Submerged-arc welding device

Abstract

To provide a submerged-arc welding device loaded with a feeding variable speed control circuit that can quickly return an arc length to a set value, even if the arc length varies in a direction in which the length remarkably shortens during welding.SOLUTION: A submerged-arc welding device is provided with: a feeder WM that feeds a welding wire 1; a voltage detection circuit VD that detects a welding voltage corresponding to an arc length and outputs a voltage detection signal Vd; a voltage setting circuit VR that outputs a voltage setting signal Vr for setting the welding voltage; and a feeding variable speed control circuit FMC that performs variable speed control of feeding speed Fw of the welding wire 1 by the feeder WM on the basis of an error between the voltage detection signal Vd and the voltage setting signal Vr. The feeding variable speed control circuit FMC performs acceleration of feeding speed Fw in forward feeding, deceleration of the feeding speed Fw in forward feeding or backward feeding, on the basis of the error.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a submerged arc welding device equipped with variable feed speed control. [Background technology]

[0002] A submerged arc welding method has been disclosed in which the arc length can be controlled by variable feed speed control that changes the feed speed of the welding wire in response to the welding voltage (see, for example, Patent Document 1).

[0003] In variable feed speed control, the welding voltage, which correlates with the arc length, is maintained at an appropriate value by feedback-controlling the feed speed based on the error between the detected value and the set value of the welding voltage. In submerged arc welding using a thick wire, the wire melting rate is unlikely to change even if the welding current changes, so it is difficult to obtain the self-regulation of the arc length that is generally used in consumable electrode arc welding using a welding power source with constant voltage characteristics. For this reason, in submerged arc welding, the arc length is maintained at an appropriate value by performing variable feed speed control using a welding power source with constant current characteristics.

[0004] In the variable feed speed control, when the detected value of the welding voltage is greater than the set value, the arc length is longer than the set value, so the feed speed is accelerated to shorten the arc length and bring it closer to the set value. Conversely, when the detected value of the welding voltage is less than the set value, the arc length is shorter than the set value, so the feed speed is decelerated to lengthen the arc length and bring it closer to the set value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-271944 Summary of the Invention [Problem to be solved by the invention]

[0006] In variable feed speed control, when the detected value of the welding voltage is significantly greater than the set value, the arc length is significantly longer than the set value, so the arc length can be quickly shortened to approach the set value by drastically accelerating the feed speed. Also, when the detected value of the welding voltage is significantly smaller than the set value, the arc length is significantly shorter than the set value, so it is desirable to quickly lengthen the arc length to approach the set value by drastically decelerating the feed speed. However, in the variable feed speed control of the prior art, the feed speed can only be decelerated to 0 m / min, so there is a problem in that the arc length cannot be quickly lengthened from a significantly short state to the set value.

[0007] Therefore, an object of the present invention is to provide a submerged arc welding device equipped with variable feed speed control that can quickly return the arc length to a set value even if the arc length fluctuates in the direction of significantly shortening it. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the invention of claim 1 comprises: a feeding machine that feeds a welding wire; a voltage detection circuit for detecting a welding voltage corresponding to an arc length and outputting a voltage detection signal; a voltage setting circuit that outputs a voltage setting signal for setting the welding voltage; a variable feed speed control circuit that controls an arc length by variably controlling a feed speed of the welding wire by the feeder based on an error between the voltage detection signal and the voltage setting signal; In a submerged arc welding apparatus comprising: The feed variable speed control circuit accelerates the feed speed of the forward feed, decelerates the feed speed of the forward feed, or reverses the feed based on the error. The submerged arc welding apparatus is characterized by the above.

[0009] The invention of claim 2 is as follows: the variable feed speed control circuit controls the feed speed including the reverse feed speed when the voltage detection signal is smaller than the voltage setting signal; 2. The submerged arc welding device according to claim 1,

[0010] The invention of claim 3 is as follows: the variable feed speed control circuit sets the feed speed to the reverse feed speed when the absolute value of the error is equal to or greater than a reference value when the voltage detection signal is smaller than the voltage setting signal; 3. The submerged arc welding device according to claim 2, wherein: Effect of the Invention

[0011] According to the submerged arc welding device of the present invention, even if the arc length fluctuates in a direction that significantly shortens it, the arc length can be quickly returned to the set value, thereby stabilizing the welding condition. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a submerged arc welding device according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a waveform diagram of a welding current Iw and a welding voltage Vw. [Diagram 3] 2 is a timing chart of each signal in the welding equipment of FIG. 1 , illustrating variable feed speed control when the current contact tip-base metal distance Lw is significantly shortened during welding to significantly shorten the arc length. [Figure 4] 2 is a timing chart of each signal in the welding equipment of FIG. 1 , illustrating variable feed speed control when the distance Lw between the power contact tip and the base metal is slightly shortened during welding to slightly shorten the arc length. [Diagram 5] 2 is a timing chart of each signal in the welding equipment of FIG. 1 , illustrating variable feed speed control when the current contact tip-base metal distance Lw is increased to increase the arc length during welding. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0014] 1 is a block diagram of a submerged arc welding device according to an embodiment of the present invention, each block of which will be described below with reference to the drawing.

[0015] The main power supply circuit PM is connected to a commercial power supply (not shown) such as a three-phase 200V power supply, and receives as input a current error amplification signal Ei (described later) and a polarity switching signal Spn (described later), performs inverter control in accordance with the current error amplification signal Ei, and switches between electrode positive polarity EP and electrode negative polarity EN in accordance with the polarity switching signal Spn to output AC welding current Iw and welding voltage Vw. Although not shown, this power supply main circuit PM includes a primary rectifier that rectifies the commercial power supply, a smoothing capacitor that smoothes the rectified DC, a primary-side inverter circuit that converts the smoothed DC into high-frequency AC, a high-frequency transformer that steps down the high-frequency AC to a voltage value suitable for welding, a secondary rectifier that rectifies the stepped-down high-frequency AC into DC, a reactor that smoothes the rectified DC, a secondary-side inverter circuit that switches the smoothed DC between electrode positive polarity EP and electrode negative polarity EN in accordance with a polarity switching signal Spn, a modulation circuit that receives as input the current error amplified signal Ei and outputs a pulse-width modulated signal, and a drive circuit that receives as input the pulse-width modulated signal to drive the switching elements of the primary-side inverter circuit.

[0016] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 coupled to a feeder WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between a power feed tip (not shown) of the welding torch 4 and the base material 2, and a welding current Iw flows. A flux feeder 6 supplies flux (not shown) to the arc generating part. The arc generating part is covered with the flux, so the arc 3 cannot be seen from the outside. The welding torch 4 is mounted on a cart, a robot, or the like, and moves along the weld line.

[0017] The current detection circuit ID detects the instantaneous value of the AC welding current Iw, converts it into an absolute value, and outputs a current detection signal Id.

[0018] The RMS current detection circuit IED receives the current detection signal Id, calculates an effective value from the current detection signal Id, and outputs an RMS current detection signal Ied. The RMS current setting circuit IER outputs a predetermined RMS current setting signal Ier. The current amplitude modulation circuit AMC receives the RMS current detection signal Ied and the RMS current setting signal Ier, performs modulation control based on the error amplification value of both values, and outputs a current amplitude modulation signal Amc. This circuit changes the amplitude of the welding current Iw so that the effective value of the welding current Iw becomes equal to the set value.

[0019] The electrode positive polarity period setting circuit TPR outputs a predetermined electrode positive polarity period setting signal Tpr, and the electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0020] The current setting circuit IR receives the electrode positive polarity period setting signal Tpr, the electrode negative polarity period setting signal Tnr, and the current amplitude modulation signal Amc as inputs, performs the following processes 1) to 3), and outputs a current setting signal Ir having a half-sine waveform, as well as a polarity switching signal Spn for switching the power supply polarity. 1) During the electrode positive polarity period Tep set by the electrode positive polarity period setting signal Tpr, the start and end points of the period become the polarity switching current value, and a half-wave sine wave having an amplitude set by the current amplitude modulation signal Amc is output as the current setting signal Ir. During the electrode positive polarity period Tep, a polarity switching signal Spn that is at a High level is output. 2) During the electrode negative polarity period Ten set by the electrode negative polarity period setting signal Tnr, the start and end points of the period are the polarity switching current value, and a half-sine wave waveform with an amplitude set by the current amplitude modulation signal Amc is output as the current setting signal Ir. During the electrode negative polarity period Ten, a polarity switching signal Spn that is at a low level is output. 3) Repeat steps 1) and 2) above.

[0021] The current error amplifier circuit EI receives the current setting signal Ir and the current detection signal Id, amplifies the error between the two values, and outputs a current error amplified signal Ei. This circuit controls the welding device to have a constant current.

[0022] The voltage detection circuit VD detects the effective value of the AC welding voltage Vw and outputs a voltage detection signal Vd. The voltage detection signal Vd is a value that correlates with the arc length, so it detects the arc length. The voltage setting circuit VR outputs a predetermined voltage setting signal Vr for setting the desired arc length.

[0023] The variable feed speed control circuit FMC receives the voltage detection signal Vd and the voltage setting signal Vr, performs the variable feed speed control shown below based on the error between these two values, and outputs a feed speed modulation signal Fmc. 1) The variable feed speed control changes the value of the feed speed modulation signal Fmc based on the error by increasing (accelerating), decreasing (decelerating) or decreasing it to a negative value (reverse feed speed). 2) Preferably, the variable feed speed control varies the value of the feed speed modulation signal Fmc, including decreasing it to a negative value (reverse feed speed), when the voltage detection signal Vd is smaller than the voltage setting signal Vr. 3) More preferably, the variable feed speed control reduces the value of the feed speed modulation signal Fmc to a negative value (reverse feed speed) when the absolute value of the error is equal to or greater than a reference value when the voltage detection signal Vd is smaller than the voltage setting signal Vr.

[0024] The feed control circuit FC receives the feed speed modulation signal Fmc and outputs a feed control signal Fc to the feeder WM for controlling the feed speed Fw of the welding wire 1 to a speed determined by the feed speed modulation signal Fmc.

[0025] 2 is a waveform diagram of the welding current Iw and the welding voltage Vw, in which positive values ​​above 0 A and 0 V correspond to the electrode positive polarity EP, and negative values ​​below 0 V correspond to the electrode negative polarity EN.

[0026] As shown in FIG. 1A, during an electrode positive polarity period Tep from time t1 to t2, the welding current Iw has a positive polarity switching current value at the start point t1 and end point t2 of the period, and has a positive half-wave waveform of a sine wave with an amplitude set by the current amplitude modulation signal Amc. As shown in FIG. 1A, during an electrode negative polarity period Ten from time t2 to t3, the welding current Iw has a negative polarity switching current value at the start point t2 and end point t3 of the period, and has a negative half-wave waveform of a sine wave with an amplitude set by the current amplitude modulation signal Amc. The electrode positive polarity period Tep is set by the electrode positive polarity period setting signal Tpr in FIG. 1. The electrode negative polarity period Ten is set by the electrode negative polarity period setting signal Tnr in FIG. 1. The amplitude is modulated and controlled so that the current effective value detection signal Ied in FIG. 1 is equal to the current effective value setting signal Ier. For example, Tep=10 ms, Ten=10 ms, polarity switching current value=±200A, and amplitude=±1000A.

[0027] As shown in Fig. 1B, the welding voltage Vw has a waveform similar to a square wave. The effective value of the welding voltage Vw is a value that correlates with the arc length.

[0028] Figure 3 is a timing chart of each signal in the welding equipment of Figure 1, showing variable feed speed control when the distance Lw between the current contact tip and the base metal is significantly shortened during welding to significantly shorten the arc length. Figure 3(A) shows the change over time in the distance Lw between the current contact tip and the base metal, figure 3(B) shows the change over time in the voltage detection signal Vd which correlates with the arc length, and figure 3(C) shows the change over time in the feed speed Fw. The operation of each signal will be explained below with reference to the figures.

[0029] The voltage detection signal Vd detects the effective value of the AC welding voltage Vw, and is a value correlated with the arc length. The feed speed Fw is set by the feed speed modulation signal Fmc in Fig. 1 through variable feed speed control based on the error between the voltage detection signal Vd and the voltage setting signal Vr in Fig. 1.

[0030] At time t1 during welding, for example, if the welding torch mounted on the welding robot is moved downward rapidly and significantly, the distance Lw between the power contact tip and the base metal becomes shorter in a step-like manner, as shown in FIG. 1A. In response to this, the voltage detection signal Vd also decreases significantly in a step-like manner, as shown in FIG. 1B, and the arc length becomes significantly shorter. Here, the value of the voltage detection signal Vd becomes smaller than the value of the voltage setting signal Vr, and the absolute value of the error between the two values ​​becomes equal to or greater than the reference value. As a result, as shown in FIG. 1C, the feed speed Fw decreases from time t1 to a negative value with a slope, and becomes the reverse feed speed. After that, it rises from the negative peak value with a gentle slope, passes 0 at time t2, and converges to a constant positive value at time t3. Since the welding wire is fed in the reverse direction until time t2, the voltage detection signal Vd increases rapidly as shown in FIG. 1B, and converges to the constant value before time t1 at time t3. The arc length increases rapidly and returns to the set value before time t1 at time t3.

[0031] As described above, when the arc length fluctuates so as to become significantly shorter, the feed speed transitionally becomes reverse feed speed and the tip of the welding wire is pulled up, so that the arc length quickly becomes longer and returns to the set value.

[0032] Figure 4 is a timing chart of each signal in the welding equipment of Figure 1, showing variable feed speed control when the distance Lw between the current contact tip and the base metal is slightly shortened during welding to slightly shorten the arc length. Figure 4(A) shows the time change in the distance Lw between the current contact tip and the base metal, figure 4(B) shows the time change in the voltage detection signal Vd which correlates with the arc length, and figure 4(C) shows the time change in the feed speed Fw. The operation of each signal will be explained below with reference to the figures.

[0033] At time t1 during welding, for example, if the welding torch mounted on the welding robot is moved downward rapidly and slightly, the distance Lw between the power contact tip and the base metal shortens in a step-like manner, as shown in FIG. 1A. In response to this, the voltage detection signal Vd also decreases in a step-like manner in a small amount, as shown in FIG. 1B, and the arc length shortens in a small amount. Here, the value of the voltage detection signal Vd becomes smaller than the value of the voltage setting signal Vr, and the absolute value of the error between the two values ​​becomes less than the reference value. As a result, as shown in FIG. 1C, the feed speed Fw decreases in a positive value range with a slope from time t1, and decelerates. After that, it rises with a gentle slope, and at time t2, it converges to the constant value before time t1. Since the feed speed decelerates, the voltage detection signal Vd increases as shown in FIG. 1B, and at time t2, it converges to the constant value before time t1. The arc length lengthens and returns to the set value before time t1 at time t2.

[0034] As described above, when the arc length fluctuates to become slightly shorter, the feed speed is transiently slowed down and the melting rate of the welding wire becomes greater than the feed speed, so that the arc length becomes longer and returns to the set value.

[0035] Figure 5 is a timing chart of each signal in the welding equipment of Figure 1, showing variable feed speed control when the distance Lw between the power contact tip and the base metal is increased during welding to increase the arc length. Figure 5(A) shows the change over time in the distance Lw between the power contact tip and the base metal, figure 5(B) shows the change over time in the voltage detection signal Vd which correlates with the arc length, and figure 5(C) shows the change over time in the feed speed Fw. The operation of each signal will be explained below with reference to the figures.

[0036] At time t1 during welding, for example, if the welding torch mounted on the welding robot is moved upward rapidly, the distance Lw between the power contact tip and the base metal increases in a stepwise manner, as shown in FIG. 1A. In response to this, the voltage detection signal Vd also increases in a stepwise manner, as shown in FIG. 1B, and the arc length increases. Here, the value of the voltage detection signal Vd becomes greater than the value of the voltage setting signal Vr. As a result, as shown in FIG. 1C, the feed speed Fw increases with a slope from time t1 and accelerates. Thereafter, it decreases with a gentle slope and converges to the constant value before time t1 at time t2. Since the feed speed accelerates, the voltage detection signal Vd decreases as shown in FIG. 1B, and converges to the constant value before time t1 at time t2. The arc length shortens and returns to the set value before time t1 at time t2.

[0037] As described above, when the arc length is changed to be longer, the feed speed is transiently accelerated and the melting rate of the welding wire becomes smaller than the feed speed, so that the arc length becomes shorter and returns to the set value.

[0038] The effects of this embodiment will be described below. According to this embodiment, the variable feed speed control circuit accelerates the forward feed speed, decelerates the forward feed speed, or reverses the feed speed based on the error between the voltage detection signal and the voltage setting signal. When the arc length fluctuates in the direction of increasing the length during welding, the value of the voltage detection signal becomes larger than the value of the voltage setting signal, and the feed speed is transiently accelerated. As a result, the melting speed of the welding wire becomes smaller than the feed speed, so the arc length becomes shorter and returns to the set value. When the arc length fluctuates in the direction of decreasing the length slightly during welding, the value of the voltage detection signal becomes smaller than the value of the voltage setting signal, and the feed speed is transiently decelerated. As a result, the melting speed of the welding wire becomes larger than the feed speed, so the arc length becomes longer and returns to the set value. When the arc length fluctuates in the direction of decreasing the length significantly during welding, the value of the voltage detection signal becomes larger than the value of the voltage setting signal, and the feed speed is transiently reversed. As a result, the tip of the welding wire is directly pulled up, so the arc length quickly becomes longer and returns to the set value. As described above, in this embodiment, even if the arc length fluctuates in the direction of increasing or decreasing the length, the feed speed is accelerated, decelerated, or reversed, so that the arc length can be quickly returned to the set value.

[0039] More preferably, according to this embodiment, the variable feed speed control circuit controls the feed speed including the reverse feed speed when the voltage detection signal is smaller than the voltage setting signal. In this way, when the arc length fluctuates in a direction that significantly shortens it, the welding wire is transiently reversed, so that the tip of the welding wire can be directly pulled up. As a result, the arc length can be rapidly lengthened and quickly returned to the set value.

[0040] More preferably, according to this embodiment, the variable feed speed control circuit sets the feed speed to the reverse feed speed when the absolute value of the error is equal to or greater than a reference value when the voltage detection signal is smaller than the voltage setting signal. In this way, when the arc length fluctuates in a direction that significantly shortens the arc length, the welding wire is transiently fed in the reverse direction by making the absolute value of the error equal to or greater than the reference value. As a result, the tip of the welding wire is directly pulled up by the reverse feed, and the arc length is rapidly lengthened, allowing it to be quickly restored to the set value. [Explanation of symbols]

[0041] 1 Welding wire 2 Base material 3. Arc 4. Welding torch 5 Feeding roll 6 Flux supply machine AMC Current Amplitude Modulation Circuit Amc Current Amplitude Modulation Signal EI Current Error Amplifier Circuit Ei Current error amplification signal EN Electrode negative polarity EP electrode positive polarity FC feed control circuit Fc feed control signal FMC Variable speed feed control circuit Fmc Feed speed modulation signal Fw Feeding speed ID Current Detection Circuit Id Current detection signal IED Current Effective Value Detection Circuit Ied Current effective value detection signal IER Current effective value setting circuit Ier Current effective value setting signal IR current setting circuit Ir Current setting signal Iw Welding current Lw Distance between power supply tip and base material PM power supply main circuit SPN polarity switching signal Ten electrode negative polarity period Tep electrode positive polarity period TNR Electrode negative polarity period setting circuit Tnr Electrode negative polarity period setting signal TPR electrode positive polarity period setting circuit Tpr electrode positive polarity period setting signal VD voltage detection circuit Vd Voltage detection signal VR voltage setting circuit Vr Voltage setting signal Vw welding voltage WM Send to Machine

Claims

1. a feeding machine that feeds a welding wire; a voltage detection circuit for detecting a welding voltage corresponding to an arc length and outputting a voltage detection signal; a voltage setting circuit that outputs a voltage setting signal for setting the welding voltage; a variable feed speed control circuit that controls an arc length by variably controlling a feed speed of the welding wire by the feeder based on an error between the voltage detection signal and the voltage setting signal; In a submerged arc welding apparatus comprising: The feed variable speed control circuit accelerates the feed speed of the forward feed, decelerates the feed speed of the forward feed, or reverses the feed based on the error. A submerged arc welding apparatus comprising:

2. the variable feed speed control circuit controls the feed speed including the reverse feed speed when the voltage detection signal is smaller than the voltage setting signal; 2. The submerged arc welding apparatus according to claim 1 .

3. the variable feed speed control circuit sets the feed speed to the reverse feed speed when the absolute value of the error is equal to or greater than a reference value when the voltage detection signal is smaller than the voltage setting signal; 3. The submerged arc welding apparatus according to claim 2.

Images