Aluminum – most common ore but requires lots of electricity to extract. It has a very sable oxide and is 2/3 the weight of mild steel. Tig welding only (electric welding with tungsten electrode)
Mild Steel – Iron & Carbon 0.025%
Medium Carbon Steel – 0.4 – 1.1% carbon.
High Carbon Steel – 1.3% carbon. High steel has a unique property that at 1% carbon it is heatable to become glass hard.
Heated iron properties:
220°c -> 320°
Soft -> Hard
Tough -> Brittle
Blue -> Straw
Soft soldering – with iron
Hard soldering – with a flame (brazing)
Brazing torch uses Acetylene & Oxygen, when balanced correctly the flame neither oxidizes or carbonises.
- Turn on the Acetylene tap (red) and draw it backwards through the pilot flame, adjust until slightly smokey.
- Turn on oxygen tap (blue) and adjust until the middle flame is just beyond the first. Acetylene flame is 30 times hotter than boiling water!
- Clean the metal surfaces to be soldered and add flux paste between surfaces. Flux prevents oxides from forming while the metal is cleaned. When soldering iron we use boax flux.
- Heat the metal generally holding the flame 2 to 4 cm away until red hot.
- There are two soldering techniques we tried;
- Melt some brazing rod (brazing rods are solder with a flux coating, for iron soldering we used a brass (copper and zinc) rod) and drag it along the join. The molten brass should follow the heat.
- Melt some brazing rod into the edge and drag it up the surface of the join without melting too much more brass to create a stronger more rounded join.
Tips: Lump solder means not enough heat was applied where as a very coppery colour means too much heat was applied.
A white coating some times on steel is Zinc and is called galvanized steel.
Plasma is super heated gas (compressed air and electricity)
Plasma cutting process:
- Switch on & turn power to 20amps. Turn on air the top light should be on.
- Put on goggles/face shield/gloves. The plasma unit produces UV light so cover up! Make sure the earth is attached to the table.
- Touch the nozzle lightly to the surface and drag it around.
- The hissing after use is just the cleaning cycle!
The plasma cutter can theoretically cut any conducting material. UWE’s unit cuts up to 12mm thick. Plasma cuts under water.
Gas welding will only weld matching metal surfaces.
- Set the torch the same as with brazing (first two steps above).
- Tack together the join to hold them stationary.
- Holding the flame perpendicular to the join, then at a 60° angle the length of the flame ‘bead’ from the join.
- Heat until a pea sized pool of molten metal appears, move the pool along aiming to move at an even pace.
- Using a copper coated steel rod melt the tip into a pool and tap evenly into the pool as you move it along. This fills up holes created by any over heating and adds metal to strengthen the join.
Tip: Hold the rod between thumbs & fingers so you can control it through gloves. You are looking for a ‘fish scale’ texture along both sides of the weld (which means the weld has penetrated both sides of the join). Slow and steady!
Mig Welding (metal inert gas)
- Turn the gas on (switch at the back). The gas is Carbon Dioxide & 10% Argon (its not toxic like carbon monoxide). Adjust the Amperage dial to the thickness of the metal (1.0 = 1mm thickness). The screen will show the watt power.
- Turn on the welding helmet and check its function by looking at and away from a light source.
- Weld using copper coloured wire with electricity, gas & control wire. Bend any excess wire out the way and as with Gas Welding hold the flame first perpendicular then at 60°.
Mild or stainless steel only. Steel has a higher electrical resistance than copper or brass. Before welding make sure the steel is corrosion free and the copper electrode on the spot welder is clean. It uses a low voltage but high current to weld two surfaces together. Our machine will weld 4mm of steel together (so 1mm and 3mm pieces). .
Drill the metal from center punch mark. Put the rivet into pneumatic pit riveter and through the hole then pull the trigger. Pit rivets can be used on leather, cloth etc… they may need a washer.