Gas welding involves burning a combustible gas like acetylene or hydrogen with oxygen to heat and melt metals for joining. Oxy-acetylene welding uses oxygen and acetylene gases to produce a flame reaching 3000-3500°C, melting a filler material and parent metals to join workpieces. Equipment includes gas cylinders, regulators, welding torches, and non-return valves. It has advantages of low cost, ability to weld various metals, and adjustable flame intensity, but disadvantages of lower temperature than arc welding and lack of flux shielding.

1. GAS WELDING
Gas welding is done by burning a combustible gas with Air
or oxygen .
Purpose of flame is to heat and melt the parent metal
and filler rod of a joint
Eg. Oxygen +Acetylene
Oxygen +hydrogen
Oxygen+ other fuel

2. Oxy –Acetylene welding
• Oxy Acetylene Welding is a type of Gas Welding Process that is used
to join the metals.
•Working Principle
• The working principle of Oxy Acetylene Welding is simple in the
process.. It uses the Fuel gases like Oxygen and Acetylene to weld the
material
• The temperature of the flame is about 3000 to 3,500
degrees centigrade.
• In this process, the welding torch produces the high-
temperature flame with the help of oxygen and acetylene. Due to
the high temperature parent and filler metal melts.
• A filler material is used to fill the gaps between two workpieces. As
the filler is cooled, the two workpieces will be joined.

3. Oxy Acetylene Welding Equipment

5. • Gas Cylinders: In the Gas Cylinders, the gases like Oxygen and Acetylene
are stored at high pressure whenever the welding needs to be done,
the gas is released manually.
• Regulator: A Regulator is a fixed part of the Cylinder; it is used to stop
or slow down the pressure of the gas that is used to weld.
• Welding Torch: A Welding Torch is the main component in the oxy
acetylene equipment where the flame is produced and used to weld . A
welding torch produces a high-temperature flame according to the
welding material.
• Non-Return Valve: Non-Return Valve is a type of valve that ensures the
flow of gas is in one direction.

6. Advantages Oxy Acetylene Welding
• It is simple in construction and easy to operate
• Not only for welding but also oxy acetylene is used to separate
or cut the materials into pieces.
• This type of Welding is cheaper.
• It can be used to weld ferrous and even non-
ferrous metals.
• The intensity of the flame can be adjusted to high and less by
using the valve.
• It can be used for high melting metals and even for low melting
metals.

7. Disadvantages of Oxy Acetylene Welding
• The temperature of the flame is less when compared to
the arc welding.
• As like arc welding, the oxy acetylene does not have
a high flux shield over the weld.
• It is suitable for thin materials and medium thin
materials whereas it is not suitable for thick materials.

9. Arc welding

11. Electric arc welding
 Most extensively used
 Source of heat is Electric arc
 Current flows through ionized particles (plasma)
 Two types of electrodes – (Consumable and non-consumable)
 In case of non consumable electrode extra filler material is used
to generate pool of liquid

12. Fluxes
An electode has metal core surrounded by flux
coating
• Provide shielding to the metal pool from
atmosphere
• Forms slag by mixing with impurities
• Slag being lighter floats on the surface of the pool
(uniform cooling and no oxidation)
• Provide alloying element

13. Equipments
• AC or DC (transformer /Generator) (low voltage and high ampere)
(10-50 volt and 50 -300 A)
• Electrode (Bare /coated electrode)
• Elecrode holder , welding helmet ,hand gloves

14. Types of joint
 Lap joint- overlapping of plates
(single transverse and double transverse)
 Butt joint –welding ends or edges of two plates
 Corner joint- surfaces are at 90 degree
 Edge joint- joining two parallel plates

15. Common defects in welding