Method for starting non-consumable electrode arc welding

Abstract

To provide a method for starting non-consumable electrode arc welding with use of a filler wire, in which a molten state of the filler wire is stabilized after welding start, and weld quality at the welding start part is improved.SOLUTION: In a method for starting non-consumable electrode arc welding that generates arc 3 between a non-consumable electrode 1 and a base material 2 to form a molten pool 2 and feeds a filler wire 6 to the molten pool 2 and welds the same, forward feeding of the filler wire 6 is started when arc 3 occurs, the filler wire 6 is reversely fed when the filler wire 6 is short-circuited with the molten pool 2 to form droplets by the arc 3, and is fed forward to short circuit-transfers the droplet to the molten pool 2. Forward feeding and reverse feeding of the filler wire 6 are repeated multiple times, and thereafter, the filler wire 6 is fed forward.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for starting non-consumable electrode arc welding in which an arc is generated between a non-consumable electrode and a base metal to form a molten pool, and a filler wire is fed into the molten pool for welding. [Background technology]

[0002] 2. Description of the Related Art A commonly used arc welding method involves generating an arc between a non-consumable electrode and a base metal to form a molten pool, and feeding a filler wire into the molten pool to perform welding.

[0003] In the invention of Patent Document 1, when welding is started, the feeding of the filler wire is started and when the filler wire comes into contact with the base metal, the feeding of the filler wire is stopped once, and after the tip of the filler wire melts in the arc forming part, the filler wire is fed into the arc forming part at the regular set filler wire feeding speed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 5-200555 Summary of the Invention [Problem to be solved by the invention]

[0005] At the start of welding, the molten state of the filler wire becomes unstable because the molten pool is not yet fully formed, which causes a problem of poor welding quality at the start of welding. Even if the feed of the filler wire is temporarily stopped as in the conventional technology, it is not possible to prevent the molten state of the filler wire from becoming unstable during the period when the molten pool is in a transitional state.

[0006] Therefore, an object of the present invention is to stabilize the molten state of the filler wire from the start of welding in a method for starting non-consumable electrode arc welding using a filler wire, thereby improving the weld quality at the start of welding. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the invention of claim 1 comprises: A method for starting non-consumable electrode arc welding in which an arc is generated between a non-consumable electrode and a base metal to form a molten pool, and a filler wire is fed into the molten pool for welding, comprising the steps of: When the arc is generated, the forward feed of the filler wire is started, When the filler wire is short-circuited with the molten pool, the filler wire is fed in a reverse direction to form a molten droplet by the arc, and then fed in a forward direction to transfer the molten droplet to the molten pool by short-circuiting; The reverse feeding and the forward feeding of the filler wire are repeated a plurality of times; Thereafter, the filler wire is fed forward. The present invention relates to a method for starting non-consumable electrode arc welding.

[0008] The invention of claim 2 is as follows: When a non-short circuit is formed between the filler wire and the molten pool, the feed is switched to the forward feed, and when a short circuit is formed between the filler wire and the molten pool, the feed is switched to the reverse feed. 2. The method for starting non-consumable electrode arc welding according to claim 1,

[0009] The invention of claim 3 is as follows: a short-circuit discrimination voltage is applied between the filler wire and the molten pool to discriminate between the non-short-circuit state and the short-circuit state; 3. A method for starting non-consumable electrode arc welding according to claim 2.

[0010] The invention of claim 4 is as follows: When a predetermined backward transport period has elapsed, switching to the forward transport is started, and when a predetermined forward transport period has elapsed, switching to the backward transport is started. 2. The method for starting non-consumable electrode arc welding according to claim 1, Effect of the Invention

[0011] According to the method for starting non-consumable electrode arc welding using a filler wire according to the present invention, the molten state of the filler wire can be stabilized from the start of welding, thereby improving the weld quality of the weld start portion. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram of a welding device for carrying out a method for starting non-consumable electrode arc welding according to an embodiment of the present invention. [Diagram 2] 2 is a timing chart of each signal in the welding device of FIG. 1, illustrating a method for starting non-consumable electrode arc welding according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0014] Fig. 1 is a block diagram of a welding device for carrying out a method for starting non-consumable electrode arc welding according to an embodiment of the present invention. In this figure, an arc 3 between a non-consumable electrode 1 and a base material 2 is a TIG arc. The arc 3 may be a plasma arc. Each block will be described below with reference to the figure.

[0015] The power supply main circuit PM receives an input of a commercial power supply (not shown) such as three-phase 200V, performs output control by inverter control in accordance with a drive signal Dv described below, and outputs a welding voltage Vw and welding current Iw for generating an arc 3. Although not shown, this power supply main circuit PM includes a primary rectifier circuit that rectifies the commercial power supply, a capacitor that smoothes the rectified DC, an inverter circuit that converts the smoothed DC into high-frequency AC in accordance with the drive signal Dv, a high-frequency transformer that steps down the high-frequency AC to an appropriate voltage value for generating the arc 3, a secondary rectifier circuit that rectifies the stepped-down high-frequency AC, and a reactor that smoothes the rectified DC.

[0016] The welding start circuit ON outputs a welding start signal On that goes to a High level when welding starts and to a Low level when welding ends. This welding start circuit ON is a torch switch attached to welding torch 4. When a welding robot (not shown) is used, the welding start signal On is output from a robot control device (not shown).

[0017] The short-circuit discrimination voltage application circuit VS is configured with a constant voltage source (not shown) and a resistor (not shown) connected in series, and is connected between the filler wire 6 and the base material 2. The value of this constant voltage source is the short-circuit discrimination voltage Vs. This short-circuit discrimination voltage Vs is set to a value at which no arc occurs even if the filler wire 6 is in a non-short-circuited state, and is set to about 1 to 8 V. For example, the short-circuit discrimination voltage Vs is set to 5 V and the resistor is set to 50 Ω. If the voltage between the filler wire 6 and the base material 2 is represented as the filler wire voltage Vf, when the filler wire 6 and the base material 2 are in a non-short-circuited state, the filler wire voltage Vf is 5 V, and when they are in a short-circuited state, Vf is 0 V. When they are in a short-circuited state, a current of 0.1 A flows through the filler wire 6.

[0018] An arc 3 is generated between a non-consumable electrode 1 attached to a welding torch 4 and a base material 2, a welding voltage Vw is applied, and a welding current Iw flows. A tungsten electrode is used for the non-consumable electrode 1. The non-consumable electrode 1 is the negative electrode and the base material 2 is the positive electrode, resulting in negative electrode polarity.

[0019] The filler wire 6 is fed through the liner 7 by the rotation of the feed roll 5 coupled to a feeder FM which receives a feed control signal Fc, which will be described later. A short-circuit discrimination voltage Vs is supplied to the filler wire 6 from the short-circuit discrimination voltage application circuit VS via a power feed tip (not shown). The filler wire 6 is melted by heat from the arc 3. In the figure, the filler wire 6 is fed to the arc 3 from the front in the welding direction. The filler wire 6 may also be fed to the arc 3 from the rear in the welding direction.

[0020] The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current setting circuit IR outputs a predetermined current setting signal Ir. The current error amplifier circuit EI receives the current setting signal Ir and the current detection signal Id, amplifies the error between the two signals, and outputs a current error amplification signal Ei.

[0021] The drive circuit DV receives the welding start signal On and the current error amplified signal Ei as inputs, and when the welding start signal On is at a high level, performs PWM modulation control based on the current error amplified signal Ei, and based on the result of that, outputs a drive signal Dv for driving the inverter circuit in the main power supply circuit PM, and does not output the drive signal Dv when the welding start signal On is at a low level.

[0022] The filler wire voltage detection circuit VFD detects the filler wire voltage Vf and outputs a filler wire voltage detection signal Vfd. The short circuit determination circuit SD receives the filler wire voltage detection signal Vfd and outputs a short circuit determination signal Sd that goes to low level when the filler wire voltage detection signal Vfd is less than a predetermined short circuit determination value (approximately 3 V) and determines that a short circuit exists, and goes to high level when the filler wire voltage detection signal Vfd is greater than or equal to a predetermined short circuit determination value and determines that a non-short circuit exists.

[0023] The forward transmission peak value setting circuit FSR outputs a predetermined forward transmission peak value setting signal Fsr, and the reverse transmission peak value setting circuit FRR outputs a predetermined reverse transmission peak value setting signal Frr.

[0024] The initial period feed speed setting circuit FIR receives the forward feed peak value setting signal Fsr, the reverse feed peak value setting signal Frr, and the short circuit determination signal Sd as inputs, selects either the forward / reverse feed control method 1) or 2) below, processes the method, and outputs an initial period feed speed setting signal Fir. 1) First forward and reverse feeding control method When the short circuit discrimination signal Sd changes to a low level (short circuit state), the value of the reverse feed peak value setting signal Frr is output as the initial period feed speed setting signal Fir, and when the short circuit discrimination signal Sd changes to a high level (non-short circuit state), the value of the forward feed peak value setting signal Fsr is output as the initial period feed speed setting signal Fir. 2) Second forward and reverse feeding control method During a predetermined reverse feed period, the value of the reverse feed peak value setting signal Frr is output as the initial period feed speed setting signal Fir, and during a predetermined forward feed period, the value of the forward feed peak value setting signal Fsr is output as the initial period feed speed setting signal Fir.

[0025] The steady-state period feed speed setting circuit FCR outputs a steady-state period feed speed setting signal Fcr, which is preset to a positive value. Since the steady-state period feed speed setting signal Fcr is a positive value, the filler wire 6 is fed forward at a predetermined speed.

[0026] The feed control circuit FC receives the current detection signal Id, the initial period feed speed setting signal Fir, and the steady period feed speed setting signal Fcr as inputs, performs the following processes 1) to 4), and outputs a feed control signal Fc to the feeder FM. 1) When a predetermined delay period Td has elapsed since the current detection signal Id started to pass current, a feed control signal Fc is output for feeding the filler wire 6 forward at a predetermined slow-down feed speed. 2) During a predetermined initial period from the point at which the short circuit discrimination signal Sd changes to a low level (short circuit), a feed control signal Fc is output to feed the filler wire 6 in the reverse and forward directions at a feed speed Fw corresponding to the value of the initial period feed speed setting signal Fir. 3) During the subsequent steady-state period, a feed control signal Fc is output for feeding the filler wire 6 in the forward direction at a feed speed Fw corresponding to the value of the steady-state-period feed speed setting signal Fcr. 4) When the current detection signal Id becomes non-conductive, a feed control signal Fc for stopping the feed is output.

[0027] Fig. 2 is a timing chart of each signal in Fig. 1 showing a method for starting non-consumable electrode arc welding according to an embodiment of the present invention. Fig. 2(A) shows the change over time of the welding current Iw passing through the arc, Fig. 2(B) shows the change over time of the filler wire feed speed Fw, Fig. 2(C) shows the change over time of the short-circuit detection signal Sd between the filler wire and the molten pool, and Fig. 2(D) shows the change over time of the welding start signal On. The operation of each signal at the start of welding will be described below with reference to this figure.

[0028] At time t1, as shown in Fig. 1(D), when the welding start signal On changes to a high level, the welding device is driven and a high frequency high voltage is applied between the non-consumable electrode and the base metal to generate an arc 3, and as shown in Fig. 1(A), the flow of the welding current Iw begins. The welding current Iw is controlled to be a constant current based on the value of the current setting signal Ir in Fig. 1. In Fig. 1, the welding current Iw is a constant value, but it may also be a pulse waveform.

[0029] Forward feed means that the filler wire is fed forward in the direction approaching the base material, and reverse feed means that the filler wire is fed backward in the direction away from the base material. When the feed speed Fw is in the forward feed state, it is displayed as a positive value, and when it is in the reverse feed state, it is displayed as a negative value.

[0030] At time t2, when the flow of the welding current Iw starts at time t1 and a predetermined delay period Td has elapsed, the feed speed Fw of the filler wire becomes a predetermined slow-down feed speed, and forward feed of the filler wire starts. As shown in FIG. 1C, the short circuit determination signal Sd is at a high level (non-shorted state). At time t3, when the filler wire is short-circuited with the molten pool, as shown in FIG. 1C, the short circuit determination signal Sd changes to a low level (shorted state), and a transition is made to a predetermined initial period from time t3 to t4. For example, the delay period Td is set to 100 ms, and the slow-down feed speed is set to 2 m / min.

[0031] (1) In the case of the first forward / reverse feed control method When the initial period starts at time t3, as shown in FIG. 1B, the feed speed Fw of the filler wire starts to switch to the reverse feed peak value. As a result, the feed speed Fw switches to a negative reverse feed peak value with a slope. The reverse feed peak value is set by the reverse feed peak value setting signal Frr in FIG. 1, and is, for example, -15 m / min.

[0032] When the reverse feed of the filler wire creates a non-short circuit between the filler wire and the molten pool, the short circuit discrimination signal Sd changes to a high level (non-short circuit state) as shown in FIG. 1C. In response to this, the filler wire feed speed Fw starts to switch to a positive forward feed peak value as shown in FIG. 1B. As a result, the feed speed Fw switches to the forward feed peak value with a slope. The forward feed peak value is set by the forward feed peak value setting signal Fsr in FIG. 1 and is, for example, 20 m / min. During this period, the filler wire is melted by the heat from the arc and a molten droplet is formed at the tip.

[0033] When the forward feed of the filler wire causes a short circuit between the filler wire and the base metal, the short circuit detection signal Sd changes to a low level (short circuit state) as shown in FIG. 1C. In response to this, the filler wire feed speed Fw starts to switch to the reverse feed peak value as shown in FIG. 1B. As a result, the feed speed Fw switches to a negative reverse feed peak value with a slope. During this period, the tip of the filler wire is short circuited with the molten pool, and the molten pool transfers to the molten pool.

[0034] The forward transmission and reverse transmission are repeated multiple times during the initial period. For example, the initial period is set to about 100 to 500 ms. Since the cycle of the forward transmission and reverse transmission is about 10 ms, the initial period includes 10 to 50 cycles of the forward transmission and reverse transmission.

[0035] (2) In the case of the second forward / reverse feed control method When the initial period starts at time t3, as shown in Fig. 1B, the feed speed Fw of the filler wire starts to switch to the reverse feed peak value, and as a result, the feed speed Fw switches to a negative reverse feed peak value with a slope.

[0036] When a predetermined reverse feed period has elapsed, as shown in FIG. 1B, the filler wire feed speed Fw starts to switch to a positive forward feed peak value. As a result, the feed speed Fw switches to a forward feed peak value with a slope. When the reverse feed of the filler wire results in a non-shorting state between the filler wire and the base metal, as shown in FIG. 1C, the short circuit determination signal Sd changes to a high level (non-shorting state). In the second forward / reverse feed control method, the timing at which the switch to forward feed starts and the timing at which the filler wire and the base metal result in a non-shorting state are not synchronized. During this period, the filler wire is melted by the heat from the arc, and a molten droplet is formed at the tip.

[0037] When the predetermined forward feed period has elapsed, as shown in FIG. 1B, the filler wire feed speed Fw starts to switch to a negative reverse feed peak value. As a result, the feed speed Fw switches to a reverse feed peak value with a slope. When the forward feed of the filler wire causes a short circuit between the filler wire and the base metal, as shown in FIG. 1C, the short circuit determination signal Sd changes to a low level (short circuit state). In the second forward / reverse feed control method, the timing at which the switch to reverse feed starts and the timing at which the filler wire and the base metal become short circuited are not synchronized. During this period, the tip of the filler wire is short circuited with the molten pool, and the droplets are transferred to the molten pool.

[0038] The above forward and reverse movements are repeated multiple times during the initial period.

[0039] When the initial period ends at time t4, as shown in FIG. 1(B), the filler wire feed speed Fw becomes the steady-state feed speed set by the steady-state feed speed setting signal Fcr in FIG. 1, and the filler wire is fed in the forward direction. For example, the steady-state feed speed is 3 m / min. A non-short circuit state is established between the filler wire and the molten pool, and the filler wire is stably melted by the arc. As shown in FIG. 1(C), the short circuit detection signal Sd becomes high level (non-short circuit state).

[0040] The effects of this embodiment will be described below. According to this embodiment, when an arc is generated, the forward feed of the filler wire is started, when the filler wire is short-circuited with the molten pool, the filler wire is fed in the reverse direction to form droplets by the arc, the filler wire is fed in the forward direction to short-circuit and transfer the droplets to the molten pool, the reverse and forward feed of the filler wire are repeated multiple times, and then the filler wire is fed in the forward direction. In this way, during the transition period at the start of welding, the formation of droplets and their transfer to the molten pool can be periodically repeated by repeating the reverse and forward feed of the filler wire. As a result, the molten state of the filler wire can be stabilized from the start of welding, and the welding quality at the start of welding can be improved.

[0041] More preferably, according to this embodiment, when a non-short circuit state is established between the filler wire and the molten pool, the feed is switched to the forward feed, and when a short circuit state is established, the feed is switched to the reverse feed. In this way, the formation of droplets in the non-short circuit state and the transfer of the droplets to the molten pool in the short circuit state can be performed periodically, so that the molten state of the filler wire can be stabilized.

[0042] More preferably, according to this embodiment, the non-short circuit state and the short circuit state are discriminated by applying a short circuit discrimination voltage between the filler wire and the molten pool. In this way, the non-short circuit state and the short circuit state can be discriminated accurately, so that the formation of droplets in the non-short circuit state and the transfer of the droplets to the molten pool in the short circuit state can be performed more periodically, and the molten state of the filler wire can be further stabilized.

[0043] More preferably, according to this embodiment, the switch to the forward feed starts when a predetermined reverse feed period has elapsed, and the switch to the reverse feed starts when a predetermined forward feed period has elapsed. In this way, by setting the cycle between the reverse feed period and the forward feed period, it is possible to set the cycle between the formation of droplets in a non-short circuit state and the transfer of the droplets to the molten pool in a short circuit state, and therefore the molten state of the filler wire can be stabilized. [Explanation of symbols]

[0044] 1 non-consumable electrode 2 Base material (molten pool) 3. Arc 4. Welding torch 5 Feeding roll 6 Filler Wire 7. Liner DV driver circuit Dv drive signal EI Current Error Amplifier Circuit Ei Current error amplification signal FC feed control circuit Fc feed control signal FM feeder FCR Steady period feeding speed setting circuit Fcr Steady-state feed speed setting signal FIR initial period feed speed setting circuit Fir Initial period feed speed setting signal FRR Reverse transmission peak value setting circuit Frr Reverse peak value setting signal FSR forward peak value setting circuit Fsr Positive transmission peak value setting signal Fw Feeding speed ID Current Detection Circuit Id Current detection signal IR current setting circuit Ir Current setting signal Iw Welding current ON Welding start circuit On Welding start signal PM power supply main circuit SD Short circuit detection circuit Sd Short circuit detection signal Vf Filler wire voltage VFD Filler Wire Voltage Detection Circuit Vfd Filler wire voltage detection signal VS short circuit detection voltage application circuit Vs Short circuit discrimination voltage Vw welding voltage

Claims

1. A method for starting non-consumable electrode arc welding in which an arc is generated between a non-consumable electrode and a base metal to form a molten pool, and a filler wire is fed into the molten pool for welding, comprising the steps of: When the arc is generated, the forward feed of the filler wire is started, When the filler wire is short-circuited with the molten pool, the filler wire is fed in a reverse direction to form a molten droplet by the arc, and then fed in a forward direction to transfer the molten droplet to the molten pool by short-circuiting; The reverse feeding and the forward feeding of the filler wire are repeated a plurality of times; Thereafter, the filler wire is fed forward.

2. A method for starting non-consumable electrode arc welding.

2. When a non-short circuit is formed between the filler wire and the molten pool, the feed is switched to the forward feed, and when a short circuit is formed between the filler wire and the molten pool, the feed is switched to the reverse feed.

2. The method for starting non-consumable electrode arc welding according to claim 1.

3. a short-circuit discrimination voltage is applied between the filler wire and the molten pool to discriminate between the non-short-circuit state and the short-circuit state; 3. The method for starting non-consumable electrode arc welding according to claim 2.

4. When a predetermined backward transport period has elapsed, switching to the forward transport is started, and when a predetermined forward transport period has elapsed, switching to the backward transport is started.

2. The method for starting non-consumable electrode arc welding according to claim 1.

Images