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This presentation contains all the info. about gas welding.
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Abhimanyu pradhan B.TECH MECHANICAL (3rd YEAR)
1222240001
GAS WELDING
Gas welding is a fusion welding process.
Flame produced by the combustion of gases is employed to melt the metal
The molten metal is allowed to flow together thus forming a solid continuous joint upon cooling.
By burning pure oxygen in combination with other gases, in special torches, a flame up to 3300 degree can be attained.
During the welding, heat from the flame is concentrated on the joint edges until the metal melts and starts to flow. When the molten metal from both sides melts it starts to fuse, when the metal cools down the two parts become Permanently joined
Additional Filler Metal is fed in by hand into the weld pool, at regular intervals where it becomes molten and joins with the parent metal.
The Oxy-acetylene welding Flame
Oxidizing Excess oxygen (1.5:1) (Brasses, Bronzes, copper)
Neutral Equal acetylene & oxygen (low carbon steel, mild steels).maximum temp. is
3100 degree
Reducing or Carburizing Excess acetylene (0.9:1) (Alloy steels and aluminium alloys) . 2900 deg
Inner Cone
Secondary Combustion envelope
Acetylene feather
Max. Temp. Zone
Carburising Neutral Oxidising
The Oxy-acetylene welding Flame
Equipment used in Oxy-Acetylene welding
The oxygen and acetylene hose pipes
Gases used
Gas pressure Regulators
Flashback arrestor
Welding torch/Welding nozzle
Filler rods and fluxes
Gases used
Oxygen extracted from air and compressed into cylinders at high pressure. Cylinder is black. Oil should never be brought into contact and should not be used on fittings
Acetylene (C2H2) is a fuel gas. Cannot be compressed directly as explodes at high pressures. Cylinders are packed with porous material which is filled with acetone. Acetone absorbs acetylene. Cylinder colour coded maroon
Gas Pressure Regulators
One gauge indicates the pressure of the cylinder and the other indicates the pressure in the supply pipe to the torch.
Advantages
The equipment is inexpensive, simple and is easily portable.
Useful for welding light metals such as automobile bodies and repair works
A large variety of material can be welded.4.Welds can be produced at reasonable cost.
Compared to electric arc welding this provides greater flexibility with respect to heat impact and cooling rates.
Disadvantages
Equipment must always be handled carefully as in certain circumstances acetylene is explosive as oxygen when used in an oily atmosphere (such as an old dirty garage floor pit).
A high temperature flame from a hand held torch isdangerous when handled carelessly.
It is much slower than electric arc welding and does not concentrate the heat close to the weld. Thus, the heat treated area is larger, which causes more distortion
Highly skilled operators are required to produce a good weld.
If electric arc welding is available gas welding is seldom used for work over 3.2mm thick.
The process is not satisfactory for heavy sections
Defects
Cracking
Incorrect edge preparation
Craters
Under cutting
Porosity
Over welding
APPLICATIONS
In aircraft building industry
Cylinders, boilers & vessel manufacturing
Structural constructions like bridges, buildings, ships etc.
Manufacturing of furnaces, tanks, cranes, hoists, railway equipment's, steel furniture etc.
Building of automobile bodies and other parts.
WELDING-APPLICATIONS1
. In aircraft building industry.2.C
ylinders, boilers & vessel manufacturing.3. Structural constructions like bridges, buildings, shipsetc.4. Manufacture of various machineries like mechanical,food processing, agricultural, earth moving & textilemachineries.5.B
uilding of automobile bodies and other parts.6. Manufacturing of furnaces, tanks, cranes, hoists,railway equipments, steel furniture etc.39
THANK YOU