Submerged arc welding control method and submerged arc welding device

Abstract

The invention provides a submerged arc welding control method and a submerged arc welding device. In a submerged arc welding control method, a welding current (Iw) and a welding voltage (Vw), which are the values of a current setting value (Is) and a voltage setting value (Vs), are output, and setting and management of welding conditions are made good. In a submerged arc welding control method for welding by feeding a welding wire and outputting a welding current (Iw) and a welding voltage (Vw) corresponding to a set external characteristic, a current setting value (Is) and a voltage setting value (Vs) are set, the external characteristic is set to a characteristic passing through an intersection point (A) of the current setting value (Is) and the voltage setting value (Vs), and the slope at the intersection point (A) is a negative value. The feed speed of the welding wire is controlled in a variable speed manner so that the welding voltage (Vw) becomes equal to the voltage set value (Vs), and the operating points of the welding current (Iw) and the welding voltage (Vw) converge at the intersection (A) of the external characteristics.

Description

Technical Field

[0001] This invention relates to a submerged arc welding control method and a submerged arc welding apparatus. Background Technology

[0002] Submerged arc welding (SAW) is known to date. SAW involves distributing granular flux onto the base metal, feeding a welding wire into the flux, and creating an electric arc between the tip of the wire and the base metal to perform welding. In SAW, by flowing a large current through a thick-diameter welding wire, thick plates can be welded with high efficiency.

[0003] Submerged arc welding method that uses variable speed control of the wire feed rate based on welding voltage to control the arc length (e.g., see Patent Document 1).

[0004] In variable speed control, the feed rate is controlled by feedback based on the error between the detected welding voltage and the voltage setpoint, maintaining the welding voltage, which is related to the arc length, at an appropriate value. In submerged arc welding using large-diameter welding wire, the change in wire melting rate is small even with variations in welding current, making it difficult to achieve the self-control of the arc length typically used in consumable electrode arc welding with constant voltage characteristics. Therefore, in submerged arc welding, variable speed control using a welding power source with constant current characteristics is employed to maintain the arc length at an appropriate value.

[0005] In variable speed control, when the detected welding voltage is greater than the voltage setpoint, the arc length is longer than the desired value. Therefore, the arc length is shortened by increasing the feed rate to bring it closer to the desired value. Conversely, when the detected welding voltage is less than the voltage setpoint, the arc length is shorter than the desired value. Therefore, the arc length is lengthened by decreasing the feed rate to bring it closer to the desired value.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 9-271944 Summary of the Invention

[0009] In variable speed control, when the detected welding voltage is significantly higher than the voltage setpoint, the arc length is significantly longer than the desired value. Therefore, it is preferable to rapidly shorten the arc length by drastically accelerating the feed rate to bring it closer to the desired value. Conversely, when the detected welding voltage is significantly lower than the voltage setpoint, the arc length is significantly shorter than the desired value. Therefore, it is preferable to rapidly extend the arc length by drastically decelerating the feed rate to bring it closer to the desired value. However, in variable speed control, if the gain is set too high to drastically accelerate / decelerate the feed rate, the feed rate becomes too sensitive, leading to an unstable welding state. Therefore, in existing variable speed control technology, the gain cannot be set too high, thus converging to the state where the error between the detected welding voltage and the voltage setpoint remains.

[0010] In submerged arc welding, welders primarily set and manage welding conditions by configuring current and voltage settings. Therefore, ensuring that the welding current and voltage are output according to the current and voltage settings is crucial for setting and managing welding conditions. In existing variable speed control technologies, the welding current is controlled by a constant current, thus always matching the current setting. On the other hand, as mentioned above, the welding voltage inherently contains errors compared to the voltage setting, posing a problem for setting and managing welding conditions.

[0011] Therefore, the object of the present invention is to provide a submerged arc welding control method and submerged arc welding apparatus that can output welding current and welding voltage such as current setting value and voltage setting value, and improve the setting and management of welding conditions.

[0012] The submerged arc welding control method provided by the first aspect of the present invention feeds a welding wire and outputs a welding current and a welding voltage corresponding to a set external characteristic for welding. The method is characterized by setting a current setting value and a voltage setting value, setting the external characteristic to a value that passes through the intersection of the current setting value and the voltage setting value with a negative slope at the intersection, and performing variable speed control on the feed speed of the welding wire to make the welding voltage equal to the voltage setting value, so that the operating points of the welding current and the welding voltage converge to the intersection of the external characteristic.

[0013] As an example, the submerged arc welding control method of the present invention is characterized in that the slope is set in the range of -5V / 100A or less and -25V / 100A or more.

[0014] As an example, the submerged arc welding control method of the present invention is characterized in that, when the output is AC, the welding current and the welding voltage are set to effective values ​​or average values.

[0015] As an example, the submerged arc welding control method of the present invention is characterized in that the gain of the variable speed control is set such that the absolute value of the error between the convergence value of the welding voltage and the voltage setting value is greater than or equal to 0.1V and less than or equal to 1V.

[0016] As an example, the submerged arc welding control method of the present invention is characterized in that the gain of the variable speed control is set such that the absolute value of the error between the convergence value of the effective value or average value of the welding voltage and the voltage setting value is greater than or equal to 0.1V and less than 1V.

[0017] The submerged arc welding apparatus provided by the second aspect of the present invention feeds a welding wire and outputs a welding current and a welding voltage corresponding to a set external characteristic for welding. The submerged arc welding apparatus sets a current setting value and a voltage setting value, sets the external characteristic to a value that passes through the intersection of the current setting value and the voltage setting value with a negative slope at the intersection, and performs variable speed control on the feeding speed of the welding wire to make the welding voltage equal to the voltage setting value, so that the operating points of the welding current and the welding voltage converge to the intersection of the external characteristic.

[0018] -Invention Effects-

[0019] Based on the above structure, for example, regarding submerged arc welding control methods and submerged arc welding apparatus, welding current and welding voltage such as current setting values ​​and voltage setting values ​​can be output, and the setting and management of welding conditions become better. Attached Figure Description

[0020] Figure 1 This is a block diagram of a welding apparatus for implementing the submerged arc welding control method according to embodiments of the present invention.

[0021] Figure 2 When it is in DC output mode Figure 1 Timing diagram of each signal in the welding device.

[0022] Figure 3 When the welding current is a sinusoidal waveform in AC output mode, Figure 1 Timing diagram of each signal in the welding device.

[0023] Figure 4 This is a diagram illustrating the relationship between the external characteristics of the submerged arc welding control method involved in the embodiments of the present invention and the operating points of the welding current and welding voltage.

[0024] -Explanation of Figure Markers-

[0025] 1: Welding wire, 2: Base material, 3: Arc, 4: Welding torch, 5: Feed roller, 6: Flux feeder, AMC: Current amplitude modulation circuit, Amc: Current amplitude modulation signal, AT: Automatic trolley, CC: External characteristic control circuit, EI: Current error amplifier circuit, Ei: Current error amplifier signal, EN: Electrode negative polarity, EP: Electrode positive polarity, FC: Feed control circuit, Fc: Feed control signal, FMC: Variable feed speed control circuit, Fmc: Feed speed modulation signal, Fw: Feed speed, GR: Gain setting circuit, Gr: Gain setting signal, IAR: AC current setting circuit, Iar: AC current setting signal, ICR: Current control setting circuit, Icr: Current control setting signal, ID: Current detection circuit, Id: Current detection signal, Idr: DC current setting signal, IED: Current RMS / Average Value Detection Circuit The circuit diagram is as follows: Ied: Current RMS / Average Value Detection Signal, IS: Current Setting Circuit, Is: Current Setting Signal, Iw: Welding Current, MR: Output Mode Setting Circuit, Mr: Output Mode Setting Signal, PM: Power Supply Main Circuit, SPN: Polarity Switching Setting Circuit, Spn: Polarity Switching Signal, t: Time, Ten: Electrode Negative Polarity Period, Tep: Electrode Positive Polarity Period, TNR: Electrode Negative Polarity Period Setting Circuit, Tnr: Electrode Negative Polarity Period Setting Signal, Tpn: Polarity Signal, TPR: Electrode Positive Polarity Period Setting Circuit, Tpr: Electrode Positive Polarity Period Setting Signal, VD: Voltage Detection Circuit, Vd: Voltage Detection Signal, VED: Voltage RMS / Average Value Detection Circuit, Ved: Voltage RMS / Average Value Detection Signal, VS: Voltage Setting Circuit, Vs: Voltage Setting Signal, Vw: Welding Voltage, WM: Feed Machine. Detailed Implementation

[0026] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in this specification, the average value refers to the average of the absolute values ​​of the values.

[0027] Figure 1 This is a block diagram of a welding apparatus for implementing the submerged arc welding control method according to embodiments of the present invention. Hereinafter, each block will be described with reference to this diagram.

[0028] The main power supply circuit PM is connected to a commercial power supply such as a three-phase 200V power supply (illustration omitted). It takes the current error amplification signal Ei (described later) and the polarity switching signal Spn (described later) as inputs, performs inverter control according to the current error amplification signal Ei, and switches the positive polarity EP and negative polarity EN of the electrode according to the polarity switching signal Spn, outputting AC or DC welding current Iw and welding voltage Vw. Although the illustration is omitted, the main power supply circuit PM includes: a primary rectifier for rectifying commercial power; a smoothing capacitor for smoothing the rectified DC; a primary-side inverter circuit for converting the smoothed DC into high-frequency AC; a high-frequency transformer for stepping down the high-frequency AC to a voltage suitable for welding; a secondary rectifier for rectifying the stepped-down high-frequency AC into DC; a reactor for smoothing the rectified DC; a secondary-side inverter circuit for switching the smoothed DC to positive electrode polarity EP and negative electrode polarity EN according to the polarity switching signal Spn; a modulation circuit that takes the current error amplification signal Ei as input and outputs a pulse width modulation signal; and a drive circuit that takes the pulse width modulation signal as input and drives the switching element of the primary-side inverter circuit.

[0029] The welding wire 1 is fed into the welding torch 4 by the rotation of the feed roller 5, which is connected to the feed machine WM, generating an arc 3 between the wire and the base material 2. A welding voltage Vw is applied between the power supply nozzle (not shown) of the welding torch 4 and the base material 2, and a welding current Iw is supplied. The flux supply machine 6 supplies flux (not shown) to the arc generating section. The arc generating section is covered by flux, so the arc 3 cannot be seen from the outside.

[0030] The automatic trolley AT is equipped with the aforementioned welding torch 4 and the aforementioned flux supply machine 6. During welding, flux is distributed from the flux supply machine 6 while the front end of the welding torch 4 moves along the welding line at a predetermined speed.

[0031] The output mode setting circuit MR outputs an output mode setting signal Mr, wherein the output mode setting signal Mr is high level in AC output mode and low level in DC output mode.

[0032] The current setting circuit IS outputs a predetermined current setting signal Is. The voltage setting circuit VS outputs a predetermined voltage setting signal Vs.

[0033] The voltage detection circuit VD detects the instantaneous value of the welding voltage Vw and converts it into an absolute value, outputting a voltage detection signal Vd.

[0034] The voltage RMS / Average Value Detection Circuit VED takes the voltage detection signal Vd mentioned above as input, calculates the RMS or average value based on its value, and outputs the voltage RMS / Average Value Detection Signal Ved.

[0035] The external characteristic control circuit CC takes the above-mentioned current setting signal Is, the above-mentioned voltage setting signal Vs, the above-mentioned output mode setting signal Mr, the above-mentioned voltage RMS / average value detection signal Ved and the above-mentioned voltage detection signal Vd as inputs, and outputs the current RMS / average value setting signal Ier and the DC current setting signal Idr calculated based on the following equation (1) or (2).

[0036] 1) When the output mode setting signal Mr is high (AC output mode)

[0037] The external characteristics are the output characteristics of the welding power source, which can be expressed as a function Ve = f(Ie) that takes the effective or average value Ie of the welding current Iw as input and the effective or average value Ve of the welding voltage Vw as output. If the function is defined as a straight line with a slope K passing through the intersection point of the current setting signal Is and the voltage setting signal Vs, it becomes the following equation.

[0038] Ve=K·(Ie-Is)+Vs

[0039] Here, the slope K is a negative value, set within the range of -5 (V / 100A). Rearranging the above equation with Ie, replacing Ie with the current RMS / average value setting signal Ier, and replacing Ve with the voltage RMS / average value detection signal Ved, yields the following equation.

[0040] Ier=(Ved-Vs) / K+Is (1) Formula

[0041] In AC output mode, this formula is used for output control based on external characteristics.

[0042] 2) Output mode setting signal Mr = low level (DC output mode)

[0043] In the above equation (1), if Ier is replaced with Idr and Ved is replaced with Vd, then it becomes the following equation.

[0044] Idr=(Vd-Vs) / K+Is (2) Formula

[0045] In DC output mode, this formula is used for output control based on external characteristics.

[0046] The current detection circuit ID detects the instantaneous value of the welding current Iw and converts it into an absolute value, outputting the current detection signal Id.

[0047] The current RMS / Average Value Detection Circuit IED takes the aforementioned current detection signal Id as input, calculates the RMS or average value based on its value, and outputs the current RMS / Average Value Detection Signal Ied.

[0048] The current amplitude modulation circuit AMC takes the aforementioned effective / average current detection signal Ied and the aforementioned effective / average current setting signal Ier as inputs, performs modulation control based on the error amplification of the two values, and outputs a current amplitude modulation signal Amc. Through this circuit, the amplitude of the welding current changes so that the effective or average value of the welding current Iw becomes equal to the value of the effective / average current setting signal Ier.

[0049] The electrode positive polarity period setting circuit TPR outputs a predetermined electrode positive polarity period setting signal Tpr. The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0050] The AC current setting circuit IAR takes the above-mentioned electrode positive polarity period setting signal Tpr, the above-mentioned electrode negative polarity period setting signal Tnr, and the above-mentioned current amplitude modulation signal Amc as inputs, performs the following processing, and outputs an AC current setting signal Iar of a half-cycle waveform of sine wave or rectangular wave (including trapezoidal wave), and outputs a polarity signal Tpn.

[0051] 1) During the positive polarity period Tep, set by the positive polarity period setting signal Tpr, the start and end points of the period become predetermined polarity switching current values. The half-cycle waveform of a sine wave or rectangular wave (including trapezoidal waves) with an amplitude set by the current amplitude modulation signal Amc is output as the AC current setting signal Iar. During the positive polarity period Tep, the output becomes a high-level polarity signal Tpn.

[0052] 2) Next, during the negative polarity period Ten, set by the negative polarity period setting signal Tnr, the start and end points of the period become the aforementioned polarity switching current values. A half-cycle waveform of a sine wave or rectangular wave (including trapezoidal waves) with an amplitude set by the current amplitude modulation signal Amc is output as the AC current setting signal Iar. During the negative polarity period Ten, a low-level polarity signal Tpn is output.

[0053] 3) Repeat steps 1) and 2) above.

[0054] The polarity switching setting circuit SPN takes the above-mentioned output mode setting signal Mr and the above-mentioned polarity signal Tpn as inputs, performs the following processing, and outputs the polarity switching signal Spn.

[0055] 1) When the output mode setting signal Mr is high (AC output mode) and the polarity signal Tpn is high (positive electrode polarity EP), the output becomes a high-level polarity switching signal Spn.

[0056] 2) When the output mode setting signal Mr is high (AC output mode) and the polarity signal Tpn is low (electrode negative polarity EN), the output becomes a low-level polarity switching signal Spn.

[0057] 3) When the output mode setting signal Mr is low (DC output mode), the polarity switching signal Spn is high when welding with the positive electrode polarity EP, and low when welding with the negative electrode polarity EN.

[0058] The current control setting circuit ICR takes the above-mentioned output mode setting signal Mr, the above-mentioned AC current setting signal Iar, and the above-mentioned DC current setting signal Idr as inputs, performs the following processing, and outputs the current control setting signal Icr.

[0059] 1) When the output mode setting signal Mr is high (AC output mode), the output AC current setting signal Iar is used as the current control setting signal Icr.

[0060] 2) When the output mode setting signal Mr is low (DC output mode), the output DC current setting signal Idr is used as the current control setting signal Icr.

[0061] The current error amplifier circuit EI takes the aforementioned current control setting signal Icr and the aforementioned current detection signal Id as inputs, amplifies the error between the two values, and outputs the current error amplified signal Ei.

[0062] The gain setting circuit GR outputs a predetermined gain setting signal Gr.

[0063] The variable speed control circuit FMC takes the output mode setting signal Mr, the voltage RMS / average value detection signal Ved, the voltage detection signal Vd, the voltage setting signal Vs, and the gain setting signal Gr as inputs, performs the following processing, and outputs the feed speed modulation signal Fmc. This circuit performs variable speed control on the feed speed Fw to maintain the arc length at an appropriate value.

[0064] 1) When the output mode setting signal Mr is high (AC output mode), the error between the voltage effective value / average value detection signal Ved and the voltage setting signal Vs is amplified by the value of the gain setting signal Gr, and variable speed control based on P (proportional) control, PI (proportional / integral) control or PID (proportional-integral / derivative) control is performed, and the feed speed modulation signal Fmc is output.

[0065] 2) When the output mode setting signal Mr is low (DC output mode), the error between the voltage detection signal Vd and the voltage setting signal Vs is amplified by the value of the gain setting signal Gr, and variable speed control based on P (proportional) control, PI (proportional / integral) control or PID (proportional / integral / derivative) control is performed, and the feed speed modulation signal Fmc is output.

[0066] The feed control circuit FC takes the aforementioned feed speed modulation signal Fmc as input and outputs the feed control signal Fc, which is used to control the feed speed Fw of the welding wire 1 to the speed determined by the feed speed modulation signal Fmc, to the aforementioned feed machine WM.

[0067] Figure 2 When it is in DC output mode Figure 1 The following is a timing diagram of the signals in the welding apparatus. Diagram (A) shows the time variation of the welding current Iw, diagram (B) shows the time variation of the welding voltage Vw, and diagram (C) shows the time variation of the polarity switching signal Spn. The operation of each signal will be explained below with reference to these diagrams.

[0068] This diagram illustrates the case where the output mode is DC output and the output polarity is positive (EP). Therefore, as shown in (C) of the diagram, the polarity switching signal Spn remains high throughout the entire period, becoming positive (EP).

[0069] Submerged arc welding is performed under welding conditions where there is no short circuit between the welding wire and the base metal; therefore, the entire period is called the arc period. As shown in Figure (A), the welding current Iw is a DC waveform and is controlled as follows: Figure 1 The value of the DC current setting signal Idr is calculated by inputting the voltage detection signal Vd into equation (2) above. Thus, output control based on external characteristics is performed. As shown in Figure (B), the welding voltage Vw becomes a DC waveform, becoming a value related to the arc length. The feed speed Fw of the welding wire (not shown) is variable-speed controlled so that the voltage detection signal Vd becomes related to the arc length. Figure 1 The voltage setting signal Vs is equal to the voltage setting signal Vs. Therefore, the arc length is controlled.

[0070] When the output polarity is the negative electrode polarity EN, the polarity switching signal Spn shown in Figure (C) remains low throughout the entire period. Furthermore, the welding current Iw and welding voltage Vw exhibit negative waveforms.

[0071] Figure 3 When the welding current is a sinusoidal waveform in AC output mode, Figure 1The following is a timing diagram of the signals in the welding apparatus. Diagram (A) shows the time variation of the welding current Iw, diagram (B) shows the time variation of the welding voltage Vw, and diagram (C) shows the time variation of the polarity switching signal Spn. The operation of each signal will be explained below with reference to these diagrams.

[0072] In this diagram, the positive values ​​above 0A and 0V represent the positive electrode polarity EP, while the negative values ​​below represent the negative electrode polarity EN.

[0073] During the period from time t1 to t2, as shown in Figure (C), the polarity switching signal Spn becomes high, becoming the positive electrode polarity EP. As shown in Figure (A), during the positive electrode polarity period Tep from time t1 to t2, the welding current Iw has positive polarity switching current values ​​at the start of the period t1 and the end of the period t2, becoming a half-cycle waveform of the positive value of a sine wave with an amplitude set by the current amplitude modulation signal Amc. During the period from time t2 to t3, as shown in Figure (C), the polarity switching signal Spn becomes low, becoming the negative electrode polarity EN. As shown in Figure (A), during the negative electrode polarity period Ten from time t2 to t3, the welding current Iw has negative polarity switching current values ​​at the start of the period t2 and the end of the period t3, becoming a half-cycle waveform of the negative value of a sine wave with an amplitude set by the current amplitude modulation signal Amc. Time t1 to t3 is then repeated. The positive electrode polarity period Tep passes through... Figure 1 The electrode positive polarity is set by the signal Tpr. The electrode negative polarity is set by... Figure 1 The negative polarity of the electrode is set by the signal Tnr. Figure 1 The effective value / average value setting signal Ier is input to the effective value / average value detection signal Ved in equation (1) above to calculate the current. The amplitude of the welding current is modulated and controlled so that... Figure 1 The current RMS / average value detection signal Ied becomes equal to the current RMS / average value setting signal Ier. Thus, output control based on external characteristics is performed. For example, Tep = 10ms, Ten = 10ms, polarity switching current value = ±200A, amplitude ±1000A.

[0074] As shown in Figure (B), the welding voltage Vw forms a waveform similar to a rectangular wave. The effective or average value of the welding voltage Vw becomes a value related to the arc length. Figure 1 The feed rate Fw is variable-speed controlled so that the voltage RMS / average value detection signal Ved becomes consistent with... Figure 1 The voltage setting signal Vs is equal to the voltage setting signal Vs. Therefore, the arc length is controlled.

[0075] The above describes the case where the welding current Iw is a sinusoidal waveform, but there are also cases where it is a rectangular waveform (including trapezoidal waveforms).

[0076] Figure 4 This is a graph illustrating the relationship between the external characteristics of the submerged arc welding control method according to embodiments of the present invention and the operating points of the welding current and welding voltage. The horizontal axis of the graph represents the welding current Iw, and the vertical axis represents the welding voltage Vw. The following description refers to this graph.

[0077] This diagram shows the case where the output is DC. The external characteristics shown in this diagram are those that pass through... Figure 1 The current setting signal Is and Figure 1 The voltage setting signal Vs intersects at point A and forms a downward-sloping straight line with a negative value K. The action points of the welding current Iw = Is and the welding voltage Vw = Vs converge at point A, and the arc length becomes an appropriate value. If, from this state, the arc length shortens due to external disturbances such as irregular movement of the molten pool, changes in the distance between the welding nozzle and the base material, or temporary changes in the feed rate, the welding current Iw changes to a value greater than Is (Iw1), and the welding voltage Vw changes to a value less than Vs (Vw1). The action point moves to the lower right (B) in terms of external characteristics. The welding current Iw1 at action point B is greater than the welding current Is at intersection A, therefore the wire melting speed increases, and the arc length changes in the direction of lengthening. Furthermore, the welding voltage Vw1 at action point B is a value less than the voltage setting signal Vs, therefore, the feed rate is reduced by variable speed control, and the arc length changes in the direction of lengthening. The aforementioned effects based on external characteristics and the effects based on variable speed control overlap, causing the action points of welding current Iw and welding voltage Vw to quickly recover from point B to point A, and the arc length to return to an appropriate value.

[0078] If, starting from the point of action at intersection point A, the arc length increases due to external disturbances, the welding current Iw changes to Iw2, which is smaller than Is, and the welding voltage Vw changes to Vw2, which is larger than Vs. The point of action moves to the upper left (point C) in terms of external characteristics. Since the welding current Iw2 at point C is smaller than the welding current Is at intersection point A, the wire melting speed slows down, and the arc length shortens. Furthermore, the welding voltage Vw2 at point C is larger than the voltage setting signal Vs, so the feed rate is accelerated through variable speed control, further shortening the arc length. The combined effects of external characteristics and variable speed control cause the point of action for both welding current Iw and welding voltage Vw to quickly return from point C to intersection point A, and the arc length returns to its appropriate value.

[0079] In the prior art, the welding current Iw is controlled by a constant current, thus maintaining a constant wire melting speed. Therefore, when the arc length changes, the feed rate is controlled by a variable speed to restore the arc length to an appropriate value. As mentioned above, if the gain of the variable speed control is increased, the feed rate becomes too sensitive to changes, the welding state becomes unstable, and therefore the gain cannot be set to a large value. As a result, in the prior art, the convergence value of the welding voltage Vw includes an error from the value of the voltage setting signal Vs, leading to a larger steady-state deviation. That is, in the prior art, arc length control results in a state with large steady-state deviation and slow transient response.

[0080] In contrast, in this embodiment, because the effects of external characteristics and variable speed control are superimposed, the steady-state deviation of arc length control can be reduced and the transient response can be accelerated even without increasing the gain of variable speed control. As a result, in this embodiment, the convergence values ​​of welding current Iw and welding voltage Vw become equal to the current setting signal Is and the voltage setting signal Vs, thus improving the setting and management of welding conditions.

[0081] When the output is AC, set the horizontal axis to the effective or average value of the welding current Iw and the vertical axis to the effective or average value of the welding voltage Vw.

[0082] The effects of this embodiment will now be explained. According to this embodiment, in the submerged arc welding control method, a current setpoint and a voltage setpoint are set, and an external characteristic is set to a value that passes through the intersection of the current setpoint and the voltage setpoint with a negative slope. Furthermore, variable speed control is applied to the feed rate so that the welding voltage becomes equal to the voltage setpoint, causing the operating points of the welding current and welding voltage to converge at the intersection of the external characteristic. In this embodiment, the effects based on the external characteristic and the effects based on variable speed control are superimposed, thus reducing the steady-state deviation of the arc length control and accelerating the transition response. As a result, in this embodiment, the convergence values ​​of the welding current and welding voltage become equal to the current setpoint and the voltage setpoint, thus improving the setting and management of welding conditions. The external characteristic only needs to be a value with a negative slope at the aforementioned intersection point; it does not need to be... Figure 4 The straight line mentioned above can also be a broken line, curve, etc., with different slopes according to each of the multiple intervals of the welding current.

[0083] More preferably, according to this embodiment, the slope of the external characteristic is set in the range of -5V / 100A or less and -25V / 100A or more. If the slope is greater than -5V / 100A, the change in welding current accompanying the change in arc length becomes too sensitive, resulting in an unstable welding state. When the slope is less than -25V / 100A, the change in welding current accompanying the change in arc length becomes smaller, and the effect of restoring the arc length to an appropriate value becomes smaller. Therefore, if the slope is set within the above range, the effect of restoring the arc length to an appropriate value can be increased while maintaining a stable welding state. More preferably, the slope setting range is set to -10V / 100A or less and -20V / 100A or more.

[0084] More preferably, according to this embodiment, when the output is AC, the welding current and welding voltage are set to effective values ​​or average values. This allows this embodiment to be applied even when the output is AC.

[0085] More preferably, according to this embodiment, the gain of the variable speed control is set such that the absolute value of the error between the convergence value of the welding voltage and the voltage setting value is 0.1V or more and 1V or less. If the gain of the variable speed control is set such that the absolute value of the error is less than 0.1V, the feed rate becomes too sensitive to changes, resulting in an unstable welding state. If the gain of the variable speed control is set such that the absolute value of the error is greater than 1V, the steady-state deviation from the voltage setting value becomes large, adversely affecting the setting and management of welding conditions. If the gain of the variable speed control is set within the above range, it is possible to maintain a stable welding state so that the steady-state deviation does not adversely affect the setting and management of welding conditions. More preferably, the gain of the variable speed control is set such that the absolute value of the error is 0.3V or more and 0.8V or less.

[0086] More preferably, according to this embodiment, the gain of the variable speed control is set such that the absolute value of the error between the convergence value of the effective value or average value of the welding voltage and the voltage setting value is 0.1V or more and 1V or less. Even when the output is AC, if the gain of the variable speed control is set to the above range, it is possible to maintain a stable welding state so that the steady-state deviation does not adversely affect the setting and management of welding conditions.

[0087] Furthermore, according to this embodiment, in a submerged arc welding apparatus that feeds welding wire and outputs welding current and welding voltage corresponding to a set external characteristic for welding, the submerged arc welding apparatus sets a current setting value and a voltage setting value, sets the external characteristic to a value that passes through the intersection of the current setting value and the voltage setting value and has a negative slope at the intersection point, and performs variable speed control on the feed speed so that the welding voltage becomes equal to the voltage setting value, and the operating points of the welding current and welding voltage converge to the intersection point of the external characteristic. The submerged arc welding apparatus according to this embodiment can achieve the above-described effects.

Claims

1. A submerged arc welding control method, comprising feeding a welding wire and outputting a welding current and welding voltage corresponding to preset external characteristics for welding, characterized in that, Set current and voltage settings, set the external characteristic to a value that passes through the intersection of the current and voltage settings and has a negative slope at the intersection, and perform variable speed control on the wire feed speed so that the welding voltage becomes equal to the voltage setting value, and the operating points of the welding current and the welding voltage converge to the intersection of the external characteristic.

2. The submerged arc welding control method according to claim 1, characterized in that, The slope is set in the range of -5V / 100A to -25V / 100A.

3. The submerged arc welding control method according to claim 1 or 2, characterized in that, When the output is AC, the welding current and the welding voltage are set to effective values ​​or average values.

4. The submerged arc welding control method according to claim 1 or 2, characterized in that, The gain of the variable speed control is set such that the absolute value of the error between the convergence value of the welding voltage and the voltage setting value is greater than 0.1V and less than 1V.

5. The submerged arc welding control method according to claim 3, characterized in that, The gain of the variable speed control is set such that the absolute value of the error between the effective value or average value of the welding voltage and the voltage setting value is greater than 0.1V and less than 1V.

6. A submerged arc welding apparatus, comprising feeding a welding wire and outputting a welding current and welding voltage corresponding to preset external characteristics for welding, characterized in that, The submerged arc welding device sets a current setting value and a voltage setting value, sets the external characteristic to a value that passes through the intersection of the current setting value and the voltage setting value and has a negative slope at the intersection, and performs variable speed control on the feed speed of the welding wire so that the welding voltage becomes equal to the voltage setting value, and the operating points of the welding current and the welding voltage converge to the intersection of the external characteristic.

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