JP2005246440A - Welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding method in which blowhole defects can be greatly reduced. <P>SOLUTION: After a welding process, a blowhole eliminating process is implemented. In this blowhole eliminating process, a laser output is adjusted so that a heat fusible depth by a laser beam becomes not more than the thickness of a sleeve 11 emitting the beam. As a result, while the blowholes generated in a bead in the welding process are eliminated by remelting, the heat fusible depth is confined inside the sleeve 11; therefore, it can prevent generation of new blowholes that hinder air-tightness. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a welding method for at least two members to be welded.

  When two members to be welded are laser-welded, pore defects (blow holes and pits) may occur in the welded portion. When such a pore defect occurs, the weld quality deteriorates, for example, the hermeticity of the welded portion is lowered. Conventionally, various methods for reducing the pore defect have been studied.

  For example, pore defects are likely to occur when a material that is gasified by heat of welding (for example, dirt such as moisture, oil, rust, etc.) is present on the surface of the member to be welded. For this reason, it is performed to sufficiently remove the contamination of the member to be welded before welding.

  Furthermore, the amount of pore defects varies depending on various welding conditions during welding. For example, if the shielding gas such as argon or nitrogen cannot sufficiently cover the molten pool due to insufficient shielding gas flow, air is entrained in the molten pool and becomes bubbles. If the molten metal solidifies before the bubbles can be removed, a blow hole is generated in the weld metal. In addition, the amount of pore defects generated in the welded portion varies depending on the welding speed, the laser output during welding, the focus position of the laser beam, and the like. For this reason, the amount of generation | occurrence | production of a pore defect can be aimed at by examining the optimal combination of these welding conditions.

  However, as described above, even if cleaning is performed or welding conditions are set optimally, there is a limit to the reduction in the generation of pore defects.

  The present invention has been made in view of the above-described points, and an object thereof is to provide a welding method capable of significantly reducing pore defects.

In order to achieve the above object, the welding method according to claim 1,
At least two members to be welded are overlapped, and one of the members to be welded is irradiated with a beam so that the heating and melting depth reaches the other member to be welded in the beam irradiation. A welding process for forming a welded portion for welding two welded members to each other by adjusting the degree of heating and melting by the beam;
After the welding process, the welded part formed in the welding process is further irradiated with a beam, and in the beam irradiation, the heating and melting depth is equal to or less than the thickness of the member to be welded on the side directly irradiating the beam. And a pore disappearance step of eliminating pores generated in the welding process by adjusting the degree of heating and melting by the beam so that

  As described above, in the welding method according to the first aspect, the pore disappearance step is performed after the welding step. In this pore disappearance step, the degree of heating and melting by the beam is adjusted so that the heating and melting depth is equal to or less than the thickness of the member to be welded on the side irradiated with the beam. Thereby, it is possible to prevent the generation of new pores while eliminating the pores generated in the welded portion in the welding process by remelting. As a result, it is possible to significantly reduce pore defects as compared with the case where welding conditions are simply set as in the prior art.

  As described in claim 2, the beam irradiation range in the pore elimination process is preferably wider than the beam irradiation range in the welding process. Thereby, in the pore disappearance step, the entire region of the welded portion in the member to be welded on the side directly irradiated with the beam can be remelted, so that most of the pores generated in the welded portion can be eliminated.

  As described in claim 3, the beam is preferably a laser beam. In the case of a laser beam, it is easy to adjust the degree of heating and melting in the welding process and the pore disappearance process, and stable welding can be performed even if the welding speed is set relatively fast.

  As described in claim 4, in the welding process, it is preferable that the beam is emitted in a pulse shape. Thereby, the peak power of the beam can be increased without imposing much load on the beam forming circuit such as an oscillator.

  On the other hand, as described in claim 5, it is preferable that the beam is continuously emitted in the pore disappearance step. When the beam is continuously emitted to the welded portion (bead portion) formed by the welding process, the bead portion can be made smooth.

Moreover, as described in claim 6,
At least one of the two members to be welded is formed in a hollow cylindrical shape,
The other welded member is press-fitted into the hollow cylindrical portion of one welded member,
A welded part is formed by a welding process over the entire circumference of the circumferential part where one welded member and the other welded member overlap, and a pore disappearance process is performed on the circumferential welded part. By doing so, one member to be welded and the other member to be welded can be welded in an airtight manner.

  In the welding method according to the present invention, the airtightness of the welded portion can be sufficiently ensured by reducing pore defects in the welded portion. Therefore, it is suitable for welding products such as various solenoid valves formed by using the hollow cylindrical member to be welded as described above, particularly products that require airtightness.

  Hereinafter, a welding method according to an embodiment of the present invention will be described. First, the configuration of a solenoid valve as a workpiece to which the welding method according to the present embodiment is applied will be briefly described. However, the application target of the welding method according to the present invention is not limited to a solenoid valve, and can be suitably used for products that require airtightness in the welded part and products that require improved weld quality in the welded part. .

  As shown in FIG. 1, a solenoid valve 10 as a workpiece is a valve in which a sleeve 11 formed in a cylindrical shape is press-fitted into an opening of the sleeve 11, and an overlapping portion with the sleeve 11 is laser-welded. And a housing 12. The sleeve 11 and the valve housing 12 are welded using the welding method according to the present embodiment, so that the airtightness inside the electromagnetic valve 10 is ensured.

  A solenoid 13 and a first plunger 14 are provided in the sleeve 11. The first plunger 14 is attracted downward in FIG. 1 by the magnetic flux generated by the solenoid 13 when the solenoid 13 is energized.

  A second plunger 15 is slidably provided in the valve housing 12. The second plunger 15 moves together with the first plunger 14 when the first plunger 14 is sucked downward in FIG. A ball valve 16 is attached to one end of the second plunger 15. The ball valve 16 shuts off the flow path 18 and the flow path 19 when seated on the valve seat 20 formed in the valve housing 12, and disconnects the flow path 18 and the flow path 19 when separated from the valve seat 20. Communicate.

  A spring 17 is provided between the valve seat 20 and the second plunger 15, and this spring 17 urges the second plunger upward in FIG. Therefore, the electromagnetic valve 10 is a normally open two-way valve in which the flow paths 18 and 19 are in communication with each other when the solenoid 13 is not energized, and are in a disconnected state when energized. In such a solenoid valve 10, since the working fluid flows through the inside, it is necessary to ensure airtightness.

  Next, a welding apparatus 30 that performs welding using the electromagnetic valve 10 as a workpiece will be described with reference to FIGS. FIG. 2A is an explanatory diagram showing a state in which the irradiation position of the laser beam is shifted by a predetermined offset amount with respect to the center position of the cylindrical workpiece, and FIG. 2 is a configuration diagram showing the overall configuration of the device 30. FIG.

  As shown in FIG. 2B, the welding apparatus 30 includes a laser oscillator 32. The laser output from the laser oscillator 32 is converted into a laser beam by the welding head 33 and is irradiated onto the workpiece. That is, the welding head 33 has an optical system that converts the laser output of the laser oscillator 32 into a laser beam having a predetermined focal length. Further, a position adjustment mechanism that adjusts the position of the welding head 33 with respect to the workpiece is provided. With this position adjustment mechanism, it is possible to adjust the irradiation position and focal position of the laser beam from the welding head 33 on the workpiece. it can. Further, the laser oscillator 32 can change the magnitude of the laser output, the output timing so as to output continuously or in pulses, the magnitude according to the control signal from the control circuit 31 described later, and Laser output is given to the welding head 33 at the output timing.

  The irradiation position of the laser beam in the welding process is set to a position shifted by a predetermined offset amount from the axial center position of the electromagnetic valve 10 that is a workpiece as shown in FIG. 2A, for example. As for the focal position of the laser beam, as shown in FIG. 2B, the just focus position is set not to be on the surface of the sleeve 11 but inside the valve housing 12. Note that the distance from the surface of the sleeve 11 to the just focus position is referred to as a defocus amount.

  The welding device 30 further includes an air pump 34 and an air curtain generator 35. The air curtain generator 35 ejects the air supplied by the air pump 34 in a curtain shape. By this air curtain, it is possible to reduce the entrainment of air into the molten pool by blocking the flow of outside air toward the welded portion of the workpiece.

  The drive motor 36 is connected to the workpiece holder 37 and rotates the workpiece in the welding process and the pore disappearance process. Thereby, it becomes possible to irradiate the laser beam from the welding head 33 over the entire circumference of the workpiece.

  Although not shown, the welding apparatus 30 includes a supply source that supplies nitrogen gas as a shielding gas in order to entrain air into the molten pool. The nitrogen gas is guided by the guide 38 so as to flow along the surface of the workpiece. As a result, the irradiation position of the laser beam, that is, the location where the molten pool is generated is shielded by nitrogen gas.

  The control circuit 31 outputs a control signal to the laser oscillator 32, the air pump 34, the drive motor 36, and the like described above, and executes a welding process so as to suppress the generation of pores as much as possible. That is, the offset amount, the defocus position, the welding speed (rotation speed), the laser output at the time of welding, the duty ratio and frequency when the laser is a pulse wave output, the air curtain ejection method, and the nitrogen gas Since the ejection method is related to the amount of pores generated, the optimal combination conditions are set so that the amount of pores generated is minimized, and a control signal is output so that each component operates according to the combination conditions. To do.

  However, even if the optimal combination conditions are set and the welding process is performed, it is impossible to completely prevent the generation of pores. Therefore, in the welding method according to the present embodiment, after the welding process, A pore disappearance step is performed.

  A welding process and a pore disappearance process executed by the welding apparatus 30 of the present embodiment will be described in detail with reference to FIGS. 3 (a) and 3 (b) and FIGS. 4 (a) and 4 (b). FIG. 3 (a) is a graph showing the relationship between the laser output in the welding process and the penetration depth d1 and the width l1 due to laser beam irradiation at the laser output, and FIG. 3 (b) shows the penetration depth. It is explanatory drawing for showing length d1 and width l1. FIG. 4A is a graph showing the relationship between the laser output in the pore disappearance process and the penetration depth d2 and the width l2 due to laser beam irradiation at the laser output. FIG. It is explanatory drawing for showing the penetration depth d2 and the width | variety l2.

  In the welding process, the overlapping portion between the sleeve 11 and the valve housing 12 is heated and melted and welded using the laser output from the laser oscillator 32. For this reason, the heat-melting depth by laser beam irradiation needs to reach the valve housing 12. At this time, in order to ensure the required welding strength, as shown in FIG. 3 (b), the penetration depth d1 and the width l1 in the valve housing 12 are targeted under conditions that are not less than a predetermined lower limit value. Weld. Therefore, in the example shown in FIG. 3A, the penetration depth d1 and the width l1 in the valve housing 12 are predetermined lower limits, d1: 0.1 [mm], l1: 0.15 [mm]. As described above, the magnitude of the laser output is set to a high output of 700 to 900 [W].

  When performing this welding process, it is preferable that the laser output of the laser oscillator 32 is a pulse wave output having a predetermined duty ratio, and the duty ratio is set as low as possible. Thereby, the peak value of the laser output can be increased while suppressing the load applied to the laser oscillator 32. In addition, the bead part (welding part) by this pulse wave output is formed so that the adjacent several bead part may overlap so that the airtightness in a workpiece may be ensured.

  In the pore disappearance process performed after the welding process, the laser oscillator 32 sets the laser output to a low output of, for example, 400 to 500 [W] and a continuous wave output that is continuously output. The magnitude of the laser output in this pore disappearance step is such that the heating and melting depth by the laser beam irradiation is the sleeve 11 in order to prevent the generation of new pores that impair the airtightness in the sleeve 11 irradiated with the laser beam. It is determined to be less than the thickness of That is, in the pore disappearance step, as shown in FIG. 4B, the penetration depth d2 and the width l2 in the sleeve 11 are targeted, and the penetration depth d2 is the thickness of the sleeve 11 (0.323 [mm]. ]) The laser output is set to a low output so as to be as follows (see FIG. 4A).

  Further, the defocus amount of the laser beam and the like are changed so that the penetration width l2 in the sleeve 11 is at least larger than the penetration width l1 in the valve housing 12 in the welding process. For example, in the example shown in FIGS. 3A and 4A, the penetration width l1 of the valve housing 12 is in the range of 0.2 to 0.4 [mm], whereas the penetration of the sleeve 11 is. The width l2 is a value in the range of 0.5 to 0.6 [mm].

  Here, as shown in FIG. 3B, the penetration width of the surface of the sleeve 11 in the welding process is substantially equal to the penetration width l1 of the valve housing 12. For this reason, the penetration width l2 of the sleeve surface in the pore elimination process is larger than the penetration width of the sleeve surface in the welding process. As a result, in the pore disappearance step, the entire area of the bead portion (welded portion) in the sleeve 11 directly irradiated with the laser beam can be remelted, so that most of the pores generated in the bead portion (substantially all of them). ) Can be eliminated.

  Furthermore, in the pore disappearance process, by making the laser output a continuous wave output, the discontinuous bead portion generated by the pulse wave output in the welding process can be remelted and the surface thereof can be smoothed.

  By continuously performing the welding process and the pore disappearance process described above, the pore defects in the bead portion can be significantly reduced.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

  For example, in the above-described embodiment, an example in which welding is performed using a laser beam has been described. However, an electron beam, a light beam, a plasma jet, and an arc can be used as a heating source in the welding process and the pore disappearance process. is there.

It is sectional drawing which shows the structure of the solenoid valve as a workpiece | work. (A) is explanatory drawing which shows the state which shifted the irradiation position of the laser beam only the predetermined | prescribed offset amount with respect to the center position of a cylindrical workpiece, (b) is the whole structure of the welding apparatus 30. FIG. FIG. (A) is a graph which shows the relationship between the laser output in a welding process, and the penetration depth d1 and the width | variety 11 by laser beam irradiation with the laser output, (b) shows the penetration depth d1 and the width | variety l1. It is explanatory drawing for showing. (A) is a graph which shows the relationship between the laser output in a void | hole elimination process, and the penetration depth d2 and the width | variety 12 by laser beam irradiation with the laser output, (b) is the penetration depth d2 and width. It is explanatory drawing for showing l2.

Explanation of symbols

10 Solenoid valve (workpiece)
DESCRIPTION OF SYMBOLS 11 Sleeve 12 Valve housing 30 Welding device 31 Control circuit 31 Laser oscillator 32 Welding head 34 Air pump 35 Air curtain generating part 36 Drive motor 37 Holder

Claims (6)

At least two members to be welded are overlapped, and one of the members to be welded is irradiated with a beam so that the heating and melting depth reaches the other member to be welded in the beam irradiation. A welding step of forming a welded portion for welding the two welded members to each other by adjusting the degree of heating and melting by the beam;
After the welding step, the welded part formed in the welding step is further irradiated with a beam, and in the beam irradiation, the thickness of the member to be welded on the side where the heat melting depth directly irradiates the beam. And a pore disappearance step for eliminating pores generated in the welding step by adjusting the degree of heating and melting by the beam so as to be equal to or less than the above.   The welding method according to claim 1, wherein a beam irradiation range in the pore disappearance step is wider than a beam irradiation range in the welding step.   The welding method according to claim 1, wherein the beam is a laser beam.   The welding method according to claim 1, wherein, in the welding step, the beam is emitted in a pulse shape.   The welding method according to claim 1, wherein the beam is continuously emitted in the pore disappearance step. At least one of the two welded members is formed in a hollow cylindrical shape,
The other welded member is press-fitted into the hollow cylindrical portion of the one welded member,
The welded portion is formed by the welding process over the entire circumference of the circumferential portion where the one welded member and the other welded member overlap, and the pores are formed in the circumferential welded portion. 6. The welding method according to claim 1, wherein the one welded member and the other welded member are hermetically welded by performing a disappearance step.

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