JPH0839253A - How to detect the position of the welding wire - Google Patents

Abstract

(57) [Summary] [Structure] Means 13 for detecting the wire voltage signal Vw generated between the non-energized welding wire 8 sent into the arc 6 and the welding base metal 27, and detecting the transition of the welding wire short circuit. By providing the means 14 and the welding wire position discriminating means 15, the number of short circuit transitions per unit time and the short circuit transition time ratio obtained by the wire short circuit detecting means 14 are taken into the wire position discriminating means during the welding period. Whether the position height is proper or not is discriminated, and when the height is too high, the height is lowered, and when the height is too small, a control signal for raising the height is transmitted. [Effect] It is possible to judge the quality of the welding wire position and the abnormality of the electrode related to the quality of the weld bead shape, and to prevent the occurrence of welding defects, so that the welding can be automated and the welding quality can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of performing an automatic welding by generating an arc in a welding torch using a non-consumable electrode and feeding a welding wire into the arc.
The present invention relates to a detection method suitable for determining the quality of a position of a wire melted in an arc and determining an abnormality of an electrode.

[0002]

2. Description of the Related Art Generally, TIG arc welding or plasma arc welding is known as a welding method using a non-consumable electrode whose main component is dangsten. In these arc welding, in contrast to welding of a joint base metal with a groove or mere overlay welding of the base metal surface, the welding wire (in the arc generated between the electrode of the welding torch and the welding base metal) Welding is performed while feeding and melting a filler material or wire). However, the position of this welding wire fed into the arc is not always constant, and is extremely affected by the effects of thermal deformation of the welding base metal, changes in the arc length, bending of the wire, etc. in addition to the wire feed speed. It is easy to change. Therefore, there is a problem that the molten state of the wire is likely to be unstable, the welding bead is disturbed, and the welding result is deteriorated. Also, in TIG welding where the electrode is exposed, if the welding wire comes too close to the electrode and comes into contact with it during welding, the electrode will be significantly damaged and the arc will be disturbed. There is a problem that the molten pool is disturbed or adhered to cause welding troubles and welding defects. These problems are major obstacles to automation of welding and improvement of welding quality.

In order to solve such a problem, several methods have been tried in the past. For example, Japanese Patent Publication Sho 53
As disclosed in the arc automatic welding method of -4817, the guide tip (wire guide) of the filler metal is pressed into contact with the welding base metal to make the gap between the filler metal and the welding base metal constant. Hold on.

On the other hand, a method of detecting the arc voltage (welding voltage) and performing feedback control is conventionally known as a method of keeping the arc length constant although the purpose of use is different. Further, in hot wire TIG welding in which the welding wire fed into the arc is energized and heated, a means for preventing the disturbance of the arc due to the energization of the wire has been proposed in addition to the control of the arc length. For example, in Japanese Patent Publication No. 5-75511,
An apparatus is disclosed in which a pulse current is used to energize a wire, a wire terminal voltage is detected during a period when the wire is not energized, and the next pulse current is prohibited when the wire and the base material are not in contact with each other.

[0005]

In order to obtain a stable welding transition of the welding wire fed into the arc, obtain a good welding result of the welding bead shape, and prevent abnormal wear of the electrode, it is necessary to judge whether the wire position is good or bad. Therefore, it is necessary to perform appropriate position control and electrode abnormality determination.

However, for example, the automatic arc welding method disclosed in Japanese Patent Publication No. 53-4817 is capable of keeping the height of the welding wire constant regardless of the variation of the arc length. Since the guide tip (wire guide) of) is pressed against the welding base metal, it cannot be applied to welding in which the welding torch is oscillated to the left or right (weaving) or multilayer multi-pass welding with uneven bead shape. Not
There is a drawback that the surface of the base material of the contact portion and the guide tip are easily damaged.

On the other hand, the method of detecting the arc voltage and performing the feedback control is effective for the constant control of the arc length, but the position of the welding wire fed into the arc is
It is in a completely uncontrolled state, and the occurrence of the above-mentioned welding wire trouble cannot be eliminated. Further, for example, the hot wire TIG disclosed in Japanese Patent Publication No. 5-75511.
Welding equipment is effective in preventing arc disturbance due to wire energization, but it is ineffective for ordinary welding in which the welding wire is not energized and the height control of the wire position is not performed at all. Since it does not exist, the molten state of the welding wire cannot be managed and controlled. Moreover, none of the electrode abnormality determinations is described.

The object of the present invention is to determine whether the wire position is good or bad in order to obtain a stable welding transition of the welding wire fed into the arc, obtain a good welding bead shape, and prevent abnormal wear of the electrode. An object of the present invention is to provide a detection method suitable for making a control command and determining an abnormality of an electrode.

[0009]

SUMMARY OF THE INVENTION According to the present invention, an arc having an arbitrary output waveform is generated by applying an electric current between a base material of a welded joint and a non-consumable electrode at a tip of a welding torch, and in the arc and in a molten pool. A wire voltage detecting means for detecting a wire voltage signal Vw generated between the non-energized welding wire and the welding base material by a method of detecting a welding wire position when performing welding while feeding a non-energized welding wire into the inside; Wire short-circuit detection means for determining the number of short-circuit transitions N per unit time and the short-circuit transition time ratio At when the welding wire undergoes a short-circuit transition, and a wire position for determining the welding wire position by incorporating the number of short-circuit transitions and the short-circuit transition time ratio. Each of the determining means is provided, and after the wire position determining means determines whether the welding wire position height is proper or not during the welding period after the arc is generated,
When it is determined that the height of the welding wire is too large and inappropriate, a control signal that lowers the height is generated. Conversely, when it is determined that the height of the welding wire is too small and inappropriate, the height is increased. And a control signal for transmitting the control signal, and electrode voltage detection means for detecting an electrode voltage signal Ve generated between the non-conducting welding wire and the non-consumable electrode, and welding with the electrode through which a welding current flows. A welding voltage detecting means for detecting a welding voltage signal Ea generated between the base material and an abnormality judging means for judging an abnormality of the electrode and the welding wire are provided respectively, and at the same time as the operation of the wire position judging means or at the wire position. After transmitting the height control signal, the electrode voltage signal Ve and the welding voltage signal Ea are taken into the abnormality determining means, and a reference voltage value e for abnormality determination is obtained.
2, the electrode voltage signal Ve is Ve ≦ e2, it is determined that the droplet of the welding wire has contacted the electrode, and the welding voltage signal Ea is compared with the reference voltage value e2 for abnormality determination.
When Ea ≦ e2, it is determined that the electrode has come into contact with the molten pool, and a welding stop command and an electrode abnormality display command are issued.

Further, another invention is a wire voltage signal Vw generated between the non-energized welding wire and the welding base material.
And a wire voltage detecting means for detecting the number N of short circuit transitions per unit time and a short circuit transition time ratio At when the welding wire makes a short circuit transition, and further the wire short circuit detecting means determines The number of short-circuit transitions and the short-circuit transition time ratio are taken in to determine whether the welding wire position is good or bad, and when it is determined that the height of the welding wire position is excessive, the control signal for lowering the height is set to the welding wire position. Is provided with wire position discriminating means for transmitting a control signal for raising the height of each of the electrodes, and an electrode voltage signal generated between the non-conducting welding wire and the non-consumable electrode. An electrode voltage detecting means for detecting Ve and a welding voltage detecting means for detecting a welding voltage signal Ea generated between the electrode through which the welding current flows and the welding base metal are provided. Simultaneously with the operation of the wire position discriminating means, or after transmitting a control signal of the wire position height, the electrode voltage signal Ve and the welding voltage signal Ea are taken into the abnormality discriminating means, and a reference voltage for abnormality judgment is obtained. For the value e2, the electrode voltage signal Ve is Ve ≦ e2
When the welding voltage signal Ea is Ea ≦ e2 with respect to the reference voltage value e2 for abnormality determination, it is determined that the electrode is in contact with the molten pool. The welding wire position detecting device is provided with an abnormality determining means to issue a welding stop instruction and an electrode abnormality display instruction. Further, the function of detecting the position of the welding wire is provided inside the welding control device so as to operate as an automatic welding system.

[0011]

As described above, the welding wire height is determined by providing the wire position discriminating means for discriminating the welding wire position from the number of short circuit transitions per unit time and the short circuit transition time ratio of the welding wire obtained by the wire short circuit detecting means. It is possible to discriminate between proper and improper. In this determination, when the short circuit transition time rate At is At <a (%), or the short circuit transition time rate At is At <a (%), and the short circuit transition number N is N <m (number / second). When the welding wire position height is too large, it is determined that the position is not appropriate. Conversely, when the short circuit transition time ratio At is greater than At> b, or the short circuit transition time ratio At is At> b and the number of short circuit transitions N is N. When <m, the welding wire position height is too small and it is determined that
Further, when a ≦ At ≦ b and N ≧ m, the welding wire position height is determined to be appropriate. Further, when it is determined from the determination result that the wire position height is inappropriate, the control signal is transmitted in the direction for correcting the wire position height, so that the wire position height can be appropriately controlled. Further, by providing an abnormality determining means for determining an abnormality of the electrode and the welding wire from the electrode voltage signal and the welding voltage signal, it is possible to detect when the welding wire being melted contacts the electrode or when the electrode contacts the molten pool. It can be clearly identified. Then, in such a case, since a welding stop command and an electrode abnormality display command are issued, at the same time as knowing a defect in the electrode or the welding wire,
It is possible to prevent deterioration of welding results and occurrence of welding defects.

Further, by using a welding control device and an automatic welding system provided with a function of detecting the position of the welding wire, it can be applied to various welding joints such as general welding structures, welding pipes, chemical plants and welding assembly of nuclear power plants. The pass welding or the multi-pass multi-pass welding can be carried out favorably, and the welding can be automated and the welding quality can be improved.

[0013]

EXAMPLES The contents of the present invention will be specifically described below with reference to examples. FIG. 1 shows an embodiment of the present invention, which is provided with the functions of judging the quality of a welding wire melted in an arc, controlling the position, and judging the abnormality of an electrode. The object to be welded to the base material 27 is, for example, an example of a welded joint of various pipes required for welding and assembling in a chemical plant or a nuclear power plant. Reference numeral 1 is a welding torch that uses a non-consumable electrode 2 containing tungsten as a main component, and is provided via a torch holder 3 on a torch drive shaft 4 that can be driven in the vertical direction. 6 is the base material 2 of the pipe 2 and the welding joint of the electrode 2 and the material to be welded
7 is an arc that is generated between the arc 7 and the welding power source 7
According to this, a current waveform of arbitrary magnitude such as a DC arc or a pulse arc is output. 8 is an arc 2 from a welding wire feeder (omitted) through a wire guide 9.
A welding wire sent inside is provided through a wire holder 10 on a wire drive shaft 20 installed on a torch vertical drive shaft 4 that can be driven in the vertical direction. This welding wire is not electrically heated. The base material 27 of the pipe welding joint is provided with a groove of arbitrary shape, and the arc 2
Is melted by heating and welded while the groove is filled with the molten metal of the welding wire 8. One-pass welding is performed for a thin plate with a shallow groove, and multi-pass multi-pass welding is performed for a thick plate with a deep groove.
Reference numeral 28 denotes a pipe traveling carriage that can travel on the traveling rail 12 installed along the welding line of the base material 27 of the pipe welding joint at an arbitrary set speed. A torch drive shaft 4 capable of simultaneous drive is mounted. 21 is a welding torch 1 and a welding wire 8
The left and right drive shafts of the torch are capable of controlling the horizontal movement and swing of the torch. Further, reference numeral 20 is a wire drive shaft capable of driving the welding wire 8 vertically and horizontally, and is provided on the torch horizontal drive shaft 21 so that the welding wire 8 can be aligned independently. ing. further,
Reference numeral 13 is a wire voltage detecting means for detecting a wire voltage signal Vw generated between the non-energized welding wire 8 and the base material 27 of the weld joint. Reference numeral 14 is a wire short-circuit detecting means for detecting a short-circuit transition of the welding wire 8. The wire voltage signal Vw from the wire voltage detecting means 13 is fetched and compared with a reference voltage e1 of the wire short-circuit, and then a short circuit per unit time of wire melting. The number of transitions and the short circuit transition time rate are detected and calculated. Further, reference numeral 15 is a welding wire position discriminating means for discriminating the position of the welding wire. The welding wire position discriminating means 15 discriminates the quality of the welding wire position from the number of short circuit transitions and the short circuit transition time ratio obtained by the wire short circuit detection means 14. When the welding wire position discriminating means 15 discriminates that the position height of the welding wire is too small or too large, a control signal for correcting the wire position height is transmitted to the welding controller 16. . The torch drive shaft 4 is driven and controlled by a control signal transmitted from the welding wire position determination circuit 15 to the welding controller 16. Further, 23 is an electrode voltage detecting means for detecting an electrode voltage signal 22 of a voltage Ve generated between the non-energized welding wire 8 sent in the arc 2 and the electrode 2 in which the arc 2 is generated, and 26 Is a welding voltage detecting means for detecting a welding voltage signal 25 of the voltage Ea generated between the electrode 2 in which the arc 2 is generated and the base material 5. Also,
Reference numeral 24 is an abnormality determining means for determining an abnormality of the welding wire and the electrode, which is an electrode voltage detecting means 23 and a welding voltage detecting means 26.
Electrode voltage signal Ve and welding voltage signal Ea transmitted from
Is compared with the reference voltage e2 for abnormality determination to determine the presence or absence of abnormality. Then, when the abnormality determination circuit 24 determines that there is an abnormality, a welding stop instruction and an electrode abnormality display instruction are transmitted to the welding controller 16. The welding controller 16 controls the traveling of the traveling carriage 28, the output control of the welding power source 7, the welding wire feeding, in addition to the drive control of the torch drive shaft 4, the torch left-right drive shaft 21, and the wire drive shaft 20. Each control circuit or control means capable of performing a series of control necessary for welding such as control of an apparatus (omitted) is stored (omitted). A storage device 17 stores the wire short circuit detection circuit 14, the welding wire position determination circuit 15, and the welding controller 16.

Next, the melting characteristic of the welding wire and the method of discriminating the wire position from this characteristic will be described. As shown in FIG. 2, when the non-energized welding wire 8 is sent into the arc 6 generated between the electrode 2 and the base material 5 of the material to be welded, the voltage Vw is generated between the welding wire 8 and the base material 5. As a result, the wire-base material voltage Vw changes depending on the state of melting and droplet transfer of the welding wire 8. For example, FIG. 3 is a typical waveform example of the wire-base metal voltage Vw observed when the arc length L or the wire-base metal distance is changed, and FIG. Short-circuit condition that remains in contact with the molten pool,
(B) shows a state in which droplets sometimes shift from a short circuit, (c) shows a state in which small droplets repeat short-circuiting in a short time, and (d) shows a state in which large grown droplets sometimes shift. . For the reference voltage e1 of wire short circuit,
The wire short circuit occurs at each time ts in the region where the inter-base material voltage Vw is Vw ≦ e1. Therefore, a voltage Vw between the wire and the base material, which causes a potential difference when the wire droplets are transferred
It is possible to determine the number N of short-circuiting transitions of the wire droplet and the short-circuiting transition time ratio At from the waveform of That is, the detection time is T
(sec), where the number of short circuits is n (times), the number of short circuit transitions per unit time N (times / sec) is N = n / T, and the short circuit transition time ratio At (%) is At = (Σt
s / T) × 100.

FIG. 4 shows the relationship between the arc length L (distance between the electrode and the base metal) and the number N of times the wire droplet is short-circuited when welding is performed using a DC arc and a pulse arc, respectively. According to this experiment, the number N of times the wire droplet has transferred to the short circuit
When the arc length L is short (the distance between the wire and the base metal is also short), the contact time with the base metal and the molten pool is long, so the number of times is small, and fine droplets migrate in a short time and reach the maximum at the position. After that, the arc length is long (wire,
As the distance between the base materials becomes longer), the droplets migrate while growing and show a decrease again. This tendency is observed in both DC arc and pulse arc. FIG.
Further, as shown in FIG. 4, when the arc length L and the distance between the wire and the base metal are too short (a), the molten pool is likely to be unstable, and the formation of weld beads is also likely to be extremely deteriorated. In particular, in the weaving welding in which the welding torch and the wire are swung left and right, problems often occur such as the wire adhering to the base material or the electrode coming into contact with the electrode and interrupting the welding. Further, when the arc length L or the distance between the wire and the base material is too long (d), the arc and the welding bead are disturbed by the migration of the unstable wire droplets that have grown large, and a welding defect is likely to occur. On the other hand, (b)
It was found that in the states of (c) and (c), the transfer of wire droplets and the arc were stable, and a good welding result of the welding bead was obtained. Therefore, in order to maintain the stable regions of (b) and (c), a judgment reference value m of the number of short circuit transitions is provided so that the number of short circuit transitions N during welding is always N ≧ m. It turns out that it is enough to control. The judgment reference value of the number of times of short circuit transfer may be set to about m = 3 to 5 (times / sec), and the wire position height is controlled by controlling the torch drive shaft on which the welding torch 1 and the welding wire 8 are mounted. Can be achieved by However, it is difficult to distinguish whether the wire position height is excessively small or excessively large when N <m by only judging the number of short-circuit transitions.
By utilizing the characteristics of the wire droplet short-circuiting transition time ratio, it is possible to perform the classification determination. FIG. 5 shows the relationship between the arc length and the short-circuit transfer time ratio of wire droplets. In the figure, the results of changing the pulse arc current value into three types: large, medium, and small are shown. The short-circuit transfer time ratio At of the wire droplets rapidly decreases from 100% of the short-circuit region as the arc length L and the distance between the wire and the base metal become longer, and then becomes 0.
It shows the characteristic of falling to%. With respect to the upper limit reference value b of the short circuit transition time rate, the short circuit transition time rate At is At> b
In the case of, the wire position height is too small and becomes an unstable region, and At <a
In the case of, the wire position height is excessive and becomes an unstable region. It can be seen that the stable region of the wire droplet and the welding is a region excluding these unstable regions, and is a region satisfying a ≦ At ≦ b. The lower limit of the short circuit transition time ratio is about a =
5 to 20 (%), and the upper limit reference value is about b = 80 to 95
It turns out that it is good to set each to (%).

Therefore, the wire short-circuit detecting means 14 shown in FIG. 1 is used to obtain the number N of times the wire droplet is transferred to the short circuit and the short-circuit transfer time ratio At, and this information is taken into the welding wire position determining means 15 to determine whether the wire position is good or bad. It makes a decision. For example, the short circuit transition time ratio At is At <
a, or the number N of short-circuit transitions is N <m, and
When At <a, the height of the wire position is determined to be excessive, and a descending control signal is transmitted to the welding controller 16. Further, when the short circuit transition time ratio At is a ≦ At ≦ b or the short circuit transition number N is N ≧ m, it is determined that the wire position height is appropriate and the wire position height is maintained as it is. ing. On the other hand, when At> b, or N <m, and At> b, the wire position height is determined to be too small, and a rising control signal is transmitted to the welding controller 16. When the welding controller 16 receives a descending control signal from the wire position determination circuit 15, the welding torch 1 and the torch drive shaft 4 on which the welding wire 8 is mounted are controlled to descend.
On the contrary, when receiving the rising control signal, the torch drive shaft 4
Is controlled to move upward. When the wire position height is proper and the vertical movement control signal is not output, the height of the welding torch and the welding wire are controlled to be maintained as they are. When the torch drive shaft 4 is provided with an operation for controlling the arc length to be constant, the torch drive shaft 4 is controlled in the ascending direction or the descending direction by the wire position determination circuit 15 determining whether the wire position is good or bad. At this time, the control operation with the constant arc length may be stopped only during the control period so that the control command of the wire position determination circuit is followed. Further, when the wire position determination circuit 15 determines that the wire position height is proper, the control operation with a constant arc length is restarted so as to maintain the wire position height, and continuous control of the torch drive shaft may be performed. . In this way, by controlling the torch drive shaft on which the welding torch and welding wire are mounted, the wire position height can be properly controlled, and the wire droplets are not disturbed and the welding bead does not become defective, and it is always stable. The transfer of wire droplets and good welding results can be obtained.

A method of diagnosing the abnormality of the welding wire and the electrode will be described. 6 and 7 show welding voltage Ea during welding.
Shows an example of the signal waveform of the electrode voltage Ve and ts in the figure is the short-circuiting transition time of the wire droplet, and ta
Represents the contact time of the electrode. As can be seen from comparison with the signal waveform of the wire voltage Vw shown in FIG. 3, when the wire droplet makes a short-circuit transition (short-circuit transition time ts), the level of the wire voltage Vw drops to near 0 V, whereas
The electrode voltage Ve has a characteristic that it rises to the level of the welding voltage only during the short circuit transition time ts. Figure 6
At the point ta where the level of the electrode voltage Ve has dropped to near 0V, when the disturbed droplet of the welding wire comes into contact with the electrode, the arc 2 is still generated, so the welding voltage changes slightly. It shows how to do. On the other hand, when the electrode 2 and the welding wire 8 come into contact with the molten pool of the base materials 5 and 27 (contact time ta), the levels of the welding voltage signal Ea and the electrode voltage signal Ve decrease to near 0 V as shown in FIG. To do. When such a contact phenomenon occurs, not only is the electrode damaged and consumed abnormally, but if the welding is continued as it is, it is difficult to continue a normal arc and a welding defect occurs.

Therefore, in order to prevent this, a reference voltage e2 for contact determination is provided here, and the abnormality determination means 24 monitors the levels of the welding voltage Ea and the electrode voltage Ve. Then, during the welding period, when the welding voltage signal Ea is Ea ≦ e2, it is determined that the electrode is in contact with the molten pool, and when the electrode voltage signal Ve is Ve ≦ e2, the droplet of the welding wire is in contact with the electrode. The welding stop command and the electrode abnormality display command are transmitted to the welding controller 16. Reference voltage e for contact judgment
It is desirable that 2 is set to be larger than 0 and not larger than about 3 V in consideration of contact resistance and cable resistance. With such a configuration, it is possible to minimize consumption due to contact with the electrode, and prevent occurrence of welding defects and deterioration of welding quality due to troubles of the welding wire and the electrode.

8 and 9 show an embodiment of a control operation flowchart of the present invention. Such control operation can be created by software and incorporated in the welding control storage device 17, for example. First, after the arc ON31 where the arc is generated and the welding wire are sent, the wire feed ON3
The detection is started after the detection waiting time 33 of 2. After the wire position detection and control processing 35 is performed, the electrode abnormality detection processing 36 is performed, and the processing operation is repeated until the arc is turned off 37 (welding is completed). In the electrode abnormality detection processing 36, electrode base material contact detection 37 and wire electrode contact detection 38 are performed. Then, when the level of the welding voltage signal Ea is Ea ≦ e2, it is determined that the electrode is in contact with the molten pool (base material contact 40), and when the level of the electrode voltage signal Ve is Ve ≦ e2. It is determined that the droplet of the welding wire has come into contact with the electrode (wire contact 42), and the welding stop 43 and the electrode abnormality display 44 are performed. On the other hand, wire position detection and control processing 35
Then, as shown in FIG. 12, the number of short-circuit transitions N (49) and the number of short-circuit transitions occurring during the sampling time T (46) of the detection 45 of the wire preform voltage Vw set separately for the DC arc 47 and the pulse arc 48. After obtaining the time ratio At (50), the quality of the wire position height is judged from the result judgment. Here, for example, the number of short-circuit transitions N is N
When ≧ m, when N <m, and the short circuit transition time ratio At is a
When ≤At≤b, the wire position height is appropriate 51, 52
The wire position height is maintained as it is.
Control to do so. In addition, N <m and At <
When it is a, it is determined that the wire position height is excessive 54, and the wire drive shaft descending control 56 is made in the direction in which only the welding wire is descended according to the cumulative value of wire descending (ΣΔVn ≦ c1).
Alternatively, the torch drive shaft lowering control 57 is performed in the direction in which both the welding torch and the welding wire are lowered. On the contrary, when N <m and At> b, the wire position height is determined to be too small 58, and both the welding torch and the welding wire are raised in accordance with the cumulative torch rise value (ΣΔZ ≦ c2). In addition, the torch drive shaft raising control 60 is performed, or the wire drive shaft raising control 61 is performed in the direction of raising only the welding wire. The lower limit value c1 of the wire descent may be set to about the initial arc length L, and the upper limit value c2 of the welding torch rise may be set to about twice the initial set arc length L.

With such a configuration, the number N of short-circuit transitions of the wire droplets during welding and the short-circuit transition time ratio At
From this, it is possible to judge the quality of the wire position height. Then, based on this determination result, the torch drive shaft 4 on which the welding torch 1 and the welding wire 8 are mounted is controlled,
Alternatively, by controlling the wire drive shaft 20 that moves only the position of the welding wire 8 up and down, the wire position height can be properly controlled more accurately, and the wire droplets are not disturbed and the welding bead is not defective. It is possible to always obtain stable wire droplet transfer and good welding results. Also,
By providing the wire drive shaft 20, positioning of the welding wire in the vertical and horizontal directions can be performed independently, and the transfer of the wire droplets can be finely controlled and the usability can be improved. Further, by diagnosing the abnormality of the welding wire and the electrode, it is possible to minimize the wear due to the contact of the electrode and prevent the occurrence of welding defects and the deterioration of the welding quality due to the trouble of the welding wire and the electrode.

By equipping the automatic welding system with the control function of the welding wire position of the present invention, it is possible to realize various welding joints.
Appropriate control of the welding wire position and electrode abnormality determination can be performed for pass welding and multi-layer multi-pass welding, and automation of welding and improvement of welding quality can be achieved. For example, it can be applied to automatic welding of a chemical plant and a nuclear power plant having many welded pipes.

[0022]

By using the welding wire position detecting method and apparatus of the present invention, it is possible to easily determine the quality of the welding wire, which is related to the quality of the welding bead shape.
The wire height can be properly controlled, and good welding results of the welding bead can be obtained. In addition, when an abnormality occurs in the electrode and welding wire during welding, the abnormality is instantly detected and the welding is stopped. It is possible to prevent the deterioration of the result. Further, by using the welding control device and the automatic welding system provided with the function of detecting the position of the welding wire of the present invention, one-pass welding of various welded joints such as welded structures, welded pipes, and welded assemblies of chemical plants and nuclear power plants. Alternatively, even for multi-layer multi-pass welding, proper detection of the welding wire position and abnormality diagnosis of the electrode can be performed, so that not only beginners can easily perform welding, but also it is easy to use, automation of welding and welding quality Can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment showing the contents relating to the control of the welding wire position of the present invention.

FIG. 2 is an explanatory view showing the position of a welding wire fed into an arc of the present invention.

FIG. 3 is a waveform diagram of a typical wire-base material voltage Vw observed in the wire melting characteristic of the present invention.

FIG. 4 is an explanatory diagram showing the relationship between the arc length and the number of times of short circuiting in wire melting according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a relationship between an arc length and a short circuit transition time rate according to an embodiment of the present invention.

FIG. 6 is a waveform diagram of typical welding voltage and wire-electrode voltage determined by the abnormality diagnosis of the welding wire and electrode of the present invention.

FIG. 7 is another waveform diagram of a typical welding voltage and wire-electrode voltage determined by the abnormality diagnosis of the welding wire and the electrode of the present invention.

FIG. 8 is an operation flowchart relating to welding wire position control and electrode abnormality diagnosis of the present invention.

FIG. 9 is an operation flowchart relating to control of the welding wire position of the present invention.

[Explanation of symbols]

1 ... Welding torch, 2 ... Electrode, 4 ... Torch drive shaft, 6 ... Arc, 7 ... Welding power supply, 8 ... Welding wire, 12 ... Traveling rail, 15 ... Welding wire position means, 16 ... Welding controller, 23 ... Electrode voltage Detection means, 24 ... Abnormality determination means, 2
7 ... Base material for pipe welding joint, 28 ... Pipe welding traveling carriage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Mizuguchi 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Yuji Yamaguchi 3-chome, Saiwai-cho, Hitachi, Ibaraki No. 1 Hitachi Ltd., Hitachi Plant (72) Inventor Eiji Hino 3-1-1, Saiwaicho, Hitachi City, Ibaraki Hitachi Ltd., Hitachi Plant

Claims (1)

[Claims] 1. A non-energizing welding wire is generated in the arc and in a molten pool by applying an electric current between a base material of a welded joint and a non-consumable electrode at a tip of a welding torch to generate an arc having an arbitrary output waveform. In a method for detecting the position of a welding wire when performing welding while feeding, a wire voltage detecting means for detecting a wire voltage signal generated between the non-energized welding wire and the welding base material, and the welding wire is short-circuited. Wire short circuit detection means for obtaining the number of short circuit transitions per unit time and the short circuit transition time ratio,
The position of the welding wire is determined by the wire position determination means during the welding period after the arc is generated, by providing wire position determination means for determining the position of the welding wire by taking in the number of times of the short circuit transition and the short circuit transition time rate. After determining whether the height of the welding wire is appropriate or unsuitable, if the position of the welding wire is excessive and is determined to be unsuitable, a control signal for lowering the height is set, and vice versa. An electrode for detecting an electrode voltage signal generated between the non-conducting welding wire and the non-consumable electrode by transmitting control signals for increasing the height when it is determined that the height is too small and inappropriate. Voltage detection means, welding voltage detection means for detecting a welding voltage signal generated between the electrode through which the welding current flows and the welding base metal, and abnormality determination for determining abnormality of the electrode and the welding wire Steps are provided respectively, and at the same time as the operation of the wire position discriminating means or after transmitting a wire position height control signal, the electrode voltage signal and the welding voltage signal are taken into the abnormality discriminating means to determine an abnormality. When the electrode voltage signal is small with respect to the reference voltage value of, it is determined that the droplet of the welding wire has contacted the electrode,
When the welding voltage signal is smaller than the reference voltage value for the abnormality determination, it is determined that the electrode is in contact with the molten pool, and a welding stop command and an electrode abnormality display command are issued. How to detect the position of the wire.