WELDING MILD STEEL
Preparation 1
Carefully cut and file the edges of the two pieces so they fit together with no gaps or burrs. Clean rust from both sides and wipe with acetone. Clamp or hold the pieces so they’re butted snugly together, then secure them with tack welds.
Welding a butt joint 2
If you’re welding 1mm steel sheet (typical for car bodywork), use a 1.6mm tungsten with a sharp point and 1.0mm ER60S2 or S6 filler wire. Use scrap material to set the current. It’s likely to be around 40 amps. Set your machine to ramp up/down to this setting, if it has this feature. Start at one end, make a puddle, dip the rod, withdraw the rod slightly, move the torch forward and dip the rod again. Keep repeating to form the joint. Use the torch speed and the addition of rod to control the puddle.
Starting and finishing 3
When starting, wait for the puddle to appear on both sections before adding rod. When stopping, add extra rod and ramp down (if possible) to avoid a crater. If your set is scratch-start, position pieces of scrap steel at each end to start and finish on.
Lay-wire technique 4
An alternative to rod feeding. Keep the end of the rod in contact with the leading edge of the puddle without actually dipping it. Any rippling effect will come from torch movement/pulsing. This is a good technique if you only have thick rod to hand.
Fusing without filler 5
It’s no good for structural joints, but welding without filler rod is perfect for bodywork. Watch for a puddle to form on each side and flow into one. Move forwards, using the torch speed and gentle torch manipulation to control the puddle.
Managing distortion 6
Heating, cooling and the addition of filler metal will result in distortion. A distinct benefit of TIG is that it’s minimal and easy to rectify. The lower piece here was flattened with a few hammer taps. Use ER60S2 filler rod for a soft and malleable weld.
Welding thick steel 7
TIG is excellent for thick material. Bevel the joint where possible and leave a root gap. This is 6mm plate so we’re using a 2.4mm tungsten, 2.4mm filler rod and 120 amps. Fill the root gap first, then fill the rest of joint in another one or two passes.
Walking the cup 8
Make a puddle on one side of the bevel, add rod, then make a puddle on the other. Keep ‘walking’ the torch from one side to the other, melting the roots and keeping the filler rod at the leading edge. Do it freehand or rest the cup on the workpiece.