Types of Welding Flames & Applications: Neutral Flame, Carburizing Flame and Oxidizing Flame - Time Zero

Types of Welding Flames & Applications: Neutral Flame, Carburizing Flame and Oxidizing Flame

Oxidizing flame in gas welding / Carburizing flame in gas welding / Neutral flame in gas welding / Flame temperature

Based on the amount of oxygen consume from the O2 cylinder,

the flame produce will be divided into three types-

1 Neutral flame:

 The inner and outer cone will be distinguished base on their color,

That is the color of the inner cone is Red or Yellow and color of

outer cone is light Blue. Red or Yellow color flame indicates

incomplete combustion, and high blue color indicates the complete

combustion. Throughout the intersection of an inner and outer

cone, the maximum temperature is induced.

Maximum temperature is about 3260° C

Average temperature is 2000° to 2100° C

When compared to the maximum temperature, the average temperature of the flame is reducing by nearly 1/3rd, this is because, during combustion of the acetylene, a large amount of water is getting generated. It is immediately getting evaporating.

For evaporating off the water is required a large amount of heat.This flame is used for joining as well as cutting off all ferrous and nonferrous metals except brass. During joining  of the brass work piece using neutral flame, the zinc present in the Brass work piece will get evaporated and the only Cu will be left over in the joint. So that it is not giving the required mechanical property to the weld bead.

2 Carburizing flame or Reducing flame:

Because of short supply of oxygen from O2 cylinder the flame has traveled for longer distance for complete combustion. hence the length of the inner cone will be 2N to 3N. Because the flame is traveling for the longer distance the heat loss by convection radiation will be considerable. Due to this the maximum and average temperature will be reducing.

 Tmax = 3040°C          Tavg  = 21800°C to 1900°C

Application

1] Because of the lower average temperature of the flame high melting point metal cannot be joining by using the flame.

2] Because of soft supply of O2 the free carbon may present in the flame during joining of ferrous materials using carburizing flame, the free carbon present in the flame will be absorbed by the iron and become rich in carbon, therefore, the brittleness of weld bead is increasing and toughness is reducing. Due to this carburizing flame should not be used for joining of ferrous material.

3] Carburizing flame is most commonly used for joining of high carbon steel.

4] In case of steel as the carbon content into the steel increases the melting point will be reduced, therefore, high carbon possessing lower melting point hence the lower average temperature carburizing flame can be used for joining of high carbon steel.

5] In addition, high carbon steel is already saturated with carbon, therefore, even though free carbon available in the flame it cannot be observed by the high Carbon Steel.

6] To withstand for higher pressure and possessing the flexibility the host pipe connected to the O2 cylinder must be by using copper as a material.

7] When copper is exposed to acetylene it can chemically react with acetylene and produce past like material, therefore, the pipe will fail, and hence copper host pipe should not be used for connecting to C2 H2 cylinder. The best preferable material for making acetylene hose pipe is plastic or rubber, so it can withstand for lowest pressure, cheaper and does not have any chemical reaction.

3 Oxidizing flame:

 Because of an excess amount of oxygen is supplied from the oxygen cylinder, distance to be traveled by the flame for complete combustion will be reducing, therefore, the length of inner cone is reduced. A slightly lean mixture will always give the highest efficiency of combustion; therefore, the maximum temperature in the oxidizing flame is always greater than neutral flame.

 Tmax = 3380°C          Tavg  = 2100°C to 2200°C

Application

1] Because of the higher average temperature of the flame high melting point metals can be joint easily.

2] Due to the supply of excess oxygen from the oxygen cylinder there is the possibility of free O2 may present in the film. So that during joining of highly reactive metals, the free oxygen can be easily combined with metals and produce metal oxides and hence the oxidizing flame cannot be used for highly reactive metals, like aluminum, magnesium etc.

3] It can be used for joining of the brass work piece that is during joining of brass because of free oxygen present in the flame, it is combining with some quantity of zinc present in the brass and produces zinc oxide also called as a tenuous oxide which is floating on weld pull. It is not allowing the remaining zinc to evaporate.

Tag:

types of welding flames pdf / oxidizing flame in gas welding / gas welding flames / carburizing flame in gas welding / carburizing flame temperature / neutral flame temperature / 

oxidizing flame temperature / neutral flame in gas welding