JP2014046316A - Arc welding method, and arc welding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To return to a good normal welding state again because a weld defect becomes unstable in arc welding because a molten state of a welded portion becomes unstable. In particular, in the case of perforation, since the molten state is greatly unstable, it is more difficult to return to a normal welding state again, and the hole tends to be long.
SOLUTION: The voltage at the time of arc welding is constantly monitored, and the perforation is detected by detecting the moment when a certain deviation or more has occurred from the specified value set from the data at the time of normal welding. Next, when a hole is detected, a command to lower the welding current is sent to the welding power source, or the electrode is moved away from the workpiece by a drive device that moves the electrode in the height direction, thereby reducing heat input and arc pressure. It stabilizes the welding state, suppresses the lengthening of the hole, and can return to the normal good welding state immediately after the hole is generated.
[Selection] Figure 3

Description

  The present invention relates to an arc welding method and an arc welding apparatus that suppress punching of a workpiece when performing arc welding.

  A conventional automatic welding apparatus includes a welding head, a welding electrode, a welding power source, a control device, and, if necessary, a wire feeding device, and performs welding within a range of conditions specified at an initial stage. Some welding power sources have an appropriate condition adjustment function while feeding back the welding current and welding voltage during welding. However, this is only a function to adjust the disturbance during normal welding, that is, slight deformation of material, presence of minute dirt, disturbance of wire feeding, etc., and adjustment for welding defects such as drilling. It is not a mechanism.

  Here, in the field of arc welding, it is known that the welding voltage is proportional to the distance between the electrode and the workpiece, and an invention in which various functions are added using this phenomenon has been made. For example, the method of detecting the welding voltage and adjusting the height of the welding head so that it becomes a constant voltage is known as AVC (Auto Voltage Control) control. -Means to keep the distance between workpieces constant.

  For example, in Patent Document 1, if a certain divergence occurs between a welding voltage obtained by detecting and averaging a voltage during welding at a certain sampling frequency and a voltage value determined as a reference, the electrode − In order to show that the distance between workpieces has changed more than a certain value, an invention has been made for an automatic welding device with automatic weld defect detection function that judges that some sort of welding defect has occurred and marks the weld defect location with a marking device. ing.

  Further, Patent Document 2 has a condition correcting function for detecting defects during welding by radiation and changing welding conditions according to the size and position of the detected defects.

JP-A-11-285824 JP 5-177351 A

  Even if the occurrence of a defect can be automatically judged in real time due to an abnormality in the welding voltage, if a welding defect occurs, the molten state of the weld becomes unstable, and it is difficult to return to a good normal welding state again. . In particular, the hole-drilling phenomenon that occurs when the melt melts or melts due to a joint defect, etc., makes the molten state unstable and unstable, making it more difficult to return to a good welded state again. There is a tendency to become longer.

  In addition, welding of thin plates requires a welding technique that is skilled in repair welding with a hole, and the longer the hole is, the more difficult the repair welding is, and the time required for repair is drastically increased. When repair welds become large, distortion due to thermal deformation increases, resulting in abnormal stress concentration and deformation modes in structures where stress is generated in welds such as pressure vessels, and repair welds greatly fall below the design strength. Quality as a product may not be ensured.

  Furthermore, depending on the state of welding, once a hole is made, the hole may continue to be repaired without returning to normal welding again, making repair impossible.

  Moreover, since the radiation generating apparatus is used in Patent Document 2, a radiation shielding facility is required, the apparatus is large and expensive, and since its practicality is low, a highly versatile and simple configuration is required. It is done.

  The arc welding method of the present invention is an arc welding method in which a welding head is equipped with a TIG electrode and a workpiece is arc-welded while measuring the welding voltage. When the welding voltage exceeds a predetermined voltage value, the welding current is usually set. The arc welding method is characterized in that arc welding is performed with a current value lower than the current value, and when the welding voltage returns to a predetermined voltage value or less, the welding current is returned to the normal current value and arc welding is performed. is there.

  The arc welding apparatus of the present invention includes a welding power source electrically connected to a TIG electrode provided on a welding head and a workpiece, a voltage measuring unit for measuring a welding voltage of the welding power source, and a welding voltage of a predetermined value. A control unit that reduces the welding current below the normal current value when the voltage value is exceeded, and returns the welding current to the normal current value when the welding voltage returns below the predetermined voltage value. An arc welding apparatus characterized by

  It is possible to detect perforation by fluctuations in the welding voltage, suppress the perforation from increasing, and quickly return to a normal welding state.

It is the schematic of the welding apparatus in Embodiment 1 of this invention. It is a schematic diagram which shows the electrode periphery at the time of perforation generation | occurrence | production. It is a flowchart which shows the control action in Embodiment 1 of this invention. It is the schematic of the welding apparatus in Embodiment 2 or 3 of this invention. It is a flowchart which shows the control action in Embodiment 2 of this invention. It is a flowchart which shows the control action in Embodiment 3 of this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram of a welding apparatus according to the first embodiment. The best mode of the present invention is to perform thin plate welding by through welding with a TIG (Tungsten Inert Gas) welding power source with the following configuration. The entire welding apparatus includes a welding power source 1, a welding head 2, a TIG electrode 3, a welding voltage detection line 4, a control mechanism 5, and a control command line 6. Reference numeral 7 denotes a workpiece, which is an object to be welded. The welding voltage detection line 4 is connected to the welding power source 1, acquires the voltage during welding in real time, and transmits it to the control mechanism 5. The control mechanism 5 determines the obtained voltage and sends a current change command to the welding power source 1.

  FIG. 2 is a schematic diagram showing the periphery of the electrode when a hole is generated. In arc welding, arc discharge concentrates on the workpiece 7 extending from the tip of the electrode 3 due to the straightness of the arc. For this reason, during normal welding, the distance 9 between the electrodes and the workpiece during normal welding is shown in FIG. In general, the higher the temperature of the metal, the lower the viscosity and the higher the fluidity. Therefore, the higher the temperature in welding, the more unstable the molten state. In addition, the arc pressure has a force to move the molten pool dynamically, which is also a factor that makes the molten state unstable. The extension from the tip of the electrode 3 where the arc discharge is concentrated is the portion where the temperature becomes the highest and the arc pressure becomes the highest. Usually, the perforation is located immediately below the electrode 3 where the arc discharge is concentrated. Occur. For this reason, the perforation 8 generated at the time of welding occurs in the vicinity of the electrode 3 and the work 7 is removed from the extended portion from the tip of the electrode 3, so that the arc discharge changes to the periphery of the hole and the perforation 8 is generated. The distance between the electrode-work distance 9 and the electrode-work distance 10 changes.

  Thereby, since the arc discharge length is increased, the welding voltage proportional to the electrode-workpiece distances 9 and 10 is increased. By always detecting the welding voltage, it can be determined that the perforation has occurred at the moment when the voltage exceeds the predetermined voltage.

  FIG. 3 is a flowchart showing the control operation in the first embodiment. This flowchart will be described using a specific example. For example, when a thin plate stainless steel having a thickness of 1 mm is welded in a downward butt welding with a welding current of 100 A and an arc length of 2 mm, the voltage is 12.7 V ± 0.2 V. The voltage is not a completely constant value, and some fluctuation occurs due to the characteristics of the welding power source 1 and the like. Here, it has been experimentally confirmed that when the perforation occurs, the voltage instantaneously becomes 13.2V or more, which is a value that clearly exceeds the voltage fluctuation range during normal welding. Can be determined. A sampling frequency of 10 ms or less is sufficient. As described above, it can be determined that the hole 8 has been generated.

  In this way, the perforation detection mechanism can be realized by a detection mechanism that constantly monitors the voltage during welding and can detect the moment when a certain deviation or more has occurred from a set specified value from data during normal welding.

  When starting the welding, the welding voltage is measured, and if the voltage value is within the specified value, this is repeated until the welding is completed.

  An abnormal voltage value that is a predetermined voltage is set in the control mechanism 5, and when a voltage that is equal to or higher than the abnormal voltage is detected, a control that sends a command to lower the current for a certain distance to the welding power source 1 is set. . For example, under the above conditions, the abnormal voltage is 13.2 V, and when the voltage is 13.2 V or more, for example, the welding power source 1 has a welding current of −20 A, that is, normal 100 A for a welding distance of 10 mm. Set the control to issue a command to change from 80 to 80A. In the flowchart, this corresponds to a subroutine for a current value change command.

  Thereafter, welding is continued under this condition until the correction condition is completed, and after the correction condition is completed, a normal welding state is returned by a current value return command. Here, completion of the correction condition means that the welding voltage returns to a predetermined voltage value or less. In this example, the voltage is less than 13.2V.

  When welding is continued with the perforation 8 being generated, the region to be welded after the perforation 8 becomes a boundary portion with the atmosphere due to the perforation 8, so that the thermal boundary condition is an adiabatic state. For this reason, if welding is resumed under normal welding conditions, excessive heat input will occur, and melting will occur more easily. For this reason, it is possible to quickly return to a good normal welding state after the perforation 8 is generated by reducing the welding current and reducing the heat input when the burn-out occurs. After returning to a good welding state and the influence of the adiabatic boundary conditions is eliminated, welding can be performed under normal welding conditions. Under the above conditions, 10 mm is a distance at which the influence of the adiabatic boundary condition is eliminated.

  Furthermore, in penetration welding, the metal can be welded without dripping even though it is liquid because the surface tension maintains the metal dripping. Gravity and arc pressure are used as the driving force to droop the molten metal. It is known that there is. In particular, this time, it was verified that the influence of the arc pressure is large, the molten metal is pushed by the arc pressure, and that the balance of force with the surface tension becomes unstable as the arc pressure increases. Since the arc pressure increases as the current increases, the arc current can be reduced by reducing the welding current when the hole 8 is generated, the molten metal is stabilized, and the normal welding state is quickly restored. be able to.

  For example, if a hole 8 is generated by automatic welding that does not employ the control mechanism of the present invention under the above-described conditions, the average length in the welding direction is about 50 mm, and a larger one is 100 mm or more. However, by using an automatic welding apparatus with a perforation suppression control mechanism that employs the control method of the present invention, a perforation 8 of 25 mm or less could be achieved.

  An arc welding method in which a welding head is equipped with a TIG electrode and the workpiece is arc welded while measuring the welding voltage, and when the welding voltage exceeds a predetermined voltage value, the welding current is reduced below the normal current value. When arc welding is performed and the welding voltage returns below the specified voltage value, the welding current is returned to the normal current value and arc welding is performed. Therefore, the perforation is detected based on fluctuations in the welding voltage, and the length of the perforation is increased. And can be promptly restored to a good normal welding state.

  In addition, a welding power source electrically connected to the TIG electrode provided on the welding head and the workpiece, a voltage measuring unit for measuring the welding voltage of the welding power source, and when the welding voltage exceeds a predetermined voltage value A control unit that lowers the welding current below the normal current value and returns the welding current to the normal current value when the welding voltage returns below the predetermined voltage value. It is possible to detect and suppress an increase in perforation and quickly return to a good normal welding state.

  As described above, by using the automatic welding apparatus with a perforation suppression control mechanism of the present invention, after the perforation occurs, the heat input and the arc pressure are reduced, so that the welding state is stabilized and promptly good normal welding. It can return to the state.

  In addition, when a hole is generated during welding, the melted state becomes largely unstable, so it is difficult to return to a good welded state again, and the hole tends to become long, but by carrying out the present invention, While detecting perforations and reducing excessive heat input and arc pressure, which are the main causes of instability in the molten state, it prevents the perforation from becoming too long and quickly returns to a normal welding state. it can.

Embodiment 2. FIG.
FIG. 4 is a schematic diagram of a welding apparatus according to the second embodiment. FIG. 5 is a flowchart showing the control operation in the second embodiment. Thin plate welding is through-welded with a TIG welding power source. The configuration of the equipment includes a welding power source 1, a welding head 2, a TIG electrode 3, a welding voltage detection line 4, a control mechanism 5, a control command line 6, and a welding head driving device 11. The welding voltage detection line 4 is connected to the welding power source 1, acquires the voltage during welding in real time, and transmits it to the control mechanism 5. The control mechanism 5 determines the obtained voltage and sends a torch height change command to the welding head driving device 11. Detection of perforations is the same as in the first embodiment.

  An abnormal voltage value is set in the control mechanism 5 in the same manner as in the first embodiment, and when a voltage equal to or higher than the abnormal voltage is detected, a command to increase the distance between the electrode and the workpiece in the welding head driving device 11 for a certain distance. Set the control to send. For example, under the same conditions as in the first embodiment, the abnormal voltage is set to 13.2 V when a butt welding is performed on a thin stainless steel plate having a thickness of 1 mm. When the detected welding voltage becomes 13.2 V or more, the welding head drive device 11 moves the TIG electrode 3 away from the work 7 by moving the welding head 2 by, for example, 1 mm, and maintains the state while welding 10 mm. The welding is continued under this condition until the completion of the correction, and after the correction condition is completed, the welding head 2 returns to the normal state. Here, completion of the correction condition means that the welding voltage returns to a predetermined voltage value or less. In this example, the voltage is less than 13.2V.

  In the first embodiment, the abnormality process is performed by lowering the current value, whereas in the second embodiment, the abnormality process is performed by adjusting the height of the welding head 2.

  As mentioned above, reducing the heat input and reducing the arc pressure are effective for returning to a good and rapid welding state when a hole is generated, but if the distance between the torch and the workpiece is increased, the concentration of the arc is reduced. Both effects can be obtained, the welding state can be stabilized, and a good normal welding state can be quickly restored.

  An arc welding method in which a welding head is provided with a TIG electrode and a workpiece is arc-welded while measuring a welding voltage. When the welding voltage exceeds a predetermined voltage value, the position of the welding head is increased to increase the TIG electrode and the workpiece. When the welding voltage returns below the specified voltage value, the welding head position is lowered to return to the state before widening the distance between the TIG electrode and the workpiece and arc welding. Therefore, it is possible to detect perforation based on fluctuations in the welding voltage, suppress an increase in perforation, and quickly return to a good normal welding state.

  In addition, a welding power source electrically connected to the TIG electrode provided on the welding head and the workpiece, a voltage measuring unit for measuring the welding voltage of the welding power source, and when the welding voltage exceeds a predetermined voltage value Before increasing the distance between the TIG electrode and the workpiece by increasing the position of the welding head to increase the distance between the TIG electrode and the workpiece, and when the welding voltage returns to a predetermined voltage value or less. Therefore, it is possible to detect a perforation based on a change in the welding voltage, suppress an increase in the perforation, and quickly return to a good normal welding state.

  As described above, by using the automatic welding apparatus with a perforation suppression control mechanism of the present invention, after the perforation occurs, the heat input and the arc pressure are reduced, so that the welding state is stabilized and promptly good normal welding. It can return to the state.

  In addition, when a hole is generated during welding, the melted state becomes largely unstable, so it is difficult to return to a good welded state again, and the hole tends to become long, but by carrying out the present invention, While detecting perforations and reducing excessive heat input and arc pressure, which are the main causes of instability in the molten state, it prevents the perforation from becoming too long and quickly returns to a normal welding state. it can.

Embodiment 3 FIG.
Since the apparatus configuration is the same as in the second embodiment, FIG. 4 also serves as a schematic diagram of the welding apparatus in the third embodiment. FIG. 6 is a flowchart showing the control operation in the third embodiment. The third embodiment performs configuration and control combining the first embodiment and the second embodiment. That is, thin plate welding is performed through welding with a TIG welding power source, and the equipment configuration is a welding power source 1, a welding head 2, a TIG electrode 3, a welding voltage detection line 4, a control mechanism 5, a control command line 6, and a welding head drive. It consists of device 11. The welding voltage detection line 4 is connected to the welding power source 1, acquires the voltage during welding in real time, and transmits it to the control mechanism 5. The control mechanism 5 determines the obtained voltage, reduces the welding current to the welding power source 1, and further sends a torch height change command to the welding head driving device 11. Detection of perforation is the same as in the first and second embodiments.

  An abnormal voltage value is set in the control mechanism 5 in the same manner as in the first and second embodiments. When a welding voltage equal to or higher than the abnormal voltage is detected, the welding current is reduced in the welding power source 1 for a certain distance, At the same time, a control for sending a command for increasing the electrode-workpiece distance 9 to the welding head driving device 11 is set. For example, under the same conditions as those of the first and second embodiments, the abnormal voltage is set to 13.2 V when a butt welding is performed on a thin stainless steel plate having a thickness of 1 mm. When the detected welding voltage becomes 13.2 V or more, for example, during a welding distance of 10 mm, the welding power source 1 is controlled to issue a command to change the welding current to -20A, that is, from normal 100A to 80A. At the same time, the electrode is moved 1 mm away from the workpiece to the welding head drive device and maintained in that state for 10 mm welding, and welding is continued under this condition until the correction condition is completed. After the correction condition is completed, the current value is restored. The normal state is restored by the command and the height return command. Here, completion of the correction condition means that the welding voltage returns to a predetermined voltage value or less. In this example, the voltage is less than 13.2V.

  As mentioned above, reducing the heat input and reducing the arc pressure are effective in returning to a good welding state when a hole is generated, but by reducing the welding current and further increasing the distance between the torch and the workpiece, Both effects can be obtained, the welding state can be stabilized, and a good normal welding state can be quickly restored.

  An arc welding method in which a welding head is equipped with a TIG electrode and the workpiece is arc welded while measuring the welding voltage, and when the welding voltage exceeds a predetermined voltage value, the welding current is reduced below the normal current value. In addition, the position of the welding head is increased to increase the distance between the TIG electrode and the workpiece and arc welding is performed. After that, when the welding voltage returns to a predetermined voltage value or less, the welding current is returned to the normal current value. In addition, arc welding is performed by lowering the position of the welding head and returning to the state before increasing the distance between the TIG electrode and the workpiece, so that perforation is detected by fluctuations in the welding voltage, and the lengthening of the perforation is suppressed. It is possible to quickly return to a good normal welding state.

  A welding power source electrically connected to the TIG electrode provided on the welding head and the workpiece, a voltage measuring unit for measuring the welding voltage of the welding power source, and a welding current when the welding voltage exceeds a predetermined voltage value When the welding voltage returns below the predetermined voltage value, the welding current is reduced to the normal current value. And a control unit that lowers the position of the welding head and restores the state before expanding the distance between the TIG electrode and the workpiece, so that the perforation is detected by fluctuations in the welding voltage and the perforation is lengthened. It can suppress and can return to a favorable normal welding state promptly.

  As described above, it is possible to detect perforation by detecting voltage and to control to return to normal welding at the same time as detection without adding a special device and simply adding general-purpose equipment. To do. This control is to reduce heat input and arc pressure, and at least one of (1) decrease of welding current and (2) increase of distance between electrode and workpiece is performed once. It is possible to provide a perforation suppressing method and an automatic welding apparatus with a perforation suppression function that quickly return to a good normal welding state even when perforation occurs.

  In addition, by using the automatic welding apparatus with a perforation suppression control mechanism of the present invention, after the perforation occurs, the heat input and the arc pressure are reduced, so that the welding state is stabilized and quickly brought into a good normal welding state. Can return.

  In addition, when a hole is generated during welding, the melted state becomes largely unstable, so it is difficult to return to a good welded state again, and the hole tends to become long, but by carrying out the present invention, While detecting perforations and reducing excessive heat input and arc pressure, which are the main causes of instability in the molten state, it prevents the perforation from becoming too long and quickly returns to a normal welding state. it can.

  1 welding power source, 2 welding head, 3 electrodes, 4 voltage detection line, 5 control mechanism, 6 control command line, 7 workpieces, 8 holes, 9 electrode-working distance (during normal welding), 10 (when holes are drilled) A) electrode-workpiece distance, 11 welding head drive.

Claims (6)

An arc welding method in which a workpiece is arc-welded while measuring a welding voltage with a TIG electrode in the welding head,
When the welding voltage exceeds a predetermined voltage value, the arc current is reduced by reducing the welding current from a normal current value,
An arc welding method, wherein when the welding voltage returns to a predetermined voltage value or less, the arc welding is performed by returning the welding current to the normal current value. When the welding voltage exceeds a predetermined voltage value, the position of the welding head is increased to increase the distance between the TIG electrode and the workpiece, and the arc welding is performed.
When the welding voltage returns below a predetermined voltage value, the arc welding is performed by lowering the position of the welding head and returning to a state before widening the distance between the TIG electrode and the workpiece. The arc welding method according to claim 1. An arc welding method in which a workpiece is arc-welded while measuring a welding voltage with a TIG electrode in the welding head,
When the welding voltage exceeds a predetermined voltage value, the position of the welding head is increased to increase the distance between the TIG electrode and the workpiece, and the arc welding is performed.
When the welding voltage returns below a predetermined voltage value, the arc welding is performed by lowering the position of the welding head and returning to a state before widening the distance between the TIG electrode and the workpiece. Arc welding method. A welding power source electrically connected to the TIG electrode provided on the welding head and the workpiece;
A voltage measuring unit for measuring a welding voltage of the welding power source;
When the welding voltage exceeds a predetermined voltage value, the welding current is reduced below the normal current value, and when the welding voltage returns below the predetermined voltage value, the welding current is changed to the normal current value. An arc welding apparatus comprising a control unit for returning to When the welding voltage exceeds a predetermined voltage value, the control unit increases the position of the welding head to widen the distance between the TIG electrode and the workpiece, and the welding voltage returns below the predetermined voltage value. 5. The arc welding apparatus according to claim 4, wherein the welding head is lowered to a state before the distance between the TIG electrode and the workpiece is increased by lowering the position of the welding head. A welding power source electrically connected to the TIG electrode provided on the welding head and the workpiece;
A voltage measuring unit for measuring a welding voltage of the welding power source;
When the welding voltage exceeds a predetermined voltage value, the position of the welding head is increased to widen the distance between the TIG electrode and the workpiece, and when the welding voltage returns to a predetermined voltage value or less. An arc welding apparatus comprising: a control unit that lowers the position of the welding head and restores the state before the distance between the TIG electrode and the workpiece is increased.

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