A welding seam forming regulation method based on three-magnetic-pole magnetic control arc double-side front and back swing

Abstract

The application discloses a welding seam forming regulation and control method based on three-magnetic-pole magnetic control electric arc double-side front and back swing, which adopts a device including a first excitation coil (1) surrounding a welding gun, a second excitation coil (2) distributed on the left side of the welding gun, a third excitation coil (3) distributed on the right side of the welding gun, a first excitation power supply (4), a second excitation power supply (5), a third excitation power supply (6), a welding seam forming controller (7) and a magnetic field feedback system (8). The method adopts three excitation coils to generate symmetrical mirror transverse magnetic fields along the welding direction on the left and right sides of the welding arc. The mirror transverse magnetic fields generate electromagnetic swing with opposite directions of action on the left and right sides of the welding arc plasma, so as to regulate and control the stirring action of the arc on the left and right sides of the welding pool and the liquid metal backflow action on the front and back ends of the welding pool, and then regulate and control the welding seam forming effect. The application can effectively eliminate welding defects such as hump and undercut, improve the welding seam quality and welding efficiency, and is suitable for welding seam quality control of various weldings.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic control welding, and particularly relates to a mirror image transverse magnetic field controlled arc method, which is especially suitable for a welding seam forming regulation method based on a three-magnetic-pole mirror image transverse magnetic field controlled arc double-sided front and back swing. BACKGROUND

[0002] Arc plasma has conductivity. Under the action of different types of external magnetic fields, the shape, spatial position and arc movement characteristics of the arc will change, thereby changing the arc behavior, affecting the droplet transfer process, reducing spatter, and also having an important influence on the molten pool flow. Specifically, the external longitudinal magnetic field and the transverse magnetic field can deflect the arc to one side; the axial magnetic field can change the arc shape and compress the arc; the rotating magnetic field can drive the synchronous rotation of the arc, leading to obvious changes in shape and position; the function of the sharp corner magnetic field is to change the arc morphology from a cone to a flat cone, and the circular cross section of the arc changes into an elliptical shape, achieving the purpose of stretching and compression.

[0003] The technology of using various types of magnetic fields to control welding arcs has a history of several years. It can effectively solve various welding defects such as undercut, hump weld, porosity and cracks that occur during welding, and further obtain the desired weld forming effect by changing the arc shape. In practice, different types of magnetic fields are selected according to the specific welding scene and use requirements, and the weld forming effect is controlled by changing the magnetic field strength and magnetic pole distribution and other welding parameters. Among the above types of magnetic fields, the sharp corner magnetic field is suitable for scenarios with less directional demand for welding, such as welding of steel plates with small curvature, etc., and the applicable scenarios are limited; the rotating magnetic field is difficult to control due to high operation requirements in practice. Therefore, the current research in the field of magnetic control arc welding mainly focuses on axial magnetic field, transverse magnetic field and longitudinal magnetic field.

[0004] For the problem of applying magnetic control arc to weld tracking, patent document CN105149738B provides a bidirectional magnetic control arc weld tracking sensor. The sensor controls the welding arc through a spatial bidirectional magnetic field, wherein the axial magnetic field and the transverse magnetic field simultaneously act on the welding arc. The axial magnetic field enhances the contraction degree and stability of the arc, and the transverse alternating magnetic field makes the welding arc swing horizontally in a regular manner. According to the change of the arc length, the current signal change caused by the arc length change is used to obtain more accurate weld information. For the problem of welding collapse in the aluminum alloy laser-MIG hybrid welding process, patent document CN113102891B provides a method and device for suppressing aluminum alloy laser-MIG hybrid welding collapse by applying a magnetic field. A transverse magnetic field perpendicular to the weld is arranged at the weld to be welded. The electromagnetic force generated by the interaction between the magnetic field and the flowing conductive molten pool fluid forms a lifting force on the back of the weld, effectively suppressing the aluminum alloy welding collapse.

[0005] The above patent solutions effectively improve the welding effect by using an external magnetic field, but still have some deficiencies: first, the effect of the combination of multiple magnetic fields is not clear, and the effect of a single type of magnetic field is emphasized, making it difficult to efficiently utilize the effect and advantages of combined magnetic fields; second, the above patent documents have limited weld forming effect improvement, and single-axis or transverse magnetic field has poor stirring effect on the molten pool, making it difficult to achieve the desired weld forming effect; finally, the two magnetic poles of the above transverse magnetic field are mostly different, and the range of action is the entire welding arc, which is not flexible enough for local control of the arc. SUMMARY

[0006] The present application improves the problems in the above patent solutions, and the main purpose is to provide a weld forming control method based on three-magnetic-pole magnetic control arc bilateral front and rear swing, which generates a mirror transverse magnetic field through three excitation coils, and then naturally divides the welding arc into left and right areas, the swing directions of the two areas are opposite due to the influence of the magnetic field, thereby optimizing the stirring effect and further achieving the desired weld forming effect by local control of the arc.

[0007] The present application provides a weld forming control method based on three-magnetic-pole magnetic control arc bilateral front and rear swing, which is realized by the following technical solutions:

[0008] The present application relates to a method for controlling an arc with a mirror transverse magnetic field, and the device used mainly includes a first excitation coil surrounding a welding torch, a second excitation coil distributed on the left side of the welding torch, a third excitation coil distributed on the right side of the welding torch, a first excitation power supply, a second excitation power supply, a third excitation power supply, and a weld forming controller. The three excitation coils generate a mirror transverse magnetic field that is symmetrically distributed along the welding direction on the left and right sides of the welding arc. The mirror transverse magnetic field produces electromagnetic swing in opposite directions on the left and right sides of the welding arc plasma, thereby controlling the stirring effect of the arc on the left and right sides of the welding pool and the liquid metal backflow effect on the front and rear ends of the welding pool, and further controlling the weld forming effect.

[0009] Further, the magnetic fields generated by the second excitation coil and the third excitation coil have the same polarity, and the magnetic field generated by the first excitation coil has a different polarity from the magnetic fields generated by the second excitation coil and the third excitation coil, thereby generating a mirror magnetic field effect with the welding direction as the center line.

[0010] The specific working process of the control method is as follows:

[0011] The second excitation coil, the first excitation coil and the third excitation coil are distributed in the time period T with the magnetic pole polarity of S-N-S and N-S-N alternately changing, for example, in the negative polarity of the welding current, at 0-T / 2, the second excitation coil, the first excitation coil and the third excitation coil are respectively connected with the excitation current of -I2, I1 and -I3, so that the mirror image transverse magnetic field with the magnetic pole polarity of S-N-S and symmetrically distributed along the welding direction is formed in the welding arc space, the magnetic field distribution between the second excitation coil and the first excitation coil produces the electromagnetic swing of the action direction to the back of the arc plasma on the left side of the welding arc, the magnetic field distribution between the third excitation coil and the first excitation coil produces the electromagnetic swing of the action direction to the front of the arc plasma on the right side of the welding arc, at this time, the mirror image transverse magnetic field drives the arc to produce the stirring action of the left back and the right front of the welding pool and the clockwise pool flow field distribution; at T / 2-T, the second excitation coil, the first excitation coil and the third excitation coil are respectively connected with the excitation current of I2, -I1 and I3, so that the mirror image transverse magnetic field with the magnetic pole polarity of N-S-N and symmetrically distributed along the welding direction is formed in the welding arc space, the magnetic field distribution between the second excitation coil and the first excitation coil produces the electromagnetic swing of the action direction to the front of the arc plasma on the left side of the welding arc, the magnetic field distribution between the third excitation coil and the first excitation coil produces the electromagnetic swing of the action direction to the back of the arc plasma on the right side of the welding arc, at this time, the mirror image transverse magnetic field drives the arc to produce the stirring action of the left front and the right back of the welding pool and the clockwise pool flow field distribution; taking T as the time period, the second excitation coil, the first excitation coil and the third excitation coil alternately change according to the above process with the magnetic pole polarity of S-N-S and N-S-N, the mirror image transverse magnetic field alternately acts on the welding arc to produce the periodic electromagnetic swing and the periodic stirring action and flow field distribution evolution of the pool flow field, so as to control the weld forming effect.

[0012] The beneficial effects of the present application are as follows: (1) The added axial magnetic field not only compresses the arc, but also acts as one of the magnetic poles of the transverse magnetic field, so the magnetic field action area is naturally divided into left and right areas along the welding direction, further improving the local control ability of the magnetic field on the arc and better adapting to special welding scenes. (2) The mirror image transverse magnetic field generated by the three excitation coils can make the welding arc produce different tearing effects, the present application fully utilizes the advantages of the mirror image transverse magnetic field, greatly improves the stirring action of the left and right sides of the welding pool and the liquid metal backflow action of the front and back ends of the welding pool, and further controls the weld forming effect. (3) Due to the space position and role of the axial magnetic field, the present application can fully utilize the limited space of the magnetic field generating device under the premise of completing the welding task, and further reduce the device volume. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1is a system flow schematic diagram of the three-magnetic-pole magnetic control arc double-sided front and rear swing weld forming regulation method described in the application;

[0014] Figure 2 is a force schematic diagram of the welding arc under the action of the mirror image transverse magnetic field at 0-T / 2 in embodiment 1, wherein the black solid arrow indicates the distribution direction of the magnetic force line of the magnetic field, and the white hollow arrow indicates the direction of the electromagnetic force;

[0015] Figure 3 is a force schematic diagram of the welding arc under the action of the mirror image transverse magnetic field at T / 2-T in embodiment 1, wherein the black solid arrow indicates the distribution direction of the magnetic force line of the magnetic field, and the white hollow arrow indicates the direction of the electromagnetic force;

[0016] Figure 4 is a principle schematic diagram at 0-T / 2 in embodiment 1;

[0017] Figure 5 is a principle schematic diagram at T / 2-T in embodiment 1;

[0018] Figure 6 is a force schematic diagram of the welding arc under the action of the mirror image transverse magnetic field at 0-T / 2 in embodiment 2, wherein the black solid arrow indicates the distribution direction of the magnetic force line of the magnetic field, and the white hollow arrow indicates the direction of the electromagnetic force;

[0019] Figure 7 is a force schematic diagram of the welding arc under the action of the mirror image transverse magnetic field at T / 2-T in embodiment 2, wherein the black solid arrow indicates the distribution direction of the magnetic force line of the magnetic field, and the white hollow arrow indicates the direction of the electromagnetic force;

[0020] Figure 8 is a principle schematic diagram at 0-T / 2 in embodiment 2;

[0021] Figure 9 is a principle schematic diagram at T / 2-T in embodiment 2. DETAILED DESCRIPTION

[0022] In order to better express the embodiments and specific effects of the application, the embodiments of the application will be further described below in combination with the drawings and examples.

[0023] Embodiment 1: The embodiment of the application proposes a weld forming regulation method based on a three-magnetic-pole magnetic control arc double-sided front and rear swing, which adopts three excitation coils to generate mirror image transverse magnetic fields symmetrically distributed along the welding direction on the left and right sides of the welding arc, and through the mirror image transverse magnetic fields, electromagnetic swings in opposite directions are generated on the left and right sides of the welding arc plasma, so as to regulate the stirring action of the arc on the left and right sides of the welding pool and the liquid metal backflow action at the front and rear ends of the welding pool, and then regulate the weld forming effect.

[0024] The system flow diagram of the regulation method is as shown in Figure 1 The specific operation steps are as follows:

[0025] Step 1: According to the welding environment, the parameters of the weld forming controller (7) are pre-adjusted to ensure that all excitation power supplies can work stably and basically complete the welding work.

[0026] Step 2: Fix the magnetic field generating device on the welding torch, adjust the position and posture of the welding torch to make the welding process proceed normally, and start the arc after the preparation work is completed.

[0027] Step 3: Start the three excitation power supplies at the same time after starting the welding, and control the three excitation coils to generate mirror image transverse magnetic fields symmetrically distributed along the welding direction on the left and right sides of the welding arc. The mirror image transverse magnetic field pulls the front and back swing on both sides of the arc with T as the time period, and the arc continuously changes the stirring direction, thereby regulating the weld formation.

[0028] Step 4: The magnetic field feedback system (8) receives the deviation signal of the magnetic field generated by the three excitation coils, further adjusts the weld forming controller (7), changes the excitation current and excitation frequency of the three excitation coils, and makes the coils generate appropriate magnetic field strength to better form the required mirror image transverse magnetic field.

[0029] Step 5: The magnetic field feedback system (8) and the weld forming controller (7) work in a cycle until the welding is completed and the work is stopped.

[0030] The three excitation power supplies in step 2 include a first excitation power supply (4), a second excitation power supply (5), and a third excitation power supply (6). The first excitation power supply (4) controls the first excitation coil (1), the second excitation power supply (5) controls the second excitation coil (2), and the third excitation power supply (6) controls the third excitation coil (3). The three excitation coils include the first excitation coil (1) surrounding the welding torch, the second excitation coil (2) distributed on the left side of the welding torch, and the third excitation coil (3) distributed on the right side of the welding torch. The magnetic field generated by the second excitation coil (2) and the third excitation coil (3) has the same polarity, and the magnetic field generated by the first excitation coil (1) has a different polarity from the magnetic fields generated by the second excitation coil (2) and the third excitation coil (3).

[0031] The welding process in step 3 works in negative polarity of welding current, and the specific process of the mirror transverse magnetic field pulling the front and back swing of the arc on both sides with T as the time period is as follows: at 0-T / 2, the second excitation coil (2), the first excitation coil (1), and the third excitation coil (3) are respectively connected with -I2, I1, and -I3 excitation current, so as to form a mirror transverse magnetic field with magnetic pole polarity of S-N-S and symmetrical distribution along the welding direction in the welding arc space, the magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) produces electromagnetic swing of the action direction to the rear of the arc plasma on the left side of the welding arc, the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) produces electromagnetic swing of the action direction to the front of the arc plasma on the right side of the welding arc, and the force diagram of the arc is as shown in Figure 2 The mirror transverse magnetic field at this time drives the arc to produce left and right stirring effects on the welding pool and counterclockwise pool flow field distribution, and the specific principle diagram is as shown in Figure 4 At T / 2-T, the second excitation coil (2), the first excitation coil (1), and the third excitation coil (3) are respectively connected with I2, -I1, and I3 excitation current, so as to form a mirror transverse magnetic field with magnetic pole polarity of N-S-N and symmetrical distribution along the welding direction in the welding arc space, the magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) produces electromagnetic swing of the action direction to the front of the arc plasma on the left side of the welding arc, the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) produces electromagnetic swing of the action direction to the rear of the arc plasma on the right side of the welding arc, and the force diagram of the arc is as shown in Figure 3 The mirror transverse magnetic field at this time drives the arc to produce left and right stirring effects on the welding pool and counterclockwise pool flow field distribution, and the specific principle diagram is as shown in Figure 5 The mirror transverse magnetic field at this time drives the arc to produce left and right stirring effects on the welding pool and counterclockwise pool flow field distribution, and the specific principle diagram is as shown in

[0032] In example 2, the second excitation coil (2) is distributed in the front side of the welding gun, the third excitation coil (3) is distributed in the rear side of the welding gun, and the first excitation coil (1) is unchanged and still distributed around the welding gun, thereby forming the distribution of the excitation coils in front, middle, and rear. The three excitation coils generate a mirror transverse magnetic field with symmetrical distribution along the axis perpendicular to the welding direction on both sides of the welding arc, and the action direction of the mirror transverse magnetic field on the arc plasma on both sides of the welding arc is opposite, and the system flow of the control method is the same as that of example 1.

[0033] The welding process works with negative polarity of welding current, the mirror transverse magnetic field swings left and right with T as time period, the specific process is as follows: at 0-T / 2, the second excitation coil (2), the first excitation coil (1), the third excitation coil (3) are respectively connected with -I2, I1, -I3, so that the mirror transverse magnetic field with magnetic pole polarity of S-N-S and symmetrical distribution along the axis perpendicular to the welding direction is formed in the welding arc space, the magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) produces left electromagnetic swing to the front side of the welding arc plasma, the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) produces right electromagnetic swing to the back side of the welding arc plasma, the force diagram of the arc is as shown in Figure 6 The mirror transverse magnetic field drives the arc to produce front left and back right stirring effect on the welding pool and counterclockwise pool flow field distribution, the specific principle diagram is as shown in Figure 8 At T / 2-T, the second excitation coil (2), the first excitation coil (1), the third excitation coil (3) are respectively connected with I2, -I1, I3, so that the mirror transverse magnetic field with magnetic pole polarity of N-S-N and symmetrical distribution along the axis perpendicular to the welding direction is formed in the welding arc space, the magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) produces right electromagnetic swing to the front side of the welding arc plasma, the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) produces left electromagnetic swing to the back side of the welding arc plasma, the force diagram of the arc is as shown in Figure 7 The mirror transverse magnetic field drives the arc to produce front right and back left stirring effect on the welding pool and clockwise pool flow field distribution, the specific principle diagram is as shown in Figure 9 With T as time period, the second excitation coil (2), the first excitation coil (1), the third excitation coil (3) change the distribution of magnetic pole polarity of S-N-S and N-S-N alternately according to the above process, through the alternating effect of the mirror transverse magnetic field, the welding arc is produced periodic electromagnetic swing and the pool flow field is produced periodic stirring effect and flow field distribution evolution, so as to regulate the weld forming effect.

[0034] The present application is not limited to the above preferred embodiments, on the basis of the experimental device and method described in the present application, various modifications and changes can be made, any change, modification, replacement, combination, simplification and the like made according to the spirit and principle of the technical scheme of the present application are equivalent replacement ways, all these modifications and changes are within the protection scope of the present application.

Claims

1. A method for controlling the formation of a weld based on a three-pole magnetron electric arc with double-sided front and rear swinging, characterized in that: The device used in the method comprises a first excitation coil (1) surrounding the welding gun, a second excitation coil (2) distributed on the left side of the welding gun, a third excitation coil (3) distributed on the right side of the welding gun, a first excitation power supply (4), a second excitation power supply (5), a third excitation power supply (6), a weld forming controller (7), and a magnetic field feedback system (8), wherein the magnetic fields generated by the second excitation coil (2) and the third excitation coil (3) have the same polarity, and the magnetic field generated by the first excitation coil (1) has a polarity different from that of the magnetic fields generated by the second excitation coil (2) and the third excitation coil (3); the method uses three excitation coils to generate mirror image transverse magnetic fields that are symmetrically distributed along the welding direction on the left and right sides of the welding arc, and the mirror image transverse magnetic fields generate electromagnetic oscillations in opposite directions on the left and right sides of the welding arc plasma, so as to control the stirring action of the arc on the left and right sides of the welding pool and the liquid metal backflow action at the front and back ends of the welding pool, and further control the weld forming effect; the working process of the three-magnetic-pole magnetic control arc bilateral front and back oscillation weld forming control method is as follows: The second excitation coil (2), the first excitation coil (1), and the third excitation coil (3) alternately change their magnetic pole polarities (SNS and NSN) within a period of T. When the welding current is negative, the specific working process is as follows: During the period from 0 to T / 2, the second excitation coil (2), the first excitation coil (1), and the third excitation coil (3) are supplied with excitation currents of -I2, I1, and -I3, respectively, thereby forming a mirror transverse magnetic field with magnetic pole polarities of SNS and symmetrically distributed along the welding direction in the welding arc space. The magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) generates an electromagnetic oscillation in the direction of action backward on the arc plasma on the left side of the welding arc, and the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) generates an electromagnetic oscillation in the direction of action forward on the arc plasma on the right side of the welding arc. At this time, the mirror transverse magnetic field drives the arc to generate a stirring effect on the weld pool from the left rear and the right front and a counterclockwise flow field distribution in the weld pool; During the period from T / 2 to T, the second excitation coil (2), the first excitation coil (1), and the third excitation coil (3) alternately change their magnetic pole polarities (SNS and NSN) within a period of T, thereby forming a mirror transverse magnetic field with magnetic pole polarities of SNS and symmetrically distributed along the welding direction. (1) The third excitation coil (3) is supplied with excitation currents I2, -I1, and I3 respectively, thereby forming a mirror transverse magnetic field with magnetic pole polarity NSN and symmetrically distributed along the welding direction in the welding arc space. The magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) generates an electromagnetic oscillation in the forward direction on the arc plasma on the left side of the welding arc, and the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) generates an electromagnetic oscillation in the backward direction on the arc plasma on the right side of the welding arc. At this time, the mirror transverse magnetic field drives the arc to generate a stirring effect on the welding pool in the left front and right rear and a clockwise flow field distribution in the weld pool. With T as the time period, the second excitation coil (2), the first excitation coil (1), and the third excitation coil (3) alternately change with magnetic pole polarity SNS and NSN according to the above process. Through the alternating effect of the mirror transverse magnetic field, the welding arc generates periodic electromagnetic oscillation and the weld pool flow field generates periodic stirring effect and flow field distribution evolution, thereby controlling the weld formation effect.

2. A welding seam forming regulation method based on a three-magnetic-pole magnetic control electric arc double-side left-right swing, characterized in that: The device used in the method comprises a first excitation coil (1) surrounding the welding gun, a second excitation coil (2) distributed on the front side of the welding gun, a third excitation coil (3) distributed on the back side of the welding gun, a first excitation power supply (4), a second excitation power supply (5), a third excitation power supply (6), a weld forming controller (7), and a magnetic field feedback system (8), wherein the magnetic fields generated by the second excitation coil (2) and the third excitation coil (3) have the same polarity, and the magnetic field generated by the first excitation coil (1) has a polarity different from that of the magnetic fields generated by the second excitation coil (2) and the third excitation coil (3); the method uses three excitation coils to generate mirror image transverse magnetic fields that are symmetrically distributed along the axis perpendicular to the welding direction on the front and back sides of the welding arc, and the mirror image transverse magnetic fields generate electromagnetic oscillations in opposite directions on the front and back sides of the welding arc through the arc plasma, so as to regulate and control the stirring action of the arc on the front and back sides of the welding pool and the liquid metal backflow action on the left and right ends of the welding pool, and further regulate and control the weld forming effect; the working process of the three-magnetic-pole magnetic control arc bilateral left-right oscillation weld forming regulation and control method is as follows: The second excitation coil (2), the first excitation coil (1) and the third excitation coil (3) are alternately changed in the time period T with the magnetic pole polarity of S-N-S and N-S-N, and when the welding current is negative, the specific working process is as follows: at 0-T / 2, the second excitation coil (2), the first excitation coil (1) and the third excitation coil (3) are respectively connected with the excitation current of -I2, I1 and -I3, so as to form the mirror image transverse magnetic field with the magnetic pole polarity of S-N-S and the axis symmetrical distribution perpendicular to the welding direction in the welding arc space, the magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) produces the electromagnetic swing of the left direction to the welding arc front side arc plasma, the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) produces the electromagnetic swing of the right direction to the welding arc rear side arc plasma, at this time, the mirror image transverse magnetic field drives the arc to produce the stirring action of the front left and the rear right and the clockwise molten pool flow field distribution to the welding molten pool; at T / 2-T, the second excitation coil (2), the first excitation coil (1) and the third excitation coil (3) are respectively connected with the excitation current of I2, -I1 and I3, so as to form the mirror image transverse magnetic field with the magnetic pole polarity of N-S-N and the axis symmetrical distribution perpendicular to the welding direction in the welding arc space, the magnetic field distribution between the second excitation coil (2) and the first excitation coil (1) produces the electromagnetic swing of the right direction to the welding arc front side arc plasma, the magnetic field distribution between the third excitation coil (3) and the first excitation coil (1) produces the electromagnetic swing of the left direction to the welding arc rear side arc plasma, at this time, the mirror image transverse magnetic field drives the arc to produce the stirring action of the front right and the rear left and the counterclockwise molten pool flow field distribution to the welding molten pool; with T as the time period, the second excitation coil (2), the first excitation coil (1) and the third excitation coil (3) are alternately changed in the magnetic pole polarity of S-N-S and N-S-N according to the above process, the periodic electromagnetic swing of the welding arc and the periodic stirring action and flow field distribution evolution of the molten pool flow field are produced to the welding arc through the alternating action of the mirror image transverse magnetic field, so as to regulate the welding forming effect.

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