A device and method for regulating the thermal distribution of an electric arc to fill a keyhole formed by a keyhole plasma arc welding

Abstract

The application discloses a device and method for adjusting arc thermal power distribution to fill in a small hole after a piercing type plasma arc welding, which is characterized by the following: under the condition of plasma arc welding, a dynamic push-pull device is used to reduce the tungsten electrode shrinkage, change the arc restraint degree, change the arc force and heat input size and the arc action range size, reduce the plasma arc penetration capacity, and meanwhile, a computer is used to control the welding current and wire feeding speed, so that the molten drop can stably and safely flow into the generated welding small hole, and the purpose of filling in the small hole is achieved. The application changes the arc thermal power distribution, uses the computer to control the welding current and wire feeding speed, and achieves the purpose of filling in the small hole after the welding. The device does not need manual TIG hole repairing after the welding, reduces the processing procedure, and improves the automatic and intelligent levels of the plasma welding.

Description

TECHNICAL FIELD

[0001] The present application relates to a device and method for adjusting arc heat power distribution to fill the small hole after the piercing type plasma arc welding, and belongs to the technical field of high-efficiency plasma arc welding process. BACKGROUND

[0002] Plasma arc welding is a high-energy density welding process method, compared with laser welding and electron beam welding, plasma arc welding has low equipment cost, simple operation, and strong adaptability to joint assembly gap, so it has broad application prospects in the processing and manufacturing of various alloy material structures. The piercing type plasma arc welding is suitable for welding 3-8mm thick stainless steel, 12mm or less thick titanium alloy, medium-thickness low-carbon steel and low-alloy structural steel. Using variable polarity plasma arc welding power supply, single-sided welding can weld 15mm thick aluminum and aluminum alloy. And the above-mentioned materials in the thickness range can be welded without opening the groove once, and single-sided welding double-sided forming can be realized. However, due to the unique physical characteristics of plasma arc, the plasma arc has high restraint degree, large current density, and concentrated energy, and a small hole is generated at the arc collection place after welding, which needs manual TIG hole repair after welding.

[0003] In order to solve the above problems, the present application discloses a device and method for adjusting arc heat power distribution to fill the small hole after the piercing type plasma arc welding. The device is used to reduce the tungsten electrode shrinkage under the condition of plasma arc welding, change the arc restraint degree, change the arc force and heat input size and the arc action range size, reduce the penetration ability of plasma arc, and use the computer to control the welding current and wire feeding speed, so that the molten droplet can flow into the generated welding small hole stably and safely, so as to achieve the purpose of filling the small hole. The present application changes the arc heat power distribution, uses the computer to control the change of welding current and wire feeding speed, and achieves the purpose of filling the small hole after welding. The device does not need manual TIG hole repair after welding, reduces the processing procedure, and improves the automation and intelligent level of plasma welding. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art, and provides a device and method for adjusting arc heat power distribution to fill the small hole after the piercing type plasma arc welding. The device is used to reduce the tungsten electrode shrinkage under the condition of plasma arc welding, change the arc restraint degree, change the arc force and heat input size and the arc action range size, reduce the penetration ability of plasma arc, and use the computer to control the welding current and wire feeding speed, so that the molten droplet can flow into the generated welding small hole stably and safely, so as to achieve the purpose of filling the small hole. The present application changes the arc heat power distribution, uses the computer to control the change of welding current and wire feeding speed, and achieves the purpose of filling the small hole after welding. The device does not need manual TIG hole repair after welding, reduces the processing procedure, and improves the automation and intelligent level of plasma welding.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0006] The device and method for adjusting the distribution of arc heat to fill the small hole after the piercing type plasma arc welding, characterized in that: it comprises a dynamic push-pull device (1), a device fixed shell (2), a tungsten electrode connecting rod (3), a tungsten electrode (4), and a plasma arc welding torch (5). The dynamic push-pull device is connected with the device fixed shell by means of bolt connection; one end of the tungsten electrode connecting rod is fixedly connected with the dynamic push-pull device, and the other end is detachably connected with the tungsten electrode, wherein the end connected with the tungsten electrode is made of high-temperature-resistant insulating material; the tungsten electrode is connected with a plasma arc welding power source, and the outside of the tungsten electrode is the plasma arc welding torch body.

[0007] The dynamic push-pull device comprises a gear transmission device (1-1), an eccentric connecting rod (1-2), a sliding rail (1-3), a sliding block (1-4), and the tungsten electrode connecting rod (3). The gear transmission device is provided with a driving motor, and the control gear rotates at different speeds. The gear transmission device (1-1) is connected with the eccentric connecting rod (1-2), and the eccentric connecting rod (1-2) is connected with the sliding block (1-4); the sliding block (1-4) is connected with the sliding rail (1-3); the rotation of the gear drives the sliding block (1-4) to move, controls the movement of the tungsten electrode connecting rod, and achieves the purpose of controlling the retraction amount of the tungsten electrode; the tungsten electrode connecting rod (3) is a specially-made high-temperature-resistant insulating device.

[0008] The dynamic push-pull device is controlled by a computer control end, and the device is connected with a plasma arc welding torch movement system and moves together with the welding torch. When the welding is about to end and the arc is extinguished, a signal is triggered by the computer control end to control the dynamic push-pull device, so that the retraction amount of the tungsten electrode changes from large to small, the arc diverges, the arc force decreases at the arc extinguishing position, the heat input range increases, and the plasma arc piercing ability is reduced. At this time, the wire feeder still maintains the wire feeding state, cooperates with the plasma arc to melt the welding wire, and fills the small hole after the plasma arc welding.

[0009] The computer control end can manually control the signal trigger, and can also preset the trajectory to automatically control the signal trigger. When the welding is about to end and the arc is extinguished, the computer control end triggers a signal to control the tungsten electrode to move downward, and the signal is transmitted to the welding machine current control end and the wire feeding device end as a signal source, so as to control the welding current to decrease and the wire feeding speed to decrease, so as to achieve the purpose of smoothly and safely filling the small hole, and also prevent the problem of nozzle burning and damage to the welding torch due to excessive current caused by the downward movement of the tungsten electrode.

[0010] The retraction amount of the tungsten electrode controlled by the dynamic push-pull device is -4mm~+4mm, and the retraction amount adjustment accuracy is 0.1mm. (with the plasma arc welding torch nozzle as the reference surface). The dynamic push-pull device is connected with a computer control end, which can adjust the motor frequency according to the experimental requirements, control the rotation speed and range of the gear, and control the speed and size of the extension and retraction of the tungsten electrode.

[0011] The tungsten electrode is made of cerium-tungsten alloy or thorium-tungsten alloy.

[0012] A device and method for adjusting arc thermal distribution to fill in the small hole after piercing type plasma arc welding, comprising the following steps,

[0013] Step one: assemble the welding torch with the dynamic push-pull device, connect the plasma welding equipment, and preset the initial welding current, wire feeding speed, and other experimental conditions. Set the response frequency of the dynamic push-pull device according to the wire feeding speed, welding current, and other conditions.

[0014] Step two: adjust the tungsten electrode retraction amount, set the signal trigger after welding current and wire feeding speed change curve,

[0015] Step three: start the plasma welding power supply and perform welding according to the predetermined trajectory. When the welding is completed, the computer control end triggers the control signal to control the dynamic push-pull device, so that the tungsten electrode retraction amount changes from large to small, and the welding current and wire feeding speed change accordingly. Keep for a certain period of time, then turn off the welding power supply and wire feeder.

[0016] The beneficial effects of the present application are:

[0017] (1) The present application designs a device that can adjust the arc thermal distribution. The dynamic push-pull device designed by the applicant is used to control the change of the tungsten electrode retraction amount, so that the arc force and the heat input range change, affecting the quality of the plasma welding seam.

[0018] (2) The tungsten electrode and the dynamic push-pull device are connected by a detachable connecting device, which can adjust the length of the tungsten electrode and replace different types of tungsten electrodes as needed, improving the adaptability to different types of welding torches and welding process parameters.

[0019] (3) The present application controls the arc thermal distribution, welding current, and wire feeding speed to achieve the purpose of automatically filling in the small hole at the end of welding, without the need for post-weld hole repair, reducing the processing procedures, and improving the automation and intelligent level. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of a device for adjusting arc thermal distribution to fill in the small hole after piercing type plasma arc welding.

[0021] Figure 2 is a dynamic push-pull device.

[0022] In the figure, 1 is a dynamic push-pull device: gear transmission device (1-1), eccentric connecting rod (1-2), slide rail (1-3), and sliding block (1-4); 2 is a device fixed shell; 3 is a tungsten electrode connecting rod; 4 is a tungsten electrode; and 5 is a plasma welding torch.

[0023] Figure 3 Dynamic push-pull device control plasma arc change during arc collection process schematic diagram.

[0024] Figure 4 Computer control end signal control flow chart. DETAILED DESCRIPTION

[0025] In order to further understand the content, features and effects of the present application, the following examples are listed and described in detail as follows in conjunction with the drawings:

[0026] The basic idea of the present application: the present application is under the condition of plasma arc welding, using dynamic push-pull device to reduce the tungsten electrode shrinkage, change the degree of arc restraint, change the arc force and heat input size and the size of the arc action range, reduce the penetration ability of plasma arc, at the same time, using computer control welding current and wire feeding speed, make the molten drop stable and safe into the generated welding hole, to achieve the purpose of filling the hole.

[0027] As shown in Figure 1 It is a kind of adjusting arc heat force distribution filling hole type plasma arc welding after the device schematic diagram, it includes dynamic push-pull device (1), device fixed shell (2), tungsten electrode connecting rod (3), tungsten electrode (4), plasma arc welding gun (5). The dynamic push-pull device is connected with the device fixed shell by bolt connection; the tungsten electrode connecting rod is fixedly connected with the dynamic push-pull device at one end, and is detachably connected with the tungsten electrode at the other end, wherein the end connected with the tungsten electrode is made of high temperature resistant insulating material; the tungsten electrode is connected with the plasma arc welding power supply, and the outside of the tungsten electrode is the plasma arc welding gun body.

[0028] As shown in Figure 2 The dynamic push-pull device includes gear transmission device (1-1), eccentric connecting rod (1-2), slide rail (1-3), slide block (1-4) and tungsten electrode connecting rod (3). The gear transmission device is provided with a driving motor, and the control gear rotates at different speeds. The gear transmission device is connected with the eccentric connecting rod, and the eccentric connecting rod is connected with the slide block. The gear rotates to drive the slide block to move, control the tungsten electrode connecting rod to move, and achieve the purpose of controlling the tungsten electrode shrinkage. The tungsten electrode connecting rod is a special high temperature resistant insulating device.

[0029] The dynamic push-pull device is controlled by the computer control end, the device is connected with the plasma arc welding gun movement system and moves with the welding gun. When the welding is about to end, the computer control end triggers a signal to control the dynamic push-pull device, so that the tungsten electrode shrinkage changes from large to small, the arc diverges, the arc force at the arc extinguishing position decreases and the heat input action range increases, and the plasma arc penetration ability decreases (as Figure 3The wire feeder is still in the wire feeding state at this time, and matches the plasma arc to melt the welding wire and fill the small hole after plasma welding. The tungsten electrode retraction amount controlled by the dynamic push-pull device is -4 mm to +4 mm, and the retraction amount adjustment accuracy is 0.1 mm (based on the plasma welding gun nozzle reference surface). The dynamic push-pull device is connected to a computer control end, which can adjust the motor frequency, control the gear rotation speed and rotation range, and control the speed and size of the tungsten electrode extension and retraction according to the experimental requirements.

[0030] The computer control end signal controls as shown in Figure 4 , wherein the computer control end can manually control the signal trigger, and can also preset the trajectory automatic control signal trigger. When welding to the arc, after the computer control end triggers the signal to control the downward movement of the tungsten electrode, the signal is transmitted to the welding machine current control end and the wire feeder end as a signal source, to control the welding current to decrease and the wire feeding speed to decrease, so as to achieve the purpose of smoothly and safely filling the small hole, and also to prevent the problem of nozzle burning and welding gun damage caused by excessive current due to the downward movement of the tungsten electrode.

[0031] Example 1:

[0032] Take the VPPA plasma welding method to weld a 10 mm thick and 10 cm long butt weld without beveling as an example, as shown in Figure 1 , connect the required equipment according to the figure. The power source used during welding is a variable polarity plasma arc welding power source, and a three-dimensional motion mechanism is used to drive the plasma welding gun and other devices to move. The specific steps include the following:

[0033] Step 1: Sand the surface of the two aluminum plates to be welded to remove surface oil and oxide film, and fix the two aluminum plates on the workbench. Set the ion gas flow to 2.8 L / min and the shielding gas flow to 15 L / min. Turn on the variable polarity plasma arc power source, set the plasma arc EN stage current to 290 A and the EP stage current to 270 A. Adjust the relative position of the plasma welding gun and the aluminum plate to be welded to 4 mm above the aluminum plate through the three-dimensional motion mechanism controller;

[0034] Step 2: Assemble the welding gun with the dynamic push-pull device, connect the plasma welding equipment, set the dynamic push-pull device response frequency to 1000 Hz according to the welding speed, welding current and other conditions, and use the dynamic push-pull device to make the tungsten electrode retraction amount -4 mm. Set the signal trigger on the computer control end to change the welding current and wire feeding speed curve.

[0035] Step 3: Start the plasma welding power source and the dynamic push-pull device, and weld according to the predetermined trajectory.

[0036] Step four: when the welding torch moves to the predetermined 10 cm track, the computer control end triggers the control signal to control the dynamic push-pull device, changes the tungsten electrode retraction amount from -4 mm to +4 mm, and the welding current and wire feeding speed change accordingly. Keep for 1 s, then turn off the welding power supply and wire feeder, complete the required weld.

Claims

1. A device for adjusting the thermal distribution of the electric arc to fill the small holes after perforation plasma arc welding, characterized in that: The device includes a dynamic push-pull device (1), a device fixing shell (2), a tungsten electrode connecting rod (3), a tungsten electrode (4), and a plasma welding torch (5). The dynamic push-pull device (1) is connected to the device fixing shell (2) by bolts. One end of the tungsten electrode connecting rod (3) is fixedly connected to the dynamic push-pull device (1), and the other end is detachably connected to the tungsten electrode (4). The end connected to the tungsten electrode (4) is made of high-temperature resistant insulating material. The tungsten electrode (4) is connected to a plasma arc welding power source, and its exterior is the body of the plasma welding torch (5). The dynamic push-pull device (1) includes a gear transmission device (1-1), an eccentric connecting rod (1-2), a slide rail (1-3), and a slider (1-4); the gear transmission device (1-1) is equipped with a drive motor to control the gear to rotate at different speeds; the gear transmission device (1-1) is connected to the eccentric connecting rod (1-2), and the eccentric connecting rod (1-2) is connected to the slider (1-4); the slider (1-4) is connected to the slide rail (1-3); the rotation of the gear drives the slider (1-4) to move, controlling the movement of the tungsten electrode (4) connecting rod, thereby controlling the amount of tungsten electrode shrinkage; the tungsten electrode connecting rod (3) is a specially made high-temperature resistant insulating device; The dynamic push-pull device (1) is controlled by a computer control terminal. The dynamic push-pull device is connected to the motion system of the plasma welding torch and moves with the plasma welding torch. When the welding is about to end and the arc is about to be extinguished, the computer control terminal triggers a signal to control the dynamic push-pull device (1), so that the inward retraction of the tungsten electrode (4) changes from large to small to 1mm to 3mm, so that the arc diverges and becomes a TIG arc. The arc force at the arc termination point decreases and the heat input range increases, reducing the plasma arc piercing ability. At this time, the wire feeder still maintains the wire feeding state, and cooperates with the plasma arc to melt the welding wire and fill the small holes after plasma welding. The computer control terminal can be manually controlled by a signal trigger, or it can be automatically controlled by a preset trajectory. When welding reaches the arc termination point, the computer control terminal triggers a signal to control the downward movement of the tungsten electrode. This signal is transmitted simultaneously to the welding machine current control terminal and the wire feeding device terminal as a signal source, controlling the reduction of welding current and wire feeding speed to achieve the purpose of smoothly and safely filling the small hole. At the same time, it can also prevent the problem of excessive current burning the nozzle and damaging the welding gun due to the downward movement of the tungsten electrode. The dynamic push-pull device (1) can adjust the tungsten electrode retraction amount from -4mm to +4mm, and the retraction adjustment accuracy is 0.1mm. The dynamic push-pull device (1) is connected to an external computer control terminal, which can adjust the motor frequency, control the gear rotation speed and rotation range, and control the speed and size of the tungsten electrode extension and retraction according to the experimental requirements.

2. The device for adjusting the arc heat distribution and filling the small hole after perforation plasma arc welding according to claim 1, characterized in that: The tungsten electrode (4) is made of cerium-tungsten alloy or thorium-tungsten alloy.

3. A method for adjusting the arc heat distribution and filling the small hole after perforation plasma arc welding according to any one of claims 1 to 2, characterized in that: Includes the following steps, Step 1: Assemble the plasma welding torch with the dynamic push-pull device, connect the plasma welding torch, and preset the initial welding current and wire feed speed; set the response frequency of the dynamic push-pull device according to the wire feed speed and welding current. Step 2: Adjust the tungsten electrode retraction amount and set the welding current and wire feed speed change curves after signal triggering. Step 3: Start the plasma welding power supply and weld along the predetermined trajectory; when the welding ends, the computer control terminal triggers a control signal to control the dynamic push-pull device, so that the tungsten electrode retraction decreases from large to small until it is fully extended, and the welding current and wire feed speed change accordingly; maintain this for a certain period of time, and then turn off the welding power supply and wire feeder.

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