Submerged arc welding control method and submerged arc welding apparatus

Abstract

To achieve stable low-heat-input welding in submerged arc welding. [Solution] In a submerged arc welding control method that feeds a welding wire and outputs a welding voltage Vw and a welding current Iw between the welding wire and the base material to generate an arc and perform welding, the set value of the welding voltage Vw is set to a value at which a short circuit between the welding wire and the base material occurs periodically, and when a short circuit is detected at time t4 to t5, a short-circuit current Iw is supplied, and the peak value of the short-circuit current Iw is controlled to be between 1500A and 2500A.

Description

Technical Field

[0001] The present invention relates to a submerged arc welding control method and a submerged arc welding apparatus.

Background Art

[0002] Conventionally, submerged arc welding has been known. Submerged arc welding is a method in which granular flux is sprayed onto a base material, a welding wire is fed into the flux, and an arc is generated between the tip of the welding wire and the base material to perform welding. In submerged arc welding, a thick plate can be welded at high efficiency by passing a large current through a thick welding wire.

[0003] A submerged arc welding method that variably controls the feeding speed of the welding wire based on the welding voltage to control the arc length is used (see, for example, Patent Document 1).

[0004] In variable speed control, the welding voltage correlated with the arc length is maintained at an appropriate value by feedback - controlling the feeding speed based on the error between the detected value of the welding voltage and the voltage set value. In submerged arc welding using a thick - diameter wire, since the change in the wire melting speed is small even when the welding current changes, it is difficult to obtain the self - control action of the arc length generally used in consumable electrode arc welding using a constant - voltage characteristic welding power source. For this reason, in submerged arc welding, variable speed control is performed using a welding power source with constant - current characteristics to maintain the arc length at an appropriate value.

[0005] In variable speed control, when the detected value of the welding voltage is greater than the voltage set value, the arc length is longer than the desired value, so the arc length is shortened by accelerating the feeding speed to approach the desired value. Conversely, when the detected value of the welding voltage is smaller than the voltage set value, the arc length is shorter than the desired value, so the arc length is lengthened by decelerating the feeding speed to approach the desired value.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Publication No. 9-271944 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] In recent years, there has been a surge in the fabrication of offshore structures and other equipment used under low-temperature conditions. In welding these structures, low-heat input welding is required to ensure the low-temperature toughness of the joints. Submerged arc welding is fundamentally a welding method performed under conditions that prevent short circuits. However, setting the welding voltage low to achieve low-heat input welding presents a problem: short circuits can occur, leading to an unstable weld.

[0008] Therefore, the present invention aims to provide a submerged arc welding control method and a submerged arc welding apparatus that can stably perform welding, for example, with low heat input. [Means for solving the problem]

[0009] A submerged arc welding control method provided by a first aspect of the present invention is a submerged arc welding control method that feeds a welding wire and outputs a welding voltage and a welding current between the welding wire and a base material to generate an arc and perform welding, characterized in that the set value of the welding voltage is set to a value at which a short circuit between the welding wire and the base material occurs periodically, a short circuit current is supplied when the short circuit is detected, and the peak value of the short circuit current is controlled to be between 1500A and 2500A.

[0010] As an example, the submerged arc welding control method of the present invention is characterized by controlling the rate of increase of the short-circuit current to 400 A / ms or more and 1500 A / ms or less.

[0011] As an example, the submerged arc welding control method of the present invention is characterized by setting the welding voltage setting value to a value in which the short circuit occurs 1 to 50 times per second.

[0012] As an example, the submerged arc welding control method of the present invention is characterized by setting the set value of the welding voltage [V] to a calculated value within the range of (set value of the welding current [A]) × 2 / 300 + (15 to 20).

[0013] As an example, the submerged arc welding control method of the present invention is characterized by periodically switching the output polarity between electrode positive polarity and electrode negative polarity to output the AC welding voltage and welding current, and controlling the output polarity so as not to switch during a short circuit.

[0014] A submerged arc welding apparatus provided by a second aspect of the present invention is a submerged arc welding apparatus that feeds a welding wire and outputs a welding voltage and a welding current between the welding wire and a base material to generate an arc and perform welding, characterized in that the set value of the welding voltage is set to a value at which a short circuit between the welding wire and the base material occurs periodically, a short circuit current is supplied when the short circuit is detected, and the peak value of the short circuit current is controlled to be between 1500A and 2500A. [Effects of the Invention]

[0015] According to the above configuration, for example, with regard to a submerged arc welding control method and a submerged arc welding apparatus, stable welding at low heat input is possible. [Brief explanation of the drawing]

[0016] [Figure 1] This is a block diagram of a submerged arc welding apparatus according to an embodiment of the present invention. [Figure 2] This is a timing chart of each signal in the submerged arc welding apparatus shown in Figure 1 when a sinusoidal welding current is applied in AC output mode. [Figure 3] This is a timing chart of each signal in the submerged arc welding apparatus shown in Figure 1 when in DC output mode. [Modes for carrying out the invention]

[0017] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0018] FIG. 1 is a block diagram of a submerged arc welding apparatus according to an embodiment of the present invention. Hereinafter, each block will be described with reference to the figure.

[0019] The main power circuit PM is connected to a commercial power source (not shown) such as a three-phase 200V power source, and performs inverter control according to the current error amplification signal Ei described later and the polarity switching signal Spn described later. According to the polarity switching signal Spn, the electrode positive polarity EP and the electrode negative polarity EN are switched to output an alternating current or direct current welding current Iw and a welding voltage Vw. Although not shown, this main power circuit PM includes a primary rectifier that rectifies the commercial power source, a smoothing capacitor that smooths the rectified direct current, a primary side inverter circuit that converts the smoothed direct current into a high-frequency alternating current, a high-frequency transformer that steps down the high-frequency alternating current to a voltage value suitable for welding, a secondary rectifier that rectifies the stepped-down high-frequency alternating current into a direct current, a reactor that smooths the rectified direct current, a secondary side inverter circuit that switches the smoothed direct current to the electrode positive polarity EP and the electrode negative polarity EN according to the polarity switching signal Spn, a modulation circuit that outputs a pulse width modulation signal with the current error amplification signal Ei as an input, and a drive circuit that drives the switching element of the primary side inverter circuit with the pulse width modulation signal as an input.

[0020] The welding wire 1 is fed through the welding torch 4 by the rotation of the feeding roll 5 coupled to the feeder WM, and an arc 3 is generated between the welding wire 1 and the base material 2. A welding voltage Vw is applied between the power supply tip (not shown) of the welding torch 4 and the base material 2, and a welding current Iw is energized. A flux feeder 6 is arranged in the submerged arc welding apparatus to supply a flux (not shown) to the arc generation part. Since the arc generation part is covered by the flux, the arc 3 cannot be visually recognized from the outside. The welding torch 4 is mounted on an automatic carriage (not shown) and moves along the welding line.

[0021] The output mode setting circuit MR is a switch or the like provided on the front panel of the welding power source. When the alternating current output mode is selected by the welder, it outputs an output mode setting signal Mr that becomes High level, and when the direct current output mode is selected, it outputs a Low level.

[0022] The current setting circuit IR outputs a predetermined current setting signal Ir.

[0023] The voltage setting circuit VR takes the above current setting signal Ir as an input and outputs a voltage setting signal Vr set as follows in 1) or 2) below where a short circuit between the welding wire 1 and the base material 2 occurs periodically. 1) Set the voltage setting signal Vr to a value at which a short circuit occurs 1 to 50 times per second. 2) Set the voltage setting signal Vr [V] within the range of Ir [A] × 2 / 300 + 15 ≤ Vr ≤ Ir × 2 / 300 + 20.

[0024] The voltage detection circuit VD detects the instantaneous value of the welding voltage Vw, converts it to an absolute value, and outputs a voltage detection signal Vd.

[0025] The voltage effective value / average value detection circuit VED takes the above voltage detection signal Vd as an input, calculates the effective value or average value from that value, and outputs a voltage effective value / average value detection signal Ved.

[0026] The external characteristic control circuit CC takes the above current setting signal Ir, the above voltage setting signal Vr, the above output mode setting signal Mr, the above voltage effective value / average value detection signal Ved, and the above voltage detection signal Vd as inputs and outputs a current effective value / average value setting signal Ier and a direct current setting signal Idr calculated based on the following formula (1) or (2). 1) When the output mode setting signal Mr = High level (alternating current output mode) The external characteristic is the output characteristic of the welding power source, and can be expressed as a function Ve = f(Ie) that takes the effective value or average value Ie of the welding current Iw as an input and outputs the effective value or average value Ve of the welding voltage Vw. When the function is defined as a straight line with a slope K passing through the intersection point of the current setting signal Ir and the voltage setting signal Vr, the following formula is obtained. Ve = K·(Ie-Ir) + Vr Here, the slope K is a negative value and is set within the range of -5 / ~-25 (V / 100A). Rearranging the above equation in terms of Ie, replacing Ie with the current RMS value / average value setting signal Ier, and replacing Ve with the voltage RMS value / average value detection signal Ved, we obtain the following equation. Ier = (Ved - Vr) / K + Ir (1) In AC output mode, output control is performed based on external characteristics using this formula. 2) When the output mode setting signal Mr = Low level (DC output mode) In the above equation (1), replacing Ier with Idr and Ved with Vd results in the following equation. Idr = (Vd - Vr) / K + Ir (2) In DC output mode, output control is performed based on external characteristics using this formula.

[0027] The current detection circuit ID detects the instantaneous value of the welding current Iw, converts it to an absolute value, and outputs a current detection signal Id.

[0028] The current RMS / average value detection circuit IED takes the above-mentioned current detection signal Id as input, calculates the RMS value or average value from that value, and outputs the current RMS / average value detection signal Ied.

[0029] The current amplitude modulation circuit (AMC) takes the above-mentioned RMS / average value detection signal Ied and the above-mentioned RMS / average value setting signal Ier as inputs, performs modulation control based on the error amplification value of both values, and outputs a current amplitude modulation signal Amc. This circuit changes the amplitude of the welding current so that the RMS or average value of the welding current Iw becomes equal to the value of the current RMS / average value setting signal Ier.

[0030] The electrode positive polarity period setting circuit TPR outputs a predetermined electrode positive polarity period setting signal Tpr. The electrode negative polarity period setting circuit TNR outputs a predetermined electrode negative polarity period setting signal Tnr.

[0031] The short-circuit detection circuit SD receives the voltage detection signal Vd as input and outputs a short-circuit detection signal Sd that becomes High level when this value is less than a predetermined short-circuit detection value, indicating that the welding wire 1 and the base material 2 are in a short-circuit state, and Low level when this value is greater than or equal to the value, indicating that an arc is being generated. In submerged arc welding, a welding voltage of at least approximately 20V is required to maintain the arc, regardless of the diameter of the welding wire. Therefore, the above short-circuit detection value must be 20V or less, and more preferably between 10V and 18V. If the short-circuit detection value exceeds 18V, it becomes easy to misidentify instantaneous changes in welding voltage as a short circuit. Also, in submerged arc welding, the output terminal of the welding power supply and the welding torch are sometimes connected by a welding cable several tens of meters long. In this case, if the welding voltage detection position is at the output terminal, the voltage drop due to the welding cable will be added to the original welding voltage. For this reason, if the short-circuit detection value becomes too small, it becomes difficult to detect a short circuit. For this reason, it is desirable that the short-circuit detection value be 10V or higher.

[0032] The AC current setting circuit IAR takes the above-mentioned electrode positive polarity period setting signal Tpr, electrode negative polarity period setting signal Tnr, current amplitude modulation signal Amc, and short-circuit detection signal Sd as inputs, performs the following processing 1) to 5), and outputs an AC current setting signal Iar in the form of a half-period waveform of a sine wave or square wave, as well as a polarity signal Tpn. 1) During the electrode positive polarity period Tep, set by the electrode positive polarity period setting signal Tpr, the start and end points of the period become predetermined polarity switching current values, and a half-period waveform of a sinusoidal wave with amplitude set by the current amplitude modulation signal Amc is output as the AC current setting signal Iar. During the electrode positive polarity period Tep, a high-level polarity signal Tpn is output. 2) Subsequently, during the electrode negative polarity period Ten, set by the electrode negative polarity period setting signal Tnr, the start and end points of the period become the polarity switching current value, and a half-period waveform of a sinusoidal wave with an amplitude set by the current amplitude modulation signal Amc is output as the AC current setting signal Iar. During the electrode negative polarity period Ten, a low-level polarity signal Tpn is output. 3) When the short-circuit detection signal Sd is at a low level (arc period), repeat steps 1) and 2) above. 4) When the short-circuit detection signal Sd is at a high level (short-circuit period) and the polarity signal Tpn is at a high level (electrode positive polarity EP), only step 1) above is repeated. 5) When the short-circuit detection signal Sd is at a high level (short-circuit period) and the polarity signal Tpn is at a low level (negative electrode polarity EN), only step 2) above is repeated.

[0033] The polarity switching setting circuit SPN takes the above output mode setting signal Mr, the above short-circuit detection signal Sd, and the above polarity signal Tpn as inputs, performs the following processing, and outputs the polarity switching signal Spn. 1) When the output mode setting signal Mr is at a high level (AC output mode), the short-circuit detection signal Sd is at a low level (arc period), and the polarity signal Tpn is at a high level (electrode positive polarity EP), a high-level polarity switching signal Spn is output. 2) When the output mode setting signal Mr is at a high level (AC output mode), the short-circuit detection signal Sd is at a low level (arc period), and the polarity signal Tpn is at a low level (electrode negative polarity EN), a low-level polarity switching signal Spn is output. 3) When the output mode setting signal Mr is at a high level (AC output mode) and the short-circuit detection signal Sd changes to a high level (short-circuit period), the polarity switching signal Spn is output while maintaining its value at that time. This controls the system so that polarity switching does not occur during the short-circuit period. 4) When the output mode setting signal Mr is at a low level (DC output mode), a polarity switching signal Spn is output at a high level when the electrode positive polarity EP is set, and at a low level when the electrode negative polarity EN is set.

[0034] The short-circuit current peak value setting circuit IPR outputs a predetermined short-circuit current peak value setting signal Ipr. It is preferable to set the value of the short-circuit current peak value setting signal Ipr to 1500A or more and 2500A or less, and more preferably to 1800A or more and 2200A or less.

[0035] The short-circuit current rise rate setting circuit SR outputs a predetermined short-circuit current rise rate setting signal Sr. It is preferable to set the value of the short-circuit current rise rate setting signal Sr to 400 A / ms or more and 1500 A / ms or less, and more preferably to 600 A / ms or more and 1200 A / ms or less.

[0036] The short-circuit current setting circuit ISR takes the current control setting signal Icr (described later), the short-circuit discrimination signal Sd, the short-circuit current peak value setting signal Ipr, and the short-circuit current rise rate setting signal Sr as inputs. When the short-circuit discrimination signal Sd changes to a high level (short-circuit period), the value of the current control setting signal Icr increases at the rate set by the short-circuit current rise rate setting signal Sr, and when it reaches the value of the short-circuit current peak value setting signal Ipr, it outputs a short-circuit current setting signal Isr that maintains that value.

[0037] The current control setting circuit ICR takes the above output mode setting signal Mr, the above short-circuit detection signal Sd, the above AC current setting signal Iar, the above DC current setting signal Idr, and the above short-circuit current setting signal Isr as inputs, performs the following processing 1) or 2), and outputs the current control setting signal Icr. 1) When the output mode setting signal Mr is at a high level (AC output mode) When the short-circuit detection signal Sd is at a low level (arc period), the AC current setting signal Iar is output as the current control setting signal Icr. When the short-circuit detection signal Sd is at a high level (short-circuit period), the short-circuit current setting signal Isr is output as the current control setting signal Icr. 2) When the output mode setting signal Mr is at a low level (DC output mode) When the short-circuit detection signal Sd is at a low level (arc period), the DC current setting signal Idr is output as the current control setting signal Icr. When the short-circuit detection signal Sd is at a high level (short-circuit period), the short-circuit current setting signal Isr is output as the current control setting signal Icr.

[0038] The current error amplification circuit EI takes the above-mentioned current control setting signal Icr and current detection signal Id as inputs, amplifies the error between the two values, and outputs a current error amplification signal Ei. This circuit enables constant current control of the welding apparatus.

[0039] The feed speed variable control circuit FMC takes the above-mentioned RMS / average value detection signal Ved and the above-mentioned voltage setting signal Vr as inputs and performs feed speed variable control using P (proportional) control, PI (proportional-integral) control, or PID (proportional-integral-derivative) control based on the error amplification value of both values, and outputs a feed speed modulation signal Fmc. This circuit variably controls the feed speed Fw so that the arc length is maintained at an appropriate value. In DC output mode, the voltage detection signal Vd is used instead of the RMS / average value detection signal Ved.

[0040] The feed control circuit FC takes the feed speed modulation signal Fmc as input and outputs a feed control signal Fc to the feeder WM to control the feed speed Fw of the welding wire 1 to a speed determined by the feed speed modulation signal Fmc.

[0041] Figure 2 shows the timing charts for each signal in the submerged arc welding apparatus shown in Figure 1 when a sinusoidal welding current is applied in AC output mode. 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 short-circuit detection signal Sd, and Figure (D) shows the time variation of the polarity switching signal Spn. The operation of each signal will be explained below with reference to the figure.

[0042] In the figure, positive values ​​above 0A and 0V indicate the electrode is positively polarized (EP), while negative values ​​below 0A and 0V indicate the electrode is negatively polarized (EN).

[0043] During the period from time t1 to t2, as shown in Figure (D), the polarity switching signal Spn is at a high level, resulting in a positive electrode polarity EP. As shown in Figure (A), during the positive electrode polarity period Tep from time t1 to t2, the welding current Iw has a positive polarity switching current value at the start and end points t1 and t2 of the period, and is a half-period waveform of a positive sine wave with amplitude set by the current amplitude modulation signal Amc. During the period from time t2 to t3, as shown in Figure (D), the polarity switching signal Spn is at a low level, resulting in a negative electrode polarity EN. As shown in Figure (A), during the negative electrode polarity period Ten from time t2 to t3, the welding current Iw has a negative polarity switching current value at the start and end points t2 and t3 of the period, and is a half-period waveform of a negative sine wave with amplitude set by the current amplitude modulation signal Amc. The positive electrode polarity period Tep is set by the positive electrode polarity period setting signal Tpr in Figure 1. The electrode negative polarity period Ten is set by the electrode negative polarity period setting signal Tnr in Figure 1. The current RMS / average value setting signal Ier in Figure 1 is calculated by inputting the voltage RMS / average value detection signal Ved into equation (1) above. The amplitude of the welding current is modulated and controlled so that the current RMS / average value detection signal Ied in Figure 1 is equal to the current RMS / average value setting signal Ier. This enables external characteristic control. For example, Tep = 10 ms, Ten = 10 ms, polarity switching current value = ±200 A, amplitude ±1000 A.

[0044] As shown in Figure (B), the welding voltage Vw has a waveform similar to a square wave. The RMS value or average value of the welding voltage Vw correlates with the arc length. The feed rate Fw in Figure 1 is variable-speed controlled so that the RMS / average voltage detection signal Ved is equal to the voltage setting signal Vr in Figure 1. This controls the arc length.

[0045] From time t3, as shown in Figure (D), the polarity switching signal Spn returns to a high level (electrode positive polarity EP), and the above operation is repeated. At time t4 during this electrode positive polarity EP, when the welding wire and the base material are short-circuited, as shown in Figure (B), the welding voltage Vw rapidly decreases to a short-circuit voltage value of a few volts, and as shown in Figure (C), the short-circuit detection signal Sd changes to a high level. In response to this, as shown in Figure (A), the welding current Iw is controlled to the value of the short-circuit current setting signal Isr in Figure 1. From time t4, the welding current Iw increases at the rate set by the short-circuit current increase rate setting signal Sr in Figure 1, and when it reaches the peak value set by the short-circuit current peak value setting signal Ipr in Figure 1, it maintains that value until the short circuit is released at time t5. During the short-circuit period from time t4 to t5, as shown in Figure (D), the polarity switching signal Spn remains at a high level, and no polarity switching occurs. At time t5, when the short circuit is released and the arc is re-generated, the welding voltage Vw rapidly increases to an arc voltage value of several tens of volts, as shown in Figure (B), and the short-circuit detection signal Sd changes to a low level, as shown in Figure (C). In response to this, as shown in Figure (A), the welding current Iw decreases from time t5 and returns to the sinusoidal half-period waveform during the arc period. Then, at time t6, the welding current Iw becomes the polarity switching current value, and as shown in Figure (D), the polarity switching signal Spn changes to a low level, resulting in the electrode being negative polarity EN. From here on, the operation is as described in Time t2~t3.

[0046] In this figure, the voltage setting signal Vr in Figure 1 is set to a value that causes short circuits to occur periodically in order to perform low-heat input welding. Conventional submerged arc welding is a welding method that is basically performed under welding conditions in which short circuits do not occur. Therefore, when the welding voltage is set low in order to perform low-heat input welding, there is a problem that short circuits occur and the welding state becomes unstable. In this embodiment, by applying a short-circuit current with a large current value, the welding state can be stabilized even under welding voltage conditions in which short circuits occur. The short-circuit period at time t4 to t5 is, for example, about 5 to 200 ms. Short circuits occur about 1 to 50 times per second.

[0047] Figure 3 shows the timing charts for each signal in the submerged arc welding apparatus shown in Figure 1, in DC output mode. 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 short-circuit detection signal Sd, and Figure (D) shows the time variation of the polarity switching signal Spn. The operation of each signal will be explained below with reference to the figure.

[0048] As shown in Figure (D), the DC output mode and the electrode polarity EP are positive, so the polarity switching signal Spn is at a high level for the entire period, resulting in the electrode polarity EP.

[0049] During the period from time t1 to t2, the arc period occurs, and as shown in Figure (C), the short-circuit detection signal Sd is at a low level. As shown in Figure (A), the welding current Iw is a DC waveform and is controlled to the value of the DC current setting signal Idr in Figure 1. The DC current setting signal Idr is calculated by inputting the voltage detection signal Vd into equation (2) above. This enables external characteristic control. As shown in Figure (B), the welding voltage Vw is a DC waveform and is a value correlated with the arc length. The feed speed Fw in Figure 1 is variable-speed controlled so that the voltage detection signal Vd is equal to the voltage setting signal Vr in Figure 1. This enables arc length control.

[0050] At time t2, when the welding wire and the base metal are short-circuited, the welding voltage Vw rapidly decreases to a short-circuit voltage of several volts, as shown in Figure (B), and the short-circuit detection signal Sd changes to a high level, as shown in Figure (C). In response to this, the welding current Iw is controlled to the value of the short-circuit current setting signal Isr in Figure 1, as shown in Figure (A). The welding current Iw increases from time t2 at the rate set by the short-circuit current increase rate setting signal Sr in Figure 1, and when it reaches the peak value set by the short-circuit current peak value setting signal Ipr in Figure 1, it maintains that value until the short circuit is released at time t3. At time t3, when the short circuit is released and the arc is regenerated, the welding voltage Vw rapidly increases to an arc voltage of several tens of volts, as shown in Figure (B), and the short-circuit detection signal Sd changes to a low level, as shown in Figure (C). In response to this, the welding current Iw decreases from time t3, as shown in Figure (A), and returns to the DC waveform during the arc period.

[0051] In this figure, the voltage setting signal Vr in Figure 1 is set to a value that causes short circuits to occur periodically in order to perform low-heat input welding. Conventional submerged arc welding is a welding method that is basically performed under welding conditions in which short circuits do not occur. Therefore, when the welding voltage is set low in order to perform low-heat input welding, there is a problem that short circuits occur and the welding state becomes unstable. In this embodiment, by applying a short-circuit current with a large current value, the welding state can be stabilized even under welding voltage conditions in which short circuits occur. The short-circuit period at time t2 to t3 is, for example, about 5 to 200 ms. Short circuits occur about 1 to 50 times per second.

[0052] The effects of this embodiment are described below. According to this embodiment, the welding voltage is set to a value at which short circuits between the welding wire and the base material occur periodically. When a short circuit is detected, a short-circuit current is supplied, and the peak value of the short-circuit current is controlled to be between 1500A and 2500A. Conventional submerged arc welding is a welding method that is basically performed under welding conditions in which short circuits do not occur. For this reason, in conventional submerged arc welding, if the welding voltage is set low in order to perform welding with low heat input, there is a problem that short circuits occur periodically and the welding state becomes unstable. This is because, in the conventional technology, even if a short circuit occurs, no special control is performed to quickly resolve the short circuit and return to the arc generation state, resulting in a prolonged short-circuit period. In contrast, in this embodiment, when a short circuit occurs, control is performed to supply a short-circuit current with a peak value of 1500A to 2500A. By supplying a short-circuit current with a high current value, the melting of the protruding part of the welding wire is promoted, and the short circuit can be resolved early. As a result, in this embodiment, the welding state can be maintained stably even when short circuits occur periodically. If the peak value of the short-circuit current is less than 1500A, the mechanism for quickly clearing the short circuit will be insufficient, and if it exceeds 2500A, the load on the welding equipment will become too heavy. It is even preferable to control the peak value of the short-circuit current between 1800A and 2200A.

[0053] More preferably, according to this embodiment, the rate of increase of the short-circuit current is controlled to be between 400 A / ms and 1500 A / ms. If the rate of increase is less than 400 A / ms, the effect of releasing the short circuit early will be insufficient. If the rate of increase exceeds 1500 A / ms, the welding state may become unstable. Therefore, by controlling the rate of increase within the above range, the short circuit can be released early without the welding state becoming unstable. It is even more preferable to control the rate of increase to be between 600 A / ms and 1200 A / ms.

[0054] More preferably, according to this embodiment, the welding voltage is set to a value at which short circuits occur 1 to 50 times per second. When short circuits occur within the above range, low heat input welding can be performed while maintaining a stable welding state. When no short circuits occur, the reduction in heat input becomes insufficient. If the number of short circuits exceeds 50, the welding state becomes unstable. A range of 5 to 30 times / second for the number of short circuits is even more preferable.

[0055] More preferably, according to this embodiment, the welding voltage setting value [V] is set to a range of calculated values ​​of (welding current setting value [A]) × 2 / 300 + (15 to 20). Setting the welding voltage setting value to the above range allows for low heat input welding while maintaining a stable welding state. If the welding voltage setting value exceeds the calculated value of (welding current setting value) × 2 / 300 + 20, the heat input reduction becomes insufficient. If the welding voltage setting value falls below the calculated value of (welding current setting value) × 2 / 300 + 15, the welding state becomes unstable.

[0056] More preferably, according to this embodiment, the output polarity is periodically switched between positive electrode polarity and negative electrode polarity to output AC welding voltage and welding current, and the output polarity is controlled not to switch during a short circuit. If the output polarity is switched during a short circuit, the welding current will decrease to 0A, making it impossible to quickly resolve the short circuit. For this reason, in this embodiment, the output polarity is controlled not to switch during a short circuit in order to resolve the short circuit early.

[0057] More preferably, according to this embodiment, after the short circuit is released and the arc is re-generated, the absolute value of the welding current is reduced to the polarity switching current value to switch the output polarity. This allows for smooth switching of the output polarity after the short circuit is released, thereby improving the arc generation condition.

[0058] Furthermore, according to this embodiment, the submerged arc welding apparatus sets the welding voltage to a value at which a short circuit between the welding wire and the base material occurs periodically, and when a short circuit is detected, it supplies a short-circuit current and controls the peak value of the short-circuit current to between 1500A and 2500A. The submerged arc welding apparatus according to this embodiment achieves the above-mentioned effects. [Explanation of symbols]

[0059] 1: Welding wire, 2: Base metal, 3: Arc, 4: Welding torch, 5: Feeding roll, 6: Flux feeder, AMC: Current amplitude modulation circuit, Amc: Current amplitude modulation signal, CC: External characteristic control circuit, EI: Current error amplification circuit, Ei: Current error amplification signal, EN: Electrode negative polarity, EP: Electrode positive polarity, FC: Feeding control circuit, Fc: Feeding control signal, FMC: Feeding variable speed control circuit, Fmc: Feeding speed modulation signal, Fw: Feeding speed, IAR: AC current setting circuit, Iar: AC current setting signal, ICR: Current control setting circuit, Icr: Current control setting signal, ID: Current detection circuit, Id: Current detection signal, Idr: DC current setting signal, IED: Current RMS / average value detection circuit, Ied: Current RMS / average value detection signal, IPR: Short-circuit current peak value setting circuit, Ipr: Short-circuit current peak value setting signal, IR: Current setting circuit, Ir :Current setting signal, ISR:Short circuit current setting circuit, Isr:Short circuit current setting signal, Iw:Welding current, MR:Output mode setting circuit, Mr:Output mode setting signal, PM:Power supply main circuit, SD:Short circuit detection circuit, Sd:Short circuit detection signal, SPN:Polarity switching setting circuit, Spn:Polarity switching signal, SR:Short circuit current rise rate setting circuit, Sr:Short circuit current rise rate setting signal, Ten:Electrode negative polarity period, Tep:Electrode positive polarity period, TNR:Electrode negative polarity period setting circuit, Tnr:Electrode negative polarity period setting signal, Tpn:Polarity signal, TPR:Electrode positive polarity period setting circuit, Tpr:Electrode positive polarity period setting signal, VD:Voltage detection circuit, Vd:Voltage detection signal, VED:Voltage RMS / average value detection circuit, Ved:Voltage RMS / average value detection signal, VR:Voltage setting circuit, Vr:Voltage setting signal, Vw:Welding voltage, WM:Feeder

Claims

1. In a submerged arc welding control method that feeds a welding wire and outputs a welding voltage and welding current between the welding wire and the base material to generate an arc and perform welding, A submerged arc welding control method characterized by setting the welding voltage to a value at which a short circuit between the welding wire and the base material occurs periodically, supplying a short-circuit current when the short circuit is detected, and controlling the peak value of the short-circuit current to be between 1500A and 2500A.

2. The submerged arc welding control method according to claim 1, characterized in that the rate of increase of the short-circuit current is controlled to be between 400 A / ms and 1500 A / ms.

3. The submerged arc welding control method according to claim 1 or 2, characterized in that the setting value of the welding voltage is set to a value in which the short circuit occurs 1 to 50 times per second.

4. The submerged arc welding control method according to claim 1 or 2, characterized in that the set value [V] of the welding voltage is set within the range of (set value [A] of the welding current) × 2 / 300 + (15 to 20).

5. The submerged arc welding control method according to claim 1 or 2, characterized in that the output polarity is periodically switched between electrode positive polarity and electrode negative polarity to output the AC welding voltage and welding current, and the output polarity is controlled not to be switched during the short circuit.

6. In a submerged arc welding apparatus that feeds a welding wire and outputs a welding voltage and welding current between the welding wire and the base material to generate an arc and perform welding, A submerged arc welding apparatus characterized by setting the welding voltage to a value at which a short circuit between the welding wire and the base material occurs periodically, supplying a short-circuit current when the short circuit is detected, and controlling the peak value of the short-circuit current to be between 1500A and 2500A.

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