The following are some notes taken from a night course I did on welding:
Stick welding
- Welders with a ‘hot start’ feature temporarily raise amperage when the arc is first formed to help warm up the material.
- Clean flux from weld between runs.
- Weld pool should be about two times the electrode diameter.
- The greater the distance the electrode is from the weld pool, the wider the weld pool becomes and you get more splatter.
- The lead angle of the electrode should be about 20° in the direction of the run.
- Larger electrodes are used for thicker materials.
- Rutile or general purpose rods have a wide range of applications.
- Electrode storage in the tropics is pretty important. Wet season humidity can destroy a pack of electrodes in an afternoon.
- Electrodes can sometimes restored by cooking them in an oven for 150°C for an hour or two.
- An old sealed fridge, fitted with an always-on incandescent bulb can be used to store the electrodes. Otherwise you are looking at about $200 for an electrode storage oven.
- Welding galvanised metal gives off toxic fumes.
- Wear a respirator fitted with activated charcol filter.
- And/or remove 5mm of galvinsation around the weld with a grinder.
- Store respirator filters in a zip-lock bag when not in use (they absorb moisture and lose effectiveness).
TIG welding
- Electrode made out of tungsten, has a melting point of 3000°C and is not consumed.
- Need to avoid contaminating the electrode by touching the weld pool or filler wire.
- Mild and Stainless steel requires a sharp fine point to the tungsten electrode.
- If the Tungsten becomes contaminated, you will need to grind it back. When grinding, keep the grains lengthwise. Otherwise the arc will wander.
- Argon is used as a shielding gas to prevent the weld from oxidizing while it is hot.
- Keep the gas flowing for 1 second per 10 amps after the arc is extinguished. (Post flow).
- TIG welding machines have three modes:
- DCSP - not good for aluminium. The electrode is negative.
- DCRP - need large electrode, limited applications. The electrode is positive.
- AC - Use a square wave arc that is extinguished for shorter periods. (Good for aluminium).
- Different types of tungsten electodes are available:
- Thoriated tungsten is good for stainless steels and copper. Used in DCSP mode (electrode is negative). This is not suited for aluminium.
- Zirconiated tungsten is good for aluminium, used in AC mode.
- Ceriated tungsten is good for all metals in AC & DC modes.
- Aluminium melts at 600°C and gomes in different grades:
- 1000 series is the lowest.
- 5000 and 6000 series is marine grade (most common)
- 7000 series is aviation grade and becomes brittle when welded.
- Filler wire needs to match material.
- Grinding tungsten on a grinder shared with steel may contaminate the electrode with steel particles.
- Use a stainless steel brush to clean any aluminium surfaces. A steel brush will contaminate the surface.
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