WO2017221963A1

WO2017221963A1 - Method for manufacturing bearing parts

Info

Publication number: WO2017221963A1
Application number: PCT/JP2017/022805
Authority: WO
Inventors: 敬史結城
Original assignee: Ntn株式会社
Priority date: 2016-06-22
Filing date: 2017-06-21
Publication date: 2017-12-28
Also published as: JP2017226873A

Abstract

The present invention provides a method for manufacturing bearing parts, which is able to inductively heat multiple molded bodies in succession and to apply heat uniformly across an entire region to be heated. This method comprises steps for: forming multiple molded bodies (1) each of which have an annular shape and a surface extending in a direction intersecting with the axial direction, and in which one end (2) side in the axial direction is located radially inward with respect to the other end (3) side; and inductively heating the multiple molded bodies (1) by means of induction heating coils (21-23) that are disposed so as to radially face the surface (4) extending in the abovementioned intersecting direction. In the step for inductively heating, the respective multiple molded bodies (1) are disposed such that as the central axes are parallel to the axial direction of the induction heating coils (21-23), and disposed such that the first end (2) sides or the second end (3) sides of two adjacent molded bodies (1) face each other in the axial direction.

Description

Manufacturing method of bearing parts

The present invention relates to a method for manufacturing a bearing component, and more particularly, to a method for manufacturing a bearing component having an outer peripheral surface extending in a direction intersecting the axial direction, with one end in the axial direction having a smaller outer diameter than the other end.

Bearing parts made of bearing steel are subjected to heat treatment that is maintained at a constant temperature for a certain period of time in order to dissolve carbides into the matrix and to diffuse the carbon uniformly. The carbon concentration of the bearing component is required to be within a predetermined range and uniform as a whole. The carbon concentration of the bearing component depends on the penetration rate of carbide into the matrix, and the penetration rate depends on the temperature of the matrix. Therefore, temperature control of the heat treatment is very important in the manufacturing process of the bearing component.

The heat treatment in the manufacturing process of bearing parts may be performed by induction heating due to advantages such as low environmental load and low power consumption. Japanese Patent Laying-Open No. 2015-066788 discloses a heat treatment method in which an axially stacked ring-shaped member is conveyed in the axial direction while being induction-heated by an induction heating coil disposed so as to surround the outer periphery. Yes.

On the other hand, in the case of induction heating, the heat generation density distribution depends on the distance between the induction heating coil and the member to be heated. For this reason, conventionally, the following induction heating method is known for uniformly induction heating the entire outer diameter surface of a heated member having an outer diameter surface inclined with respect to the axial direction. .

Japanese Patent Publication No. 2011-515575 discloses an induction heating method in which the roller is moved at a predetermined interval with respect to the rolling surface of the outer ring of the tapered roller bearing inclined with respect to the axial direction.

Japanese Patent Laid-Open No. 2015-10260 discloses a twisting method in which a plurality of columnar portions extending along the axial direction of the inner ring and the respective columnar portions are connected in the radial direction in order to uniformly heat the surface of the inner ring of the tapered roller bearing. An induction heating method using a surface uniform heating coil having a portion is disclosed.

Japanese Patent Laying-Open No. 2015-066780 Special table 2011-515575 gazette Japanese Patent Laid-Open No. 2015-10260

However, with the induction heating methods described in JP 2011-515575 A and JP 2015-10260 A, it is difficult to continuously heat the member to be heated (molded body) to be a plurality of race rings. is there.

The present invention has been made to solve the above-described problems. A main object of the present invention is to provide a method for manufacturing a bearing component that can continuously induction-heat a plurality of molded bodies and can uniformly heat the entire heating target region.

The bearing component manufacturing method according to the present invention has an annular shape, has a surface extending in a direction intersecting the axial direction, and one end side in the axial direction is positioned more radially inward than the other end side. Forming a plurality of molded bodies, and inductively heating the plurality of molded bodies with at least one induction heating coil arranged to face a surface extending in the intersecting direction. In the step of induction heating, the plurality of molded bodies are arranged so that the central axes thereof are along the axial direction of the induction heating coil, and one end side or the other end side of two adjacent molded bodies are located between each other. It arrange | positions so that it may oppose in an axial direction.

According to the present invention, it is possible to provide a method for manufacturing a bearing component that can continuously induction-heat a plurality of molded bodies and can uniformly heat the entire heating target region.

It is a cross-sectional schematic diagram of the molded object which concerns on this Embodiment. It is a flowchart which shows the manufacturing method of the bearing component which concerns on this Embodiment. It is a side surface schematic diagram which shows the manufacturing method of the bearing component which concerns on this Embodiment. It is a side surface schematic diagram which shows the manufacturing method of the bearing component which concerns on this Embodiment. It is a side surface schematic diagram which shows the manufacturing method of the bearing component which concerns on this Embodiment. It is a cross-sectional schematic diagram which shows the modification of the manufacturing method of the bearing component which concerns on this Embodiment. It is a cross-sectional schematic diagram which shows the other modification of the manufacturing method of the bearing components which concerns on this Embodiment. It is a cross-sectional schematic diagram which shows the further another modification of the manufacturing method of the bearing components which concerns on this Embodiment. It is a figure which shows the model 1 in an Example. It is a figure which shows the model 2 in an Example. It is a figure which shows the model 2 in an Example. It is a graph which shows the electric current input into the

models

1 and 2 in an Example. It is a figure which shows the analysis location of the temperature of the

models

1 and 2 in an Example. It is a graph which shows the analysis result of the model 1 in an Example. It is a graph which shows the analysis result of the model 2 in an Example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

A method for manufacturing a bearing component according to the present embodiment will be described with reference to FIGS. In the present embodiment, as an example of the present invention, a method for manufacturing an inner ring of a tapered roller bearing will be described. As shown in FIG. 2, the inner ring manufacturing method according to the present embodiment mainly includes a step of forming a molded body (S10) and an induction heating step (S20).

In the formed body forming step (S10), a steel material having an arbitrary component composition suitable for induction hardening is prepared. The steel material is, for example, JIS standard SUJ2. Further, for example, SCM445H, SCM440, or the like may be used.

Next, processing such as forging and turning is performed on the prepared steel material. Thereby, a plurality of molded bodies having a shape corresponding to the shape of the desired inner ring are produced. As shown in FIG. 1, the molded body 1 has an annular shape. In the molded body 1, the outer diameter of one end 2 in the axial direction is shorter than the outer diameter of the other end 3. In other words, in the molded body 1, the one end 2 side in the axial direction is located on the inner side in the radial direction than the other end 3 side. One end 2 of the molded body 1 is a portion to be a small collar portion in the inner ring. The other end 3 of the molded body 1 is a portion that should become a large collar portion in the inner ring. A groove is formed between the one end 2 and the other end 3 on the outer peripheral surface of the molded body 1. The groove portion extends in the circumferential direction. The bottom surface of the groove portion is a surface 4 extending in a direction intersecting the axial direction. The surface 4 of the molded body 1 is a portion to be a rolling surface in the inner ring.

Next, as shown in FIG. 2, a quench hardening process is performed. The quench hardening process includes an induction heating process (S20), a heating stop holding process (S30), and a cooling process (S40). The quench hardening process is performed by, for example, a heat treatment apparatus including an induction heating unit illustrated in FIG. 3 and a cooling unit (not illustrated). The induction heating step (S20) is performed by the induction heating unit, and the cooling step (S40) is performed by the cooling unit. First, a heat treatment apparatus used in the quench hardening process will be described.

As shown in FIG. 3, the induction heating unit includes, for example, a plurality of

induction heating coils

21, 22, and 23. The induction heating coils 21 to 23 have an annular shape. The induction heating coils 21 to 23 have an inner diameter larger than the outer diameter of the other end 3 of the molded body 1. The inner diameters of the induction heating coils 21 to 23 are the same, for example. The induction heating coils 21 to 23 are arranged coaxially so that the central axes overlap when viewed from the respective axial directions. The induction heating coils 21 to 23 are arranged at an interval in the axial direction. The axial direction of the induction heating coils 21 to 23 is, for example, along the vertical direction. The axial direction D1 of the induction heating coils 21 to 23 is along the conveying direction of the molded body 1 conveyed in a space surrounded by induction heating coils 21 to 23 described later.

The number of turns of the induction heating coils 21 to 23 differs, for example, between some induction heating coils 21 and 22 and other induction heating coils 23. The number of turns of some induction heating coils 21, 22, 23, and 26 is, for example, half the number of turns of the other induction heating coils 24 and 25. The distance between the two induction heating coils adjacent in the axial direction of the induction heating coils 21 to 23 is, for example, the length in the axial direction of the molded body 1 (the length in the axial direction between the one end 2 and the other end 3). ) About twice as much. In the induction heating unit, the configurations of the induction heating coils 21 to 23 are appropriately changed according to the shape of the molded body 1 and the like. The optimum configuration of the induction heating coils 21 to 23 can be determined by preliminary experiments or simulations.

The induction heating unit further includes, for example, a power supply device 30 that supplies power to the induction heating coils 21 to 23 individually. The power supply device 30 is electrically connected to the induction heating coils 21 to 23 in series. In the power supply device 30, for example, any of a power value, a current value, and a voltage value supplied to the induction heating coils 21 to 23 is controlled by a control device (not shown). A high-frequency current flows through the induction heating coils 21 to 23 by the power supplied from the power supply device 30. The high frequency current flowing through the induction heating coils 21 to 23 is controlled to be constant in the induction heating step (S20) by the power supply device 30, for example. Note that the high-frequency currents flowing through the induction heating coils 21 to 23 may be controlled by the power values supplied by different power supply devices.

The induction heating unit includes, for example, a carry-in unit 40 for carrying the molded bodies 1 one by one into a space adjacent to the space surrounded by the induction heating coils 21 to 23 in the axial direction D1 of the induction heating coils 21 to 23, and the carry-in unit 40. Further includes a support portion 41 that supports the plurality of molded bodies 1 carried into the adjacent space. The support part 41 is a plurality of nail jigs formed at intervals in the circumferential direction of the molded body 1, for example. The support portion 41 has one end 2 of the molded body 1 that is located farthest from the induction heating coil 21 among the plurality of molded bodies 1 that are carried into the space surrounded by the induction heating coils 21 to 23 and the adjacent space. Alternatively, it is provided so as to be able to contact a plurality of locations on the other end 3. The carry-in unit 40 can convey the molded body 1 to the induction heating coils 21 to 23 side in the axial direction D1 relative to the support unit 41. Specifically, the carry-in unit 40 is directly connected to the support unit 41 among the plurality of molded products 1 in which the other end 3 or one end 2 of the molded product 1 being conveyed by the carry-in unit 40 is supported by the support unit 41. While contacting the one end 2 or the other end 3 of the molded body 1 that is in contact, the one end 2 or the other end 3 of the molded body 1 being conveyed by the carry-in portion 40 reaches a position where it can be supported by the support portion 41. So that it is driven. That is, the some molded object 1 currently supported by the support part 41 is conveyed along the axial direction D1 with the molded object 1 which the carrying-in part 40 is conveying. In the support portion 41, the plurality of molded bodies 1 are arranged so that the center axes thereof are along the axial direction of the induction heating coils 21 to 23, and one end 2 of the two molded bodies 1 adjacent to each other in the axial direction and the other. It can be supported in a state where the ends 3 are stacked so as to face each other. The direction in which the plurality of molded bodies 1 supported by the support section 41 are pushed out by the carry-in section 40 is the axial direction of the induction heating coils 21 to 23 and the axial direction of the plurality of molded bodies 1 held on the support section 41. It is along. The direction D1 is, for example, a direction from below to above along the vertical direction. The support part 41 can be stopped relative to the induction heating coils 21 to 23 while holding the plurality of molded bodies 1. A time interval from the time when the molded body 1 whose one end 2 is in contact with the carry-in part 40 is conveyed to the time when the molded body 1 whose other end 3 is in contact with the carry-in part 40 is conveyed (the changing process described later ( The time required for the conveying step S21) is from when the molded body 1 whose other end 3 is in contact with the carry-in part 40 is conveyed until when the molded body 1 whose one end 2 is in contact with the carry-in part 40 is conveyed. Shorter than the time interval (the time required for the holding step (S22) described later).

The cooling unit includes, for example, a cooling liquid tank in which a cooling liquid (for example, quenching oil) held at an appropriate temperature is stored. The molded body 1 processed in the induction heating unit is individually and sequentially conveyed from the induction heating unit to the cooling unit, for example, by a conveyance unit provided in the heat treatment apparatus.

The carry-in section 40 may be configured to carry two molded bodies 1 laminated so that one end 2 faces each other into a space adjacent to the space surrounded by the induction heating coils 21 to 23. Good. The support part 41 should just be provided in contact with several places of the other end 3 of the molded object 1 in the position most distant from the induction heating coil 21 among the two molded objects 1 carried in as one set. . The transport unit may be configured to transport two molded bodies 1 laminated so that one end 2 faces each other as a set from the induction heating unit to the cooling unit. That is, the method for manufacturing a bearing component according to the present embodiment may be configured so that two molded bodies to be the bearing components can be processed as one workpiece having a drum shape.

In the induction heating step (S20), the plurality of molded bodies 1 are continuously subjected to induction heating treatment. The induction heating step (S20) includes a step of changing the relative positions of the plurality of molded bodies 1 and the induction heating coils 21 to 23 in the axial direction of the induction heating coils 21 to 23 (conveying step S21), an induction heating. A step of holding the relative positions of the plurality of molded bodies 1 and the induction heating coils 21 to 23 in the axial direction of the coils 21 to 23 for a predetermined time (S22).

First, a plurality of molded bodies 1 are held on the support portion 41. The plurality of molded bodies 1 have their respective central axes along the axial direction of the induction heating coils 21 to 23, and one end 2 and the other end 3 of the two molded bodies 1 adjacent to each other in the direction D1 face each other. It is held in a stacked state. For example, twelve molded bodies 1 are held on the support portion 41. On the support portion 41, the twelve molded bodies 1 are arranged such that their respective central axes are continuous along the direction D1, and one end 2 of the two molded bodies 1 adjacent to each other in the direction D1 and the other It arrange | positions so that the ends 3 may oppose. For convenience of explanation, the two molded bodies 1 laminated so that one ends 2 thereof are opposed to each other are referred to as a set of laminated bodies. The twelve molded bodies 1 are composed of six sets of

laminated bodies

11, 12, and 13. The six sets of stacked bodies 11 to 13 are stacked in order from the top in the vertical direction to the bottom so that the other ends 3 face each other.

Next, a changing step (S21) is performed. In this step (S <b> 21), the plurality of molded bodies 1 held by the support portion 41 are pushed up by the molded body 1 carried in by the carry-in section 40, and the molded bodies 1 carried in by the carry-in section 40 are By being supported by the support part 41, it is sequentially conveyed along the direction D1. Specifically, the molded body 1 conveyed by the carry-in portion 40 to one end 2 or the other end 3 of the molded body 1 positioned at the lowermost position among the plurality of molded bodies 1 held by the support portion 41. One end 2 or the other end 3 abuts from below. The carry-in part 40 moves upward until the one end 2 or the other end 3 located below the molded body 1 being conveyed reaches a position where the support part 41 can support it. At this time, the carrying-in part 40 supports the some molded object 1 previously supported by the support part 41, and the molded object 1 currently conveyed, and conveys it in the direction D1.

Thereby, the relative positions of the plurality of molded bodies 1 and the induction heating coils 21 to 23 in the axial direction D1 are changed. The plurality of molded bodies 1 are sequentially conveyed into a space surrounded by the induction heating coils 21 to 23. Of the plurality of molded bodies 1, the uppermost molded body 1 is discharged from the space surrounded by the induction heating coils 21 to 23.

As shown in FIG. 3, in this step (S21), when viewed from the radial direction, the other ends 3 of the two adjacent molded bodies 1 in the axial direction do not overlap with the induction heating coils 21 to 23. Until the state (hereinafter referred to as the first state) is reached. In this step (S21), when viewed from the radial direction in a relatively short time, the other ends 3 of the two adjacent molded bodies 1 in the axial direction and the induction heating coils 21 to 23 overlap each other. Are placed in a state (hereinafter referred to as a second state). The time t2 when the molded body 1 is placed in the second state is preferably less than 10 seconds.

Next, the holding step (S22) is performed. This step (S22) is performed immediately after reaching the first state. In this step (S22), the plurality of molded bodies 1 are supported by the support portion 41. As shown in FIG. 3, in the first state, when viewed from the radial direction, the one end 2 of the molded body 1 and a part of the surface 4 constituting the laminate 11 are guided by the changing step (S21). It arrange | positions in the position which overlaps with the heating coil 21. FIG. Preferably, when viewed from the radial direction, the boundary between two adjacent one ends 2 in the direction D1 and the center of the induction heating coils 21 to 23 in the axial direction overlap each other.

The holding step (S22) is performed for a predetermined time. That is, the first state is maintained for a predetermined time. The time t1 in which the first state is maintained is sufficiently longer than the time t2 in which the first state is kept in the second state in the changing step (S22). For example, the time t1 is twice or more the time t2. The time t1 and the time t2 vary depending on the size of the molded body 1 and the like. For example, when the outer shape of the molded body 1 is 140 mm, the inner diameter is 110 mm, and the width is 40 mm, the time t1 is 8 seconds to 30 seconds. The time t2 is not less than 4 seconds and not more than 15 seconds.

The step of changing (S21) and the step of holding (S22) are repeatedly performed. In other words, each molded body 1 is held in the first state by the number of induction heating coils 21 to 23 in the induction heating step (S20). Specifically, the stacked bodies 11 to 13 resume moving in the direction D1 after the processing time (time t1) in the holding step (S22) has elapsed. As shown in FIG. 4, the laminated bodies 11 to 13 are used until the molded body 1 constituting the laminated body 11 is again put in the first state, that is, the one end 2 and the surface of the molded body 1 constituting the laminated body 11. It moves until a part of 4 is arrange | positioned in the position which opposes the induction heating coil 22 in radial direction. When the molded body 1 constituting the laminated body 11 is placed in the first state, the step of holding again (S22) is performed. At this time, the molded body 1 constituting the laminated body 12 is also placed in the first state. That is, the one end 2 and a part of the surface 4 of the molded body 1 constituting the laminated body 12 are arranged at positions facing the induction heating coil 21 in the radial direction. The laminated bodies 11 to 13 resume moving in the direction D1 after a predetermined time has passed since they stopped. In addition, although the processing time of the process to hold | maintain several times (S22) can each be set arbitrarily, for example, all are fixed time t1.

After the induction heating step (S20) is started, the step of changing (S21) and the step of holding (S22) are performed by the number of the laminates 11 to 13, thereby forming the laminate 11 as shown in FIG. One end 2 of the molded body 1 and a part of the surface 4 are arranged at a position facing the induction heating coil 23 in the radial direction. At the same time, the one end 2 and a part of the surface 4 of the molded body 1 constituting the laminated body 13 are arranged at positions facing the induction heating coil 21 in the radial direction.

The stacked bodies 11 to 13 are moved again in the direction D1 after a predetermined time has elapsed after the movement in the direction D1 is stopped. The formed body 1 constituting the laminate 11 is conveyed above the induction heating coil 23. Thereby, the induction heating process (S20) with respect to the molded object 1 which comprises the laminated body 11 is complete | finished. Furthermore, the process of changing (S21) and the process of holding (S22) are repeated, whereby the induction heating process (20) for the plurality of molded bodies 1 is sequentially completed. In other words, in the induction heating step (20), the induction heating process for the plurality of molded bodies 1 is continuously performed.

In the induction heating step (S20), for example, the plurality of molded bodies 1 are heated while being sequentially conveyed to positions opposed to the respective radial directions of the induction heating coils 21 to 23, and are molded at predetermined positions in the direction D1. The surface layer region including at least the surface 4 of the body is induction-heated to a temperature of A ₁ point or higher. Thereby, an annular heating region along the surface 4 is formed in each molded body 1. In addition, the heat processing conditions in an induction heating process (S20) can be suitably set according to the characteristic requested | required as a dimension of a molded object 1, a bearing ring, etc. In the induction heating step (S20), the high frequency current supplied to the induction heating coils 21 to 23 is controlled to be constant, for example.

The molded body 1 that has undergone the induction heating step (S20) is subjected to a heating stop holding step (S30). In other words, the heating stop and holding step (S30) is sequentially performed on each of the molded bodies 1 constituting the laminated bodies 11 to 13. The molded body 1 is held for a predetermined time in a state where heating is stopped in the step (S30). The step (S30) is performed after the induction heating is completed and before the cooling to a temperature equal to or lower than the _MS point in order to suppress temperature variation. More specifically, under the shape of the molded body 1 and the heating conditions, for example, by maintaining the state in which the heating is stopped for 3 seconds after the heating is completed, the temperature variation on the surface of the heated region is 20 ° C. It can be suppressed to the following extent. This step (S30) can be performed while the stacked bodies 11 to 13 are moving in the direction D1 or stopped. In other words, the specific molded body 1 can be performed simultaneously with the induction heating step (S20) of the other molded body 1 positioned below the molded body 1. The heating stop holding step (S30) for the plurality of molded bodies 1 is sequentially completed.

A cooling process (S40) is implemented to the molded object 1 which the heating stop holding process (S30) was complete | finished. That is, the cooling step (S40) is sequentially performed on the molded bodies 1 constituting the stacked bodies 11 to 13. In the step (S40), the entire heating area of the molded body 1 is simultaneously cooled to a temperature equal to or lower than the _MS point. The formed body 1 is sequentially transported from above the laminates 11 to 13 to the cooling section by the transport section, and immersed in the cooling liquid tank of the cooling section for a predetermined time, so that the entire heating region is brought to a temperature below the _MS point. Cooled at the same time. As a result, the heating region is transformed into martensite, and the region including the surface 4 is hardened and hardened. The quench hardening process is completed by the above procedure. The quench hardening process for the plurality of molded bodies 1 is continuously performed.

Next, a tempering step (S50) is performed. In this step (S50), the quenched and hardened molded body 1 is placed in, for example, a furnace, heated to a temperature of A ₁ point or less, and held for a predetermined time, whereby a tempering process is performed. The

Next, a finishing process (S60) is performed. In this step (S60), for example, a finishing process such as a polishing process on the surface 4 is performed. By the above process, the inner ring member constituting the inner ring of the tapered roller bearing is completed. The surface 4 is finished as a rolling surface. In the inner ring member manufactured in this way, the hardened and hardened layer is uniformly formed over the entire circumference along at least the rolling surface.

Next, the function and effect of the bearing component manufacturing method according to the present embodiment will be described. The bearing component manufacturing method according to the present embodiment has an annular shape, has a surface extending in a direction intersecting the axial direction, and one end 2 side in the axial direction is more radial than the other end 3 side. The plurality of molded bodies 1 are formed by the step (S10) of forming a plurality of molded bodies 1 positioned inside the surface and the induction heating coils 21 to 23 arranged to face the surface 4 extending in the intersecting direction in the radial direction. (S20). In the induction heating step (S20), the plurality of molded bodies 1 are arranged so that the central axes thereof are along the axial direction of the induction heating coils 21 to 23, and one end of two adjacent molded bodies 1 are arranged. The two sides or the other end 3 side are arranged so as to face each other in the axial direction.

If it does in this way, in the induction heating process (S20), each forming object 1 may be put in the 1st state sequentially or simultaneously. In the first state, the magnetic flux generated by the induction heating coils 21 to 23 is formed along the outer peripheral surface of the molded body 1. Therefore, at least the surface layer region of the molded body 1 including the surface 4 to be a rolling surface is induction-heated to a temperature of A ₁ point or higher by the eddy current induced by the magnetic flux when the molded body 1 is in the first state. As a result, a hardened and hardened layer is uniformly formed on the molded body 1 along at least the surface 4. That is, according to the method for manufacturing a bearing component according to the present embodiment, a plurality of molded bodies 1 can be continuously subjected to induction heating treatment, and the entire heating target region of each molded body 1 is uniformly heated. be able to.

In the bearing component manufacturing method, the induction heating step (S20) is a step of changing the relative positions of the plurality of molded bodies 1 and the induction heating coils 21 to 23 in the axial direction of the induction heating coils 21 to 23 ( S21) and a step (S22) of maintaining the relative positions of the plurality of molded bodies 1 and the induction heating coils 21 to 23 in the axial direction of the induction heating coils 21 to 23. Therefore, the first state is realized by the changing step (S21) and can be held by the holding step (S22).

In the bearing component manufacturing method, in the induction heating step (S20), the plurality of molded bodies 1 are induction heated by the plurality of induction heating coils 21 to 23. The plurality of induction heating coils 21 to 23 are arranged at intervals from each other along the axial direction of the induction heating coils 21 to 23. The step of changing (S21) and the step of holding (S22) are repeatedly performed alternately. In this way, the plurality of laminates 11 to 13 can be subjected to induction heating treatment simultaneously.

In the second state, the magnetic flux generated by the induction heating coils 21 to 23 is formed so as to intersect the outer peripheral surface of the molded body 1. Therefore, when the molded body 1 is in the second state, the surface layer region of the molded body 1 including the surface 4 to be the rolling surface is induced and heated by the eddy current induced by the magnetic flux to a temperature of A ₁ point or higher. As a result, a non-homogeneous hardened layer is formed on the molded body 1. If the time t2 during which the molded body 1 is placed in the second state is less than 10 seconds, the surface layer of the molded body 1 including the surface 4 to be a rolling surface by eddy current induced by the magnetic flux when in the second state. It is possible to prevent the region from being heated by induction to a temperature of A ₁ point or higher.

Note that any number of the molded bodies 1 may be stacked. As shown in FIG. 6, the dummy members 50 are preferably stacked above the stacked body 11. That is, it is preferable that a dummy member 50 to be transported before the laminated body 11 is prepared in a space surrounded by the induction heating coils 21 to 23. The dummy member 50 has a configuration equivalent to that of the molded body 1. In the dummy member 50, the one end 52 side in the axial direction is positioned more radially inward than the other end 53 side. For example, a plurality of dummy members 50 are stacked in the axial direction. The dummy members 50 are stacked such that one ends 52 and the other ends 53 face each other in the axial direction. The dummy member 50 is preferably provided such that the length in the axial direction is longer than the distance between the centers of the induction heating coil 21 and the induction heating coil 23 in the axial direction. The magnetic field distribution in the space surrounded by the induction heating coils 21 to 23 changes depending on the presence / absence and arrangement of the object to be heated in the space. Therefore, by arranging a dummy member 50 having a configuration equivalent to that of the molded body 1 in the space prior to the heat treatment of the molded body 1, the magnetic field distribution in the space before and after the heat treatment for the molded body 1 is started. Can be prevented from changing.

Further, in the example shown in FIG. 3, the molded bodies 1 constituting the laminates 11 to 13 are arranged at positions where a part of one end 2 and a part of the surface 4 face the induction heating coil 23 in the radial direction. However, it is not limited to this. Each molded body 1 constituting the laminated bodies 11 to 13 may be disposed at a position where the entire one end 2 and a part of the surface 4 face the induction heating coil 23 in the radial direction. Each of the molded bodies 1 constituting the laminates 11 to 13 may be disposed at a position where the boundary between one end 2 adjacent in the axial direction and the center of the induction heating coils 21 to 23 in the axial direction overlap in the radial direction. Good.

Also, as shown in FIG. 3, it is preferable that one end 2 and the other end 3 of the plurality of molded bodies 1 are directly connected in the axial direction. However, as shown in FIG. One end 2 of body 1 may be indirectly connected in the axial direction. One ends 2 may be connected to each other through a conductive member 60 made of, for example, a conductive material. Similarly, the some molded object 1 may be laminated | stacked so that the other ends 3 may contact indirectly in an axial direction. Even in this case, in the first state, the magnetic flux generated by the induction heating coils 21 to 23 is formed along the outer peripheral surface of the molded body 1, so that the same method as the method for manufacturing the bearing component according to the present embodiment is used. There is an effect.

In the above bearing component manufacturing method, the molded body 1 has a surface 4 formed on the outer peripheral surface extending in a direction intersecting the axial direction. That is, in this Embodiment, the molded object 1 is shape | molded as what should become an inner ring | wheel of a tapered roller bearing. In addition, the manufacturing method of the bearing component which concerns on this Embodiment is suitable for the manufacturing method of the bearing component in which the quench hardening layer is formed on the surface area | region inclined with respect to the axial direction. Therefore, as FIG. 8 shows, the molded object 1 may be shape | molded as what should become an outer ring | wheel of a tapered roller bearing, for example. In this case, a surface to be a rolling surface (a surface extending in a direction intersecting the axial direction) in the molded body 1 is formed on the inner peripheral surface. Therefore, the outer diameter of the induction heating coils 21 to 23 used in the induction heating step (S20) is shorter than, for example, the inner diameter of the molded body 1, and the induction heating coils 21 to 23 are, for example, the inner peripheral surface of the molded body 1 in the radial direction. It is arranged inside. As for the molded object which should become an outer ring | wheel, the one end side in an axial direction is located in the outer side of radial direction rather than the other end side. For this reason, the plurality of molded bodies are arranged such that their central axes are along the axial direction of the induction heating coil, and one end side and the other end side of two adjacent molded bodies are opposed in the axial direction. It suffices if they are arranged so as to.

Moreover, in the manufacturing method of the said bearing components, the normalization process may be implemented before a quench hardening process. The normalizing step, after the fabricated molded body is heated to a temperature not lower than the A ₁ transformation point in the step (S10), normalizing processing is performed by being cooled to a temperature lower than the A ₁ transformation point The At this time, the cooling rate at the time of cooling in the normalizing process may be a cooling rate at which the steel constituting the formed body is not transformed into martensite, that is, a cooling rate lower than the critical cooling rate. The hardness of the molded body after the normalizing treatment is high when the cooling rate is large, and is low when the cooling rate is small. Therefore, desired hardness can be imparted to the molded body by adjusting the cooling rate. The heat treatment in the normalizing process is performed by furnace heating, for example.

Next, examples will be described. In this embodiment, the following

models

1 and 2 are set up for induction heat treatment, and the temperature distribution and the temperature rise behavior in the heated region of the molded body that is the heat-treated object in each

model

1 and 2 are simulated It was evaluated by. The simulation was performed using coupled analysis of electromagnetic field frequency response analysis and heat conduction analysis by the finite element method.

(Model 1)
Model 1 is a model according to the induction heating process of the bearing component manufacturing method according to the present invention. FIG. 9 is a schematic cross-sectional view for explaining the model 1.

The molded body 1 was an inner ring of a tapered roller bearing (model number 32022). The heated area for induction heating was a surface layer area facing the outer peripheral surface of the molded body 1. As shown in FIG. 9, in the model 1, twelve molded bodies 1 are arranged so that the central axes thereof are continuous, and each of the small ribs (one end side) of two adjacent molded bodies 1. They were stacked so that each other and the large brim (the other end side) face each other in the axial direction. The induction heating coils 21 to 26 were each single-turn coils (inner diameter 200 mm, sectional shape 12 mm × 12 mm). In the model 1, the six induction heating coils 21 to 26 are arranged at intervals in the axial direction. The number of turns of the induction heating coils 21, 22, 24, and 25 was half the number of turns of the induction heating coils 23 and 26. The distance between the centers of the two induction heating coils adjacent in the axial direction in the axial direction was twice the length of the molded body 1 in the axial direction. The central axis of the laminate of the molded body 1 and the central axes of the induction heating coils 21 to 26 were arranged coaxially so as to overlap. The molded body 1 and the induction heating coils 21 to 26 are arranged so that the axial directions thereof are along the vertical direction.

The molded body 1 was moved relative to the induction heating coils 21 to 26 from the lower side in the vertical direction to the upper side. The molded body 1 before the heat treatment was at room temperature. The molded body 1 was to repeat the changing step (S21) and the holding step (S22). In the holding step (S22), when viewed from the radial direction, the time during which the one end 2 of the molded body 1 and the extending surface in the direction intersecting the axial direction are held at a position overlapping the induction heating coils 21 to 26 is as follows: 24 seconds.

The current values input to the induction heating coils 21 to 26 are the same. The frequency of the high-frequency current input to the induction heating coils 21 to 26 was 3 kHz. Each current value input to the induction heating coils 21 to 26 was set to be constant at 2085 Arms.

As the coupled analysis conditions, the measured values of SUJ2 were used for the magnetization curve (BH curve), electrical conductivity, specific heat, and thermal conductivity.

In the coupled analysis of model 1, after the start of the heat treatment (time zero in FIG. 12), the induction heating coil 21 located at the lowest position among the six induction heating coils shown in FIG. Of the two molded bodies 1 of the laminated body 11 to be arranged, the temperature rise behavior was analyzed at four locations in the surface region of the molded body 1 positioned below. FIG. 13 is a schematic cross-sectional view showing the four places in the molded body. As shown in FIG. 13, the analysis location A is a point on the large brim (the other end 3) of the molded body 1. Analysis points B and C are points on the rolling surface (surface 4) of the molded body 1. The analysis location D is a point on the small brim (one end 2) of the molded body 1. The heat treatment was performed for 280 seconds.

(Model 2)
Model 2 is a model obtained by changing the stacking method of the compacts to be heated as compared with model 1. The model 2 stacking method is employed in the induction heating method of the conventional manufacturing method of bearing parts. Model 2 is a model of an induction heating method that is considered optimal by simulation when the conventional stacking method is employed. FIG. 10 is a schematic cross-sectional view for explaining the model 2. FIG. 11 is an analysis model of model 2. As shown in FIG. 12, the current passed through the induction heating coil was changed with time after the heat treatment for the molded body 1 was started. In this simulation, instead of changing the relative positional relationship of the plurality of molded bodies 1 with respect to the induction heating coil as in the step (S21) of changing in the bearing component manufacturing method of the embodiment described above, the induction heating coil The current value supplied to was changed over time. The horizontal axis of FIG. 12 indicates zero time when the supply of current to each induction heating coil is started, and shows the elapsed time (unit: second) from that time. The vertical axis | shaft of FIG. 12 shows the electric current value (unit: Arms) input into an induction heating coil.

The molded body was an inner ring of a tapered roller bearing (model number 32022) in the same manner as model 1. Referring to FIG. 11, model 2 simulates a state in which molded body 1 and induction heating coil are arranged infinitely in the vertical direction by setting periodic boundary conditions at the upper and lower ends of the model. The induction heating coil had an inner diameter of 200 mm and a cross-sectional shape of 12 mm × 12 mm.

The configuration of the induction heating coil and the heat treatment conditions in the model 2 were based on the configuration considered to be optimal when induction heating is continuously performed on the molded bodies stacked as described above.

In the coupled analysis of model 2, after the heat treatment is started (time zero in FIG. 12), the molding is arranged at a position overlapping with the induction heating coil located at the lowest position among the 13 induction heating coils shown in FIG. The temperature rise behavior was analyzed at four points in the surface area of the body. The four places were designated as A to D shown in FIG. The heat treatment was performed for 280 seconds.

14 and 15 are graphs showing the analysis results of model 1 and model 2, respectively. 14 and 15, as in the horizontal axis of FIG. 12, when viewed from the radial direction, the portion other than the large brim of the molded body is positioned at the lowest position shown in FIGS. 9 and 10. The time when it is placed at the position where it overlaps the coil is set to zero, and the elapsed time from that time (unit: seconds) is shown. The vertical axes in FIGS. 14 and 15 indicate temperatures (unit: ° C.) at four analysis points A to D, respectively.

Table 1 shows the temperature reached at four locations 280 seconds after the start of heating, the difference between the maximum temperature and the minimum temperature (maximum value of temperature variation), and until all four locations reached 900 ° C. Indicates the time required.

As shown in FIG. 14 and Table 1, in model 1, all four locations reached 900 degrees after 126 seconds. Furthermore, in model 1, after reaching 900 ° C., the temperature variation between the four locations was small, and the temperature variation was small at all four locations.

On the other hand, as shown in FIG. 15 and Table 1, model 2 had 272 seconds to reach 900 degrees at all four locations. In model 2, the temperature variation at four locations was particularly large at a temperature of 700 ° C. or higher.

According to this example, model 1 has a shorter time to reach 900 ° C. and a smaller temperature distribution in the heated region of the molded body than model 2 which is considered to be the optimum condition in the conventional induction heating method. It was confirmed. That is, according to the method for manufacturing a bearing component according to the present invention, as compared with the conventional method for manufacturing a bearing component in which a plurality of molded bodies are induction-heated in a state of being stacked in the same direction as shown in FIG. It was confirmed that the entire heating target region can be heated uniformly.

It should be considered that the embodiments and examples disclosed this time are examples in all respects and are not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 molded body, 2 one end (small brim), 3 other end (large brim), 4 surfaces (rolling surface), 11, 12, 13 laminate, 21, 22, 23, 24, 25, 26 induction heating coil 31, 32, 33 Power supply device, 40 support part, 50 dummy member, 60 conductive member.

Claims

A plurality of molded bodies having an annular shape, having a surface extending in a direction intersecting with the axial direction, and having one end side in the axial direction positioned more radially inward than the other end side are formed. Process,
A step of inductively heating the plurality of molded bodies by at least one induction heating coil disposed opposite to the surface extending in the intersecting direction,
In the induction heating step, the plurality of molded bodies are arranged such that respective central axes are along the axial direction of the induction heating coil, and the one end sides of the two adjacent molded bodies or A method for manufacturing a bearing component, wherein the other end sides are arranged so as to face each other in the axial direction.
The induction heating step includes a step of changing a relative position of the plurality of molded bodies in the axial direction of the induction heating coil and the induction heating coil, and the plurality of the axial heating coils in the axial direction. The manufacturing method of the bearing component of Claim 1 including the process of hold | maintaining the relative position of a molded object and the said induction heating coil.
In the holding step, a state in which the other end of each of the two molded bodies adjacent in the axial direction and the induction heating coil do not overlap when viewed from the radial direction is maintained. The method for manufacturing a bearing component according to claim 2.
In the induction heating step, the plurality of molded bodies are induction heated by the plurality of induction heating coils,
The plurality of induction heating coils are spaced apart from each other along the axial direction of the induction heating coil,
The method of manufacturing a bearing component according to claim 2, wherein the changing step and the holding step are repeatedly performed alternately.
5. The method for manufacturing a bearing part according to claim 1, wherein the molded body has a surface extending in the intersecting direction formed on an outer peripheral surface.