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Welding history

Classification of welding

Effect of welding speed

Welding defects

Types of welding joints

Welding position

Welding electrodes

Types of welding flame

Welding flux

Welding techniques

Welding symbol

Welding edge preparation

Advantages of welding joints

Thermal properties of metal

Welding safety

Types of welds

Brazing

Soldering

Types of welding flame

Welding flame

The character of flame is most important for oxy-acetylene welding or brazing and soldering. The types of flame describe in bellow.


Carburizing flame: When more acetylene present than oxygen in the flame then it is said to be carburizing flame or reducing flame. The carburizing or reducing flame is mostly used because of its need for oxygen will reduce oxides, such as iron-oxide or copper-oxide. Non-ferrous alloy and carbon steels may required a carburizing flame, where zinc compound materials may need oxidizing flame.

The carburizing flame when burning with an excess of acetylene, which is surrounding the central white cone is a ragged bluish-white area, which is suitably called as a “feather”. This extension of the cone coincides with the extension of the feather zone in which the acetylene is dissociated to yield hydrogen and carbon-monoxide. The reason for its extension is that more acetylene is passing that can be conveniently oxidized in the small cone surrounding the nozzle.


Oxidizing flame: If there is an excess amount of oxygen, the flame is said to be oxidizing flame. The secondary cone becomes very short and pointed because insufficient acetylene is passing from the nozzle to form a normal size cone. The excess of oxygen will react with the metal being welded and for this reason an oxidizing flame is employed when welding brasses to reduce the volatilization of zinc. The flame is slightly hotter than the neutral flame.


Neutral flame: When the acetylene and oxygen are in equal proportions in the flame then it is said neutral flame. The inner cone is large and sharply defined and the regulation of the flame is concerned with maintaining these two conditions. If these two conditions are not maintained the flame becomes either oxidizing or carburizing flame. During welding the nozzle tip becomes heated, this alert that the proportion of two gases tending to produce an oxidizing flame. For this reason it is needed to readjustment of flame frequently during welding process.


Pictures of flame

Carburising flame

Carburizing flame: Indefinite cone and ragged acetylene feather.

natural flame

Neutral flame: Clean white cone.

Oxidizing flame

Oxidizing flame: Pale short cone, short hard flame.

The maximum temperature of the oxy-acetylene flame is 3150– 33000C and the centre of this heat concentration is just off the extreme tip of the white cone.

Gas welding flame

Types of welding flame for different material

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Welding flame