CN101524781B - AC arc welding system and method thereof - Google Patents

Abstract

The invention relates to an AC input arc welding system and method, belonging to the field of welding equipment and automation. This system adopts the wire feeding mode of push-pull wire, and the power supply adopts the AC output mode, which specifically includes welding power supply system and wire feeding system. The welding power supply system mainly includes a main circuit part (1) that directly provides power output for welding and a control circuit part (2) that controls the output power of the main circuit. The wire feeding system uses an AC servo motor as the wire feeding machine, and receives the signal from the DSP system (A) through the wire feeding system control interface circuit (E). The wire feeding motor performs reciprocating motion to realize push-pull wire feeding. At the same time, the welding power supply judges that the welding is in a short-circuit/arcing state according to the feedback voltage, and changes the output polarity of the power supply. The droplet short-circuit transition is completed under the pulling force of the welding wire, and a small short-circuit current is used. In addition, the DC positive connection is used at the initial stage of the arc, so that more energy of the arc is distributed to the welding wire, and the heat input to the base metal is greatly reduced.

Description

An AC arc welding system and method

technical field

The invention relates to an AC input arc welding system and method, belonging to the field of welding equipment and automation.

Background technique

Low energy input arc welding is a welding method for thin plates, which is still in its infancy. At present, there are two main welding methods, one is called cold metal transition welding (CMT), and the other is called cold arc welding. Both welding methods use the droplet transfer method of short-circuit transfer, but their process characteristics are quite different. For the first form, the push-pull wire feeding method is adopted, and a specially designed wire feeding system is used. The wire feeder completes the forward and reverse actions at a high frequency, and the short circuit signal is detected during the welding process and fed back to the wire feeder. The wire feeder responds by withdrawing the welding wire, thereby separating the welding wire from the droplet and reducing the energy input. The second form adopts the continuous forward wire feeding method, uses the ordinary wire feeding system with the waveform control technology of short-circuit transition, and uses the welding wire with specific components to reduce the welding energy input. However, no matter what kind of process is used, there are big shortcomings: the CMT method still uses DC reverse connection mode to work, although the energy is reduced in the short circuit stage, but because the short circuit energy itself is very small, the reduction of the heat input of the base metal is limited. It is only slightly lower than the traditional surface tension transition method (STT); the cold arc welding method uses a special welding wire, which is not easy to promote, and also uses the DC reverse connection working method, which cannot effectively reduce energy. In the early stage of Beijing University of Technology, the over-push and wire-drawing method was used to realize low-energy welding, and different methods were used to achieve similar functions to CMT, but the power supply also adopted the form of DC reverse connection, and a large part of the heat during the arcing period was used to heat the base metal. Therefore, there is still a lot of room for energy reduction.

Contents of the invention

Based on the deficiencies of existing low-energy input arc welding methods, the present invention proposes a new AC input arc welding system and method. output polarity. The droplet short-circuit transition is completed under the pulling force of the welding wire, and a small short-circuit current can be used. In addition, the DC positive connection is used at the initial stage of arcing, so that more energy of the arc is distributed to the welding wire, and the heat input to the base metal is further reduced.

The low-energy arc welding system proposed by the present invention is composed of two parts: a welding power supply system and a wire feeding system.

The welding power supply system includes a main circuit part 1 directly providing power output for welding and a control circuit part 2 for adjusting the output power of the main circuit part 1 . Control circuit part 2 includes DSP system A, primary inverter drive and protection circuit B, peripheral equipment control and execution part C, man-machine interface D, wire feeding system control interface circuit E, secondary inverter drive and protection circuit F. in:

DSP system A is connected with part B to part F, receives the current and voltage signals of the main circuit part, and outputs control signals. The primary and secondary inverter drive and protection circuits B and F receive the signal from the DSP controller, perform isolation and amplification, and drive the IGBT on and off of the primary and secondary inverter parts. Peripheral equipment control and execution part C includes torch switch C1 and gas valve C2. Both C1 and C2 are connected to DSP system A, C1 provides welding switch signal to A, and C2 receives A's instruction to provide shielding gas for the welding process. The man-machine interface D realizes the display of welding parameters and the preset of welding parameters. The wire feeding system control interface circuit E is connected to the wire feeding system 3 .

The wire feeding system uses an AC servo motor as a wire feeding machine, and the wire feeding system control interface circuit E in the control circuit part 2 receives the signal from the DSP system A.

The control method of the low-energy arc welding system proposed by the present invention is as follows: In this method, the wire feeding system performs high-frequency reciprocating wire feeding, and the droplet transfer is completed under the joint action of the pulling force of the welding wire and the electromagnetic contraction force. The welding power controller judges whether the welding process is in the short-circuit or arc-burning stage according to the welding voltage feedback signal, and adopts current values of different polarities in different stages. Specific steps are as follows:

1) Determine welding parameters according to actual requirements: including wire feeding speed V, initial short circuit current Idc, initial short circuit time Tdc, positive polarity current Ien, positive polarity peak time Tap, negative polarity peak current Ibp, negative polarity peak time Tbp, negative polarity Input the above welding parameters into the DSP system A through the man-machine interface D.

2) The DSP system A detects whether the welding torch switch C2 is turned on, and if so, the wire feeding system 3 is started through the wire feeding system control interface circuit E, and the DSP system A judges whether the welding process is in the short circuit or arc burning stage through the received welding voltage feedback signal.

In the short-circuit stage, firstly, the wire feeding system 3 controls the motor to advance the welding wire, and the DSP system A sends out a control signal to pass through the secondary inverter drive and protection circuit F, and then drives the secondary inverter part 1.7 to reverse the polarity of the power output, that is, the workpiece is the cathode The welding wire is the anode, and at the same time, the DSP system A controls the primary inverter part 1.3 through the primary inverter drive and the protection circuit B, so that the power supply outputs the initial short-circuit current Idc, and maintains the action time Tdc; then, the DSP system A sends out a control signal, and passes through part F Drive the secondary inverter part 1.7 to make the power supply output positive polarity, that is, the workpiece is the anode and the welding wire is the cathode, and the positive polarity current Ien is given by the primary inverter part 1.3, and the wire feeding system 3 controls the motor to draw back the welding wire. Under the action of tension, the short-circuit transition of the droplet is completed, and the smooth re-ignition of the arc is ensured.

In the arcing stage, when the DSP system A detects the arcing signal through the feedback voltage of the power output part 1.8, it enters the arcing stage. At this time, the welding wire continues to be drawn back, the positive polarity of the power output remains unchanged, and the workpiece is still anodic welding wire Still the cathode. When the positive polarity peak time Tap arrives, DSP system A outputs a control signal, drives the secondary inverter part 1.7 through part F, and reverses the polarity of the power supply output, that is, the workpiece is the cathode welding wire and the anode, and at the same time, DSP system A is controlled by part B The primary inverter part 1.3 makes the power supply output negative polarity peak current Ibp. After the negative polarity peak current Ibp acts for time Tbp, the DSP system A controls the primary inverter part 1.3 through the part B, so that the power supply outputs the negative polarity base value current Ibb, and the wire feeding system 3 controls the motor to advance the welding wire.

The value range of the wire feeding speed V is 3-7m/min, the initial short-circuit current Idc generally takes a value of 3-100A, the initial short-circuit current action time Tdc is 0.5-5ms, and the positive polarity current Ien takes a value of 20-100A. 150A, the value of the positive polarity peak time Tap is 0~5ms, the value range of the negative polarity peak current Ibp is 120~300A, the value range of the negative polarity peak time Tbp is 0.1~3ms, the value range of the negative polarity base current Ibb It is 10~50A.

The whole welding process is composed of the forward and backward drawing of the welding wire and different multi-stage currents. Through reasonable parameter coordination, a stable welding process can be realized.

Compared with the prior art, the control method and arc welding system adopted in the present invention have the following advantages:

1) The energy input in the welding process is low, and the process is stable and reliable. The method of the invention combines the AC welding power supply with the push-pull wire feeding system; in the short-circuit stage, the output polarity of the power supply is changed, and the AC commutation is easily realized, and at the same time, the pulling force of the welding wire is used to ensure that the short-circuit transition is completed in a small current state; DC positive connection is adopted, and reverse connection is adopted in the later stage, which can reasonably distribute the distribution ratio of arc energy between the welding wire and the workpiece, further reduce the heat input to the workpiece, and easily realize the adjustment of the arc length to ensure the stability of the arc;

2) The wire feeding system adopts AC servo motor as the wire feeding machine, which has extremely high dynamic response performance, and the wire feeding process is accurate and controllable;

3) Wide range of applications: it can be applied to surface surfacing, welding of ultra-thin plates and galvanized steel sheets, effectively preventing burn-through of weldments and volatilization of galvanized protective layers, and has broad application prospects.

Description of drawings

Figure 1 Structural composition diagram of welding system

Figure 2 Main program software scheme diagram

Figure 3 welding program block diagram

Figure 4 Current Waveform Diagram

Detailed ways

The present embodiment will now be described with reference to the drawings. (embodiment carries out the welding of butt weld seam at the 3A21 aluminum alloy plate of 1mm thickness)

A specific example of the present invention, the structure of the low-energy input arc welding system is shown in Figure 1, which generally includes two parts: a welding system and a wire feeding system.

The welding system includes a main circuit part 1 and a control circuit part 2 with TMS320F2812DSP as the core. The input voltage of the main circuit is three-phase 380V; the input rectification 1.1 is rectified by Fuji rectifier bridge, the model is FUJ6RI100G-160; the primary inverter circuit 1.3 adopts the half-bridge inverter structure, which is composed of two IGBTs whose model is BSM150GB120DN2; the intermediate frequency transformer 1.4 adopts The ultrafine crystal magnetic core has a transformation ratio of 15:2; the secondary filter 1.6 adopts a magnetic core saturated inductance, and the inductance is about 30 μH; the secondary inverter circuit 1.7 adopts a half-bridge inverter structure, which consists of two IGBTs of the type BSM150GB120DN2 composition. The control circuit part 2 adopts a control system based on TMS320F2812DSP, which mainly completes parameter calculation, proportional integral adjustment, sequence control, and can communicate with the wire feeding system 3 . It will be described in detail below in conjunction with the accompanying drawings.

Its working sequence is: the input three-phase 380V AC is rectified by the rectification part 1.1 and filtered by the primary filter 1.2, and becomes 540V DC, and then passes through the primary inverter circuit 1.3 (this is controlled by the control circuit part 2) inverter and intermediate frequency transformer 1.4 After step-down isolation, it becomes 20KHz alternating current, and after being filtered by output rectifier 1.5 and secondary filter 1.6, it becomes high-current low-voltage direct current for welding. Then, according to the control requirement, the secondary inverter part 1.7 switches the polarity of the direct current output, which is finally output by the welding power output 1.8. Since the working frequency of the above circuit is 20KHz, and the output inductance is also very small (about 30μH), adjusting the inverter switching frequency or pulse width can achieve microsecond level control, so this type of power supply has fast response and good dynamic performance.

The composition and functions of welding system control circuit part 2 are as follows:

DSP system A is mainly composed of TMS320F2812DSP, including three input parts. The first input part is the current and voltage value output from the welding power output 1.8, in which the current is controlled by PI (proportional integral control), and the current deviation is adjusted in real time to realize closed-loop control; the voltage value is used to monitor the welding status. The second input section is the torch switch signal C1 obtained from section C. The third input part comes from the welding parameter preset of the man-machine interface D to obtain the initial welding parameters. Part A, as the core control part, mainly completes the response to welding parameter input and external signals, and controls the four parts B, C, D, and E after software processing, calculation and conversion, so that the entire welding system can coordinate and complete the scheduled work. for welding purposes.

The wire feeding system 3 uses an AC servo motor as a wire feeding machine, and receives the signal from the DSP system A through the wire feeding system control interface circuit in the control circuit part 2 .

The program control of the present invention is divided into two parts: the program control of welding wire movement (ie, the rotation track of the wire feeding motor) and the program control of the welding process DSP system, which will be described in detail below.

Welding wire motion (that is, wire feeding motor rotation track) program control:

Determine the welding parameters according to the actual welding requirements, and determine the wire feeding frequency F (the number of times the welding wire advances and withdraws per second, the previous one is counted as one time) and the wire feeding step size d (every time) according to the wire feeding speed V in the welding parameters. The difference between the advance and retract distance of the welding wire). The wire feeding system control interface circuit E receives the signal from the DSP system A, and controls the wire feeding motor to move forward and backward according to the predetermined step length.

Welding process DSP system program control, refer to the program flow chart to describe this example in detail:

Figure 2 is a schematic diagram of the main program software for DSP control of low-energy inverter arc welding power supply. The software main program includes: initialization subroutine, parameter preset and display subroutine, delay subroutine, calculation subroutine and welding subroutine. The specific execution sequence of the main program is: after power-on reset, the program starts to run from the initial address, and the system first executes the initialization subroutine to complete the initial value setting of each welding parameter. Then execute the parameter preset subroutine. The preset wire feeding speed V is 3.5m/min, the initial short circuit current Idc is 20A, the initial short circuit time Tdc is 2ms, the positive polarity current Ien is 70A, the positive polarity peak time Tap is 1ms, and the negative polarity Welding parameters such as polar peak current Ibp of 80A, negative polarity peak time Tbp of 0.5ms, and negative polarity base current Ibb of 20A are used for welding process control. The preset welding parameters are used for welding process control, and then the relevant parameter setting display. Then judge whether the welding switch is turned on, if yes, turn on the pulse width modulation (that is, can output energy), start the motor, judge whether the arc striking is successful, if the arc striking is successful, enter the welding program, until the welding end signal is detected, turn off the pulse width modulation, Turn off the motor and exit the welding state. If there is no welding start signal, the previous program will be executed again after a certain time delay (such as 20ms). The control method of the present invention is mainly embodied in the control process of the wire feeding process and the current waveform of the welding machine.

Figure 3 and Figure 4 show the welding program block diagram and current waveform schematic diagram, which mainly carry out state judgment, sequence control and output different current parameters according to different sequences. The process is:

First, the welding wire advances to judge whether a short circuit occurs according to the feedback voltage. If a short circuit occurs, the DSP system A sends out a control signal and passes through the secondary inverter drive and protection circuit F to drive the secondary inverter part 1.7 to reverse the polarity of the power supply output, that is, the workpiece is the cathode and the welding wire is the anode. At the same time, the DSP system A passes through a The inverter drive and protection circuit B controls the primary inverter part 1.3, so that the power supply outputs the initial short-circuit current Idc, and lasts for a duration of Tdc; then, the DSP system A sends out a control signal, and drives the secondary inverter part 1.7 through part F to make the power supply output Positive polarity, that is, the workpiece is the anode and the welding wire is the cathode, and the positive polarity current Ien is given by the primary inverter part 1.3. The wire feeding system 3 controls the motor to draw the welding wire back, and under the pulling force of the welding wire, the droplet short circuit transition is completed.

Then judge whether arcing occurs according to the feedback voltage, if so, enter the arcing stage, at this time, the welding wire continues to be withdrawn, the positive polarity of the power output remains unchanged, and the workpiece is still anode and the welding wire is still cathode. When the positive polarity peak time Tap arrives, DSP system A outputs a control signal, drives the secondary inverter part 1.7 through part F, and reverses the polarity of the power supply output, that is, the workpiece is the cathode welding wire and the anode, and at the same time, DSP system A is controlled by part B The primary inverter part 1.3 makes the power supply output negative polarity peak current Ibp. After the negative polarity peak current Ibp acts for time Tbp, the DSP system A controls the primary inverter part 1.3 through the part B, so that the power supply outputs the negative polarity base value current Ibb, and the wire feeding system 3 controls the motor to advance the welding wire.

The whole process is to judge the welding state according to the feedback voltage, and combine the movement of the welding wire to give the corresponding power supply polarity and current value. The welding parameters and the movement of the welding wire are well combined to realize low-energy welding.

The above is an example of the system and its control method, and we can also make some changes to it. For example, the main circuit part can use the full-bridge inverter circuit instead of the half-bridge form, the control part can use other DSP or single-chip microcomputer instead of TMS320F2812 to realize its functions, and the wire-feeding motor and wire-feeding curve can be adjusted slightly. As long as its system and control ideas are consistent with those described in the present invention, it should be regarded as the scope of the present invention.

Claims (3)

1. an AC arc welding system comprises welding power source system and wire feed system, and described welding power source system comprises directly to be provided the main circuit part (1) of power output and be used to regulate the main circuit part for welding

(1) control circuit of power output part (2);

Described main circuit part (1) comprises input rectifying (1.1), a filtering (1.2), an inversion (1.3), intermediate-frequency transformer (1.4), output rectifier (1.5), secondary filtering (1.6), secondary inversion (1.7) and the bonding power output (1.8) that connects successively;

Described control circuit part (2) comprises dsp system (A), the inversion driving and holding circuit (B), peripheral unit control and operating part (C), human-computer interaction interface (D) and the wire feed system control interface circuit (E) that link to each other with an inversion (1.3) of main circuit part; It is characterized in that: described control circuit part also comprises secondary inversion driving and the holding circuit (F) that is connected with secondary inversion in the main circuit part;

Dsp system (A) links to each other with the bonding power output (1.8) of main circuit part, receives the voltage signal of bonding power output (1.8);

Dsp system (A) links to each other with secondary inversion driving and holding circuit (F) with an inversion driving and holding circuit (B) respectively, an inversion driving and holding circuit (B) and secondary inversion driving and holding circuit (F) receive the signal of dsp system, isolate the break-make that drives the IGBT in an inversion (1.3) and the secondary inversion (1.7) after the amplification respectively;

Dsp system (A) links to each other with human-computer interaction interface (D), and human-computer interaction interface (D) is realized the demonstration of welding parameter and presetting of welding parameter;

Described peripheral unit control and operating part (C) comprise arc welding gun switch (C1) and air valve (C2), arc welding gun switch (C1) all links to each other with dsp system with air valve (C2), arc welding gun switch (C1) provides the welding switching signal for dsp system (A), and the instruction that air valve (C2) receives dsp system (A) provides protection gas to welding process;

Described wire feed system adopts AC servo motor to do wire-feed motor; Dsp system links to each other with wire feed system (3) by wire feed system control interface circuit (E); Wire feed system is accepted the signal that dsp system (A) sends by wire feed system control interface circuit.

2. a kind of AC arc welding system according to claim 1 is characterized in that: described wire feed system adopts the push-and-pull wire feeding mode, and described welding power source system adopts AC power.

3. use the welding control method of the described a kind of AC arc welding system of claim 1, it is characterized in that: wire feed system is done reciprocal wire feed, and the droplet transfer finishes under welding wire pumpback pulling force and electromagnetic contractile force acting in conjunction; The DSP control system judges that according to the weldingvoltage feedback signal welding process is in short circuit or arc stage, adopts the current value of opposed polarity in different phase; Its concrete steps are as follows:

Short-circuit stage: at first wire feed system (3) control motor advances welding wire, dsp system (A) makes power supply output reversed polarity by secondary inversion driving and holding circuit (F), be that workpiece is an anode for the negative electrode welding wire, dsp system (A) makes power supply output short-circuit initial stage electric current I dc by an inversion driving and holding circuit (B) simultaneously, after having acted on time T dc, dsp system (A) makes the power supply output cathode by secondary inversion driving and holding circuit (F) again, be that workpiece is a negative electrode for the anode welding wire, and provide positive polarity electric current I en by an inversion (1.3), wire feed system (3) control motor makes the welding wire pumpback, under the effect of welding wire pumpback pulling force, finish short circuiting transfer, and guarantee that electric arc ignites smoothly again;

Arc stage: after the feedback voltage of dsp system (A) by bonding power output (1.8) detects the arcing signal, promptly enter arc stage, this moment, welding wire continued to keep pumpback, and the power supply output cathode remains unchanged, and workpiece still be that the anode welding wire still is a negative electrode; After having acted on positive polarity time to peak Tap; dsp system (A) makes power supply output reversed polarity by secondary inversion driving and holding circuit (F); be that workpiece is an anode for the negative electrode welding wire; dsp system (A) makes power supply output negative pole peak point current Ibp by an inversion driving and holding circuit (B) simultaneously; negative polarity peak point current Ibp effect behind the time T bp; dsp system (A) makes power supply output negative pole background current Ibb by an inversion driving and holding circuit (B) again, and wire feed system (3) control motor advances welding wire.

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