Welding completion control method for consumable electrode arc welding

Abstract

To perform good welding completion control even when an arc length during transition to an antistick period becomes longer in consumable electrode arc welding.SOLUTION: In a welding completion control method for consumable electrode arc welding, when a welding completion signal On is input to a welding power source PS, a feed motor M of a welding wire 1 stops driving, and during an antistick period from the transient speed reduction of the feed motor M to stop through inertia to the end of welding, a welding voltage Vw is controlled on the basis of an antistick welding voltage setting value Var to end welding. The antistick welding voltage setting value Var is reduced when no short-circuiting occurs between the welding wire 1 and a base material 2 during a prescribed period from the time of transition to the antistick period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for controlling the end of consumable electrode arc welding. [Background technology]

[0002] In consumable electrode arc welding, welding end control (anti-stick control) is performed to prevent the welding wire from sticking to the molten pool at the end of welding and to optimize the size of the wire tip grains formed at the end of welding to improve the next arc start performance.

[0003] In the welding end control, when a welding end signal is input to the welding power source, the welding wire feed motor stops driving, and during the anti-stick period until the feed motor decelerates transiently due to inertia and stops and welding is ended, the welding voltage is controlled based on the anti-stick welding voltage set value to end the welding (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2023-62926 A Summary of the Invention [Problem to be solved by the invention]

[0005] If the arc length at the time of transition to the anti-stick period fluctuates due to welding conditions such as the distance between the power contact tip and the base metal, the welding position, and the welding voltage setting, the distance between the tip of the welding wire and the base metal at the end of welding and the grain size at the tip of the welding wire will fluctuate. In particular, if the arc length at the time of transition to the anti-stick period becomes longer than the appropriate value, the distance between the tip of the welding wire and the base metal at the end of welding will be longer than the appropriate value and the grain size at the tip will also be larger than the appropriate size, resulting in a problem of poor performance in starting the next arc.

[0006] Therefore, an object of the present invention is to provide a method for controlling the end of welding in consumable electrode arc welding, which can prevent the distance between the tip of the welding wire and the base metal and the tip grain size at the end of welding from becoming excessive, even if the arc length becomes long when transitioning to the anti-stick period. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the invention of claim 1 comprises: In a method for controlling the end of welding in consumable electrode arc welding, when a welding end signal is input to a welding power source, a welding wire feed motor stops driving, and the feeding motor decelerates transiently due to inertia and stops, and during an anti-stick period until welding is ended, the welding voltage is controlled based on an anti-stick welding voltage set value to end the welding, When no short circuit occurs between the welding wire and the base metal during a predetermined period from the transition point to the anti-stick period, the anti-stick welding voltage set value is decreased. The present invention relates to a method for controlling the end of consumable electrode arc welding.

[0008] The invention of claim 2 is as follows: reducing the anti-stick welding voltage setting value when the short circuit does not occur during the predetermined period and the welding voltage after the predetermined period has elapsed is equal to or higher than a reference value; 2. The method for controlling a welding termination in consumable electrode arc welding according to claim 1,

[0009] The invention of claim 3 is as follows: Decreasing the anti-stick welding voltage setting value to 0V; 3. The method for controlling a welding termination in consumable electrode arc welding according to claim 1 or 2. Effect of the Invention

[0010] According to the method for controlling the end of consumable electrode arc welding of the present invention, even if the arc length becomes longer when transitioning to the anti-stick period, the distance between the tip of the welding wire and the base metal and the tip grain size at the end of welding can be prevented from becoming excessively large, thereby preventing the next arc start from being poor. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram of a welding power source PS for carrying out a method for controlling welding termination in consumable electrode arc welding according to an embodiment of the present invention. [Diagram 2] 2 is a first timing chart of each signal in the welding power source of FIG. 1, illustrating a method for controlling the welding termination in consumable electrode arc welding according to an embodiment of the present invention. [Diagram 3] 4 is a second timing chart of each signal in the welding power source of FIG. 1 , illustrating the welding termination control method for consumable electrode arc welding according to the embodiment of the present invention. [Figure 4] 4 is a third timing chart of each signal in the welding power source of FIG. 1 , illustrating the welding termination control method for consumable electrode arc welding according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] 1 is a block diagram of a welding power source PS for carrying out a method for controlling the welding termination of consumable electrode arc welding according to an embodiment of the present invention. Each block will be described below with reference to the diagram.

[0014] The main power supply circuit PM receives a commercial power supply (not shown) such as three-phase 200V as input, performs output control such as thyristor phase control and inverter control in accordance with a drive signal Dv described later, and outputs a welding voltage Vw and welding current Iw suitable for arc welding.

[0015] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 connected to a feed motor M, and an arc 3 is generated between the welding wire 1 and the base metal 2. A welding voltage Vw is applied between the welding wire 1 and the base metal 2, and a welding current Iw flows between the welding wire 1 and the base metal 2. A shielding gas (not shown) is sprayed from the tip of the welding torch 4.

[0016] The welding start / end circuit ON outputs the welding start / end signal On, which goes to High level (welding start signal) when welding starts and to Low level (welding end signal) when welding ends. This circuit is a switch attached to the welding torch 4. In the case of robot welding, this circuit is also built into the robot control device.

[0017] The anti-stick period setting circuit TAR outputs a predetermined anti-stick period setting signal Tar.

[0018] The period discrimination circuit SI receives the above welding start / end signal On and the above anti-stick period setting signal Tar as inputs, performs the following processing, and outputs a period discrimination signal Si. 1) When the welding start / end signal On is at a high level (welding starts), the steady welding period Tc is reached and the period discrimination signal Si=1 is output. 2) After that, when the welding start / end signal On changes to a low level (welding end), the period determination signal Si=2 is output from that point on during the anti-stick period Ta set by the anti-stick period setting signal Tar. 3) Thereafter, when the anti-stick period Ta ends, a period discrimination signal Si=0 is output to stop the output of the welding power supply.

[0019] The welding current setting circuit IR outputs a predetermined welding current setting signal Ir.

[0020] The feed speed setting circuit FR receives the above-mentioned welding current setting signal Ir as an input, and outputs a feed speed setting signal Fr calculated using a predetermined current-feed speed conversion function.

[0021] The welding voltage detection circuit VD detects the welding voltage Vw and outputs a welding voltage detection signal Vd. The welding current detection circuit ID detects the welding current Iw and outputs a welding current detection signal Id.

[0022] The short circuit determination circuit SD receives the above-mentioned welding voltage detection signal Vd as input, and outputs a short circuit determination signal Sd that goes to a High level when this value is less than the short circuit determination value (approximately 10 V) and determines that it is a short circuit period, and goes to a Low level when this value is equal to or greater than the short circuit determination value and determines that it is an arc period.

[0023] The feed control circuit FC receives the welding start / end signal On and the feed speed setting signal Fr as inputs, performs the following processing, and outputs a feed control signal Fc for controlling the feed motor M. 1) When the welding start / end signal On is at a high level (welding start signal), the welding wire 1 is fed at a constant feed speed Fw set by the feed speed setting signal Fr. 2) When the welding start / end signal On changes to a low level (welding end signal) and the anti-stick period Ta begins, the drive of the feed motor M is stopped. As a result, the feed speed Fw is decelerated by inertia.

[0024] The rotation speed of the feed motor M is controlled by the feed control signal Fc, and the welding wire 1 is fed at a feed speed Fw.

[0025] The steady-state welding voltage setting circuit VCR outputs a predetermined steady-state welding voltage setting signal Vcr.

[0026] The welding condition determination circuit AD receives the period determination signal Si, the short circuit determination signal Sd, and the welding voltage detection signal Vd, performs the following process 1) or 2), and outputs a welding condition determination signal Ad. 1) If the short circuit determination signal Sd does not become high level (short circuit) within a specified period from the time when the period determination signal Si changes to 2 (anti-stick period), a welding state determination signal Ad is output which becomes high level when the specified period has elapsed and becomes low level when the period determination signal Si changes to 0 (end of welding). 2) If the short circuit determination signal Sd does not become high level (short circuit) within a specified period from the point at which the period determination signal Si changes to 2 (anti-stick period) and the value of the welding voltage detection signal Vd after the specified period has elapsed is equal to or greater than a predetermined reference value, a welding state determination signal Ad is output which becomes high level when the specified period has elapsed and becomes low level when the period determination signal Si changes to 0 (end of welding).

[0027] The anti-stick welding voltage setting circuit VAR receives the above-mentioned welding state determination signal Ad as an input, and outputs an anti-stick welding voltage setting signal Var which is a predetermined anti-stick welding voltage initial value when the welding state determination signal Ad is at a low level, and which is an anti-stick welding voltage reduction value which is smaller than the anti-stick welding voltage initial value when the welding state determination signal Ad is at a high level. The anti-stick welding voltage reduction value may be set to 0 V.

[0028] The welding voltage setting circuit VR receives the period discrimination signal Si, the steady-state welding voltage setting signal Vcr, and the anti-stick welding voltage setting signal Var as inputs, performs the following processing, and outputs the welding voltage setting signal Vr. 1) When the period discrimination signal Si is 1 and it is the steady welding period Tc, the steady welding voltage setting signal Vcr is output as the welding voltage setting signal Vr. 2) When the period discrimination signal Si=2 is in the anti-stick period Ta, the anti-stick welding voltage setting signal Var is output as the welding voltage setting signal Vr.

[0029] The voltage error amplifier circuit EV amplifies the error between the welding voltage setting signal Vr and the welding voltage detection signal Vd, and outputs a voltage error amplified signal Ev.

[0030] The drive circuit DV receives the period discrimination signal Si and the voltage error amplified signal Ev as inputs, and outputs a drive signal Dv for driving the main power supply circuit PM based on the voltage error amplified signal Ev during the period when the period discrimination signal Si=1 or 2. Therefore, the welding power source PS performs output control during the steady welding period Tc and the anti-stick period Ta.

[0031] FIG. 2 is a first timing chart of each signal in the welding power source of FIG. 1, which shows the welding end control method for consumable electrode arc welding according to the embodiment of the present invention. This figure shows the case where the arc length at the time of transition to the anti-stick period is within the appropriate range, and the operation is the same as that of the prior art. FIG. 2(A) shows the change over time of the welding start / end signal On, FIG. 2(B) shows the change over time of the feed speed Fw, FIG. 2(C) shows the change over time of the welding current Iw, FIG. 2(D) shows the change over time of the welding voltage Vw, FIG. 2(E) shows the change over time of the welding voltage setting signal Vr, FIG. 2(F) shows the change over time of the drive signal Dv, and FIG. 2(G) shows the change over time of the welding state determination signal Ad. Hereinafter, the operation of each signal will be described with reference to FIG.

[0032] In the figure, the period before time t1 is the steady welding period Tc, and the period discrimination signal Si in Figure 1 becomes 1. The period from time t1 to t2 is the predetermined anti-stick period Ta, and the period discrimination signal Si becomes 2. Then, at time t2, when the anti-stick period Ta ends, the period discrimination signal Si becomes 0, and the welding power source stops output.

[0033] (1) Operation during the steady welding period Tc before time t1 During the steady welding period TC, as shown in FIG. 1(A), the welding start / end signal On is at a high level (welding starts). As shown in FIG. 1(B), the feed speed Fw is set to a value set by the feed speed setting signal Fr in FIG. 1. As shown in FIG. 1(E), the welding voltage setting signal Vr is set to a value set by the steady welding voltage setting signal Vcr in FIG. 1, and the welding power source is constant-voltage controlled so that the average value of the welding voltage Vw is this value. As shown in FIG. 1(D), the welding voltage Vw repeats a short-circuit period in which the short-circuit voltage value is several volts and an arc period in which the arc voltage value is several tens of volts. As shown in FIG. 1(C), the welding current Iw gradually increases during the short-circuit period and gradually decreases during the arc period. As shown in FIG. 1(F), the drive signal Dv is at a high level until time t2, and the welding power source outputs, and at time t2, it becomes a low level and the welding power source stops outputting.

[0034] (2) Operation during the anti-stick period Ta from time t1 to t2 At time t1, as shown in FIG. 1A, when the welding start / end signal On changes from a high level (welding start) to a low level (welding end), the anti-stick period Ta begins. In response to this, the driving of the feed motor M is stopped, and the feed speed Fw decelerates due to inertia and becomes 0 at time t13, as shown in FIG. 1B. At the same time, as shown in FIG. 1E, the welding voltage setting signal Vr decreases from the value of the steady welding voltage setting signal Vcr to the anti-stick welding voltage initial value set by the anti-stick welding voltage setting signal Var in FIG. 1. During this period, as shown in FIG. 1C and FIG. 1D, the short circuit period and the arc period are repeated. In FIG. 1C, a short circuit occurs from the transition time t1 to the anti-stick period Ta until the time t11 when a predetermined period has elapsed, and therefore the welding state determination signal Ad remains at a low level, as shown in FIG. 1G.

[0035] After that, as shown in FIG. 1D, at time t12 just before the feed rate Fw becomes 0, the final short circuit period ends and the final arc period begins. As shown in FIG. 1C, the welding current Iw during the final arc period becomes a small current value. During the final arc period, the arc length gradually becomes longer, and when the arc cannot be maintained at time t14, arc interruption occurs. When arc interruption occurs, the welding current Iw becomes 0A as shown in FIG. 1C, and the welding voltage Vw becomes a no-load voltage value of about 80V as shown in FIG. 1D. At time t2, when the anti-stick period Ta set by the anti-stick period setting signal Tar in FIG. 1 ends, the period discrimination signal Si=0, and the drive signal Dv becomes a low level as shown in FIG. 1F. In response to this, the output of the welding power source is stopped, and the welding voltage Vw becomes 0V as shown in FIG. 1D. This ends the welding. The anti-stick period Ta is set so that the period during which the no-load voltage is applied from time t14 to t2 is about 50 ms, and is set to, for example, 200 ms.

[0036] Fig. 3 is a second timing chart of each signal in the welding power source of Fig. 1, which shows the welding end control method for consumable electrode arc welding according to the embodiment of the present invention. This figure shows a case where the arc length at the time of transition to the anti-stick period is longer than the appropriate range, and the value of the anti-stick welding voltage setting signal Var is reduced. Fig. 3(A) shows the time change of the welding start / end signal On, Fig. 3(B) shows the time change of the feed speed Fw, Fig. 3(C) shows the time change of the welding current Iw, Fig. 3(D) shows the time change of the welding voltage Vw, Fig. 3(E) shows the time change of the welding voltage setting signal Vr, Fig. 3(F) shows the time change of the drive signal Dv, and Fig. 3(G) shows the time change of the welding state determination signal Ad. Hereinafter, the operation of each signal will be described with reference to the figure.

[0037] In this figure, the operation before time t1 is the same as in FIG. 2, and therefore the description will not be repeated.

[0038] (2) Operation during the anti-stick period Ta from time t1 to t2 At time t1, as shown in FIG. 1(A), when the welding start / end signal On changes from a high level (welding start) to a low level (welding end), the anti-stick period Ta is entered. In response to this, the driving of the feed motor M is stopped, and the feed speed Fw is decelerated by inertia and becomes 0 at time t12, as shown in FIG. 1(B). At the same time, as shown in FIG. 1(E), the welding voltage setting signal Vr decreases from the value of the steady welding voltage setting signal Vcr to the anti-stick welding voltage initial value set by the anti-stick welding voltage setting signal Var in FIG. 1. Here, 1) when no short circuit occurs from the transition time t1 to the anti-stick period Ta until time t11 when a predetermined period has elapsed, or 2) when no short circuit occurs until time t11 when a predetermined period has elapsed and the welding voltage at time t11 when the predetermined period has elapsed is equal to or higher than the reference value, the welding state determination signal Ad changes to a high level during the period from time t11 to t2, as shown in FIG. 1(G). In response to this, as shown in FIG. 1(E), at time t11, the welding voltage setting signal Vr decreases to the anti-stick welding voltage reduction value set by the anti-stick welding voltage setting signal Var in FIG. 1. Because the value of the welding voltage setting signal Vr has decreased, the arc length becomes shorter and a short circuit occurs. Then, as shown in FIG. 1(C) and FIG. 1(D), the short circuit period and the arc period are repeated. The above-mentioned predetermined period is set to a time at which the droplet does not grow large even if the arc period continues for a predetermined period, and is set to, for example, 10 ms. The above-mentioned reference value is set to a voltage value at which it is expected that the welding voltage is large due to the long arc length and that a short circuit will not occur early, and is set to, for example, 35 V.

[0039] After that, as shown in FIG. 1D, at time t12 just before the feed rate Fw becomes 0, the final short circuit period ends and the final arc period begins. As shown in FIG. 1C, the welding current Iw during the final arc period becomes a small current value. During the final arc period, the arc length gradually becomes longer, and when the arc cannot be maintained at time t14, arc interruption occurs. When arc interruption occurs, the welding current Iw becomes 0A as shown in FIG. 1C, and the welding voltage Vw becomes a no-load voltage value of about 80V as shown in FIG. 1D. At time t2, when the anti-stick period Ta set by the anti-stick period setting signal Tar in FIG. 1 ends, the period discrimination signal Si=0, and the drive signal Dv becomes a low level as shown in FIG. 1F. In response to this, the output of the welding power source is stopped, and the welding voltage Vw becomes 0V as shown in FIG. 1D. This ends the welding.

[0040] Fig. 4 is a third timing chart of each signal in the welding power source of Fig. 1, which shows the welding end control method for consumable electrode arc welding according to the embodiment of the present invention. This figure shows a case where the arc length at the time of transition to the anti-stick period is longer than the appropriate range, and the value of the anti-stick welding voltage setting signal Var is reduced to 0V. Fig. 4(A) shows the time change of the welding start / end signal On, Fig. 4(B) shows the time change of the feed speed Fw, Fig. 4(C) shows the time change of the welding current Iw, Fig. 4(D) shows the time change of the welding voltage Vw, Fig. 4(E) shows the time change of the welding voltage setting signal Vr, Fig. 4(F) shows the time change of the drive signal Dv, and Fig. 4(G) shows the time change of the welding state determination signal Ad. Hereinafter, the operation of each signal will be described with reference to the figure.

[0041] In this figure, the operation before time t1 is the same as in FIG. 2, and therefore the description will not be repeated.

[0042] (2) Operation during the anti-stick period Ta from time t1 to t2 At time t1, as shown in FIG. 1(A), when the welding start / end signal On changes from a high level (welding start) to a low level (welding end), the anti-stick period Ta is entered. In response to this, the driving of the feed motor M is stopped, and the feed speed Fw is decelerated by inertia and becomes 0 at time t13, as shown in FIG. 1(B). At the same time, as shown in FIG. 1(E), the welding voltage setting signal Vr decreases from the value of the steady welding voltage setting signal Vcr to the anti-stick welding voltage initial value set by the anti-stick welding voltage setting signal Var in FIG. 1. Here, 1) when no short circuit occurs from the transition time t1 to the anti-stick period Ta until time t11 when a predetermined period has elapsed, or 2) when no short circuit occurs until time t11 when a predetermined period has elapsed and the welding voltage at time t11 when the predetermined period has elapsed is equal to or higher than the reference value, the welding state determination signal Ad changes to a high level during the period from time t11 to t2, as shown in FIG. 1(G). In response to this, as shown in Fig. 1(E), at time t11 the welding voltage setting signal Vr decreases to the anti-stick welding voltage reduction value set by the anti-stick welding voltage setting signal Var in Fig. 1. In Fig. 1, this is the case where the anti-stick welding voltage reduction value is 0 V.

[0043] At time t11, as shown in Fig. 1(E), the welding voltage setting signal Vr becomes 0V, so that as shown in Fig. 1(D), the welding voltage Vw becomes 0V, and as shown in Fig. 1(C), the welding current Iw becomes 0A, the arc is extinguished, and welding ends. At time t2, when the anti-stick period Ta set by the anti-stick period setting signal Tar in Fig. 1 ends, the period discrimination signal Si becomes 0, and as shown in Fig. 1(F), the drive signal Dv becomes low level.

[0044] The effects of this embodiment will be described below. According to this embodiment, when no short circuit occurs between the welding wire and the base metal during a predetermined period from the transition to the anti-stick period, the anti-stick welding voltage set value is decreased. If the arc length at the time of transition to the anti-stick period is long, no short circuit occurs even in the anti-stick period, the arc period continues for a long time, and the droplets grow large, so that the distance between the welding wire tip and the base metal and the tip grain size at the end of welding become excessively large. In this embodiment, when the arc length at the time of transition to the anti-stick period is long and no short circuit occurs during the predetermined period, the anti-stick welding voltage set value is decreased. In this way, the welding voltage is reduced, and a short circuit occurs early, and the short circuit period and the arc period are repeated. As a result, it is possible to suppress the distance between the welding wire tip and the base metal and the tip grain size at the end of welding from becoming excessively large.

[0045] More preferably, according to this embodiment, when no short circuit occurs during a predetermined period and the welding voltage after the predetermined period is equal to or greater than a reference value, the anti-stick welding voltage set value is decreased. When no short circuit occurs during a predetermined period and the welding voltage after the predetermined period is equal to or greater than a reference value, this indicates a state in which a short circuit will not occur early even after the predetermined period has elapsed. In this embodiment, in this state, the anti-stick welding voltage set value is decreased. In this way, the welding voltage is reduced, causing a short circuit to occur early, and the short circuit period and the arc period are repeated. As a result, it is possible to prevent the distance between the welding wire tip and the base metal and the tip grain size from becoming excessive at the end of welding.

[0046] More preferably, according to this embodiment, the anti-stick welding voltage set value is reduced to 0 V. In this embodiment, when a state in which a short circuit does not occur early even after a predetermined period of time has passed, the anti-stick welding voltage set value is reduced to 0 V, thereby stopping the output of the welding voltage and welding current and extinguishing the arc. In this way, it is possible to prevent the arc period from continuing for a long time and the droplet from growing large, and therefore it is possible to prevent the distance between the welding wire tip and the base metal and the tip grain size from becoming excessive at the end of welding. [Explanation of symbols]

[0047] 1 Welding wire 2 Base material 3. Arc 4. Welding torch 5 Feeding roll AD Welding condition determination circuit Ad Welding status determination signal DV driver circuit Dv drive signal EV voltage error amplifier circuit Ev Voltage error amplified signal FC feed control circuit Fc feed control signal FR feed speed setting circuit Fr feed speed setting signal Fw Feed speed ID Welding current detection circuit Id Welding current detection signal IR welding current setting circuit Ir Welding current setting signal Iw Welding current M Feed motor ON Welding start / end circuit On Welding start / end signal PM power supply main circuit PS Welding Power Source SD Short circuit detection circuit Sd Short circuit detection signal SI period discrimination circuit Si Period discrimination signal TAR Anti-stick period setting circuit Tar anti-stick period setting signal VAR Anti-stick welding voltage setting circuit Var Anti-stick welding voltage setting signal VCR constant welding voltage setting circuit Vcr Constant welding voltage setting signal VD Welding voltage detection circuit Vd Welding voltage detection signal VR welding voltage setting circuit Vr Welding voltage setting signal Vw welding voltage

Claims

1. In a method for controlling the end of welding in consumable electrode arc welding, when a welding end signal is input to a welding power source, a welding wire feed motor stops driving, and the feeding motor decelerates transiently due to inertia and stops, and during an anti-stick period until welding is ended, the welding voltage is controlled based on an anti-stick welding voltage set value to end the welding, When no short circuit occurs between the welding wire and the base metal during a predetermined period from the transition point to the anti-stick period, the anti-stick welding voltage set value is decreased.

2. A method for controlling the end of consumable electrode arc welding.

2. reducing the anti-stick welding voltage setting value when the short circuit does not occur during the predetermined period and the welding voltage after the predetermined period has elapsed is equal to or higher than a reference value; 2. The method for controlling the end of consumable electrode arc welding according to claim 1.

3. Decreasing the anti-stick welding voltage setting value to 0 V; 3. The method for controlling the end of consumable electrode arc welding according to claim 1 or 2.

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