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 type of welding process, which has already been discussed in the previous post.
In gas welding, gas welding flame plays a very most important role so before knowing the types of gas welding flames firstly we have to know what is a 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 time let's know the 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 melts the metals and joins 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
The 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 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
The middle part of
the flame is also known as the 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 are and their applications.
Types of Gas Welding Flames
- Neutral Flame
- Carburizing flame
- Oxidizing Flame
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| Types of Gas Welding Flames |
Neutral Flame
The neutral flame is made by mixing both oxygen and acetylene gases in equal quantities.
Its temperature is around
3,200 °C.
This flame is most
commonly used.
This flame is also called a balanced flame as well as a natural flame.
There are two regions of this
flame first one is the inner zone and the second one is the outer zone.
The inner region is white in
color, and its temperature varies from 3,100 to 3,500 degrees centigrade and
the outer region is blue in color and its temperature varies from 1275 to
1400 degrees 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 is also known as the 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 a
neutral flame because during welding there are no any type of chemical changes
on the molten metal and so it’s not oxidized 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 molecules of oxygen mix with acetylene gas in the same proportion then neutral flame produces.
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 an 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 an intermediate zone.
And the last part is the
outer zone.
In which the inner zone looks white in color, the intermediate zone which looks like red in color and the outer zone is look like blue in color.
You can clearly see this 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 color.
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.
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 blow pipe is high, it consists of two parts, the
inner part is very small and sharp with a very shiny white color, 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 compared 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 steel.
A slightly oxidizing flame is helpful when welding most copper bases or zinc base metal.
Uses of Oxidizing Flame
This flame is used for welding 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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