TYPES OF OXY-ACETYLENE FLAMES

The oxy-acetylene gas flame has following features which make it useful for gas welding:

·      It has a well controlled flame with high temperature.  

·      The flame can be easily manipulated for proper melting of the base metal

·      It does not change the chemical composition of the base metal/ weld.

Three different types of oxy-acetylene flames as given below can be set:  

Neutral flame

·         Oxidising flame

·         Carburizing flame

Neutral Flame

Oxygen and acetylene are mixed in equal proportion in the blowpipe and complete combustion takes place in this flame. This flame does not have a bad effect on the metal/ weld i.e. the metal is not oxidized and no carbon is available for reacting with the metal. It is used to weld most of the common metals, i.e. mild steel, cast iron, stainless steel, copper and aluminium.

Oxidizing Flame

It contains an excess of oxygen over acetylene as the gases come out of the nozzle. The flame has an oxidizing effect on metals which prevents evaporation of zinc/ tin in brass welding/ brazing. It is used for welding of brass and for brazing of ferrous metals.

Carburizing Flame

It receives an excess of acetylene over oxygen from the blowpipe. The flame has a carburizing effect on steel, causing hard, brittle and weak weld.

The selection of the flame is based on the metal to be welded.

The neutral flame is the most commonly used flame. Metals and flame to be used are as given below:

·      Mild steel (Neutral)

·  Copper (de-oxidized) (Neutral)

·  Brass (Oxidizing)

·  Cast iron (Neutral)

·  Stainless steel (Neutral)

·  Aluminium (pure) (Neutral)

·  Stellite (Carburizing)