Aluminium blackish/dirty welding problem solving


    Aluminium dirty weld, blackishness, soot troubleshooting

    Reasons of blackish Marks in aluminium MIG/TIG Welding

    Possible Reasons Behind Black marks or Blackish Welding while welding Aluminium.
    • Uncleaned Base metal. 
    • Wrong Welding Technique. 
    • Wrong Shielding Gas Flow. 
    • Dirty filler wire

    Solutions to Aluminium Black welding

    Cleaning Of Base Metal.

    This is a very important step while welding aluminum, As Aluminum has a high affinity to oxygen. it will continuously form aluminium oxide(al2o3) on the surface of the base metal & oxides will create blackish weld.
    Aluminium Oxide AL2O3 has a higher melting point than aluminium, it will negatively affect penetration and so strength of joint, So cleaning of the base material from Oil, Grease as well as from Oxide layer is very important for a clean and strong joint.

    Cleaning measures must be followed while welding aluminium. Must use SS wire brush When using a stainless-steel brush, brush only in one direction.
    Take care to not brush too roughly: rough brushing can further imbed the oxides in the workpiece. Also, use the brush only on aluminium work-don't clean aluminium with a brush that's been used on stainless or carbon steel.

    Welding Technique. (travel direction)

    Using a Proper weld technique is very important in Aluminium welding, Pulling or using a drag angle will produce porous, dirty welds because of lack of gas coverage.
    If the torch is applied using a drag angle (also known as a Pulling/lagging torch angle), then the gas shielding will be absent from the molten puddle and the finished weld will appear gray or black.
    So recommended 10-15 degree Push angle  will result in better cleaning action, reduced weld contamination, and improved shielding-gas coverage will give a clean weld appearance.

    Refer image below to understand Push angle

    Shielding Gas

    Selecting Proper shielding gas as well as the proper gas flow rate is very important to achieve proper weld results. Also Purity of gas is imp so buy it from good quality suppliers instead of a local one.
    Using Too low gas flow will cause poor shielding hence weld will oxidize and look dull, Similarly, excess gas flow will create turbulence effect and will attract oxygen in the weld area will cause porous and dull weld.

    So proper gas flow rate is IMP. Thumb rule for the same is – Wire Dia * 10 (+/- 2) for eg. For 1.2mm dia wire flow rate should be 1.2 * 10  +2 /-2 = Flow rate = 10-14 LPM.

    Filler Wire

    Oxide layer also forms on filler wire same as with base metal, So the following measures must be taken.

    ·   Aluminium should never be stored outside.
    ·  Wire should be stored in the original box and any plastic interior bag it came in.
    ·  ts good to have a Dehumidified room for storage will keep wires dry.
    ·  Wire which will not be used for 2 days or more should be dismounted from the wire feeder, returned to its original packaging, and stored properly.
    ·  Aluminium wire which is stored following the above recommendations will be usable with no deterioration in performance for at least 2 years. Wire older than this should be discarded.

    So if you follow the above measures then you will definitely achieve clean and best quality weld. 
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