Welding basic knowledge

1. Basics Of Welding

2. Welding
• Welding is a process of
joining metals
* With the application
of heat,
*With or without the
application of pressure,
* With or without the
application of filler
metal to form a
metallurgical joint.

3. Types of Welding
Fusion
• SMAW
• Gas / Brazing
• TIG
• GMAW(MIG/MAG)
• FCAW
• SAW
Non-Fusion
• Forge Welding
• Resistance Welding
• Thermal Spraying
• Electron beam welding.
• Laser beam welding.
• Soldering

4. Types of Joints
• There are 5 types of
joints …

5. Fillet and Groove Welds
• Groove and fillet welds can be made on many
types of joints

6. Parts of a Weld
Joint and Weld
Heat Affected Zone

7. What are Welding Positions?
• There are various positions that a weld can be
made in:

8. Why is Welding Important?
• Many things around us are welded …
– Pipelines that bring fresh water
– Towers that carry electricity to houses
– Cars and buses that take people where they need
to go

9. Can All Metals Be Welded?
• Most metals can be welded, but not all
• The three most common weldable metals include:
– Mild Steel - inexpensive and strong
– Stainless Steel – does not rust
– Aluminum – does not rust and is light weight
Mild steel Stainless Steel Aluminum

10. Arc Welding

11. What is Arc Welding?
• Arc welding is most commonly used to join two
pieces of metal
– The welder creates an electric arc that melts the base
metals and filler metal (consumable) together so that they
all fuse into one solid piece of metal
Steel Pipe – Tack
Welded
Root Pass or
“Stringer Bead”
Final weld after
several beads are
made

12. Basic Steps of Arc Welding
• Prepare the base materials: remove paint and rust
• Choose the right welding process
• Choose the right filler material
• Assess and comply with safety requirements
• Use proper welding techniques and be sure to protect
the molten puddle from contaminants in the air
• Inspect the weld

13. The Arc Welding Circuit
• The electricity flows
from the power source,
through the electrode
and across the arc,
through the base
material to the work
lead and back to the
power source

14. Basic Electricity
• Voltage – The electrical
potential or pressure that
causes current to flow
– Measured in Volts
• Current – The movement
of charged particles in a
specific direction
– Measured in Amps
• Polarity
– DC- (Direct Current
Electrode Negative)
– DC+ (Direct Current
Electrode Positive)
– AC (Alternating Current)
DC+
DC -
AC

15. Striking an Arc
• To begin the SMAW Process, you must first strike
an arc. This can be done using one of the
following techniques:
– Scratch start – scratch the electrode on the base
metal like a match
– Tap Start – tap the rod against the base metal

16. Work Angle
• The work angle is the
angle between the
electrode and the work
as depicted on the left
• Work angles can vary
depending on the
position the weld is
being made in
90°

17. Travel Angle
• Also commonly called
Lead Angle
• The travel (lead) angle
is the angle between
the electrode and the
plane perpendicular to
the weld axis
20-30°

18. Arc Length
• After striking the arc, maintain a 1/8” distance
between the electrode and the workpiece
– If the arc length becomes too short, the electrode will get
stuck to the workpiece or ‘short out’
– If the arc length becomes too long; spatter, undercut, and
porosity can occur
Arc Length = 1/8”

19. Travel Speed
• The travel speed is the
speed at which the
electrode moves along the
base material while
welding
– Too fast of a travel speed
results in a ropey or convex
weld
– Too slow of a travel speed
results in a wide weld with
an excessive metal deposit
The travel speed impacts the
shape of the bead.
End of Weld

20. E70XX
Electrode
Tensile in Psi
Welding Position:
1 = All Position, 2 = Flat & Horizontal
Type of Current and Coating
AWS Classification
of SMAW Electrodes

22. WEAR
“LOSS OF MATERIAL” CAUSED IN AN
ENGINEERING SYSYEM.

23. TYPES OF WEAR
PRIMARY
• FRICTION
• ABRASION
• IMPACT
SECONDARY
• CAVITAION
• CORROSION
• HEAT
• EROSION

24. FRICTION
• FRICTIONAL WEAR IS CAUSED BY MOVEMENT
OF ONE METALLIC SURFACE OVER THE OTHER
CAUSING LOCALISED MATERIAL LOSS.
• NO ABRASIVE MATERILA IS INVOLVED.
• EXAMPLES : SHAFT JOURNALS, BEARINGS

25. ABRASION
• LOSS OF MATERIAL FROM A
PART CAUSED BY THE ACTION
OF HARD FOREIGN MATERIAL
IN MOTION OR UNDER LOAD.
Ex :Raw Mill roller, Chutes etc

26. TYPES OF ABRASION
• GOUGING : Large coarse abrasives strike the surface and
remove large amount of material.
Ex: Chutes.
• HIGH STRESS : Wear caused by crushing of abrasive
material between metal parts. High stress abrasion.
Ex: Grinding rollers..
• LOW STRESS: Small abrasive parfticles move rapidly over
the part. Low stress abrasion.
Ex : I D Fans.

27. IMPACT
• WEAR DUE TO IMPACT IS THE RESULT OF
SUCCESSIVE SHOCK LOADS CAUSED BY AN
OBJECT STRIKING AGAINST AN OTHER AND
CAUSING LOCALISED COMPRESSION,
DEFORMATION, CRACKING, FLAKING OR
FATIGUE.
• Ex: Impactor arms, hammer crusher.

28. EROSION
• WEAR CAUSED BY FINE ABRASIVES CARRIED IN
A HIGH VELOCITY FLUID STREAM
• Ex: Pumps, ID Fans

29. HEAT
DEGRADATION MODES
• WARPAGE/DISTORTION
• MATERIAL SOFTENING
• MATERIAL EMBRITTLEMENT
• OXIDATION/SCALING
• THERMAL CRACKING
• THERMAL SHOCK
• THERMAL FATIGUE
Ex: Cooler plates in Cement Kiln.

30. CORROSION
• RESULT OF CHEMICAL OR ELECTROCHEMICAL
ACTION OF ENVIRONMENT ON THE BASE
METAL.
Ex: Pumps, Valves, Screw Conveyors

31. ELECTRODE
-
WORK PIECE
+
+
-
PENETRATION
CONCENTRATION OF HEAT
MORE AT ELECTRODE
SHALLOW PENETRATION
LESS DISTORTION
MORE HEAT GENERATED AT
WORK PIECE
DEEPER PENETRATION
CLEANSING ACTION ON
WORK PIECE
Selection of Polarity

33. BRASS Vs BRONZE
BRASS BRONZE
ALLOY ZINC & COPPER ALLOY TIN & COPPER
MALLEABLE HARD & BRITTLE
USED UNDER STRESS CORROSION
RESISTANT
GOLDEN COPPER