Electroslag welding apparatus and electroslag welding method

Abstract

To perform excellent welding by suppressing the occurrence of defective penetration when performing electroslag welding with two electrodes of the same polarity.SOLUTION: The electroslag welder 1 includes two weld torches 7 having the same polarity, a swing mechanism that horizontally swings both of the two weld torches 7 at the same time with the two weld torches 7 spaced apart from each other, and an adjustment mechanism that can adjust the distances from the lower ends of contact tips 8 of the two weld torches 7 to the surface of molten slag 10 to 20 to 150mm. The respective weld torches 7 are arranged in such a manner that the distances between the wires on the surface of the molten slag 10 of the two weld wires 9 fed from the respective two weld torches 7 at the time of the weld are equal to or below the 40mm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electroslag welding apparatus and an electroslag welding method. [Background technology]

[0002] In recent years, the steel construction industry has seen a trend toward super-tall buildings and deeper underground construction, and the steel materials used are becoming increasingly stronger, tougher, and more highly valued, as well as thicker. For example, it is expected that box columns using steel plates up to 100 mm thick will be used in urban buildings of the near future. Furthermore, the use of thick plates is also increasing in structures such as ship shells, oil tanks, and wind power generation poles (towers).

[0003] Electroslag welding, which allows for vertical automatic welding, is known as a welding method for thick plates used in structures. Compared to electrogas arc welding, another vertical automatic welding method, electroslag welding generates less arc radiation heat, fumes, spatter, etc., making it a welding method with an excellent working environment during welding.

[0004] Electroslag welding is a method of welding base materials together by forming molten slag in a groove surrounded on all sides by plates such as the base material to be welded and a backing metal, melting the welding wire delivered from the welding torch and the base material to be welded in the slag bath, and cooling and solidifying the molten metal.

[0005] Claim 6 of Patent Document 1 discloses a method for electroslag welding, which uses a first melting electrode and a second melting electrode to weld a first base metal and a second base metal, in which a first DC voltage is applied between the first melting electrode and the first and second base metals, and a second DC voltage of the same polarity as the first DC voltage is applied between the second melting electrode and the first and second base metals. Patent Document 1 also describes that in the step of melting the first and second base metals, the inter-electrode distance between the first and second melting electrodes is set to a distance at which the magnetic fields do not interfere with each other. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6152203 Summary of the Invention [Problem to be solved by the invention]

[0007] To ensure stable welding quality, it is necessary to prevent poor penetration in the groove. However, Patent Document 1 describes that when two electrodes of the same polarity are used and welding is performed with the inter-electrode distance between the two electrodes set to a distance that causes mutual interference between the magnetic fields, poor penetration occurs. Therefore, when performing electroslag welding with two electrodes of the same polarity, improvements are needed to prevent poor penetration and improve welding quality.

[0008] The present invention has been made in view of the above circumstances, and has an object to suppress the occurrence of poor penetration when performing two-electrode, same-polarity electroslag welding, thereby enabling good welding. [Means for solving the problem]

[0009] The inventors have discovered that in electroslag welding with two electrodes of the same polarity, even if the distance between the two electrodes is short and the magnetic fields of the two electrodes interfere with each other, poor penetration can be suppressed by performing welding while oscillating both electrodes.

[0010] The present invention, which solves the above-mentioned problems, is an electroslag welding apparatus used for vertical upward welding, comprising two welding torches of the same polarity, a swing mechanism that swings both welding torches horizontally at the same time while maintaining a constant distance between them, and an adjustment mechanism that can adjust the distance from the lower end of a contact tip provided on each of the two welding torches to the molten slag surface during welding to between 20 and 150 mm, and is characterized in that each welding torch is positioned so that the distance between the two welding wires fed from each of the two welding torches on the molten slag surface during welding is 40 mm or less.

[0011] Another aspect of the present invention is an electroslag welding method for performing vertical upward welding, characterized in that, when welding is performed using two welding torches of the same polarity, the distance from the lower end of a contact tip provided on each of the two welding torches to the molten slag surface is 20 to 150 mm, the distance between two welding wires fed from each of the two welding torches on the molten slag surface is 40 mm or less, and welding is performed while both of the two welding torches are simultaneously swung horizontally while maintaining a constant distance between them. [Effects of the Invention]

[0012] According to the present invention, when performing two-electrode same-polarity electroslag welding, the occurrence of poor penetration can be suppressed and good welding can be performed. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing a schematic configuration of an electroslag welding apparatus according to an embodiment of the present invention; [Figure 2] FIG. 1 is a diagram showing a schematic configuration of a wire straightener. [Figure 3] 1 is an enlarged view of the welding torch and its surroundings, and a diagram showing the schematic configuration of a slag bath detector. FIG. [Figure 4] FIG. 1 is a diagram showing a schematic configuration of a connector for connecting two welding torches and a flux supply nozzle. [Figure 5] FIG. 2 is a diagram showing a schematic configuration of a flux supplying device. [Figure 6] FIG. 10 is a schematic diagram of the groove copying mechanism as seen from the positive side in the Z direction. [Figure 7] FIG. 10 is a schematic diagram of the groove copying mechanism as viewed from the positive side in the X direction. [Figure 8] 10 is a flowchart relating to the operation of a carriage moving on a rail. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification and the drawings, elements having substantially the same functional configuration are designated by the same reference numerals, and redundant description will be omitted. In the drawings, the X, Y, and Z directions are perpendicular to each other, and the Z direction is the vertical direction (perpendicular to the horizontal plane).

[0015] <Electroslag welding equipment> FIG. 1 is a diagram showing a schematic configuration of an electroslag welding apparatus according to this embodiment, and hatched portions in the diagram indicate cross sections.

[0016] The electroslag welding apparatus 1 includes a fixed water-cooled copper plate 2, which is an example of a fixed plate, and a sliding water-cooled copper plate 3, which is an example of a sliding plate. The fixed water-cooled copper plate 2 corresponds to a backing metal. The sliding water-cooled copper plate 3 faces the fixed water-cooled copper plate 2 and is disposed at a distance from the fixed water-cooled copper plate 2. The sliding water-cooled copper plate 3 is configured to be movable in the vertical direction (Z direction).

[0017] Both the fixed water-cooled copper plate 2 and the sliding water-cooled copper plate 3 have a structure that allows cooling water to flow through them, and during welding, they are cooled to a temperature that does not melt the molten slag (e.g., 1300 to 2000°C). Note that the weld metal can be more easily cooled by expanding the water-cooled area by increasing the number of locations where water-cooled copper plates are used.

[0018] In this embodiment, a fixed water-cooled copper plate is used as the fixed plate, but this is not limited to copper plates. For example, a ceramic plate with a high heat resistance temperature can be used without cooling. Similarly, the sliding plate is not limited to copper plates. Other metal plates can be used. However, if metal plates with a melting point lower than the molten slag temperature are used as the fixed plate or sliding plate, a cooling means such as a water-cooling structure must be applied to prevent the metal plate from dissolving in the molten slag.

[0019] Between the fixed water-cooled copper plate 2 and the sliding water-cooled copper plate 3, one of the two base materials (not shown) to be welded is placed on the front side in the direction perpendicular to the plane of the paper in Fig. 1, and the other base material is placed on the back side in the direction perpendicular to the plane of the paper in Fig. 1. In the electroslag welding device 1, the area surrounded by the fixed water-cooled copper plate 2, the sliding water-cooled copper plate 3, and the two base materials (not shown) forms a groove 4.

[0020] The electroslag welding apparatus 1 includes a carriage 5 and multiple separable rails 6 on which the carriage 5 travels, as an example of a movement mechanism for raising the sliding water-cooled copper plate 3 and a welding torch 7 (described later). The multiple rails 6 are connected to one another in the vertical direction (Z direction), and the number of connected rails 6 can be changed as desired depending on the welding length. The sliding water-cooled copper plate 3 is fixed to the carriage 5, and when the carriage 5 is raised, for example, the sliding water-cooled copper plate 3 also rises vertically upward (toward the positive Z direction) by the same amount as the carriage 5.

[0021] Two welding torches 7 are attached to the carriage 5 above the attachment point of the sliding water-cooled copper plate 3. Because the sliding water-cooled copper plate 3 and the two welding torches 7 are fixed to the same carriage 5, they can move vertically while always maintaining the same relative positional relationship with each other.

[0022] A contact tip 8 is attached to the tip of each welding torch 7. Welding wire 9 fed from a wire feeder (not shown) passes through the interior of each welding torch 7 and is fed out from the tip of contact tip 8. The welding wire 9 is preferably a solid wire or a cored wire (flux-cored wire) with a diameter of 1 to 2 mm. In this case, for example, a solid wire may be fed out from both of the two welding torches 7, a cored wire may be fed out from both of the two welding torches 7, or a solid wire may be fed out from one welding torch 7 and a cored wire may be fed out from the other welding torch 7.

[0023] Each welding torch 7 is connected to a welding power source (not shown), and welding current is supplied to a welding wire 9 via a contact tip 8. The two welding wires 9, one fed from each of the two welding torches 7, each function as an electrode, so the electroslag welding apparatus 1 is a two-electrode welding apparatus. The polarities of the two electrodes are the same, and the polarity combination is either positive-positive or negative-negative.

[0024] The welding power source (not shown) connected to each welding torch 7 may be a thyristor-controlled power source, but is preferably an inverter-controlled digital power source, which allows for quick response and precise control when adjustments such as the welding current are required.

[0025] Within the groove 4 during welding, the welding torch 7 can be moved vertically (in the Z direction) by itself using a screw-type slider (not shown), allowing its position relative to the carriage 5 to be adjusted. Furthermore, by moving the welding torch 7 in the Z direction, the length (dry extension) of the welding wire 9 from the lower end of the contact tip 8 to the slag bath surface can be changed. Resistance heating occurs within the welding wire 9 as the welding current flows from the lower end of the contact tip 8 to the slag bath 10 (described below). The longer the dry extension, the greater the resistance heating within the wire. This, combined with the resistance heating in the slag bath 10 after the welding wire 9 is immersed, promotes wire melting and the generation of molten metal, facilitating stable penetration during welding. Furthermore, the resistance heating within the welding wire 9 before immersion in the slag bath contributes to reducing resistance heating within the slag bath 10, thereby reducing welding heat input and increasing welding speed, while also enabling stable penetration.

[0026] The electroslag welding apparatus 1 is equipped with an adjustment mechanism that can adjust the distance from the bottom of the contact tip 8 to the surface of the slag bath 10. If the dry extension is shorter than 20 mm, the contact tip 8 will be too close to the slag bath 10, resulting in significant thermal wear of the contact tip 8. If it is longer than 150 mm, the wire tip may bend, causing the immersion position of the wire tip in the slag bath 10 to become unstable, making it difficult to maintain stable welding and ensure stable penetration. Therefore, in the electroslag welding apparatus 1 according to this embodiment, the dry extensions of the two welding torches 7 are preferably adjusted to 20 to 150 mm, and more preferably to 30 to 130 mm. The dry extensions of the welding torches 7 may differ from each other as long as they are within the range of 20 to 150 mm.

[0027] During welding, the groove 4 contains a slag bath 10 formed by melting flux, molten metal 11 pooling at the bottom of the slag bath 10, and a bead 12 formed by cooling and solidifying the molten metal 11. During welding, the tip of the welding wire 9 is immersed in the slag bath 10, and current is passed through the slag bath 10 via the welding wire 9. In addition to the resistance heat generated by the current flowing through the slag bath 10 between the contact tip 8 and the slag bath 10, resistance heat is also generated in the slag bath 10 due to the welding current flowing through the slag bath 10, where the wire tip is immersed. This resistance heat melts the welding wire 9 and the base material (not shown) to be welded. This forms the molten metal 11, which is deposited on the bead 12. The molten metal 11 then gradually cools from the bottom, and the cooled portion solidifies, welding the base materials together.

[0028] The electroslag welding apparatus 1 is equipped with a swinging mechanism (not shown) that swings two welding torches 7 horizontally at the same time. During welding, the two welding torches 7 can be swung simultaneously in the direction of the white arrow in FIG. 1 while maintaining a fixed distance between them. By performing welding while swinging the two welding torches 7, it is possible to promote penetration of the base material in the groove 4 and prevent poor penetration. The structure of the swinging mechanism that swings the two welding torches 7 is not particularly limited, and a known swinging device (oscillating device) can be used.

[0029] A wire straightener 14 is preferably provided at the connection between each of the two welding torches 7 and the conduit cable 13. The wire straightener 14 illustrated in FIG. 2 includes a housing 15 through which the welding wire 9 passes and a plurality of rollers 16 that clamp the welding wire 9. The welding wire 9 passing through the housing 15 is plastically deformed as it passes through the rollers 16, thereby straightening any warping or bending. This prevents clogging due to meandering of the welding wire 9 within the welding torch 7 and also stabilizes the immersion position of the welding wire 9 in the slag bath 10. Note that FIG. 2 is a view from above in the vertical direction (positive side in the Z direction), and the rollers 16 are arranged to straighten warping and bending in a horizontal plane (in the XY plane). However, another wire straightener may be provided to straighten warping and bending in the vertical direction (Z direction) as needed.

[0030] 3 is an enlarged view of the vicinity of the tips of the two welding torches 7. The two welding torches 7 are arranged so that the wire-to-wire distance d between the two welding wires 9 fed from each welding torch 7 on the surface of the slag bath 10 is 40 mm or less. For example, if the two welding wires 9 reach the surface of the slag bath 10 parallel to each other, the wire-to-wire distance d can also be rephrased as the distance between the centers of the contact tips 8 of the two welding torches 7. When welding is performed under conditions where the wire-to-wire distance d is 40 mm or less, the welding is performed at a distance where the magnetic fields generated by the two electrodes interfere with each other. However, the electroslag welding apparatus 1 according to this embodiment performs welding while oscillating the two welding torches 7 (i.e., while oscillating the two electrodes), thereby preventing poor penetration.

[0031] As described above, both of the two welding torches 7 oscillate during welding, but the flux supply nozzle 33 is connected to the two welding torches 7 by the connector 17, and therefore oscillates together with the two welding torches 7 during welding. Therefore, in the electroslag welding apparatus 1 according to this embodiment, when flux is supplied during welding, the flux is always supplied from between the two welding torches 7 (i.e., between the two welding wires 9). When supplying flux in this manner, the flux can be introduced into the area surrounded by the two welding wires 9, which becomes hot during welding, and therefore melting of the flux in the groove 4 can be promoted.

[0032] If the inter-wire distance d exceeds 40 mm, the two welding torches 7 cannot swing wide enough in the groove 4, and sufficient penetration cannot be achieved. On the other hand, if the inter-wire distance d is less than 10 mm, it becomes difficult to supply flux between the two electrodes, so the inter-wire distance d is more preferably 10 mm or more and 40 mm or less. Furthermore, to maintain stable welding, it is desirable for the inter-wire distance d to be in the range of 15 mm or more and 30 mm or less.

[0033] As shown in FIG. 3, a flux supply nozzle 33 is disposed between the two welding torches 7. The two welding torches 7 and the nozzle 33 are connected by a connector 17. As shown in FIG. 4, the connector 17 is a cubic member having two through holes 17a for inserting the welding torches 7 and a through hole 17b formed between the two through holes 17a for inserting the nozzle 33. The connector 17 is formed of a material with excellent insulating properties and heat resistance, such as Teflon (registered trademark). Also, as shown in FIG. 3, a drop prevention ring 18 may be provided on the underside of the connector 17 to prevent the connector 17 from dropping.

[0034] As shown in FIG. 3, the electroslag welding apparatus 1 includes a slag bath detector 20 that detects the bath surface of the slag bath 10. The slag bath detector 20 includes a tungsten rod 21 as a detector for detecting the bath surface of the slag bath 10 and a conductive plate 22 that supports the tungsten rod 21. The conductive plate 22 may be made of any conductive material, such as a copper plate. In this embodiment, the conductive plate 22 is L-shaped and has an upper surface 22a and a side surface 22b. When such a slag bath detector 20 is used, the supply of flux during welding raises the bath surface of the slag bath 10. When the tungsten rod 21 comes into contact with the slag bath and establishes communication, the supply of flux can be temporarily stopped to prevent excessive flux supply.

[0035] (Flux supply device) 1, the electroslag welding apparatus 1 includes a flux supply device 30 that supplies flux into the groove 4. The flux supply device 30 includes a hopper 31 that stores the flux, a sprayer 32 that sprays a fixed amount of flux, and a nozzle 33 that supplies the flux from the sprayer 32 to the slag bath 10.

[0036] The hopper 31 is a container having a rectangular horizontal cross section. The upper side wall of the hopper 31 is composed of a vertical wall 31a extending parallel to the vertical plane, and the lower side wall of the hopper 31 is composed of an inclined wall 31b having an inclined surface. The shape of the hopper 31 is not particularly limited, and the horizontal cross section may be circular or polygonal.

[0037] The spraying device 32 will be described in detail later, but the spraying device 32 and the carriage 5 are fixed to each other via a support part 34. This allows the flux supplying device 30 to move up or down together with the carriage 5.

[0038] The nozzle 33 is connected to the lower surface of the spraying device 32 and extends from the lower surface of the spraying device 32 to the vicinity of the bath surface of the slag bath 10.

[0039] 5 is a diagram showing a schematic configuration of a flux supply device according to this embodiment, with the internal structures of some components shown for ease of explanation. The black dots in the diagram represent flux particles.

[0040] The spraying device 32 includes an uneven roller 35 as a cylindrical rotating body, a housing 36 that houses the uneven roller 35, and a motor (not shown) attached to the side of the housing 36 as a rotation drive source.

[0041] The uneven roller 35 rotates around a rotation axis in the horizontal direction (Y direction in this embodiment). A plurality of grooves 37 are formed at intervals along the circumferential direction of the uneven roller 35 on the periphery of the uneven roller 35. These grooves 37 are arranged, for example, at equal intervals, and extend along the direction of the rotation axis. Furthermore, by forming a plurality of grooves 37, the uneven roller 35 has convex portions 38 between adjacent grooves 37. Note that the uneven roller 35 is an example of a rotating body, and gears, for example, may also be used as the rotating body.

[0042] The housing 36 is a container having a cylindrical hollow portion 39 therein. The inner peripheral surface of this hollow portion 39 and the outer peripheral surface (the circumferential surface of the maximum outer diameter portion) of the uneven roller 35 are in close proximity and face each other, and the multiple protrusions 38 of the uneven roller 35 and the inner peripheral surface of the hollow portion 39 are in approximate contact to the extent that rotation of the uneven roller 35 is not hindered. Therefore, a space into which flux is filled is formed between the grooves 37 of the uneven roller 35 and the inner peripheral surface of the hollow portion 39.

[0043] An upper opening 40 is formed in the upper surface of the housing 36, which communicates with the lower end of the hopper 31. The upper opening 40 penetrates from the upper surface of the housing 36 to a hollow portion 39 within the housing 36, and the flux discharged from the lower end of the hopper 31 passes through the upper opening 40 and falls into the groove 37 of the uneven roller 35.

[0044] A lower opening 41 is formed in the lower surface of the housing 36, and communicates with the upper end of the nozzle 33. The lower opening 41 penetrates from the hollow portion 39 inside the housing 36 to the lower surface of the housing 36, and the flux filled in the grooves 37 of the uneven roller 35 passes through the lower opening 41 and falls into the nozzle 33.

[0045] According to the spraying device 32 of this embodiment, the volume between the inner circumferential surface of the hollow portion 39 of the housing 36 and each groove 37 of the uneven roller 35 is equal, so that the amount of flux in each groove 37 becomes equal when the uneven roller 35 rotates after the flux falls into the grooves 37 from the upper opening 40. This makes it possible to spray a fixed amount of flux.

[0046] To ensure a stable supply of flux, it is preferable to prevent clogging of the flux in the hopper 31. In the example of Fig. 5, a vibration driver 51 that generates vibrations is provided, and the vibrations generated by the vibration driver 51 are transmitted to the hopper 31 via a stay 52, causing the hopper 31 to vibrate, thereby preventing clogging of the flux. The vibration driver 51 generates vibrations, for example, using an eccentric motor with an eccentric weight, a reciprocating air cylinder mechanism, or a solenoid that can generate electromagnetic vibrations.

[0047] (groove copying mechanism) 1, the electroslag welding apparatus 1 according to this embodiment is provided with a groove copying mechanism 60 above the welding torch 7. The groove copying mechanism 60 is a mechanism for automatically adjusting the position of the tip of the welding torch 7 in the groove width direction (Y direction) according to the shape of the groove 4.

[0048] The groove copying mechanism 60 has a disk-shaped copying roller 61 and a roller support part 62 that supports the copying roller 61. The copying roller 61 is supported by the roller support part 62 so that it can rotate in the XZ plane with its rotation axis in the Y direction. The roller support part 62 is fixed to the carriage 5, and when the carriage 5 rises, the copying roller 61 also rises via the roller support part 62. The copying roller 61 is made of, for example, a heat-resistant metal material, and has multiple through holes 63 formed therein to reduce weight.

[0049] 6 is a diagram showing a schematic view of the groove copying mechanism 60 as seen from above in the vertical direction (positive side in the Z direction). The roller support part 62 is configured to be movable in the depth direction (X direction) of the groove 4, and when welding is to be started, the roller support part 62 is advanced in advance toward the groove 4, and the position of the roller support part 62 in the groove depth direction is fixed with the copying roller 61 in contact with the base material of the groove 4.

[0050] Additionally, the roller support part 62 is attached to a stroke encoder 64 that can detect the amount of movement in the groove width direction (Y direction). Therefore, when the profiling roller 61 moves in the width direction within the groove 4, the amount of movement of the profiling roller 61 in the groove width direction can be detected via the roller support part 62. The stroke encoder 64 is an example of a detection mechanism that detects the amount of movement of the profiling roller 61 in the groove width direction.

[0051] FIG. 7 is a schematic diagram of the groove tracking mechanism 60 as viewed from the positive side in the X direction. The groove tracking mechanism 60 includes a cylinder mechanism 65 that moves the welding torch 7 in the groove width direction. The movement amount of the tracking roller 61 in the groove width direction (Y direction) detected by the stroke encoder 64 is output to the control unit 100. Based on the information on the movement amount of the tracking roller 61 in the Y direction, the control unit 100 outputs a control signal to a drive source (not shown), such as a stepping motor, and the cylinder of the cylinder mechanism 65 expands and contracts in the groove width direction due to the driving force of the drive source. The expansion and contraction movement of the cylinder moves the position of the tip of the welding torch 7 in the groove width direction. The cylinder mechanism 65 is an example of an adjustment mechanism that adjusts the position of the tip of the welding torch 7 in the groove width direction.

[0052] If the electroslag welding apparatus 1 has the groove profiling mechanism 60 as described above, when the carriage 5 shown in FIG. 1 rises during welding, the profiling roller 61 rotates and rises within the groove 4. If the center line of the groove 4 shifts in the width direction (Y direction), the profiling roller 61 in contact with the base material surface within the groove 4 also moves in the groove width direction, and the welding torch 7 can be moved by the same amount as the movement of the profiling roller 61 in the groove width direction. This makes it possible to perform welding while automatically adjusting the tip position of the welding torch 7 to a predetermined position (for example, a position within a region that is 1 / 2 of the groove spacing and includes the center position in the width direction of the groove 4).

[0053] (Control unit) The electroslag welding apparatus 1 is controlled by a control unit 100 (FIG. 1). The control unit 100 is, for example, a computer equipped with a CPU, memory, etc., and is mounted on, for example, an operation panel (not shown) that can be operated by a field worker. The control unit 100 has a program storage unit (not shown). The program storage unit stores various programs for performing a series of welding processes in the electroslag welding apparatus 1. For example, the program storage unit stores a program for controlling the operation of the carriage 5 based on the magnitude of the welding current, a program for controlling the start or stop of supply of flux from the flux supply device based on a bath surface detection signal output from the slag bath detector 20, and a program for controlling the adjustment of the position of the tip of the welding torch 7 in accordance with the amount of movement of the profiling roller 61 in the groove width direction. These programs may be recorded on a computer-readable storage medium and installed into the control unit 100 from the storage medium.

[0054] Here, the operation of the carriage 5 during welding will be described. FIG.

[0055] First, during welding, welding wire 9 is fed from the tip of welding torch 7 into slag bath 10 at a constant feed rate, and when welding wire 9 is immersed in slag bath 10, welding wire 9 melts and the extension length of welding wire 9 is shortened (step S101). At this time, the resistance to the welding voltage decreases by the shortened extension length of welding wire 9, but because the welding voltage applied from a welding power source (not shown) is constant, the welding current flowing through welding wire 9 increases (step S102).

[0056] Next, the control unit 100 (FIG. 1) compares the welding current with a preset set current value and determines whether the welding current exceeds the set current value (step S103). The preset "set current value" is a current value that can be set by a person skilled in the art to perform appropriate electroslag welding depending on the composition of the welding wire, the wire feed speed, and other welding conditions. The set current value information held by the control unit 100 may be directly input to an operation panel (not shown) by a field worker at the start of welding, taking into account the wire feed speed setting conditions, or may be pre-stored in the control unit 100. The welding current value to be compared with the set current value is measured using a known method and input to the control unit 100.

[0057] In the above-mentioned step S103, if the welding current is equal to or less than the set current value, the process returns to step S101. On the other hand, if the welding current exceeds the set current value, the carriage 5 is raised (step S104), as shown in Fig. 8(c).

[0058] The carriage 5 rises at a preset constant speed (e.g., 30 mm / min), and as the carriage 5 rises, the distance between the tip of the welding torch 7 and the surface of the slag bath 10 increases, and the extension length of the welding wire 9 increases (step S105).Then, the resistance to the welding voltage increases by the amount of the increase in the extension length of the welding wire 9, and as a result, the welding current decreases (step S106).

[0059] Next, the control unit 100 (FIG. 1) compares the welding current with a set current value and determines whether the welding current is less than the set current value (step S107). The set current value in step S107 is the same as the set current value in step S103. If the welding current is equal to or greater than the set current value in step S107, the process returns to step S104, and the carriage 5 continues to rise. On the other hand, if the welding current is less than the set current value, the raising of the carriage 5 is temporarily stopped (step S108).

[0060] In this way, in the electroslag welding apparatus 1, the welding current varies during welding depending on the extension length of the welding wire 9 from the tip of the welding torch 7, but when the upper limit value of the welding current exceeds a preset current value, a trigger is triggered to raise the carriage 5. This also raises the sliding water-cooled copper plate 3 and the welding torch 7.

[0061] Although the electroslag welding apparatus 1 according to this embodiment is a two-electrode apparatus having two welding torches 7, the welding current that triggers the lifting of the carriage 5 may be the welding current measured by either of the two welding torches 7. Alternatively, for example, the average value of the welding currents measured by the two welding torches 7 may be used as the welding current to be compared with the set current value. In this embodiment, the sliding water-cooled copper plate 3 and the welding torch 7 are fixed to one carriage 5, so that the sliding water-cooled copper plate 3 and the welding torch 7 also lift simultaneously when the carriage 5 lifts. However, an apparatus configuration in which the sliding water-cooled copper plate 3 and the welding torch 7 lift separately may also be employed.

[0062] The above has described the schematic configuration of the electroslag welding apparatus 1 according to this embodiment. This electroslag welding apparatus 1 is a two-electrode, same-polarity welding apparatus, and the two welding torches 7 are arranged so that the inter-wire distance d between the two welding wires 9 fed from each of the two welding torches 7 during welding is 40 mm or less. During welding, the two electrodes are spaced apart so that their magnetic fields interfere with each other. However, by swinging both of the two welding torches 7 and adjusting the distances from the lower ends of the contact tips 8 to the molten slag surface (the surface of the slag bath 10) to 20 to 150 mm, electroslag welding can be achieved with reduced penetration failure.

[0063] While one embodiment of the present invention has been described above, the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that such modifications also fall within the technical scope of the present invention.

[0064] For example, the components of the above-described embodiments can be combined in any manner, and such combinations will naturally provide the functions and advantages of the individual components involved in the combination, as well as other functions and advantages that will be apparent to those skilled in the art from the description herein.

[0065] Furthermore, the effects described herein are merely descriptive or exemplary and are not limiting. In other words, the technology according to the present disclosure may achieve other effects that are apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects.

[0066] Note that the following configuration examples also fall within the technical scope of the present disclosure. (1) An electroslag welding device used for vertical upward welding, Two welding torches of the same polarity; a swing mechanism that swings both of the two welding torches in a horizontal direction simultaneously while maintaining a constant distance between the two welding torches; and an adjustment mechanism that can adjust the distance from the lower end of the contact tip provided on each of the two welding torches to the molten slag surface during welding to 20 to 150 mm, An electroslag welding apparatus characterized in that each welding torch is positioned so that the wire-to-wire distance between the two welding wires fed from each of the two welding torches on the molten slag surface during welding is 40 mm or less. (2) An electroslag welding device as described in (1), characterized in that it has a mechanism for automatically raising a sliding plate, which is one of the multiple plate materials that make up the groove, and the welding torch as welding progresses. (3) The electroslag welding apparatus according to (2), further comprising a control unit that controls the sliding plate and the welding torch to rise when the upper limit value of the welding current of either electrode of the two welding torches exceeds a preset current value. (4) Multiple rails that can be separated; a carriage that moves up along the rail, The electroslag welding device according to any one of (1) to (3), wherein the sliding plate and the welding torch are fixed to the carriage. (5) An electroslag welding device according to any one of (1) to (4), characterized in that it is provided with a groove tracking mechanism that can automatically adjust the position of the tip of the welding torch in the groove width direction according to the shape of the groove. (6) The electroslag welding device according to any one of (1) to (5), wherein the welding power sources used for the welding torches are all inverter-controlled digital power sources. (7) The electroslag welding device according to any one of (1) to (6), wherein the welding wire is a solid wire or a cored wire having a diameter of 1 to 2 mm. (8) The electroslag welding device according to any one of (1) to (7), further comprising a wire straightener at a connection between the welding torch and the conduit cable. (9) The electroslag welding device according to any one of (1) to (8), characterized in that it is configured to supply flux between two welding wires fed from each of the two welding torches. [Industrial Applicability]

[0067] The present invention is applicable to electroslag welding. [Explanation of symbols]

[0068] 1. Electroslag welding equipment 2 Fixed water-cooled copper plate 3 Sliding water-cooled copper plate 4 Bevel 5 carts 6 Rail 7. Welding torch 8 Contact Tips 9 Welding Wire 10 Slag bath (molten slag) 11 Molten Metal 12 beads 13 Conduit Cable 14 Wire Straightener 15 Case 16 Laura 17 Connector 17a, 17b through hole 18 Anti-drop ring 20 Slag bath detector 21 Tungsten rod 22 Conductive plate 22a Top part 22b Side part 30 Flux supply device 31 Hopper 32 Spraying equipment 33 nozzle 34 Support part 35 Uneven Roller 36 Case 37 Groove 38 Convex part 39 Hollow part 40 Top opening 41 Lower opening 51 Vibration drive unit 52 Stay 60 Groove copying mechanism 61 Copying Roller 62 Roller support part 63 Through hole 64 stroke encoder 65 Cylinder mechanism 100 control section

Claims

1. An electroslag welding apparatus used for vertical upward welding, Two welding torches of the same polarity; a swing mechanism that swings both of the two welding torches in a horizontal direction simultaneously while maintaining a constant distance between the two welding torches; and an adjustment mechanism that can adjust the distance from the lower end of the contact tip provided on each of the two welding torches to the molten slag surface during welding to 20 to 150 mm, 1. An electroslag welding apparatus, wherein the two welding torches are arranged so that the distance between the two welding wires fed from each of the two welding torches on the surface of the molten slag during welding is 40 mm or less.

2. 2. The electroslag welding apparatus according to claim 1, further comprising a mechanism for automatically raising a sliding plate, which is one of a plurality of plate materials constituting the groove, and the welding torch as welding progresses.

3. 3. The electroslag welding apparatus according to claim 2, further comprising a control unit that controls the sliding plate and the welding torch to rise when an upper limit value of the welding current of either electrode of the two welding torches exceeds a preset set current value.

4. Separable rails and a carriage that moves up along the rail, 3. The electroslag welding apparatus according to claim 2, wherein the sliding plate and the welding torch are fixed to the carriage.

5. The electroslag welding device according to any one of claims 1 to 4, further comprising a groove tracking mechanism capable of automatically adjusting the position of the tip of the welding torch in the groove width direction according to the shape of the groove.

6. 5. The electroslag welding apparatus according to claim 1, wherein the welding power sources used for the welding torches are all inverter-controlled digital power sources.

7. 5. The electroslag welding apparatus according to claim 1, wherein the welding wire is a solid wire or a cored wire having a diameter of 1 to 2 mm.

8. 5. The electroslag welding apparatus according to claim 1, further comprising a wire straightener at a connection between the welding torch and the conduit cable.

9. 5. The electroslag welding apparatus according to claim 1, wherein the apparatus is configured to supply flux between two welding wires fed from the two welding torches, respectively.

10. 1. An electroslag welding method for performing vertical up welding, comprising: When welding using two welding torches with the same polarity, The distance from the lower end of the contact tip provided on each of the two welding torches to the molten slag surface is 20 to 150 mm, The distance between the two welding wires fed from each of the two welding torches on the molten slag surface is set to 40 mm or less, Electroslag welding method characterized in that welding is performed while simultaneously swinging both of the two welding torches horizontally while maintaining a constant distance between them.

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