JP6460910B2 - Electroslag welding method and electroslag welding apparatus - Google Patents

Description

  The present invention relates to an electroslag welding method and an electroslag welding apparatus.

  In recent years, the plate thickness tends to increase as the size of structures increases in the shipbuilding and industrial machinery fields. Upright welding of these structures has been performed by highly efficient electrogas arc welding. However, there are problems in the work environment such as arc radiant heat, fume, and spatter for the welding operator, and problems such as the deterioration of the shield and the mechanical performance of the welded part have become apparent as the plate thickness increases. It was.

  On the other hand, there is electroslag welding using Joule heat of molten slag as a heat source. In electroslag welding, heat is generated not in the exposed arc but in the molten slag to melt the wire and base material, so there is no arc radiant heat and less fume and spatter are generated, improving the working environment. Become. Also, since the weld metal is shielded from the atmosphere with molten slag, no shielding gas is required, and even if the plate thickness increases, the shielding effect does not deteriorate, and the penetration of nitrogen and other elements in the atmosphere into the molten metal is prevented. Since it can be effectively prevented regardless of the thickness, mechanical deterioration of the weld metal does not occur.

  On the other hand, electrogas arc welding can monitor the penetration state of the molten pool and the base material, but electroslag welding confirms the penetration state because the molten pool and the base metal melted part are covered with molten slag. Can not do it. Whether or not sound penetration has been obtained can be confirmed for the first time by destroying the hardened slag covering the bead with a hammer and visually observing the bead.

Further, sound penetration is important not only because whether or not poor penetration occurs but also because the mechanical properties of the weld metal depend on the degree of penetration. In other words, the chemical composition of the weld metal is determined by the chemical composition of the welding wire, the chemical composition of the base metal, and the penetration ratio, but the chemical composition of the welding wire is different from the chemical composition of the base metal. As the ratio changes, the chemical composition of the weld metal changes, which affects the mechanical properties of the weld metal. Therefore, it is important to perform welding while keeping the penetration ratio as constant as possible.
Factors affecting penetration are slag bath depth in electroslag welding in addition to welding current, welding voltage, wire protrusion length, and the like. Although welding current, welding voltage, wire protrusion length, and the like are parameters that can be easily managed, it is difficult to measure and control the slag bath depth.

  Here, for example, in Patent Document 1, as conventional electrogas arc welding, while supplying a flux-cored wire to a groove extending in the vertical direction z of a steel plate erected substantially vertically, welding is performed in an upward direction. In the electrogas welding apparatus, a first electrode whose tip enters the groove, and a second electrode which enters the groove closer to the groove opening side in the plate thickness direction x than the tip of the first electrode in the groove. A trolley including a driving motor and rising along the groove, and a vertical electrogas welding provided with oscillating means supported by the trolley and driven to swing the first and second electrodes in the plate thickness direction x. An apparatus is disclosed.

  Further, in Patent Document 1, as welding progresses, molten metal is formed in the groove, and further, molten slag accumulates on the groove, and the surface rises and protrudes from the welding torch. It is described that when the protrusion length of the power supply becomes shorter and the current value between the power supply circuit and the vertical plate rises above a predetermined value, an instruction to raise is given to the carriage. Furthermore, the molten slag on the molten pool sequentially flows between the sliding copper plating and the weld bead as the sliding copper plating covering the opening of the groove rises as welding progresses, and welding is performed. It is described that it solidifies on the bead and is consumed by this.

  Further, for example, in Patent Document 2, as conventional electroslag welding, in a non-consumable nozzle type two-electrode electroslag welding in which a groove surrounded by a base metal and a base material is welded simultaneously with two electrodes, two electrodes The feed nozzles are simultaneously swung in the same direction in the arrangement direction, stopped near the open tip and the groove center, and the current energy Wm when the feed nozzle is swung and the current energy Wh when the open tip is stopped And the current energy Wc at the time of stopping near the center of the groove is set to Wc <Wm <Wh, and the power supply nozzle is pulled up and driven so as to maintain the welding wire protrusion length at which the welding current becomes the target current value. A nozzle-type two-electrode electroslag welding method is disclosed.

  Further, in Patent Document 2, welding is performed on a groove surrounded on all sides by a metal base and a base metal, and a manganese dioxide system is used at the start of welding so that a slag bath depth during welding is 15 mm. It is described that the flux is charged.

JP-A-10-118771 Japanese Patent Laid-Open No. 5-42377

  Electroslag welding has features such as no arc radiant heat and less generation of fumes and spatters compared to electrogas arc welding. However, in the conventional electroslag welding, the electrode is hung from the upper side to the groove surrounded on all sides by the steel plate, so that the slag is not consumed and the appropriate slag bath depth is maintained. The larger the base material, the worse the workability, and the size of the base material that can be welded is limited according to the size of the nozzle. For this reason, electroslag welding has been generally used when, for example, building steel having a length of several meters is welded. On the other hand, if a base metal is slid using a carriage as in electrogas arc welding, welding to a larger base metal is possible, but in this case, welding is performed on a groove surrounded on all sides by a steel plate. Therefore, the slag flows and flows between the sliding metal pad and the weld bead.

  Therefore, when electroslag welding is performed using a sliding pad, in order to ensure sound penetration, a flux is added from the top to compensate for slag consumption, and the slag bath depth is reduced. It is required to keep it as constant as possible. Basically, a slag bath can be made constant by adding a flux corresponding to the amount of wear, but as the groove width increases, the bead width increases and the amount of slag consumption increases. Further, the slag flow changes depending on the temperature of the contact metal, and the amount of wear changes. Furthermore, the amount of wear also changes when the gap between the backing metal and the base material changes or when the welding speed changes.

As described above, in electroslag welding using a sliding contact metal, since the slag consumption changes due to various factors, the flux input amount must be changed, but the slag bath depth is measured. It is difficult to do this, and the amount to be input must be observed and estimated by the welding operator. Therefore, it depends on the skill and inference force of the welding operator, and it is extremely difficult to keep the slag bath depth at a predetermined depth and make the penetration sound. In addition, penetration changes not only cause weld defects, but also adversely affect the mechanical properties of the weld metal.
As described above, when electroslag welding is performed using a sliding-type pad by the methods shown in Patent Document 1 and Patent Document 2, the slag bath depth changes, which affects the penetration and mechanical properties of the weld metal. Unfortunately, the welding workability is excellent, but unfortunately it was not applicable to long-line welding.

  The present invention relates to electroslag welding using a sliding metal pad, welding while maintaining a slag bath depth at a predetermined depth, ensuring sound penetration and deteriorating the mechanical properties of the weld metal. The purpose is to prevent.

For this purpose, in the electroslag welding, the present invention sets the wire feed speed and the reference current value on the basis of a predetermined relationship between the wire feed speed and the reference current value. the length of the welding wire to the slag bath supplies the flux so that the length predetermined by the welding torch slidingly straps as welding current becomes a predetermined relationship to the reference current value This is an electroslag welding method in which welding is performed while adjusting the traveling speed of a traveling carriage equipped with the above and maintaining the slag bath depth at a predetermined depth.

From another point of view, the present invention relates to a welding torch having a contact tip for supplying power to a welding wire, a sliding contact, a traveling carriage equipped with the welding torch and the sliding application, and a traveling carriage control device. And a slag bath detector, a flux supply device, and a flux supply control device, and the slag bath detector is a slag bath when the slag bath rises to a position of a predetermined length from the tip of the contact tip. When the slag bath detector detects the slag bath, the flux supply control device detects the slag bath so that the length of the welding wire from the tip of the contact tip to the slag bath becomes a predetermined length. When the slag bath detector does not detect the slag bath, the flux supply device is controlled so as to supply the flux. The traveling speed of the traveling carriage is controlled so that the welding current has a predetermined relationship with respect to a reference current value determined according to the feeding speed, and welding is performed while maintaining the slag bath depth at a predetermined depth. It is an electroslag welding apparatus to be performed.
Further, as a predetermined relationship, the traveling carriage control device increases the traveling speed of the traveling carriage when the welding current becomes larger than the reference current value, and decreases the traveling speed of the traveling carriage when the welding current becomes smaller than the reference current value. It can be characterized by controlling to.
Furthermore, the slag bath detector can detect the slag bath by detecting the welding voltage when the detection terminal of the slag bath detector comes into contact with the slag bath.
The slag bath detector processes the detected welding voltage with a filter having a time constant of 1/2 to 2 times the weaving cycle, and determines whether or not a slag bath has been detected. can do.
Further, the detection terminal may be connected to a welding torch.
Furthermore, the slag bath detector applies a voltage from a DC power supply to the detection terminal of the slag bath detector through a resistor, and when the detection terminal comes into contact with the slag bath, the slag bath detector detects the slag bath by reducing the voltage of the detection terminal. Can be characterized.
And a slag bath detector has a photo sensor, can detect the light of a slag bath, and can be characterized by detecting a slag bath.
Further, the flux supply device may be characterized in that the flux is supplied by a valve driven by a solenoid.
Further, the flux supply device may be characterized in that the flux is supplied by a screw driven by a motor.
When the wire feed speed is changed, the reference current value is automatically changed based on a predetermined function indicating a relationship between the wire feed speed and the reference current value. be able to.
The reference current value can be obtained for each type by a function determined according to the type of the welding wire.

  According to the present invention, in electroslag welding using a sliding-type metal pad, welding is carried out while maintaining the slag bath depth at a predetermined depth, ensuring sound penetration and mechanical properties of the weld metal. Can be prevented.

It is a figure which shows an example of schematic structure of the electroslag welding apparatus which concerns on this Embodiment. It is the figure which looked at the electroslag welding apparatus shown in FIG. 1 from the T direction. It is a figure which shows the correlation of the depth of a molten slag bath, the length of a welding wire, welding current, and penetration width. It is a figure which shows the correlation of the depth of a molten slag bath, the length of a welding wire, welding current, and penetration width. It is a figure which shows the correlation of the depth of a molten slag bath, the length of a welding wire, welding current, and penetration width. It is a figure which shows the structural example of a molten slag bath detector. It is a figure which shows an example of the welding voltage distribution on the surface of a molten slag bath. It is a figure which shows an example of the welding voltage distribution of the molten slag bath surface at the time of rocking | fluctuating a welding torch in a plate | board thickness direction. It is a figure which shows an example of the welding voltage distribution of the molten slag bath surface at the time of rocking | fluctuating a welding torch in a plate | board thickness direction. It is a figure which shows an example of the welding voltage distribution of the molten slag bath surface at the time of rocking | fluctuating a welding torch in a plate | board thickness direction. It is a figure which shows the structural example which provided the filter circuit in the molten slag bath detection apparatus shown in FIG. It is a figure which shows an example of the welding voltage waveform when there is no filter circuit. It is a figure which shows an example of the welding voltage waveform at the time of passing through a filter circuit. It is a figure for demonstrating an example of the structure which connected the detection terminal to the welding torch. It is a figure which shows the other structural example of a molten slag bath detector. It is a figure which shows the other structural example of a molten slag bath detector. It is a figure which shows the structural example of a flux supply apparatus. It is a figure which shows the structural example of a flux supply apparatus. It is a figure which shows the other structural example of a flux supply apparatus. It is a figure which shows the comparison result with the case where a slag bath control is not carried out, and the case where a slag bath is controlled in this Embodiment. It is a figure for demonstrating the influence which slag bath depth has on welding.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Configuration of welding equipment>
First, the electroslag welding apparatus 100 according to the present embodiment will be described. FIG. 1 is a diagram illustrating an example of a schematic configuration of an electroslag welding apparatus 100 according to the present embodiment. In FIG. 1, the direction indicated by arrow Z is the upward direction in the vertical direction (up and down direction), the direction indicated by arrow X is the right direction in the plate thickness direction (left and right direction), and the surface from the back surface is perpendicular to the paper surface. The direction toward is the front side of the horizontal horizontal direction Y. 2 is a view of the electroslag welding apparatus 100 shown in FIG. That is, FIG. 2 is a view of the electroslag welding apparatus 100 as viewed from above. However, in FIG. 2, a welding torch 4, a flux supply device 14, a flux supply control device 15, a traveling carriage 16, a traveling carriage control device 17, and the like which will be described later are omitted.

  As shown in FIG. 1, the electroslag welding apparatus 100 according to the present embodiment includes a fixed copper plating 1 and a sliding copper plating 2, a welding torch 4, a molten slag bath detector 13, a flux A supply device 14, a flux supply control device 15, a traveling cart 16, and a traveling cart control device 17 are provided.

  In the electroslag welding apparatus 100, a fixed copper plating 1 is disposed on the back side of the groove, and a sliding copper plating 2 is disposed on the front side of the groove. Here, a backing material made of heat-resistant ceramics may be used in place of the back-side copper plating 1. The front-side sliding copper plating 2 is a copper plating that slides in the vertical direction and is water-cooled. However, instead of copper, the sliding copper plating 2 may be used.

  The welding torch 4 feeds the welding wire 6 with a welding current 8 supplied from a welding power source (not shown) to weld the welding base material 3. In addition, the welding torch 4 has a contact tip 5 that guides the welding wire 6 and supplies a welding current 8 to the welding wire 6.

The molten slag bath detector 13 detects the position of the molten slag bath 7.
The flux supply device 14 throws the flux 12 into the molten slag bath 7. Since the flux 12 is melted to form molten slag, the amount of the molten slag bath 7 is increased by introducing the flux 12.
The flux supply control device 15 controls the operation of the flux supply device 14 and adjusts the amount of the flux 12 put into the molten slag bath 7.

The traveling cart 16 is equipped with a sliding copper brazing metal 2, a welding torch 4, a molten slag bath detector 13, a flux supply device 14, a flux supply control device 15, and a traveling cart control device 17, and is directed upward (arrows). move in the direction indicated by z). In other words, the traveling carriage 16 moves together with the sliding copper plating 2, the welding torch 4, the molten slag bath detector 13, the flux supply device 14, the flux supply control device 15, and the traveling carriage control device 17. The relative positional relationship between them does not change. As the traveling carriage 16 rises, welding is performed along the upward direction.
The traveling cart control device 17 controls the operation of the traveling cart 16 by increasing or decreasing the traveling speed of the traveling cart 16.

  Then, the welding wire 6 is fed from the contact tip 5 of the welding torch 4 into the groove surrounded by the welding base material 3, the copper plating 1, and the sliding copper plating 2, and is formed in the groove. Into the molten slag bath 7. The welding current 8 flows from the welding wire 6 through the molten slag bath 7 to the molten metal 9. At this time, Joule heat is generated by the welding current 8 flowing through the molten slag bath 7 and the resistance of the molten slag bath 7, and welding proceeds while melting the welding wire 6 and the welding base material 3.

  As the welding progresses, the molten metal 9 is cooled to become the weld metal 10, and a part of the molten slag bath 7 is between the copper metal 1 and the weld metal 10 and between the sliding copper metal 2 and the weld metal. The molten slag layer is formed between the molten slag layer 10 and the molten slag layer is cooled to become the solidified slag 11. In this manner, the molten slag bath 7 becomes a solidified slag 11 that partially covers the bead surface, so that the molten slag bath 7 is consumed as the welding progresses, and the depth Ls of the molten slag bath 7 decreases. In order to compensate for the decrease in the molten slag bath 7, it is necessary to add an additional flux 12 that melts and becomes the molten slag bath 7.

  The amount of the solidified slag 11 covering the bead surface varies depending on the bead width and the width of the weld groove. Further, the amount of the solidified slag 11 varies depending on the adhesion degree of the copper plating 1 and the sliding copper plating 2 and the cooling state. Therefore, the amount of the solidified slag 11 is not constant, and the amount of the flux 12 to be input needs to be changed in order to keep the depth Ls of the molten slag bath 7 constant. However, since the depth Ls of the molten slag bath 7 is not known, the depth Ls of the molten slag bath 7 varies when the amount of the flux 12 is not appropriate.

  Therefore, in the present embodiment, control is performed to keep the depth Ls of the molten slag bath 7 constant. Here, “constant” is not limited to the case where the depth Ls of the molten slag bath 7 is always one value, and the depth Ls of the molten slag bath 7 shows a value within a certain range in consideration of errors. Is also included. That is, the depth Ls of the molten slag bath 7 is controlled so as to maintain a predetermined depth.

  The first requirement for making the depth Ls of the molten slag bath 7 constant is that the welding wire length Ld from the tip of the contact tip 5 to the upper surface of the molten slag bath 7 (hereinafter referred to as dry extension Ld). Control is made to have a predetermined length. The second requirement for making the depth Ls of the molten slag bath 7 constant is the relationship in which the welding current 8 is predetermined with respect to the reference current value determined according to the wire feed speed, that is, the reference The traveling carriage control device 17 controls the traveling speed of the traveling carriage 16 so that the current value and the welding current 8 are equal.

<Requirements to keep the depth of the molten slag bath>
First, the first requirement for making the depth Ls of the molten slag bath 7 constant will be described.
When the molten slag bath detector 13 does not detect the molten slag bath 7, that is, when the molten slag bath detector 13 is installed on the upper part of the sliding copper metal plate 2, the flux supply control device 15 When the upper surface of 7 is not touched, the flux supply device 14 is controlled so as to feed the flux 12. On the other hand, in the flux supply control device 15, when the molten slag bath detector 13 detects the molten slag bath 7, that is, the molten slag bath detector 13 installed on the upper part of the sliding copper plating 2 is melted. When it is in contact with the upper surface of the slag bath 7, the flux supply device 14 is controlled so as to stop the introduction of the flux 12. In this way, the flux supply device 14 inputs the flux 12 so that the molten slag bath detector 13 detects the molten slag bath 7, and adjusts the depth Ls of the molten slag bath 7.

  Here, the welding torch 4, the sliding copper pad 2, and the molten slag bath detector 13 are all mounted on the traveling carriage 16, and the relative positional relationship does not change even when the traveling carriage 16 moves. Therefore, the distance between the tip of the contact tip 5 and the molten slag bath detector 13 does not change. When the molten slag bath 7 rises to a position of a predetermined length from the tip of the contact tip 5 (that is, the position of the molten slag bath detector 13), the molten slag bath detector 13 is connected to the molten slag bath 7 Is detected. The flux supply control device 15 controls the amount of the flux 12 so that the molten slag bath detector 13 detects the molten slag bath 7, so that the distance from the tip of the contact tip 5 to the upper surface of the molten slag bath 7, that is, the dry The extension Ld is controlled to have a predetermined length.

Next, the second requirement for making the depth Ls of the molten slag bath 7 constant will be described.
FIGS. 3-1 to 3-3 are diagrams showing the correlation among the depth of the molten slag bath 7, the length of the welding wire 6, the welding current 8, and the penetration width. Here, as shown in FIGS. 3-1 to 3-3, in the state where the dry extension Ld is controlled to a predetermined length, the depth Ls of the molten slag bath 7 changes as Ls1>Ls2> Ls3. Then, the length in which the welding wire 6 is immersed in the molten slag bath 7 (hereinafter referred to as wet extension Lw) changes in proportion to Lw1>Lw2> Lw3, and the penetration width Lm is Lm1 <Lm2. <Lm3 changes. On the other hand, when the value of the welding current 8 is Iw, the relationship between the welding current Iw and the wire feed speed Vw is expressed by the following equation (1).

  In Equation 1, K1 to K4 are constants determined by the diameter, structure, and material of the welding wire 6.

  Furthermore, in the state where welding is performed with the wire feed speed Vw constant, the condition that the dry extension Ld is controlled to a predetermined length by the flux supply control device 15 as shown in the first requirement described above. Then, Formula 1 is expressed as the following Formula 2.

  That is, from Equation 2, the welding current Iw changes in inverse proportion to the wet extension Lw, and when the wet extension Lw increases, the welding current Iw decreases. As described above, since the depth Ls of the molten slag bath 7 is proportional to the wet extension Lw, the welding current Iw at the appropriate depth Ls2 of the molten slag bath 7 is set as the reference current value Iw2. Keep it. When the welding current Iw becomes larger than the reference current value Iw2 as welding progresses, it is determined that the depth Ls of the molten slag bath 7 is smaller than Ls2 and the penetration width Lm is larger than Lm2. Thus, the traveling carriage control device 17 increases the traveling speed of the traveling carriage 16. When the traveling speed of the traveling carriage 16 is increased, the wire protrusion length (Ld + Lw) is increased, and the welding current Iw is decreased to the reference current value Iw2. On the other hand, when the welding current Iw becomes smaller than the reference current value Iw2, it is determined that the depth Ls of the molten slag bath 7 is larger than Ls2 and the penetration width Lm is smaller than Lm2, and the traveling vehicle controller 17 Decreases the traveling speed of the traveling carriage 16.

  If it adds, first, the depth Ls of the molten slag bath 7 will be adjusted to Ls2 as a predetermined depth, and welding will be started. Further, the traveling speed of the traveling carriage 16 is determined in accordance with the magnitude of the welding current Iw. As the welding progresses, a part of the molten slag bath 7 becomes the solidified slag 11 and is consumed, so the depth Ls of the molten slag bath 7 decreases. When the molten slag bath detector 13 installed on the upper part of the sliding copper plating 2 decreases to such an extent that it does not contact the upper surface of the molten slag bath 7, the flux supply control device 15 supplies the flux 12 so that the flux 12 is introduced. The device 14 is controlled. When the molten slag bath detector 13 detects the molten slag bath 7, that is, the molten slag bath detector 13 installed on the upper part of the sliding copper plating 2 is melted. When it comes into contact with the upper surface of the slag bath 7, the flux supply device 14 is controlled so as to stop the charging of the flux 12. As described above, the distance from the tip of the contact tip 5 to the upper surface of the molten slag bath 7, that is, the dry extension Ld is controlled to be a predetermined length. On the other hand, since the welding current Iw in the case of an appropriate molten slag bath depth is set as the reference current value Iw2, if the dry extension Ld becomes constant by the above control, the wet extension Lw also becomes constant, and the slag bath depth It is also constant.

  Thus, the traveling vehicle controller 17 controls the traveling speed of the traveling vehicle 16 so that the welding current Iw becomes equal to the reference current value Iw2, so that the depth Ls of the molten slag bath 7 is an appropriate depth Ls2. Thus, an appropriate penetration width Lm2 can be obtained. In addition, a weld metal having stable mechanical properties can be obtained.

  In determining the reference current value Iw2, first, in the electroslag welding apparatus 100, when welding is performed with the wire feed speed Vw fixed using a certain welding wire 6, the dry extension Ld is controlled to a predetermined length. Is done. Here, when welding is performed using several types of welding currents Iw, welding with different wet extensions Lw and penetration widths Lm is performed. At this time, the welding current Iw when the optimum penetration width Lm2 is obtained is determined as the reference current value Iw2 of the wire feed speed Vw.

  Next, the wire feed speed Vw is changed, and similarly the optimum reference current value Iw2 is obtained. By repeating this, the reference current value Iw2 can be obtained as a function of the wire feed speed Vw. This function (function indicating the relationship between the reference current value Iw2 and the wire feed speed Vw) is stored in the traveling carriage control device 17, and the output of the wire feed speed setter or the detected value of the wire feed speed is obtained. If the control is performed to set the reference current value Iw2, the reference current value Iw2 is set according to the wire feed speed Vw. When the wire feed speed Vw is changed, the reference current value Iw2 is automatically changed according to the changed wire feed speed Vw. Then, welding can be automatically performed with the wet extension Lw (or the depth Ls of the molten slag bath 7) that automatically obtains the optimum penetration.

  Moreover, the reference current value Iw2 corresponding to the wire feed speed Vw can be obtained for various welding wires 6 by changing the welding wire 6 and performing the above procedure. Here, the reference current value Iw2 is obtained as a function of the wire feed speed Vw for each type of the welding wire 6 such as the diameter, structure, and material of the welding wire 6, for example. In addition, the function of the wire feed speed Vw is determined according to the type of the welding wire 6, and the reference current value Iw2 is obtained by a function for each type of the welding wire 6.

<Configuration of molten slag bath detector>
Next, the configuration of the molten slag bath detector 13 will be described in detail. FIG. 4 is a diagram illustrating a configuration example of the molten slag bath detector 13.
As shown in FIG. 4, the molten slag bath detector 13 according to the present embodiment includes a detection terminal 18, a differential amplifier 19, a contact determination reference signal setting device 20, and a comparator 21, and the detection terminal 18 is conductive. It is made of copper, which is a conductive metal, and is generally water-cooled. When the detection terminal 18 contacts the molten slag bath 7, it detects a part of the welding voltage.

The differential amplifier 19 receives the voltage of the detection terminal 18 and the voltage of the sliding copper pad 2 and outputs the difference between the two voltages. Since the sliding copper plating 2 is in contact with the weld base material 3, the voltage of the sliding copper plating 2 is the base material voltage.
The contact determination reference signal setting device 20 outputs a voltage that is about half of the voltage detected when the detection terminal 18 contacts the molten slag bath 7 as a reference signal. For example, FIG. 5 shows an example of the welding voltage distribution on the surface of the molten slag bath 7, but the detection terminal 18 normally detects a welding voltage of about 6 volts (unit of voltage: V). Half of the voltage is set to about 3V. When the detection terminal 18 is not in contact with the molten slag bath 7, the welding voltage is not applied to the detection terminal 18, so the voltage of the detection terminal 18 is 0V.

  The comparator 21 receives the output signal of the differential amplifier 19 and the reference signal of the contact determination reference signal setting unit 20, and the output signal of the differential amplifier 19 is larger than the reference signal of the contact determination reference signal setting unit 20. At this time, a signal determined that the detection terminal 18 and the molten slag bath 7 are in contact with each other is created. The generated signal is sent to the flux supply control device 15, and the flux 12 is supplied and stopped by the flux supply device 14, and the upper surface of the molten slag bath 7 is positioned at a predetermined length from the tip of the contact tip 5. The dry extension Ld is maintained at a predetermined length.

  FIGS. 6A to 6C are diagrams illustrating an example of a welding voltage distribution on the surface of the molten slag bath 7 when the welding torch 4 is swung in the plate thickness direction. First, the welding voltage distribution shown in FIG. 6B is that when the welding wire 6 is in the center of the plate thickness, and the welding voltage detected by the detection terminal 18 is about 6V. Therefore, when the welding torch 4 is swung in order to make the penetration in the plate thickness direction uniform and the welding torch 4 is in the vicinity of the copper plating 1, it is arranged in the vicinity of the sliding copper plating 2. As shown in FIG. 6A, the voltage detected by the detection terminal 18 is reduced to about 3V, which is half of 6V. On the other hand, as shown in FIG. 6-3, when the welding torch 4 comes near the sliding copper plating 2, the welding voltage detected by the detection terminal 18 becomes as high as about 12V.

Here, if the voltage of the reference signal of the contact determination reference signal setting unit 20 is set to about 1.5 V, the comparator 21 can correctly determine that the molten slag bath 7 and the detection terminal 18 are in contact with each other. Since the value of the reference signal is small, there is a possibility that correct determination cannot be made due to the welding state or external noise.
In order to prevent this erroneous detection, the molten slag bath detection device 13 has a filter circuit 22 installed after the differential amplifier 19 and has detected the molten slag bath 7 based on the welding voltage processed by the filter circuit 22. It may be determined whether or not. FIG. 7 is a diagram illustrating a configuration example in which a filter circuit 22 is provided in the molten slag bath detection device 13 illustrated in FIG. 4. The filter circuit 22 is desirably a filter circuit 22 having a time constant that is about the oscillation period of the welding torch 4, that is, about 1/2 to twice the period.

  FIG. 8 is a diagram illustrating an example of a welding voltage waveform when the filter circuit 22 is not provided, and FIG. 9 is a diagram illustrating an example of a welding voltage waveform when the filter circuit 22 is interposed. Specifically, the waveform shown in FIG. 8 is a welding voltage waveform detected without a filter having a sampling period of 250 ms. Further, the waveform shown in FIG. 9 is a welding voltage waveform of a moving average of 27 data, that is, a moving average of a section of 6.75 seconds (6750 ms). Here, one scale on the vertical axis indicates 3.000 V, and one scale on the horizontal axis indicates 1 second (sec). Further, in the example shown in FIGS. 8 and 9, the oscillation cycle of the welding torch 4 is 8 seconds, so that the welding voltage waveform is equivalent to the oscillation cycle of the welding torch 4.

  As is apparent from these welding voltage waveforms, when there is no filter, when the welding torch 4 is in the vicinity of the copper pad 1, the voltage detected by the detection terminal 18 decreases to about 3 V, and the welding torch 4 Is in the vicinity of the sliding copper plating 2, the detection voltage is about 12V. Further, the detected welding voltage has a large fluctuation. On the other hand, the welding voltage waveform through the filter is averaged in the range of 9V to 12V. Therefore, when the filter circuit 22 is used, the reference signal for contact determination can be set to 3V to 6V, and the risk of erroneous determination is greatly reduced. Here, an example using a time constant substantially equal to the oscillation period is shown, but the effect was confirmed even with a filter using a time constant of about 1/2 to twice the oscillation period.

  Further, the detection terminal 18 may be connected to the welding torch 4. FIG. 10 is a diagram for explaining an example of a configuration in which the detection terminal 18 is connected to the welding torch 4. In the example shown in FIG. 10, the configurations of the differential amplifier 19, the contact determination reference signal setting unit 20, the comparator 21, and the filter circuit 22 are the same as those shown in FIG. 7, but the detection terminal 18 is connected to the welding torch 4. It is connected. When the welding torch 4 swings, the detection terminal 18 also swings with the welding torch 4, so that the detection terminal 18 is always located in the vicinity of the welding wire 6. For this reason, referring to the welding voltage distribution shown in FIGS. 6-1 to 6-3, when the detection terminal 18 comes into contact with the molten slag bath 7, a welding voltage of about 24 V can be detected, and the welding torch 4 A substantially constant voltage can be detected regardless of the oscillation of the. Therefore, the risk of being affected by noise and the like is reduced.

<Other structural examples of molten slag bath detector>
Next, another configuration example of the molten slag bath detector 13 will be described. 11 and 12 are diagrams showing another configuration example of the molten slag bath detector 13.
In the example shown in FIG. 11, the molten slag bath detector 13 includes a detection terminal 18, a DC power supply 23, a resistor 24, a differential amplifier 19, a filter circuit 22, a contact determination reference signal setting device 20, and a comparator 21. Yes. The DC power supply 23 is a power supply of about 100V to 200V, for example, and the output of the DC power supply 23 is connected to the detection terminal 18 through the resistor 24. Here, the value of the resistor 24 is, for example, 20 kΩ to 500 kΩ.

When the detection terminal 18 is not in contact with the molten slag bath 7, no current flows, so that the voltage of the DC power source 23 is applied to the detection terminal 18. On the other hand, when the detection terminal 18 comes into contact with the molten slag bath 7, current flows from the detection terminal 18 through the molten slag bath 7 to the sliding copper pad 2, so that the voltage of the DC power supply 23 is dropped by the resistor 24 and detected. The voltage at the terminal 18 decreases to a part of the welding voltage, that is, about 3V to 12V. This change is determined by the differential amplifier 19, the filter circuit 22, the contact determination reference signal setting unit 20, and the comparator 21, and the molten slag bath 7 is detected. Since these operations are the same as those described above, description thereof will be omitted.
According to this method, the voltage of the detection terminal 18 when the detection terminal 18 and the molten slag bath 7 are not in contact is 100V to 200V, whereas the detection terminal 18 and the molten slag bath 7 are in contact with each other. Since the voltage of the detection terminal 18 is 3V to 12V and the difference between the two voltages is large, a reliable operation is expected.

  In the example shown in FIG. 12, the molten slag bath detector 13 is a photosensor that receives light emitted from the surface of the molten slag bath 7 and the light amount of the light receiver 25 is at a certain level. A light reception determination unit 26 for determining when The determination level of the light amount is determined in advance, and the angle of the light receiver 25 is adjusted so that the dry extension Ld has a target predetermined length. The determination result is sent to the flux supply control device 15, and the flux 12 is supplied so that the dry extension Ld is constant.

  In addition, when the light reception determination unit 26 determines that the light amount of the light receiver 25 has reached a certain level, the molten slag bath 7 has risen from the tip of the contact tip 5 to a position of a predetermined length. . In this case, since the dry extension Ld is equal to or shorter than a predetermined length, the flux supply control device 15 performs control so as to stop the introduction of the flux 12. On the other hand, when the light reception determining unit 26 determines that the light amount of the light receiving unit 25 has not reached a certain level, the molten slag bath 7 has not risen from the tip of the contact tip 5 to a position of a predetermined length. . In this case, the dry extension Ld is larger than a predetermined length, and the flux supply control device 15 performs control so that the flux 12 is introduced.

<Configuration of flux supply device>
Next, the configuration of the flux supply device 14 will be described in detail. FIG. 13A and FIG. 13B are diagrams illustrating a configuration example of the flux supply device 14.
As shown in FIG. 13A, in the flux supply device 14 according to the present embodiment, the solenoid 30 reciprocates as indicated by an arrow 28, so that the valve 30 is indicated as indicated by an arrow 31 around the rotation shaft 29. It rotates and the flux supply nozzle 32 opens and closes. By this operation, the flux 12 of the flux hopper 33 is supplied to the molten slag bath 7.

  Here, FIG. 13A shows a state where the flux supply nozzle 32 is closed. On the other hand, FIG. 13-2 shows a state in which the flux supply nozzle 32 is open. When the flux supply nozzle 32 is opened, the flux 12 of the flux hopper 33 is transferred to the molten slag bath 7 via the flux supply nozzle 32. Supplied.

<Other configuration examples of the flux supply device>
Next, another configuration example of the flux supply device 14 will be described. FIG. 14 is a diagram illustrating another configuration example of the flux supply device 14.
In the example shown in FIG. 14, in the flux supply device 14, the flux 12 is pushed out from the flux hopper 33 by the rotation of the screw 35 driven by the motor 34, and supplied to the molten slag bath 7 through a path not shown. Is done.

<Example>
Next, an experimental result is shown and the Example in this Embodiment is described. Note that the present embodiment is not limited to this example.
In the electroslag welding apparatus 100 shown in FIG. 1, a welding wire 6 of 1.6 mmφ is used, a wire feed speed of 15.4 m / min, a welding voltage of 42 V, and a reference current value of 380 A, a plate thickness of 60 mm and 20 ° V. Groove welding was performed. The tip base material distance was 45 mm. Moreover, welding was started at a slag bath depth of 25 mm. FIG. 15 shows a comparison result between the case where the slag bath is not controlled after the electroslag welding is stabilized (conventional method) and the case where the slag bath is controlled in the present embodiment. Here, the result of this embodiment is shown as an example, and the result of the conventional method is shown as a comparative example.

  FIG. 15 shows the distance that the traveling carriage 16 has risen as the distance after the electroslag welding has stabilized, and the evaluation results of “arc generation”, “surface bead width”, and “penetration” are shown at each distance. Show. In the “arc generation”, “x” was set when an arc was generated, and “x” was set when no arc was generated. In “penetration”, “X” was given when there was a penetration failure, and “◯” was given when there was no penetration failure. According to the results shown in FIG. 15, it can be seen that by controlling the molten slag bath 7, the penetration depth becomes substantially constant and the front bead width does not change greatly.

  Moreover, the welding result at the time of welding at the said wire feed speed using the electroslag welding apparatus 100 which concerns on this Embodiment, and changing slag bath depth is demonstrated. FIG. 16 is a diagram for explaining the influence of the slag bath depth on welding. FIG. 16 shows the evaluation results of “arc generation”, “surface bead width”, “penetration”, and “toughness” at each slag bath depth. In “toughness”, when the temperature was −20 degrees and the temperature was 39 J (joules) or more, “◯” was given, and when it was smaller than 39 J, “x” was given. According to the result shown in FIG. 16, it turns out that the appropriate slag bath depth in this case is 20-60 mm. Although only an example is shown here, workability varies depending on the type of flux, wire type, and welding voltage that are actually used in welding, and the appropriate flag bath depth also varies.

  Moreover, in this Embodiment, although the electroslag welding apparatus 100 decided to weld with 1 electrode, it is not restricted to such a structure, It is good also as welding with multiple electrodes.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to said embodiment. It will be apparent to those skilled in the art that various modifications and alternative embodiments can be made without departing from the spirit and scope of the invention.

DESCRIPTION OF SYMBOLS 1 ... Copper plating, 2 ... Sliding copper plating, 3 ... Welding base material, 4 ... Welding torch, 5 ... Contact tip, 6 ... Welding wire, 7 ... Molten slag bath, 8 ... Welding current, 9 ... Melting Metal: 10 ... Weld metal, 11 ... Solidified slag, 12 ... Flux, 13 ... Molten slag bath detector, 14 ... Flux supply device, 15 ... Flux supply control device, 16 ... Traveling cart, 17 ... Traveling cart control device, 18 DESCRIPTION OF SYMBOLS ... Detection terminal, 19 ... Differential amplifier, 20 ... Contact judgment reference signal setting device, 21 ... Comparator, 22 ... Filter circuit, 23 ... DC power supply, 24 ... Resistance, 25 ... Light receiver, 26 ... Light reception judgment device, 27 ... Solenoid, 28 ... Arrow, 29 ... Rotating shaft, 30 ... Valve, 31 ... Arrow, 32 ... Flux supply nozzle, 33 ... Flux hopper, 34 ... Motor, 35 ... Screw, 100 ... Electroslag welding equipment

Claims (12)

In electroslag welding,
Based on the predetermined relationship between the wire feed speed and the reference current value, set the wire feed speed and the reference current value,
Supply the flux so that the length of the welding wire from the contact tip tip to the slag bath becomes a predetermined length,
Adjust the speed of the traveling vehicle that the welding current is equipped with a welding torch so that the predetermined relationship with the sliding straps with respect to the reference current value,
An electroslag welding method for performing welding while maintaining a slag bath depth at a predetermined depth. A welding torch having a contact tip for supplying power to the welding wire, a sliding batten,
A traveling carriage equipped with the welding torch and the sliding-type stopper, a traveling carriage controller,
A slag bath detector, a flux supply device, and a flux supply control device;
The slag bath detector detects a slag bath when the slag bath rises to a position of a predetermined length from the tip of the contact tip,
The flux supply control device supplies the flux when the slag bath detector detects the slag bath so that the length of the welding wire from the tip of the contact tip to the slag bath becomes the predetermined length. And when the slag bath detector does not detect the slag bath, the flux supply device is controlled to supply the flux,
The traveling carriage control device controls the traveling speed of the traveling carriage so that a welding current has a predetermined relationship with respect to a reference current value determined according to a wire feeding speed,
An electroslag welding apparatus that performs welding while maintaining a slag bath depth at a predetermined depth. As the predetermined relationship, the traveling cart control device increases the traveling speed of the traveling cart when the welding current becomes larger than the reference current value, and when the welding current becomes smaller than the reference current value, The electroslag welding apparatus according to claim 2, wherein the electroslag welding apparatus is controlled so as to reduce a traveling speed. The electroslag welding apparatus according to claim 2, wherein the slag bath detector detects a slag bath by detecting a welding voltage when a detection terminal of the slag bath detector comes into contact with the slag bath. . The slag bath detector processes the detected welding voltage with a filter having a time constant of 1/2 to 2 times the weaving cycle, and determines whether or not a slag bath has been detected. The electroslag welding apparatus according to claim 4. The electroslag welding apparatus according to claim 4, wherein the detection terminal is connected to the welding torch. The slag bath detector applies a voltage from a DC power source to a detection terminal of the slag bath detector through a resistor, and when the detection terminal comes into contact with the slag bath, the voltage of the detection terminal decreases to reduce the slag bath. The electroslag welding apparatus according to claim 2, wherein the electroslag welding apparatus is detected. The electroslag welding apparatus according to claim 2, wherein the slag bath detector includes a photosensor, and detects slag bath by detecting light of the slag bath. The electroslag welding apparatus according to claim 2, wherein the flux supply apparatus supplies the flux by a valve driven by a solenoid. The electroslag welding apparatus according to claim 2, wherein the flux supply apparatus supplies a flux by a screw driven by a motor. When the wire feeding speed is changed, the reference current value is automatically changed based on a predetermined function indicating a relationship between the wire feeding speed and the reference current value. The electroslag welding apparatus according to claim 2. The electroslag welding apparatus according to claim 11, wherein the reference current value is obtained for each type by the function determined according to the type of the welding wire.