1. Welding Processes
Gautam singh (M.E 4th yr)

2. WELDING
Welding is a materials joining process which produces coalescence of materials by heating them to suitable temperatures with or without the application of pressure or by the application of pressure alone, and with or without the use of filler material.
Welding is used for making permanent joints.
It is used in the manufacture of automobile bodies, aircraft frames, railway wagons, machine frames, structural works, tanks, furniture, boilers, general repair work and ship building.

3. Types of Welding Fusion Welding Pressure Welding Friction Welding
Homogeneous
Heterogeneous
Brazing
Soldering
Gas Welding
Electroslag
MIG
TIG
High Energy Beam
Shielded Metal Arc – “Stick”
Electric Arc

4. Fusion Welding Principles
Base metal is melted
Filler metal may be added
Heat is supplied by various means
Oxyacetylene gas
Electric Arc
Plasma Arc
Laser

5. Fusion Welding ELECTRODE COATING CORE WIRE WELDING ATMOSPHERE
ARC STREAM
ARC POOL
SOLIDIFIED SLAG
PENETRATION DEPTH
WELD
BASE METAL

6. Weld Fluxes Typical fluxes SiO2, TiO2, FeO, MgO, Al2O3
Produces a gaseous shield to prevent contamination
Act as scavengers to reduce oxides
Add alloying elements to the weld
Influence shape of weld bead during solidification

7. Inert Gases Argon, helium, nitrogen, and carbon dioxide
Form a protective envelope around the weld area
Used in
MIG
TIG
Shield Metal Arc

8. Types of Fusion Welding
Oxyacetylene Cutting/Welding
Shielded Metal Arc (“Stick”)
Metal Inert Gas (MIG)
Tungsten Inert Gas (TIG)

9. Oxyacetylene Welding
Flame formed by burning a mix of acetylene (C2H2) and oxygen
Fusion of metal is achieved by passing the inner cone of the flame over the metal
Oxyacetylene can also be used for cutting metals
TORCH TIP
2300 deg F
Inner Cone: deg F
Combustion Envelope 3800 deg F

10. Gas Welding (Oxy-acetylene)
A number of welding processes use a flame produced by burning a mixture of fuel gas and oxygen. The gas usually used is Acetylene but other gases are also used.
Separate cylinders and a hose pipe from each cylinder transports the gases to a torch.
Gas and fuel mix in the torch
3100°C.

11. Metal Inert Gas (MIG)
Uses a consumable electrode (filler wire made of the base metal)
Inert gas is typically Argon
DRIVE WHEELS
CONSUMABLE ELECTRODE
POWER SOURCE
SHIELDING GAS
ARC COLUMN
BASE METAL
PUDDLE

12. Tungsten Inert Gas (MIG)
Tungsten electrode acts as a cathode
A plasma is produced between the tungsten cathode and the base metal which heats the base metal to its melting point
Filler metal can be added to the weld pool
TUNGSTEN ELECTRODE
(CATHODE)
POWER SOURCE
TUNGSTEN ELECTRODE
+ +
+ +
- - -
SHIELDING GAS
ARC COLUMN
BASE METAL
PUDDLE
BASE METAL (ANODE)

13. Submerged Arc Welding (SAW)
Similar to MIG welding, SAW involves formation of an arc between a continuously-fed bare wire electrode and the workpiece
Applications
SAW welding taking place in the flat position. Ideal for heavy workpieces
Carbon-manganese steels,low alloy steels and stainless steels

14. Welding Positions FLAT HORIZONTAL OVERHEAD VERTICAL
INCREASING DIFFICULTY
FLAT
HORIZONTAL
OVERHEAD
VERTICAL

15. Weld Symbols (Butt Joints)
Backing

16. Weld Symbol (Fillet Joints)

17. Weld Symbol (Corner Joints)