JP2014091125A - Steel component different in carbon content and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel component different in a carbon content the manufacturing cost of which can be largely reduced, and to provide a method of manufacturing the steel component.SOLUTION: A steel component 20 different in a carbon content is composed of a shaft component 5 formed in a shaft shape and a gear component 10 having a through-hole 7 in which the shaft component 5 can be mounted. The shaft component 5 and the gear component 10 are each formed by heading, and after pressing in these shaft component 5 and gear component 10, a joined interface 20 contacting with the shaft component 5 and the gear component 10 by press-in, is integrally formed by diffusion joining, and the steel component is formed by at least any one work of varnishing work of finishing the joined interface of the shaft component 5 by form-rolling and work of finishing the joined interface of the gear component 10 by blanking. Thereby, manufacturing cost of the steel component 20 can be largely reduced more than conventional ones, and strong joining can also be materialized.

Description

  The present invention relates to a steel part having a different carbon content and a manufacturing method thereof, which can reduce the manufacturing cost of a steel part in which a gear part having a low carbon content and a shaft part having a higher carbon content than the gear part are joined.

  A conventional steel part 100 and a manufacturing method thereof will be described below with reference to FIGS. First, a conventional steel part 100 is configured by integrally forming a shaft part 105 provided with a driving hole 101 that engages with a bit (not shown) at the tip and a gear part 110 fixed to the shaft part 105. Yes. Further, according to the description in Patent Document 1, the steel material part 100 is used as an optical axis adjustment part of a vehicle lamp, and is particularly adopted in an automobile part. The shaft part 105 includes a shaft part 103 that can be inserted into the through hole 107 of the gear part 110 and a head part 102 formed at one end thereof. On the other hand, the gear part 110 includes a gear 106 formed on the outer periphery thereof and a through hole 107 formed in the center. Further, the shaft portion 103 is formed with a flange portion 104 that contacts the end surface of the gear part 110, and the head portion 102 is formed with the drive hole 101.

  Next, in the conventional method of manufacturing the steel material part 100, the gear part 110 and the shaft part 105 are separately pressed as shown in FIG. 6, and then assembled to each other and spot welding or projection welding (welding operation of FIG. 6). To fix). Thereafter, a quenching operation for the purpose of improving the strength of the gear 106 is performed. The brim portion 104 is a portion in contact with an electrode of a welding machine (not shown) that performs this spot welding or projection welding, and is an essential configuration for the shaft component 105. In the case of projection welding, a plurality of protrusions 104 a are formed on the flange 104.

  That is, since the welding operation is essential for manufacturing the steel material part 100 and a large amount of capital investment is required for the welding machine, the conventional steel material part 100 and the manufacturing method thereof have a problem that the manufacturing cost is high. there were.

  Therefore, the inventor of the present application has studied the manufacturing method of the steel material part 100 ′ shown in FIG. 7 by using the diffusion bonding described in Patent Document 2 in the above manufacturing method.

  The diffusion bonding is generally known widely, and parts having different thermal expansion coefficients (the shaft part 105 ′ and the gear part 110 in FIG. 7) are press-fitted and heated, and are integrated using the difference in the thermal expansion coefficient. It is a technology to join. Details of this diffusion bonding will be described later. That is, the steel material part 100 ′ and the manufacturing method thereof replace the above welding operation with the diffusion bonding, and thus the above-described welding machine is not necessary.

  Further, as shown in FIG. 7, the steel material part 100 ′ includes a shaft part 105 ′ integrally including a head 102 and a shaft part 103 ′ disposed at one end, and a gear part 110 having a gear 106 formed on the outer periphery. , Is composed of. Since the gear part 110 is the same as described above, its description is omitted. Since the shaft part 105 ′ is press-fitted as described above, the diameter of the shaft part 103 ′ is set slightly larger than the diameter of the through hole 107 of the gear part 110. Further, since the flange 104 is not formed on the shaft part 105 ′, the second header processing of FIG. 6 is not required in the forging process (FIG. 7) of the shaft 103 ′. That is, the steel part 100 ′ and the manufacturing method thereof can reduce the forging process of the shaft part 105 ′ by one step.

  Therefore, the steel material part 100 ′ and the manufacturing method thereof have an advantage that the manufacturing cost can be reduced as compared with the steel material part 100 and the manufacturing method thereof.

  In addition, it is known that the diffusion bonding has to smooth the surfaces of parts in contact with each other in advance. This is because the area where the shaft portion 103 ′ and the through hole 107 are in contact with each other is increased by press-fitting, and the degree of adhesion at the bonding interface is increased. That is, the smaller the gap existing at the bonding interface, the stronger the bonding state can be obtained. A polishing process is generally known as a processing method for smoothly finishing the surfaces of the shaft portion 103 ′ and the through hole 107 in advance.

  Further, when viewing the Patent Document 2, a plating process is disclosed as a processing method for finishing the joint interface smoothly in advance, whereby the joint strength between the shaft part 105 ′ and the gear part 110 after diffusion joining is disclosed. Is not different from the above polishing process. That is, Patent Document 2 has a feature that it can be performed at a lower cost than a finishing process such as a polishing process because the bonding interface can be finished by plating.

  By the way, the diffusion bonding utilizes the difference in thermal expansion coefficient as described above, and the shaft part 105 ′ disposed on the inner side is selected as a material having a high thermal expansion coefficient, and the gear disposed on the outer side. The part 110 must be selected as a material having a low coefficient of thermal expansion. That is, the shaft part 105 ′ and the gear part 110 are heated at the same time, so that the shaft part 105 ′ expands more than the gear part 110. This is because the shaft portion 103 ′ is strongly constrained by the through hole 107 of the gear part 110, and the gap existing at the joining interface is smaller than before heating.

  This difference in coefficient of thermal expansion can be clarified from a generally known iron-carbon system equilibrium diagram. This iron-carbon equilibrium diagram shows the state of the structure when the carbon steel is held at a certain temperature, and the carbon steel has a lower melting point as the carbon content increases. In addition, carbon steel having a low melting point undergoes thermal expansion at a lower temperature than carbon steel having a high melting point. That is, the coefficient of thermal expansion of carbon steel increases as the melting point decreases and increases as the carbon content increases.

  Accordingly, if the material is carbon steel by joining by diffusion bonding, the shaft part 105 ′ is selected as a material having a high carbon content, while the gear part 110 is selected as a material having a low carbon content. There is a need to.

JP 2004-303523 A Japanese Patent Laid-Open No. 06-047568

  However, in the conventional steel part 100 ′ having a different carbon content and the manufacturing method thereof, since the shaft part 105 ′ or the gear part 110 ′ is plated in advance, as shown in FIG. There is a plating process between the press-fitting operation and the assembly process of diffusion bonding. As a result, there is a problem that the manufacturing cost of the steel material part 100 ′ cannot be significantly reduced because the cost for the plating process is required.

  The present invention was created in view of the above-mentioned problems, and the production cost of the steel parts can be greatly reduced, and the carbon content is different so that a strong bonding state can be obtained by increasing the contact area of the bonding interface. An object is to provide a steel part and a manufacturing method thereof. First, a steel part having a different carbon content according to the present invention includes a first member formed of a shaft-shaped material having a high carbon content, and a material having a low carbon content provided with a mounting hole to which the first member can be attached. The first member and the second member are formed by pressure forming, the first member and the second member are press-fitted, and then the first member and the second member are press-fitted. Formed by at least one of a burnishing process in which the bonding interface of the first member is integrally formed by diffusion bonding, and the bonding interface of the first member is finished by rolling, and a shaving process in which the bonding interface of the second member is finished by punching It is characterized by becoming.

  In addition, it is preferable that the said 1st member and the said attachment hole are dimension-set in the range whose press-fitting allowance is 0.03 mm or more and 0.06 mm or less.

  Furthermore, it is preferable to form a slope at the entrance of the mounting hole.

  Next, the method for manufacturing a steel part having a different carbon content according to the present invention includes a mounting hole in which the carbon content of the first member formed into a shaft shape is increased and the first member can be attached. The carbon content of the two members is set low, the first member and the second member are respectively molded by forging, the first member and the second member are press-fitted, and then the first member and the second member are pressed. The bonding interface is contacted by diffusion bonding, and the forging step includes at least one of a burnishing process that finishes the bonding interface of the first member by rolling and a shaving process that finishes the bonding interface of the second member by punching. It is characterized by including.

  The steel part 20 having a different carbon content according to the present invention is formed by burnishing the shaft portion 3 of the first member or by shaving the through-hole 7 of the second member, and thus it is necessary to finish the joint interface. There is an advantage that the cost is reduced compared to the conventional one. Moreover, since the joining interface is smoothly finished, there is an advantage that strong joining can be realized by the diffusion joining.

  In addition, since the shaft portion 3 and the through hole 7 have a press-fit allowance set in a range of 0.03 mm to 0.06 mm, scratches on the outer periphery of the shaft portion 3 and the inner periphery of the through hole 7 due to press fitting. The sticking can be reduced, and a larger contact area can be secured. For this reason, there also exists an advantage which can perform joining of the axial part 3 and the through-hole 7 after the said diffusion joining reliably.

  Furthermore, since the inclined surface is formed at the inlet of the through hole 7 of the second member, the tip of the shaft portion 3 is gradually guided to the through hole 7 during press-fitting. Thereby, there also exists an advantage which can further reduce the damage | wound of the outer periphery of the axial part 3, and the inner periphery of the through-hole 7, without the front-end | tip of the axial part 3 peeling.

  Moreover, the manufacturing method of the steel material components 20 with different carbon contents of the present invention includes at least one process of burnishing the shaft portion 3 of the first member or shaving the through hole 7 of the second member. Therefore, the cost for finishing the joint interface can be reduced as compared with the conventional case.

It is explanatory drawing which shows one Example of this invention. Moreover, (a) is a side view which shows the completion state of the steel material component of this invention, (b) is explanatory drawing which shows the state before the assembly of (a). It is explanatory drawing which shows the flow of the manufacturing process of this invention. It is explanatory drawing explaining the burnishing of the 1st member of this invention. It is explanatory drawing explaining the shaving process of the 2nd member of this invention. Moreover, (a) is explanatory drawing which shows the process before a 2nd member, (b) is explanatory drawing which shows the process after (a). It is explanatory drawing which shows one conventional Example. Moreover, (a) is a side view which shows the completion state of the conventional steel material components, (b) is explanatory drawing which shows the state before the assembly of (a). It is explanatory drawing which shows the conventional manufacturing process and steel material components. It is explanatory drawing which shows another conventional manufacturing process and steel material components.

  Hereinafter, an embodiment of a steel material part 20 having a different carbon content and a manufacturing method thereof according to the present invention will be described with reference to FIGS. First, as shown in FIGS. 1 (a) and 1 (b), a steel material part 20 having a different carbon content according to the present invention includes a shaft part 5 as an example of a first member formed in a shaft shape, It is comprised from the gear component 10 which is an example of the 2nd member distribute | arranged to the shaft component 5. The shaft component 5 includes a head 2 having a drive hole 1 that engages with a bit (not shown) at one end, and a shaft portion 3 having a diameter smaller than the maximum diameter of the head 2. The head 2 and the shaft 3 are integrally formed. On the other hand, the gear part 10 has a plurality of gears 6 formed on the entire circumference thereof, and is a spur gear in this embodiment. Further, the gear part 10 is provided with a through hole 7 as an example of the mounting hole at the center thereof, and an inclined surface is formed at at least one inlet of the through hole 7. In the present embodiment, the inclined surface is the R portion 7a shown in FIGS. 1A and 2 or the chamfered portion 7b shown in FIG. 4B, and either of them may be formed.

  The steel part 20 is configured such that the gear part 10 rotates integrally with the shaft part 5 by the rotation of the bit, and the shaft part 5 and the gear part 10 are integrally formed by diffusion bonding. It is joined. Since the diffusion bonding utilizes the difference in thermal expansion coefficient as described above, in this embodiment, the shaft part 5 is set to a material having a carbon content of about 0.45%, The gear part 10 is set to a material having a carbon content of about 0.12%.

  Next, the manufacturing method of the steel material components 20 with different carbon contents according to the present invention will be described below. As shown in FIG. 2, the manufacturing method of the steel material part 20 is performed in the order of a forging process, an assembly process, and a heat treatment process.

  The forging step is a step of forming the shaft part 5 or the gear part 10 with a cold forging device. Further, the shaft part 5 is formed through a header process and a burnishing process, which will be described later, while the gear part 10 is formed via a shaving process, which will be described later. , A header device (not shown) for forming the head portion 2, the drive hole 1, and the shaft portion 3 respectively, and a rolling device for performing the burnishing process for finishing the shaft portion 3 with a surface roughness comparable to that of a polishing process. 30 and a pressing device 40 for simultaneously performing the shaving process for finishing the through hole 7 and the inclined surface of the gear part 10 to the surface roughness equivalent to the polishing process and the shaping of the gear 6. That is, the shaft component 5 is forged through the header device and the rolling device 30 in this order.

  As shown in FIG. 3, the rolling device 30 includes a pair of flat dies 31 and 32 facing each other, and any one of the flat dies slides to roll the shaft portion 3 sandwiched therebetween. It is a device that rolls and finishes. For this reason, the flat dies 31 and 32 are each finished with a flat surface in contact with the shaft portion 3. Thus, the finishing process of the shaft part 4 by the rolling device 30 is the burnishing process, and this burnishing process may finish the surface roughness (Rmax) of the shaft part 3 to about 0.8 s. it can. Therefore, since the burnishing is performed by rolling, the machining time can be greatly shortened as compared with general shaft polishing.

  As shown in FIGS. 4A and 4B, the pressing device 40 includes a punching tool 37 that can be lowered and raised, and a receiving jig 35 that receives the material 11, and the punching tool 37 is lowered. Thus, the gear 11 is formed by punching the material 11. The punching tool 37 is formed so as to be capable of punching the material 11, and includes an internal gear 38 for forming the gear 6 and a shaft-like blade 39 for forming the through hole 7 and the inclined surface, respectively. It becomes. The shaving process is characterized in that the through hole 7 and the inclined surface can be finished with a surface roughness similar to that of the polishing process by the blade 39, and the processing time can be greatly reduced as compared with a general hole polishing process.

  By the way, since the shaft component 5 is processed by the header device, in this embodiment, the material is set to SWCH45K of carbon steel wire for cold heading defined in JIS G3507-2. The SWCH45K has a carbon content set to about 0.45%. On the other hand, the gear part 10 is processed by the pressing device 40, and in this embodiment, the material is set to SWCH12A of cold forging carbon steel wire defined in JIS G3507-2. The SWCH12A has a carbon content set to about 0.12%. The materials of the shaft component 5 and the gear component 10 are not limited to the above-described materials, and may be any material as long as the diffusion bonding is possible.

  The assembly process is divided into a press-fitting operation for press-fitting the shaft component 5 and the gear component 10 by a press-fitting device (not shown) and the diffusion bonding performed after the press-fitting operation. The press-fitting operation is an operation in which the tip of the shaft component 5 is guided to the inclined surface and the gear component 10 is pushed to a predetermined position of the shaft portion 3. Further, since the slope is formed, not only the press-fitting operation can be facilitated, but also the smooth outer periphery of the shaft portion 3 and the peripheral surface of the through hole 7 are not damaged by the press-fitting operation. Therefore, the gap existing at the joint interface between the shaft portion 3 and the through hole 7 can be minimized. Further, the diameter dimensions of the shaft portion 3 and the through hole 7 are set so that the press-fitting allowance is in the range of 0.03 mm to 0.06 mm. This is because when the press-fitting allowance is set to 0.01 mm and 0.02 mm, the gear part 10 slips from the shaft part 5 and slips at a low torque when a torque is applied to the gear part 10 after diffusion bonding described later. Further, when the press-fitting allowance exceeds 0.06 mm, even if the inclined surface is formed, the outer periphery of the shaft portion 3 and the peripheral surface of the through hole 7 are damaged during press-fitting, and the bonding force after diffusion bonding is weak. Similarly, idling occurs at a low torque.

  In the diffusion bonding, the shaft component 5 and the gear component 10 that have finished the press-fitting operation are heated in a vacuum atmosphere by a heat treatment furnace. By this heating, the difference in thermal expansion coefficient described above acts to increase the adhesion area of the bonding interface, and atom diffusion occurs through the adhesion surface, and each bonding proceeds. In this example, in the diffusion bonding, the furnace temperature is set to 860 ° C., and the holding time of this temperature is set to 150 minutes. The furnace temperature and the holding time may be optimally set depending on the materials of the shaft part 5 and the gear part 10 and can be changed as appropriate.

  The heat treatment step is divided into the diffusion bonding and a quenching operation performed after the diffusion bonding. That is, the diffusion bonding overlaps the assembly process and the heat treatment process as shown in FIG. The quenching operation is performed in order to improve the strength of the gear part 10. In this embodiment, the gear part 10 is set to SWCH12A, which is a low-carbon steel, so that it is carburized and quenched. Yes. Note that this quenching operation only needs to improve the strength of the gear component 10, and therefore, for example, tempering quenching may be used if the material of the gear component 10 changes, and the type of quenching is limited to the carburizing quenching. It is not something.

DESCRIPTION OF SYMBOLS 1 Drive hole 2 Head 3 Shaft part 5 Shaft part 6 Gear 7 Through hole 7a R part 7b Chamfering part 10 Gear part 20 Steel material part (this invention)
30 Rolling equipment 31 Flat dies 32 Flat dies 40 Press equipment 100 Steel parts (conventional)
100 ′ Steel part 101 Drive hole 102 Head 103 Shaft part 103 ′ Shaft part 104 Head part 104a Projection part 105 Shaft part 105 ′ Shaft part 106 Gear 107 Through hole 110 Gear part

Claims (4)

A first member formed of a shaft-shaped material having a high carbon content, and a second member made of a material having a low carbon content with a mounting hole to which the first member can be attached;
The first member and the second member are respectively molded by forging, and after the first member and the second member are press-fitted, a joint interface where the first member and the second member are in contact by press-fitting is integrally formed by diffusion bonding. In steel parts with different carbon content,
The carbon content is characterized by being formed by at least one of a burnishing process that finishes the joining interface of the first member by rolling and a shaving process that finishes the joining interface of the second member by punching. Different steel parts.   2. The steel parts having different carbon contents according to claim 1, wherein the first member and the mounting hole are dimensioned within a press-fitting margin of 0.03 mm to 0.06 mm.   The steel part with different carbon content according to claim 1 or 2, wherein a slope is formed at an entrance of the mounting hole. Increasing the carbon content of the first member formed into a shaft shape, and setting the carbon content of the second member having a mounting hole to which the first member can be attached low, the first member and the first member A method of manufacturing steel parts having different carbon contents, in which two members are each formed by forging, the first member and the second member are press-fitted, and then the bonding interface where the first member and the second member are in contact is diffusion-bonded by press-fitting In
The forging step includes at least one of a burnishing process that finishes the joining interface of the first member by rolling and a shaving process that finishes the joining interface of the second member by punching. Manufacturing method for steel parts with different carbon contents.

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