Mechanical and Microstructural Characterization of Weld Joints Obtained with Cellulosic Electrodes Fabricated by TREFISOUD El-EULMA

Mechanical and Microstructural Characterization of
Weld Joints Obtained with Cellulosic Electrodes
Fabricated by TREFISOUD El-EULMA
By
HABCHI AHMED MATHIL
B.S., Ferhat Abbas University of Setif
A THESIS
Submitted in partial fulfillment of the requirements for the degree
MASTER OF SCIENCE
in Mechanic of Materials
Department of Applied Mechanics
Institute of Optics and Precision Mechanics
FERHAT ABBAS UNIVERSITY OF SETIF
Setif, ALGERIA
2017
Supervised by:
Professor Louahdi Rachid

Abstract
Welding is the most important joining technique in the industry, and its evaluation plays a prominent
role in determining the final properties of the joints. Therefore, in the current work, the microstructure
and mechanical properties of a weld metal joints deposited with Trefisoud cellulosic electrodes was
investigated. Different microstructures of various sites were observed and identified using optical and
electron microscopy. Mechanical properties of the weldments were investigated through tensile,
Charpy V as well as hardness testing. XRF spectrometry was used to determine the chemical
compositions of the weld. SEM fractography was conducted to determine the fracture modes and
mechanisms.
Keywords: SMAW, welds, cellulosic, electrodes, microstructure, mechanical, characterization.

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Table of Contents
List of Figures................................................................................................................................ vi
Acknowledgements....................................................................................................................... vii
Dedication....................................................................................................................................viii
Nomenclature................................................................................................................................. ix
List of Abbreviations in alphabetical order ............................................................................... ix
Chapter 1 - Introduction.................................................................................................................. 1
1.1 General.................................................................................................................................. 1
1.2 Motivation............................................................................................................................. 2
1.3 Aim and Objectives of Present Work ................................................................................... 2
Chapter 2 - Literature Review......................................................................................................... 3
2.1 Overview of Welding............................................................................................................ 3
2.2 Types of welding .................................................................................................................. 4
2.2.1 Fusion Welding.............................................................................................................. 4
2.2.2 Solid-state welding......................................................................................................... 4
2.3 Arc welding........................................................................................................................... 5
2.3.1 Shielded Metal Arc Welding.......................................................................................... 6
2.3.2 Other Arc-Welding Processes........................................................................................ 7
A/ Submerged arc welding.................................................................................................. 7
B/ Gas tungsten arc welding ............................................................................................... 7
C/ Gas metal arc welding.................................................................................................... 8
D/ Plasma arc welding ........................................................................................................ 8
E/ Electron beam welding................................................................................................... 8
2.4 Electrode Overview .............................................................................................................. 8
2.5 Types of Arc Welding Electrodes....................................................................................... 10
2.5.1 Non consumable electrodes ......................................................................................... 10

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2.5.2 Consumable electrodes ................................................................................................ 11
2.6 Electrode Coating Components Classification ................................................................... 11
2.6.1 Gas forming component............................................................................................... 11
2.6.2 Slag forming component.............................................................................................. 12
2.6.3 Reducing component ................................................................................................... 12
2.6.4 Stabilizing component ................................................................................................. 12
2.6.5 Binding component...................................................................................................... 12
2.7 Types of Electrode Coatings............................................................................................... 12
2.7.1 Cellulosic electrode coating......................................................................................... 13
2.7.2 Basic electrode coating ................................................................................................ 13
2.7.3 Rutile electrode coating ............................................................................................... 14
2.7.4 Iron oxide electrode coating......................................................................................... 14
2.8 Characterization of Welds .................................................................................................. 14
2.8.1 Structure....................................................................................................................... 16
A/ Macrostructure............................................................................................................. 16
B/ Weld Microstructure .................................................................................................... 16
2.8.2 Compositional analysis ................................................................................................ 17
2.8.3 Mechanical Testing...................................................................................................... 18
A/ Tension test.................................................................................................................. 19
B/ Hardness tests............................................................................................................... 19
C/ Fracture toughness ....................................................................................................... 20
Chapter 3 - Experimental Work.................................................................................................... 21
3.1 Production of Experimental Weld Metals .......................................................................... 21
3.1.1 The weld joint plate (for mechanical tests).................................................................. 21
3.1.2 The welding pad (for chemical analysis)..................................................................... 22
3.2 Sample Preparation............................................................................................................. 23
3.2.1 Mechanical tests specimens ......................................................................................... 23
3.2.2 Polishing and Etching .................................................................................................. 24

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3.3 Chemical Analysis .............................................................................................................. 24
3.4 Mechanical Investigations .................................................................................................. 25
3.4.1 Tensile testing .............................................................................................................. 25
3.4.2 Charpy impact testing .................................................................................................. 26
3.4.3 Hardness testing........................................................................................................... 27
3.5 Microstructure Characterization Techniques...................................................................... 28
3.5.1 Optical Light Microscopy (OLM)................................................................................ 28
3.5.2 Scanning electron microscopy (SEM) ......................................................................... 29
Chapter 4 - Results and Discussion .............................................................................................. 30
4.1 Tensile Test......................................................................................................................... 30
4.2 Charpy impact..................................................................................................................... 31
4.3 Chemical composition ........................................................................................................ 31
4.4 Hardness Tests .................................................................................................................... 32
4.5 Metallographic Examinations............................................................................................. 34
Chapter 5 - Conclusion ................................................................................................................. 38
References..................................................................................................................................... 39
Appendix A - Master chart of welding and allied processes ........................................................ 41
Appendix B - Principal welding process. ..................................................................................... 42
Appendix C - Electrodes production process flow chart .............................................................. 43
Appendix D - Cellulosic Electrodes Specifications Sheets .......................................................... 44
1 - WELDCOTE METALS ...................................................................................................... 44
2 – LINCOLN ELECTRIC....................................................................................................... 45
3 – ESAB .................................................................................................................................. 46

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List of Figures
Figure 2-1 Shielded metal arc welding [4]..................................................................................... 6
Figure 2-2 Different types of Welding Rods ................................................................................. 13
Figure 2-3 Typical weld defects.................................................................................................... 15
Figure 2-4 Grain shape distribution in a typical weld joint. [6].................................................. 17
Figure 2-5 distribution of stress in a simple weld ........................................................................ 18
Figure 3-1 Specimens positioning in the test plate....................................................................... 22
Figure 3-2 Pad for chemical analysis of undiluted weld metal.................................................... 23
Figure 3-3 Descriptive image of the position of a tensile (a); Charpy (b) specimen on the weld
joint. ...................................................................................................................................... 23
Figure 3-4 (left) Zeiss Axiovert 40 MAT light optical microscope & (right) MECATECH-234
Polishing machine at (LPMMM). ......................................................................................... 24
Figure 3-5 SHIMADZU Lab Center XRF-1800 (Trefisoud Control Laboratory)........................ 25
Figure 3-6 Zwick Roell Z250 machine (Trefisoud Control Laboratory)...................................... 26
Figure 3-7 Cylindrical tensile specimen after fracture with dimensions in mm........................... 26
Figure 3-8 Charpy V specimens after being fractured................................................................. 27
Figure 3-9 TUKON 2500 Wilson Hardness machine at (LPMMM)............................................. 28
Figure 3-10 PHILIPS ESEM XL30 Scanning Electron Microscopy. ........................................... 29
Figure 4-1 Hardness filiation results............................................................................................ 32
Figure 4-2 Hardness map of the studied weld joint specimen with a real photo. ........................ 33
Figure 4-3 Indentations in two different regions of the weld metal. (Bright region: ferrite, dark
region: pearlite).................................................................................................................... 34
Figure 4-4 Optical micrographs showing the different microstructures of the weld joint with
respect to a typical macrograph. .......................................................................................... 35
Figure 4-5 SEM micrographs for the three main zones of the weld joint..................................... 36
Figure 4-6 Fractographs of the ruptured surfaces for the broken Charpy v specimens .............. 37

vii
Acknowledgements
All praise, thanks and adorations is due to ALLAH the Almighty, the uncreated creator of
all creatures who has taught man by pen.
This project would not have been able to see the light without the extreme help and support
I received from several individuals and organizations. I hereby want to thank all of those who
contributed in this work in any kind of way.
I first would like to thank Ferhat Abbas University of Setif for allowing me to continue
my graduate studies in the first place, and all the teaching staff for making sure we got the right
education and for providing an excellent learning atmosphere.
I would like to express my deepest thanks and sincere gratitude to my supervisor Professor
Louahdi Rachid, not only for his close and encouraging support during the course of this project.
But for his kind support and tremendous impact on my success throughout my years of study.
I cannot express enough thanks to Dr. Abid Taher Chief of welding products section at
Trefisoud factory for granting me access to their enterprise, and for his great assistance and support
throughout the project.
Last, but certainly not least, I would like to extend special thanks to Fares and Kenza for
helping me with The SEM characterization.
A big word of thanks and gratitude to Mom, Dad and my Siblings for their tremendous
emotional and financial support during my whole years of study.
Finally, I am truly grateful to all the students I met during my years of study from all around
the country for their joyful and pleasant company and for giving me a priceless Experience.
To you all I owe my highest gratitude.

viii
Dedication
‫إىل‬‫أمي‬‫و‬‫أبي‬
To my Parents
I would not have been able to accomplish this
without their support

ix
Nomenclature
The International System for units (SI) has been used:
List of Abbreviations in alphabetical order
AC: Alternative current.
AW: Arc welding.
AWS: American welding society.
BM: Base Metal.
DC: Direct current.
DFW: Diffusion welding.
FRW: Friction welding.
FZ: Fusion Zone.
GMAW: Gas Metal Arc Welding.
GTAW: Gas Tungsten Arc Welding.
HAZ: Heat Affected Zone.
LOM: Light optical microscopy.
LPMMM: Laboratory of Physics and
Mechanics of Metallic Materials.
MAG: Metal Active Gas.
MIG: Metal inert Gas.
MMA: Manual Metal Arc.
OFW: Oxyfuel gas welding.
OLM: Optical Light Microscopy.
RW: Resistance welding.
SEM: Scanning electron microscopy.
SMAW: Shielded Metal Arc Welding.
TIG: Tungsten Inactive Gas.
USW: Ultrasonic welding.
XRF: X-ray fluorescence.

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Chapter 1 - Introduction
1.1 General
Evidence of several joining techniques was documented as early as in the Bronze Age,
there was always a need to create or repair metal structures by joining the pieces of metals
through various fusion processes using heat in almost all cases. Welding is one of the vital
processes that helped in the industrial revolution and until our time, welding is still the
backbone of many industries.
The SMAW process started at the Beginning of the XX century. The joining is obtained
by electrical arc established between consumable covered electrode and work piece. Even as a
lower productivity welding process, compared to others it remains as an interesting alternative
in manufacturing operations and maintenance. This fact is associated mainly to its versatility.
Shielded metal welding electrodes are made up of two major components, the core wire
and the flux coating. In iron base welding electrodes, the core wire is common and inexpensive.
The carbon steel and low alloy SMAW electrodes, with a few exceptions, generally do not have
large amounts of alloying elements added to them. Therefore, these electrodes are somewhat
tolerant of some variation in the electrode composition while still meeting the basic mechanical
requirements of that electrode.
Cellulosic based electrodes often have additional requirements requested by the
customer which are above the general requirements. This requires the electrodes to be
manufactured to produce a weld deposit with tighter constraint of the all-over mechanical
properties than the standard range.
The aim of this work was to evaluate the weld metal deposited by the coated electrode
with the new better performance flux formulation. The weld metal produced was subjected to
chemical and metallographic analysis, hardness tests, tensile test (to determine yield strength,
ultimate strength and strain) and impact toughness (Charpy - V notch test) to determine the
energy absorbed by the impact fracture of the material. Additionally, the fractured specimens
was analyzed by Scanning Electron Microscopy.

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This dissertation is presented in the form of five chapters. It starts with an introduction
followed by a literature review which contains the theoretical background of this work. After that
comes the experimental part which describes the work done, then the experimental results and their
discussion and we finished by a general conclusion.
1.2 Motivation
SMAW is used extensively in key industries, for instance in ship building, pipeline,
transportation, offshore, maintenance and repair heavy machinery and many other fields. All
require a steady rate to improve the whole process. Judging by the effect SMAW had on
industry since its invention, one understands how important it is in our world. Testing the new
TREFISOUD Cellulosic electrode will add more knowledge and will help develop the whole
welding process giving the customer a better choice to pick the best electrode according to the
desired application.
1.3 Aim and Objectives of Present Work
TREFISOUD is a company which develops and produces welding Electrodes among
other products. It was established in 1978, and since then the company produces and
manufactures many different types of welding electrodes. In the past years TREFISOUD tried
to produce the cellulosic coated electrodes to add to their collection, but they had problems
with the produced electrode performance.
At the present time, the company is trying to solve this problem with a new coating
formula. This work has been conducted to evaluate the performance of welded joint of the new
produced cellulosic electrodes.
The following issues have been investigated in the project:
What is the chemical composition of the Weld Metal?
What is the difference in the microstructure of the different kinds of samples?
What are the mechanical properties of the welds? Such as hardness, yield strength, etc.
What is the relationship between composition, structure and mechanical properties?

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Chapter 2 - Literature Review
2.1 Overview of Welding
Welding is a production or a fabrication process of joining two or more materials
together, usually metals or thermoplastics to achieve coalescence. Welding is performed by the
application of heat and pressure to melt the work piece together often with the addition of filler
material to form a pool of molten material which form the welded joint after solidification.
Many welding processes are accomplished by heat alone, with no pressure applied; others by
a combination of heat and pressure; and still others by pressure alone, with no external heat
applied. Welding processes are used to produce joints with properties similar to those of
materials being joined, these materials are called parent materials. [1]
The assembling of parts that are joined by welding is called a weldment. The three
main components to create a weld are:
- 1. A heat source: A heat source is an important component in the creation of a weld,
which includes an electric arc, a flame, pressure or friction. However, the most
common heat source is the electric arc.
- 2. Shielding: Shielding is the use of a gas or another substance to protect the weld
from atmospheric contamination of the molten weld.
- 3. Filler materials: They are used in joining two pieces of materials together, usually
metals.
Welding is extensively used in fabrication and has found application as an alternative
method for casting or forging and as a replacement for bolted and riveted joints. It is also used
as a repair medium, for example to reunite metals at a crack, to build up a small part that has
broken off, such as gear tooth or to repair a worn surface such as a bearing surface. [2]
Advantages of welding as a joining process include high joint efficiency, simple set up,
flexibility and low fabrication cost [3].
Today, many processes of welding have been developed and probably there is no
industry which is not using welding in the fabrication of its product in one form or another.

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2.2 Types of welding
Appendix A & B contains a master chart of welding and allied processes and a
classification shows the position of the SMAW among various welding process.
2.2.1 Fusion Welding
Fusion-welding processes use heat to melt the base metals. In many fusion welding
operations, a filler metal is added to the molten pool to facilitate the process and provide bulk
and strength to the welded joint. A fusion-welding operation in which no filler metal is added
is referred to as an autogenous weld.
The fusion category includes the most widely used welding processes, which can be
classified into the following general groups.
 Arc welding (AW): Arc welding refers to a group of welding processes in which heating
of the metals is accomplished by an electric arc. Some arc-welding operations also apply
pressure during the process and most utilize a filler metal.
 Resistance welding (RW): Resistance welding achieves coalescence using heat from
electrical resistance to the flow of a current passing between the faying surfaces of two
parts held together under pressure.
 Oxyfuel gas welding (OFW): These joining processes use an oxyfuel gas, such as a mixture
of oxygen and acetylene, to produce a hot flame for melting the base metal and filler metal,
if one is used.
 Other fusion-welding processes: Other welding processes that produce fusion of the metals
joined include electron beam welding and laser beam welding. [4]
2.2.2 Solid-state welding
Solid-state welding refers to joining processes in which coalescence results from
application of pressure alone or a combination of heat and pressure. If heat is used, the

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temperature in the process is below the melting point of the metals being welded. No filler
metal is utilized. Representative welding processes in this group include:
 Diffusion welding (DFW): Two surfaces are held together under pressure at an elevated
temperature and the parts coalesce by solid-state diffusion.
 Friction welding (FRW): Coalescence is achieved by the heat of friction between two
surfaces.
 Ultrasonic welding (USW): Moderate pressure is applied between the two parts and an
oscillating motion at ultrasonic frequencies is used in a direction parallel to the
contacting surfaces. The combination of normal and vibratory forces results in shear
stresses that remove surface films and achieve atomic bonding of the surfaces. [4]
2.3 Arc welding
The term arc welding applies to a large and diversified group of welding processes that
use an electric arc as the source of heat to melt and join metals. The formation of a joint between
metals being arc welded may or may not require the use of pressure or filler metal.
The arc is struck between the workpiece and an electrode that is manually or
mechanically moved along the joint or that remains stationary while the workpiece is moved
underneath it.
The electrode will be either a consumable wire or rod or a nonconsumable carbon or
tungsten rod which serves to carry the current and sustain the electric arc between its tip and
the workpiece. When a nonconsumable electrode is used, a separate rod or wire can supply
filler metal if needed. The consumable electrode, however, will be specially prepared so that it
not only conducts the current and sustains the arc but also melts and supplies filler metal to the
joint and may produce a slag covering as well. [5]
The major arc welding processes and their unique features are described in the
following pages.

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2.3.1 Shielded Metal Arc Welding
Manual Metal Arc welding (MMA) is often referred to as Shielded Metal Arc Welding
(SMAW) or stick electrode welding, is one of the oldest, simplest, and most versatile joining
processes; consequently, about 50% of all industrial and maintenance welding is performed by
this process. The electric arc is generated by touching the tip of a coated electrode against the
workpiece.
The arc is struck by bringing the electrode in contact with the work surface and then
immediately pulling them apart about 2 to 3 mm, thus ionizing the gas between the two
electrical ends. [6]
The heat generated melts a portion of the electrode tip, its coating, and the base metal
in the immediate arc area. The molten metal consists of a mixture of the base metal (the
workpiece), the electrode metal, and substances from the coating on the electrode; this mixture
forms the weld when it solidifies. The electrode coating deoxidizes the weld area and provides
a shielding gas, to protect it from oxygen in the environment.
A bare section at the end of the electrode is clamped to one terminal of the power source,
while the other terminal is connected to the workpiece being welded. [7]
The SMAW process is the most widely used welding process. It is the simplest, in terms
of equipment requirements, but it is, perhaps, the most difficult in terms of welder training and
skill-level requirements.
Figure 2-1 Shielded metal arc welding [4]

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SMAW may utilize either direct current (dc) or alternating current (ac). Generally, dc
is used for smaller electrodes. Larger electrodes utilize alternating current to eliminate
undesirable arc blow conditions. (Arc blow is the deflection of an arc from its normal path
because of magnetic forces.) [8]
Shielded metal arc welding has the greatest flexibility of all the welding processes,
because it can be used in all positions, with virtually all base-metal thicknesses, and in areas of
limited accessibility, which is a very important capability. [9]
Appendix B is a classification shows the position of the Shielded Metal Arc Welding
among various welding process.
2.3.2 Other Arc-Welding Processes
A/ Submerged arc welding
This is an automatic process developed primarily for the production of high quality butt
welds in thicker steel plates. Submerged arc welding is different from other arc welding
processes in a way that a blanket of fusible, granular material (flux) which consists of lime,
silica, manganese oxide, calcium fluoride and other compounds is used for shielding the arc
and the molten metal. The process provides very high deposition rate and a deep penetration
and it is used for welding pressure vessels and high pressure pipes.
B/ Gas tungsten arc welding
Inert gases are used to keep contaminants away from contacting the metal. Gas tungsten
arc welding is faster, produces cleaner welds and can weld metals considered to be difficult or
impossible to weld, it uses a non-consumable electrode and is used for welding stainless and
light gauge materials. The equipment needed for gas tungsten arc welding are welding torch,
welding power source and a source of inert gas.

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C/ Gas metal arc welding
This welding operation is performed using direct current reverse polarity as it gives both
good cleaning action and fast filler metal deposition rate. Gas metal arc welding electrode uses
a consumable electrode which is fed through the electrode holder into the arc and at the same
speed the electrode is melted and deposited in the weld.
D/ Plasma arc welding
Plasma is defined as a gas heated to at least practically ionized condition, enabling it to
conduct an electric current. Plasma arc refers to a constricted electric arc which is achieved by
passing through the water cooled orifice. Plasma arc is made to pass through a small hole in a
nozzle which surrounds a non-consumable electrode. This type of welding process has a small
heat affected zone and has high welding speed. It is used for welding stainless steel, nickel
alloys, refractory and metals in aerospace.
E/ Electron beam welding
In this process the metal to be joined are brought rather close together and a concentrated
stream of high energy electron emitted from a high voltage (150kv) electrode gun is directed
on to the surface of the work piece, causing fusion to take place. This welding process is usually
performed in the vacuum and thus no flux is required, as there is no air present to contaminate
the weld metal. Electron beam welding find application in aerospace and automotive industries.
2.4 Electrode Overview
Electrode is a specially prepared rod or wire that not only conducts electric current and
sustain the arc, but also melts and supplies the filler metal to the joint; as in the case of a
consumable electrode [8]. In arc welding, an electrode is used to conduct current through a
work piece to fuse two pieces of materials together. Depending upon the process, an electrode

9
is either consumable as in the case of shielded metal arc welding or non-consumable such as
gas tungsten welding [10].
Electrode is a metal in rod or wire form with baked minerals around it, which can also
be referred to as filler wire used in electric arc welding to maintain the arc and at the same time
supply molten metal. Electrode used in arc welding is basically made of steel core wire, and
the covering (coating). Electrode can be bare, fluxed and can be heavy coated. Bare electrodes
have limited applications as during welding operations, they are exposed to oxygen or nitrogen
of the surrounding air which form non-metallic constituents and they are trapped in the rapidly
solidifying weld metal, thereby decreasing the strength, and ductility of the weld metal. When
bare electrodes are used, the weld appearance is poor, and there is difficulty of maintaining a
stable arc. Bare electrodes are generally used for welding wrought iron.
Improved weld may be obtained by applying light coating of flux on the rod using a
dusting or washing process. The flux coating on an electrode assists both in eliminating
undesirable oxides and preventing their formation. The heavy coated electrodes are by far the
most important and the most widely used [11].
The AWS classifies electrodes on the basis of chemical composition of their undiluted
weld metal or mechanical properties or both. Welding current and position are also indicated.
Example of electrode designation system is E6010, which is explained below:
- Letter E designates an electrode.
- Number 60 signifies that the tensile strength of the deposited weld metal is minimum
60,000 psi (60 thousands of pounds per square inch).
- The second-to-last digit (1) represents the welding position the electrode is suitable for
use (1 is all positions).
- The last digit (0) refers to the covering type and current type. In this case, 0 indicates
the covering is of cellulose, and the electrode is good for all positions of welding. [6]
Fluxes are chemical compounds which are composed of different minerals such as
oxides, carbonates and fluorides used to prevent oxidation or the formation of oxides and other
unwanted chemical reactions. Fluxes help to make welding easier and ensure making of a good
and sound weld. [12] Fluxes and their slags provide a blanket to protect the weld metal from

10
the action of extraneous gases, flux can also perform cleaning, alloying actions and also
produces shielding gas that prevents molten weld metal from oxidation. [13]
Fluxes protect, prevent atmospheric oxidation and clean up welded joint chemically and
reduce impurities in the metal joining processes. [1]
The type of flux coating depends on the weld metal composition. Electrode coatings
facilitate striking the arc and also provide a stable arc. Coating on an electrode also provides
gaseous shield, and prevents the oxidation of molten weld metal, a good flux covered electrode
will produce a weld that has an excellent physical and chemical properties.
SMAW Electrodes production process flow is explained in Appendix C.
2.5 Types of Arc Welding Electrodes
There are two main types of arc welding electrodes. These are consumable electrodes
(used in shielded metal arc welding) and non-consumable electrodes (used in plasma arc
welding and tungsten inert gas welding).
2.5.1 Non consumable electrodes
Non-consumable or Refractory electrodes are those which do not melt away or
consumed during the welding process. These electrodes involve the use of high melting point
materials such as carbon, pure tungsten, or alloy tungsten.
These types of electrodes do not burn away with usage, hence they last longer and can
be used with a wider variety of metals, especially thicker metals. Non consumable electrodes
are used with inert gas for shielding the arc.
Main features of non-consumable welding electrode:
- Filler metal is needed to fill up the gap between the two metal parts.
- Used in carbon arc welding and Tungsten Inert Gas (TIG) welding.
- Tungsten electrodes are much costlier than carbon or graphite electrodes. Tungsten
alloy electrodes are costlier. [15]

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2.5.2 Consumable electrodes
These types of electrodes slowly burn away with usage and are replaced when they
become too short (50mm) for further use.
Main features of Consumable welding electrode:
- They are more thermally efficient than non-consumable electrodes.
- They are made of different materials depending upon the need and the chemical
composition of metals to be joined.
- They are used in MIG welding in the form of bare electrode.
- Most commonly used core material is mild steel, low alloy steel and nickel steel.
2.6 Electrode Coating Components Classification
The principal difference between various types of electrodes is in their coatings and by
varying the coatings it is possible to greatly alter the operating characteristics of electrodes.
[16]
Electrode coating is composed of a mixture of various organic and inorganic materials,
these materials are termed components and these components can be sub divided as follows:
2.6.1 Gas forming component
The gas forming components are organic materials, such as cellulose, starch and wood
pulp. They form gas layer, thus isolating the weld zone from ambient air. Organic materials are
present in much larger quantities in electrodes baked at low temperature.

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2.6.2 Slag forming component
These are mineral silicates, these components constitute a slag, which by covering the
molten metal prevent it from the surrounding atmosphere and also ensure gradual cooling of
molten metal.
2.6.3 Reducing component
These are components that reduce the oxides that are likely to be formed during
welding.
2.6.4 Stabilizing component
These also form slag. In the presence of arc, the component ionizes the zone between
the electrode and the part to be welded, thus ensuring a stable burning arc.
2.6.5 Binding component
These components serve for binding other components, which make it possible to
obtain a solid coating which adheres to the metal core, examples of these components are
sodium silicates and potassium silicates. [11]
2.7 Types of Electrode Coatings
There are four main types of electrode coatings on which all mild steel and low alloy
steel are based.

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2.7.1 Cellulosic electrode coating
Cellulosic-covered electrodes have been used for shielded metal arc welding (SMAW)
circumferential welding of line pipe over many decades. They are characterized by electrode
coverings containing organic matter. [16]
These coatings contain over 30 percent organic materials mostly cellulose. In the arc,
the coating decomposes to give a large volume of shielding gas, such as hydrogen, carbon
monoxide and carbon dioxide. These gases shield the weld and also provide good weld metal
properties.
Cellulose coated electrodes are designed to provide a smooth stable arc forceful enough
to achieve deep penetration into the base metal. This electrode exhibits high deposition
efficiency and low spatter loss. It produces a weld puddle that wets and spreads well, yet sets
up fast enough to make this electrode ideal for vertical up or vertical down welding techniques.
Cellulosic electrodes are most commonly used for out-of-position welding such as field
construction, ship yards, water towers, pressure vessels, pressure pipes, steel castings, plain
and galvanized steel storage tanks, etc.
2.7.2 Basic electrode coating
These electrodes are made up of calcium carbonates, fluorite, clay, asbestos and other
minerals. They are also known as low hydrogen electrodes; speed of deposition and weld
penetration are high.
Figure 2-2 Different types of Welding Rods

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Basic electrodes produce a slag having a lower melting point than that from rutile and
acid electrodes, Due to the very high temperatures involved (up to 500°C) in the manufacture
of basic electrodes, the moisture content of the coating is low when the electrodes are supplied.
As a result, the hydrogen content in basic weld metals is low, thus providing good cold cracking
performance. [20]
2.7.3 Rutile electrode coating
The coating contains 50 percent titanium oxide (TiO2) as minerals, this compound
gives good arc stability and low operating voltage, so that it can be readily used with alternating
current. Electrodes of this type produce an arc that is easy to strike and re-strike.
They are very easy to use and produce neat welds with an easily removable slag. The
evenness of the weld bead and the resulting good connection to the base metal at the joint edges
generally results in high fatigue strength. Unfortunately, these electrodes produce a higher
hydrogen content in the weld metal, which introduces the risk of hydrogen Embrittlement and
cracking and restricts their use to welding carbon steel having a minimum ultimate tensile
strength less than 440 MPa. Rutile electrodes are suitable for standard structural steel and
shipbuilding steel. [18]
2.7.4 Iron oxide electrode coating
This coating is based on iron oxide, manganese oxide and associated silicates.
Depending on other constituents of the coating, the high oxygen content can lead to a low
carbon weld deposit of low strength or a well oxidized deposit with good strength and ductility.
Because of its low operating voltage, the electrode is suitable for use with DC or AC. The
electrode produces low spatter, high deposition rate and a good weld penetration. [17]
2.8 Characterization of Welds
Welds can be characterized according to a number of criteria, including the welding
process used, size, shape, mechanical properties, chemical composition, and a number of

15
others. The appropriate methods of characterization depend on the weld's function and the
particular set of properties required for the application. In some instances, the ability of a weld
to function successfully can be addressed by characterizing the size or shape of the weld. An
example of this is where factors related to the welding procedure, such as inadequate weld size,
convexity of the bead, or lack of penetration, may cause a weld to fail.
It is important to characterize metallurgical factors such as weld metal composition and
microstructure. Examples might include welds for which the goal is to avoid failures due to
inadequate strength, ductility, toughness, or corrosion resistance. In general, the goals of weld
characterization are to assess the ability of a weld to successfully perform its function, to
thoroughly document a weld and welding procedure that have been demonstrated to be
adequate, or to determine why a weld failed.
Typical weld defects are shown in Figure 2-3. These are some of the commonly
detected defects in typical weld; however, their presence, variance, and appearance differ
according to the welding process. [6]
Figure 2-3 Typical weld defects.

16
2.8.1 Structure
A/ Macrostructure
Several factors associated with the production and performance of welds are
macroscopic and easily observed. The most obvious of these are the size, shape, and general
appearance of the weld. To a large extent, these parameters depend on the geometry of the weld
joint and the welding process selected.
A number of techniques are widely used to assess the presence of surface and
subsurface defects in welds. The most common of these are liquid penetrant inspection for
surface cracks, magnetic particle inspection, x-ray radiography, and ultrasonic inspection.
B/ Weld Microstructure
In many cases, it is important to examine and characterize the weldment microstructure
and to understand its formation and effects on properties.
The microstructure of a weld consists of three regions as shown in Figure 2-4: a fusion
zone (material that has been melted); a heat affected zone (material that was not melted, but
whose microstructure has been altered); and the base metal.
The parameters used to characterize the weld microstructures, such as grain size, grain
morphology, and the amount of the various phases or micro constituents present, are those used
to characterize homogeneous materials (Figure 2-4).
Microstructural characterization of welds has two purposes: to evaluate the
microstructure with respect to properties and to relate the microstructure to the process used.
The ultimate goal is to optimize the process to produce the most desirable microstructure. In
general, the effects of a process and parameters on microstructure are due to the compositional
and thermal effects. The compositional effects are largely limited to the fusion zone. [19]

17
Figure 2-4 Grain shape distribution in a typical weld joint. [6]
2.8.2 Compositional analysis
The composition of a weld will have a significant effect on its performance,
contributing to both the mechanical and corrosion properties of the weld.
The composition of a weld is affected by the base metal composition, the composition
of any filler metal used (and dilution between the two), reactions with flux or shielding gas,
and any material losses associated with the process. These factors are, in turn, largely controlled
by the welding setup, process selection, parameters, and stability.
Characterization of welds requires techniques with sufficient spatial resolution to
characterize their inhomogeneity. Scanning electron microscopy with wavelength or energy
dispersive x-ray analysis systems, electron microprobes, and x-ray fluorescence techniques are
often employed. The most commonly used method for compositional analysis of welds is
optical emission spectroscopy.

18
2.8.3 Mechanical Testing
A number of mechanical properties are used to characterize welds, including strength,
ductility, hardness, and toughness. In general, the same samples and procedures are used in
other areas of metallurgy.
With the help of Figures 2-4 and 2-5, we can understand the effect of heating and
cooling in a simple weld. In more complex joints, the stresses are more complex and have more
serious implications on the performance of the weldments.
A weld is rapidly deposited along the edge of two pieces of metal. The entire weld zone
is still at a high temperature when the weld is completed. At high temperature, the metal close
to the weld attempts to expand in all directions, as it is prevented (restrained) by the adjacent
cold metal. Because it is being restrained from lateral expansion (elongating), the metal close
to the weld is compressed. [6]
Figure 2-5 distribution of stress in a simple weld

19
During cooling, the unstable zone attempts to contract again, and now the cold metal
surrounding it restrains it. As a result, the unstable zone becomes stressed in tension. [6]
However, a prominent concern regarding the mechanical performance of welds is the
direct comparison with base material. The goal is to ensure that the weld is not the weakest
component of a structure. Here are the testing methods which can be used to examine and
evaluate the expected performance of welded joints.
A/ Tension test
The basic data on the strength and ductility of materials are generally obtained from an
engineering tension test in which a machined specimen is subjected to an increasing uniaxial
load while simultaneous observations of linear extension are made. The test results are plotted
in the form of a stress-strain curve. Two standard measurements of ductility are derived from
the engineering tension test the percent elongation and the percent reduction of area. The
percent elongation is the ratio of the increase in gage length to its original gage length.
The tension testing of welds is somewhat more involved than for base metal because
the weld test section is heterogeneous in nature, composed of the deposited weld metal, the
heat-affected zone, and the unaffected base metal. [21]
B/ Hardness tests
Hardness testing may be used in weld evaluations, either alone or to complement
information gained through the tension tests previously described. Routine testing methods for
the hardness testing of metals are well established. These include the Brinell, Vickers, and
Knoop hardness tests, which use the area of indentation under load as the measure of hardness,
and the Rockwell test, which relates hardness to the depth of indentation under load. Hardness
measurements can provide information about the metallurgical changes caused by welding.

20
C/ Fracture toughness
Fracture toughness is a property of the metal which defines its resistance to brittle
fracture. A variety of fracture toughness testing procedures are used throughout the world. In
this work only the Charpy V-notch test will be discussed.
The Charpy V-notch test was developed in 1905 to make qualitative assessments of the
influence of notches on the fracture behavior of steels in the transition temperature range. Since
that time, this test procedure has gained worldwide acceptance and today is used routinely for
steel specification and quality assurance. [5]

21
Chapter 3 - Experimental Work
Organizational chart summarizes all the work done in the context of this research.
3.1 Production of Experimental Weld Metals
The technique of Shielded Metal Arc Welding SMAW was employed to produce all
experimental weld metals analyzed in this work. The set up principles of SMAW welding are
shown schematically in Figure 2-1.
3.1.1 The weld joint plate (for mechanical tests)
Welded joints were made according to the French standard NF A 81-302 using 270 mm
plates with a backing plate as shown in Figure 3-1. The joints were ‘buttered’ prior to welding
which involved the deposition of multiple layers of weld beads along the joint edges of the

22
plates. The deposition of the experimental weld metals took place in 27 cm runs with two or
three runs per layer. After the plate is completely welded, the test plate is prepared for
specimen’s extraction by machining off the excess parts from the weld.
This particular joint geometry gives very limited dilution of the weld metal and allows
accurate determination of the weld metal properties.
3.1.2 The welding pad (for chemical analysis)
The procedure used for deposition of weld metal sample for chemical analysis, consists
of building up a weld pad (Figure 3-2) by depositing several weld bead layers on the base plate,
one on top of the other to a minimum height of 16 mm. The base metal used is carbon steel of
0.2 percent carbon, the pad was welded in the flat position with multiple layers to ensure that
the effect of base metal dilution is completely removed. The slag was removed after each pass.
After welding, the top surface is machined or ground smooth to remove all foreign matter.
Figure 3-1 Specimens positioning in the test plate.

23
3.2 Sample Preparation
3.2.1 Mechanical tests specimens
The specimens are cut from the test plate of weld metal. Specimens for tensile test was
taken from the joint cross-section parallel to the welding direction. Samples of weld metal for
Charpy impact and hardness investigations were taken from the joint cross-section
perpendicular to the welding direction as shown in Figure 3-3.
Figure 3-3 Descriptive image of the position of a tensile (a); Charpy (b) specimen on the
weld joint.
Figure 3-2 Pad for chemical analysis of undiluted weld metal.

24
3.2.2 Polishing and Etching
The Charpy tests specimens are the ones used for metallographic observation. The
metallographic specimens were prepared as described below.
Polishing was done so as to obtain a mirror like surface, suitable for metallographic
examination. Polishing was carried out on a MECATECH-234 polishing machine Figure 3-4
(right). Polishing was achieved by using successively finer abrasive paper (120-450-500-800-
1200-2400-4000). When moving from a grade to another, the samples were rotated 90°. A
coolant was used during the operation to prevent rise in temperature of the samples.
Etching was carried out using a 3% Nital (97ml of ethanol and 3ml of nitric acid). The
immersion time was 5 seconds. The micrographs of the prepared samples were taken using the
metallurgical microscope shown in Figure 3-4 (left).
Figure 3-4 (left) Zeiss Axiovert 40 MAT light optical microscope & (right) MECATECH-234
Polishing machine at (LPMMM).
3.3 Chemical Analysis
Chemical analysis was performed on the welding pad, to determine the chemical
composition and the weight per cent wt% of the main elements.
The equipment used is an X-ray fluorescence spectrometer SHIMADZU Lab Center
XRF-1800 at Trefisoud Control Laboratory (Figure 3-5).

25
Figure 3-5 SHIMADZU Lab Center XRF-1800 (Trefisoud Control Laboratory).
3.4 Mechanical Investigations
3.4.1 Tensile testing
Tensile testing can be used to access several mechanical properties of the weld metal.
In this work, the specimen were deformed until fracture by increasing the tensile load uniaxially
along the axis of the specimen. The specimen was machined longitudinally from the weld
deposits. The specimen had a length of 106 mm, a diameter of 10 mm and a gauge length of
50 mm. The tensile specimen was placed in a tensile testing machine and pulled until it
fractures as shown in Figure 3-7. Elongation was measured over 60 mm. Tensile testing was
performed in compliance with standard NF A 03-151 using Zwick Roell Z250 (Figure 3-6)
machine at room temperature.

26
Figure 3-6 Zwick Roell Z250 machine (Trefisoud Control Laboratory).
Figure 3-7 Cylindrical tensile specimen after fracture with dimensions in mm.
3.4.2 Charpy impact testing
Charpy V-notch testing is used to measure the impact energy which is sometimes also
termed the notch toughness [4]. For Charpy testing, transverse specimens were machined in
the shape of a bar having dimensions 10 mm × 10 mm × 55 mm, as shown in Figure 3-8. They
were then notched in the weld metal center perpendicular to the welding direction, with a notch
depth of 2 mm and a total notch angle of 45°. Three specimens were tested at two temperatures
0° and -20°. The energy absorbed in breaking each of them is recorded. Charpy impact testing

27
was performed in compliance with standard NF A 03-161 using Charpy pendulum Heckert
type WPM at Trefisoud Control Laboratory.
Figure 3-8 Charpy V specimens after being fractured
3.4.3 Hardness testing
Hardness is a measure of the weld metal’s resistance to localized plastic deformation.
Hardness testing was conducted according to Vickers method using a 0.2 N load on joint cross-
sections polished with abrasive papers. Samples were hardness tested starting from the base
metal towards the weld metal in 1 mm steps. A total of 18 indentations were made in each
filiation. A TUKON 2500 Wilson Hardness machine (Figure 3-9) of the Laboratory of Physics
and Mechanics of Metallic Materials – Ferhat Abbas University of Setif was used in the testing.
Microhardness testing was additionally used to identify the nature of some micro
constituents in addition to the microstructures obtained.
A hardness mapping has been done to one of the prepared specimens, the hardness map
is very important to identify the mechanical properties of different developed zones in the
welding. This would be necessary to study the effect of developed microstructures during
welding on the final mechanical properties of the material [22].
Additionally, this map would be useful for evaluating the micromechanical properties
of the material [22].

28
Figure 3-9 TUKON 2500 Wilson Hardness machine at (LPMMM).
3.5 Microstructure Characterization Techniques
Optical and scanning electron microscopes were applied to evaluate the microstructure
and failure mode.
3.5.1 Optical Light Microscopy (OLM)
Optical Light Microscopy is one of the most commonly used techniques for
microstructure characterization in the development of weld metals. Steel weld metals are
opaque to visible light and as a result reflection of light from a well prepared
(polishing/etching). The image contrast is a result of variations in reflectivity from different
phases of the microstructure.
Limitations of this technique are its spacial resolution and its depth of field.
Investigations in this work was carried out using a Zeiss Axiovert 40 MAT light optical
microscope at LPMMM (Figure 3-4 Left).

29
3.5.2 Scanning electron microscopy (SEM)
Scanning electron microscopy offers possibilities for image formation that are usually
easy to interpret and will reveal clear pictures of as-polished and etched cross sections as well
as rough surfaces and particles. Microscopic examination of the fracture surface is best
accomplished by use of the scanning electron microscope, The SEM provides good depth of
focus to observe topological features of the fracture surface.
The SEM used in this work to examine the fracture surfaces was a PHILIPS ESEM
XL30 (Figure 3-10) at Laboratory of Physics and Chemistry of Materials – Mouloud
MAMMERI University of Tizi Ouzou.
Figure 3-10 PHILIPS ESEM XL30 Scanning Electron Microscopy.

30
Chapter 4 - Results and Discussion
This chapter presents the results of the mechanical tests conducted on the welded joints
of all the samples as well as the microstructural analysis of the different zones of the
weldments, followed by a discussion of the obtained results.
4.1 Tensile Test
The results obtained from the tensile test on a cylindrical test piece of 78.5mm2
cross-
sectional area are summarized in Table 1.
Table 1 Tensile test results.
Yield Point Stress Rupture Stress Strain
525.9 (N/mm2) 584.68 (N/mm2) 22 %
Rupture Stress: The Load (N) at rupture point / Cross sectional area of the specimen (mm2
).
Yield point stress: the stress at which a material begins to deform plastically.
Strain: Change in length /Gauge length.
According to these results, the weld metal shows, a high mechanical strength.
The yield strength and resistance of the weld metal deposited with the cellulosic
electrode are well above the specified minimum for class E6010 electrodes (See Appendix D
for references). However, there was noticeable reduction in the strain to failure, in comparison
with the values given by some producers. This is due to inefficiencies in the welding procedure
and the formation of metallurgical defects such as manganese sulfide inclusions which can be
crack initiation sites.

31
4.2 Charpy impact
The impact test results are shown in Table 2.
Table 2 Impact tests results
Specimen Notch Temperature Energy (J) Mean Value Reference
01
Type V
2 mm
0°C
101
96.66 ≥ 4702 95
03 94
04
-20°C
72
61.33 ≥ 2805 63
06 49
We can see that the two mean values for each temperature are greater than the reference
values which indicates that the impact failure bearing of the weld metal is very satisfactory.
The average energy absorbed in impact tests was 96.66J at 0°c and 61.33J at -20°c.
These results are significantly better than the expected (see Reference at Table 2) for a weld
metal produced by E6010 cellulosic electrodes.
We have also noticed a big difference between the energies of the two temperature tests
which is confirmed by the fractography examinations of the two fracture surfaces, which will
be detailed in section 4.5 below.
4.3 Chemical composition
The chemical composition of the weld metal is presented in Table 3.
Table 3 Elemental composition of the weld pad using XRF analysis.
C% Mn% Si% N% S% Ni% Mo% Cu%
0.085 0.579 0.142 0.014 0.013 0.066 0.018 0.128

32
The material is a low carbon high manganese C-Mn-Si high strength steel weld metal.
It can be observed by analyzing the results presented in Table 3 that the chemical
composition of weld metal deposited with electrodes are inside the limits specified for Class
E6010 electrodes. (Check Appendix D for references of “Cellulosic Electrodes Specifications
Sheets” of different international companies.
4.4 Hardness Tests
Hardness values are given in Figure 4-1 and Table 4. It is observed that hardness mean
values of FZ and BM are about 347 HV and 238 HV, respectively, and hardness values of HAZ
vary from 293 HV to 238 HV.
Figure 4-1 Hardness filiation results.
Hardness results give an indication on the microstructure to be obtained. The hardness
curve consists of three main regions. The first one (in blue) corresponds to the fusion zone, and
is the hardest of the three (mean value of 347 HV). The second one (in red) has a linearly
decreasing hardness, the highest value being adjacent to the fusion zone and the lowest value
adjacent to the base metal, and corresponds to the heat affected zone. This behavior can be
explained by the multitude of its microstructures. The third one (in green) has the lowest
hardness (mean value of 238 HV) and corresponds to the base metal.

33
Table 4 Results of the hardness filiation carried out along the length of the prepared samples.
Point 01 02 03 04 05 06 07 08 09
Distance (mm) 00 01 02 03 04 05 06 07 08
HV 337 358 342 332 347 363 347 353 342
Point 10 11 12 13 14 15 16 17 18
Distance (mm) 09 10 11 12 13 14 15 16 17
HV 293 253 232 238 250 244 216 234 251
Hardness map obtained from the three zones of the joint is depicted in Figure 4-2.
Inhomogeneity in hardness can be related to microstructure of different zones. The interesting
feature which stands from the mapping is the interpenetration of part of the heat affect structure
into the weld structure or vise versa. This feature can be explained by the influence of the FZ
on the HAZ, thus indicating the existence of a temperature gradient decreasing from the molten
pool towards the base metal.
Figure 4-2 Hardness map of the studied weld joint specimen with a real photo.

34
Vickers hardness measurements in two distinct phases of the weld metal indicate the
existence of proeutectoid ferrite (bright, 274 HV) and pearlite (dark, 381 HV), as confirmed
by the micrograph of Figure 4-3.
Figure 4-3 Indentations in two different regions of the weld metal. (Bright region: ferrite,
dark region: pearlite).
4.5 Metallographic Examinations
The microstructure of weld metal plays an important role on its proprieties. However,
recognizing every constituent of the microstructure is far from being evident due to
resemblance of some phases. Figure 4-4 shows the microstructures of the different zones of the
welded joint. An investigation of the weld joint was carried out using optical and electron
microscopy.

35
Figure 4-4 Optical micrographs showing the different microstructures of the weld joint with
respect to a typical macrograph.
The results of LOM observations of the weld microstructures are shown in Figure 4-4.
Three different zones of microstructure are observed:
A Fusion Zone (FZ), which melts and re-solidifies during the welding process. A Heat
Affected Zone (HAZ), which does not melt but undergoes microstructural changes, and the
Base Metal (BM) which does not experience any microstructural changes.
- The base metal microstructure (a) is a cold rolled ferrito-pearlitic structure
corresponding to a 0.2% Carbon steel as given in the technical sheet provided by the
manufacturer of the material.
The results showed that the initial microstructures consisted of around 75% ferrite and
25% perlite.
- The HAZ zone presents a more complex microstructure (c1, c2, c3), as depicted in
Figure 4-4. This can be related to the thermal and cooling regimes of these parts of the
zone during welding.

36
Micrograph (c1) is situated at the interface adjacent to the FZ. Its structure is bainitic
and has a hardness of 300-350 HV (see the hardness mapping of Figure 4-2).
Micrograph (c2) represents a region in the middle of the HAZ. It shows partial grain
refinement of a recrystallized ferrito-perlitic structure, as well as globular cementite.
Micrograph (c3) represents a partially recrystallized hypo-eutectoid structure.
- Micrographs (b1 & b2) of the Fusion Zone show a typical cast structure (ferrite +
pearlite) with the grains in the (b1) region being finer than in (b2).
Figure 4-5 SEM micrographs for the three main zones of the weld joint.
The SEM examination shows one micrograph from each zone (Figure 4-5). It
corresponds well to the optical micrographs.

37
Figure 4-6 Fractographs of the ruptured surfaces for the broken Charpy v specimens
For the Charpy tested specimen at 0°C, the SEM fractograph (Figure 4-6-a) represent
ductile fracture surface due to dimples created around spherical particles, as indicated by the
red arrow on the fractograph.
For the specimen tested at -20°C, the SEM fractograph (Figure 4-6-b) shows a cleavage
type brittle fracture. This has already been mentioned in section 4.1. It can therefore be
concluded that the temperature of -20°C belongs to the ductile-brittle transition range.

38
Chapter 5 - Conclusion
- A weld joint plate and a weld pad, made in Trefisoud factory, were studied to evaluate
the characteristics of the weld metal for the new cellulosic electrode fabricated by the
same factory.
- A chemical analysis was done on the welding pad in order to determine the weld
chemical composition.
- Cross-sectional samples of the welded joints were polished, etched and observed under
optical and electronic microscopes in order to reveal their microstructures.
- A specimen was used for the tensile test, with the gauge positioned at the center of the
weld area and parallel to the welding direction.
- Charpy V-notched bar impact tests were performed in a Charpy pendulum machine, at
two distinct temperatures: 0°C and -20°C.
- Vickers hardness measurements were taken along the length of the specimen. The
results are presented in the form of filiation and mapping.
- SEM Fractography analyses were conducted to determine the fracture modes and
mechanisms.
The results show that:
- The composition of weld metal deposited with the cellulosic electrodes is within the
limits specified for class E6010 electrodes.
- Different microstructures of various sites has been revealed and identified.
- Mechanical properties of the weld metal deposited by the newly produced electrode
were satisfactory when compared to the minimum requirements for the class E6010
electrodes.
- Fracture surface SEM analyses of the broken Charpy v specimens show a ductile
fracture surface at 0°C, and a brittle fracture surface at the temperature -20°C.
- Hardness filiation and mapping diagrams are consistent with the microstructures
obtained.

39
References
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Ambik Press, Benin City. pp 505-509.
[2] Khurmi, R.S. & Gupta, J.K. (2005). A textbook of machine design, Second Edition,
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[3] Armentani, E. Esposito, R. & Sepe, R. (2007). The effects of thermal properties and
weld efficiency on residual stresses in welding. The journal of achievements in
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[4] Mikell P, Groover. (2013). Fundamentals of Modern Manufacturing. Materials,
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[5] Leonard P, Connor. (1976). Welding Handbook, Vol 1, Fundamentals of Welding,
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[6] Ramesh, S. (2016). Applied Welding Engineering. Processes, Codes, and Standards,
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[7] Serope, K. & Steven R, S. (2014). Manufacturing Engineering and Technology,
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[8] Hwaiyu, G. (2004). Manufacturing Engineering Handbook, McGraw-Hill Inc, Chapter
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[9] Asm International Staff. (1993). Asm Handbook, Vol 6, Welding, Brazing, And
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[10] Lincoln Electric. (2006). The Procedure Handbook of Arc Welding, Revised Third
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[11] Jain, R.K. (2008). Production technology, Sixteenth Edition, Khanna publishers. New
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[12] Davies, A.C. (1972). Science and Practice of Welding, Seventh Edition, Cambridge
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[13] Jackson, C.E. (1973). Fluxes and slags in welding, welding research bulletins, no190
[14] Davies, A.C. (1972). Science and Practice of Welding, Seventh Edition, Cambridge
University press, London. pp 55.
[15] http://mechanicalinventions.blogspot.com (Retrieved 25th
May 2017 at 14:05).
[16] Weaver, R. & Ogborn, J. (2005). Cellulosic Covered Electrode Storage Conditions -
Influence on Welding Performance and Weld Properties. The Lincoln Electric
Company. Cleveland, Ohio, USA.

40
[17] Olawale, A. (2014). Production and Weld Joint Performance Evaluation of Arc
Welding Electrodes from Dana Rolling Mill Scales, Ahmadu Bello University, Zaria.
NIGERIA.
[18] Houldcroft, J. & John, R. (2001). Welding and cutting, Woodhead Publishing Limited,
pp 99-103.
[19] American Society for Metals. (1985). Metallography of Weldments, Metals Handbook,
Vol9, Ninth Edition, American Society for Metals, pp 577-586
[20] Radhakrishnan, V.M. (2005). Welding Technology and Design, Second Edition, New
Age Publishers, U.S, pp 105-147.
[21] American Society for Metals. (1985). Mechanical Testing, Metals Handbook, Vol9,
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[22] Ramazani, A. Mukherjee. K, Abdurakhmanov, A. Abbasi, M. (2015).
Characterization of Microstructure and Mechanical Properties of Resistance Spot
Welded DP600 Steel. Metals 5, no. 3, pp1704-1716.

41
Appendix A - Master chart of welding and allied processes

42
Appendix B - Principal welding process.

43
Appendix C - Electrodes production process flow chart

44
Appendix D - Cellulosic Electrodes Specifications Sheets
1 - WELDCOTE METALS

:‫الملخص‬
‫تحديد‬ ‫في‬ ‫بارز‬ ‫دور‬ ‫ولتقييمه‬ ،‫الصناعي‬ ‫المجال‬ ‫في‬ ‫التجميع‬ ‫تقنيات‬ ‫اهم‬ ‫من‬ ‫التلحيم‬ ‫يعتبر‬‫الخصائص‬‫لوصلة‬ ‫النهائية‬
‫المودعة‬ ‫المعدنية‬ ‫اللحام‬ ‫لوصالت‬ ‫والميكانيكية‬ ‫المجهرية‬ ‫الخصائص‬ ‫دراسة‬ ‫تمت‬ ،‫العمل‬ ‫هذا‬ ‫في‬ ‫لذلك‬ ،‫اللحام‬
‫تريفيسود‬ ‫مصنع‬ ‫طرف‬ ‫من‬ ‫المنتجة‬ ‫السيليلوزية‬ ‫التلحيم‬ ‫قضبان‬ ‫بواسطة‬–.‫العلمة‬
‫عليها‬ ‫والتعرف‬ ‫معاينتها‬ ‫تمت‬ ‫متنوعة‬ ‫بمناطق‬ ‫مختلفة‬ ‫مجهرية‬ ‫بنيات‬‫تم‬ ،‫واإللكتروني‬ ‫الضوئي‬ ‫المجهر‬ ‫بإستخدام‬
.‫الصالدة‬ ‫اختبار‬ ‫وكذالك‬ ،‫اإلصدام‬ ،‫الشد‬ ‫خالل‬ ‫من‬ ‫للوصالت‬ ‫الميكانيكية‬ ‫الخواص‬ ‫فحص‬‫اال‬ ‫مطياف‬ ‫استخدام‬ ‫تم‬‫ش‬‫عة‬
‫صور‬ ‫اخذت‬ ‫كما‬ ،‫للحام‬ ‫الكيميائية‬ ‫التركيبات‬ ‫لتحديد‬ ‫السينية‬‫ال‬ ‫وآليات‬ ‫طرق‬ ‫لتحديد‬ ‫الماسح‬ ‫اإللكتروني‬ ‫بالمجهر‬.‫كسر‬
Abstract
Welding is the most important joining technique in the industry, and its evaluation plays a
prominent role in determining the final properties of the joints. Therefore, in the current work,
the microstructure and mechanical properties of a weld metal joints deposited with Trefisoud
cellulosic electrodes was investigated. Different microstructures of various sites were observed
and identified using optical and electron microscopy. Mechanical properties of the weldments
were investigated through tensile, Charpy V as well as hardness testing. XRF spectrometry was
used to determine the chemical compositions of the weld. SEM fractography was conducted to
determine the fracture modes and mechanisms.
Copyright
© Mathil Habchi 2017.
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Mechanical and Microstructural Characterization of Weld Joints Obtained with Cellulosic Electrodes Fabricated by TREFISOUD El-EULMA

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Mechanical and Microstructural Characterization of Weld Joints Obtained with Cellulosic Electrodes Fabricated by TREFISOUD El-EULMA