Types of Gas Welding Flames and Their Uses

Hello friends in this topic, we will know about types of gas welding flames and their uses and at the last also discuss some FAQ related to gas welding flame.


Gas welding is the most important types of welding process, which has already discussed in previous post.

 

In gas welding, gas welding flame plays very most important role so before knowing types of gas welding flames firstly we have to know what is flame in gas welding?


Choosing the wrong flame can lead to many welding defects like porosity, cracks, slag inclusion and many more.


So, without wasting of time let's know types of gas welding flames and their uses.

 

What is Flame?


In gas welding, the flame produced by mixing a flammable gas and oxygen in the nozzle or tip of the blow pipe is called flame.

 

Mostly in gas welding, Oxy-acetylene flames are used.


Always grind the welded area after welding and re-welding if needed.


Oxy-acetylene Flame


Oxy-acetylene flame is mostly used for gas welding because of its high flame temperature (3200 °C). 


Oxygen is generated by liquefaction of air or by electrolysis of water and acetylene is produced as a result of a chemical reaction of calcium carbide in contact with water.


calcium carbide + water → oxy-acetylene + slaked lime


CaC2 + 2H2O → C2H2 + Ca (2 OH )


Various flames can be obtained by changing the respective amounts of acetylene and oxygen in the gas mixture.


In an oxy-acetylene method, metal is heated through the hot flame of a gas-fed torch which melt the metals and join together to form a weld. 


In many cases, excess metal from a welding rod is melted into the joint and making the joint as strong as the base metal.

 

Parts of the Oxy-acetylene Flame

 

Oxy-acetylene flame consists of three main parts.

  • Inner Part (2760 °C -3,480 °C)
  • Middle Part (2090 °C -3,800 °C)
  • Outer Part (1260 °C -2100 °C )

Inner Part or Inner Cone 

 

The inner cone or inner part is the part where the mixture of both the gases Oxygen and Acetylene exits the tip of the blow pipe. 

 

It is also called as the luminous cone or inner cone or inner zone.

 

It is a bright white low and the size is also less.

 

The temperature of this part is from 2760 °C to 3,480 °C.

 

The front part of the inner part is the hottest part of the flame.

 

Middle Part or Intermediate Zone

 

The middle part of the flame also known as Intermediate zone.

 

It is also called the blue reducing zone of carbon monoxide and hydrogen.

 

Its temperature is around 2090 °C.

 

Outer Part or Outer Envelope

 

This is the outer part of the flame.

 

It completes its combustion process by getting oxygen from the air. 

 

The temperature of this part varies from 1260 °C to 2100 °C. 

 

Air, oxygen and acetylene combine in different proportions to form different types of flame. 

 

In this zone acetylene first burns with the oxygen added inside the torch and later this burnt gas burns again in the atmospheric air.

 

Now, let's know how many types of gas welding flames and their applications.

 

Types of Gas Welding Flames


There are following types of gas welding flames are used.

  • Neutral Flame
  • Carburizing flame
  • Oxidizing Flame

Show in the figure types of gas welding flames which are described below in detail.

 

types of gas welding flame
Types of Gas Welding Flames


Neutral Flame

 

The neutral flame is made by mixing both oxygen and acetylene gases in equal quantity.

 

Its temperature is around 3,200 °C.

 

This flame is most commonly used.

 

This flame is also called as balance flame as well as natural flame.

 

There are two regions of this flame first one is inner zone and second one is the outer zone.

 

The inner region is white in color, and its temperature is varies from 3,100 to 3,500 degree centigrade and the outer region is blue in color and its temperature is varies from 1275 to 1400 degree centigrade.


You can see in the above mentioned figure.

 

This neutral flame has a well-defined inner zone, and it is surrounded by an outer flame envelope which also known as outer zone, which results from the combination of oxygen in the air and extremely hot carbon monoxide and hydrogen gases from the inner zone.


This flame is called as neutral flame because during welding there is no any type of chemical changes on the molten metal and so it’s not oxidize or carburized the metal.  

 

Uses of Neutral Flame


This flame is used for welding mild steel, cast iron, stainless steel, copper and aluminum.

 

Chemical Reaction of Neutral flame


When molecule of oxygen mix with acetylene gas in same proportion then neutral flame produce.

 

O2 + C2H2 = CO + H2 + heat

 

Where,


O2 = Oxygen

 

C2H2 = Acetylene Gas

 

CO = Carbon monoxide

 

H2 = Hydrogen

 

After that hydrogen and carbon monoxide again react with oxygen and developed outer envelope or outer zone.

 

CO + H2 + O2 = CO2 + H2O

 

Where,


CO2 = Carbon dioxide

 

H2O = Water

 

Carburizing Flame

 

The amount of acetylene in this flame is high, it has three parts, first one is the inner zone and it also has the middle part which is called intermediate zone.

 

And the last part is the outer zone.

 

In which inner zone is look as a white in color, the intermediate zone which is look as a red in color and the outer zone is look as a blue in color.


You can clearly see in the figure.

 

The temperature of this flame is 3,100 °C.

 

It is also known as reducing flame.

 

A reducing flame or carburizing flame can be identified by the acetylene feather which is present between the inner zone and outer zone. 

 

The outer cone or outer envelope is always longer as compared to the neutral flame and also much brighter in colour.

 

A reducing flame does not fully consume the available carbon; therefore, it has a lower burning temperature, and the remaining carbon is injected into the molten metal. 


With iron and steel it produces a very hard, brittle material called iron carbide. 


Due to this iron carbide, makes the metal unsuitable for many applications that may require bending or stretching of welds. 

 

Metals that absorb carbon should not be welded with a reducing flame.

 

Uses of Carburizing Flame


It is used for welding high carbon steel, aluminum and alloy steel.

 

Oxidizing Flame


In this, the amount of oxygen in the gases coming out of the blowpipe is high, it consists of two parts, the inner part is very small and sharp with very shiny white colour, its temperature is 3,300 ° C.


An oxidizing flame can be identified only by the smaller region which is always smaller and more pointed as compare to the neutral flame.


The outer flame envelope is very small.


Oxidizing flame is hotter than neutral flame.


This is due to excess oxygen and due to which the temperature becomes higher. 


Excess oxygen combines with many metals to form hard, brittle, low strength oxides.


For these reasons, oxidizing flames are of limited use in welding.


It is not used in welding of steel. 


A slight oxidizing flame is helpful when welding most copper bases or zinc base metal.

 

Uses of Oxidizing Flame 


This flame is used for welding of copper, zinc, cast iron, brass.

 


So here I discussed types of gas welding flames and their uses, applications as well as chemical reaction of these flames.

 

I hope you all enjoy this post.

 

FAQ for Types of Gas Welding Flames

 

Which flame is used for gas welding? 


Oxy-acetylene is the flame which is most used in gas welding.

 

What are the three types of flame in oxyacetylene welding?

 

In oxyacetylene welding the three types of flame is neutral, oxidizing and carburizing flame.

 

Which flame is used for Aluminium welding?
 

For aluminium welding mostly used neutral as well as carburizing flame.

 

Which flame is used for cutting operation?
 

For cutting operation always use neutral flame.

 

Which flame is used for copper welding?


For copper welding mostly used oxidizing flame.

 

Which of the following flame is harmful to steel?


The flame which is harmful to the steel is oxidizing flame due to excess of oxygen in this flame more chance to rust of steel.

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