Weld seam tracking device based on longitudinal magnetic field to control TIG welding arc shape

Abstract

The present invention relates to the field of welding automation, and specifically designs a weld tracking device for controlling the arc shape of TIG welding based on a longitudinal magnetic field. The purpose of the present invention is to control the rotation of charged particles by controlling the longitudinal magnetic field, and then obtain the deviation between the welding gun and the weld by comparing the voltage value. The invention is simple to operate and has accurate weld tracking. The system includes a tungsten electrode welding gun, a bracket, a gear, an excitation coil, an outer sleeve, an inner sleeve, a bearing, a Hall sensor, a computer, a common emitter amplifier circuit device, etc. The structure is simple, and it has real-time performance, high efficiency, and high weld tracking accuracy.

Description

Technical Field

[0001] The invention relates to the field of welding automation, and specifically designs a weld tracking device for controlling the TIG welding arc shape based on a longitudinal magnetic field. Background Art

[0002] Tungsten inert gas shielded arc welding (TIG welding for short) is an arc welding method that uses pure tungsten or activated tungsten (such as thoriated tungsten, cerium tungsten, etc.) as a non-melting electrode and an inert gas (such as argon, helium, etc.) as a shielding gas. It is widely used in modern industry. Its advantages are high quality of welded joints and can be used for almost all metal connections. It is particularly suitable for welding thin plates or thin-walled pipes. However, TIG welding has a small penetration depth and low efficiency. In order to improve the efficiency of TIG welding, people have adopted many effective methods, such as active agent TIG welding (A-TIG), ultrasonic TIG composite technology (U-TIG), hot wire TIG welding and high-speed TIG welding. Medium-speed TIG welding uses the method of increasing the welding speed to improve the welding efficiency. The welding speed is generally above 1m / min. However, the increase in welding speed will cause the TIG arc anode spot to lag behind, the arc to drag, and then produce welding defects such as undercut and hump. The higher the welding speed, the more serious the arc drag, and the undercut and poor forming will be aggravated. How to solve these existing problems has become a key technology for achieving high-speed TIG welding.

[0003] Magnetic field welding technology is a new type of welding technology developed in recent years. During the welding process, an external magnetic field is applied to the arc, which will affect the movement form of charged particles in the arc and the arc shape, thereby affecting the molten droplet transfer process. It has a significant effect on the flow of metal in the molten pool, the formation and growth of grains, and can refine the primary structure of the weld, reduce the unevenness of chemical composition, reduce the formation of weld pores and cracks, and effectively improve the quality of the welded joint and welding production efficiency.

[0004] Since the magnetic field has the characteristics of simple auxiliary devices, low investment cost, high efficiency, low energy consumption, and can significantly improve the welding quality, the use of external magnetic field to control the welding process has broad application prospects and important research value. Summary of the invention

[0005] The purpose of the present invention is to control the rotation of charged particles by controlling the longitudinal magnetic field, and then obtain the deviation between the welding gun and the weld by comparing the voltage value. The invention is simple to operate and has accurate weld tracking. The system includes a tungsten electrode welding gun, a bracket, a gear, an excitation coil, an outer sleeve, an inner sleeve, a bearing, a Hall sensor, a computer, a common emitter amplifier circuit device, etc. The structure is simple and the weld tracking accuracy is high.

[0006] The weld tracking device based on longitudinal magnetic field to control the arc shape of TIG welding is characterized in that: the system generates the required magnetic field by a longitudinal magnetic field generating device, and the magnetic field generating device provides a stable excitation current for the excitation coil by a DC power supply. The voltage signal is amplified by a common emitter amplifier circuit. One end of the Hall sensor is connected to the welding gun, and the other end is connected to the workpiece. The amplified arc voltage signal is extracted by the Hall sensor, and after computer analysis and processing, the welding gun position is continuously adjusted to align the welding gun with the center position of the weld.

[0007] The specific method is as follows:

[0008] The device is fixed with a welding gun and an excitation coil by a bracket. In order to avoid damage to the detection device caused by sparks and spatters during welding, an external sleeve is added to the entire device. A DC power supply provides a stable excitation current for the excitation coil, and the excitation coil wound on the inner sleeve is energized, and a longitudinal magnetic field is generated at this time. When the tungsten electrode welding gun starts working, the 1-motor is energized, and the 2-gear is driven to rotate. Since the 7-iron core and the inner sleeve are connected together by the 8-connecting bearing, the 7-iron core starts to rotate around the excitation coil from the left side, thereby generating a longitudinal magnetic field passing through the left half of the arc. The voltage signal is amplified by the common emitter amplifier circuit, and the arc voltage value U1 is obtained according to the Hall sensor. Similarly, when the 7-iron core rotates to the right side of the excitation coil, a longitudinal magnetic field passing through the right half of the arc is generated. The voltage signal is amplified by the common emitter amplifier circuit, and the arc voltage value U2 is obtained according to the Hall sensor. Therefore, this device can destroy the balance between the longitudinal magnetic fields that originally existed during the welding process by rotating the iron core, thereby changing the size of the voltage value. Therefore, according to the weld groove morphology, the U1 and U2 values ​​are input into the computer, and the left and right deviations of the weld are obtained according to the comparison of U1 and U2, and the welding gun position is adjusted to achieve real-time weld tracking.

[0009] The advantages of the present invention are:

[0010] The entire weld tracking device of the present invention has a simple structure and strong operability. Since ceramics have good high temperature resistance, corrosion resistance, excellent insulation performance, high hardness and other characteristics, the 4-inner sleeve is made of ceramic material. And in order to avoid the damage of the external sensor device caused by sparks and splashes generated during welding, a 3-outer sleeve is added to the device. Compared with the traditional weld tracking system, it is simpler and the system data processing is relatively simpler. On the basis of the longitudinal magnetic field, the longitudinal magnetic fields on the left and right sides of the arc can be independently controlled by the rotating 7-iron core. Based on the signal amplification of the common emitter circuit, the signal extraction of the Hall sensor and the computer signal processing, the accurate tracking of the weld can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1It is a flow chart of the present invention.

[0012] Figure 2 It is the overall architecture diagram of the present invention.

[0013] Figure 3 This is an internal diagram of the present invention.

[0014] Figure 4 It is a cross-sectional view of the present invention.

[0015] Among them: 1-motor, 2-gear, 3-external sleeve, 4-inner sleeve, 5-tungsten electrode welding gun, 6-keyway, 7-iron core, 8-connecting bearing, 9-excitation coil, 10-rolling bearing. DETAILED DESCRIPTION

[0016] In order to better express the technical solutions and beneficial results of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0017] The system structure diagram of the weld tracking device based on longitudinal magnetic field control of TIG welding arc morphology of the present invention is as follows Figure 2 As shown, it mainly solves the problems of complex structure and inaccurate positioning of the weld tracking system. It is characterized in that: the system includes a bracket, a welding gun, an excitation coil, a sensor protection device, a voltage sensor, a common emitter circuit device, and a computer. Among them, the welding gun and the excitation coil are fixed together by the bracket, which is convenient for moving with the weld position to realize scanning of the workpiece surface. One end of the Hall sensor is connected to the welding gun and the other end is connected to the workpiece, which is convenient for extracting the weld voltage signal. The Hall sensor is connected to the computer to facilitate processing the voltage signal and extracting the weld deviation. During the welding process, the present invention can control the longitudinal magnetic field on the left and right sides of the arc in real time through a rotating iron core, so that the weld tracking effect is more accurate and the system structure is simpler and more efficient.

[0018] The charged particles in the welding arc include electrons, positive ions and negative ions, and the key role is played by electrons and positive ions. When no magnetic field is applied, during the welding process, the charged particles will produce directional motion due to the longitudinal electric field, transverse (radial) electric field and concentration difference generated by themselves. When the longitudinal magnetic field is applied, the directional motion component of the charged particles in the arc (taking electrons as an example, the motion form of positive ions is just opposite to that of electrons) is affected by the magnetic field and generates Lorentz force. The Lorentz force provides centripetal force, so the charged particles begin to move in a circle with a radius of r around the arc axis.

[0019] Assume that a uniform longitudinal magnetic field is applied, and the centripetal acceleration formula, Newton's second law formula and Lorentz force formula are shown in equations (1) to (3) respectively. Since the centripetal force of the electron in the magnetic field is provided by the Lorentz force on the electron, the calculation formula for the rotation radius of the electron in the magnetic field can be derived based on equations (2) and (3), as shown in equation (4).

[0020] a=v 2 / r (1)

[0021] F=ma=mv 2 / r (2)

[0022] F=qvB (3)

[0023] r=mv / qB (4)

[0024] In the formula: a is acceleration; r is the rotation radius; F is the Lorentz force; m is the mass of the electron; v is the velocity component of the electron's directional motion; q is the electron's charge; and B is the magnetic induction intensity.

[0025] It can be seen from equation (4) that because the Lorentz force does not do work, the speed of the electron remains unchanged, and thus the electron rotation radius r is inversely proportional to the magnetic induction intensity B. Therefore, when the magnetic induction intensity increases, the rotation radius decreases and the arc column shrinkage increases.

[0026] 1) When there is no magnetic field, the arc column is conical and has no rotational motion.

[0027] 2) Under the action of an external magnetic field, the arc column is in a contracted state and rotates clockwise; as the magnetic field intensity increases, the degree of contraction of the arc column increases accordingly.

[0028] 3) Under the action of an external longitudinal magnetic field, the rotation radius of the arc is inversely proportional to the magnetic induction intensity.

[0029] When an external constant longitudinal magnetic field is applied, the charged particles in the welding arc rotate at high speed. This high-speed drift rotation motion increases the distance that the arc conducts the current, which is actually equivalent to increasing the arc length. Therefore, as the magnetic induction intensity of the external longitudinal magnetic field increases, the arc voltage will increase. Under the action of the external constant longitudinal magnetic field, the welding arc rotates at high speed, which strengthens the cooling effect of the surrounding gas medium on the arc, increases the electric field intensity of the arc column, and also causes the arc voltage to increase.

[0030] Embodiment: Specifically illustrate the welding gun posture adjustment process.

[0031] A DC power supply provides a stable excitation current for the excitation coil. The excitation coil wound around the inner sleeve is energized, and a longitudinal magnetic field will be generated at this time. When the tungsten electrode torch starts to work, the 1-motor is energized. At this time, by driving the 2-gear to rotate, since the 7-iron core and the inner sleeve are connected together by the 8-connecting bearing, the 7-iron core starts to rotate around the excitation coil from the left side at this time, thus generating a longitudinal magnetic field passing through the left half of the arc. The voltage signal is amplified by the common emitter amplifier circuit, and then the arc voltage value U1 is obtained according to the voltage sensor. Similarly, when the 7-iron core rotates to the right side of the excitation coil, a longitudinal magnetic field passing through the right half of the arc is generated. The voltage signal is amplified by the common emitter amplifier circuit, and then the arc voltage value U2 is obtained according to the voltage sensor.

[0032] The iron core starts to perform a circular motion of rotating around the excitation coil from the left side to the right side. At this time, the longitudinal magnetic field on the side where the iron core is located will be affected, so the magnetic field strength will increase. The voltage signal is amplified by the common emitter amplifier circuit, and the amplified arc voltage value U1 is obtained according to the Hall sensor. When the iron core moves to the right side driven by the motor, the voltage signal is amplified by the common emitter amplifier circuit, and the arc voltage U2 is obtained according to the voltage sensor. Compare U1 with U2. If U1 < U2, the torch is on the left side of the weld. The movement trajectory of the arc particles on the right side is longer, so the voltage on the right side of the arc is greater. If U1 > U2, the torch is on the right side of the weld.

[0033] When U1 < U2, the torch is on the left side of the weld, and at this time, the torch needs to be moved to the right. When U1 > U2, the torch is on the right side of the weld, and at this time, the torch needs to be moved to the left. The measured U1 and U2 after each movement are input into the computer for data analysis and processing. After continuous adjustment, the voltages on both sides of the arc gradually approach equality. When U1 = U2, at this time, the working point of the torch is the best, and the weld forming effect is the best.

Claims

1. The weld tracking device based on the longitudinal magnetic field to control the arc shape of TIG welding is mainly used to solve the problems of complex system structure and inaccurate positioning in weld tracking. It is characterized by: The device includes a tungsten electrode welding gun, a bracket, a gear, an excitation coil, an outer sleeve, an inner sleeve, a bearing, a connecting sleeve, a Hall sensor, a computer, a sensor protection device, and a common emitter amplifier circuit device; wherein the tungsten electrode welding gun passes through the inner sleeve, the excitation coil is wound on the inner sleeve, and is fixed together by a bearing, so as to be easy to move along with the position of the weld to realize scanning of the workpiece surface, and the excitation coil power supply adopts a DC power supply; the iron core is connected to the inner sleeve through the connecting bearing, and when the workpiece is welded, the iron core is driven by a motor to rotate around the excitation coil, thereby breaking the balance of the longitudinal magnetic field generated by the excitation coil, so as to extract the voltage signal around the weld.

2. According to the weld tracking device based on longitudinal magnetic field control of TIG welding arc shape described in claim 1, a DC power supply provides a stable excitation current for the excitation coil, and the excitation coil wound on the inner sleeve is energized, and a longitudinal magnetic field is generated at this time; when the tungsten electrode welding gun starts to work, the motor is energized, and the gear is driven to rotate. Since the iron core and the inner sleeve are connected together by a connecting bearing, the iron core starts to rotate around the excitation coil from the left side, thereby generating a longitudinal magnetic field passing through the left half of the arc; the voltage signal is amplified by a common emitter amplifier circuit, and then based on the The arc voltage value U1 is obtained according to the Hall sensor. When the iron core rotates to the right side of the excitation coil, a longitudinal magnetic field passing through the right half of the arc is generated. The voltage signal is amplified by the common emitter amplifier circuit, and then the arc voltage value U2 is obtained according to the Hall sensor. The device can destroy the balance between the longitudinal magnetic fields that originally existed during the welding process by rotating the iron core, thereby changing the voltage value. Then, according to the weld groove morphology, the U1 and U2 values ​​are input into the computer, and the left and right deviations of the weld are obtained based on the comparison of U1 and U2, and the welding gun position is adjusted to achieve real-time weld tracking.

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