Types of Flames: 3 types of oxy‐acetylene flames

Flickering Flames: A Guide to Understanding and Identifying Various Types of Flames

What are the types of flames that may be produced in gas welding?

Answer: Types of Flames

In oxy‐acetylene gas welding, a flame is the most important means to control the welding joint and the welding process.

There are three basic types of oxy‐acetylene flames:

1. Neutral flame (Acetylene and oxygen in equal proportions).

(a) Inner cone shows incomplete combustion.

(b) Outer bluish color indicates complete combustion.

(c) Maximum temperature of the flame is induced at the intersection of the inner cone and outer cone.

(d) During the combustion of acetylene large quantity of water is produced, to evaporate this water, a large amount of heat is carried away.


(a) It is used for ferrous and nonferrous metals strictly prohibited for zinc alloys. For example, brass because zinc is present in brass, it will get evaporated.
(b) It can be used for high melting point materials.

2. Carburizing flame or reducing flame (excess of acetylene) :

(a) Excess supply of acetylene.

(b) Because of less supply of oxygen, combustion is incomplete.

(c) Temperature generated in the flame is less.


(a) Because of lower average temperature, high melting point metals cannot be joined.

(b) Because of un‐burnt carbon present in flame, this carbon may absorb by the iron during the joining of ferrous metals and increase the brittleness and reduce toughness. So it should not be used for the joining of ferrous materials.

(c) This is mostly used for high carbon steel.

Types of flames

3. Oxidizing flame (excess of oxygen) :

(a) Here excess amount of oxygen is present.

(b) Due to the presence of the excess amount of oxygen, complete combustion of acetylene is taking place.

(c) The temperature of the flame is maximum than any other flames.


(a) Because of higher average temperature, it can be used for high melting point materials.

(b) Oxidizing flame is used to weld metal like copper (Cu). It is not suitable for highly reactive metals like Al, Mn, etc., because of an excess supply of oxygen there is a possibility of oxidation.

(c) It can be used for joining the brass workpiece.

Types of Flames Types of Flames

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