Methods to deal with magnetic blow during pulsed arc welding

Abstract

To suppress deformation of an arc caused by a magnetic blow in consumable electrode pulse arc welding.SOLUTION: A method of addressing a magnetic blow in pulse arc welding repeats a peak period Tp in which a welding wire is supplied and a peak current Ip and a peak voltage are output at an electrode positive polarity EP, and a base period Tb in which a base current Ib and a base voltage are output. When occurrence of a magnetic blow is determined on the basis of a rise in the base voltage, the method controls output of a welding power supply to address the magnetic blow. When a magnetic blow is determined Dab at time t42, the output is switched from the electrode positive polarity EP to an electrode negative polarity EN, and at times t42 to t44 during the electrode negative polarity, an electrode negative polarity current In is applied. When disappearance of the magnetic blow is determined on the basis of reduction in the base voltage Vw at time 44, the output is returned to the electrode positive polarity EP.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for dealing with magnetic blow in consumable electrode pulsed arc welding. [[ID=…]]

Background Art

[0002] In consumable electrode pulsed arc welding, welding is repeatedly performed by feeding a welding wire and repeating a peak period for outputting a peak current and a peak voltage with electrode positive polarity and a base period for outputting a base current and a base voltage. The peak current is set to a large current value of about 500 A to melt the welding wire to form and transfer droplets. The base current is set to about 30 A, and the welding wire hardly melts. In pulsed arc welding, it is important to maintain a state of one-droplet transfer per pulse in which one droplet is transferred by one energization of the peak current in order to obtain a high-quality weld bead with less spatter generation.

[0003] In pulsed arc welding of steel or the like, a magnetic field is often formed around the arc generation part by the welding current passing through the base material, and the arc is often deformed by the force received from this magnetic field. Such a state is generally called magnetic blow or arc blow. When the occurrence state of magnetic blow becomes severe, the arc is greatly deformed, the arc length becomes very long, and the arc cannot be maintained, resulting in arc interruption. When arc interruption occurs, the welding quality deteriorates. Therefore, in pulsed arc welding, countermeasures against magnetic blow are a major issue.

[0004] In the invention described in Patent Document 1, when the rate of increase of the base voltage during the base period is detected to be greater than or equal to a reference rate of increase, it is determined that magnetic blow has occurred, and magnetic blow countermeasure control is performed by rapidly increasing the base current to 200A or more. Magnetic blow occurs during the base period when the rigidity of the arc is weak due to the small current value. The occurrence of magnetic blow is determined by utilizing the fact that the arc voltage (base voltage) increases when the arc length is increased due to magnetic blow. Furthermore, increasing the base current strengthens the rigidity of the arc, and the deformation of the arc can be suppressed even when subjected to force from the magnetic field. As a result, arc breakup can be prevented. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2004-268081 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In cases where arc deformation due to magnetic blowing is severe, increasing the base current, as in conventional techniques, may not suppress the arc deformation.

[0007] Therefore, the present invention aims to provide a method for dealing with magnetic blow in pulsed arc welding that can eliminate magnetic blow and suppress arc deformation, even when the deformation of the arc due to magnetic blow is strong. [Means for solving the problem]

[0008] To solve the above-mentioned problems, the invention of claim 1 repeatedly feeds a welding wire and outputs a peak current and peak voltage with positive electrode polarity during a peak period and a base current and base voltage during a base period, In a pulsed arc welding method for dealing with magnetic blow, where the occurrence of magnetic blow is determined based on the rise in the base voltage, the output of the welding power supply is controlled to deal with the magnetic blow. When the magnetic blow is detected, the output is switched from the positive polarity of the electrode to the negative polarity of the electrode, and while the electrode is in the negative polarity state, the negative polarity current is Power is turned on, The negative polarity current of the electrode is set to a value greater than or equal to a value that does not cause a short circuit between the welding wire and the base material, and less than a value that does not cause droplet formation. This is a method for dealing with magnetic blow during pulsed arc welding, characterized by the following features.

[0009] The invention of claim 2 is, When it is determined that magnetic blow has been eliminated based on the decrease in the base voltage, the electrode is returned to positive polarity. The method for dealing with magnetic blow in pulsed arc welding as described in feature 1. [Effects of the Invention]

[0011] According to the present invention, even when the arc deformation due to magnetic blow is strong, the magnetic blow can be eliminated and the arc deformation can be suppressed, thus enabling high-quality welding. [Brief explanation of the drawing]

[0012] [Figure 1] This is a block diagram of a welding power supply for implementing a method to deal with magnetic blowing in pulsed arc welding according to an embodiment of the present invention. [Figure 2] Figure 1 shows a timing chart of each signal in the welding power supply illustrating a method for dealing with magnetic blow during pulsed arc welding according to an embodiment of the present invention. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings.

[0014] Figure 1 is a block diagram of a welding power source for implementing a method to address magnetic blow during pulsed arc welding according to an embodiment of the present invention. Each block will be described below with reference to this figure.

[0015] The main power supply circuit MC takes a commercial power supply such as 3-phase 200V (not shown) as input and controls the output by inverter control etc. according to the current error amplification signal Ei described later, and switches between the electrode positive polarity EP and the electrode negative polarity EN by the polarity switching signal Dr described later, and outputs a welding voltage Vw and welding current Iw between the welding wire 1 and the base material 2. This main power supply circuit MC, although not shown, includes a primary rectifier for rectifying the commercial power supply, a smoothing capacitor for smoothing the rectified DC, an inverter circuit driven by the current error amplification signal Ei that converts the smoothed DC to a high-frequency AC, a high-frequency transformer for stepping down the high-frequency AC to a voltage value suitable for welding, a secondary rectifier for rectifying the stepped-down high-frequency AC to DC, a reactor for smoothing the rectified DC, and a secondary inverter circuit that switches the polarity of the smoothed DC based on the polarity switching signal Dr.

[0016] The welding wire 1 is fed through the welding torch 4 by the rotation of a feed roll 5 coupled to a wire feed motor (not shown), and an arc 3 is generated between it and the base material 2. A welding voltage Vw is applied and a welding current Iw flows between the power supply tip (not shown) inside the welding torch 4 and the base material 2. The circuit for controlling the feeding of the welding wire 1 is omitted.

[0017] The voltage detection circuit VD detects the absolute value of the welding voltage Vw and outputs a voltage detection signal Vd. The voltage averaging circuit VAV averages the voltage detection signal Vd and outputs a voltage average signal Vav. The voltage setting circuit VR outputs a predetermined voltage setting signal Vr.

[0018] The voltage error amplification circuit EV amplifies the error between the above-mentioned voltage setting signal Vr and the above-mentioned voltage average signal Vav, and outputs the voltage error amplification signal Ev. The V / F converter VF outputs a pulse frequency signal Tf having a frequency corresponding to the above-mentioned voltage error amplification signal Ev. This pulse frequency signal Tf is a signal that determines the frequency with a peak period and a base period equal to one period.

[0019] The peak period timer circuit TTP outputs a peak period signal Ttp that becomes High level for a peak period Tp determined in advance for each frequency of the above pulse frequency signal Tf. Therefore, this peak period signal Ttp is a signal that becomes High level during the peak period Tp and Low level during the base period.

[0020] The arc discrimination circuit AD takes the above voltage detection signal Vd as an input, discriminates whether an arc is generated based on this value, and outputs an arc discrimination signal Ad that becomes High level.

[0021] The magnetic blow discrimination circuit DAB takes the above peak period signal Ttp, the above arc discrimination signal Ad, and the above voltage detection signal Vd as inputs. When the peak period signal Ttp is at Low level (base period Tb) and the arc discrimination signal Ad is at High level (arc generation state), based on the voltage detection signal Vd (base voltage) at this time, when the generation of magnetic blow is discriminated by the following method 1) or 2), it becomes High level, and then when the elimination of magnetic blow is discriminated, it outputs a magnetic blow discrimination signal Dab that returns to Low level. 1) When the rising rate of the voltage detection signal Vd becomes equal to or higher than the reference value, it is discriminated that magnetic blow has occurred and becomes High level. Then, when the falling rate (absolute value) of the voltage detection signal Vd becomes equal to or lower than the reference value, it is discriminated that magnetic blow has disappeared and becomes Low level, and a magnetic blow discrimination signal Dab is output. 2) When the rising rate of the voltage detection signal Vd becomes equal to or higher than the reference value, it is discriminated that magnetic blow has occurred and becomes High level. Then, when the peak period signal Ttp becomes High level, it is discriminated that magnetic blow has disappeared and becomes Low level, and a magnetic blow discrimination signal Dab is output.

[0022] The peak current setting circuit IPR outputs a predetermined peak current setting signal Ipr. The peak current setting signal Ipr is set to about 400 to 600 A according to the diameter, material, feeding speed, etc. of the welding wire.

[0023] The base current setting circuit IBR outputs a predetermined base current setting signal Ibr. The setting range for the base current setting signal Ibr is approximately 20 to 50A.

[0024] The electrode negative polarity current setting circuit INR outputs a predetermined electrode negative polarity current setting signal Inr. The electrode negative polarity current setting signal Inr is set to a value that prevents a short circuit between the welding wire 1 and the base material 2 during electrode negative polarity EN. For example, it is set to approximately 40 to 70A.

[0025] The current setting circuit IR takes the above-mentioned peak current setting signal Ipr, base current setting signal Ibr, electrode negative polarity current setting signal Inr, peak period signal Ttp, and magnetic blow discrimination signal Dab as inputs, performs the following processing, and outputs the current setting signal Ir. 1) When the peak period signal Ttp is at a high level, the peak current setting signal Ipr is output as the current setting signal Ir. 2) When the peak period signal Ttp is at a low level and the magnetic blow discrimination signal Dab is at a low level, the base current setting signal Ibr is output as the current setting signal Ir. 3) When the peak period signal Ttp is at a low level and the magnetic blow discrimination signal Dab is at a high level, the electrode negative polarity current setting signal Inr is output as the current setting signal Ir.

[0026] The current detection circuit ID detects the absolute value of the welding current Iw and outputs a current detection signal Id. The current error amplification circuit EI amplifies the error between the current setting signal Ir and the current detection signal Id and outputs a current error amplification signal Ei.

[0027] The polarity switching circuit DR takes the magnetic blow detection signal Dab as input and outputs a polarity switching signal Dr that becomes low level (electrode positive polarity EP) when the magnetic blow detection signal Dab is low level, and high level (electrode negative polarity EN) when the magnetic blow detection signal Dab is high level. Therefore, the electrode is positive polarity EP during the peak period and the base period when magnetic blow is not occurring, and negative polarity EN when magnetic blow is occurring.

[0028] Figure 2 is a timing chart of each signal in the welding power supply of Figure 1, illustrating a method for dealing with magnetic blow in pulsed arc welding according to an embodiment of the present invention. Figure (A) shows the time variation of the welding current Iw, Figure (B) shows the time variation of the welding voltage Vw, Figure (C) shows the time variation of the magnetic blow detection signal Dab, and Figure (D) shows the time variation of the polarity switching signal Dr. The operation of each signal will be explained below with reference to the figure.

[0029] The figure shows waveforms for two periods. The first period represents the case where no magnetic blow occurs. The second period represents the case where magnetic blow occurs during the base period Tb. In the figure, the welding current Iw shown in (A) and the welding voltage Vw shown in (B) indicate electrode positive polarity EP above 0 and electrode negative polarity EN below 0.

[0030] (1) Explanation of the operation of the first cycle During the first cycle from time t1 to t3, no magnetic blow occurs, so as shown in Figure (C), the magnetic blow detection signal Dab remains at a low level, and as shown in Figure (D), the polarity switching signal Dr is at a low level, and the output of the welding power supply is electrode positive polarity EP. During the predetermined peak period Tp from time t1 to t2, as shown in Figure (A), a predetermined peak current Ip is supplied with electrode positive polarity EP, and as shown in Figure (B), a peak voltage proportional to the arc length is applied. The peak current Ip is set by the peak current setting signal Ipr in Figure 1. During the peak period Tp, the tip of the welding wire is melted and a droplet is formed, and at the initial timing of Ib after the end of the peak period Tp, the droplet moves into the molten pool (1 pulse, 1 droplet transition state). The peak period Tp and peak current Ip are set to achieve this 1 pulse, 1 droplet transition state.

[0031] The period from time t2 to t3 is the base period Tb. Time t1 to t3 is one pulse period. The pulse period (pulse frequency) is feedback controlled (frequency modulation control) so that the average value of the welding voltage Vw is equal to the value of the voltage setting signal Vr. This maintains the average arc length at an appropriate value.

[0032] During the base period Tb, no magnetic blow occurs, so as shown in Figure (A), a predetermined base current Ib is supplied by the positive polarity electrode EP, and as shown in Figure (B), a base voltage Vb that is approximately constant is applied. The base current Ib is set by the base current setting signal Ibr in Figure 1.

[0033] (2) Explanation of the operation of the second cycle The behavior of the peak period Tp from time t3 to t4 is the same as that of time t1 to t2. Furthermore, the behavior of the base period from time t4 to t41 is the same as that of time t2 to t3.

[0034] At time t41, magnetic blow occurs, causing the arc to deform and the arc length to gradually increase beyond the normal state. As a result, as shown in Figure (B), the base voltage Vb rises from time t41, and at time t42, the rate of increase exceeds the reference value, causing the magnetic blow detection signal Dab to reach a high level, as shown in Figure (C). In response, as shown in Figure (D), the polarity switching signal Dr changes to a high level, and the output of the welding power supply switches from electrode positive polarity EP to electrode negative polarity EN. As a result, as shown in Figure (A), the welding current Iw switches from a positive base current Ib to a predetermined negative electrode negative polarity current In. The electrode negative polarity current In is set by the electrode negative polarity current setting signal Inr in Figure 1. As shown in Figure (B), the welding voltage Vw switches from a positive base voltage value to a negative electrode negative polarity voltage. The absolute value of the welding voltage Vw continues to rise for a short time from time t42, and then decreases from time t43. At time t44, because the rate of decrease falls below the reference value, the magnetic blow detection signal Dab becomes low level, as shown in Figure (C), as it is determined that the magnetic blow has been eliminated. In response to this, the polarity switching signal Dr changes to a low level, as shown in Figure (D), so the output of the welding power supply returns to the electrode positive polarity EP from t44 to t45. The period from time t45 to t5 becomes the base period, and the operation from time t4 to t41 is performed. The determination of the elimination of magnetic blow can also be made at the start of the next peak period after time t5. This is because when a peak current of a large current value is applied, the rigidity of the arc increases and the magnetic blow is eliminated.

[0035] The effects and advantages of this embodiment will be described below. According to this embodiment, when magnetic blow is detected, the output is switched from positive electrode polarity to negative electrode polarity, and a negative electrode polarity current is supplied while the electrode is negative. When magnetic blow occurs and the arc is deformed by a force from the magnetic field, switching the polarity and reversing the direction of the welding current supply reverses the direction of the force acting on the arc. As a result, the deformation of the arc is reset, and the magnetic blow is eliminated. Consequently, in this embodiment, even when the arc deformation due to magnetic blow is strong, the magnetic blow can be eliminated and the arc deformation can be suppressed.

[0036] More preferably, according to this embodiment, when the elimination of magnetic blow is determined based on the decrease in base voltage, the electrode polarity is returned to positive. In this way, the electrode polarity can be negative only for a short period of time until the magnetic blow is eliminated, thus minimizing the impact on the bead appearance, penetration, etc.

[0037] More preferably, according to this embodiment, the negative electrode current is set to a value that does not cause a short circuit between the welding wire and the base material. In this way, the instability of the welding state caused by the occurrence of a short circuit can be suppressed. If the negative electrode current is too large, droplets will form and the welding state will become unstable, so it is set to a value that is about 20 to 50 A larger than the base current. That is, it is desirable that the negative electrode current be set to a value that is greater than or equal to the value that does not cause a short circuit, and less than the value that does not cause droplet formation. [Explanation of symbols]

[0038] 1. Welding wire 2 Base material 3 Arc 4. Welding torch 5 Feeding Roll AD Arc Discrimination Circuit Ad Arc Discrimination Signal DAB Magnetic Blowing Discrimination Circuit DAB magnetic blow discrimination signal DR polarity switching circuit Dr polarity switching signal EI Current Error Amplifier Circuit Ei Current Error Amplification Signal EV voltage error amplification circuit Ev Voltage Error Amplification Signal Ib Base current IBR Base Current Setting Circuit Ibr Base current setting signal ID Current Detection Circuit Id Current detection signal In Electrode Negative Polarity Current INR electrode negative polarity current setting circuit Inr electrode negative polarity current setting signal Ip Peak Current IPR Peak Current Setting Circuit IPR Peak Current Setting Signal IR current setting circuit Ir current setting signal Iw welding current MC power supply main circuit Tb base period Tf pulse frequency signal Tp peak period TTP Peak Period Timer Circuit TTP Peak Period Signal VAV Voltage Averaging Circuit Vav voltage averaged signal Vb Base voltage VD Voltage Detection Circuit Vd voltage detection signal VF V / F Converter VR voltage setting circuit Vr voltage setting signal Vw welding voltage

Claims

1. The welding wire is fed, and the system repeatedly outputs a peak current and peak voltage with the electrode in positive polarity during the peak period, and a base current and base voltage during the base period. In a pulsed arc welding method for dealing with magnetic blow, where the occurrence of magnetic blow is determined based on the rise in the base voltage, the output of the welding power supply is controlled to deal with the magnetic blow. When the magnetic blow is detected, the output is switched from the positive polarity of the electrode to the negative polarity of the electrode, and while the electrode is in the negative polarity state, a negative polarity current is passed through it. The negative polarity current of the electrode is set to a value greater than or equal to a value that does not cause a short circuit between the welding wire and the base material, and less than a value that does not cause droplet formation. A method for dealing with magnetic blowing in pulsed arc welding, characterized by the features described herein.

2. When it is determined that magnetic blow has been eliminated based on the decrease in the base voltage, the electrode is returned to positive polarity. The method for dealing with magnetic blowing in pulsed arc welding as described in feature 1.

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