A method for regulating the orientation of the front and back ends of a welding arc in a dual-pole combined magnetic field

Abstract

The application discloses a kind of double magnetic pole combination magnetic field control welding arc front and rear end directional deviation regulation and control method, this method adopts by arc welding torch, welding torch axial magnetic field generating device, external longitudinal magnetic field generating device composition welding system is completed to the directional deviation regulation and control of welding arc front or rear end, welding torch axial magnetic field generating device and the magnetic field generated by external longitudinal magnetic field generating device jointly form combination magnetic field, and the combination magnetic field produces local deflection to arc.The application can effectively improve the ability of magnetic field generating device to control arc, further control the stirring effect of molten pool to improve the weld formation, solve the problem that the regulation and control effect and mode are not high in the existing magnetic control arc method.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of magnetic control welding, and particularly relates to a method for controlling an electric arc through two magnetic field combinations, and is particularly suitable for a method for regulating and controlling directional deviation of front and rear ends of a welding electric arc through a combination of a double magnetic pole axial magnetic field and a longitudinal magnetic field. BACKGROUND

[0002] Magnetic control arc welding technology is an advanced welding technology that uses electromagnetic induction principle to regulate and control the shape and movement of an electric arc through electromagnetic interaction between an external magnetic field and the electric arc. Research has found that the external magnetic field changes the shape of the electric arc, i.e., changes the size and position of the heated area of the base material, thereby affecting the melting of the base material and the formation of the weld, improving the liquid metal phase change process and the grain crystallization direction, and ultimately playing a role in refining the grains, reducing segregation, and improving the mechanical properties of the weld. Because the magnetic control arc has a significant effect on improving the weld formation, it has attracted the attention of many welding researchers in recent years.

[0003] Under the action of different types of external magnetic fields, the shape, spatial position, and characteristics of the electric arc movement change differently, and these electric arc behaviors have an important influence on the molten pool flow and weld formation. Applying a traditional transverse magnetic field, i.e., the direction of the magnetic field lines of the external magnetic field is perpendicular to the electric arc axis and the welding direction, will cause the electric arc to deviate to one side, thereby changing the molten pool flow, but the range of changing the electric arc shape is relatively fixed, and it is difficult to change the welding effect according to the welding scene and actual requirements; applying a traditional axial magnetic field, i.e., the magnetic field generated by a coaxial excitation coil installed around the electrode, the direction of the magnetic potential is parallel to the electric arc axis, which can significantly change the electric arc shape and compress the electric arc, but it basically does not change the position of the electric arc axis, and the regulation effect is limited.

[0004] In view of the problem of controlling the directional deviation of the welding electric arc by the transverse magnetic field, patent document CN113263246B discloses a magnetic control welding device based on alternating magnetic field, which generates a transverse magnetic field through magnetic control probes located on both sides of the welding torch, so that the molten pool flows to both sides while flowing along the weld, thereby avoiding the problem of excessive excess height caused by the solidification of the molten pool. In view of the problem of controlling the electric arc shape compression by the axial magnetic field, patent document CN113042860A discloses a high-frequency longitudinal magnetic field generating device for magnetic control welding, which forms an axial high-frequency magnetic field through a few-turn excitation coil, so that the magnetic induction intensity of the high-frequency magnetic field is smoothly output. Under the action of electromagnetic force, the compression effect of the welding electric arc is more obvious, and the electric arc energy density is more concentrated.

[0005] The patent solutions above can effectively improve the welding effect and are suitable for respective welding scenes, but still have the following shortcomings: firstly, the applicable scene of single magnetic field is limited, the above-mentioned transverse magnetic field can reduce the weld reinforcement while suppressing welding defects, but it is difficult to concentrate the arc to ensure the appropriate penetration, and the above-mentioned axial magnetic field can better compress the arc to ensure heat concentration, but the stirring effect on the molten pool is poor; secondly, the magnetic field regulation effect is macroscopic, which changes the overall shape of the welding arc, and is not suitable for welding scenes with high requirements; finally, the magnetic field generating device is complex, the connecting part is too large, and the water cooling device and the connecting part are not tightly matched, which may cause overheating and loss of the excitation coil. SUMMARY

[0006] The present application improves the problems in the above-mentioned patent documents, and makes improvements for the problems of heat concentration and arc shape not meeting the requirements in the arc welding process. On the basis of the existing magnetic control arc theory and research, a regulation method for controlling the directional deviation of the front and rear ends of the welding arc by a double magnetic pole combined magnetic field is proposed. The local transverse magnetic field formed by the external longitudinal magnetic field and the axial magnetic field is used to control the shape of the welding arc, thereby producing a local deflection effect and an arc compression effect, which greatly increases the arc regulation ability of the magnetic field generating device. According to the principle of electromagnetic induction, the excitation coil produces periodic directional deviation at the local position of the welding arc under the action of alternating current, which causes the local stirring of the welding pool to increase, thereby changing the weld forming effect.

[0007] In order to more flexibly and efficiently regulate the arc shape, further regulate the stirring effect of the molten pool to improve the weld forming, and solve the problem that the regulation effect and method in the existing magnetic control arc method are not high in applicability, the arc deviation regulation method proposed by the present application is implemented by the following technical solutions: the present application relates to two kinds of magnetic field combination control arc method, the combination magnetic field generated by the welding gun axial magnetic field generating device and the external longitudinal magnetic field generating device controls the local periodic directional deviation of the welding arc, the two kinds of magnetic field generating devices are connected through a four-hole rectangular fixed plate to ensure that the axes of the generating devices are parallel and the device main bodies are at the same height.

[0008] Further, the welding gun axial magnetic field generating device is composed of a welding gun sleeve, an axial excitation coil and a water cooling channel. The welding gun sleeve can completely accommodate the arc welding gun including the shielding gas nozzle, and the sleeve is fastened with the welding gun by welding gun fastening bolts. The axial excitation coil is wound on the sleeve in a dense manner by using a common layer winding method. The two ends of the axial excitation coil are connected with an excitation power supply to generate an axial magnetic field acting on the welding arc.

[0009] Further, the external longitudinal magnetic field generating device is composed of an external core, an external core sleeve, a longitudinal excitation coil and a water cooling channel, the external core is directly made of soft magnetic materials such as pure electrical iron or iron-silicon alloy, ferrite, etc., the material cost is low, and the external core has the advantages of low coercive force and high magnetic permeability; the external core sleeve is relatively small in size compared with the welding gun sleeve, and the central through hole can completely contain the core; the longitudinal excitation coil is similar to the above-mentioned axial excitation coil and is layer-wound on the sleeve to generate a longitudinal magnetic field acting on the welding arc.

[0010] The water cooling channel mentioned in the welding gun axial magnetic field generating device and the external longitudinal magnetic field generating device is designed in an integrated manner, has a simple and light structure, saves space, and has a double U-shaped design of two layers, the cooling water channel enters from the upper boss of the welding gun sleeve, passes through the upper boss of the external core sleeve and then extends from the welding gun sleeve, and has a U-shaped cooling effect, similarly, the lower boss also has such a U-shaped cooling effect, so that the eddy current heat generated by the coil can be effectively absorbed, and the coil loss failure can be avoided.

[0011] The application provides a double-magnetic-pole combined magnetic field control welding arc front and rear end directional deviation adjusting and controlling method.

[0012] Firstly, the fixed position of the external longitudinal magnetic field generating device is selected according to the actual demand of the weld forming, when the external longitudinal magnetic field generating device is fixed at the rear end of the welding gun axial magnetic field generating device, the rear end of the electric arc can be deviated directionally, the fluid flow process and the solidification process of the tail part of the molten pool can be affected, the tail part of the molten pool can be obviously and evenly spread, the generation of weld cracks and bubbles can be reduced, and the weld forming can be improved; when the external longitudinal magnetic field generating device is fixed at the front end of the welding gun axial magnetic field generating device, the front end of the electric arc can be deviated directionally, the range of the weld heat affected zone is changed, the weld forming parameters including the weld penetration and the weld width are changed, the weld penetration is reduced, the weld width is increased, and the method can be suitable for special welding scenes.

[0013] Taking the case that the external longitudinal magnetic field generating device is fixed at the rear end of the welding gun axial magnetic field generating device as an example, the excitation current and the excitation frequency of the excitation power source are set in advance, so that the magnetic fields generated by the longitudinal excitation coil and the axial excitation coil interact to form a suitable combined magnetic field, and the specific parameter adjustment needs to be tested according to the welding material and the scene, the size of the additional electromagnetic force perpendicular to the welding direction is obtained through the test calculation, and then the excitation parameters are adjusted to control the degree and the influence range of the directional deflection of the tail part of the electric arc.

[0014] The size of the additional electromagnetic force perpendicular to the welding direction can be represented as F=B x j, wherein B is the magnetic field distribution of a point in the welding area, and j is the current density of the point in the welding area. For the magnetic field distribution B of a point, the influence of temperature on the magnetic permeability in space is ignored, the three components of the magnetic induction intensity of the point can be obtained according to the relationship between the magnetic potential space component and the magnetic induction intensity. Wherein A is magnetic potential, the magnetic field distribution B thus obtained presents a trend from big to small from the center of the weld to both sides. For a certain point current density j, according to theoretical derivation and simulation, the current density on the cross section at any height in the arc presents a Gaussian distribution, which can be expressed as: Wherein I is welding current, d is arc distribution coefficient, σ c is current density distribution coefficient, and r is the radius of the point. By adjusting the welding current and other welding parameters to meet the use requirements through the theoretical value and actual deflection test effect.

[0015] Further, when the formal welding is started, the welding gun successfully ignites the arc and then starts welding along the welding direction, at this time, the two excitation coils start to work through alternating current, the longitudinal excitation coil and the axial excitation coil are distributed with magnetic pole polarity N-S and S-N in the period T, and the water cooling system simultaneously cools the coils. Taking the direct current positive connection as an example, at 0-T / 2, the longitudinal excitation coil and the axial excitation coil are respectively connected with I1 and -I2 excitation current, so that the combination magnetic field of N-S magnetic pole polarity distribution and left directional offset of the rear end of the welding arc is generated in the welding arc space; at T / 2-T, the longitudinal excitation coil and the axial excitation coil are respectively connected with -I1 and I2 excitation current, so that the combination magnetic field of S-N magnetic pole polarity distribution and right directional offset of the rear end of the welding arc is generated in the welding arc space. Through the magnetic pole polarity transformation and the ampere force direction transformation with the period T, the rear end of the welding arc is periodically directional offset, the liquid metal is uniformly spread, the momentum of the rear liquid flow in the molten pool is reduced, the liquid metal accumulation is avoided, the hump defects are avoided, and the weld is smooth and beautiful. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 It is a flow chart of the regulation and control method of the double magnetic pole combination magnetic field for controlling the directional offset of the front and rear ends of the welding arc.

[0017] Figure 2 It is a structural schematic diagram of the double magnetic pole combination magnetic field generating device.

[0018] Figure 3 It is a cooperation schematic diagram of the two magnetic field generating devices and the water cooling system.

[0019] Figure 4 It is a force schematic diagram of the welding arc under the action of the combination magnetic field at 0-T / 2 in embodiment 1, wherein the black solid arrow indicates the magnetic field magnetic line distribution direction, and the white hollow arrow indicates the electromagnetic force direction.

[0020] Figure 5is a schematic diagram of the force of the welding arc in T / 2-T under the combined magnetic field in Example 1, wherein the black solid arrow indicates the direction of the magnetic field magnetic line distribution, and the white hollow arrow indicates the direction of the electromagnetic force;

[0021] In the figure, 1 is a conductive rod, 2 is a welding gun sleeve, 3 is an axial excitation coil, 4 is a conductive nozzle, 5 is an external iron core sleeve, 6 is a longitudinal excitation coil, 7 is a water cooling channel, 701 is a water cooling channel on the left side of the welding gun sleeve, 702 is a water cooling channel of the external iron core sleeve, 703 is a water cooling channel on the right side of the welding gun sleeve, 8 is an external iron core, 9 is a four-hole rectangular fixed plate, and 10 is a welding gun fixed threaded hole. DETAILED DESCRIPTION

[0022] In order to better express the embodiments and specific effects of the present application, the embodiments of the present application will be further described below in combination with the drawings and examples, but the embodiments of the present application are not limited thereto.

[0023] Example 1: The embodiment of the present application proposes a method for controlling the directional deviation of the front and rear ends of a welding arc under a combined magnetic field of double magnetic poles. A combined magnetic field generated by a single longitudinal magnetic field and an axial magnetic field is used to control the shape of the welding arc. Specifically, the combined magnetic field generated by the welding gun axial magnetic field generating device and the external longitudinal magnetic field generating device controls the local periodic directional deviation of the welding arc. As shown in Figure 2 The welding gun axial magnetic field generating device is composed of a welding gun sleeve (2), an axial excitation coil (3), and an internal water cooling channel (7). The welding gun sleeve (2) is fixed on the conductive rod (1) and can completely accommodate the arc welding gun including the protective gas nozzle. The axial excitation coil (3) is wound on the sleeve in a dense manner using a common layer winding method. The two ends of the axial excitation coil are connected to the excitation power source to generate an axial magnetic field that acts on the welding arc. This axial magnetic field can significantly compress the arc, increase the arc energy density, and improve the heat input. The external longitudinal magnetic field generating device is composed of an external iron core (8), an external iron core sleeve (5), a longitudinal excitation coil (6), and a water cooling channel (7). The external iron core (8) is directly made of a material with good magnetic conductivity to reduce the loss in the magnetic conduction process and can directly affect the arc shape. The external iron core sleeve (5) is relatively small in size compared to the welding gun sleeve (2) and has a central through hole that can completely accommodate the external iron core (8). The external iron core (8) and the external iron core sleeve (5) can be fixed by adhesive bonding or other bonding methods. The longitudinal excitation coil (6) is also layer-wound on the external iron core sleeve (5) to generate a longitudinal magnetic field that acts on the welding arc. The longitudinal magnetic field and the local transverse magnetic field generated by the interaction of the above-mentioned axial magnetic field have a major deflection effect on the welding arc.

[0024] As Figure 3As shown, the two magnetic field generating devices are connected by a four-hole rectangular fixed plate (9), which ensures that the axes of the generating devices are parallel and the device main bodies are at the same height. In order to save space, the water cooling channels (7) of the two magnetic field generating devices are connected to each other, presenting a double U-shaped design with two layers. The upper layer water cooling pipeline enters from the left side water cooling channel (701) of the welding gun sleeve, passes through the external iron core sleeve water cooling channel (702), and then extends out from the right side water cooling channel (703) of the welding gun sleeve. Similarly, the lower layer water cooling pipeline also achieves such a U-shaped cooling effect, fully cooling the coil and sleeve to avoid coil loss and failure. The water inlet and outlet of the water cooling channel (7) are connected to the external water cooling system to ensure stable operation.

[0025] For the side of the welding gun sleeve (2) connected to the external iron core sleeve (5), a countersunk screw is used to fix the welding gun. For the other side, a common bolt is used to fasten the welding gun.

[0026] The external longitudinal magnetic field generating device of the embodiment is fixed to the rear end of the welding gun axial magnetic field generating device, and direct current positive connection is adopted. The specific method steps for regulating and controlling the welding arc are as follows: Figure 1 As shown: After determining the fixed position of the external longitudinal magnetic field generating device, the excitation power parameters need to be set in advance, mainly including excitation current and excitation frequency, so that the magnetic fields generated by the longitudinal excitation coil and the axial excitation coil interact to form a suitable combined magnetic field. Subsequently, according to the welding material and scene, the size of the additional electromagnetic force perpendicular to the welding direction is calculated through testing. The main purpose is to obtain the magnetic field and electromagnetic force distribution inside the arc space, so as to optimize the application position and application method of the external magnetic field and related welding conditions, and then adjust the excitation parameters to control the degree and range of directional deflection of the arc tail.

[0027] Specifically, the size of the additional electromagnetic force perpendicular to the welding direction is represented as: F = B x j, where B is the magnetic field distribution at a certain point in the welding area, and j is the current density at a certain point in the welding area. Here, the influence of the temperature field needs to be considered, so the electromagnetic field and current density distribution at a certain point can be calculated through a thermal-magnetic coupling model and a thermal-electric coupling model, respectively, and then the final electromagnetic force distribution can be calculated from the two parameters. For the magnetic field distribution B at a certain point, the general idea is to solve it using Maxwell's equations. According to the relationship between the magnetic potential space component and the magnetic induction intensity, the three components of the magnetic induction intensity at a certain point can be obtained: Where A is the magnetic potential. The overall trend of the magnetic field distribution during the welding process obtained in this way is still from the center of the weld to both sides, gradually decreasing from large to small, but the maximum magnetic induction intensity region shifts. Here, the degree of shift can be used to preliminarily judge whether the excitation parameters are appropriate. For the current density j at a certain point, the current density on any height section in the arc presents a Gaussian distribution, which can be represented as: Where I is the welding current, d is the arc distribution coefficient, and σ is the arc cross section.c is the current density distribution coefficient, r is the radius of the point.

[0028] The additional electromagnetic force perpendicular to the welding direction in the welding test is obtained by the above calculation process, and it is judged whether the electromagnetic force size value is within a reasonable range. If it exceeds the maximum additional electromagnetic force or the value is too small, the welding parameters and welding conditions, including welding current, welding voltage, sample surface cleanliness, etc. need to be adjusted first, and then the excitation parameters are reset and tested again. If the electromagnetic force size is within a reasonable range, the welding is formally started.

[0029] After the welding gun is successfully ignited during the formal welding, the welding is started along the welding direction. At this time, the two excitation coils start to work through alternating current. The longitudinal excitation coil (6) and the axial excitation coil (3) are distributed with magnetic pole polarity N-S and S-N, and alternately change within a period T. The water cooling system simultaneously cools the coils. At 0-T / 2, the longitudinal excitation coil (6) and the axial excitation coil (3) are respectively connected with I1 and -I2 excitation current, so as to generate a combined magnetic field with N-S magnetic pole polarity distribution in the welding arc space and make the rear end of the arc directional offset to the left. The force on the arc at this time is as shown in Figure 4 At T / 2-T, the longitudinal excitation coil (6) and the axial excitation coil (3) are respectively connected with -I1 and I2 excitation current, so as to generate a combined magnetic field with S-N magnetic pole polarity distribution in the welding arc space and make the rear end of the arc directional offset to the right. The force on the arc at this time is as shown in Figure 5 Through the magnetic pole polarity transformation and the amperes force direction transformation with a period T, the rear end of the welding arc is periodically directional offset. The specific effect is that the liquid metal at the tail of the molten pool is uniformly spread, and at the same time, the momentum of the backward liquid flow in the molten pool is reduced, avoiding the accumulation of liquid metal to produce hump defects, so as to make the weld smooth and beautiful.

[0030] After welding, the weld forming effect is observed. If there are obvious defects, it is necessary to judge whether the defects affect the quality of the workpiece. If the load or other standards of the related welding structure do not meet the requirements, the welding parameters still need to be adjusted, and the subsequent test is carried out again. If there is no defect after welding or the defect does not affect the welding quality, the welding is ended, and the weld that meets the requirements is obtained.

[0031] In this embodiment, the external longitudinal magnetic field generating device is fixed to the front end of the welding gun axial magnetic field generating device, and direct current is connected in positive, so this embodiment mainly controls the deviation of the arc front end, the longitudinal exciting coil (6) and the axial exciting coil (3) still change in magnetic pole polarity N-S and S-N distribution alternately in a period T, but the specific performance is: at 0-T / 2, the longitudinal exciting coil (6) and the axial exciting coil (3) are respectively connected with I1, -I2 exciting current, so that the N-S magnetic pole polarity distribution in the welding arc space and the combined magnetic field that makes the arc front end deviate to the right are generated; at T / 2-T, the longitudinal exciting coil (6) and the axial exciting coil (3) are respectively connected with -I1, I2 exciting current, so that the S-N magnetic pole polarity distribution in the welding arc space and the combined magnetic field that makes the arc front end deviate to the left are generated, through the magnetic pole polarity transformation and the ampere force direction transformation in a period T, the welding arc front end is periodically deviated.

[0032] The beneficial effect of the periodic directional deviation of the welding arc front end is to expand the influence range of the arc, and then change the heat affected zone range of the weld, that is, the weld forming parameters including the penetration and the width change, the specific performance is that the penetration is reduced and the width is increased, which can be applied to special welding scenes.

[0033] The present application is not limited to the above preferred embodiments, various modifications and changes can be made on the basis of the experimental device and method described in the present application, any change, modification, substitution, combination, simplification and the like made according to the spirit and principle of the technical scheme of the present application are equivalent replacement methods, all these modifications and changes are within the protection scope of the present application.

Claims

1. A method for controlling the directional offset of the front and rear ends of a welding arc using a dual-pole combined magnetic field, wherein the method employs a welding system consisting of an arc welding torch, an axial magnetic field generator for the welding torch, and an external longitudinal magnetic field generator to control the directional offset of the front or rear ends of the welding arc, further controlling the local stirring effect of the arc, characterized in that... The welding system described above controls the arc shape through the interaction of the welding torch axial magnetic field generator and the external longitudinal magnetic field generator. The welding torch axial magnetic field generator consists of a welding torch sleeve (2), an axial excitation coil (3), and a water-cooling channel (7). The welding torch sleeve (2) is coaxially mounted on the welding torch, and the axial excitation coil (3) wound around the welding torch sleeve (2) generates an axial magnetic field. The external longitudinal magnetic field generator consists of an external iron core (8), an external iron core sleeve (5), a longitudinal excitation coil (6), and a water-cooling channel (7). It is individually installed at the front or rear end of the welding torch axial magnetic field generator. The external iron core (8) is fixed in the central through hole of the external iron core sleeve (5), and the longitudinal excitation coil (6) wound around the external iron core sleeve (5) generates a longitudinal magnetic field. This longitudinal magnetic field and the axial magnetic field generated by the axial excitation coil (3) work together to form a local transverse magnetic field, which is a dual-pole combined magnetic field. The above welding torch axial magnetic field generator The external longitudinal magnetic field generator is connected to the external longitudinal magnetic field generator by a four-hole rectangular fixing plate (9), and the water cooling channels (7) of the two magnetic field generators are interconnected, presenting a double U-shaped design with upper and lower layers. The upper water cooling pipe enters from the water cooling channel (701) on the left side of the welding gun sleeve, passes through the water cooling channel (702) of the external iron core sleeve, and then extends from the water cooling channel (703) on the right side of the welding gun sleeve. Similarly, the lower water cooling pipe also achieves such a U-shaped cooling effect, fully cooling the coil and sleeve, avoiding coil loss and failure. The inlet and outlet of the water cooling channel (7) are connected to the external water cooling system to ensure working stability. The magnetic field lines of the dual magnetic pole combination magnetic field are perpendicular to both the arc axis and the welding direction, so that the combination magnetic field compresses the arc while causing a directional shift at the front or rear end of the welding arc. That is, one end is fully stirred, while the other end basically remains unchanged, and the center of the arc remains basically unchanged. The specific process of the control method of the dual magnetic pole combination magnetic field controlling the directional shift of the front and rear ends of the welding arc is as follows: The longitudinal excitation coil (6) and the axial excitation coil (3) alternately change their magnetic pole polarities of NS and SN within a period of T. The longitudinal excitation coil (6) is placed at the rear end of the welding torch axial magnetic field generator and is DC positively connected. During the period 0-T / 2, the longitudinal excitation coil (6) and the axial excitation coil (3) are respectively supplied with excitation currents of I1 and -I2, which generate a magnetic pole polarity distribution of NS and a combined magnetic field that causes the rear end of the arc to deflect to the left. During the period T / 2-T, the longitudinal excitation coil (6) and the axial excitation coil (3) are respectively supplied with excitation currents of -I1 and I2, which generate a magnetic pole polarity distribution of SN and a combined magnetic field that causes the rear end of the arc to deflect to the right. Through the change of magnetic pole polarity and the change of Ampere force direction with a period of T, the rear end of the welding arc is periodically deflected, the molten pool is fully stirred and uniform, and the weld is smooth and beautiful.

2. The method for controlling the directional offset of the welding arc's front and rear ends using a dual-pole combined magnetic field according to claim 1, characterized in that, The method for controlling the directional offset of the welding arc front and rear ends by the dual-pole combined magnetic field is applicable to tungsten inert gas welding and gas metal arc welding.

3. The method for controlling the directional offset of the welding arc's front and rear ends using a dual-pole combined magnetic field according to claim 1, characterized in that, The water-cooled channel (7) is arranged in either series or parallel. In series, the upper water-cooled pipe is connected to the lower water-cooled pipe; in parallel, the upper water-cooled pipe and the lower water-cooled pipe are each supplied with water.

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