Overview

Gas welding is one of the oldest methods of welding and, for many years, was the most widely used method of metal-melting; however, its use is a lot less common today. Nevertheless, it is a versatile method, using simple and relatively cheap equipment. It is suitable for repair and erection work, for welding pipes/tubes and structures with a wall thickness of 0.5 6 mm in materials particularly prone to cracking, such as cast iron and non-ferrous metals. It is also widely used for cladding and hardfacing. The heat is generated by the combustion of acetylene in oxygen, which gives a flame temperature of about 3100 C. This is lower than the temperature of an electric arc, and the heat is also less concentrated. The flame is directed onto the surfaces of the joint, which melt, after which filler material can be added as necessary. The melt pool is protected from air by the reducing zone and the outer zone of the flame. The flame should therefore be removed slowly when the weld is completed.

The less concentrated flame results in slower cooling, which is an advantage when welding steels that have a tendency to harden, although it does make the method relatively slow, with higher heat input and the added risk of thermal stresses and distortion.

In addition to welding, gas flames are also often used for cutting, and are very useful for heating and flame straightening.

2.1 Equipment

A set of equipment (Figure 2.1) consists essentially of gas bottles,...