The document presents an overview of gas welding, specifically oxyacetylene welding, as a method for joining metals through heating with a flame from fuel gas and oxygen. It describes the process, types of gas welding, equipment used, and the advantages and disadvantages of this welding technique. The importance of flux and the chemical reactions involved in the process are also highlighted.

1. Seminar On
GAS WELDING
AND CUTTING
Melwin D’mello
M.E (Welding Engineering)
Centre for Materials Joining & Research (CEMAJOR),
Department of Manufacturing Engineering,
ANNAMALAI UNIVERSITY
Presented by

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.

3. Types of Welding

4. Gas Welding
• Gas welding is a welding process that melts and joins metals by
heating them with a flame caused by a reaction of fuel gas and
oxygen.
• The most commonly used method is Oxyacetylene welding
due to its high flame temperature.
• The flux may be used to deoxidize and cleanse the weld metal.
• The flux melts, solidifies and forms a slag skin on the resultant
weld metal.

5. Continued....
• Utilizes oxygen and a fuel gas to heat metal until it is in a
molten state and fuse multiple pieces of metal together.
Can be used with or without a filler rod.
• Great for joining dissimilar metals together.
• Older technology that can be replaced by GTAW

6. Oxyacetylene Welding
• Also known as “oxyacetylene welding”
• Uses an oxyfuel gas flame
• Can be applied with or without pressure
• Can be applied with or without the use of filler
materials

7. Gas Welding
• Oxy-acetylene Welding:
CaC2 + 2H2O = Ca (OH) 2 + C2H2
C2H2+2.5O2= 2CO2+H2O(vapour)+ 306.800 cal /mol

8. 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.

9. Chemical reactions and temperature
distribution in a neutral oxyacetylene
The secondary combustion is also called the protection envelope since CO and
H2 here consume the O2 entering from surrounding air, thereby protecting the
weld from oxidation.

10. The Oxy-acetylene welding Flame
The oxy-acetylene flame has two distinct zones.
The inner zone (Primary combustion Zone) is the hottest part
of the flame. The welding should be performed so as the point
of the inner zone should be just above the joint edges.
C2H2 + O2 2CO + H2
Primary Combustion zone

11. The outer zone the secondary combustion envelope performs
two functions
•Preheats the joint edges
•Prevents oxidation by using some of the surrounding oxygen
from weld pool for combustion and gives off carbon dioxide
and water vapour
CO + H2 + O2 CO2 +H2O
Secondary Combustion zone

12. 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

13. Oxyacetylene Welding
Uses a high-temperature flame from the
combustion of acetylene and oxygen

14. Oxyacetylene
welding
(a) overall process
(b) welding area.
Gas Welding

15. GAS WELDING
• Sound weld is obtained by selecting proper size of flame, filler
material and method of moving torch
• The temperature generated during the process is 33000c
• When the metal is fused, oxygen from the atmosphere and
the torch combines with molten metal and forms oxides,
results defective weld
• Fluxes are added to the welded metal to remove oxides
• Common fluxes used are made of sodium, potassium. Lithium
and borax.
• Flux can be applied as paste, powder,liquid.solid coating or gas.

16. The Oxy-acetylene welding Flame
Oxidizing
Excess oxygen (1.5:1)
(Brasses, Bronzes, copper)
Neutral
Equal acetylene & oxygen
(low carbon steel, mild
steels).
Reducing or Carburizing
Excess acetylene (0.9:1)
(Alloy steels and
aluminium alloys)
Inner Cone
Secondary Combustion
envelope
Acetylene feather
Max. Temp.
Zone

17. Types of Gas Welding
1. Leftward Welding
2. Rightward Welding

18. Gas welding two types

19. Gas welding equipments
1. Gas Cylinders
Pressure
• Oxygen – 125 kg/cm2
• Acetylene – 16 kg/cm2
2. Regulators
• Working pressure of oxygen 1 kg/cm2
• Working pressure of acetylene 0.15 kg/cm2
• Working pressure varies depending upon the thickness of the work
pieces welded.
3. Pressure Gauges
4. Hoses
5. Welding torch
6. Non return valve

21. Gas welding Apparatus
1. Oxygen cylinder
2. Acetylene cylinder
3. Pressure gauges
4. Valves
5. Hose pipes
6. Torch
7. Welding tip
8. Pressure regulators
9. Lighter
10. Goggles

22. Gas welding torch

24. Gas Welding - Advantages
• Simple equipment
• Portable
• Inexpensive
• Easy for maintenance and repair

25. Gas Welding - Disadvantages
• Very low welding speed
• High total heat input per unit length
• Large heat affected zone
• Severe distortion
• Not recommended for welding reactive metals such
as titanium and zirconium.

26. References
• Text Book : “Welding Process and Technology” by Dr. R.S
Parmar, 2015 edition.
• Text Book : “Welding Engineering and Technology” by Dr. R.S
Parmar, 2015 edition

27. THANK
YOU