JP2014140853A - Welding method and welding product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding method and a welded product which can prevent weld cracks effectively by the texture control of welded parts.SOLUTION: The welding method has a welding process which welds between members 11 and 12 with different carbon content. In the welding process, while supplying the metal material W for welding to a butted part 13 to which both the members are butted, beam B is irradiated to a position which shifts from the butted part to the side of one member 11 with lower carbon content such that both the members are welded each other.

Description

  The present invention relates to a welding method and a welded article.

  Conventionally, various attempts have been made to improve welding quality. For example, the ring gear and the differential case that are welded to each other described in Patent Document 1 are formed so that the center of the load that the ring gear receives is positioned within the radial width of the welded portion formed along the circumferential direction. Yes. This prevents an unreasonable load from acting on the welded portion, so that the load bearing performance of the welded portion is enhanced.

JP 2011-47420 A

  On the other hand, in order to further improve the welding quality, the present inventors diligently studied prevention of weld cracking by controlling the structure of the welded part, in addition to improving the characteristics of the welded part by devising the member shape as described above. In particular, the inventors of the present invention have made extensive studies on the prevention of weld cracking by controlling the structure of the welded part when welding members having different carbon contents such as a ring gear and a differential case.

  The present invention has been made as a result of such studies, and an object thereof is to provide a welding method and a welded product that can effectively prevent weld cracking by controlling the structure of the welded portion.

  The welding method of the present invention for achieving the above object has a welding step of welding members having different carbon contents. In the welding process, the welding metal material is supplied to the butted portion where the members are butted together, and the beam is irradiated to a position shifted from the butted portion toward one member having a small carbon content. They are welded together.

  The welded product of the present invention for achieving the above object has welds formed by melting members having different carbon contents and a metal material for welding. The welded portion is shifted from the butted portion where the members are butted to one member side having a small carbon content.

  According to the welding method having the above configuration, the beam is irradiated to a position shifted to one side having a small carbon content among the butted members, and the welded product having the above configuration has a low carbon content. A weld is formed at a position shifted to one side. For this reason, the carbon content of the weld zone is suppressed. As a result, martensite, which is a brittle structure, is suppressed in the welded portion, and austenite, which is a ductile structure, increases, so that weld cracks can be effectively prevented.

It is a schematic block diagram of the welded product of embodiment for demonstrating the welding method and welded product of embodiment. It is sectional drawing which follows the 2-2 line of FIG. 1 before welding. It is an arrow view from three directions of FIG. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is sectional drawing which follows the 2-2 line | wire of FIG. 1 after welding. It is sectional drawing which expands and shows the principal part corresponding to FIG. 2 and FIG. 5 of the welded goods of an Example.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the dimension ratio of drawing is exaggerated on account of description, and differs from an actual ratio.

  As outlined in FIG. 1, the ring gear 11 and the differential case 12 (members having different carbon contents) formed of different materials are welded by the welding method of the present embodiment, and a welded product 10 in which the ring gear 11 and the differential case 12 are joined is produced. Is done.

  The ring gear 11 is formed of a material having a lower carbon content than the material forming the differential case 12. The ring gear 11 is made of, for example, a steel material. The steel material is, for example, SCr417H, SCr420H, SCM420H, SCM418H, SNCM420H, etc. defined in the JIS standard. The differential case 12 is made of, for example, cast iron material. The cast iron material is, for example, FCD450, FCD600, FCD700, FCD800, etc. defined in the JIS standard.

  When the welding wire W (metal material for welding) is supplied to the butting portion 13 where the ring gear 11 and the differential case 12 are butted, and the laser beam B is irradiated, the ring gear 11 and the differential case 12 are welded. The butting portion 13 is formed by butting the circumferentially arranged circumferential portions 14 and 15 provided in the ring gear 11 and the differential case 12.

The laser beam B is emitted from a nozzle N disposed in the vicinity of the abutting portion 13. The laser beam B is oscillated by an oscillator and then emitted from the nozzle N through a condensing optical system including a condensing lens. The laser beam B is, for example, a CO ₂ laser, but is not limited to this. The laser beam B may be a YAG laser, for example. The nozzle N may include a gas flow path and blow out a shielding gas such as argon or nitrogen.

  As shown in FIG. 2, the differential case 12 has a protrusion 16 protruding in a direction along the rotation axis. The ring gear 11 has a hole 17 into which the protrusion 16 is fitted. The ring gear 11 and the differential case 12 are connected by fitting the protrusion 16 and the hole 17. The differential case 12 is connected to a rotary drive device including a motor and the like. The ring gear 11 rotates together with the differential case 12. The nozzle N is fixed.

  During welding, the ring gear 11 and the differential case 12 rotate in the circumferential direction as shown in FIG. 3 while the emission position and emission direction of the laser beam B are fixed. The ring gear 11 and the differential case 12 are welded while the irradiation position of the laser beam B relatively moves in the circumferential direction of the circumferential portions 14 and 15. The ring gear 11 and the differential case 12 are welded along the entire circumference of the circumferential portions 14 and 15.

  The welding wire W is supplied by a wire feeding mechanism that feeds the welding wire W from a wire reel around which the welding wire W is wound. The welding wire W is sequentially supplied in accordance with the rotation of the ring gear 11 and the differential case 12.

  The welding wire W contains nickel. The content of nickel in the welding wire W is preferably 10% by mass or less, but is not limited thereto and may be more than 10% by mass. The material for forming the welding wire W is, for example, a welding wire containing Ni such as Y308 and Y310 defined in JIS standards.

  The irradiation position of the laser beam B and its vicinity are photographed by a photographing device C such as a CCD camera. During welding, the operator confirms an image photographed by the photographing device C with a display device such as a liquid crystal display. The ring gear 11 and the differential case 12 are welded while the irradiation position of the laser beam B is monitored.

  As shown in FIG. 4, the irradiation position of the laser beam B is shifted from the butting portion 13 toward the ring gear 11 with a low carbon content. Therefore, as shown in FIG. 5, the ring gear 11, the differential case 12, and the welded portion 18 formed by melting the welding wire W by the irradiation of the laser beam B are shifted from the butted portion 13 toward the ring gear 11 side. To do.

  The effect of this embodiment is described.

  According to the welding method of the present embodiment, the laser beam B is irradiated to a position shifted to the ring gear 11 side having a low carbon content in the ring gear 11 and the differential case 12, and the ring gear having a low carbon content in the welded product 10. A weld 18 is formed at a position shifted to the 11 side. For this reason, the carbon content of the welded portion 18 is suppressed. As a result, martensite, which is a brittle structure, is suppressed in the welded portion 18 and austenite, which is a ductile structure, increases, so that weld cracks can be effectively prevented. The correlation between the carbon content of the weld 18 and the austenite is predicted from the Schaeffler phase diagram.

  By welding while monitoring the irradiation position of the laser beam B, the laser beam B is reliably irradiated to the position shifted to the ring gear 11 side without the irradiation position deviating to the differential case 12 side. For this reason, the welding part 18 is shifted and formed in the ring gear 11 side with little carbon content in the whole cyclic | annular welding part 18 formed around a rotating shaft. Therefore, the weld crack is effectively suppressed in the entire welded portion 18 and the members are reliably joined.

  Unlike the present embodiment, when the ring gear 11 and the differential case 12 are fixed without rotating and are welded in the circumferential direction while changing the emission position and emission direction of the laser beam B and the supply position of the welding wire W, the nozzle N and A driving device for moving the welding wire W and the like and a control device for controlling them are required. For this reason, the welding apparatus may be complicated. On the other hand, in the present embodiment, the welding is performed by rotating the ring gear 11 and the differential case 12 in the circumferential direction while fixing the emission position and the emission direction of the laser beam B. There is no need for a large-scale device, so the welding device can be simplified.

  When the welding wire W contains nickel, austenite, which is a ductile structure, increases in the welded portion 18, so that weld cracks can be more effectively prevented.

  By using the welding wire W having a nickel content of 10% by mass or less, the material cost can be suppressed, so that the manufacturing cost can be suppressed. In this embodiment, since the carbon content of the welded portion 18 is suppressed by controlling the irradiation position of the laser beam B, austenite increases in the welded portion 18 even if the amount of nickel contained in the welding wire W is small. Accordingly, it is possible to effectively prevent weld cracking while suppressing costs.

<Example>
As shown in FIG. 6, the inventors actually weld the welded product 20 by welding a ring gear 21 and a differential case 22 in which an annular gap 24 is formed between members when they are abutted with each other. Produced. The configuration other than the gap 24 is substantially the same as the embodiment.

The material forming the ring gear 21 is SCM418H defined in the JIS standard as case hardening steel. The material forming the differential case 22 is FCD700 defined in JIS standards as graphite cast iron. The inventors used a welding wire W formed of Y308 defined in the JIS standard. The laser beam B to be irradiated is a CO ₂ laser.

  The inventors changed the output of the laser beam B at each of a plurality of irradiation positions set by shifting the positions along the rotation axes of the ring gear 21 and the differential case 22, and welded. Strength of welded portion 25 formed by melting ring gear 21, differential case 22, and welding wire W by irradiation of laser beam B, presence or absence of breakage in welded portion 25, hardness of welded portion 25, and depth of welded portion 25 With respect to the above, different results were obtained depending on the output of the laser beam B and the irradiation position. The results are shown in Tables 1 to 4 below.

  The laser beam irradiation position described in Tables 1 to 4 is a separation distance in a direction along the rotation axis from the abutting portion 23 between the ring gear 21 and the differential case 22.

  When the laser beam irradiation position is positive in Tables 1 to 4, the irradiation position of the laser beam B is located closer to the ring gear 21 than the butting portion 23. For example, when the laser beam irradiation position is 0.2 mm, the laser beam B is irradiated to a position shifted from the abutting portion 23 in the axial direction toward the 0.2 mm ring gear 21 side.

  When the laser beam irradiation position is negative in Tables 1 to 4, the irradiation position of the laser beam B is located closer to the differential case 22 than the butting portion 23. For example, when the laser beam irradiation position is −0.2 mm, the laser beam B is irradiated to a position shifted from the abutting portion 23 in the axial direction toward the differential case 22 side.

  Table 1 shows the results obtained for the strength of the welded portion 25 after curing. A circle in Table 1 indicates that the strength of the welded portion 25 is equal to or greater than the strength of the differential case 22. The strength of the differential case 22 is lower than the strength of the ring gear 21. X in Table 1 indicates that the strength of the welded portion 25 is smaller than the strength of the differential case 22. The hatched portion in the table is not welded, and this is the same for Tables 2 to 4.

  From the results of Table 1, when welding is performed by irradiating the laser beam B on the ring gear 21 side having a relatively low carbon content, and irradiating the laser beam B on the side of the differential case 22 having a relatively high carbon content. It can be seen that a welded portion 25 having a higher strength can be obtained.

  Table 2 shows the results obtained for the presence or absence of breakage in the welded portion 25 after curing. A circle in Table 2 indicates that no fracture occurred in the welded portion 25. X in Table 2 indicates that fracture occurred in the welded portion 25.

  From the results in Table 2, it can be seen that the welded portion 25 can be prevented from being broken by irradiating the ring gear 21 with a relatively low carbon content to the side of the ring gear 21 for welding.

  Table 3 shows the results obtained for the hardness of the welded portion 25 after curing. “◯” in Table 3 indicates that the hardness of the welded portion 25 is Vickers hardness of 400 Hv or less. In Table 3, “X” indicates that the hardness of the welded portion 25 is greater than 400 Hv in terms of Vickers hardness.

  When the hardness of the welded portion 25 indicated by ◯ in Table 3 is 400 Hv or less, the welded portion 25 contains more austenite than martensite. When the hardness of the welded portion 25 indicated by x in Table 3 is greater than 400 Hv, the welded portion 25 contains more martensite than austenite.

  From the results of Table 3, the laser beam B is irradiated on the ring gear 21 side where the carbon content is relatively small as compared with the case where welding is performed by irradiating the laser beam B on the differential case 22 side where the carbon content is relatively large. It turns out that the austenite contained in the welding part 25 increases by welding.

  When the welded portion 25 contains more austenite, which is a ductile structure, than martensite, weld cracks are effectively prevented. As the irradiation position of the laser beam B is separated from the butted portion 23 toward the ring gear 21 having a relatively small carbon content, the carbon content is decreased and the austenite is increased in the welded portion 25, so that the weld crack is more effective. Can be prevented.

  Table 4 shows the results obtained for the depth of the welded portion 25 after curing. The circles in Table 4 indicate that the welded portion 25 is deep and the welded portion 25 is formed completely through the butted portion 23 from the outer surface of the ring gear 21 and the differential case 22 to the gap 24. Δ in Table 4 indicates a case where the welded portion 25 reaches the gap 24 but does not completely penetrate the butted portion 23. In Table 4, “x” indicates a case where the welded portion 25 does not penetrate the butted portion 23 without reaching the gap 24.

  From the results of Table 4, it can be seen that the welded portion 25 can be formed deeply by irradiating the laser beam B to the ring gear 21 side having a relatively low carbon content and welding. When the welded portion 25 is formed deep, the members are firmly joined to each other.

  From the results of Tables 1 to 4, the irradiation position of the laser beam B is preferably between the butt portion 23 and the position shifted by 0.2 mm from the butt portion 23 to the ring gear 21 side. More preferably, it was found that the position was shifted by 0.2 mm from the butt 23 to the ring gear 21 side.

  By irradiating the laser beam B at a position shifted by 0.2 mm from the butted portion 23 toward the ring gear 21, as shown in Tables 1 to 4, breakage and weld cracking of the welded portion 25 can be effectively prevented. In addition, the welded portion 25 can be formed deep to strengthen the joining between the members.

  The present invention is not limited to the above-described embodiments and examples, and various modifications can be made within the scope of the claims.

  For example, the members to be welded are not limited to the ring gear and the differential case as long as they have different carbon contents, and other members may be used.

  In the embodiments and examples, welding is performed by rotating the ring gear and the differential case in the circumferential direction while fixing the emission position and emission direction of the laser beam, but the present invention is not limited to this. The present invention includes a form in which the ring gear and the differential case are fixed without rotating and welded in the circumferential direction while changing the emission position and the emission direction of the laser beam. The beam is not limited to a laser beam, and may be an electron beam.

10, 20 welded product,
11, 21 Ring gear (one member with low carbon content),
12, 22 Differential case (the other member),
13, 23 Butting part,
14 Circumference,
15 circumference,
16 protrusions,
17 holes,
18, 25 welds,
24 gap,
B Laser beam (beam),
C photographing device,
N nozzle,
W Welding wire (welding metal material).

Claims (7)

  Supplying the welding metal material to the butted portion where the members having different carbon contents are butted together, and irradiating a beam to a position shifted from the butted portion toward one of the members having a small carbon content, A welding method comprising a welding step of welding members together.   The welding method according to claim 1, wherein welding is performed while monitoring an irradiation position of the beam.   The abutting portion is formed by abutting a circumferentially arranged circumferential portion of the members, and in the welding process, the member is placed on the circumferential portion while fixing an emission position and an emission direction of the beam. The welding method according to claim 1, wherein welding is performed while rotating the irradiation position of the beam relatively in the circumferential direction of the circumferential portion by rotating in the circumferential direction.   The welding method according to claim 1, wherein the welding metal material includes nickel.   The welding method according to claim 4, wherein the nickel content is 10% by mass or less.   The welding method according to any one of claims 1 to 5, wherein the beam is irradiated to a position shifted by 0.2 mm from the butted portion toward one of the members having a small carbon content. . Members having different carbon contents and welds formed by melting metal materials for welding,
The welded portion is a welded product that is shifted from a butted portion where the members are butted to one of the members having a low carbon content.

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