JP2007253196A - Method of and apparatus for seal-welding pipe end - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of and an apparatus for seal-welding a pipe end by which a welding operation can be leaved and defects of welding can be reduced. <P>SOLUTION: In the pipe end seal-welding method, by which a heat transfer pipe 5 is horizontally inserted into each pipe hole 41 of a vertically provided pipe plate 4 and the pipe end 51 around each pipe hole 41 is subjected to TIG welding, the distance of an electrode 21 to the pipe end 51 is beforehand set, further, the arc voltage at the position of the electrode is memorized as standard arc voltage, thereafter, upon welding, arc voltage is sampled, further, the sampled arc voltage and the standard arc voltage are compared, and, when the difference between both the arc voltages exceeds a prescribed determination voltage difference, the welding is interrupted. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tube end seal welding method and apparatus applied to manufacture of a pressure vessel, a heat exchanger, and the like, and relates to determination of electrode wear and an automatic stop function during welding associated therewith.

  Generally, a pressure vessel or a heat exchanger is known in which a large number of tubes are arranged between a pair of opposed tube plates. When manufacturing the heat exchanger, a pipe is fitted into an insertion hole provided in the pipe plate, and the end of the pipe is sealed and welded.

  Patent document 1 and patent document 2 propose a pipe end seal welding apparatus for welding such pipe ends.

  In the tube end seal welding apparatus, for example, GTAW (Gas Tungsten Arc Welding, TIG welding) is performed in which an arc is generated from a tungsten electrode to a base material and welding is performed by adding a welding wire (filler material). .

  In the TIG welding, the electrode may be consumed and deteriorated due to contact with the welding wire, and the tip portion of the electrode may be damaged. When such a defect occurs, the concentration of the welding arc is impaired, often resulting in poor welding and welding defects.

  Therefore, in order to ensure quality, it is necessary that the tip portion of the electrode be kept in a normal shape.

  Conventionally, in TIG welding, a welder constantly checks the tip of the electrode visually during welding.

JP 2003-88956 A JP 2001-150132 A

  However, since the welder directly monitors the welding state in such a manner, for example, even if the pipe end seal welding apparatus itself is automated, the constant monitoring of the electrodes cannot be automated. It will be a big factor that hinders the abandonment.

  In addition, since monitoring depends on human factors, there is a limit to the monitoring capability, and the missing state of the electrode tip is overlooked.

  For example, in the pipe end welding operation in the above-described heat exchanger or the like, the welding time per individual joint is about 90 seconds, but there are as many as 20,000 joints in one tube sheet. In the tube end welding operation, if the welding operation is continuously performed while overlooking the defect state of the tip of the electrode, defective welding frequently occurs at the time when a failure is noticed. This is often the case.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pipe end seal welding method and a pipe end seal welding apparatus that can solve the above-described problems and can allow welding work to be left and welding defects to be reduced.

  In order to achieve the above object, the present invention provides a tube end seal welding method in which a heat transfer tube is horizontally inserted into each tube hole of a vertically provided tube plate, and the tube end around the tube hole is TIG welded. The distance of the electrode with respect to the tube end is set in advance, the arc voltage at the electrode position is stored as a reference arc voltage, and then the arc voltage is sampled at the time of welding, and the sampled arc voltage and the reference arc voltage are sampled. And the welding is interrupted when the difference between both arc voltages exceeds a predetermined judgment voltage difference.

  Preferably, the tube end is divided into a plurality of portions in the circumferential direction of the heat transfer tube to set a welding region, and the reference arc voltage is stored for each of the welding regions.

  Preferably, welding is interrupted when a state where the difference between the sampled arc voltage and the reference arc voltage exceeds the determination voltage difference continues for a predetermined time or more.

  Preferably, the welding is performed by supplying a rectangular wave pulse having a peak portion and a base portion to the electrode, and the arc voltage is increased from the central portion to the peak portion of the base portion of the rectangular wave pulse. It is detected in the section.

  In order to achieve the above object, the present invention provides a tube end seal welding apparatus in which a heat transfer tube is inserted horizontally into each tube hole of a vertically provided tube plate, and the tube end around the tube hole is TIG welded. Detection means for detecting the arc voltage between the electrode and the tube end, electrode setting means for setting the distance of the electrode with respect to the tube end in advance, and the arc voltage at the electrode position set by the electrode setting means Is stored as a reference arc voltage, and at the time of welding, the detection means samples the arc voltage, and compares the sampled arc voltage with the reference arc voltage stored in the storage means, And an abnormal stopping means for interrupting welding when a difference between both arc voltages exceeds a predetermined determination voltage difference.

  Preferably, the abnormal stop means is provided with a storage switch for operating the storage means, an input device for inputting and setting the judgment voltage difference, and a display device for notifying the interruption of welding. It is a thing.

  According to the present invention, it is possible to achieve an excellent effect that it is possible to leave the welding work and reduce welding defects.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  The pipe end seal welding apparatus and the pipe end seal welding method of the present embodiment include, for example, a pressure vessel or a heat exchanger in which a large number of heat transfer tubes (hereinafter referred to as tubes) are arranged between a pair of opposed tube plates. In manufacturing, it is used to weld the tube to the tube sheet in a tube end seal.

  First, the pipe end seal welding apparatus of this embodiment will be described with reference to FIGS. 1 and 2.

  As shown in FIG. 1, a pipe end seal welding apparatus 1 controls a pipe end seal welding apparatus 1 while supplying a welding head 2 having an electrode 21, power, shield gas, cooling water, and the like to the welding head 2. Control power supply device (power supply) 3 for the purpose.

  By supplying electric power from the control power supply device 3 to the electrode 21 of the welding head 2, an arc is generated between the electrode 21 and the base material to weld the base material. More specifically, as shown in FIG. 2, the tube end seal welding apparatus 1 inserts the heat transfer tubes 5 horizontally into the respective tube holes 41 of the tube plate 4 provided vertically, and around the tube holes 41. The pipe end 51 is TIG welded.

  The welding head 2 includes a mandrel 22 inserted into a tube 5 fitted in a tube plate 4 provided vertically, a torch 23 provided to be rotatable around the mandrel 22, and held by the torch 23. Electrode 21, an electrode turning device 24 (see FIG. 1) for turning the electrode 21 and the torch 23 in a vertical plane, and a wire coil for supplying a wire (melting material) 251 to the tip of the torch 23 And a mounting portion 25 (see FIG. 1).

  The electrode turning device 24 is provided with an electrode turning position sensor (not shown) for detecting the turning position of the electrode 21, and a detection signal of the electrode turning position sensor is input to the control power supply device 3.

  The torch 23 includes an electrode holder 231 that holds the electrode 21, and electrode setting means 232 for moving the electrode holder 231 in the front-rear direction (the axial direction of the mandrel 22, the left-right direction in FIG. 2).

  The electrode setting means 232 includes a slider 233 to which the electrode holder 231 is fixed and movable in the front-rear direction, and a drive means (motor in the illustrated example) 234 for driving the slider 233 and the electrode 21 in the front-rear direction.

  With the above electrode setting means 232, the position of the electrode 21 with respect to the tube end 51 is set.

  In the present embodiment, the electrode 21 is made of a tungsten electrode, and TIG welding is performed. TIG welding is performed by generating an arc from the electrode 21 to the base materials 4 and 5 and adding a welding wire 251 (melting material).

  During the welding, abnormalities occur at the tip of the electrode 21, such as the loss of the electrode 21 as shown in FIG. 4 and the attachment of the welding wire 251 to the electrode 21 as shown in FIG. There is a case.

  Here, as shown in FIG. 4, when the electrode 21 is consumed or missing, the arc length between the electrode and the base material becomes longer and the arc voltage becomes higher. On the other hand, as shown in FIG. 5, when the welding wire 251 adheres to the electrode 21, the state between the electrode and the base material is close to a short circuit, and the arc voltage is lowered.

  Therefore, the inventor of the present application pays attention to the fact that the abnormality of the tip of the electrode 21 (defect or adhesion of the welding wire 251) affects the welding voltage signal (arc voltage), and uses the change in the welding voltage signal. Thus, when the arc voltage value deviates from the appropriate range, the pipe end seal welding apparatus 1 and method for detecting the occurrence of an abnormality in the electrode 21 and automatically stopping it are devised.

  That is, the pipe end seal welding apparatus 1 of the present embodiment includes a detection means for detecting an arc voltage between the electrode 21 and the pipe end 51 and an electrode setting means for setting the distance of the electrode 21 with respect to the pipe end 51. 232, storage means for storing the arc voltage at the electrode position set by the electrode setting means as a reference arc voltage, and at the time of welding, the arc voltage is sampled by the detection means, and the sampled arc An abnormal stop means for interrupting welding when the voltage is compared with the reference arc voltage stored in the storage means and the difference between the two arc voltages exceeds a predetermined determination voltage difference.

  In the present embodiment, the control power supply device 3 serves as detection means, storage means, and abnormal stop means.

  The control power supply device 3 is connected to the welding head 2 via a plurality of cables so as to transmit and receive signals and supply power, cooling water, shield gas, and the like.

  More specifically, as shown in FIG. 1, the control power supply device 3 includes a pair of power cables 31 and 32 for supplying power to the electrode 21 and the base material, and a nipple 311 to each power cable 31 and 32. , 321 and a pair of detection cables 33 and 34 for detecting an arc voltage between the electrode 21 and the base metals 4 and 5, a signal cable (not shown), a cooling water cable, a shield gas cable, etc. Is provided.

  For example, the control power supply device 3 supplies electric power (current) as a rectangular wave pulse as shown in FIG. 6 and detects an arc voltage as a rectangular wave pulse (see FIG. 7) synchronized with the supplied electric power. .

  Returning to FIG. 1, the control power supply device 3 is provided with a memory 35 for storing the detected arc voltage and a predetermined determination voltage difference. The memory 35 stores a program for detecting the arc voltage, storing the reference arc voltage, and stopping welding when the electrode is abnormal.

  The control power supply 3 is provided with a storage switch for operating the storage means, an input device for inputting and setting the determination voltage difference, and a display device for notifying the interruption of welding. Specifically, the control power supply device 3 is provided with a touch panel 36 serving as an input device and a display device. The control power supply 3 is connected to a remote control BOX 37 provided with an electrode exchange switch 371 for allowing the control power supply 3 to recognize the exchange of the electrode 21, and the electrode exchange switch 371 serves as the storage switch.

  Next, a pipe end seal welding method using the pipe end seal welding apparatus 1 of the present embodiment will be described based on FIGS.

  First, the outline of the pipe end seal welding method of this embodiment will be described.

  As shown in FIG. 2, in the tube end seal welding method of the present embodiment, the heat transfer tube 5 is horizontally inserted into each tube hole 41 of the tube plate 4 provided vertically, and the tube end 51 around the tube hole 41 is inserted. TIG welding. Specifically, the distance of the tungsten electrode 21 with respect to the tube end 51 is set in advance, the arc voltage at the electrode position is stored as a reference arc voltage, and then the arc voltage is sampled at the time of welding. The measured arc voltage is compared with the reference arc voltage, and the welding is interrupted when the difference between both arc voltages exceeds a predetermined judgment voltage difference.

  Further, in the present embodiment, welding is interrupted when a state where the difference between the sampled arc voltage and the reference arc voltage exceeds the determination voltage difference continues for a predetermined time or longer.

  Thereby, abnormality of the electrode 21 can be detected reliably, and welding is interrupted at the time of the abnormality, so that welding defects can be reduced.

  In this embodiment, tube end welding is performed by inserting a mandrel 22 into a tube 5 inserted in a vertical tube sheet 4 and turning the electrode 21 around the mandrel 22 in a vertical plane.

  Here, when the electrode 21 is swung in the vertical plane and the pipe end 51 is welded, the influence of gravity acting on the molten pool of the base material differs depending on the swivel angle of the electrode 21 (the circumferential position of the tube 5). For example, in FIG. 3, at the lower position (reference numeral w6 and reference numeral w7), the molten pool becomes drooping due to gravity, and the distance between the molten pool (base material) and the electrode 21 is shortened. On the other hand, the distance between the molten pool (base material) and the electrode 21 becomes longer at the position on the upper side (reference number w2 and reference number w3).

  Thus, since the state of the molten pool (base material) differs depending on the turning angle of the electrode 21, even when the electrode 21 is normal, the arc voltage between the electrode 21 and the base materials 4, 5 differs depending on the turning angle. It will be.

  Therefore, in the present embodiment, the pipe end 51 is divided into a plurality (eight in the illustrated example) in the circumferential direction of the pipe 5 to set the welding areas w1 to w8, and for each of the welding areas w1 to w8. The reference arc voltage is stored.

  Thereby, at the time of pipe end welding, it is possible to discriminate between a change in arc voltage due to the turning position of the electrode 21 and a change in arc voltage due to electrode abnormality, and it is possible to prevent erroneous detection of electrode abnormality.

  Next, an example of detecting an electrode abnormality by the tube end seal welding method of the present embodiment will be described.

  In the example described below, in order to detect the consumption of the tungsten electrode 21, a change in arc voltage after electrode replacement is detected, and the fluctuation range of the arc voltage exceeds a predetermined set value (determination voltage difference). In this case, it is determined that the electrode is consumed and an abnormal state is recognized, and the pipe end seal welding apparatus 1 is automatically stopped.

  First, an operator such as a welder presets a determination voltage difference for determining electrode abnormality using the touch panel 36 of the control power supply device 3. The determination voltage difference is stored in the memory 35 of the control power supply device 3. Further, the operator sets the distance of the electrode 21 with respect to the tube end 51 by the electrode setting means 232. This distance is adjusted and determined in advance by a welder or the like so that welding is performed appropriately.

  Next, pipe end welding is performed using the electrode 21 in a normal state (for example, the electrode 21 immediately after replacement), and the arc voltage (electrode 21-base material 4, 5) when the steady state (see FIG. 6) is reached. Is stored as a reference arc voltage.

  Specifically, after the electrode replacement, the operator presses the electrode replacement switch 371 of the remote control BOX 37 to cause the control power supply device 3 to recognize the replacement. The control power supply 3 that has recognized the replacement of the electrode 21 performs tube end welding at the electrode 21 immediately after the replacement, and detects the arc voltage between the electrode 21 and the base materials 4 and 5 at the time of the welding. Furthermore, when the detected arc voltage is in a steady state, the control power supply device 3 stores the arc voltage in each of the welding regions w1 to w8 (see FIG. 3) as a reference arc voltage.

  As described above, the control power supply device 3 of the present embodiment automatically reads the arc voltage during welding, and automatically uses the read arc voltage as a reference arc voltage (a voltage in a good state) for determining electrode wear. Thus, it is set and stored in the control power supply 3 (memory 35).

  Next, the control power supply device 3 compares the stored reference arc voltage with the arc voltage sampled during welding (hereinafter referred to as an actual arc voltage), and whether or not the voltage difference exceeds the determination voltage difference. Determine whether.

  Specifically, the control power supply device 3 sets the sampling interval to 10 msec and samples the actual arc voltage. When the voltage difference between the actual arc voltage and the reference arc voltage becomes equal to or greater than the determination voltage difference five times in succession, the control power supply device 3 determines that the electrode is abnormal and performs a welding operation (for example, the electrode 21 and the base material). The power supply to 4, 5 and the turning drive of the electrode 21) are stopped in accordance with the emergency stop.

  That is, in this embodiment, when the state where the voltage difference between the actual arc voltage and the reference arc voltage exceeds the determination voltage difference continues for 50 msec, the welding is temporarily suspended.

  Further, as shown in FIG. 1, the control power supply device 3 displays a message of “abnormal consumption of tungsten electrode” on the touch panel 36 in order to inform the operator that an abnormality has occurred in the electrode 21.

  Based on the display, if an abnormality has occurred in the electrode, the operator replaces the electrode 21, and after replacing the electrode, the operator presses the electrode replacement switch 371 of the remote control BOX 37, so that the above-described welding operation is performed. Is resumed. When there is no abnormality in the electrodes, the determination voltage difference is set larger than the current value.

  Next, detection of the reference arc voltage and the actual arc voltage will be described with reference to FIGS.

  As shown in FIG. 6, the pipe end welding of this embodiment is performed by supplying a rectangular wave pulse (pulse current) having a peak portion 61 and a base portion 62 to the electrode 21 and the base materials 4 and 5. For example, in the illustrated example, a pulse having a peak time / base time of 0.2 sec / 0.2 sec is used. The pulse becomes t0 after the start of welding, and passes through slope-up sections t1 to t2, and then reaches a steady state t2 to t3.

  The control power supply device 3 starts and ends the operation for determining the abnormality of the electrode 21 only in the steady state peak current and base current sections t2 to t3, and in the slope up sections t1 to t2 and the slope down sections t3 to t4. ,Not performed. That is, the control power supply device 3 detects the reference arc voltage and the actual arc voltage in the steady state t2 to t3.

  Further, as shown in FIG. 7, the control power supply device 3 detects the arc voltage at the second half 621 of the base portion 62 of the rectangular wave pulse. More specifically, the arc voltage is detected in a section 621 from the center portion of the base portion 62 of the rectangular wave pulse to the rise to the peak portion 61. Thereby, the falling slope 622 can be excluded from the arc voltage detection value, and erroneous detection due to noise at the beginning of the falling can be excluded.

  As described above, in this embodiment, the control power supply device 3 detects an electrode abnormality based on the arc voltage and automatically stops the pipe end seal welding device 1, so that monitoring work by a person can be omitted, It can be neglected and can reduce welding defects.

  In addition, when a system for monitoring the electrode 21 is configured outside the pipe end seal welding apparatus 1 by using an electric signal called arc voltage (welding voltage) that can be easily detected and acquired during welding. Compared with, it can be configured easily.

  In addition, the control power supply device 3 and the program that the pipe end seal welding apparatus 1 originally has can be used in the system as it is, and the pipe end seal welding apparatus 1 can be simplified and reduced in cost.

  Further, by using the arc voltage, the pulse signal (rectangular wave pulse) on the secondary side of the power source supplied to the electrode 21 and the base materials 4 and 5 and sampling can be completely synchronized, and signals necessary for abnormality detection Can be obtained without waste, and a signal with unnecessary noise can be eliminated, thereby improving detection accuracy.

  Here, in order to confirm the operation and effect of the pipe end seal welding apparatus 1 and the pipe end seal welding method of the present embodiment, verification by a welding mock-up test was performed. Thereby, the following results (1) to (3) were obtained.

  (1) We witnessed that the pipe end seal welding device outputs an abnormal stop signal.

  (2) When the fluctuation of the arc voltage is about 1V, it was confirmed that the electrode abnormality was sufficiently detected and the stop operation was normally performed.

  (3) By detecting the voltage fluctuation only at the base of the rectangular wave pulse and in the half length of the latter half of the rectangular wave parallel part in order to exclude the falling slope, the abnormality of the electrode can be further detected. It was detected effectively. In addition, by using the control power supply device for the pipe end seal welding device in combination, the pulse signal control and the detection operation are coordinated.

  In addition, this invention is not limited to the above-mentioned embodiment, Various modifications and application examples can be considered.

  For example, in the above-described embodiment, each reference arc voltage is stored for each welding region. However, the present invention is not limited to this, and the reference arc voltage is common and a determination voltage difference is set for each welding region. Also good.

FIG. 1 shows a pipe end seal welding apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged detail view of part II in FIG. 3 is a view in the direction of the arrow III in FIG. FIG. 4 is a diagram for explaining a state in which an electrode is missing. FIG. 5 is a diagram illustrating a state in which the welding wire is attached to the electrode. FIG. 6 is a diagram illustrating a rectangular wave pulse supplied by the control power supply device of the present embodiment. FIG. 7 is an enlarged detailed view of an arc voltage waveform corresponding to the VII portion of FIG.

Explanation of symbols

1 Pipe end seal welding device 3 Control power supply device (detection means, storage means, abnormal stop means)
4 Tube plate 5 Heat transfer tube 21 Electrode 41 Tube hole 51 Tube end 232 Electrode setting means

Claims (6)

In the tube end seal welding method in which a heat transfer tube is inserted horizontally into each tube hole of the tube plate provided vertically, and the tube end around the tube hole is TIG welded.
While setting the distance of the electrode with respect to the tube end in advance, the arc voltage at the electrode position is stored as a reference arc voltage,
Thereafter, during welding, the arc voltage is sampled, the sampled arc voltage is compared with the reference arc voltage, and the welding is interrupted when the difference between both arc voltages exceeds a predetermined judgment voltage difference. Pipe end seal welding method.   The tube end seal welding method according to claim 1, wherein the tube end is divided into a plurality of portions in the circumferential direction of the heat transfer tube, a welding region is set, and the reference arc voltage is stored for each of the welding regions.   The tube end seal welding method according to claim 1 or 2, wherein welding is interrupted when a state in which a difference between the sampled arc voltage and the reference arc voltage exceeds the determination voltage difference continues for a predetermined time or longer.   The welding is performed by supplying a rectangular wave pulse having a peak part and a base part to the electrode, and the arc voltage is in the interval from the central part to the peak part in the base part of the rectangular wave pulse. The pipe end seal welding method according to claim 1, wherein the pipe end seal welding method is detected. In the tube end seal welding device that inserts a heat transfer tube horizontally into each tube hole of the tube plate provided vertically, and TIG welds the tube end around the tube hole,
Detection means for detecting an arc voltage between the electrode and the tube end;
Electrode setting means for setting the distance of the electrode with respect to the tube end in advance;
Storage means for storing the arc voltage at the electrode position set by the electrode setting means as a reference arc voltage;
At the time of welding, the arc voltage is sampled by the detecting means, and the sampled arc voltage is compared with the reference arc voltage stored by the storing means, and the difference between both arc voltages exceeds a predetermined judgment voltage difference. A tube end seal welding apparatus characterized by comprising an abnormal stopping means for interrupting welding. The abnormal stop means is provided with a storage switch for operating the storage means, an input device for inputting and setting the judgment voltage difference, and a display device for notifying the interruption of welding. 5. The pipe end seal welding apparatus according to 5.

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