JP2008161937A - Fusion-bonded product having high-strength part and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fusion-bonded product capable of maintaining required strength of a bonded portion while having a high-strength part of required precision. <P>SOLUTION: The fusion-bonded product having a high- strength part, comprises: a first preform constituted by integrally, frictionally pressure-welding a first low-carbon steel part made of low-carbon steel containing less than 0.45% of C and a high-carbon steel part made of high-carbon steel containing not less than 0.45% of C; and a second preform having a second low-carbon steel part made of second low-carbon steel containing less than 0.45% of C. The high-carbon steel part of the first preform is provided with a high-strength part that has been previously formed into a desired shape and quenched, the second low-carbon steel part of the second preform has been previously formed into a predetermined shape, and the first low-carbon steel part of the first preform and the second low-carbon steel part of the second preform are bonded to each other by fusion welding. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fusion bonded product having a high strength portion and a method for manufacturing the same.

  Conventionally, friction welding is known as a technique for forming a joined product by joining two members having different shapes. For example, in Japanese Patent Laid-Open No. 5-84614, a first intermediate processed product having a tooth profile formed by precision forging and a second intermediate processed product are joined by friction welding to form a composite gear having a tooth profile portion. Is disclosed.

  Laser welding is known as another technique for forming a joined product by joining two members having different shapes. For example, Japanese Patent Application Publication No. 2006-509172 discloses that a ring gear and a differential case that require high strength are laser welded to form a differential case having a tooth profile.

  In the technique disclosed in Japanese Patent Application Laid-Open No. 5-84614, that is, in the technique of joining the first intermediate processed product and the second intermediate processed product having tooth shapes formed by precision forging by friction welding, the first intermediate processed product is used. Then, either one of the second intermediate processed product is pressed against the other while being rotated at a high speed, and the end portion of the first intermediate processed product and the end portion of the second intermediate processed product are melted by frictional heat to be joined. For this reason, the joined product that has been friction welded may be joined in a state where the axis of the first intermediate processed product and the axis of the second intermediate processed product are misaligned, The axial length may vary due to melting with the end of the two intermediate processed product. In such a case, there is a problem that the required accuracy cannot be obtained in the joined product subjected to friction welding. In order to obtain the necessary accuracy for the friction-welded joint product, it is necessary to perform cutting on the friction-welded joint product, which significantly increases the processing cost.

  On the other hand, in the technique disclosed in Japanese Translation of PCT International Publication No. 2006-509172, as shown in paragraph 0017 of FIG. 1B and FIG. 1B in particular, the first differential case as the first intermediate processed product and the second intermediate processed product The second differential case having the ring gear is fixed and joined by laser welding to form a differential case as a joined product. In this way, when the first differential case and the second differential case are fixed and welded, if the axis of the first differential case and the axis of the second differential case are adjusted to coincide with each other at the time of fixing, they are joined and formed. Even in the differential case, the axial center does not deviate and the required accuracy can be obtained.

However, since the ring gear requires high strength, it is often composed of high carbon steel containing a large amount of C (carbon). In such a case, when the second differential case made of high carbon steel is exposed to fusion welding such as laser welding, the melted joint of the high carbon steel may harden and cracks may occur in the joint. That is, there may be a problem that the strength of the joint portion between the first differential case and the second differential case becomes weak.
Japanese Patent Laid-Open No. 5-84614 JP-T-2006-509172

  The present invention has been made in order to solve the above-mentioned problems, and is a fusion-bonded product comprising a high carbon steel portion having a high strength portion and a low carbon steel portion, and having a high strength portion having a required accuracy. Then, it aims at providing the fusion | melting joining product which can maintain the required intensity | strength in a junction part. Moreover, it aims at providing the manufacturing method.

  The present invention includes a first low carbon steel portion made of a low carbon steel having a C content of less than 0.45%, a high carbon steel portion made of a high carbon steel having a C content of 0.45% or more, A first intermediate processed product that is formed by integral friction welding, and a second intermediate processed product having a second low carbon steel portion made of a second low carbon steel having a C content of less than 0.45%, The high-carbon steel portion of the first intermediate processed product is provided with a high-strength portion that is previously molded and quenched into a desired shape, and the second low-carbon steel portion of the second intermediate processed product is The first low-carbon steel part of the first intermediate processed product and the second low-carbon steel part of the second intermediate processed product are joined to each other by fusion welding. It is a melt bonded product having a high strength part.

  According to the present invention, the required strength can be obtained by quenching the high strength portion of the high carbon steel portion of the first intermediate processed product. In addition, since the first low carbon steel part of the first intermediate processed product and the second low carbon steel part of the second intermediate processed product are joined by fusion welding, hardening by melting the high carbon steel part at the joint. Is prevented, and the occurrence of cracks due to the curing can be prevented. That is, the required strength can be maintained at the joint between the first intermediate processed product and the second intermediate processed product. Moreover, since fusion welding can be performed in a state in which the first intermediate processed product and the second intermediate processed product are fixed, it is easy to obtain a joined product having a required accuracy. Further, the first material is formed by friction welding a high carbon steel having a C content of 0.45% or more and a low carbon steel having a C content of less than 0.45%, and then having a predetermined shape. Therefore, the deviation of the axial center of the first material and the variation in the axial length due to the friction welding can be corrected in the subsequent molding process.

  For example, the high-strength portion can be formed into a tooth profile.

  Further, for example, the first intermediate processed product constitutes a first differential case, the second intermediate processed product constitutes a second differential case, and the first low carbon steel portion and the second intermediate processed product of the first intermediate processed product. The second low carbon steel portion is joined by fusion welding to form a differential case. In this case, joining parts such as bolts can be reduced, and the weight of the differential case can be reduced.

  The C content in the high carbon steel portion is, for example, about 0.45% to 0.60%. The C content in the first low carbon steel portion is, for example, 0.10% to 0.40%. Further, the C content in the second low carbon steel portion is, for example, 0.10% to 0.40%.

  The present invention also includes a first preliminary material made of a low carbon steel having a C content of less than 0.45%, a second preliminary material made of a high carbon steel having a C content of 0.45% or more, A step of forming an integral first material by friction welding, a step of removing burrs due to friction welding of the first material, and a quenching schedule of a predetermined shape in the region of the second preliminary material of the first material Forming a part, forming a first low carbon steel portion of a predetermined shape in the first preliminary material region of the first material, and forming a first intermediate processed product; A second intermediate having a second low carbon steel portion of a predetermined shape from a step of quenching to form a high strength portion and a second material comprising a second low carbon steel having a C content of less than 0.45% The process of forming the processed product, the first low carbon steel part of the first intermediate processed product and the second low of the second intermediate processed product. And Motoko portion, a manufacturing method of melt bonding products having a high strength part characterized by comprising the steps of joining by fusion welding.

  According to the present invention, a high strength portion having a required strength can be obtained by quenching a planned quenching portion made of high carbon steel. In addition, since the first low carbon steel portion of the first intermediate processed product and the second low carbon steel portion of the second intermediate processed product are joined by fusion welding, the high carbon steel portion is hardened by melting at the joint. Occurrence is prevented, and generation of cracks due to the curing can be prevented. That is, the required strength can be maintained at the joint between the first intermediate processed product and the second intermediate processed product. Moreover, since fusion welding can be performed in a state in which the first intermediate processed product and the second intermediate processed product are fixed, it is easy to obtain a joined product having a required accuracy. Further, a high carbon steel (second preliminary material) having a C content of 0.45% or more and a low carbon steel (first preliminary material) having a C content of less than 0.45% are friction welded. Since one material is molded and then formed into a first intermediate processed product of a predetermined shape, the axial displacement and axial length variation of the first material due to friction welding can be corrected in the subsequent molding process. is there.

  For example, a predetermined quenching portion can be formed by forging. The first low carbon steel portion having a predetermined shape can also be formed by forging. Furthermore, the second low carbon steel portion having a predetermined shape can also be formed by forging. In these cases, the yield of the first material or the second material is good. Moreover, since the shift of the axial center of the first material and the variation in the length in the axial direction due to the friction welding can be corrected during the forging process, the processing cost can be reduced.

  The above considerations are mainly made on carbon steel materials whose properties are generally determined by the amount of carbon. The present inventor further studied structural steel materials whose properties are affected by the amount of steel components other than carbon. As a result, it was found that such structural steel should be based on carbon equivalent instead of carbon content.

The carbon equivalent is defined in JIS as follows.
Carbon equivalent = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14
Here, C is carbon amount (%), Mn is manganese amount (%), Si is silicon amount (%), Ni is nickel amount (%), Cr is chromium amount (%), Mo is molybdenum amount (%) , V is the amount of vanadium (%).

  And if carbon steel material of the carbon amount of "0.45%" which is the threshold value which this inventor discovered initially is converted using the component data of general carbon steel materials (for example, S45C etc.), "0.60% It is equivalent to a structural steel material having a carbon equivalent of "", and it was actually confirmed that such substitution is possible in the present invention. (An example of S45C: C = 0.46, Mn = 0.72, Si = 0.18, Ni = 0.04, Cr = 0.11, V = 0.00: Carbon content = 0.46%, carbon Equivalent = 0.613%)

  That is, in the present invention, a first steel material portion made of a steel material having a carbon equivalent of less than 0.60% and a quenching steel material portion made of a steel material having a carbon equivalent of 0.60% or more are integrated by friction welding. A first intermediate processed product, and a second intermediate processed product having a second steel material portion made of a steel material having a carbon equivalent of less than 0.60%. , A high-strength portion that has been molded and hardened in a desired shape in advance is provided, and the second steel material portion of the second intermediate processed product is previously molded into a predetermined shape, and the first intermediate processed product is The steel material part and the second steel material part of the second intermediate processed product are melt-bonded products having a high-strength part characterized by being joined by fusion welding.

  According to the present invention, the required strength can be obtained by quenching the high strength portion of the steel material portion for quenching of the first intermediate processed product. In addition, since the first steel material portion of the first intermediate processed product and the second steel material portion of the second intermediate processed product are joined by fusion welding, hardening due to melting of the steel material portion for quenching may occur in the joint portion. It is prevented, and the generation | occurrence | production of the crack by the said hardening can be prevented. That is, the required strength can be maintained at the joint between the first intermediate processed product and the second intermediate processed product. Moreover, since fusion welding can be performed in a state in which the first intermediate processed product and the second intermediate processed product are fixed, it is easy to obtain a joined product having a required accuracy. Further, the first material is formed by friction welding a steel material for quenching having a carbon equivalent of 0.60% or more and a first steel material having a carbon equivalent of less than 0.60%, and then a first intermediate having a predetermined shape. Since it can be formed into a processed product, the deviation of the axial center of the first material and the variation in the axial length due to friction welding can be corrected in the subsequent forming process.

  Also in this case, for example, the high-strength portion can be formed in a tooth profile.

  Also in this case, for example, the first intermediate processed product constitutes the first differential case, the second intermediate processed product constitutes the second differential case, and the first steel material portion and the second intermediate processed product of the first intermediate processed product The second steel material part of the processed product can be joined by fusion welding to form a differential case. In this case, joining parts such as bolts can be reduced, and the weight of the differential case can be reduced.

When the first steel part of the first intermediate product and the second steel part of the second intermediate product are joined by fusion welding, the value of the hot cracking susceptibility of the first steel part and the high temperature of the second steel part If the sum with the value of crack sensitivity is 7 or less, the occurrence of cracks can be prevented more reliably. Here, the value of hot cracking sensitivity is calculated by the following equation.
Hot cracking susceptibility = 1000 × C (S + P + (Si / 25) + (Ni / 100)) / (3Mn + Cr + Mo + V)
Here, C is the carbon content (%), S is the sulfur content (%), P is the phosphorus content (%), Si is the silicon content (%), Ni is the nickel content (%), and Mn is the manganese content (%). Cr is the chromium content (%), Mo is the molybdenum content (%), and V is the vanadium content (%).

  In the present invention, the first preliminary material made of a steel material having a carbon equivalent of less than 0.60% and the second preliminary material made of a steel material having a carbon equivalent of 0.60% or more are friction-welded to form an integrated first material. A step of forming one material, a step of removing burrs due to friction welding of the first material, a portion to be quenched of a predetermined shape in the region of the second preliminary material of the first material, and the first A step of forming a first steel material portion having a predetermined shape in a region of a first preliminary material of one material to form a first intermediate processed product, and a step of quenching the portion to be quenched and forming a high strength portion And forming a second intermediate processed product having a second steel material portion of a predetermined shape from a second material made of a second steel material having a carbon equivalent of less than 0.60%, and a first of the first intermediate processed product Weld the steel part and the second steel part of the second intermediate processed product by fusion welding. A step of a manufacturing method of melt bonding products having a high strength part characterized by comprising a.

  According to the present invention, the required strength can be obtained by quenching the quenching planned portion made of the second preliminary material. In addition, since the first steel material part of the first intermediate processed product and the second steel material part of the second intermediate processed product are joined by fusion welding, it is prevented that the second preliminary material is cured due to melting at the joint. And generation of cracks due to the curing can be prevented. That is, the required strength can be maintained at the joint between the first intermediate processed product and the second intermediate processed product. Moreover, since fusion welding can be performed in a state where the first intermediate processed product and the second intermediate processed product are fixed, it is easy to obtain a joined product having a required accuracy. Further, the first preliminary material is formed by friction welding the second preliminary material having a carbon equivalent of 0.60% or more and the first preliminary material having a carbon equivalent of less than 0.60%, and then the first preliminary material having a predetermined shape is formed. Since it is formed into an intermediate processed product, the shift of the axial center of the first material and the variation in the axial length due to friction welding can be corrected in the subsequent forming process.

  Also in this case, for example, the quenching planned portion having a predetermined shape can be formed by forging. The first steel material portion having a predetermined shape can also be formed by forging. Furthermore, the second steel material portion having a predetermined shape can also be formed by forging. In these cases, the yield of the first material or the second material is good. Moreover, since the shift of the axial center of the first material and the variation in the length in the axial direction due to the friction welding can be corrected during the forging process, the processing cost can be reduced.

  Also in this case, when the first steel material part of the first intermediate processed product and the second steel material part of the second intermediate processed product are joined by fusion welding, the value of the hot crack susceptibility of the first steel material part and the second If the sum with the value of the hot cracking susceptibility of the steel part is 7 or less, the occurrence of cracking can be prevented more reliably.

  FIG. 1 is a cross-sectional view of a differential apparatus that is a fusion bonded product according to an embodiment of the present invention. 2A and 2B are cross-sectional views illustrating a first material forming step in the manufacturing method according to the embodiment of the present invention. 3A and 3B are cross-sectional views for explaining a molding process for molding the first differential case from the first material in the manufacturing method according to the embodiment of the present invention. FIG. 4 is a cross-sectional view of the first intermediate processed product in the melt-bonded product according to the embodiment of the present invention. 5A to 5C are cross-sectional views illustrating a molding process for molding a second intermediate processed product from the second material in the manufacturing method according to the embodiment of the present invention. FIG. 6 is a cross-sectional view of a differential apparatus that is a fusion-bonded product according to an embodiment of the present invention before welding.

  First, the differential apparatus 1 will be described with reference to FIG. A differential case 2 of a differential device 1 that is a melt-bonded product according to an embodiment of the present invention includes a first differential case 2a that is a first intermediate processed product and a second differential case 2b that is a second intermediate processed product. Yes. The first differential case 2a has a first boss portion 13 extending in the axle direction and a high carbon steel portion H having a C content of 0.45% or more and a C content of less than 0.45%. And a first low carbon steel portion L1. The second differential case 2b includes a second low carbon steel portion L2 having a second boss portion 14 formed in the axle direction and having a C content of less than 0.45%.

  The content of C in the high carbon steel portion H is, for example, about 0.45% to 0.60%. Further, the content of C in the first low carbon steel portion L1 is, for example, 0.10% to 0.40%. Further, the C content in the second low carbon steel portion L2 is, for example, 0.10% to 0.40%.

  A tooth profile 9 that is a high-strength portion is formed in the high carbon steel portion H of the first differential case 2a. In the first low carbon steel portion L1 of the first differential case 2a, a differential case hole 10 for inserting a pinion shaft 3 to be described later into the first differential case 2a and a fixing pin 15 to be described later are inserted into the first differential case 2a. A fixing pin insertion hole 16 and a recess 11 for fitting are formed. Moreover, the convex part 12 for fitting is shape | molded by the 2nd low carbon steel part L2 of the 2nd differential case 2b. The concave portion 11 for fitting and the convex portion 12 for fitting are joined together by any one welding method of electron beam welding, laser welding, and resistance welding. Thus, the differential case 2 is configured.

  In the differential case 2, there are a pinion shaft 3 that rotates integrally with the differential case 2, a fixing pin 15 that fixes the pinion shaft 3 in the differential case 2, and a pinion gear that is rotatably supported by the pinion shaft 3 that is inserted into the differential case hole 10. 6, pinion gear thrust washer 4 mounted between pinion gear 6 and differential case 2, first side gear 17 and second side gear 18 meshing with pinion gear 6, first side gear 17 and second side gear 18 and differential case 2 A side gear thrust washer 5 is disposed.

  Next, a method for forming the first differential case 2a will be described with reference to FIGS. 2A to 4.

  As shown in FIG. 2A, first, a first preliminary material 20 of low carbon steel having a C content of less than 0.45% and a second high carbon steel having a C content of 0.45% or more. The spare material 21 is prepared. The first preliminary material 20 and the second preliminary material 21 are attached to a friction welding apparatus (not shown), and only the first preliminary material 20 is friction-welded to the second preliminary material 21 while being rotated at a high speed. Thereby, as shown in FIG. 2B, the first preliminary material 20 and the second preliminary material 21 are joined, and the first material 23 having the burr 22 around the joint portion is formed.

  Next, the burr | flash of the 1st raw material 23 is removed, and as shown to FIG. 3A, the content of C is the high carbon steel part H which is 0.45% or more, and the content of C is less than 0.45% The first raw material 23 having the first low carbon steel portion L1 is formed. In the friction welding here, since the first preliminary material 20 and the second preliminary material 21 are joined by softening, the occurrence of blowholes at the joint and cracking due to hardening at the joint are prevented. The That is, the first material 23 having the high carbon steel portion H and the first low carbon steel portion L1 is firmly and integrally joined.

  The first material 23 has a tooth profile that is a quenching planned portion 9a, a first boss portion 13, and a region of a high carbon steel portion H having a C content of 0.45% or more by plastic deformation by hot forging, The first through hole 31 inside the first boss portion 13 is formed. A first preliminary gear chamber 32 is formed inside the high carbon steel portion H and the low carbon steel portion L1. Further, a circumferential fitting recess 11 is formed at the outer peripheral end of the low carbon steel portion L1. Thus, the preliminary first differential case 30 is completed.

  As shown in FIG. 4, the first through hole 31 of the preliminary first differential case 30 is finished with an inner diameter, and the first lubricating groove 33 is cut. Further, the inside of the first preliminary gear chamber 32 is cut so as to correspond to the shapes of the pinion gear thrust washer 4 and the side gear thrust washer 5 that are in contact with each other, thereby forming the first gear chamber 35. Further, the differential case hole 10 is cut between the outer periphery of the preliminary first differential case 30 and the first gear chamber 35, and the fixed pin insertion hole 16 is cut so as to be orthogonal to the differential case hole 10. In addition, the tooth profile which is the quenching scheduled portion 9a is also cut into a required shape. Then, induction hardening is performed only on the tooth profile portion which is the quenching scheduled portion 9a, and the first differential case 2a having the tooth profile 9 having a required shape and hardness is completed.

  Next, a method for forming the second differential case 2b will be described with reference to FIG. First, as shown in FIG. 5A, a second material 40 made of low carbon steel having a C content of less than 0.45% is prepared. Then, by hot forging, as shown in FIG. 5B, the second boss portion 14 is formed outside, the second through hole 41 and the second auxiliary gear chamber 42 are formed inside, and the auxiliary first end is formed at the outer peripheral end portion. The circumferential fitting convex portion 12 that fits with the fitting concave portion 11 of the differential case 30 is formed, and the preliminary second differential case 50 is completed.

  Then, as shown in FIG. 5C, the inside of the second preliminary gear chamber 42 is cut so as to correspond to the shapes of the pinion gear thrust washer 4 and the side gear thrust washer 5, so that the second gear chamber 45 is formed. It is formed. The second through hole 41 is finished with an inner diameter, and the second lubricating groove 43 is cut. Thus, the second differential case 2b is completed.

  Next, a method for assembling the differential device 1 will be described with reference to FIG.

  First, in the first differential case 2a, the first side gear 17 with the side gear thrust washer 5 attached on the side opposite to the tooth profile side is arranged so that the tooth profile side of the first side gear 17 faces the differential case center Y. Placed on X.

  Next, the pinion gear 6 to which the pinion gear thrust washer 4 is attached on the opposite tooth side is placed on the first side gear 17. At this time, the tooth profile of each pinion gear 6 faces the rotation axis X of the differential case 2 and faces each other around the differential case rotation axis X. Further, the pinion gear hole 7 of the pinion gear 6, the differential case hole 10 of the first differential case 2a, and the hole of the pinion gear thrust washer 4 are aligned on the same straight line.

  Then, the pinion shaft 3 passes through the differential case hole 10, the pinion gear thrust washer 4 and the pinion gear hole 7 formed in the pinion gear 6, and is inserted to the rotational axis X of the differential case 2. It is guided to the pinion gear hole 7 symmetrical with respect to X, the hole of the thrust washer 4 for pinion gear, and the differential case hole 10. Next, the pinion gear 6 is positioned in the first differential case 2a. Then, the fixing pin 15 is inserted into the fixing pin insertion hole 16 of the first differential case 2 a and the fixing pin insertion hole 19 of the pinion shaft 3. As a result, the pinion gear 6 is assembled to the first differential case 2a so as not to come off.

  Subsequently, the second side gear 18 to which the side gear thrust washer 5 is attached on the side opposite to the tooth shape is placed on the pinion gear 6. At this time, the second side gear 18 is placed so that the tooth profile thereof faces the pinion gear 6 side.

  And the fitting convex part 12 of the 2nd differential case 2b and the recessed part 11 for fitting of the 1st differential case 2a are fitted. And the recessed part 11 for fitting of the 1st low carbon steel part L1 and the fitting convex part 12 of the 2nd low carbon steel part L2 are melt-bonded by electron beam welding, and the assembly | attachment of the differential case 2 of the differential apparatus 1 is completed. .

  According to the differential case 2 as described above, the high strength portion 9 having a required strength can be obtained by quenching the planned quenching portion 9a of the high carbon steel portion H of the first differential case 2a. Further, since the first low carbon steel portion L1 of the first differential case 2a and the second low carbon steel portion L2 of the second differential case 2b are joined by electron beam welding, the high carbon steel portion H is melted at the joint. Curing does not occur, and generation of cracks due to the curing can be prevented. That is, a required strength can be obtained at the joint between the first differential case 2a and the second differential case 2b. Further, since the electron beam welding can be performed with the first differential case 2a and the second differential case 2b being fixed, it is easy to obtain a joined product having a required accuracy. Further, the first material 23 is formed by friction welding a high carbon steel having a C content of 0.45% or more and a low carbon steel having a C content of less than 0.45%, and then has a predetermined shape. Since the first differential case 2a is molded, the shift of the axial center of the first material 23 and the variation in the length in the axial direction due to the friction welding can be corrected in the subsequent molding process.

  Moreover, joining parts, such as a volt | bolt, can be decreased by joining the 1st differential case 2a and the 2nd differential case 2b by welding. That is, the number of parts of joint parts such as bolts can be reduced. Accordingly, the weight reduction of the differential case 2 can be realized.

  In addition, when forming the tooth profile that is the quenching scheduled portion 9a, forming the first differential case 2a, and forming the second differential case 2b are performed by forging, the first differential case 2a and the second differential case 2a are formed by cutting. The yield of the differential case 2b is good. In addition, since the displacement of the axial center of the first material 23 and the variation in the length in the axial direction due to the friction welding can be corrected during the forging process, it is possible to reduce the processing cost required to achieve the required dimensional accuracy.

  In the above embodiment, the tooth profile is formed as the high-strength portion 9, but the portion requiring high strength may be formed in a different shape. The first differential case 2a and the second differential case 2b after the friction welding process may be formed by hot forging, cold forging, warm forging, or cutting.

  In the above embodiment, the differential case 2 has been described. However, the present invention can also be applied to different bonded products. Further, as an example of melting and joining the first differential case 2a and the second differential case 2b, joining by electron beam welding has been described. However, even if other melting welding such as laser welding or resistance welding is used. Good.

  Further, the fitting recess 11 is formed in the first differential case 2a, and the fitting convex portion 12 is formed in the second differential case 2b, and positioning is performed during welding, but the fitting protrusion 11 is formed in the first differential case 2a. A part may be shape | molded and the recessed part for fitting may be shape | molded in the 2nd differential case 2b, and positioning may be performed.

  Moreover, although the 2nd differential case 2b is comprised only from the 2nd low carbon steel part L2, if the junction part by fusion welding is a low carbon steel part, it may have a high carbon steel part.

  Moreover, although induction hardening is employ | adopted as quenching, carburizing quenching may be employ | adopted in order to raise an altitude further.

  The above explanation is mainly made on carbon steel materials whose properties are generally determined by the amount of carbon. The present inventor further studied structural steel materials whose properties are affected by the amount of steel components other than carbon. As a result, it was found that such structural steel should be based on carbon equivalent instead of carbon content.

The carbon equivalent is defined in JIS as follows.
Carbon equivalent = C + Mn / 6 + Si / 24 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14
Here, C is carbon amount (%), Mn is manganese amount (%), Si is silicon amount (%), Ni is nickel amount (%), Cr is chromium amount (%), Mo is molybdenum amount (%) , V is the amount of vanadium (%).

  And if carbon steel material of the carbon amount of "0.45%" which is the threshold value which this inventor discovered initially is converted using the component data of general carbon steel materials (for example, S45C etc.), "0.60% It is equivalent to a structural steel material having a carbon equivalent of "", and it was actually confirmed that such substitution is possible in the present invention. (An example of S45C: C = 0.46, Mn = 0.72, Si = 0.18, Ni = 0.04, Cr = 0.11, V = 0.00: Carbon content = 0.46%, carbon Equivalent = 0.613%)

That is, in contrast to the above embodiment, instead of the high carbon steel portion H, a steel material (quenching steel material) having a carbon equivalent of 0.60% or more can be used, and the first low carbon steel portion L1 Instead, the first steel material portion made of a steel material having a carbon equivalent of less than 0.60% can be used,
Instead of the second low carbon steel portion L2, a second steel material portion made of a steel material having a carbon equivalent of less than 0.60% can be used.

  Even in this case, the high strength portion 9 having the required strength can be obtained by quenching the quenching planned portion 9a of the quenching steel H of the first differential case 2a. Also, the first steel material portion L1 of the first differential case 2a and the second steel material portion L2 of the second differential case 2b are joined by electron beam welding or the like, and hardening due to melting of the quenching steel material H does not occur at the joined portion. The occurrence of cracks due to the curing can be prevented. That is, a required strength can be obtained at the joint between the first differential case 2a and the second differential case 2b. Further, since the electron beam welding can be performed in a state where the first differential case 2a and the second differential case 2b are fixed, it is easy to obtain a joined product having a required accuracy. Furthermore, the first material 23 is formed by friction welding the steel material H for quenching with a carbon equivalent of 0.60% or more and the first steel material part with a carbon equivalent of less than 0.60%, and then the first material 23 having a predetermined shape is formed. By forming the differential case 2a, the displacement of the axial center of the first material 23 and the variation in the length in the axial direction due to the friction welding can be corrected in the subsequent forming process.

When the first steel part L1 of the first intermediate product and the second steel part L2 of the second intermediate product are joined by fusion welding, the value of the hot cracking susceptibility of the first steel part and the second steel part When the sum of the hot cracking susceptibility value is 7 or less, the occurrence of cracking can be prevented more reliably. Here, the value of hot cracking sensitivity is calculated by the following equation.
Hot cracking susceptibility = 1000 × C (S + P + (Si / 25) + (Ni / 100)) / (3Mn + Cr + Mo + V)
Here, C is the carbon content (%), S is the sulfur content (%), P is the phosphorus content (%), Si is the silicon content (%), Ni is the nickel content (%), and Mn is the manganese content (%). Cr is the chromium content (%), Mo is the molybdenum content (%), and V is the vanadium content (%).

  FIG. 7 shows data of steel materials actually examined by the present inventors. In the table, Ceq is carbon equivalent, and HCS is hot cracking sensitive. And the evaluation result at the time of using each steel materials shown by FIG. 7 as the steel materials H for quenching thru | or the steel materials L1 and L2 for fusion joining in the said embodiment is shown in FIG.8 and FIG.9.

  As shown in FIG. 8, S45C, S50C, and S55C were preferable as the steel material H for quenching from the viewpoint of the hardness (strength) of the tooth profile 9 after quenching. The other steel materials could not achieve the desired tooth profile height, and were not suitable as a steel material H for quenching.

  On the other hand, as shown in FIG. 9, the suitability of the steel materials L1 and L2 for fusion bonding was determined with a carbon amount of 0.45% to a carbon equivalent of 0.60% as a threshold value. It has also been found that when the sum of the hot cracking susceptibility values of the two steel materials to be joined is 7 or less, the occurrence of cracking is more reliably prevented.

  Needless to say, when selecting a steel material, its workability is also taken into account (a steel material with poor workability that makes it difficult to perform desired processing is not used).

Sectional drawing of the differential case of the differential apparatus which is a fusion | melting joining product of one embodiment of this invention. It is sectional drawing explaining the formation process of the 1st raw material in the manufacturing method of one embodiment of this invention. It is sectional drawing explaining the formation process of the 1st raw material in the manufacturing method of one embodiment of this invention. Sectional drawing explaining the formation process which shape | molds the 1st differential case from the 1st raw material in the manufacturing method of one embodiment of this invention. Sectional drawing explaining the formation process which shape | molds the 1st differential case from the 1st raw material in the manufacturing method of one embodiment of this invention. Sectional drawing of the 1st intermediate process product in the fusion-bonded product of one embodiment of this invention. Sectional drawing explaining the formation process which shape | molds the 2nd intermediate processed product from the 2nd raw material in the manufacturing method of one embodiment of this invention. Sectional drawing explaining the formation process which shape | molds the 2nd intermediate processed product from the 2nd raw material in the manufacturing method of one embodiment of this invention. Sectional drawing explaining the formation process which shape | molds the 2nd intermediate processed product from the 2nd raw material in the manufacturing method of one embodiment of this invention. Sectional drawing of the state before welding of the differential case of the differential apparatus which is a fusion | melting joining product of one embodiment of this invention. The table | surface which shows the data of the steel materials which this inventor actually examined. The table | surface which shows the evaluation result as steel materials for hardening about the steel materials of FIG. The table | surface which shows the evaluation result as a steel material for fusion welding about the steel material of FIG.

Claims (19)

First low carbon steel part (L1) made of low carbon steel with a C content of less than 0.45% and high carbon steel part (H) made of high carbon steel with a C content of 0.45% or more And a first intermediate processed product (2a) configured to be integrated by friction welding,
A second intermediate processed product (2b) having a second low carbon steel portion (L2) made of a second low carbon steel having a C content of less than 0.45%;
With
The high-carbon steel part (H) of the first intermediate processed product (2a) is provided with a high-strength part (9) that has been molded and hardened in a desired shape in advance,
The second low carbon steel part (L2) of the second intermediate processed product (2b) is previously molded into a predetermined shape,
The first low carbon steel part (L1) of the first intermediate processed product (2a) and the second low carbon steel part (L2) of the second intermediate processed product (2b) are joined by fusion welding. A fusion bonded product having a high strength part. The fusion-bonded product having a high-strength portion according to claim 1, wherein the high-strength portion (9) has a tooth profile. The first intermediate processed product (2a) constitutes the first differential case,
The second intermediate processed product (2b) constitutes the second differential case,
The first low carbon steel part (L1) of the first intermediate processed product (2a) and the second low carbon steel part (L2) of the second intermediate processed product (2b) are joined by fusion welding to obtain a differential case (2 The melt-bonded product having a high-strength portion according to claim 2. The melt-bonded product having a high-strength portion according to any one of claims 1 to 3, wherein the content of C in the high carbon steel portion (H) is 0.45% to 0.60%. The content of C in the first low carbon steel portion (L1) is 0.10% to 0.40%, and the fusion bonding having a high strength portion according to any one of claims 1 to 4 Product. The fusion bonding having a high strength portion according to any one of claims 1 to 5, wherein the content of C in the second low carbon steel portion (L2) is 0.10% to 0.40%. Product. A first preliminary material (20) made of a low carbon steel having a C content of less than 0.45%, and a second preliminary material (21) made of a high carbon steel having a C content of 0.45% or more, Forming a first integrated material (23) by friction welding,
Removing the burrs (22) due to friction welding of the first material (23);
In the region of the second preliminary material (21) of the first material (23), a quenching planned portion (9a) having a predetermined shape is formed, and the first preliminary material (20) of the first material (23) is formed. Forming a first low carbon steel portion (L1) having a predetermined shape in a region to form a first intermediate processed product (2a);
Quenching the portion to be quenched (9a) to form a high strength portion (9);
A second intermediate processed product (2b) having a second low carbon steel portion (L2) of a predetermined shape from a second material (40) made of a second low carbon steel having a C content of less than 0.45% Forming, and
Joining the first low carbon steel part (L1) of the first intermediate processed product (2a) and the second low carbon steel part (L2) of the second intermediate processed product (2b) by fusion welding;
A method for producing a fusion bonded product having a high-strength portion. The method for producing a fusion-bonded product having a high-strength portion according to claim 7, wherein the quenching scheduled portion (9 a) having a predetermined shape is formed by forging. The method for producing a fusion bonded product having a high strength portion according to claim 7 or 8, wherein the first low carbon steel portion (L1) having a predetermined shape is formed by forging. The method for producing a fusion bonded product having a high strength portion according to any one of claims 7 to 9, wherein the second low carbon steel portion (L2) having a predetermined shape is formed by forging. The first steel material portion (L1) made of a steel material having a carbon equivalent of less than 0.60% and the quenching steel material portion (H) made of a steel material having a carbon equivalent of 0.60% or more are integrated by friction welding. A first intermediate processed product (2a) configured;
A second intermediate processed product (2b) having a second steel part (L2) made of a steel having a carbon equivalent of less than 0.60%;
With
The steel material portion (H) for quenching of the first intermediate processed product (2a) is provided with a high-strength portion (9) that has been molded and hardened in a desired shape in advance.
The second steel material portion (L2) of the second intermediate processed product (2b) is previously formed into a predetermined shape,
High strength, characterized in that the first steel part (L1) of the first intermediate product (2a) and the second steel part (L2) of the second intermediate product (2b) are joined by fusion welding. Fusion-bonded product having a part. The melt-bonded product having a high-strength portion according to claim 11, wherein the high-strength portion (9) has a tooth profile. The first intermediate processed product (2a) constitutes the first differential case,
The second intermediate processed product (2b) constitutes the second differential case,
The first steel material portion (L1) of the first intermediate processed product (2a) and the second steel material portion (L2) of the second intermediate processed product (2b) are joined by fusion welding to form the differential case (2). The melt-bonded product having a high-strength portion according to claim 12. The first steel part (L1) and the second steel part so that the sum of the value of the hot cracking susceptibility of the first steel part (L1) and the value of the hot cracking susceptibility of the second steel part (L2) is 7 or less. (L2) is selected, The fusion-bonded product having a high-strength portion according to any one of claims 11 to 13. A first preliminary material (20) made of a steel material having a carbon equivalent of less than 0.60% and a second preliminary material (21) made of a steel material having a carbon equivalent of 0.60% or more are friction welded to form an integral first material. Forming one material (23);
Removing the burrs (22) due to friction welding of the first material (23);
A pre-quenched portion having a predetermined shape is formed in the region of the second preliminary material (21) of the first material (23), and predetermined in the region of the first preliminary material (20) of the first material (23). Forming a first steel material part (L1) of the shape of and forming a first intermediate processed product (2a);
Quenching the portion to be quenched (9a) to form a high strength portion (9);
Forming a second intermediate processed product (2b) having a second steel material portion (L2) having a predetermined shape from the second material (40) made of the second steel material having a carbon equivalent of less than 0.60%;
Joining the first steel part (L1) of the first intermediate processed product (2a) and the second steel part (L2) of the second intermediate processed product (2b) by fusion welding;
A method for producing a fusion bonded product having a high-strength portion. The method for producing a fusion-bonded product having a high-strength portion according to claim 15, wherein the quenching scheduled portion (9 a) having a predetermined shape is formed by forging. The method for producing a fusion-bonded product having a high-strength portion according to claim 15 or 16, wherein the first steel material portion (L1) having a predetermined shape is formed by forging. The method for producing a fusion-bonded product having a high-strength portion according to any one of claims 15 to 17, wherein the second steel material portion (L2) having a predetermined shape is formed by forging. The first preliminary material (20) and the second material (40) so that the sum of the hot cracking susceptibility value of the first preliminary material (20) and the hot cracking sensitivity value of the second material (40) is 7 or less. The method for producing a fusion-bonded product having a high-strength portion according to any one of claims 15 to 18, wherein:

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