Esab basic welding fillar metal technology

BASIC
WELDING FILLER METAL
TECHNOLOGY
A Correspondence Course
LESSON I
THE BASICS OF ARC WELDING
©COPYRIGHT 2000 THE ESAB GROUP, INC.
ESAB ESAB Welding &
Cutting Products
An Introduction to Metals
Electricity for Welding
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Welding Filler Metals
for Stainless Steels
Lesson 6
Carbon & Low Alloy
Steel Filler Metals -
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Reliability of Welding
Filler Metals

© COPYRIGHT 1998 THE ESAB GROUP, INC
TABLE OF CONTENTS
LESSON I
THE BASICS OF ARC WELDING
PART A. AN INTRODUCTION TO METALS
Section Nr. Section Title Page
1.1 Source and Manufacturing............................................................. 1
1.1.1 Rimmed Steel ................................................................................... 2
1.1.2 Capped Steel .................................................................................... 2
1.1.3 Killed Steel ........................................................................................ 3
1.1.4 Semi-Killed Steel............................................................................... 3
1.1.5 Vacuum Deoxidized Steel ................................................................. 3
1.2 Classification of Steels................................................................... 3
1.2.1 Carbon Steel ..................................................................................... 3
1.2.2 Low Alloy Steel.................................................................................. 3
1.2.3 High Alloy Steel ................................................................................. 4
1.3 Specifications ................................................................................. 5
1.4 Crystalline Structure of Metals ...................................................... 6
1.4.1 Grains and Grain Boundaries ........................................................... 7
1.5 Heat Treatment ................................................................................ 8
1.5.1 Preheat ............................................................................................. 8
1.5.2 Stress Relieving ................................................................................ 9
1.5.3 Hardening ......................................................................................... 9
1.5.4 Tempering ......................................................................................... 9
1.5.5 Annealing .......................................................................................... 9
1.5.6 Normalizing ....................................................................................... 10
1.5.7 Heat Treatment Trade-Off ................................................................. 10
1.6 Properties of Metals........................................................................ 10
1.6.1 Tensile Strength ................................................................................ 10
1.6.2 Yield Strength.................................................................................... 11
1.6.3 Ultimate Tensile Strength .................................................................. 11
1.6.4 Percentage of Elongation ................................................................. 11
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

TABLE OF CONTENTS
LESSON I - Con't.
1.6.5 Reduction of Area ............................................................................. 11
1.6.6 Charpy Impacts ................................................................................. 11
1.6.7 Fatigue Strength ............................................................................... 12
1.6.8 Creep Strength.................................................................................. 13
1.6.9 Oxidation Resistance ........................................................................ 13
1.6.10 Hardness Test ................................................................................... 13
1.6.11 Coefficient of Expansion ................................................................... 14
1.6.12 Thermal Conductivity ........................................................................ 14
1.7 Effects of Alloying Elements .......................................................... 14
1.7.1 Carbon .............................................................................................. 14
1.7.2 Sulphur ............................................................................................. 14
1.7.3 Manganese ....................................................................................... 15
1.7.4 Chromium ......................................................................................... 15
1.7.5 Nickel ................................................................................................ 15
1.7.6 Molybdenum ..................................................................................... 15
1.7.7 Silicon ............................................................................................... 15
1.7.8 Phosphorus....................................................................................... 15
1.7.9 Aluminum .......................................................................................... 15
1.7.10 Copper .............................................................................................. 15
1.7.11 Columbium........................................................................................ 16
1.7.12 Tungsten ........................................................................................... 16
1.7.13 Vanadium .......................................................................................... 16
1.7.14 Nitrogen ............................................................................................ 16
1.7.15 Alloying Elements summary ............................................................. 16
PART B. ELECTRICITY FOR WELDING
1.8 Electricity for Welding ....................................................................... 17
1.8.1 Principles of Electricity ...................................................................... 17
1.8.2 Ohm’s Law ........................................................................................ 18
1.8.3 Electrical Power ................................................................................ 19
1.8.4 Power Generation ............................................................................. 20
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

`
TABLE OF CONTENTS
LESSON I - Con't.
1.8.5 Transformers .................................................................................... 22
1.8.6 Power Requirements ........................................................................ 24
1.8.7 Rectifying AC to DC .......................................................................... 25
1.9 Constant Current or Constant Voltage .............................................. 26
1.9.1 Constant Current Characteristics ...................................................... 26
1.9.2 Constant Voltage Characteristics ...................................................... 26
1.9.3 Types of Welding Power Sources ..................................................... 27
1.9.4 Power Source Controls ..................................................................... 28
Appendix A Glossary of Terms ............................................................................. 29
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
AN INTRODUCTION TO METALS
1.1 SOURCE AND MANUFACTURING
Metals come from natural deposits of ore in the earth’s crust. Most ores are contaminated
with impurities that must be removed by mechanical and chemical means. Metal extracted
from the purified ore is known as primary or virgin metal, and metal that comes from scrap
is called secondary metal. Most mining of metal bearing ores is done by either open pit or
underground methods. The two methods of mining employed are known as “selective” in
which small veins or beds of high grade ore are worked, and “bulk” in which large quantities
of low grade ore are mined to extract a high grade portion.
1.1.0.1 There are two types of ores, ferrous and nonferrous. The term ferrous comes
from the Latin word “ferrum” meaning iron, and a ferrous metal is one that has a high iron
content. Nonferrous metals, such as copper and aluminum, are those that contain little or
no iron. There is approximately 20 times the tonnage of iron in the earth’s crust compared
to all other nonferrous products combined; therefore, it is the most important and widely
used metal.
1.1.0.2 Aluminum, because of its attractive appearance, light weight and strength, is the
next most widely used metal. Commercial aluminum ore, known as bauxite, is a residual
deposit formed at or near the earth’s surface.
1.1.0.3 Some of the chemical processes that occur during steel making are repeated
during the welding operation and an understanding of welding metallurgy can be gained by
imagining the welding arc as a miniature steel mill.
1.1.0.4 The largest percentage of commercially produced iron comes from the blast
furnace process. A typical blast furnace is a circular shaft approximately 90 to 100 feet in
height with an internal diameter of approximately 28 feet. The steel shell of the furnace is
lined with a refractory material, usually a hard, dense clay firebrick.
1.1.0.5 The iron blast furnace utilizes the chemical reaction between a solid fuel charge
and the resulting rising column of gas in the furnace. The three different materials used for
the charge are ore, flux and coke. The ore consists of iron oxide about four inches in
diameter. The flux is limestone that decomposes into calcium oxide and carbon dioxide.
The lime reacts with impurities in the ore and floats them to the surface in the form of a
slag. Coke, which is primarily carbon, is the ideal fuel for blast furnaces because it
produces carbon monoxide gas, the main agent for reducing iron ore into iron metal.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.1.0.6 The basic operation of the blast furnace is to reduce iron oxide to iron metal and
to remove impurities from the metal. Reduced elements pass into the iron and oxidized
elements dissolve into the slag. The metal that comes from the blast furnace is called pig
iron and is used as a starting material for further purification processes.
1.1.0.7 Pig iron contains excessive amounts of elements that must be reduced before
steel can be produced. Different types of furnaces, most notably the open hearth, electric
and basic oxygen, are used to continue this refining process. Each furnace performs the
task of removing or reducing elements such as carbon, silicon, phosphorus, sulfur and
nitrogen by saturating the molten metal with oxygen and slag forming ingredients. The
oxygen reduces elements by forming gases that are blown away and the slag attracts
impurities as it separates from the molten metal.
1.1.0.8 Depending upon the type of slag that is used, refining furnaces are classed as
either acid or basic. Large amounts of lime are contained in basic slags and high quantities
of silica are present in acid slags. This differential between acid and basic slags is also
present in welding electrodes for much of the same refining process occurs in the welding
operation.
1.1.0.9 After passing through the refining furnace, the metal is poured into cast iron ingot
molds. The ingot produced is a rather large square column of steel. At this point, the metal
is saturated with oxygen. To avoid the formation of large gas pockets in the cast metal, a
substantial portion of the oxygen must be removed. This process is known as deoxidation,
and it is accomplished through additives that tie up the oxygen either through gases or in
slag. There are various degrees of oxidation, and the common ingots resulting from each
are as follows:
1.1.1 Rimmed Steel - The making of rimmed steels involves the least deoxidation. As
the ingots solidify, a layer of nearly pure iron is formed on the walls and bottom of the mold,
and practically all the carbon, phosphorus, and sulfur segregate to the central core. The
oxygen forms carbon monoxide gas and it is trapped in the solidifying metal as blow holes
that disappear in the hot rolling process. The chief advantage of rimmed steel is the excel-
lent defect-free surface that can be produced with the aide of the pure iron skin. Most
rimmed steels are low carbon steels containing less than .1% carbon.
1.1.2 Capped Steel - Capped steel regulates the amount of oxygen in the molten
metal through the use of a heavy cap that is locked on top of the mold after the metal is
allowed to reach a slight level of rimming. Capped steels contain a more uniform core
composition than the rimmed steels. Capped steels are, therefore, used in applications
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
that require excellent surfaces, a more homogenous composition, and better mechanical
properties than rimmed steel.
1.1.3 Killed Steel - Unlike rimmed or capped steel, killed steel is made by completely
removing or tying up the oxygen before the ingot solidifies to prevent the rimming action.
This removal is accomplished by adding a ferro-silicon alloy that combines with oxygen to
form a slag, leaving a dense and homogenous metal.
1.1.4 Semi-killed Steel - Semi-killed steel is a compromise between rimmed and killed
steel. A small amount of deoxidizing agent, generally ferro-silicon or aluminum, is added.
The amount is just sufficient to kill any rimming action, leaving some dissolved oxygen.
1.1.5 Vacuum Deoxidized Steel - The object of vacuum deoxidation is to remove
oxygen from the molten steel without adding an element that forms nonmetallic inclusions.
This is done by increasing the carbon content of the steel and then subjecting the molten
metal to vacuum pouring or steam degassing. The carbon reacts with the oxygen to form
carbon monoxide, and as a result, the carbon and oxygen levels fall within specified limits.
Because no deoxidizing elements that form solid oxides are used, the steel produced by
this process is quite clean.
1.2 CLASSIFICATIONS OF STEEL
The three commonly used classifications for steel are: carbon, low alloy, and high alloy.
These are referred to as the “type” of steel.
1.2.1 Carbon Steel - Steel is basically an alloy of iron and carbon, and it attains its
strength and hardness levels primarily through the addition of carbon. Carbon steels are
classed into four groups, depending on their carbon levels.
Low Carbon Up to 0.15% carbon
Mild Carbon Steels .15% to 0.29% carbon
Medium Carbon Steels .30% to 0.59% carbon
High Carbon Steels .60% to 1.70% carbon
1.2.1.1 The largest tonnage of steel produced falls into the low and mild carbon steel
groups. They are popular because of their relative strength and ease with which they can
be welded.
1.2.2 Low Alloy Steel - Low alloy steel, as the name implies, contains small amounts
of alloying elements that produce remarkable improvements in their properties. Alloying
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
elements are added to improve strength and toughness, to decrease or increase the
response to heat treatment, and to retard rusting and corrosion. Low alloy steel is gener-
ally defined as having a 1.5% to 5% total alloy content. Common alloying elements are
manganese, silicon, chromium, nickel, molybdenum, and vanadium. Low alloy steels may
contain as many as four or five of these alloys in varying amounts.
1.2.2.1 Low alloy steels have higher tensile and yield strengths than mild steel or carbon
structural steel. Since they have high strength-to-weight ratios, they reduce dead weight in
railroad cars, truck frames, heavy equipment, etc.
1.2.2.2 Ordinary carbon steels, that exhibit brittleness at low temperatures, are unreliable
in critical applications. Therefore, low alloy steels with nickel additions are often used for
low temperature situations.
1.2.2.3 Steels lose much of their strength at high temperatures. To provide for this loss
of strength at elevated temperatures, small amounts of chromium or molybdenum are
added.
1.2.3 High Alloy Steel - This group of expensive and specialized steels contain alloy
levels in excess of 10%, giving them outstanding properties.
1.2.3.1 Austenitic manganese steel contains high carbon and manganese levels, that
give it two exceptional qualities, the ability to harden while undergoing cold work and great
toughness. The term austenitic refers to the crystalline structure of these steels.
1.2.3.2 Stainless steels are high alloy steels that have the ability to resist corrosion. This
characteristic is mainly due to the high chromium content, i.e., 10% or greater. Nickel is
also used in substantial quantities in some stainless steels.
1.2.3.3 Tool steels are used for cutting and forming operations. They are high quality
steels used in making tools, punches, forming dies, extruding dies, forgings and so forth.
Depending upon their properties and usage, they are sometimes referred to as water
hardening, shock resisting, oil hardening, air hardening, and hot work tool steel.
1.2.3.4 Because of the high levels of alloying elements, special care and practices are
required when welding high alloy steels.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.3 SPECIFICATIONS
Many steel producers have developed steels that they market under a trade name such as
Cor-Ten, HY-80, T-1, NA-XTRA, or SS-100, but usually a type of steel is referred to by its
specification. A variety of technical, governmental and industrial associations issue
specifications for the purpose of classifying materials by their chemical composition,
properties or usage. The specification agencies most closely related to the steel industry
are the American Iron and Steel Institute (AISI), Society of Automotive Engineers (SAE),
American Society for Testing and Materials (ASTM), and the American Society of
Mechanical Engineers (ASME).
1.3.0.1 The American Iron and Steel Institute (AISI) and the Society of Automobile
Engineers (SAE) have collaborated in providing identical numerical designations for their
specifications. The first two digits of a four digit index number refer to a series of steels
classified by their composition or alloy combination. While the last two digits, which can
change within the same series, give an approximate average of the carbon range. For
example, the first two digits of a type 1010 or 1020 steel indicate a “10” series that has
carbon as its main alloy. The last two digits indicate an approximate average content of
.10% or .20% carbon, respectively. Likewise, the “41” of a 4130 type steel refers to a group
that has chromium and molybdenum as their main alloy combination with approximately
.30% carbon content.
1.3.0.2 The AISI classifications for certain alloys, such as stainless steel, are somewhat
different. They follow a three digit classification with the first digit designating the main
alloy composition or series. The last two digits will change within a series, but are of an
arbitrary nature being agreed upon by industry as a designation for certain compositions
within the series. For example, the “3” in a 300 series of stainless steel indicates chromium
and nickel as the main alloys, but a 308 stainless has a different overall composition than a
347 type. The “4” of a 400 series indicates the main alloy as chromium, but there are
different types such as 410, 420, 430, and so forth within the series.
1.3.0.3 The American Society for Testing and Materials (ASTM) is the largest
organization of its kind in the world. It has compiled some 48 volumes of standards for
materials, specifications, testing methods and recommended practices for a variety of
materials ranging from textiles and plastics to concrete and metals.
1.3.0.4 Two ASTM designated steels commonly specified for construction are A36-77
and A242-79. The prefix letter indicates the class of a material. In this case, the letter “A”
indicates a ferrous metal, the class of widest interest in welding. The numbers 36 and 242
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

© COPYRIGHT 1999 THE ESAB GROUP
LESSON I, PART A
are index numbers. The 77 and 79 refer to the year that the standards for these steels
were originally adopted or the date of their latest revision.
1.3.0.5 The ASTM designation may be further subdivided into Grades or Classes. Since
many standards for ferrous metals are written to cover forms of steel (i.e., sheet, bar, plate,
etc.) or particular products fabricated from steel (i.e., steel rail, pipe, chain, etc.), the user
may select from a number of different types of steel under the same classification. The
different types are than placed under grades or classes as a way of indicating the
differences in such things as chemistries, properties, heat treatment, etc. An example of a
full designation is A285-78 Grade A or A485-79 Class 70.
1.3.0.6 The American Society of Mechanical Engineers (ASME) maintains a widely used
ASME Boiler and Pressure Vessel Code. The material specification as adopted by the
ASME is identified with a prefix letter “S”, while the remainder is identical with ASTM with
the exception that the date of adoption or revision by ASTM is not shown. Therefore, a
common example of an ASME classification is SA 387 Grade 11, Class 1.
1.4 CRYSTALLINE STRUCTURE OF METALS
When a liquid metal is cooled, its atoms will assemble into a regular crystal pattern and we
say the liquid has solidified or crystallized. All metals solidify as a crystalline material. In a
crystal the atoms or molecules are held in a fixed position and are not free to move about
as are the molecules of a liquid or gas. This fixed position is called a crystal lattice. As the
temperature of a crystal is raised, more thermal energy is absorbed by the atoms or
molecules and their movement increases. As the distance
between the atoms increases, the lattice breaks down and
the crystal melts. If a lattice contains only one type of atom,
as in pure iron, the conditions are the same at all points
throughout the lattice, and the crystal melts at a single
temperature (see Figure 1).
FIGURE 1
4000
3000
2000
1000
TIME
SOLID-LIQUID TRANSFORMATION, PURE IRON
LIQUID
2795°F
SOLID
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.4.0.1 However, if the lattice contains two
or more types of atoms, as in any alloy-steel,
it may start to melt at one temperature but not
be completely molten until it has been heated
to a higher temperature (See Figure 2). This
creates a situation where there is a
combination of liquids and solids within a
range of temperatures.
1.4.0.2 Each metal has a characteristic
crystal structure that forms during
solidification and often remains the permanent
form of the material as long as it remains at
room temperature. However, some metals
may undergo an alteration in the crystalline
form as the temperature is changed. This is known as phase transformation. For example,
pure iron solidifies at 2795°F, the delta structure transforms into a structure referred to as
gamma iron. Gamma iron is commonly known as austenite and is a nonmagnetic
structure. At a temperature of 1670°F., the pure iron structure transforms back to the delta
iron form, but at this temperature, the metal is known as alpha iron. These two phases are
given different names to differentiate between the high temperature phase (delta) and the
low temperature phase (alpha). The capability of the atoms of a material to transform into
two or more crystalline structures at different temperatures is defined as allotropic. Steels
and iron are allotropic metals.
1.4.1 Grains and Grain Boundaries - As the metal is cooled to its freezing point, a
small group of atoms begin to assemble into crystalline form (refer to Figure 3). These
small crystals scattered throughout the body of the liquid are oriented in all directions and
as solidification continues, more crystals are formed from the surrounding liquid. Often,
they take the form of dendrites, or a treelike structure. As crystallization continues, the
crystals begin to touch one another, their free growth hampered, and the remaining liquid
freezes to the adjacent crystals until solidification is complete. The solid is now composed
of individual crystals that usually meet at different orientations. Where these crystals meet
is called a grain boundary.
1.4.1.2 A number of conditions influence the initial grain size. It is important to know that
cooling rate and temperature has an important influence on the newly solidified grain
structure and grain size. To illustrate differences in grain formation, let's look at the cooling
phases in a weld.
FIGURE 2
TIME
Lesson 1
The Basics of Arc
Welding
Liquid
Lesson 2
Common Electric
Arc Welding
Processes
Liquid and Solid
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Solid
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Solid-Liquid Transformation, Alloy Metal
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.4.1.3 Initial crystal formation begins at the coolest spot in the weld. That spot is at the
point where the molten metal and the unmelted base metal meet. As the metal continues
to solidify, you will note that the grains in the center are smaller and finer in texture than the
grains at the outer boundaries of the weld deposit. This is explained by the fact that as the
weld metal cools, the heat from the center of the weld deposit will dissipate into the base
metal through the outer grains that solidified first. Consequently, the grains that solidified
first were at high temperatures for a longer time while in the solid state and this is a
situation that encourages grain growth. Grain size can have an effect on the soundness of
the weld. The smaller grains are stronger and more ductile than the larger grains. If a
crack occurs, the tendency is for it to start in the area where the grains are largest.
1.4.1.4 To summarize this section, it should be understood that all metals are composed
of crystals of grains. The shape and characteristics of crystals are determined by the
arrangement of their atoms. The atomic pattern of a single element can change its
arrangement at different temperatures, and that this atomic pattern or microstructure
determines the properties of the metals.
1.5 HEAT TREATMENT
The temperature that metal is heated, the length of time it is held at that temperature, and
the rate that it is cooled, all have an effect on a metal's crystalline structure. This crystalline
structure, commonly referred to as "microstructure," determines the specific properties of
metals. There are various ways of manipulating the microstructure, either at the steel mill
or in the welding procedure. Some of the more common ways are as follows:
1.5.1 Preheat - Most metals are rather good conductors of heat. As a result, the heat
in the weld area is rapidly dispersed through the whole weldment to all surfaces where it is
radiated to the atmosphere causing comparatively rapid cooling. In some metals, this rapid
cooling may contribute to the formation of microstructures in the weld zone that are detri-
mental. Preheating the weldment before it is welded is a method of slowing the cooling
FIGURE 3
GRAIN
BOUNDARIES
DENDRITE INITIAL COMPLETE
FORMATION CRYSTAL FORMATION SOLIDIFICATION
BASE
METAL
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
rate of the metal. The preheat temperature may vary from 150°F to 1000°F, but more
commonly it is held in the 300°F to 400°F range. The thicker the weld metal, the more
likely will it be necessary to preheat, because the heat will be conducted away from the
weld zone more rapidly as the mass increases.
1.5.2 Stress Relieving - Metals expand when heated and contract when cooled. The
amount of expansion is directly proportional to the amount of heat applied. In a weldment,
the metal closest to the weld is subjected to the highest temperature, and as the distance
from the weld zone increases, the maximum temperature reached decreases. This nonuni-
form heating causes nonuniform expansion and contraction and can cause distortion and
internal stresses within the weldment. Depending on its composition and usage, the metal
may not be able to resist these stresses and cracking or early failure of the part may occur.
One way to minimize these stresses or to relieve them is by uniformly heating the structure
after it has been welded. The metal is heated to temperatures just below the point where a
microstructure change would occur and then it is cooled at a slow rate.
1.5.3 Hardening - The hardness of steel may be increased by heating it to 50°F to
100°F above the temperature that a microstructure change occurs, and then placing the
metal in a liquid solution that rapidly cools it. This rapid cooling, known as "quenching,"
locks in place microstructures known as "martensite" that contribute to a metal's hardness
characteristic. The quenching solutions used in this process are rated according to the
speed that they cool the metal, i.e., Oil (fast), Water (faster), Salt Brine (fastest).
1.5.4 Tempering - After a metal is quenches, it is then usually tempered. Tempering is
a process where the metal is reheated to somewhere below 1335°F, held at that tempera-
ture for a length of time, and then cooled to room temperature. Tempering reduces the
brittleness that is characteristic in hardened steels, thereby producing a good balance
between high strength and toughness. The term toughness, as it applies to metals, usually
refers to resistance to brittle fracture or notch toughness under certain environmental
conditions. More information on these properties will be covered later in this lesson and in
subsequent lessons. Steels that respond to this type of treatment are known as "quenched
and tempered steels."
1.5.5 Annealing - A metal that is annealed is heated to a temperature 50° to 100°
above where a microstructure change occurs, held at that temperature for a sufficient time
for a uniform change to take place, and then cooled at a very slow rate, usually in a fur-
nace. The principal reason for annealing is to soften steel and create a uniform fine grain
structure. Welded parts are seldom annealed for the high temperatures would cause
distortion.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.5.6 Normalizing - The main difference between normalizing and annealing is the
method of cooling. Normalized steel is heated to a temperature approximately 100° above
where the microstructure transforms and then cooled in still air rather than in a furnace.
1.5.7 Heat Treatment Trade-Off - It must be noted that these various ways of control-
ling the heating and cooling of metals can produce a desired property, but sometimes at the
expense of another desirable property. An example of this trade-off is evident in the fact
that certain heat treatments can increase the strength or hardness of metal, but the same
treatments will also make the metal less ductile or more brittle, and therefore, susceptible
to welding problems.
1.6 PROPERTIES OF METALS
The usefulness of a particular metal is determined by the climate and conditions in which it
will be used. A metal that is stamped into an automobile fender must be softer and more
pliable than armor plate that must withstand an explosive force, or the material used for an
oil rig on the Alaska North Slope must perform in a quite different climate than a steam
boiler. It becomes obvious that before a material is recommended for a specific use, the
physical and mechanical properties of that metal and the weld metal designed to join it
must be evaluated. Some of the more important properties of metals and the means of
evaluation are as follows:
1.6.1 Tensile Strength - Tensile strength is one of the most important determining
factors in selecting a metal, especially if it is to be a structural member, part of a machine,
or part of a pressure vessel.
1.6.1.1 The tensile test is performed as shown in Figure 4. The test specimen is
machined to exact standard dimensions and clamped into the testing apparatus at both
ends. The specimen is then
pulled to the point of fracture
and the data recorded.
1.6.1.2 The tensile strength
test gives us 4 primary pieces
of information: (1) Yield
Strength, (2) Ultimate Tensile
Strength, (3) Elongation, and (4)
Reduction in Area.
FIGURE 4
RECORDING
DIAL
TEST
SPECIMEN
FORCE
TENSILE TESTING APPARATUS
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.6.2 Yield Strength - When a metal is placed in tension, it acts somewhat like a
rubberband. When a load of limited magnitude is applied, the metal stretches, and when
the load is released, the metal returns to its original shape. This is the elastic characteristic
of metal and is represented by letter A in Figure 5. As a greater load is applied, the metal
will reach a point where it will no longer return to its original shape but will continue to
stretch. Yield strength is the point where the metal reaches the limit of its elastic character-
istic and will no longer return to its original shape.
1.6.3 Ultimate Tensile Strength - Once a metal has exceeded its yield point, it will
continue to stretch or deform, and if the load is suddenly released, the metal will not return
to its original shape, but will remain in its elongated form. This is called the plastic region of
the metal and is represented by the letter B in Figure 5. As this plastic deformation in-
creases, the metal strains
against further elongation, and
an increased load must be
applied to stretch the metal. As
the load is increased, the metal
will finally reach a point where it
no longer resists and any fur-
ther load applied will rapidly
cause the metal to break. That
point at which the metal has
withstood or resisted the maximum applied load is its ultimate tensile strength. This infor-
mation is usually recorded in pounds per square inch (psi).
1.6.4 Percentage of Elongation - Before a tensile specimen is placed in the tensile
tester, two marks at a measured distance are placed on the opposing ends of the circular
shaft. After the specimen is fractured, the distance between the marks is measured and
recorded as a percentage of the original distance. See Figure 5. This is the percentage of
elongation and it gives an indication of the ductility of the metal at room temperature.
1.6.5 Reduction of Area - A tensile specimen is machined to exact dimensions. The
area of its midpoint cross-section is a known figure. As the specimen is loaded to the point
of fracture, the area where it breaks is reduced in size. See Figure 5. This reduced area is
calculated and recorded as a percentage of the original cross-sectional area. This informa-
tion reflects the relative ductility or brittleness of the metal.
1.6.6 Charpy Impacts - Metal that is normally strong and ductile at room temperature
may become very brittle at much lower temperatures, and thus, is susceptible to fracture if
FIGURE 5
STRAIN - INCHESA B C
NOMINAL STRESS - STRAIN CURVE
Lesson 1
The Basics of Arc
Welding
Elong-
ation
Lesson 2
Common Electric
Arc Welding
Processes
Reduction
of Area
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Fracture
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Yield Strength
Lesson 5
Ultimate Strength
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
a sharp abrupt load is applied to it. An impact tester measures the degree of susceptibility
to what is called brittle fracture.
1.6.6.1 The impact specimen is machined to exact dimensions (Figure 6) and then
notched on one side. Quite often, the notch is in the form of a "V" and the test in this case
is referred to as a Charpy V-Notch Impact Test. The specimen is cooled to a
predetermined temperature and then placed in a stationary clamp at the base of the testing
machine. The specimen is in the direct path of a weighted hammer attached to a
pendulum (Figure 6).
1.6.6.2 The hammer is released from a fixed height and the energy required to fracture
the specimen is recorded in ft-lbs. A specimen that is cooled to -60°F and absorbs 40 ft-lbs
of energy is more ductile, and therefore, more suitable for low temperature service than a
specimen that withstands only 10 ft-lbs at the same temperature. The specimen that
withstood 40 ft-lbs energy is said to have better toughness or notch toughness.
1.6.7 Fatigue Strength - A metal will withstand a load less than its ultimate tensile
strength but may break if that load is removed and then reapplied several times. For ex-
ample, if a thin wire is bent once, but if it is bent back and forth repeatedly, it will eventually
fracture and it is said to have exceeded its fatigue strength. A common test for this
strength is to place a specimen in a machine that repeatedly applies the same load first in
tension and then in compression. The fatigue strength is calculated from the number of
cycles the metal withstands before the point of failure is reached.
FIGURE 6
FRACTURES CRACKS DEFORMS
CHARPY V-NOTCH
SPECIMEN
ENERGY
IN FT/LBS
CHARPY IMPACT TEST MACHINE
CHARPY V-NOTCH IMPACT TEST
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.6.8 Creep Strength - If a load below a metal's tensile strength is applied at room
temperature (72°F), it will cause some initial elongation, but there will be no further measur-
able elongation if the load is kept at a constant level. If that same load were applied to a
metal heated to a high temperature, the situation would change. Although the load is held
at a constant level, the metal will gradually continue to elongate. This characteristic is
called creep. Eventually, the material may rupture depending on the temperature of the
metal, the degree of load applied and the length of time that it is applied. All three of these
factors determine a metal's ability to resist creep, and therefore, its creep strength.
1.6.9 Oxidation Resistance - The atoms of metal have a tendency to unite with oxy-
gen in the air to form oxide compounds, the most visible being rust and scale. In some
metals, these oxides will adhere very tightly to the skin of the metal and effectively seal it
from further oxidation as is evident in stainless steel. These materials have high oxidation
resistance. In other metals, the bond is very loose, creating a situation where the oxides
will flake off, and the metal gradually deteriorates as the time of exposure is extended.
1.6.10 Hardness Test - The resistance of a metal to indentation is a measure of its
hardness and an indication of the materials's strength. To test for hardness, a fixed load
forces an indenter into the test material (Figure 7). The depth of the penetration or the size
of the impression is measured. The measurement is converted into a hardness number
through the use of a variety of established tables. The most common tables are the Brinell,
Vickers, Knoop and Rockwell. The Rockwell is further divided into different scales, and
FIGURE 7
HARDNESS TEST SHAPE OF INDENTER INDENTER DESCRIPTION
ROCKWELL
A Diamond
C Cone
D
B 1/16 in. Diameter
F Steel Sphere
G
1/8 in. Diameter
E Steel Sphere
10 mm Sphere of Steel
BRINNELL or Tungsten Carbide
VICKERS Diamond Pyramid
KNOOP Diamond Pyramid
}
}
Types of Indenters - Hardness Tests
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
depending on the material being tested, the shape of the indenter and the load applied, the
conversion tables may differ. For example, a material listed as having a hardness of Rb or
Rc means its hardness has been determined from the Rockwell "B" scale or the Rockwell
"C" scale.
1.6.11 Coefficient of Expansion - All metals expand when heated and contract when
cooled. This dimensional change is related to the crystalline structure and will vary with
different materials. The different expansion and contraction rates are expressed numeri-
cally by a coefficient of thermal expansion. When two different metals are heated to the
same temperature and cooled at the same rate, the one with the higher numerical coeffi-
cient will expand and contract more than the one with the lesser coefficient.
1.6.12 Thermal Conductivity - Some metals will absorb and transmit heat more readily
than others. They are categorized as having high thermal conductivity. This characteristic
contributes to the fact that some metals will melt or undergo transformations at much lower
temperatures than others.
1.7 EFFECTS OF THE ALLOYING ELEMENTS
Alloying is the process of adding a metal or a nonmetal to pure metals such as copper,
aluminum or iron. From the time it was discovered that the properties of pure metals could
be improved by adding other elements, alloy steel has increased by popularity. In fact,
metals that are welded are rarely in their pure state. The major properties that can be
improved by adding small amounts of alloying elements are hardness, tensile strength,
ductility and corrosion resistance. Common alloying elements and their effect on the
properties of metals are as follows:
1.7.1 Carbon - Carbon is the most effective, most widely used and lowest in cost
alloying element available for increasing the hardness and strength of metal. An alloy
containing up to 1.7% carbon in combination with iron is known as steel, whereas the
combination above 1.7% carbon is known as cast iron. Although carbon is a desirable
alloying element, high levels of it can cause problems; therefore, special care is required
when welding high carbon steels and cast iron.
1.7.2 Sulphur - Sulphur is normally an undesirable element in steel because it causes
brittleness. It may be deliberately added to improve the machinability of the steel. The
sulphur causes the
machine chips to break rather than form long curls and clog the machine. Normally, every
effort is made to reduce the sulphur content to the lowest possible level because it can
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
create welding difficulties.
1.7.3 Manganese - Manganese in contents up to 1% is usually present in all low alloy
steels as a deoxidizer and desulphurizer. That is to say, it readily combines with oxygen
and sulphur to help negate the undesirable effect these elements have when in their natu-
ral state. Manganese also increases the tensile strength and hardenability of steel.
1.7.4 Chromium - Chromium, in combination with carbon, is a powerful hardening
alloying element. In addition to its hardening properties, chromium increases corrosion
resistance and the strength of steel at high temperatures. Chromium is the primary alloying
element in stainless steel.
1.7.5 Nickel - The greatest single property of steel that is improved by the presence of
nickel is its ductility or notch toughness. In this respect, it is the most effective of all alloy-
ing elements in improving a steel's resistance to impact at low temperatures. Electrodes
with high nickel content are used to weld cast iron materials. Nickel is also used in combi-
nation with chromium to form a group known as austenitic stainless steel.
1.7.6 Molybdenum - Molybdenum strongly increases the depth of the hardening
characteristic of steel. It is quite often used in combination with chromium to improve the
strength of the steel at high temperatures. This group of steels is usually referred to as
chrome-moly steels.
1.7.7 Silicon - Silicon is usually contained in steel as a deoxidizer. Silicon will add
strength to steel but excessive amounts can reduce the ductility. Additional amounts of
silicon are sometimes added to welding electrodes to increase the fluid flow of weld metal.
1.7.8 Phosphorus - Phosphorus is considered a harmful residual element in steel
because it greatly reduces ductility and toughness. Efforts are made to reduce it to its very
lowest levels; however, phosphorus is added in very small amounts to some steels to
increase strength.
1.7.9 Aluminum - Aluminum is primarily used as a deoxidizer in steel. It may also be
used in very small amounts to control the size of the grains.
1.7.10 Copper - Copper contributes greatly to the corrosion resistance of carbon steel
by retarding the rate of rusting at room temperature, but high levels of copper can cause
welding difficulties.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART A
1.7.11 Columbium - Columbium is used in austenitic stainless steel to act as a stabi-
lizer. Since the carbon in the stainless steel decreases the corrosion resistance, a means
of making carbon ineffective must be found. Columbium has a greater affinity for carbon
than chromium, leaving the chromium free for corrosion protection.
1.7.12 Tungsten - Tungsten is used in steel to given strength at high temperatures.
Tungsten also joins with carbon to form carbides that are exceptionally hard, and therefore
have exceptional resistance to wear.
1.7.13 Vanadium - Vanadium helps keep steel in the desirable fine grain condition after
heat treatment. It also helps increase the depth of hardening and resists softening of the
steel during tempering treatments.
1.7.14 Nitrogen - Usually, efforts are made to eliminate hydrogen, oxygen and nitrogen
from steel because their presence can cause brittleness. Nitrogen has the ability to form
austenitic structures; therefore, it is sometimes added to austenitic stainless steel to reduce
the amount of nickel needed, and therefore, the production costs of that steel.
1.7.15 Alloying Elements Summary - It should be understood that the addition of
elements to a pure metal may influence the crystalline form of the resultant alloy. If a pure
metal has allotropic characteristics (the ability of a metal to change its crystal structure) at a
specific temperature, then that characteristic will occur over a range of temperatures with
the alloyed metal. The range in which the change takes place may be wide or narrow,
depending on the alloys and the quantities in which they are added. The alloying element
may also effect the crystalline changes by either suppressing the appearance of certain
crystalline forms or even by creating entirely new forms. All these transformations induced
by alloying elements are dependent on heat input and cooling rates. These factors are
closely controlled at the steel mill, but since the welding operation involves a nonuniform
heating and cooling of metal, special care is often needed in the welding of low and high
alloy steel.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8 ELECTRICITY FOR WELDING
1.8.1 Principles of Electricity - Arc welding is a method of joining metals accom-
plished by applying sufficient electrical pressure to an electrode to maintain a current path
(arc) between the electrode and the work piece. In this process, electrical energy is
changed into heat energy, bringing the metals to a molten state; whereby they are joined.
The electrode (conductor) is either melted and added to the base metal or remains in its
solid state. All arc welding utilizes the transfer of electrical energy to heat energy, and to
understand this principle, a basic knowledge of electricity and welding power sources is
necessary.
1.8.1.1 The three basis principles of static electricity are as follows:
1. There are two kinds of electrical charges in existence - negative and positive.
2. Unlike charges attract and like charges repel.
3. Charges can be transferred from one place to another.
1.8.1.2 Science has established that all matter is made up of atoms and each atom
contains fundamental particles. One of these particles is the electron, which has the ability
to move from one place to another. The electron is classified as a negative electrical
charge. Another particle, about 1800 times as heavy as the electron, is the proton and
under normal conditions the proton will remain stationary.
1.8.1.3 Material is said to be in an electrically uncharged state when its atoms contain an
equal number of positive charges (protons) and negative charges (electrons). This balance
is upset when pressure forces the electrons to move from atom to atom. This pressure,
sometimes referred to as electromotive force, is commonly known as voltage. It should be
noted that voltage that does not move through a conductor, but without voltage, there would
be no current flow. For our purposes, it is easiest to think of voltage as the electrical
pressure that forces the electrons to move.
1.8.1.4 Since we know that like charges repel and unlike charges attract, the tendency is
for the electrons to move from a position of over-supply (negative charge) to an atom that
lacks electrons (positive charge). This tendency becomes reality when a suitable path is
provided for the movement of the electrons. The transfer of electrons from a negative to a
positive charge throughout the length of a conductor constitutes an electrical current. The
rate that current flows through a conductor is measured in amperes and the word ampere
is often used synonymously with the term current. To give an idea of the quantities of
electrons that flow through a circuit, it has been theoretically established that one ampere
equals 6.3 quintillion (6,300,000,000,000,000,000) electrons flowing past a fixed point in a
conductor every second.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8.1.5 Different materials vary in their ability to transfer electrons. Substances, such as
wood and rubber, have what is called a tight electron bond and their atoms greatly resist
the free movement of electrons. Such materials are considered poor electrical conductors.
Metals, on the other hand, have large amounts of electrons that transfer freely. Their
comparatively low electrical resistance classifies them as good electrical conductors.
1.8.1.6 Electrical resistance is primarily due to the reluctance of atoms to give up their
electron particles. It may also be thought of as the resistance to current flow.
1.8.1.7 To better understand the electrical terms discussed above, we might compare
the closed water system with the electrical diagram shown in Figure 8. You can see that as
the pump is running, the water will move in the direction of the arrows. It moves because
pressure has been produced and that pressure can be likened to voltage in an electrical
circuit. The pump can be compared to a battery or a DC generator. The water flows
through the system at a certain rate. This flow rate in an electrical circuit is a unit of
measure known as the ampere. The small pipe in the fluid circuit restricts the flow rate and
can be likened to a resistor. This unit resistance is known as the ohm. If we close the
valve in the fluid circuit, we stop the flow, and this can be compared to opening a switch in
an electrical circuit.
1.8.2 Ohm's Law - Resistance is basic to electrical theory and to understand this
principle, we must know the Ohm's Law, which is stated as follows: In any electrical circuit,
the current flow in amperes is directly proportional to the circuit voltage applied and in-
versely proportional to the circuit resistance. Directly proportional means that even though
the voltage and amperage may change, the ratio of their relationship will not. For example,
if we have a circuit of one volt and three amps, we say the ratio is one to three. Now if we
increase the volts to three, our amperage will increase proportionately to nine amps. As
can be seen, even though the voltage and amperage changed in numerical value, their
ratio did not. The term "inversely proportional" simply means that if the resistance is
FIGURE 8
VALVE
SWITCH
RESISTOR
10 OHM
BATTERY
12 VOLT
ELECTRICAL DIAGRAM
SMALL PIPE
PUMP
CLOSED WATER SYSTEM
LARGE
PIPE
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
doubled, the current will be reduced to one-half. Ohm's Law can be stated mathematically
with this equation:
I = E ÷ R or E = I × R or R = E ÷ I
(E = Volts, I = Amperes, R = Resistance (Ohms))
1.8.2.1 The equation is easy to use as seen in the following problems:
1) A 12 volt battery has a built-in resistance of 10 ohms. What is the amperage?
12 ÷ 10 = 1.2 amps
2) What voltage is required to pass 15 amps through a resistor of 5 ohms?
15 × 5 = 75 volts
3) When the voltage is 80 and the circuit is limited to 250 amps, what is the value
of the resistor?
80 ÷ 250 = .32 ohms
1.8.2.2 The theory of electrical resistance is of great importance in the arc welding
process for it is this resistance in the air space between the electrode and the base metal
that contributes to the transfer of electrical energy to heat energy. As voltage forces the
electrons to move faster, the energy they generate is partially used to overcome the
resistance created by the arc gap. This energy becomes evident as heat. In the welding
process, the temperature increases to the point where it brings metals to a molten state.
1.8.3 Electrical Power - The word "watt" is another term frequently encountered in
electrical terminology. When we pay our electrical bills, we are actually paying for the
power to run our electrical appliances, and the watt is a unit of power. It is defined as the
amount of power required to maintain a current of one ampere at a pressure of one volt.
The circuit voltage that comes into your home is a constant factor, but the amperage drawn
from the utility company depends on the number of watts required to run the electrical
appliance. The watt is figured as a product of volts times amperes and is stated math-
ematically with the following equation:
W =E × I E = W ÷ I I = W ÷ E
(W = Watts, E = Volts, I = Amperes)
1.8.3.1 The amperage used by an electrical device can be calculated by dividing the
watts rating of the device by the primary voltage for which it is designed.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8.3.2 For example, if an appliance is designed for the common household primary
voltage of 115 and the wattage stamped on the appliance faceplate is 5, then the
amperage drawn by the appliance when in operation is determined as shown:
5 ÷ 115 = .04 amperes
1.8.3.3 Kilowatt is another term common in electrical usage. The preface "kilo" is a
metric designation that means 1,000 units of something; therefore, one kilowatt is 1,000
watts of power.
1.8.4 Power Generation - Electrical energy is supplied either as direct current (DC) or
alternating current (AC). With direct current, the electron movement within the conductor is
in one direction only. With alternating current, the electron flow reverses periodically. Al-
though some types of electrical generators will produce current directly (such as batteries,
dry cells, or DC generators), most direct current is developed from alternating current.
1.8.4.1 Through experimentation, it was discovered that when a wire is moved through a
magnetic field, an electrical current is induced into the wire, and the current is at its
maximum when the motion of the conductor is at right
angles to the magnetic lines of force. The sketch
in Figure 9 will help to illustrate this principle.
1.8.4.2 If the conductor is moved upwards in
the magnetic field between the N and S poles,
the galvanometer needle will deflect plus (+).
Likewise, if the conductor is moved downwards
the needle will deflect minus (-). With this
principle of converting mechanical energy into
electrical energy understood, we can apply it to
the workings of an AC generator.
1.8.4.3 Figure 10 is a simplified sketch of an AC
generator. Starting at 0° rotation, the coil wire is moving
parallel to the magnetic lines of force and cutting none of them. Therefore, no current is
being induced into the winding.
1.8.4.4 From 0° to 90° rotation, the coil wire cuts an increasing number of magnetic lines
of force and reaches the maximum number at 90° rotation. The current increases to the
maximum because the wire is now at right angles to the lines of force.
FIGURE 9
GALVANOMETER
ELECTRO-MAGNETIC
INDUCTION
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8.4.5 From 90° to 180° rotation, the coil wire cuts a diminishing number of lines of
force and at 180° again reaches zero.
1.8.4.6 From 180° to 270°, the current begins to rise again but in the opposite direction
because now the wire is in closer proximity to the opposite pole.
1.8.4.7 One cycle is completed as the coil wire moves from 270° to 0° and the current
again drops to zero.
1.8.4.8 With the aid of a graph, we can visualize the rate at which the lines of force are
cut throughout the cycle. If we plot the current versus degree of rotation, we get the
familiar sine wave as seen in Figure 11.
1.8.4.9 With this sine wave, we can
see that one complete cycle of
alternating current comprises one
positive and one negative wave
(negative and positive meaning
electron flow in opposing directions).
The frequency of alternating current is
the number of such complete cycles
per second. For most power
applications, 60 cycles per second (60
Hertz) is the standard frequency in
North America.
FIGURE 10
CONTACTS
N N
N N
S S
S
ROTATING COIL
OR ARMATURE
PERMANENT MAGNETS
OR FIELD COILS
S
N
S
270°180°
0° 90°
BASIC AC POWER GENERATION
FIGURE 11
MAXIMUM (+)
MAXIMUM (–)
0° 90° 180° 270° 360°
START 1/4 TURN 1/2 TURN 3/4 TURN FULL TURN
(+)
(–)
0
00
ONE CYCLE - ALTERNATING CURRENT
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8.4.10 Some welders use a three-phase AC supply. Three-phase is simply three
sources of AC power as identical voltages brought in by three wires, the three voltages or
phases being separated by 120 electrical degrees. If
the sine wave for the three phases are plotted on one
line, they will appear as shown in Figure 12.
1.8.4.11 This illustrates that three-phase power is
smoother than single-phase because the overlapping
three phases prevent the current and voltage from
falling to zero 120 times a second, thereby producing a
smoother welding arc.
1.8.4.12 Since all shops do not have three-phase power, welding machines for both
single-phase and three-phase power are available.
1.8.5 Transformers - The function of a transformer is to increase or decrease voltage
to a safe value as the conditions demand. Common household voltage is usually 115 or
230 volts, whereas industrial power requirements may be 208, 230, 380, or 460 volts.
Transmitting such relatively low voltages over long distances would require a conductor of
enormous and impractical size. Therefore, power transmitted from a power plant must be
stepped up for long distance transmission and then stepped down for final use
1.8.5.1 As can be seen in Figure 13, the voltage is generated at the power plant at
13,800 volts. It is increased, transmitted over long distances, and then reduced in steps for
the end user. If power supplied to a transformer circuit is held steady, then secondary
current (amperes) decreases as the primary voltage increases, and conversely, secondary
current increases as primary voltage decreases. Since the current flow (amperes)
determines the wire or conductor size, the high voltage line may be of a relatively small
diameter.
FIGURE 12
120°
1 CYCLE
THREE PHASE AC
240°
0°
FIGURE 13
POWER TRANSMISSION
13,800 V
POWER
PLANT STEP
UP
287,000
V
HIGH VOLTAGE
300 MILES
STEP
DOWN
132,000 V
34,000 V
4,600
V
208V
230V
460V
FINAL
USE
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8.5.2 The transformer in a welding machine performs much the same as a large power
plant transformer. The primary voltage coming into the machine is too high for safe
welding. Therefore, it is stepped down to a useable voltage. This is best illustrated with an
explanation of how a single transformer works.
1.8.5.3 In the preceding paragraphs, we have found than an electrical current can be
induced into a conductor when that conductor is moved through a magnetic field to
produce alternating current. If this alternating current is passed through a conductor, a
pulsating magnetic field will surround the exterior of that conductor, that is the magnetic
field will build in intensity through the first 90 electrical degrees, or the first cycle. From that
point, the magnetic field will decay during the next quarter cycle until the voltage or current
reaches zero at 180 electrical degrees. Immediately, the current direction reverses and the
magnetic field will begin to build again until it reaches a maximum at 270 electrical degrees
in the cycle. From that point the current and the magnetic field again begin to decay until
they reach zero at 360 electrical degrees, where the cycle begins again.
1.8.5.4 If that conductor is wound around a material with high magnetic permeability
(magnetic permeability is the ability to accept large amounts of magnetic lines of force)
such as steel, the magnetic field permeates that core. See
Figure 14. This conductor is called the primary coil, and if
voltage is applied to one of its terminals and the circuit is
completed, current will flow. When a second coil is wound
around that same steel core, the energy that is stored in
this fluctuating magnetic field in the core is induced into
this secondary coil.
1.8.5.5 It is the build-up and collapse of this magnetic
field that excite the electrons in the secondary coil of the
transformer. This causes an electrical current of the same frequency as the primary coil to
flow when the secondary circuit is completed by striking the welding arc. Remember that
all transformers operate only on alternating current.
1.8.5.6 A simplified version of a welding transformer is schematically shown in Figure 15.
This welder would operate on 230 volts input power and the primary winding has 230 turns
of wire on the core. We need 80 volts for initiating the arc in the secondary or welding
circuit, thus we have 80 turns of wire in the secondary winding of the core. Before the arc
is struck, the voltage between the electrode and the work piece is 80 volts. Remember that
no current (amperage) flows until the welding circuit is completed by striking the arc.
FIGURE 14
STEEL CORE
PRIMARY
COIL
SECONDARY
COIL
80 V
80
TURNS
460 V
460
TURNS
BASIC TRANSFORMER
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8.5.7 Since the 80 volts
necessary for initiating the arc
is too high for practical
welding, some means must be
used to lower this voltage to a
suitable level. Theoretically, a
variable resistor of the proper
value could be used as an
output control since voltage is
inversely proportional to
resistance as we saw when studying Ohm's Law. Ohm's Law also stated that the
amperage is directly proportional to the voltage. This being so, you can see that adjusting
the output control will also adjust the amperage or welding current.
1.8.5.8 After the arc is initiated and current begins to flow through the secondary or
welding circuit, the voltage in that circuit will be 32 volts because it is then being controlled
by the output control.
1.8.6 Power Requirements - We can make another calculation by looking back at
Figure 15, and that is power consumption. Earlier, we explained that the watt was the unit
of electrical power and can be calculated by the formula:
Watts = Volts × Amperes
1.8.6.1 From Figure 15, we can see that the instantaneous power in the secondary
circuit is:
Watts = 32 × 300
Watts = 9600 Watts
1.8.6.2 The primary side of our transformer must be capable of supplying 9600 watts
also (disregarding losses due to heating, power factor, etc.), so by rearranging the formula,
we can calculate the required supply line current or amperage:
Amperage = Watts ÷ Volts
A = 9600 ÷ 230 = 41.74 Amps
1.8.6.3 This information establishes the approximate power requirements for the welder,
and helps to determine the input cable and fuse size necessary.
FIGURE 15
9600 WATTS 9600 WATTS
230 TURNS 80 TURNS
80
OCV
OUTPUT
CONTROL
230
VOLTS PRIMARY SECONDARY
41.74
AMPS
SIMPLIFIED WELDING TRANSFORMER
32 VOLTS
300 AMPS
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.8.7 Rectifying AC to DC - Although much welding is accomplished with AC welding
power sources, the majority of industrial welding is done with machines that produce a
direct current arc. The commercially produced AC
power that operates the welding machine
must then be changed (rectified) to direct
current for the DC arc. This is accom-
plished with a device called a rectifier.
Two types of rectifiers have been used
extensively in welding machines, the
old selenium rectifiers and the more
modern silicon rectifiers, often referred
to as diodes. See Figure 16.
1.8.7.1 The function of a rectifier in the
circuit can best be shown by the use of the
AC sine wave. With one diode in the circuit,
half-wave rectification takes place as shown
in Figure 17.
1.8.7.2 The negative half-wave is simply cut off and a pulsating DC is produced. During
the positive half-cycle, current is allowed to flow through the rectifier. During the negative
half-cycle, the current is blocked. This produces a DC composed of 60 positive pulses per
second.
1.8.7.3 By using four rectifiers connected in a
certain manner, a bridge rectifier is created, producing
full wave rectification. The bridge rectifier results in
120 positive half-cycles per second, producing a
considerably smoother direct current than half-wave
rectification. See Figure 18.
1.8.7.4 Three-phase AC can be rectified to
produce an even smoother DC than single-phase
AC. Since three-phase AC power produces three
times as many half-cycles per second as single-
phase power, a relatively smooth DC voltage
results as shown in Figure 19.
SINGLE PHASE HALF WAVE RECTIFICATION
FIGURE 17
FIGURE 16
SILICON RECTIFIER
SELENIUM RECTIFIER
SINGLE PHASE FULL WAVE RECTIFICATION
FIGURE 18
1 CYCLE
3 PHASE FULL WAVE RECTIFICATION
FIGURE 19
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.9 CONSTANT CURRENT OR CONSTANT VOLTAGE
Welding power sources are designed in many sizes and shapes. They may supply either
AC or DC, or both, and they may have various means of controlling their voltage and
amperage output. The reasons for this is that the power source must be capable of
producing the proper arc characteristics for the welding process being used. A power
source that produces a satisfactory arc when welding with coated electrodes will be less
than satisfactory for welding with solid and flux cored wires.
1.9.1 Constant Current Characteristics - Constant current power sources are used
primarily with coated electrodes. This type of power source has a relatively small change in
amperage and arc power for a corresponding relatively large change in arc voltage or arc
length, thus the name constant current. The characteristics of this power source are best
illustrated by observing a graph that plots the volt-
ampere curve. As can be seen in Figure 20, the
curve of a constant current machine drops down-
ward rather sharply and for this reason, this type of
machine is often called a "drooper."
1.9.1.1 In welding with coated electrodes, the
output current or amperage is set by the operator
while the voltage is designed into the unit. The
operator can vary the arc voltage somewhat by
increasing or decreasing the arc length. A slight
increase in arc length will cause an increase in arc
voltage and a slight decrease in amperage. A slight
decrease in arc length will cause a decrease in arc
voltage and a slight increase in amperage.
1.9.2 Constant Voltage Characteristics - Constant voltage power sources, also
known as constant potential, are used in welding with solid and flux cored electrodes, and
as the name implies, the voltage output remains relatively constant. On this type of power
source, the voltage is set at the machine and amperage is determined by the speed that
the wire is fed to the welding gun. Increasing the wire feed speed increases the amperage.
Decreasing the wire feed speed decreases the amperage.
1.9.2.1 Arc length plays an important part in welding with solid and flux cored electrodes,
just as it does in welding with a coated electrode. However, when using a constant voltage
power source and a wire feeder that delivers the wire at a constant speed, arc length
caused by operator error, plate irregularities, and puddle movement are automatically
34V - 290
A
32V - 300 A
30V - 308 A
VOLT / AMPERE CURVE
CONSTANT CURRENT
100 200 300
AMPERES
CONSTANT CURRENT VOLT / AMPERE CURVE
FIGURE 20
80
70
60
50
40
30
20
10
V
O
L
T
S
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
compensated for by the characteristics of this process. To understand this, keep in mind
that with the proper voltage setting, amperage setting, and arc length, the rate that the wire
melts is dependent upon the amperage. If the amperage decreases, this melt-off rate
decreases and if the amperage increases, so does the melt-off rate.
1.9.2.2 In Figure 21, we see that condition #2 produces the desired arc length, voltage,
and amperage. If the arc length is increased as in #1, the voltage increases slightly; the
amperage decreases considerably, and therefore, the melt-off rate of the wire decreases.
The wire is now feeding faster than it is melting
off. This condition will advance the end of the
wire towards the work piece until the proper arc
length is reached where again, the melt-off rate
equals the feeding rate. If the arc length is
decreased as in #3, the voltage drops off
slightly, the amperage is increased
considerably, and the melt-off rate of the wire
increases. Since the wire is now melting off
faster than it is being fed, it melts back to the
proper arc length where the melt-off rate
equals the feeding rate. This is often referred
to as a self-adjusting arc. These automatic
corrections take place in fractions of a second,
and usually without the operator being aware
of them.
1.9.2.3 There are a variety of different welding machines, each with its own unique
internal design. Our purpose is not to detail the function of each part of the machine, but to
emphasize that their main difference is in the way they control the voltage and amperage
output.
1.9.3 Types of Welding Power Sources - A great variety of welding power sources
are being built today for electric arc welding and we shall mention some of the major types
briefly. Welding power sources can be divided into two main categories: static types and
rotating types.
1.9.3.1 Static Types - Static type power sources are all of those that use commercially
generated electrical power to energize a transformer that, in turn, steps the line voltage
down to useable welding voltages. The two major categories of static power sources are
the transformer type and the rectifier type.
1 2 3
V
O
L
T
S
40
30
20
10
100 200 300 400
AMPERES
VOLT / AMPERE CURVE - CONSTANT VOLTAGE
FIGURE 21
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, PART B
1.9.3.1.1 The transformer type produce only alternating current. They are commonly
called "Welding Transformers." All AC types utilize single-phase primary power and are of
the constant current type.
1.9.3.1.2 The rectifier types are commonly called "Welding Rectifiers" and produce DC or,
AC and DC welding current. They may utilize either single phase or three phase input
power. They contain a transformer, but rectify the AC or DC by the use of selenium
rectifiers, silicon diodes or silicon controlled rectifiers. Available in either the constant
current or the constant voltage type, some manufacturers offer units that are a combination
of both and can be used for coated electrode welding, non-consumable electrode welding
and for welding with solid or flux cored wires.
1.9.3.2 Rotating Types - Rotating type power sources may be divided into two classifi-
cations:
1. Motor-Generators
2. Engine Driven
1.9.3.2.1 Motor-generator types consist of an electric motor coupled to a generator or
alternator that produces the desired welding power. These machines produced excellent
welds, but due to the moving parts, required considerable maintenance. Few, if any, are
being built today.
1.9.3.2.2 Engine driven types consist of a gasoline or diesel engine coupled to a generator
or alternator that produces the desired welding power. They are used extensively on jobs
beyond commercial power lines and also as mobile repair units. Both rotating types can
deliver either AC or DC welding power, or a combination of both. Both types are available
as constant current or constant voltage models.
1.9.4 Power Source Controls - Welding power sources differ also in the method of
controlling the output current or voltage. Output may be controlled mechanically as in
machines having a tapped reactor, a moveable shunt or diverter, or a moveable coil. Elec-
trical types of controls, such as magnetic amplifiers or saturable reactors, are also utilized
and the most modern types, containing silicon controlled rectifiers, give precise electronic
control.
1.9.4.1 A detailed discussion of the many types of welding power sources on the market
today is much too lengthy a subject for this course, although additional information on the
type of power sources for the various welding processes will be covered in Lesson II.
1.9.4.2 Excellent literature is available from power source manufacturers, however, and
should be consulted for further reference.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, GLOSSARY
APPENDIX A
LESSON I - GLOSSARY OF TERMS
AISI — American Iron and Steel Institute
Allotropic — A material in which the atoms are capable of transforming into two
or more crystalline structures at different temperatures.
Alternating — An electrical current which alternately travels in either direction in a
Current conductor. In 60 cycles per second (60 Hz) AC, the frequency
used in the U.S.A., the current direction reverses 120 times every
second.
Ampere — Unit of electrical rate of flow. Amperage is commonly referred to as
the “current” in an electrical circuit.
ASME — American Society of Mechanical Engineers
ASTM — American Society for Testing and Materials
Atom — The smallest particle of an element that posses all of the
characteristics of that element. It consists of protons, neutrons,
and electrons.
Carbon Steel — (Sometimes referred to as mild steel.) An alloy of iron and carbon.
Carbon content is usually below 0.3%.
Conductor — A material which has a relatively large number of loosely bonded
electrons which may move freely when voltage (electrical pressure)
is applied. Metals are good conductors.
Constant Current — (As applied to welding machines.) A welding power source which
will produce a relatively small change in amperage despite
changes in voltage caused by a varying arc length. Used mostly
for welding with coated electrodes.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, GLOSSARY
Constant Voltage — (As applied to welding machines.) A welding power source which
will produce a relatively small change in voltage when the
amperage is changed substantially. Used mostly for welding with
solid or flux cored electrodes.
Direct Current — An electrical current which flows in only one direction in a
conductor. Direction of current is dependent upon the electrical
connections to the battery or other DC power source. Terminals on
all DC devices are usually marked (+) or (-). Reversing the leads
will reverse the direction of current flow.
Electron — Negatively charged particles that revolve around the positively
charged nucleus in an atom.
Ferrous — Containing iron. Example: carbon steel, low alloy steels, stainless
steel.
Hertz — Hertz (Hz) is the symbol which has replaced the term “cycles per
second.” Today, rather than saying 60 cycles per second or simply
60 cycles, we say 60 Hertz or 60 Hz.
High Alloy Steels — Steels containing in excess of 10% alloy content. Stainless steel is
considered a high alloy because it contains in excess of 10%
chromium.
Induced Current or
Induction — The phenomena of causing an electrical current to flow through a
conductor when that conductor is subjected to a varying magnetic
field.
Ingot — Casting of steel (weighing up to 200 tons) formed at mill from melt
of ore, scrap limestone, coke, etc.
Insulator — A material which has a tight electron bond, that is, relatively few
electrons which will move when voltage (electrical pressure) is
applied. Wood, glass, ceramics and most plastics are good
insulators.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

LESSON I, GLOSSARY
Kilowatt — 1,000 watts
Low Alloy Steels — Steels containing small amounts of alloying elements (usually 1½%
to 5% total alloy content) which drastically improves their
properties.
Non-Ferrous — Containing no iron. Example: Aluminum, copper, copper alloys.
Ohm — Unit of electrical resistance to current flow.
Phase
Transformation — The changes in the crystalline structure of metals caused by
temperature and time.
Proton — Positively charged particles which are part of the nucleus of atoms.
Rectifier — An electrical device used to change alternating current to direct
current.
SAE — Society of Automotive Engineers
Transformer — An electrical device used to raise or lower the voltage and inversely
change the amperage.
Volt — Unit of electromotive force, or electrical pressure which causes
current to flow in an electrical circuit.
Watt — A unit of electrical power. Watts = Volts x Amperes
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

BASIC
WELDING FILLER METAL
TECHNOLOGY
A Correspondence Course
LESSON II
COMMON ELECTRIC ARC
WELDING PROCESSES
ESAB ESAB Welding &
Cutting Products
©COPYRIGHT 2000 THE ESAB GROUP, INC.
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

TABLE OF CONTENTS
LESSON II
COMMON ELECTRIC ARC WELDING
PROCESSES
2.1 INTRODUCTION .............................................................................. 1
2.2 SHIELDED METAL ARC WELDING ............................................... 1
2.2.1 Equipment & Operation ..................................................................... 2
2.2.2 Welding Power Sources .................................................................... 2
2.2.3 Electrode Holder................................................................................ 4
2.2.4 Ground Clamp ................................................................................... 4
2.2.5 Welding Cables ................................................................................. 4
2.2.6 Coated Electrodes ............................................................................ 4
2.3 GAS-TUNGSTEN ARC WELDING .................................................. 5
2.3.1 Equipment & Operation ..................................................................... 6
2.3.2 Power Sources .................................................................................. 7
2.3.3 Torches.............................................................................................. 10
2.3.4 Shielding Gases ................................................................................ 11
2.3.5 Electrodes ......................................................................................... 12
2.3.6 Summary ........................................................................................... 13
2.4 GAS METAL ARC WELDING .......................................................... 13
2.4.1 Current Density .................................................................................. 14
2.4.2 Metal Transfer Modes ........................................................................ 15
2.4.3 Equipment and Operation .................................................................. 17
2.4.4 Power Source.................................................................................... 18
2.4.5 Wire Feeder ...................................................................................... 19
2.4.6 Welding Gun ...................................................................................... 20
2.4.7 Shielding Gases ................................................................................ 21
2.4.7.1 Short Circuiting Transfer .................................................... 22
2.4.7.2 Spray Arc Transfer ............................................................ 23
Lesson 1
The Basics of Arc
Welding
Lesson 2
Common Electric
Arc Welding
Processes
Lesson 3
Covered Electrodes
for Welding
Mild Steels
Lesson 4
Covered Electrodes
for Welding Low
Alloy Steels
Lesson 5
Lesson 6
Carbon & Low Alloy
GMAW,GTAW,SAW
Lesson 7
Flux Cored Arc
Electrodes Carbon
Low Alloy Steels
Lesson 8
Hardsurfacing
Electrodes
Lesson 9
Estimating &
Comparing Weld
Metal Costs
Lesson 10
Filler Metals

Esab basic welding fillar metal technology

Esab basic welding fillar metal technology

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