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Automatic arc-welding method

  • US 4,816,641 A
  • Filed: 07/14/1988
  • Issued: 03/28/1989
  • Est. Priority Date: 07/20/1987
  • Status: Expired due to Term
First Claim
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1. In an automatic arc-welding method, which comprises:

  • continuously supplying a welding wire as a consumable welding electrode at a prescribed feeding rate substantially vertically through a nozzle toward a groove formed between two objects to be welded;

    continuously moving said nozzle together with said welding wire along the longitudinal direction of said groove; and

    supplying a prescribed welding current to said welding wire to produce an arc between the tip of said welding wire and said groove, thereby welding said objects to be welded together at a prescribed welding speed along said groove by means of the arc heat;

    the improvement comprising;

    when welding said objects to be welded together along said groove,(a) continuously measuring a distance of a root gap of said groove in the downstream of said nozzle in the travelling direction thereof;

    (b) calculating a target welding current (I), with which a depth of penetration agrees with a target value thereof, in accordance with the following formula (1);

    
    
    space="preserve" listing-type="equation">I=I.sub.o -KG (1)where,I;

    target welding current,Io ;

    welding current when the distance of root gap is zero,K;

    constant dependent on the depth of penetration, the kind of shielding gas, the material of the welding wire and the like, andG;

    distance of root gap, and controlling said welding current so as to agree with the thus calculated target welding current;

    (c) calculating a target feeding rate (Vf) of said welding wire, at which an extension length of said welding wire from the tip of said nozzle agrees with a target value thereof, in accordance with the following formula (2);

    Vf =A·

    I+B·



    I2 (

         2)where,Vf ;

    target feeding rate of welding wire,I;

    welding current,l;

    extension length of welding wire, andA, B;

    constants dependent on the kind of shielding gas, the material of the welding wire and the like, and controlling said feeding rate of said welding wire so as to agree with the thus calculated target feeding rate of said welding wire;

    (d) calculating a target welding speed (V), at which a height of the weld bead agrees with a target value thereof, in accordance with the following formula (3);

    
    
    space="preserve" listing-type="equation">V=V.sub.f (V.sub.fo /V.sub.o +(d/k)·

    G) (3)where,V;

    target welding speed,Vf ;

    feeding rate of welding wire,Vfo ;

    feeding rate of welding wire when the distance of root gap is zero,Vo ;

    welding speed when the distance of root gap is zero,d;

    distance between the lowermost point of penetration and the uppermost point of weld bead,k;

    product of multiplication of the cross-sectional area of the welding wire and the deposition efficiency, andG;

    distance of root gap, and controlling said welding speed so as to agree with the thus calculated target welding speed.

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