Today we will discuss types of welding flames.
There are mainly three types of flames used in welding, they are:-
1) Natural Flame or Neutral Flame:-
It is called natural flame because when we do welding with this flame no chemical reaction takes place. Also, this flame produces very little smoke.
Neutral flame has equal oxygen and gas fuel by volume. It gets an additional amount of oxygen from the air and provides complete combustion.
In this flame, there are two cones, they are:-
1) The first one is called the inner cone which is white in colour.
2) The second one is called the outer cone which is blue in colour.
The temperature of the inner cone is nearly 3100°C – 3400 °C and the temperature of the outer cone is nearly 1200°C – 1300°C.
Neutral flame is used for most welding operation and also for preheating during cutting operations. When steel is welded using neutral flame, the molten metal flows easily without foaming, sparking or boiling and the metal puddle is quiet and clear.
This flame has an equal amount of oxygen and gases fuel by volume.
It is used to weld mild steel, stainless steel, cast iron, copper, aluminium etc.
2) Carburizing Flame:-
This flame is called carburizing because when this flame is used in welding then metal carbide is formed. If a metal that absorbs carbon is welded using this flame then the properties of the metal will be changed.
This flame is more smoky and quiet. In this flame more fuel gas is used as compared to oxygen. Thre ratio of fuel gas to oxygen in this flame is 3:2.
Carburizing Flame has three cones or zones,they are:-
1) First one is called inner cone and is white in colour.
2) The intermediate one is called acetylene feather and is red in colour.
3) The last one is called outer cone and is blue in colour.
The intermediate cone is called acetylene feather because the gas used in welding is acetylene and this cone is created because of excess use of fuel gas.
The temperature of inner cone in the carburizing flame is from 2900 °C to 3200 °C. The temperature of intermediate cone or acetylene feather is nearly 2100 °C and the temperature of outer cone is from 1200 °C to 1300 °C.
When metal is welded using strongly carburizing flame, the metal boils and its puddle is not clear. The steel which is absorbing carbon from the flame, gives off heat. When the metal is cold after welding , the metal has properties of high carbon steel that is being brittle and subject to cracking.
Carburizing flame is used in medium carbon steel, nickel, etc. This flame is used in metal which does not absorb carbon or in a condition where absorption of carbon is required.
3) Oxidizing Flame:-
In this oxidizing flame, the content of oxygen is more than the content of fuel gas by volume.
It has two zones or two cones, the first one is called the inner cone and is white in colour. The inner zone is very bright. The second one is called outer cone and is blue in colour. The size of the inner cone in the oxidizing flame is very small as compared to its size in a natural or neutral flame. It has more heat than a neutral flame.
The temperature of the inner cone is from 3300 °C to 3500 °C and the temperature of outer cone is nearly 1200°C.
If more heat is required to weld then we use oxidizing flame in which the temperature of inner cone is very high.
Oxidizing flame is used to weld copper alloys like brass, bronze, etc.
Oxidizing flame should not be used to weld metals like zinc, copper, manganese steel, cast iron etc.
When an oxidizing flame is applied to steel, the oxidizing flame causes the molten metal to foam and give off sparks. The excess oxygen in oxidizing flame combines with steel and burn it.