CN1943969A

CN1943969A - Electromagnetic impact device for controlling welding heat cracking and deformation

Info

Publication number: CN1943969A
Application number: CN 200610150952
Authority: CN
Inventors: 方洪渊; 徐文利; 杨建国; 刘雪松; 许威
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2006-10-27
Filing date: 2006-10-27
Publication date: 2007-04-11
Anticipated expiration: 2026-10-27
Also published as: CN100496869C

Abstract

The present invention relates to welding technology, and is one kind of electromagnetic impact device for controlling welding heat crack and deformation. The electromagnetic impact device includes one pulse discharge circuit, and one coil with two input ends connected to the output of the pulse discharge circuit. The coil is set over the weld seam, and has lower surface apart from the upper surface of the weld seam by 2-5 mm and center in the distance to the center of the welding torch of 25-60 mm. The present invention has simple operation, easy control on energy, small size, low cost, stereo electromagnetic impact force and no need of contacting the coil with the welded workpiece.

Description

Device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion

Technical field

The present invention relates to a kind of technical field of controlling HOT CRACK FOR WELDING P and distortion.

Background technology

HOT CRACK FOR WELDING P, welding residual stress and residual deformation are the common problems that exists in the welding process, for addressing the above problem, the device of various control residual stress and residual deformation has been proposed both at home and abroad, as static and dynamic temperature difference stretch, with weldering roll, with welding hammering and weld with trailing impactive rolling device etc., but said apparatus all has their weak point.Static and dynamic tensile device can not reduce the cross-direction shrinkage of weld seam, and production efficiency is low, complicated operation.Huge with the weldering rolling device, the easy and welding gun interference of rolling wheel produces and beats the arc phenomenon.Exist the vibration of tup beat bigger with the weldering hammering device, need to increase the shortcoming of guiding mechanism.The weld with trailing impactive rolling device is that (patent No. is: ZL03132581.5) for a kind of new control welding stress and the technology of distortion, although this method remedied with weldering roll with the weldering percussion mechanism the part deficiency, but it still adopts mechanical force that the direct contact type impact is carried out on the test specimen surface, the assurance of its impact effect is based upon on the basis that reduces impact area, and the size of impulsive force is difficult to quantification, and thick structure and the hardness welding of material greatly in not being suitable for.

Summary of the invention

The present invention seeks in order to solve the cross-direction shrinkage that existing static state and dynamic tensile device can not reduce weld seam, production efficiency is low, complicated operation; Huge with weldering rolling device equipment, the easy and welding gun interference of rolling wheel produces and beats the arc phenomenon; Exist the vibration of tup beat bigger with the weldering hammering device, need to increase guiding mechanism; The size of weld with trailing impactive rolling device impulsive force is difficult to quantification, the welding of the big material of thick structure and hardness in not being suitable for, and a kind of device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion that provides.

The present invention comprises pulse discharge circuit 1, coil 2; Two outputs of pulse discharge circuit 1 are two inputs of connecting coil 2 respectively, coil 2 be arranged on weld seam 3 directly on the position, the lower surface of coil 2 is 2～5mm apart from the distance L between the upper surface of weld seam 32, and the center of coil 2 is 25～60mm to the centre distance L1 of welding gun 7.

The present invention can realize the welding of low stress, small deformation, no hot tearing to the thick LY12 aluminium alloy plate of 2mm, and residual deformation can be controlled in the 6%-10%.The present invention relies on the effect control welding stress and the distortion of electromagnetic force to have following advantage: simple to operate; The size of plant capacity is easy to accurate control, thereby makes the magnetic field force can be accurately quantitative; Electrical transmission is compared more or less freely with the mechanical force transmission, it is little to take up room; Application of force coil is made simple, and cost is low; Electromagnetic force is body force and has impact characteristics, can impel stressed object to produce plastic deformation more effectively; Can come the size and the distribution of controlling magnetic field power by the structure that changes coil; Application of force coil need not to contact with welded piece.

Description of drawings

Fig. 1 is a front view of the present invention; Fig. 2 is the vertical view of Fig. 1; Fig. 3 is the circuit structure logic diagram of pulse discharge circuit 1 among Fig. 1; Fig. 4 is the electrical block diagram of pulse discharge circuit 1 among Fig. 1; Fig. 5 is the structural representation of the specific embodiment six; Fig. 6 is the vertical view of Fig. 5.

The specific embodiment

The specific embodiment one: in conjunction with Fig. 1, Fig. 2, Fig. 3, Fig. 4 present embodiment is described, present embodiment is made up of pulse discharge circuit 1, coil 2; Two outputs of pulse discharge circuit 1 are two inputs of connecting coil 2 respectively, coil 2 be arranged on weld seam 3 directly on the position, the lower surface of coil 2 is 2～5mm apart from the distance L between the upper surface of weld seam 32, and the center of coil 2 is 25～60mm to the centre distance L1 of welding gun 7.

Pulse discharge circuit 1 is made up of main circuit 1-1, IGBT circuits for triggering 1-2, time base circuit 1-3, thyristor gating circuit 1-4, hysteresis voltage comparator circuit 1-5, the first logic circuit 1-6, the second logic circuit 1-7, the first on-off circuit 1-8 and second switch circuit 1-9;

Operation principle: producing pulse current by pulse discharge circuit 1, when coil 2 feeds pulse current, place the weldment 6 of coil 2 belows to induce induced-current with coil 2 current opposite in direction, thereby generation induced field, the magnetic field effect of induced field and coil 2, make 2 pairs of weldments of coil 6 produce one moment downward pulse-electromagnetic force, the brittle temperature range 5 both sides metals of weldment 6 produce extension owing to be subjected to the effect of pulse-electromagnetic force, therefore the metal in the brittle temperature range 5 is compressed strain, thereby has prevented the generation of HOT CRACK FOR WELDING P.Coil 2 feeds pulse current, and the weldment that is in high temperature 6 at 4 rears, molten bath is subjected to downward pulse-electromagnetic force, and weld seam 3 plasticity takes place extends, and makes welding residual stress and residual deformation be reduced.

The specific embodiment two: in conjunction with Fig. 1, Fig. 2 present embodiment is described, the difference of present embodiment and embodiment one is that coil 2 centers are 25～45mm to welding gun 7 centre distance L1, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment one.

The specific embodiment three: in conjunction with Fig. 1, Fig. 2 present embodiment is described, the difference of present embodiment and embodiment two is that coil 2 centers are 26mm to welding gun 7 centre distance L1, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment two.

The specific embodiment four: in conjunction with Fig. 1, Fig. 2 present embodiment is described, the difference of present embodiment and embodiment two is that coil 2 centers are 35mm to welding gun 7 centre distance L1, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment two.

The specific embodiment five: in conjunction with Fig. 1, Fig. 2 present embodiment is described, the difference of present embodiment and embodiment two is that coil 2 centers are 44mm to welding gun 7 centre distance L1, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment two.

The specific embodiment six: in conjunction with Fig. 5, Fig. 6 present embodiment is described, present embodiment and embodiment one difference are that it has increased by the first coil 2-1, the second coil 2-2 and the first pulse discharge circuit 1-10; Two outputs of the first pulse discharge circuit 1-10 connect the end of the first coil 2-1 and the end of the second coil 2-2 respectively, the other end of the first coil 2-1 is connected to the other end of the second coil 2-2, the first coil 2-1 and the second coil 2-2 symmetry respectively are positioned over top, weld seam 3 both sides, the center of the first coil 2-1 and the second coil 2-2 is 20～30mm apart from weld seam 3 distance between center line L3 respectively, the vertical distance at centre-to-centre spacing welding gun 7 centers of the first coil 2-1 and the second coil 2-2 is that L4 is 25～35mm, the centre distance L5 of the centre-to-centre spacing welding gun 7 of coil 2 is 45～60mm, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment one.

The specific embodiment seven: present embodiment is described in conjunction with Fig. 5, Fig. 6, present embodiment and embodiment six differences are that the center of the first coil 2-1 and the second coil 2-2 is 20mm apart from weld seam 3 distance between center line L3 respectively, the vertical distance at centre-to-centre spacing welding gun 7 centers of the first coil 2-1 and the second coil 2-2 is that L4 is 25mm, the centre distance L5 of the centre-to-centre spacing welding gun 7 of coil 2 is 44mm, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment six.

The specific embodiment eight: present embodiment is described in conjunction with Fig. 5, Fig. 6, present embodiment and embodiment six differences are that the center of the first coil 2-1 and the second coil 2-2 is 25mm apart from weld seam 3 distance between center line L3 respectively, the vertical distance at centre-to-centre spacing welding gun 7 centers of the first coil 2-1 and the second coil 2-2 is that L4 is 30mm, the centre distance L5 of the centre-to-centre spacing welding gun 7 of coil 2 is 50mm, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment six.

The specific embodiment nine: present embodiment is described in conjunction with Fig. 5, Fig. 6, present embodiment and embodiment six differences are that the center of the first coil 2-1 and the second coil 2-2 is 30mm apart from weld seam 3 distance between center line L3 respectively, the vertical distance at centre-to-centre spacing welding gun 7 centers of the first coil 2-1 and the second coil 2-2 is that L4 is 35mm, the centre distance L5 of the centre-to-centre spacing welding gun 7 of coil 2 is 59mm, and other The Nomenclature Composition and Structure of Complexes is identical with the specific embodiment six.

Claims

1, controls the device of HOT CRACK FOR WELDING P and distortion with the weldering electromagnetic impact, it is characterized in that it comprises pulse discharge circuit (1), coil (2), two outputs of pulse discharge circuit (1) are two inputs of connecting coil (2) respectively, coil (2) be arranged on weld seam (3) directly on the position, the lower surface of coil (2) is 2～5mm apart from the distance between the upper surface of weld seam (3) (L2), and the center of coil (2) is 25～60mm to the centre distance (L1) of welding gun (7).

2, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 1 is characterized in that pulse discharge circuit (1) is made up of main circuit (1-1), circuits for triggering (1-2), time base circuit (1-3), thyristor gating circuit (1-4), hysteresis voltage comparator circuit (1-5), first logic circuit (1-6), second logic circuit (1-7), first on-off circuit (1-8) and second switch circuit (1-9); The voltage signal output end of main circuit (1-1) connects the input of hysteresis voltage comparator circuit (1-5), the output of hysteresis voltage comparator circuit (1-5) connects an input of first logic circuit (1-6) and an input of second logic circuit (1-7), the output of time base circuit (1-3) connects another input of first logic circuit (1-6) and another input of second logic circuit (1-7), the output of first logic circuit (1-6) connects the input of first on-off circuit (1-8), the output of second logic circuit (1-7) connects the input of second switch circuit (1-9), two outputs of first on-off circuit (1-8) connect two inputs of IGBT circuits for triggering (1-2) respectively, two outputs of second switch circuit (1-9) connect two inputs of thyristor gating circuit (1-4) respectively, three outputs of IGBT circuits for triggering (1-2) connect three inputs of main circuit (1-1) respectively, and two outputs of thyristor gating circuit (1-4) connect two other input of main circuit (1-1) respectively.

3, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 2 is characterized in that main circuit (1-1) is made up of choke coil (L), the 6th electric capacity (C6), the 31 resistance (R31), IGBT module (Q5), the 7th electric capacity (C7), the 32 resistance (R32) and the 34 resistance (R34), controllable silicon (Q6), the 33 resistance (R33), the 5th electric capacity (C5), the 6th diode (D6); One end of choke coil (L) connects the output of power supply VCC, the other end of choke coil (L) connects an end of the 31 resistance (R31) and an end of the 6th electric capacity (C6), the other end of the 31 resistance (R31) connects the source electrode of IGBT module (Q5), the drain electrode of IGBT module (Q5) connects an end of the 7th electric capacity (C7), the anode of one end of the 32 resistance (R32) and controllable silicon (Q6), the other end of the 32 resistance (R32) connects an end and the output voltage signal end of the 34 resistance (R34), one end of the 33 resistance (R33) connects the anode of controllable silicon (Q6), the other end of the 33 resistance (R33) is connected with an end of the 5th electric capacity (C5), the negative electrode of controllable silicon (Q6) connects the cathode terminal of the 6th diode (D6), one end of the other end of the 5th electric capacity (C5) and output pulse current, the other end of the 6th electric capacity (C6), the other end of the 7th electric capacity (C7), the other end of the 34 resistance (R34), the other end ground connection GND-A of the anode tap of the 6th diode (D6) and output pulse current end.

4, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 2 is characterized in that hysteresis voltage comparator circuit (1-5) is made up of first resistance (R1), first operational amplifier (U1A), the 3rd resistance (R3), first variable resistance (R27), second resistance (R2), the 7th voltage-stabiliser tube (D7), the tenth resistance (R10); Main circuit (1-1) voltage signal output end connects an end of first resistance (R1) of hysteresis voltage comparator circuit (1-5), the other end of first resistance (R1) connects the reverse input end pin 2 of first operational amplifier (U1A), the in-phase input end pin 3 of first operational amplifier (U1A) connects an end of the 3rd resistance (R3), the other end of the 3rd resistance (R3) connects the convertible tip of first variable resistance (R27), two stiff ends of first variable resistance (R27) connect power supply VCC1 and ground connection (GND-A) respectively, the power supply termination power VCC2 of first operational amplifier (U1A), the end pin 4 ground connection GND-B of first operational amplifier (U1A), the output pin 1 of first operational amplifier (U1A) connects an end of second resistance (R2), the other end of second resistance (R2) connects the negative electrode of the 7th voltage-stabiliser tube (D7), one end of the tenth resistance (R10), the input of the input of first logic circuit (1-6) and second logic circuit (1-7), the other end of the tenth resistance (R10) connects the plus earth GND-B of in-phase input end pin 3, the seven voltage-stabiliser tubes (D7) of first operational amplifier (U1A).

5, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 2 is characterized in that time base circuit (1-3) is made up of the 3 555 chip (U3), the 23 resistance (R23), the 24 resistance (R24), the 25 resistance (R25), second variohm (R29), the 3rd variohm (R30), the 8th voltage-stabiliser tube (D8), the 4th electric capacity (C4), the 4th diode (D4) and the 5th diode (D5); The RESET input pin 4 of the 3 555 chip (U3) is connected power supply VCC3 with power end pin 8, the pin 6 of the 3 555 chip (U3) and pin 2, one end of the 4th electric capacity (C4) connects a stiff end of the 3rd variohm (R30), another stiff end of the 3rd variohm (R30) is connected the convertible tip of second variohm (R29) with convertible tip, two stiff ends of second variohm (R29) connect the anode tap of the 4th diode (D4) and the cathode terminal of the 5th diode (D5) respectively, the cathode terminal of the 4th diode (D4) connects an end of the 25 resistance (R25), the other end of the 25 resistance (R25), the anode tap of the 5th diode (D5) is connected the pin 7 of the 3 555 chip (U3) with an end of the 23 resistance (R23), the other end of the 23 resistance (R23) connects power supply VCC3, the output pin 3 of the 3 555 chip (U3) connects an end of the 24 resistance (R24), the other end of the 24 resistance (R24) connects the cathode terminal of the 8th voltage-stabiliser tube (D8), the input of the input of first logic circuit (1-6) and second logic circuit (1-7), the earth terminal pin 1 of the 3 555 chip (U3), the anode tap ground connection GND-B of the other end of the 4th electric capacity (C4) and the 8th voltage-stabiliser tube (D8).

6, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 2 is characterized in that first logic circuit (1-6) is made up of first NAND gate (U7A), first not gate (U8A); The output of hysteresis voltage comparator circuit (1-5) connects the input pin 1 of first NAND gate (U7A), the output of time base circuit (1-3) connects the input pin 2 of first NAND gate (U7A), the output pin 3 of first NAND gate (U7A) connects on the input pin 1 of first not gate (U8A), and the output pin 2 of first not gate (U8A) connects the input of first on-off circuit (1-8); Second logic circuit (1-7) is made up of second NAND gate (U7B), second not gate (U8B), the 3rd not gate (U8C); The output of hysteresis voltage comparator circuit (1-5) connects the input pin 3 of second not gate (U8B), the output of time base circuit (1-3) connects the input pin 5 of the 3rd not gate (U8C), the output pin 4 of second not gate (U8B) is connected respectively on the input pin 4 and input pin 5 of second NAND gate (U7B) with the output pin 6 of the 3rd not gate (U8C), and the output pin 6 of second NAND gate (U7B) connects the input of second switch circuit (1-9); First on-off circuit (1-8) is made up of first optical coupled switch (U4), the 6th resistance (R6), first light emitting diode (DS1); The first logic circuit 1-6 output connects the input pin 2 of first optical coupled switch (U4), the 6th resistance (R6) of connecting between the input pin 1 of first optical coupled switch (U4) and the negative electrode of first light emitting diode (DS1), the anode of first light emitting diode (DS1) is connected on the power supply VCC4, and the output pin 3 of first optical coupled switch (U4) is connected respectively on two inputs of IGBT circuits for triggering (1-2) with pin 4; Second switch circuit (1-9) is made up of second optical coupled switch (U5), the 22 resistance (R22), second light emitting diode (DS2); Second logic circuit (1-7) output connects the input pin 2 of second optical coupled switch (U5), the 22 resistance (R22) of connecting between the input pin 1 of second optical coupled switch (U5) and the negative electrode of second light emitting diode (DS2), the anode of second light emitting diode (DS2) connects on the power supply VCC4, and the output pin 3 of second optical coupled switch (U5) is connected respectively on two inputs of thyristor gating circuit (1-4) with pin 4.

7, device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 2, the IGBT circuits for triggering (1-2) that it is characterized in that it are by the 2 555 chip (U2), the 11 resistance (R11), second diode (D2), the 12 resistance (R12), first electric capacity (C1), the 4th resistance (R4), the 18 resistance (R18), the 5th resistance (R5), second electric capacity (C2), the 13 resistance (R13), the 4th variable resistance (R28), the 17 resistance (R17), the 15 resistance (R15), first diode (D1), the 16 resistance (R16), the 19 resistance (R19), the tenth voltage-stabiliser tube (D10), the one NPN triode (Q1), the 2nd NPN triode (Q2), the 8th resistance (R8), the 9th resistance (R9), the 3rd diode (D3), PNP triode (Q4), the 7th resistance (R7), the 11 voltage-stabiliser tube (D11), the 9th voltage-stabiliser tube (D9), the 14 resistance (R14), second operational amplifier (U6A) is formed; The pin 2 of the 2 555 chip (U2) is connected with an end of the pin 6 of the 2 555 chip (U2) and the 11 resistance (R11), the other end of the 11 resistance (R11) connects the output pin 4 of first optical coupled switch (U4), the 18 resistance (R18) of connecting between the output pin 4 of first optical coupled switch (U4) and the ground connection GND-C, the pin 4 of the 2 555 chip (U2) connects on the anode of second diode (D2), the negative electrode of second diode (D2) connects power supply VCC5, the 12 resistance (R12) of connecting between IGBT module (Q5) gate terminal of the pin 3 of the 2 555 chip (U2) and main circuit (1-1), the pin 3 of the 2 555 chip (U2) is connected with the pin 7 of the 2 555 chip (U2), first electric capacity (C 1) of connecting between the pin 5 of the 2 555 chip (U2) and the ground connection GND-C, the 4th resistance (R4) of connecting between the pin 7 of the 2 555 chip (U2) and the power supply VCC5, one end of the 13 resistance (R13) connects power supply VCC5, the other end of the 13 resistance (R13) connects a stiff end of the 4th variable resistance (R28) and an end of the 15 resistance (R15), another stiff end ground connection GND-C of the 4th variable resistance (R28), the convertible tip of the 4th variable resistance (R28) connects an end of the 17 resistance (R17), the other end of the 17 resistance (R17) connects the reverse input end pin 4 of second operational amplifier (U6A), the in-phase input end pin 5 of second operational amplifier (U6A) connects the other end of the 15 resistance (R15) and the anode tap of first diode (D1), the cathode terminal of first diode (D1) connects IGBT module (Q5) source terminal of main circuit (1-1), the 16 resistance (R16) of connecting between the power end pin 3 of the output pin 2 of second operational amplifier (U6A) and second operational amplifier (U6A), the output pin 2 of second operational amplifier (U6A) connects an end of the 19 resistance (R19), the other end of the 19 resistance (R19) is connected with the negative electrode of the tenth voltage-stabiliser tube (D10), the anode of the tenth voltage-stabiliser tube (D10) connects the base stage of the 2nd NPN triode (Q2) and the base stage of a NPN triode (Q1), the colelctor electrode of the 2nd NPN triode (Q2) connects an end of the 5th resistance (R5), one end of one end of second electric capacity (C2) and the 8th resistance (R8), the other end of the 8th resistance (R8) is connected power supply VCC5 with the other end of the 5th resistance (R5), the other end ground connection GND-C of second electric capacity (C2), the colelctor electrode of the one NPN triode (Q1) connects an end of the 9th resistance (R9) and the cathode terminal of the 3rd diode (D3), the other end of the 9th resistance (R9) connects power supply VCC5, the anode tap of the 3rd diode (D3) connects on the base stage of PNP triode (Q4), the colelctor electrode of PNP triode (Q4) connects the negative electrode of the 11 voltage-stabiliser tube (D11), one end of the 7th resistance (R7), IGBT module (Q5) drain electrode end of one end of the 14 resistance (R14) and main circuit (1-1), the other end of the 14 resistance (R14) connects the 9th voltage-stabiliser tube (D9) cathode terminal, the emitter stage of PNP triode (Q4) connects on the anode of the 9th voltage-stabiliser tube (D9), the negative electrode of the 9th voltage-stabiliser tube (D9) connects IGBT module (Q5) gate terminal of main circuit (1-1), the earth terminal pin 1 of the 2 555 chip (U2), the earth terminal pin 1 of second operational amplifier (U6A), the anode of the 11 voltage-stabiliser tube (D11), the grounded emitter GND-C of the emitter stage of the one NPN triode (Q1) and a NPN triode (Q1), the pin 8 of the 2 555 chip (U2), the output pin 3 of second optical coupled switch (U5), the power end pin 3 of second operational amplifier (U6A), the other end of the 7th resistance (R7) is connected power supply VCC5 with the other end of the 9th resistance (R9).

8, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 2 is characterized in that its thyristor gating circuit (1-4) is made up of the 21 resistance (R21), the 20 resistance (R20), the 26 resistance (R26), the 3rd electric capacity (C3), the 3rd NPN triode (Q3); The 21 resistance (R21) of connecting between the pin 3 of second optical coupled switch (U5) and the power supply VCC6, the 20 resistance (R20) of connecting between the control utmost point of power supply VCC6 and controllable silicon (Q6), the 26 resistance (R26) of connecting between the output pin 4 of second optical coupled switch (U5) and the earth terminal GND-D, the two ends of 26 resistance (R26) that the 3rd electric capacity (C3) is connected in parallel on, the base stage of the 3rd NPN triode (Q3) connects on the output pin 4 of second optical coupled switch (U5), the grounded emitter of the 3rd NPN triode (Q3), the colelctor electrode of the 3rd NPN triode (Q3) connects the cathode terminal of controllable silicon (Q6).

9, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 1 is characterized in that coil (2) center is 25～45mm to welding gun (7) centre distance (L1).

10, the device with weldering electromagnetic impact control HOT CRACK FOR WELDING P and distortion according to claim 1 is characterized in that it has increased by first coil (2-1), second coil (2-2) and first pulse discharge circuit (1-10); Two outputs of first pulse discharge circuit (1-10) connect an end of first coil (2-1) and an end of second coil (2-2) respectively, the other end of first coil (2-1) is connected to the other end of second coil (2-2), first coil (2-1) and second coil (2-2) symmetry respectively are positioned over top, weld seam (3) both sides, the center of first coil (2-1) and second coil (2-2) is 20～30mm apart from weld seam (3) distance between center line (L3) respectively, the vertical distance at centre-to-centre spacing welding gun (7) center of first coil (2-1) and second coil (2-2) is that (L4) is 25～35mm, and the centre distance (L5) of the centre-to-centre spacing welding gun (7) of coil (2) is 45～60mm.