Welding Flashcards
3 ways of providing heat for welding
- Gas welding
- Electric arc welding
- Resistance welding
3 ways to prevent oxidation
- Apply a non-reactive gas
- Apply flux
- Formation of a slag coating
Advantages of flux
- Prevents oxidation.
- Collects impurities and brings them to the surface.
Disadvantages of flux
- Creates a surface slag layer, must be chipped off if appearance is important.
Resistance seam welding
Parts pressed together through rollers Copper electrodes Continuous overlapping run of spot welds Each pulse lasts long enough to produce a spot weld Overlap 40%
Resistance spot welding
Between electrodes, pressed together
Nugget weld
Current generates heat
Distinctive circular mark
Submerged arc welding
Bare wire electrode fed automatically from a spool Generates an electric arc Flux (powder form) fed from a hopper Arc creates heat Slag protective coating Fully-automated
Electro-slag welding
Automatic, for thicker plates
Gap… quite large b/c filled with molten metal
Water-cooled copper shoes prevent…
Carriage, shoes and electrode move together
Gas welding (Oxy-Acetylene)
Fusion process
Metal melts, fuses joining edges
Oxygen + acetylene burned
Oxidation prevented by envelope of products of combustion
Oxy-Acetylene equipment
Acetylene cylinder Oxygen cylinder Oxygen and acetylene hoses Welding torch Pressure gauges Flashback arrestors
3 flame types (Oxy-Acetylene)
Neutral - equal portions of both gases
Oxidising - excess oxygen
Carburising - excess acetylene
Safety features (Oxy-Acetylene)
- Colour-coded cylinders (oxygen = black, acetylene = maroon)
- Different sized cylinders
- Flashback arrestors prevent the flame returning to the cylinders
- Cylinders can be turned off when finished welding
Neutral flame
- Equal portions of both gases
- Maximum combustion
- 3300 degrees
Oxidising flame
- Excess oxygen
- 3500 degrees
- Smaller flame
- Brass + bronze
Carburising flame
- Excess acetylene
- 3150 degrees
- Bigger flame (acetylene feather)
- Aluminium + alloy steel
Multi-run welding
Welding the same joint more than once. Creates a better, tougher joint. Anneals metals so they are less hard and brittle.
Application of TIG
Aluminium + stainless steel
Application of SAW
Large-scale straight line welds, such as shipbuilding
Application of Oxy-Acetylene
Automotive bodies (fabrication and repair)
Application of Resistance Seam
Filing cabinets
