Welding RevisionLC Engineering
Gas Welding Revision
Stages of combustion
Primary Combustion – Acetylene & Oxygen burn in the primary combustion zone to give off Carbon Monoxide and Hydrogen.
C2H2+O2 2CO+H2
Secondary Combustion – oxygen is sucked in from the weld pool and is burned with Carbon Monoxide & Hydrogen to give off Carbon Dioxide and Water vapour.
CO+H2+O2 CO2+H2O
Types of FlamesThe Oxidising Flame
This is a result of excess Oxygen. Approx 1.5 parts oxygen to 1 part acetylene. If used with steel the excess oxygen would contimnate the joint, so it is used for copper and some bronzes. It has a temp. of about 3500ºC
max temp zoneinner cone
secondary combustion zone
The Carburising FlameThis is a result of excess Acetylene. Approx 0.9 parts oxygen to 1 part acetylene. Has a temp of approx 3150ºC and is used for welding alloy steels and aluminium alloys
max temp zoneinner cone
secondary combustion zone
C
Acetylene feather
Transformer/ RectifierTransformer RectifierDropping Voltage means
current increases current, which is needed for welding.
There is a primary and secondary coil.
The number of windings on each coil controls the output current.
Primary 100 Turns and 220V and 10A
Secondary 200 coils = 110V & 20A
The Rectifier converts AC to DC.
It uses 4 diodes arranged in a diamond shape.
2 diodes conduct in each half-cycle.
The capacitor ensures a smooth output.
Transformer/Rectifier
MIG/MAGSMetal Inert Gas/Metal
Arc Gas Shielded.Semi-automatic ProcessConsumable Electrode
fed automatically.Argon gas protects the
weld pool like a flux.No slag produced.Suitable for steel.
Argon Gas
Wire Feed
Power Plant
Welding Gun
Electrode
NOTE: CO2 welding is a form of MIG/MAGS
TIG/TAGSTungsten Inert GasNon –consumable
Electrode.Filler rod used.Argon gas protects
the weld pool like a flux.
Suitable for Aluminium & Stainless Steel.
Filler Rod
NOTE: Label the diagram using MIG/MAGS as a reference.
A Transformer steps up and down the voltage to set welding currents.
The Rectifier converts AC to DC using a series of diodes.
Resistance Spot Welding
Resistance Seam Welding
Submerged Arc Welding
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