Gas Welding process

Gas welding Process

Gas welding is a fusion welding process, in which the desired heat is obtained by mixing oxygen with flammable gas, following types of flammable gases are used in this process.

Two familiar fuel gases are used in gas welding, which most popular welding process in the gas welding process.

  • the mixture of oxygen and acetylene gas using in Air- acetylene welding.
  • the mixture of oxygen and hydrogen gas using in the oxy-hydrogen welding.

We may classify gas welding into four parts

  • Air-acetylene Welding
  • Oxyhydrogen welding
  • Oxyacetylene welding,
  • Pressure gas welding



In this process, acetylene is mixed with oxygen in a certain proportion in a welding torch and ignited, then the metal in the flame at the tip of the torch is melted and mixed into the parent metal.

In this process, the temperature of the acetylene flame reaches about 3200-degree centigrade, which is sufficient to melt the metal.

Oxy-hydrogen gas welding

Hydrogen is used in place of acetylene in the oxy-hydrogen process, which has a lower temperature than that required for oxy-acetylene, which is about 2500 ° C.

In other gas welding process, flame temperatures with oxygen mixture, given bellow:

Oxygen with acetylene 3200

Oxygen with hydrogen 2500

Oxygen with propane 2500

Gas welding Equipment

The basic types of equipment used to carry out gas welding are as follows:
1- Oxygen gas cylinder
2- Acetylene gas cylinder 3- Oxygen pressure regulator 4- Acetylene pressure regulator 5- Oxygen gas.


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Shielding gases     


pressure regulator     

Acetylene cylinder 

Types of equipment   





Type of flames

The correct type of flame is essential in the gas welding process.

Flames can be classified as follows:

  1. Acetylene flame
  2. Reducing flame
  3. Neutral flame
  4. Oxidising flame
gas welding

Neutral Flame

A neutral flame is produced when approximately equal (1.1: 1) volumes of oxygen and acetylene are mixed into the welding torch and fired at the tip of the flashlight. Neutral flame temperatures are of the order of about 3260 degrees centigrade.

A neutral flame is applied in the welding of stainless steel, mild steel, cast iron aluminium and coper

Oxidising flame

The oxidizing flame is the second stage of the neutral flame. After established the neutral flame, the oxygen supply ration is increased and the oxidizing flame is established.This flame is identified by a small white cone, which is smaller, more blue in color and higher than a neutral flame.

The oxidizing flame is applied in the welding of Zinc base metals, copper base metals, and some types of ferrous metals like cast iron

Reducing Flame

The reducing flame is established when the amount of oxygen supplied is reduced by the neutral flame. This can be identified by the acetylene feather, which is present between the inner core and the outer envelope. The outer flame envelope is longer as compared to the neutral flame and is generally brighter in color. The temperature of the reducing flame is about 3038 degrees centigrade.

Acetylene flame

As we know that the maximum temperature of the oxyacetylene flame is 3100 to 3300 degrees centigrade and the center of the heat concentration is just off the extreme tip of the white cone.