Automatic arc-welding method

• US 4,816,640 A
• Filed: 07/14/1988
• Issued: 03/28/1989
• Est. Priority Date: 07/20/1987
• Status: Expired due to Term

• Current Assignee: NSK Corporation (NSK Limited)
• Original Assignee: NSK Corporation (NSK Limited)
• Inventors: Kanjo, Yosihiro, Nishi, Yasuhiko, Sugitani, Yuji
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US07/219,391
• Time in Patent Office: 257 Days
• Field of Search: 219/137 PS, 219/130.21, 219/137.71, 219/124.34, 219/124.22
• US Class Current: 219/137.0PS
• CPC Class Codes: B23K 9/073 Stabilising the arc
• CPC Class Codes: B23K 9/0953 using computing means

Abstract

An automatic arc-welding method, which comprises, when welding two objects to be welded together by means of a welding wire along a first groove formed between the objects to be welded on a first side thereof, continuously determining by calculation a target welding current, with which a depth of penetration agrees with a target value thereof, on the basis of the root gap, the material of the welding wire and the like; continuously determining by calculation a target feeding rate of the welding wire, at which an extension length of the welding wire agrees with a target value thereof, on the basis of the welding current, the material of the welding wire and the like; continuously determining by calculation a target welding speed, at which a height of the weld bead agrees with a target value thereof, on the basis of the feeding rate of the welding wire, the material of the welding wire, the root gap and the like; and on the other hand, when welding the objects to be welded together by means of the welding wire along a second groove formed on a second side of the objects to be welded, opposite to the first groove, continuously determining by calculation a target welding current and a target welding speed while taking into consideration the depth of penetration and the weld bead in the first groove; thereby automatically controlling the welding current, the feeding rate of the welding wire and the welding speed on the basis of the respective target values thus determined.

Claims

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 first groove formed between two objects to be welded on a first side thereof;

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

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

then, continuously supplying said welding wire at a prescribed feeding rate substantially vertically through said nozzle toward a second groove formed on a second side of said objects to be welded, opposite to said first groove;

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

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

the improvement comprising;

(A) when welding said objects to be welded together along said first groove,

(a) continuously measuring a distance of a root gap 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,

I_o ;

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, and

G;

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 (V_f) 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);

space="preserve" listing-type="equation">V.sub.f =A·

I+B·

l·

I.sup.2 (

     2)

where,

V_f ;

target feeding rate of welding wire,

I;

welding current,

l;

extension length of welding wire, and

A, 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);

##EQU5## where, V;

target welding speed,

V_f ;

feeding rate of welding wire,

V_fo ;

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

V_o ;

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, and

G;

distance of root gap,

and controlling said welding speed so as to agree with the thus calculated target welding speed; and

(B) when welding said objects to be welded together along said second groove,

(a) continuously measuring a distance of a root gap in the downstream of said nozzle in the travelling direction thereof;

(b) calculating a target welding current, with which a target depth (P₂) of penetration satisfies the following formula (4) when the distance of said root gap is zero, in accordance with said formula (1);

space="preserve" listing-type="equation">P.sub.2 ≧

t.sub.f -P.sub.1 (

     4)

where,

P₂ ;

target depth of penetration of the second groove,

P₁ ;

target depth of penetration of the first groove, and

t_f ;

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

(c) 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 (5);

##EQU6## where, V;

target welding speed,

V_fo ;

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

V_o ;

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 welding wire and the deposition efficiency, and

G;

distance of root gap,

and controlling said welding speed so as to agree with the thus calculated target welding speed.