JP2023031067A - Lap fillet welding method and welding device - Google Patents

Abstract

To provide a lap fillet welding method capable of suppressing occurrence of a humping bead which occurs when the target position of welding wire is deviated toward an upper plate side in a downward lap fillet welding.SOLUTION: A lap fillet welding method performs arc-welding by supplying welding wire to a corner part of overlapped portion of a first base material and a second base material. The method comprises: detecting a welding-current; determining whether or not the welding-current is increased due to that molten metal is swelled at the corner part; and when determining that the welding-current is increased, decreasing a current command value for controlling the welding current.SELECTED DRAWING: Figure 4

Description

The present invention relates to a lap fillet welding method and a welding apparatus.

One type of welded joint is a lap joint in which two plate materials are placed on each other substantially horizontally. A corner weld consisting of the top plate edge and bottom plate of a lap joint is called a lap fillet weld. Patent Literature 1 discloses a technique for detecting a positional deviation of a welding torch with respect to a joint position from variations in arc time and preventing burn-through.

Japanese Patent No. 4112213

In downward lap fillet welding, if the target position of the welding wire deviates to the upper plate side, the heat input to the upper plate increases, and there is a technical problem that only the upper plate melts down and a humping bead is generated. . When the target position of the welding wire shifts toward the upper plate and the heat input to the upper plate increases, the upper plate melts excessively, and the molten metal spreads and rises. A large amount of molten metal cannot follow the welding wire and arc, resulting in a nodular bead. When such a state is repeated, a uniform bead is not formed, and a discontinuous hump-like bead is formed.
Patent Literature 1 discloses a technique for detecting displacement of a welding torch and preventing burn-through. No technology is disclosed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fillet welding method and a welding apparatus capable of suppressing the occurrence of a humping bead that may occur when the target position of the welding wire is shifted toward the upper plate in downward lap fillet welding. to do.

A lap fillet welding method according to one aspect of the present invention is a lap fillet welding method in which arc welding is performed by feeding a welding wire to a corner of a first base material and a second base material that are overlapped, The welding current is detected, and it is determined whether or not the welding current has increased due to the buildup of the molten metal at the corner. When it is determined that the welding current has increased, the current command value for controlling the welding current is decreased.

A welding apparatus according to one aspect of the present invention is a welding apparatus that performs arc welding by feeding a welding wire to corners of a first base material and a second base material that are superimposed on each other, wherein a welding current is detected. a detection circuit, a power supply circuit for outputting a welding current, and a control circuit for determining whether or not the welding current has increased due to the rise of the molten metal at the corner, and for controlling the welding current when it is determined that the welding current has increased. and an adjustment circuit that reduces the current command value.

According to the above, in downward lap fillet welding, it is possible to suppress the occurrence of a humping bead that may occur when the target position of the welding wire deviates toward the upper plate.

It is a schematic diagram which shows the structural example of an arc welding apparatus. 1 is a block diagram showing a configuration example of a welding power source; FIG. It is a block diagram which shows the structural example of an adjustment circuit. 5 is a flowchart showing an adjustment processing procedure according to the embodiment;

A lap fillet welding method and a welding apparatus according to embodiments of the present disclosure will be described below with reference to the drawings. The present disclosure is not limited to these examples, but is indicated by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims. Moreover, at least part of the embodiments described below may be combined arbitrarily.

Hereinafter, the present invention will be described in detail based on the drawings showing its embodiments.
FIG. 1 is a schematic diagram showing a configuration example of an arc welding apparatus, and FIG. 2 is a block diagram showing a configuration example of a welding power source. The arc welding apparatus according to the present embodiment is a consumable electrode gas shield arc welder for performing downward lap fillet welding. The base material A is a lap joint composed of an upper plate A1 (first base material) and a lower plate A2 (second base material) that are substantially horizontally overlapped. The arc welding apparatus according to the present embodiment is, for example, a pulse welder, and performs arc welding by feeding the welding wire W to the corner formed by the end of the upper plate A1 and the lower plate A2 to perform arc welding. Carry out the welding method.

The arc welding apparatus includes a welding robot 1 to which a welding torch 11 and a wire feed section 12 are attached, a welding power source 2, a control device 3, and a shield gas supply section (not shown). In FIG. 1, thick lines are power supply cables, and thin lines are control communication lines.

Control device 3 sets welding conditions for welding power source 2 and controls the operation of welding power source 2 . Control device 3 also controls the operation of welding robot 1 by outputting an operation control signal to welding robot 1 .

The welding robot 1 has a base fixed to an appropriate location on the floor. A plurality of arms are rotatably connected to the base through shafts. A welding torch 11 is held at the tip portion of the arm connected to the tip side. A servomotor is provided at the linking portion of the arm, and each arm rotates around the shaft portion by the rotational driving force of the servomotor. Rotation of the servomotor is controlled by the controller 3 . The control device 3 can move the welding torch 11 up, down, front, back, left and right with respect to the base material A by rotating each arm. An encoder for outputting a signal indicating the rotational position of the arm to the control device 3 is provided at the connecting portion of each arm. and posture recognition.

The shield gas supply unit supplies shield gas to the welding torch 11 . The shield gas is for preventing oxidation of the base material A and the welding wire W melted by the arc. The shielding gas is, for example, argon Ar, a mixed gas of carbon dioxide CO ₂ and helium He, or a mixed gas of argon Ar and helium He.

The welding torch 11 is made of a conductive material such as a copper alloy, and has a cylindrical contact tip that guides the welding wire W to the welded portion of the base material A and supplies the welding current Iw required to generate an arc. . The contact tip contacts the welding wire W passing therethrough and supplies the welding wire W with the welding current Iw. The welding torch 11 has a hollow cylindrical shape surrounding the contact tip, and has a nozzle for injecting the shield gas supplied from the shield gas supply part to the welded part.

The welding wire W is, for example, a solid wire, a metal cored wire or a flux cored wire and functions as a consumable electrode. The welding wire W is, for example, a pack wire that is spirally wound and stored in a pail pack, or a reel wire that is wound on a wire reel.

The wire feeder 12 has a feed roller that feeds the welding wire W to the welding torch 11 and a motor that rotates the feed roller. The wire feeding unit 12 rotates the feeding roller to draw out the welding wire W from the pail pack or wire reel, and feeds the drawn welding wire W to the welding torch 11 at a constant speed.

The welding power supply 2 includes a power supply circuit 21 , a detector 22 , a power control circuit 23 and a feed control circuit 24 . The power supply circuit 21 is connected to the contact tip of the welding torch 11 and the base material A via a power supply cable, applies a welding voltage Vw between the welding wire W and the base material A, and supplies a welding current Iw.

The detection unit 22 includes a voltage detection circuit 22a and a current detection circuit 22b. The current detection circuit 22b detects the welding current Iw flowing through the arc during the welding process, and outputs a current detection signal Id indicating the detected current value to the power supply control circuit 23. The voltage detection circuit 22 a detects the welding voltage Vw applied to the welding torch 11 and the base material A, and outputs a voltage detection signal Vd indicating the detected voltage value to the power supply control circuit 23 .

The power supply control circuit 23 includes a current command value calculation circuit 23a, an adjustment circuit 25, and a difference amplification circuit 23b. The voltage detection signal Vd and the current detection signal Id are input to the current command value calculation circuit 23a. The current command value calculation circuit 23a calculates the current command value based on the current value and the voltage value detected by the voltage detection circuit 22a and the current detection circuit 22b, and the set voltage value and the set current value. A current command signal Irc indicating a current command value is output to the adjustment circuit 25 . The set voltage value and the set current value are set by the controller 3, for example. The current command value includes information on the target value of the welding current Iw that flows between the welding wire W and the base material A. The adjustment circuit 25 adjusts the current command value so as to suppress a humping bead that may occur when the target position of the welding wire W shifts toward the upper plate in downward lap fillet welding. A current command signal Irc indicating a current command value is output to the differential amplifier circuit 23b. The difference amplifier circuit 23b amplifies the difference between the current detection signal Id output from the current detection circuit 22b and the current command signal Irc output from the adjustment circuit 25, and outputs an amplified difference signal ΔI indicating the difference. Output to the power supply circuit 21 . A power supply circuit 21 inputs a commercial AC power supply, performs inverter control, thyristor phase control, etc., based on the difference amplification signal ΔI, and outputs a welding current Iw suitable for welding.

The feed control circuit 24 outputs a feed control signal for feeding the welding wire W at a feed speed corresponding to the set current value to the wire feeding section 12 to control the feed speed of the welding wire W. .

FIG. 3 is a block diagram showing a configuration example of the adjustment circuit 25. As shown in FIG. The adjustment circuit 25 is a device that adjusts the current command value. The adjustment circuit 25 is a computer or arithmetic device including a processing section 25a, an input section 25b, an output section 25c, and a storage section 25d.

The storage unit 25d is non-volatile memory such as EEPROM (Electrically Erasable Programmable ROM) and flash memory. In downward lap fillet welding, the storage unit 25d performs a process of optimizing the current command value in order to solve the problem of humping beads that may occur when the target position of the welding wire W shifts toward the upper plate side. It stores a computer program 25e and a table 25f for execution. The table 25f stores the setting current value and the rate of increase of the welding current Iw due to the swelling of the molten metal in association with each other. When the target position of the welding wire W shifts toward the upper plate A1, heat input concentrates on the upper plate A1, and the upper plate A1 melts down and the molten metal rises. Depends on current value.

The processing unit 25a is a computer having a CPU (Central Processing Unit) or a processor such as a multi-core CPU, a ROM (Read Only Memory), a RAM (Random Access Memory), an input/output interface, etc. The interface includes an input unit 25b , an output unit 25c and a storage unit 25d are connected. By executing the computer program 25e stored in the storage unit 25d, the processing unit 25a determines whether or not the molten metal rises when the target position of the welding wire W is displaced toward the upper plate A1. A process for increasing or decreasing the current command value is executed according to the state.

The input section 25b is connected to the current command value calculation circuit 23a and the current detection circuit 22b. The current command signal Irc output from the current command value calculation circuit 23a and the current detection signal Id output from the current detection circuit 22b are input to the input unit 25b.

The output section 25c is connected to the differential amplifier circuit 23b. The current command signal Irc whose current command value is adjusted by the arithmetic processing of the processing unit 25a is output to the difference amplifier circuit 23b.

Although the current command value calculation circuit 23a, the difference amplification circuit 23b, and the adjustment circuit 25 have been described as separate circuits, these circuits may be configured by one computer or arithmetic circuit.

FIG. 4 is a flowchart showing an adjustment processing procedure according to this embodiment. The control device 3 controls the operations of the welding robot 1 and the welding power source 2 to perform fillet welding of the base material A, which is a lap joint. The welding speed is 100 cm/min or more and 120 cm/min or less. A pulse period for pulse welding is, for example, 4 ms (250 Hz). Before or at the start of fillet welding, the adjustment circuit 25 uses the set current value as a key to determine the swelling of the molten metal that can occur when the target position of the welding wire W is shifted toward the upper plate. A rate is read from the table 25f (step S11).

Next, the adjustment circuit 25 detects the welding current Iw with the current detection circuit 22b (step S12). Specifically, adjustment circuit 25 acquires data indicating the current value of welding current Iw from current detection signal Id output from welding power source 2 .

The adjustment circuit 25 calculates an average output current based on the detected welding current Iw and determines whether or not the average output current has suddenly increased (step S13). In downward lap fillet welding, if the target position of the welding wire W shifts toward the upper plate, the heat input concentrates on the upper plate A1. When the heat input to the upper plate A1 concentrates, the molten metal rises and the welding current Iw rises sharply. Metal bulges can be detected.
The average output current is, for example, a moving average value of current values for N pulse cycles. For the average output current, for example, a moving average value of current values for N pulse cycles may be calculated. The adjustment circuit 25 calculates the difference between the average value of the welding current Iw calculated from the current values for the last N pulse cycles and the average value of the welding current Iw calculated from the current values for the previous N pulse cycles. By doing so, the amount of change in the output current is calculated. Then, when the average output current increases more than the threshold obtained by multiplying the set current value by the rate of increase, the adjustment circuit 25 determines that the average output current has suddenly increased. That is, when the amount of change in the average output current is positive and the absolute value of the amount of change is greater than the absolute value of the threshold, the adjustment circuit 25 determines that the average output current has risen sharply.

When determining that the average output current has decreased rapidly (step S13: YES), the adjustment circuit 25 decreases the current command value by a predetermined amount (step S14). The adjustment circuit 25 reduces the welding current Iw by 5A, for example.

Next, the adjustment circuit 25 detects the welding current Iw (step S15) and determines whether or not the average output current has recovered to the state before the sharp rise (step S16). If it is determined that the average output current has not recovered (step S16: NO), the adjustment circuit 25 returns the process to step S14 and continues the process of decreasing the current command value. The adjustment circuit 25 reduces the current command value by, for example, 5 A/0.1 ms.

When it is determined that the average output current has recovered (step S16: YES), or when it is determined in step S13 that the average output current has not suddenly increased (step S13: NO), the adjustment circuit 25 adjusts the current command value. It is determined whether or not reduction control is in progress (step S17). That is, the adjustment circuit 25 determines whether or not the current command value is decreased in the process of step S14.
If it is determined that the control to decrease the current command value is not being performed (step S17: NO), the adjustment circuit 25 ends the process. If it is determined that the welding current Iw is being controlled to decrease (step S17: YES), the adjustment circuit 25 determines whether or not the welding current Iw has decreased (step S18). That is, the adjustment circuit 25 determines whether or not the swelling of the molten metal has disappeared. When determining that the welding current Iw has not decreased (step S18: NO), the adjustment circuit 25 returns the process to step S12. When determining that the welding current Iw is decreasing (step S18: YES), the adjustment circuit 25 increases the current command value by a predetermined amount (step S19), and returns the process to step S12. For example, the adjustment circuit 25 increases the current command value by 5A. The adjustment circuit 25 increases the current command value by, for example, 5 A/0.1 ms.

In the process of gradually returning the welding current Iw to the original current command value, if the average output current does not decrease rapidly, that is, if the molten metal does not swell due to the displacement of the welding wire W to the upper plate A1, a little The current command value is returned to the original value one by one.

(Example)
An example will be described. Projection length 20 mm, target angle 45 degrees, forward angle 0 degrees, target position +3.0 mm (upper plate A1 side), set current 440 A, set voltage 32.5 V, welding speed 150 cm / min, plate thickness 3.2 mm × Make a 3.2 mm lap fillet weld. After the start transition period, when the average output current for 3 pulses has increased by 10A or more from the previous 3 cycles, it is judged that the molten metal has started to swell due to burn-through of the upper plate A1, and the average output current for 3 pulses is The current command value is decreased at a rate of 5 degrees/0.1 ms until the pulse output current for 3 cycles before the determination of the swelling of the molten metal is reached.
By adjusting the current command value in this way, it is possible to effectively prevent the molten metal from rising.

According to the welding apparatus and the lap fillet welding method according to the present embodiment, in downward lap fillet welding, the occurrence of humping beads that can occur when the target position of the welding wire W is shifted toward the upper plate A1 side is suppressed. can do.

Further, by decreasing the current command value stepwise, it is possible to more stably suppress the swelling of the molten metal and the occurrence of humping beads.
Furthermore, when the welding current Iw is stabilized, the current command value is decreased stepwise, thereby avoiding sudden changes in the welding conditions and achieving more stable lap fillet welding.

Furthermore, since the swell of the molten metal is detected using a threshold corresponding to the set current value, the current command value can be controlled more accurately, and the occurrence of humping beads can be suppressed.

In the case of high-speed welding where the problem of humping beads is likely to occur due to the target position of the welding wire W being shifted toward the upper plate A1 side, for example, lap fillet welding of thin plates at a welding speed of 100 cm/min to 120 cm/min. Even if there is, the process of the present embodiment can effectively suppress the humping bead.

In this embodiment, when the average output current suddenly rises, the control for decreasing the current command value is exemplified, but the welding speed may be decreased.

Also, in the present embodiment, the case where the rate of change is the same when the current command value is decreased and when it is increased has been described, but the current command value may be increased at a faster speed.

Furthermore, the welding device capable of performing the lap fillet welding method according to the present embodiment is not limited to a pulse welder, and can be applied to any consumable electrode type welding device.

Furthermore, in this embodiment, an example in which the welding power source 2 is provided with the adjustment circuit 25 has been described, but the adjustment circuit 25 may be provided in the control device 3 .

1: Welding robot 2: Welding power source 3: Control device 11: Welding torch 12: Wire feeding unit 21: Power supply circuit 22: Detecting unit 22a: Voltage detecting circuit 22b: Current detecting circuit 23: power supply control circuit, 24: feed control circuit, 25: adjustment circuit, 25a: processing unit, 25b: input unit, 25c: output unit, 25d: storage unit, 25e: computer program, 25f: table, A1: top Plate, A2: Lower plate, Vw: Welding voltage, Iw: Welding current, Vd: Voltage detection signal, Id: Current detection signal, ΔI: Differential amplification signal, Irc: Current command signal, W: Welding wire

Claims (5)

A lap fillet welding method for arc welding by feeding a welding wire to a corner of a first base material and a second base material that are overlapped,
detect the welding current,
Determining whether or not there is an increase in the welding current due to the swelling of the molten metal at the corner,
A lap fillet welding method for decreasing a current command value for controlling the welding current when it is determined that the welding current has increased. stepwise decreasing the current command value from the current command value based on the set current until the welding current returns to the state before the increase;
The lap fillet welding method according to claim 1, wherein when the welding current returns to the state before the increase, the current command value is increased stepwise to the current command value based on the set current. Preparing a table that associates a welding current set value with a rate of increase in the welding current due to the rise of the molten metal at the corner,
Identify the rate of increase by referring to the table based on the set value of the welding current,
The lap fillet welding method according to claim 1 or 2, wherein the current command value is decreased when it is determined that the detected welding current is rising from the specified rate of increase. The lap fillet welding method according to any one of claims 1 to 3, wherein the welding speed is 100 cm/min or more. A welding device for arc welding by feeding a welding wire to a corner of a first base material and a second base material that are overlapped,
a current detection circuit that detects a welding current;
a power supply circuit that outputs a welding current;
and an adjustment circuit that determines whether or not the welding current has increased due to the buildup of the molten metal at the corner, and decreases a current command value for controlling the welding current when it is determined that the welding current has increased. .

Images