JP2005144458A - Welding method and welding equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding method and welding equipment capable of allowing a welding torch to correctly follow a weld line in the butt welding to form a weld bead by advancing/retracting the welding torch in the direction of the weld line direction while weaving the welding torch in a direction substantially orthogonal to the weld line. <P>SOLUTION: In a butt arc welding method to form a welding bead by advancing/retracting a welding torch 2 in the direction of the weld line while weaving the welding torch in a direction substantially orthogonal to the weld line, the integrated welding current value and the integrated welding voltage value are compared with each other on the right and left sides with a weaving center C as a boundary during the equal phase period from the weaving center C of the period in which welding arcs 20a and 20b are generated between the welding torch 2 and groove surfaces of base metals 8a and 8b, and the weaving center of the welding torch 2 is moved in the direction in which the difference between the welding current values and the difference between the welding voltage values on the right and left sides are reduced. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a welding method and welding apparatus for butt arc welding in which a welding bead is formed by weaving a welding torch in a direction substantially perpendicular to a welding line to advance and retreat in the welding line direction.

  In general, for welding line tracking when performing automatic arc welding, the welding torch is weaved in a direction substantially perpendicular to the welding line, and the weaving center position of the welding torch is based on the electrical changes accompanying changes in the arc length and protrusion length. The method of controlling is widely adopted. In this method, the welding currents obtained on the left and right sides are compared with the weaving center as a boundary, and the welding torch weaving center is moved in a direction in which the integrated value of the welding currents on the left and right sides is reduced based on the comparison signal. Thus, the welding torch can follow the weld line (see, for example, Patent Document 1).

Japanese Patent Publication No.53-11502

  In recent years, using a backing material even for butt joints with a root gap by weaving a welding torch in a direction substantially perpendicular to the weld line and following the weld line while repeatedly advancing and retreating in the weld line direction A technology to form a good back bead has been developed.

  However, in this technique, since the weld bead is formed while the welding torch is advanced and retracted in the direction of the weld line, when the weld metal is superimposed on the portion where the initial layer of the weld bead has already been formed, the arc is generated by the welding torch. May occur between the welding torch and the molten pool, not between the groove and the groove surface of the base metal. Therefore, when the welding line tracking control described in Patent Document 1 is applied to this technique, the weaving center depends on the state of the molten pool during the period in which the arc is generated between the welding torch and the molten pool surface. The arc length on both the left and right sides of the boundary may fluctuate, and accurate welding line tracking may not be performed.

  The present invention has been made in view of the above-mentioned matters, and the object thereof is butt welding in which a welding bead is formed by advancing and retreating in the welding line direction while weaving the welding torch in a direction substantially perpendicular to the welding line. An object of the present invention is to provide a welding method and a welding apparatus that can cause a welding torch to accurately follow a weld line.

  In order to achieve the above object, a first invention provides a welding method for butt arc welding in which a welding bead is formed by advancing and retreating in a welding line direction while weaving the welding torch in a direction substantially perpendicular to the welding line. The welding current value and welding voltage value integration values on both the left and right sides of the weaving center in the same phase period from the weaving center during the period in which the welding arc occurs between the groove and the base metal groove surface are compared. The weaving center of the welding torch is moved in the direction in which the difference between the welding current value and the welding voltage value on both the left and right sides becomes smaller.

  Further, according to a second aspect of the present invention, in the first aspect, during the period in which a welding arc is generated between the welding torch and the groove surface of the base material, the operation of the welding torch in the welding line direction is advanced. It is characterized by the number of weaving cycles immediately before switching to the reverse.

  In a third aspect based on the first aspect, the welding torch is advanced in the weld line direction during a period in which a welding arc is generated between the welding torch and the groove surface of the base material. Immediately after the difference between the average value of the welding voltage for one period of weaving and the average value of the welding voltage for one period of weaving immediately before exceeds the set threshold, the operation of the welding torch moves backward from forward. It is a period until it switches to.

  The fourth invention is a butt arc welding welding apparatus in which a welding bead is formed by advancing and retreating in the welding line direction while weaving the welding torch in a direction substantially perpendicular to the welding line, and a welding torch in which an electrode wire is inserted; It is equal from the center of the weaving during the period in which the welding arc is generated between the welding torch and the groove surface of the base metal, and the welding robot for moving the welding torch in the direction of the welding line while weaving the welding torch substantially perpendicularly to the welding line Compare the welding current value and the integrated value of the welding voltage value on the left and right sides with the weaving center in the phase period as the boundary, and the welding torch in the direction in which the difference between the welding current value and the welding voltage value on the left and right sides becomes smaller And a controller for controlling the welding robot to move the weaving center.

  According to the present invention, even when performing butt arc welding to form a weld bead while repeatedly advancing and retreating in the weld line direction while weaving in the direction perpendicular to the weld line, it becomes possible to follow the appropriate weld line, High quality welding with a good back bead can be performed.

Hereinafter, an embodiment of a welding method and a welding apparatus of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing the overall configuration of an embodiment of a welding apparatus of the present invention, and FIG. 2 is an operation diagram of a welding torch.
1 and 2, 1 is a welding robot (manipulator) having an articulated arm 1 a, 2 is a welding torch provided at the tip of the arm 1 a of the welding robot 1, and 3 is an electrode wire inserted through the welding torch 2. It is. As shown in FIG. 2, the welding robot 1 can advance and retract in the weld line direction while weaving the welding torch 2 in a direction substantially perpendicular to the weld line (see arrow 26 in FIG. 2) (in FIG. 2). Arrow 25).

  4 is a tube for guiding the electrode wire 3 to the welding torch 2, and 5 is a wire feeding device for sequentially feeding the electrode wire 3 wound around the reel 6 to the welding torch 2. Although not particularly shown, the welding torch 2 is provided with a gas nozzle for injecting a shielding gas. 7 is a power supply device for supplying power (current, voltage) to the electrode wire 3 and the like. The positive terminal 7a of the power supply device 7 is the electrode wire 3 (strictly, the tube 4), and the negative terminal 7b is a butt to be welded. Each is connected to the joint 8. Further, an output terminal (not shown) of the power supply device 7 is connected to the wire feeding device 5, and the electrode wire 3 is controlled by the magnitude of a command signal (power) supplied from the power supply device 7 to the wire feeding device 5. The feeding speed is adjusted.

  Reference numeral 9 denotes a robot control panel. The robot control panel 9 includes a control device 10 for calculating command signals for the welding robot 1 and the power supply device 7, and the command signals calculated by the control device 10 for the welding robot 1 and the power supply device. 7 includes a robot driver 11 and a power supply driver 12 that output the signals respectively. Reference numeral 13 denotes a gap sensor that detects a route gap or a misinterpretation between the butt joints 8 and outputs the detected gap to the control device 10. This gap sensor 13 is located near the welding torch 2 (see FIG. 1) at the tip of the arm 1a of the welding robot 1. It is provided on the front side in the welding line direction indicated by an arrow. As the gap sensor 13, for example, a known laser sensor or ultrasonic sensor is used.

FIG. 3 is a block diagram illustrating a schematic configuration of the control device 10.
In FIG. 3, reference numeral 14 denotes an A / D converter that is a signal input unit, and the detection signal from the gap sensor 13 and the electrode wire 3 by the power supply device 7 are supplied via the A / D converter 14. The value of electric power (current / voltage) is input to the control device 10 and converted into a digital signal. Reference numeral 15 denotes a read only memory (ROM) that stores a program of a predetermined control procedure and constants necessary for control. This ROM 15 is obtained experimentally (or theoretically) in advance according to the root gap of the butt joint 8. A welding condition table in which combination patterns of the welding conditions (applied power of electrode wire 3, feeding speed, weaving condition, welding speed) are collected is stored.

  16 is a timer for measuring time, and 17 is a central processing unit (CPU) that calculates predetermined command signals for the welding robot 1 and the power supply device 7 in accordance with the welding conditions selected from the programs stored in the ROM 15 and the welding condition table. It is. Reference numeral 18 denotes a random access memory (RAM) that temporarily stores calculation results of the CPU 17 and numerical values during the calculation. Reference numeral 19 converts an instruction signal calculated by the CPU 17 into an analog signal, and the corresponding driver (the robot driver 11, the power supply). It is a D / A converter that outputs to the driver 12).

  With such a configuration, when the welding start point and end point are input, the control device 10 sequentially updates the welding conditions based on the detection signal from the gap sensor 13 based on the instruction to start welding, and the welding robot. 1 and the power supply device 7 are controlled.

  When the welding robot 1 receives a command signal from the control device 10 that is output via the robot driver 11, the welding robot 1 has a weaving condition and a moving speed (welding speed) according to the command signal as shown in FIG. 2 is repeatedly switched back in the weld line direction while weaving 2 in the direction perpendicular to the weld line. At this time, one cycle of the switchback operation of the welding torch 2 consisting of advancement and retreat in the weld line direction is first performed at the path a in the advance direction in which the first layer welding is performed on the groove, and then turned back at the turn-back point d. The path b in the backward direction in which the second-layer weld bead is superimposed and the path c in the forward direction in which the third-layer weld bead is superimposed at the folding point e.

  On the other hand, when the power supply device 7 receives a command signal from the control device 10 output via the power supply driver 12, the power supply device 7 applies a voltage / current corresponding to the command value to the electrode wire 3. The current applied to the electrode wire 3 flows in the order of the plus terminal 7 a of the power supply device 7 → the electrode wire 3 → the butt joint 8 → the minus terminal 7 b of the power supply device 7. As a result, an arc 20 is generated from the tip of the electrode wire 3 to the welded portion of the butt joint 8, and the arc heat melts the tip of the electrode wire 3 and the welded portion of the butt joint 8. A weld bead (molten metal) is deposited on the surface. As the electrode wire 3 is consumed (melted), the power supply device 7 outputs a wire feeding signal (voltage) having a magnitude corresponding to the command signal from the control device 10 to the wire feeding device 5, and the wire The electrode wire 3 is sequentially fed to the welding torch 2 by controlling the driving speed of the feeding device 5.

Here, the concept of the welding line tracking control in one embodiment of the welding method of the present invention will be described.
FIG. 4 is a diagram showing a state near a welding point when an arc is generated as viewed from the front of the welding line, and FIG. 5 is a graph showing changes in current and voltage when the arc is generated.
In general, when using arc power data for copying a welding line, the weaving center C is controlled in the groove width direction so that the integrated values of the current and voltage on both the left and right sides of the weaving center C are equal in each weaving cycle. Is done. In the case of welding in which the welding torch is moved in one direction (that is, only forward), since the molten pool 21 exists behind the left and right arcs 20a and 20b, the arcs 20a and 20b are shown in FIG. Thus, it occurs between the groove surfaces of the base materials 8 a and 8 b and the electrode wire 3. Here, for convenience, the electrode wire 3 when positioned at the weaving left end L is denoted by reference symbol 3a, and the electrode wire 3 when positioned at the weaving right end R is denoted by reference symbol 3b. Therefore, the measured welding current and welding voltage values are between the electrode wire 3a and the groove surface of the base material 8a at the weaving left end L, and at the weaving right end R, the groove surface of the electrode wire 3b and the base material 8b. When the weaving center C coincides with the gap center between the two base materials 8a and 8b, the current value and voltage value are approximately shown in FIGS. 5 (a) and 5 (b), respectively. The waveform is as shown.

  On the other hand, as shown in FIG. 4B, when the weaving center C is shifted to the right side from the gap center of the base materials 8a and 8b, the distance between the electrode wire 3a and the groove surface of the base material 8a at the left end L of the weaving. Is longer than the distance (arc length) between the electrode wire 3b and the groove surface of the base material 8b at the right end R of the weaving, the current value and the voltage value thereof are approximately shown in FIG. (C) A waveform as shown in FIG.

  As shown in FIGS. 5A to 5D, the weaving center C is controlled in such a manner that the current and voltage on both sides with the weaving center C as a boundary are in the same phase Δt with respect to the weaving center C. (Period of Δt after ts has passed since passing through the weaving center) Integration is performed by moving the weaving center C in a direction in which the difference between the integrated values on the left and right of the weaving decreases. For example, when the weaving center C deviates to the right side from the gap center as shown in FIG. 4B, the integrated value of the current is on the right side of the weaving center C as shown in FIGS. 5C and 5D. The integrated value of the voltage is large on the left side of the weaving center C. Therefore, the weaving center C is controlled in a direction (in this case, the left side) to reduce the difference between the integral values on the left and right sides. Accordingly, as shown in FIG. 4B, when the weaving center C does not coincide with the gap center, the weaving center C is controlled to the gap center position that is equidistant from the groove surfaces of both the base materials 8a and 8b.

  On the other hand, as shown in FIG. 2, in the case of repeated advancement and retreat in the welding line direction, a portion that has already been welded during retreat (path b movement) and part of advance (path c movement). Since it passes through (on the molten pool), the arcs 20a and 20b may be generated between the electrode wires 3a and 3b and the molten pool 21, respectively, as shown in FIG. In this case, the measured welding current and welding voltage value are between the electrode wire 3a and the molten pool 21 at the weaving left end L, and between the electrode wire 3b and the molten pool 21 at the weaving right end R. Therefore, when the height of the surface of the molten pool 21 becomes nonuniform in the width direction for some reason, the lengths of the arcs 20a and 20b may change regardless of the position of the weaving center C. For example, as shown in FIG. 4D, when the molten pool 21 is formed to rise to the right in the width direction, it is measured even if the gap center between the base materials 8a and 8b and the weaving center C coincide. The welding current and welding voltage value generally have waveforms as shown in FIGS. 5 (c) and 5 (d), respectively. Therefore, in the case of FIG. 4D, the current and voltage on both sides with the weaving center C as a boundary are integrated with respect to the weaving center for a period Δt (the period of Δt after passing ts after passing the weaving center C), When the weaving center C is controlled in a direction in which the difference between the integral values on the left and right of the weaving becomes smaller, control is performed to bother the weaving center C that coincides with the gap center.

  Therefore, in the switchback welding that repeatedly advances and retreats in the weld line direction as in the present invention, as shown in FIG. 4A, the arcs 20a and 20b are connected to the electrode wires 3a and 3b and the groove surfaces of the base materials 8a and 8b. By using only the welding current value and welding voltage value of the weaving period during movement of the path a during the movement of the weaving center C, it is possible to control the weaving center C to the gap center. . As a period in which the arcs 20a and 20b are generated between the electrode wires 3a and 3b and the groove surfaces of the base materials 8a and 8b, the period for measuring the current value and the voltage value for controlling the weaving center C in the present invention is as follows. For example, the number of weaving cycles (before reaching the turn-around point d) immediately before the welding torch 2 switches from forward to backward (hereinafter referred to as “first period”), or on the molten pool during forward movement From immediately after the arc 20 generated from the groove surface is generated from the groove surface (boundary point with one cycle of the previous switchback, that is, the start point of one cycle), until it switches from forward to backward (to the turning point d) (This period is hereinafter referred to as “second period”) and the like.

  Regarding the acquisition start time of the welding current value and the welding voltage value, for the first period, a time at which the welding torch 2 passes the turning point d is determined from preset welding conditions, and the weaving a The time before the cycle (a = integer, set value), and for the second period, the arc voltage rises at the moment when the arc generation point shifts from the molten pool to the groove surface. The average value of the voltage for one period of weaving is calculated, and the time when the difference between the average value and the average voltage value of the previous period becomes equal to or greater than the set threshold value is set. As a result, it is possible to acquire a welding current value and a welding voltage value when an arc is generated from the groove surface, enable accurate follow-up of the weld line, and obtain a high-quality weld bead.

FIG. 6 is a flowchart of a control procedure by a program stored in the control device 10 described above. The control device 10 having the above-described configuration is configured to connect the welding robot 1, the wire feeding device 5, and the power supply device 7 based on the flow of FIG. Control.
First, in step 100, the control device 10 inputs a welding start point and an end point set by the operator from a setting unit (not shown) provided on the robot control panel 9 (or provided separately). The input welding start / end points are converted into digital signals via the A / D converter 14 and stored in the RAM 18.

  Moving to step 101, the detection signal of the root gap and the misalignment amount of the butt joint 8 from the gap sensor 13 is input via the A / D converter 14, converted into a digital signal, and stored in the RAM 18. Transition.

  In step 102, based on the detection signal input in step 101 by the CPU 17, an appropriate welding condition (applied power, feeding speed, welding speed of the electrode wire 3) is selected from the welding condition table stored in the ROM 15. Are selected (set) and stored in the RAM 18 (n = 1). And CPU17 calculates the command signal for performing welding on the set welding conditions, and outputs it to the welding robot 1 and the power supply device 7 via the robot driver 11 and the power supply driver 12, respectively. The welding robot 1 is instructed to move the welding torch 2 (welding speed) and the weaving condition, and the power supply device 7 is instructed to feed the electrode wire 3 and supply power (current / voltage).

  Subsequently, in step 103, during the weaving welding, the measured value of the current / voltage applied to the electrode wire 3 from the power supply device 7 is input, converted into a digital signal via the A / D converter 14, and stored in the RAM 18, Move on to step 104.

  In step 104, it is determined whether or not the time measured by the timer 16 (current time) has reached the weaving period (for one period). If the determination is not satisfied, the process returns to step 103 to continue the current / voltage measurement. Enter a value. If the current time reaches the weaving cycle and the determination in step 104 is satisfied, the procedure proceeds to step 105.

  In step 105, it is determined whether the correction output trigger signal at the center of the weaving stored in the RAM 18 is ON / OFF. If ON, the process proceeds to step 108. If OFF, the process proceeds to step 106.

In step 106, first determines the difference ΔV of one weaving cycle of the average voltage value Vave and (m) and the preceding one weaving cycle of the average voltage value Vave (m-1) is, whether the threshold value greater than or equal _to V ₀ is Is done. At the same time, the current time is t, and after the start of welding, the time when the number of times the operation of the welding torch 2 switches from forward (when moving the path a) to backward (when moving the path b) is n is tc (n), Whether the current time has reached a time (tc (n) −aT) a period before the time (turning point d arrival time) when the weaving cycle is T and a is a constant and the time is switched from forward to backward (turn-around point d arrival time). Determined. If any one of these determinations is satisfied, the routine proceeds to step 107, where the correction output trigger signal ON is stored in the RAM 18, and the routine proceeds to step 108. If neither determination is satisfied, the procedure returns to step 103.
Note that the determination in step 106 may not be the case where one of the two determination criteria is satisfied (OR condition) as described above, but may be the case where both are satisfied (AND condition). Further, only one of the determination criteria may be used without using the two determination criteria.

  In step 108, it is determined whether or not the current time t has reached a time tc (n) at which the current time t switches from forward to backward. If the determination in step 108 is satisfied, the procedure proceeds to step 109, and the CPU 17 designates the specified period Δt (see FIG. 5) in the predetermined period (the first period or the second period described above) stored in the RAM 18. ) Is integrated on both the left and right sides of the weaving center. Then, the left and right integral values are compared, a correction value for moving the weaving center so as to reduce the difference between the two is stored in the RAM 18, and the stored correction value is passed through the D / A converter 19. The analog signal is output to the welding robot 1 via the robot driver 11. Thereby, the weaving center position of the electrode wire 3 is corrected to an appropriate position substantially coincident with the gap center position of the base materials 8a and 8b.

  On the other hand, if the current time has passed the nth forward-to-reverse switching time (tc (n)) and the determination in step 108 is not satisfied, the procedure proceeds to step 110 and the RAM 18 receives the correction output trigger signal. Is stored, the time that is the criterion in step 109 is changed from tc (n) to tc (n + 1), the process returns to step 103, and the subsequent procedures are repeated.

  When the weaving center is corrected in the previous step 109, the process proceeds to step 111, and it is determined whether or not the welding torch 2 has reached the welding end point. If the determination is not satisfied, the procedure returns to Step 101, the procedure from the input of the root gap and the mistake is performed, new welding conditions are set at Step 102, and the procedure after Step 103 is repeated. On the other hand, when the welding end point is reached and the determination in step 111 is satisfied, the command signal for the welding robot 1 and the power supply device 7 is turned off and the control procedure of FIG. 6 is ended.

  By executing such a procedure, the weaving center C of the welding torch 2 is controlled to substantially coincide with the gap center position of the base materials 8a and 8b during the first period or the second period described above. The

  In the control procedure of FIG. 6, as a result, the weaving center position is controlled for each weaving cycle during the first period or the second period described above. However, the present invention is not limited to this. Rather than controlling the weaving center for each period, the integrated value of the voltage value and current value during the first period or the second period is accumulated, and the voltage value and current value on both the left and right sides of the weaving center as a boundary. It is also possible to compare the accumulated integral values and move the weaving center position in a direction in which the difference decreases. In this case, the weaving center position is actually corrected by, for example, 1 of the switchback operation such as when the turn-around point d passes or when one cycle of the switchback operation starts (when switching from the path c to the path a). It may be performed at an appropriate timing during the cycle.

  As described above, according to the present embodiment, the acquisition period of the welding current value and the welding voltage value used for welding line tracking is limited to the period in which the arc is generated from the groove surfaces of the base materials 8a and 8b. Thus, the welding current value and the welding voltage value between the tip of the electrode wire 3 and the groove surfaces of the base materials 8a and 8b can be obtained. This enables the welding torch to follow an appropriate welding line even when performing a butt arc welding method in which a welding bead is formed while repeatedly advancing and retreating in the welding line direction while weaving in a direction perpendicular to the welding line. High quality welding with good back bead can be performed.

  In the above description, the example in which the detection data of the route gap between the base materials 8a and 8b is input to the control device 10 online by the gap detection sensor 13 is not limited to this. It is good also as a structure which measures and inputs it in advance. Moreover, although the case where arc welding was performed using only the electrode wire 3 was taken as an example, for example, the present invention can also be applied to a so-called double wire type welding apparatus provided with a filler wire in addition to the electrode wire 3. In FIG. 1, the wire feeding device 5 is described as a so-called push type provided on the reel 6 side. However, a so-called pull type provided on the welding torch 2 side may be combined. Absent. In these cases, the same effect as described above can be obtained.

It is the schematic showing the whole structure of one Embodiment of the welding apparatus of this invention. It is an operation | movement figure of the welding torch with which the welding apparatus of this invention was equipped. It is a block diagram showing schematic structure of the control apparatus with which one Embodiment of the welding apparatus of this invention was equipped. It is a figure showing the mode of the welding point vicinity at the time of the arc generation seen from the welding line front. It is a graph showing the change of the electric current at the time of arc generation, and a voltage. It is a flowchart showing the control procedure by the control apparatus with which one Embodiment of the welding apparatus of this invention was equipped.

Explanation of symbols

1 Welding Robot 2 Welding Torch 3 Electrode Wire 10 Controller C Weaving Center

Claims (4)

In a welding method of butt arc welding in which a welding bead is formed by advancing and retreating in the welding line direction while weaving the welding torch substantially perpendicular to the welding line,
The integrated value of the welding current value and the welding voltage value on both the left and right sides of the weaving center in the same phase period from the weaving center during the period in which the welding arc is generated between the welding torch and the groove surface of the base metal. A welding method characterized by comparing each of them and moving the weaving center of the welding torch in a direction in which the difference between the welding current value and the welding voltage value on both the left and right sides becomes smaller.   The period in which the welding arc is generated between the welding torch and the groove surface of the base metal is the number of weaving cycles immediately before the operation of the welding torch in the welding line direction is switched from forward to backward. The welding method according to claim 1.   The period during which the welding arc is generated between the welding torch and the groove surface of the base metal is the average value of the welding voltage for one period of weaving when the welding torch is advanced in the welding line direction, and immediately before that. A period from immediately after the difference from the average value of the welding voltage for one period of weaving exceeds a set threshold value until the operation of the welding torch switches from forward to backward. The welding method according to 1. In a welding apparatus for butt arc welding in which a welding bead is formed by advancing and retreating in the welding line direction while weaving the welding torch substantially perpendicular to the welding line,
A welding torch inserted through an electrode wire;
A welding robot that advances and retreats in the welding line direction while weaving the welding torch substantially perpendicular to the welding line;
The integrated value of the welding current value and the welding voltage value on both the left and right sides of the weaving center in the same phase period from the weaving center during the period in which the welding arc is generated between the welding torch and the groove surface of the base metal. And a control device for controlling the welding robot so as to move the weaving center of the welding torch in a direction in which the difference between the welding current value and the welding voltage value on both the left and right sides becomes smaller. Welding equipment to do.

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