JP2015037799A - Arc starting control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain good arc starting performance even if the temperature of a base material and welding dead time vary.SOLUTION: Welding is started by applying a hot-start current Ih for a hot-start period Th. The temperature of a base material at the welding start time is measured, and the welding dead time from the former welding finishing to this time welding starting is measured. Comparing the hot-start current Ih calculated on the basis of the welding dead time with the hot-start current Ih calculated on the basis of the temperature measurement value of the base material, the smaller value is set as the hot-start current Ih in this time welding starting. Comparing the hot-start period Th calculated on the basis of the welding dead time with the hot-start period Th calculated on the basis of the temperature measurement value of the base material, the smaller value is set as the hot-start period Th in this time welding starting. Thus, good arc starting performance is always obtained even if the temperature of the base material and the welding dead time vary.

Description

  The present invention relates to an arc start control method for starting welding by energizing a predetermined hot start current during a predetermined hot start period when a welding current is energized.

  At the start of consumable electrode arc welding and non-consumable electrode arc welding, if a welding current is energized (the arc is ignited), a predetermined hot start current is energized for a predetermined hot start period to start welding. Conventional arc start control methods have been used. The value of this hot start current is set to a value larger than the value of the steady welding current. Thereby, a favorable arc start property can be obtained by rapidly applying heat to the electrode and the base material.

  If the values of the above hot start current and hot start period are larger than the appropriate values, the heat input becomes excessive, and in consumable electrode arc welding, the arc length becomes too long and the state shifts to a steady welding state. It takes time. On the other hand, in non-consumable electrode arc welding, there is a problem in that electrode wear increases. On the other hand, if the values of the hot start current and the hot start period are smaller than the appropriate values, there is a problem that heat input is insufficient, arc breakage occurs, and the state does not smoothly shift to the steady welding state. Therefore, the hot start current and the hot start period are set by experiments so as to be appropriate values according to the welding method, the type of electrode, the welding current average value, and the like.

  When the welding pause time from the previous welding end time to the current welding start time is short, the electrode temperature at the current welding start time becomes high. When the welding pause time is long, the electrode temperature is low. The appropriate values of the hot start current and the hot start period vary depending on the electrode temperature at the start of welding. For this reason, in the invention of Patent Document 1, the welding pause time is measured, and the value of the hot start current and / or the hot start period is changed according to the welding pause time. As a result, even if the welding pause time changes and the electrode temperature changes, the hot start current and the hot start period are automatically adjusted so as to have appropriate values, so that a good arc start property can always be obtained. it can.

JP-A-62-9773

  In the case where there are a plurality of welding locations in one work (base material), the base material temperature becomes higher as the welding of the plurality of welding locations proceeds. In the prior art, the values of the hot start current and the hot start period are constant values regardless of the base material temperature. Therefore, when the base material temperature increases, the heat input becomes excessive, and the arc start performance is deteriorated as described above. There is a fear.

  Therefore, an object of the present invention is to provide an arc start control method capable of obtaining good arc start performance even when the base metal temperature at the start of welding changes.

In order to solve the above-described problems, the invention of claim 1
In the arc start control method of starting welding by energizing a predetermined hot start current during a predetermined hot start period when the welding current is energized,
Measure the temperature of the base material at the start of welding, calculate and set the hot start current and the hot start period based on this base material temperature measurement value,
An arc start control method characterized by the above.

The invention of claim 2 measures the welding pause time from the end of the previous welding to the current welding start time, calculates the hot start current and the hot start period based on the welding pause time,
Comparing the hot start current calculated based on the welding pause time and the hot start current calculated based on the measured base material temperature, the smaller value is the hot start current at the start of the current welding. Set as
Comparing the hot start period calculated based on the welding pause time and the hot start period calculated based on the measured base material temperature, the smaller value is the hot start period at the start of welding this time. Set as
The arc start control method according to claim 1, wherein:

  According to the present invention, good arc start performance can be obtained even if the base metal temperature at the start of welding changes.

It is a block diagram of the welding power supply for enforcing the arc start control method concerning Embodiment 1 of the present invention. In Embodiment 1 of this invention, it is an example of the relationship figure of the base material temperature measurement signal Bd (degreeC) at the time of a welding start, hot start electric current Ih (A), and hot start period Th (ms). It is a timing chart of each signal in the welding power supply mentioned above in FIG. It is a block diagram of the welding power supply for implementing the arc start control method which concerns on Embodiment 2 of this invention. In Embodiment 2 of this invention, it is an example of the related figure of welding stop time signal Td (sec), hot start electric current Ih (A), and hot start period Th (ms).

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

[Embodiment 1]
In the first embodiment, the case where the welding method is carbon dioxide arc welding which is one of consumable electrode arc welding will be described.

  FIG. 1 is a block diagram of a welding power source for carrying out an arc start control method according to Embodiment 1 of the present invention. Hereinafter, each block will be described with reference to FIG.

  The power supply main circuit PM receives a commercial power supply (not shown) such as three-phase 200 V, performs output control such as inverter control in accordance with a drive signal Dv described later, and generates a welding voltage Vw and a welding current for generating the arc 3. Iw is output. Although not shown, the power main circuit PM has a primary rectifier that rectifies commercial power, a capacitor that smoothes the rectified direct current, an inverter circuit that converts the smoothed direct current into high-frequency alternating current according to the drive signal Dv, A high-frequency transformer that steps down the alternating current to a voltage value suitable for arc welding, a secondary rectifier that rectifies the stepped-down high-frequency alternating current, and a reactor that smoothes the rectified direct current.

  The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeding motor WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding current Iw is passed through the arc 3, and a welding voltage Vw is applied between the power feed tip (not shown) in the welding torch 4 and the base material 2.

  The voltage detection circuit VD detects the welding voltage Vw and outputs a voltage detection signal Vd. The current detection circuit ID detects the welding current Iw and outputs a current detection signal Id. The current energization determination circuit CD receives the current detection signal Id and, when this value is equal to or greater than a predetermined current determination value, determines that the welding current Iw is energized and becomes a high level current energization determination signal. Cd is output. This current discrimination value is set to about 10 A, for example.

  The temperature sensor BD is attached to the welding torch 4, measures the temperature of the base material 2, and outputs a base material temperature measurement signal Bd. A non-contact type radiation thermometer is used for the temperature sensor BD. Further, even if the temperature of the base material 2 is indirectly measured by using a contact-type thermometer for the temperature sensor BD and measuring the temperature of a jig (not shown) on which the base material 2 is installed. good.

  The interface circuit IF receives the welding condition signal Wc from the robot controller RC and outputs a welding start signal St, a steady welding voltage setting signal Vr, and a steady feeding speed setting signal Fr included in this signal. The start-up circuit ON receives this welding start signal St and outputs an start-up signal On with an off-delay for a predetermined anti-stick control period, and at the same time, an anti-stick control period signal that is at a high level during the anti-stick control period. Ta is output.

  The hot start current setting circuit IHR receives the welding start signal St and the base material temperature measurement signal Bd as input, and the base material temperature measurement signal Bd when the welding start signal St changes to a high level (welding start). The value is input to a predetermined hot start current calculation function which will be described later with reference to FIG. 2 to calculate and output a hot start current setting signal Ihr. The current error amplification circuit EI amplifies an error between the hot start current setting signal Ihr and the current detection signal Id, and outputs a current error amplification signal Ei.

  The anti-stick voltage setting circuit VAR outputs a predetermined anti-stick voltage setting signal Var. The voltage control setting circuit VCR receives the above-mentioned steady welding voltage setting signal Vr, the anti-stick voltage setting signal Var and the anti-stick control period signal Ta, and the anti-stick control period signal Ta is at a low level (steady welding period). In this case, the steady welding voltage setting signal Vr is output as the voltage control setting signal Vcr, and when the level is High, the anti-stick voltage setting signal Var is output as the voltage control setting signal Vcr. The voltage error amplification circuit EV amplifies an error between the voltage control setting signal Vcr and the voltage detection signal Vd, and outputs a voltage error amplification signal Ev.

  The hot start period setting circuit THR receives the welding start signal St and the base material temperature measurement signal Bd, and receives the base material temperature measurement signal Bd when the welding start signal St changes to a high level (welding start). The value is input to a predetermined hot start period calculation function which will be described later with reference to FIG. 2 to calculate and output a hot start period setting signal Thr. The hot start period timer circuit TH receives the hot start period setting signal Thr and the current energization determination signal Cd, and receives only the period determined by the hot start period setting signal Thr from the time when the current energization determination signal Cd changes to High level. A hot start period signal Th that becomes a high level is output.

  The external characteristic switching circuit SW receives the current error amplification signal Ei, the voltage error amplification signal Ev, and the hot start period signal Th, and when the hot start period signal Th is at a high level, the current error amplification signal Ei. Is output as the error amplification signal Ea, and when it is at the Low level, the voltage error amplification signal Ev is output as the error amplification signal Ea. The drive circuit DV receives the error amplification signal Ea and the activation signal On, and when the activation signal On is at a high level, performs a pulse width modulation control based on the error amplification signal Ea and outputs the drive signal Dv. . As a result, when the welding start signal St becomes high level, the constant voltage characteristic is obtained and the output of the welding voltage Vw is started. When the welding current Iw starts energization, constant current characteristics are obtained, and the hot start current Ih is energized during the hot start period Th. When this period ends, the constant voltage characteristic is obtained, and the welding voltage Vw becomes a value determined by the steady welding voltage setting signal Vr. When the welding start signal St changes to the Low level, the welding voltage Vw becomes a value determined by the antistick voltage setting signal Var from this time point to the antistick control period.

  The feed rate control setting circuit FCR receives the welding start signal St, the current energization determination signal Cd, and the steady feed rate setting signal Fr as inputs, and when the welding start signal St becomes a high level, a predetermined slow speed is set. The feed speed control setting signal Fcr becomes a value determined by the steady feed speed setting signal Fr when the current energization determination signal Cd becomes High level and becomes 0 when the welding start signal St becomes Low level. Output.

  The feed control circuit FC receives the feed speed control setting signal Fcr as an input, and feeds a feed control signal Fc for feeding the welding wire 1 at a feed speed corresponding to this value to the feed motor WM. Output.

  FIG. 2 is an example of a relationship diagram between the base material temperature measurement signal Bd (° C.), the hot start current Ih (A), and the hot start period Th (ms) at the start of welding. The horizontal axis indicates the base material temperature measurement signal Bd, which is in the range of 0 to 250 ° C. The left vertical axis indicates the hot start period Th, which ranges from 0 to 10 ms. The right vertical axis indicates the hot start current Ih, which is in the range of 300 to 600A. In the figure, the base material is steel, the welding wire is steel, the diameter is 1.2 mm, and the welding method is carbon dioxide arc welding.

  The hot start current Ih indicated by the solid line is 500 A in the range of Bd ≦ 20 ° C., Ih decreases as Bd increases, and becomes 400 A in the range of Bd ≧ 220 ° C. The hot start period Th indicated by the broken line is 5 ms in the range of Bd ≦ 20 ° C., Th decreases as Bd increases, and 1 ms in the range of Bd ≧ 220 ° C.

  The characteristic of the solid line in the figure is a hot start current calculation function built in the hot start current setting circuit IHR in FIG. In addition, the characteristics indicated by the broken line in FIG. 4 are a hot start period calculation function built in the hot start period setting circuit THR in FIG. These functions are set so as to have appropriate characteristics by experiments for each welding condition such as the material of the base material, the material of the welding wire, the diameter, and the welding method.

  1 and 2 described above are cases where the hot start current Ih and the hot start period Th, which are parameters at the time of arc start, are changed in accordance with the base material temperature measurement signal Bd, but at least one of the two parameters is used. May be changed. For example, in order not to change the hot start period Th even if the base material temperature measurement signal Bd changes, the hot start period calculation function indicated by the broken line in FIG. 2 is not dependent on the value of the base material temperature measurement signal Bd. What is necessary is just to make it a fixed value. This constant value is set to a value when Bd ≦ 20 ° C. That is, it is set to a value when the base material is in a cold state.

  FIG. 3 is a timing chart of each signal in the welding power source described above with reference to FIG. FIG. 4A shows the time change of the welding start signal St, FIG. 4B shows the time change of the welding wire feed speed Fw, FIG. 3C shows the time change of the welding current Iw, FIG. 4D shows the change over time of the welding voltage Vw. Hereinafter, the operation will be described with reference to FIG.

[When welding starts (when arc starts)]
When the welding torch reaches the welding start position by the movement of the robot, a high level welding start signal St is output to the welding power source from the robot controller RC at time t1, as shown in FIG. The hot start current setting circuit IHR in FIG. 1 inputs the value of the base material temperature measurement signal Bd at the time when the welding start signal St changes to the high level to the hot start current calculation function described above with reference to FIG. A start current setting signal Ihr is output. At the same time, the hot start period setting circuit THR in FIG. 1 inputs the value of the base material temperature measurement signal Bd at the time when the welding start signal St changes to the high level to the hot start period calculation function described above with reference to FIG. The hot start period setting signal Thr is output. Thus, an appropriate hot start current Ih and hot start period Th are automatically set according to the base material temperature at the start of welding.

At time t1, when the welding start signal St becomes a high level (welding start) as shown in FIG. 9A, the welding wire is set to a predetermined slow of about 1 m / min as shown in FIG. Feeding at the slow-down feeding speed Fi is started. At the same time, since the output of the welding power source is also started, as shown in FIG. 4D, the welding voltage Vw that is the maximum no-load voltage value is applied between the welding wire and the base material. In this state, since the welding wire and the base material are separated from each other and are in a no-load state, the welding current Iw is not energized as shown in FIG.

  At time t2, when the tip of the welding wire comes into contact with the base material by the slow-down feeding, the welding current Iw starts energization and the arc is ignited as shown in FIG. When energization of the welding current Iw is started, the hot start current Ih set to an appropriate value according to the base material temperature is changed to a hot start period Th (time t2 to t3) set to an appropriate value according to the base material temperature. ) Energize inside. At time t2, the welding voltage Vw becomes a hot start voltage value smaller than the no-load voltage value as shown in FIG. When the welding current Iw is energized at time t2, as shown in FIG. 5B, the feeding speed Fw is accelerated with an inclination and converges to a value determined by the steady feeding speed setting signal Fr at time t4.

  The reason why the hot start current Ih is energized is that when the tip of the welding wire comes into contact with the base material, the hot start current Ih having a large current value is energized to rapidly melt the tip of the welding wire and instantly start an arc. This is to make it arc. Furthermore, it is to smoothly shift from the instantaneous arc generation state to the steady arc generation state by initially applying appropriate heat input.

[Normal welding period]
The period from time t4 to t5 is the steady welding period. During this period, as shown in FIG. 5B, the feeding speed Fw becomes a value determined by the steady feeding speed setting signal Fr. During the short-circuit period from time t41 to t42, the welding current Iw gradually increases as shown in FIG. 8C, and the welding voltage Vw becomes a short-circuit voltage value of several volts as shown in FIG. . During the arc period from the time t42 to t43, the welding current Iw gradually decreases as shown in FIG. 10C, and the welding voltage Vw has an arc voltage value of several tens of volts as shown in FIG. Become. In the figure, three short-circuit periods and arc periods are drawn during the steady welding period from time t4 to t5. Actually, the short circuit occurs about 30 to 100 times per second. The average value of the welding current Iw during the steady welding period becomes the steady welding current value, and is set by the steady feeding speed setting signal Fr. Moreover, the average value of the welding voltage Vw during the steady welding period becomes the steady welding voltage value, and is set by the steady welding voltage setting signal Vr.

[At the end of welding (anti-stick control period)]
At time t5, when the welding start signal St becomes low level (end of welding) as shown in FIG. 11A, the feed motor is controlled to stop as shown in FIG. The speed Fw gradually decelerates due to inertia and stops at time t6. At the same time, the output from the welding power source PS is continued during a predetermined anti-stick control period Ta at times t5 to t8. During this anti-stick control period Ta, two short-circuits occur during the period from time t51 to t52 and from time t53 to t54. Actually, a short circuit occurs about 3 to 8 times. The short circuit from time t53 to t54 is the final short circuit. As shown in FIG. 6D, the welding voltage Vw becomes a short-circuit voltage value during the last short-circuit period from time t53 to t54, and gradually increases when the arc is regenerated at time t54, and time t6 when the feeding stops. The arc cannot be maintained at time t7 slightly later than the arc, and the arc is extinguished. When the arc is extinguished at time t7, the welding voltage Vw rises to the no-load voltage value as shown in FIG. 4D, and the no-load voltage is output until time t8. On the other hand, as shown in FIG. 5C, the welding current Iw gradually increases during the last short-circuit period from time t53 to t54, and becomes a small current value of about several tens of A during the burn-up period from time t54 to t7. And 0 at time t7.

  The average value of the welding voltage Vw during the period from time t5 to time t7 is a value determined by a predetermined anti-stick voltage setting signal Var. The value of the anti-stick voltage setting signal Var is set to a value smaller than the value of the steady welding voltage setting signal Vr.

  According to the first embodiment described above, the temperature of the base material at the start of welding is measured, and the hot start current and the hot start period are automatically set to appropriate values based on the measured base material temperature. For this reason, in this Embodiment, even if the base material temperature at the time of a welding start changes, favorable arc start property can be obtained.

[Embodiment 2]
In the invention of the second embodiment, the welding pause time Td is measured, and the hot start current Ih and the hot start period Th are automatically set from both values of the welding pause time Td and the base material temperature measurement signal Bd of the first embodiment. To do.

  FIG. 4 is a block diagram of a welding power source for carrying out the arc start control method according to the second embodiment of the present invention. This figure corresponds to FIG. 1 described above, and the same reference numerals are given to the same blocks, and the description thereof will not be repeated. In FIG. 1, a welding pause time measuring circuit TD is added to FIG. 1, the hot start current setting circuit IHR in FIG. 1 is replaced with a second hot start current setting circuit IHR2, and the hot start period setting circuit THR in FIG. This is a replacement for the 2 hot start period setting circuit THR2. Hereinafter, these different blocks will be described with reference to FIG.

  The welding stop time measuring circuit TD receives the welding start signal St and inputs from the time when the welding start signal St changes to Low level (welding end) to the time when the welding start signal St changes again to High level (welding start). Time is measured and output as a welding pause time signal Td. Therefore, the value of the welding pause time signal Td is the time from the previous welding end time to the current welding start time. When the welding stop time is measured using the welding start signal St, in FIG. 3 described above, the welding end time is set as the timing of time t5, and the welding start time is set as the timing of time t1. Although there is a difference between the time t5 and the time t7 when the welding current Iw is not energized, the time from the time t5 to the time t7 is as short as 50 to 100 ms and can be ignored. Similarly, although there is a difference between time t1 and time t2 when welding current Iw starts energization, time t1 to t2 is as short as 50 to 100 ms and can be ignored. Instead of the welding start signal St, a current energization determination signal Cd may be used. In this case, the time at which the welding current Iw is not energized can be set as the welding end time, and the time at which the welding current Iw starts to be energized can be set as the welding start time.

The second hot start current setting circuit IHR2 receives the welding start signal St, the base material temperature measurement signal Bd, and the welding pause time signal Td as described above, performs the following processing, and outputs a hot start current setting signal Ihr.
1) The value of the base material temperature measurement signal Bd at the time when the welding start signal St changes to a high level (welding start) is input to the predetermined hot start current calculation function as described above with reference to FIG. Calculate the start current value.
2) At the same time, when the welding start signal St changes to the high level (welding start), the value of the welding pause time signal Td is input to a predetermined time-corresponding hot start current calculation function as will be described later with reference to FIG. To calculate a hot start current value corresponding to time.
3) The temperature-corresponding hot start current value is compared with the time-corresponding hot start current value, and the smaller value is output as the hot start current setting signal Ihr.

The second hot start period setting circuit THR2 receives the welding start signal St, the base material temperature measurement signal Bd, and the welding pause time signal Td as described above, performs the following processing, and outputs a hot start period setting signal Thr.
1) The value of the base material temperature measurement signal Bd at the time when the welding start signal St changes to the high level (welding start) is input to the predetermined hot start period calculation function as described above with reference to FIG. Calculate the start period value.
2) At the same time, when the welding start signal St changes to the high level (welding start), the value of the welding pause time signal Td is input to a predetermined time-corresponding hot start period calculation function as will be described later with reference to FIG. To calculate a time-based hot start period value.
3) Compare the temperature-corresponding hot start period value and the time-corresponding hot start period value, and output the smaller value as the hot start period setting signal Thr.

  FIG. 5 is an example of a relationship diagram between the welding pause time signal Td (sec), the hot start current Ih (A), and the hot start period Th (ms). The horizontal axis represents the welding pause time signal Td, which is in the range of 0 to 7 seconds. The left vertical axis indicates the hot start period Th, which ranges from 0 to 10 ms. The right vertical axis indicates the hot start current Ih, which is in the range of 300 to 600A. In the figure, the base material is steel, the welding wire is steel, the diameter is 1.2 mm, and the welding method is carbon dioxide arc welding.

  The hot start current Ih indicated by the solid line is 400 A when Td ≦ 1 second, Ih increases as Td increases, and becomes 500 A within the range of Td ≧ 5 seconds. The hot start period Th indicated by the broken line is 1 ms when Td ≦ 1 second, Th increases as Td increases, and becomes 5 ms when Td ≧ 5 seconds.

  The characteristic of the solid line in the figure is a time-corresponding hot start current calculation function built in the second hot start current setting circuit IHR2 of FIG. In addition, the characteristics indicated by the broken line in FIG. 4 is a time-corresponding hot start period calculation function built in the second hot start period setting circuit THR2 in FIG. These functions are set so as to have appropriate characteristics by experiments for each welding condition such as the material of the base material, the material of the welding wire, the diameter, and the welding method.

  4 and 5 described above are cases where the hot start current Ih and the hot start period Th, which are parameters at the time of arc start, are changed according to the welding pause time signal Td, but at least one of the two parameters is set. It may be changed. For example, in order not to change the hot start period Th even if the welding pause time signal Td changes, the time-corresponding hot start duration calculation function indicated by the broken line in FIG. 5 is not dependent on the value of the weld pause time signal Td. What is necessary is just to make it a fixed value. This constant value is set to a value when Td ≧ 5 seconds. That is, the value is set when the welding wire is in a cold state.

  Since the timing chart of each signal in the welding power source described above with reference to FIG. 4 is the same as that of FIG. 3 described above, description thereof will not be repeated. However, since the automatic setting method of the hot start current Ih and the hot start period Th at the start of welding is different, this point will be described below.

  When the welding torch reaches the welding start position by the movement of the robot, a high level welding start signal St is output to the welding power source from the robot controller RC at time t1, as shown in FIG. The second hot start current setting circuit IHR2 of FIG. 4 is calculated based on the temperature-corresponding hot start current value calculated based on the value of the base material temperature measurement signal Bd at the start of welding and the welding pause time signal Td. The time-corresponding hot start current value is compared, and the smaller value is output as the hot start current setting signal Ihr. At the same time, the second hot start period setting circuit THR2 in FIG. 4 is calculated based on the temperature corresponding hot start period value calculated based on the value of the base material temperature measurement signal Bd at the start of welding and the welding pause time signal Td. The time-corresponding hot start period value is compared, and the smaller value is output as the hot start period setting signal Thr. Thus, an appropriate hot start current Ih and hot start period Th are automatically set according to the base metal temperature and the welding pause time at the start of welding.

The above-described operation will be described with numerical examples in two cases.
Case 1) Assume that the base material temperature measurement signal Bd at the start of the current welding is Bd = 120 ° C. and the welding pause time signal Td is 7.0 seconds. From FIG. 2, the temperature-corresponding hot start current value when Bd = 120 ° C. is 450 A, and the temperature-corresponding hot start period value is 3.0 ms. From FIG. 5, the time-corresponding hot start current value when Td = 7.0 seconds is 500 A, and the time-corresponding hot start period value is 5.0 ms. Since the smaller value of both values is selected, the hot start current Ih at the start of the current welding is Ih = 450 A, and the hot start period Th is 3.0 ms.

Case 2) Assume that the base material temperature measurement signal Bd = 120 ° C. and the welding pause time signal Td = 1.0 second at the start of the current welding. From FIG. 2, the temperature-corresponding hot start current value when Bd = 120 ° C. is 450 A, and the temperature-corresponding hot start period value is 3.0 ms. Further, from FIG. 5, the time-corresponding hot start current value when Td = 1.0 second is 400 A, and the time-corresponding hot start period value is 1.0 ms. Since the smaller value of both values is selected, the hot start current Ih at the start of the current welding is Ih = 400 A, and the hot start period Th is 1.0 ms.

  According to the second embodiment described above, the welding pause time from the end of the previous welding to the current welding start time is measured, the hot start current and the hot start period are calculated based on the welding pause time, and the welding pause The hot start current calculated based on the time and the hot start current calculated based on the measured base material temperature according to the first embodiment are compared, and the smaller value is set as the hot start current at the start of the current welding. Then, the hot start period calculated based on the welding pause time and the hot start period calculated based on the measured base metal temperature according to the first embodiment are compared, and the smaller value is determined as the hot start time at the start of the current welding. Set as start period. For this reason, in addition to the effects of the first embodiment, the present embodiment has the following effects. In the present embodiment, an appropriate hot start current and hot start period are automatically set according to the base metal temperature and the welding pause time at the start of welding, so it is good even if the base metal temperature and the welding pause time change. Arc startability can be obtained.

  In the first and second embodiments described above, the case where the arc welding method is consumable electrode type arc welding has been described, but the present invention can be similarly applied to the case where it is non-consumable electrode type arc welding.

DESCRIPTION OF SYMBOLS 1 Welding wire 2 Base material 3 Arc 4 Welding torch 5 Feed roll BD Temperature sensor Bd Base material temperature measurement signal CD Current energization discriminating circuit Cd Current energization discriminating signal DV Drive circuit Dv Drive signal Ea Error amplification signal EI Current error amplification circuit Ei Current error amplification signal EV Voltage error amplification circuit Ev Voltage error amplification signal FC Feed control circuit Fc Feed control signal FCR Feed speed control setting circuit Fcr Feed speed control setting signal Fi Slow down feed speed Fr Steady feed speed setting Signal Fw Feeding speed ID Current detection circuit Id Current detection signal IF Interface circuit Ih Hot start current IHR Hot start current setting circuit Ihr Hot start current setting signal IHR2 Second hot start current setting circuit Iw Welding current ON Start circuit On Start signal PM Power supply main circuit PS Welding power supply RC Robot controller St St Welding start signal SW External characteristic switching circuit Ta Anti-stick control period (signal)
TD Welding stop time measurement circuit Td Welding stop time (signal)
TH Hot start period timer circuit Th Hot start period (signal)
THR Hot start period setting circuit Thr Hot start period setting signal THR2 Second hot start period setting circuit VAR Anti stick voltage setting circuit Var Anti stick voltage setting signal VCR Voltage control setting circuit Vcr Voltage control setting signal VD Voltage detection circuit Vd Voltage detection signal Vr Steady welding voltage setting signal Vw Welding voltage Wc Welding condition signal WM Feeding motor

Claims (2)

In the arc start control method of starting welding by energizing a predetermined hot start current during a predetermined hot start period when the welding current is energized,
Measure the temperature of the base material at the start of welding, calculate and set the hot start current and the hot start period based on this base material temperature measurement value,
An arc start control method characterized by the above. Measure the welding pause time from the previous welding end time to the current welding start time, calculate the hot start current and the hot start period based on this welding pause time,
Comparing the hot start current calculated based on the welding pause time and the hot start current calculated based on the measured base material temperature, the smaller value is the hot start current at the start of the current welding. Set as
Comparing the hot start period calculated based on the welding pause time and the hot start period calculated based on the measured base material temperature, the smaller value is the hot start period at the start of welding this time. Set as
The arc start control method according to claim 1.

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