JP2013146769A - Method for manufacturing shaft member of wheel rolling bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a shaft member of a wheel rolling bearing device, which can efficiently manufacture the shaft member of the wheel rolling bearing device with a simpler die by appropriately securing a desired dimensional accuracy and surface roughness.SOLUTION: In a method for manufacturing a shaft member of a wheel rolling bearing device, a cylindrical fitting shaft part having a recess opening in an axial direction, a flange part having a disk shape or a radial shape orthogonal to the axial direction, and a shaft part having a columnar shape in which an inner ring raceway surface is formed on an outer peripheral surface thereof are coaxially arranged along the axial direction. The method includes: a heating step (B) of heating steel to a hot rolling temperature of a transformation point temperature or above; hot-forging steps (C)-(E) of molding the steel of the hot rolling temperature into a forging intermediate molded product 7E; and a cold forging step (J) of molding the forging intermediate molded product into a forging final molded product 7J by cold forging.

Description

  The present invention relates to a method for manufacturing a shaft member of a wheel rolling bearing device.

For example, Patent Document 1 and Patent Document 2 disclose a method of manufacturing a wheel rolling bearing device (a so-called wheel hub unit).
In the method of manufacturing a wheel-supporting rolling bearing unit disclosed in Patent Document 1, the shaft member of the wheel-rolling bearing device is formed in stages into a final forged product by sequentially performing hot forging in a plurality of steps. Then, after further cooling, cold working is performed. The position where the cold working is performed is a caulking portion for caulking the inner ring to the shaft member of the wheel rolling bearing device, and the cold working is caulking.
Moreover, in the manufacturing method of the bearing ring member which comprises the wheel bearing rolling bearing unit disclosed by patent document 2, the shaft member of the wheel rolling bearing apparatus is shape | molded in steps by cold forging of multiple processes. Yes. As a cold forging die, a special die provided with a floating die is used.

JP 2009-226460 A JP 2007-152413 A

In the prior art described in Patent Document 1, the forged final molded product of the shaft member of the wheel rolling bearing device is molded by hot forging, and has a dimensional accuracy higher than that formed by cold forging. Inferior in terms of surface roughness. The reason why the dimensional accuracy is inferior is that in hot forging, heat gathers in a thick part during cooling and deflection is likely to occur. The reason why the surface roughness is inferior is that when the material is heated to a temperature equal to or higher than the transformation point, oxide scale is generated on the surface.
The transformation point temperature described in this specification refers to a so-called AC1 transformation temperature, and refers to a temperature at which austenite starts to be generated during heating. Austenite is a phase that precipitates at a relatively high temperature in a solid solution of iron and carbon, and refers to so-called γ iron.
Moreover, in the prior art described in Patent Document 2, the forged final molded product of the shaft member of the wheel rolling bearing device is formed by cold forging, and the dimensional accuracy is higher than the case of forming by hot forging. , Superior in terms of surface roughness. However, since cold forging is less susceptible to plastic deformation than hot forging, there are many steps to be molded step by step, and complex molds having floating dies are also used for the molds.
The present invention was devised in view of such points, and the shaft member of the wheel rolling bearing device is appropriately secured with a simpler mold so as to ensure the desired dimensional accuracy and surface roughness. It aims at providing the manufacturing method of the shaft member of the rolling bearing apparatus for wheels which can be manufactured efficiently.

In order to solve the above-described problems, the method for manufacturing the shaft member of the rolling bearing device for wheels according to the present invention takes the following means.
In the present invention, a fitting shaft portion having a cylindrical shape with a recess opening in the axial direction, a flange portion having a disk shape or radial shape orthogonal to the axial direction, and an inner ring raceway surface are formed on the outer peripheral surface. It is a manufacturing method of the shaft member of the rolling bearing device for wheels by which the shaft part which has a column shape is arranged on the same axis along the axial direction.
And the manufacturing method of the shaft member of the rolling bearing device for wheels includes a heating step of heating a steel material so as to have a hot temperature that is equal to or higher than a transformation point temperature of the steel material, and the steel material having the hot temperature, A hot forging step in which a forging intermediate molded product having an intermediate shape between the shape of the steel material and the forged final molded product which is the final shape in forging is formed using a mold for intermediate molded products, and the final Cold forging process in which the shape of the fitting shaft portion, the flange portion, and the shaft portion is formed into the shape of the forged final molded product by cold forging the forged intermediate molded product using a mold for a molded product And having.

According to the present invention, the shaft member of the rolling bearing device for a wheel is not formed by only hot forging or only cold forging, but is first forged from a steel material (material) using hot forging that is relatively easy to plastically deform. Mold into an intermediate molded product. Then, plastic deformation from the forged intermediate molded product to the final forged product is performed using cold forging.
Thus, since the forging final molded product is formed by cold forging, dimensional accuracy and surface roughness can be appropriately ensured. Further, the forging intermediate molded product is formed by performing hot forging before cold forging, and the amount of plastic deformation caused by cold forging is less than that of the invention described in Patent Document 2, so simpler gold Cold forging can be performed efficiently with a die.

It is an axial sectional view showing the state where shaft member 1 of the rolling bearing device for wheels manufactured with the manufacturing method of the rolling bearing device for wheels of the present invention was assembled as rolling bearing device A for wheels. It is the figure which looked at the shaft member 1 of the rolling bearing device for wheels shown in Drawing 1 from the B direction, and (A) explains the example of flange part 21 in which a plurality of flange parts 21 have extended radially in the direction of an outer diameter. (B) is a figure explaining the example of the flange part 21 extended in the disk shape in the outer-diameter direction. It is an axial sectional view of the shaft member 1 of the rolling bearing device for wheels. It is a figure which shows the change of the shape of the raw material by process (A)-(N) until it forms the shaft member of the rolling bearing apparatus for wheels from the shaft-shaped raw material 7A. It is a figure which shows the external appearance of the post-coating forging intermediate molded product 7I (after the surface treatment process of FIG. 4 (I)) before being molded by cold forging.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated using drawing.
● [Whole rolling bearing device structure (FIG. 1) and wheel rolling bearing device shaft member 1 structure (FIGS. 2 and 3)]
Next, the whole structure of the wheel rolling bearing device A and the shaft member 1 of the wheel rolling bearing device (hereinafter referred to as “the shaft member 1 of the wheel rolling bearing device” will be referred to as the “shaft member 1” with reference to FIGS. Will be described. FIG. 1: has shown the axial sectional drawing which shows the state with which the shaft member 1 manufactured with the manufacturing method of the shaft member 1 of the rolling bearing device for wheels of this invention was assembled | attached as the rolling bearing device A for wheels. 2 is a view of the shaft member 1 shown in FIG. 1 as viewed from the B direction, and FIG. 3 is a view for explaining the shaft member 1 in detail by extracting the shaft member 1 from FIG.
As shown in FIG. 1, a wheel rolling bearing device A (a so-called wheel hub unit) includes a shaft member 1, an outer ring 45, an inner ring 42, a first rolling element 50, a second rolling element 51, and the like. It is configured.
The shaft member 1 (so-called hub wheel) integrally includes a shaft portion 10, a fitting shaft portion 30, a flange base portion 20, and a flange portion 21.
When the wheel rolling bearing device A is attached to the vehicle, the shaft portion 10 is located inside the vehicle, the fitting shaft portion 30 is located outside the vehicle, and in FIG. Indicates the inside of the vehicle, and the right direction of the page indicates the outside of the vehicle.

The shaft portion 10 has a substantially cylindrical shape. The shaft portion 10 is formed with a large-diameter shaft portion 11 having a large diameter on the side close to the flange portion 21, and at an end portion far from the flange portion 21 than the large-diameter shaft portion 11. A small-diameter shaft portion 12 having a small diameter is formed. Further, an inner ring abutting surface 12 a that is a surface orthogonal to the rotation axis of the shaft portion 10 is formed at the step portion between the large diameter shaft portion 11 and the small diameter shaft portion 12.
The flange base portion 20 is located between the shaft portion 10 and the fitting shaft portion 30 described later, and a plurality of flange portions 21 that extend radially outward from the outer peripheral surface of the flange base portion 20. (See FIG. 2) is formed. The plurality of flange portions 21 are provided with bolt holes 24 through which hub bolts 27 for fastening the wheels are arranged by press fitting.
In the following description of the present embodiment, a shaft member having the flange portion 21 having the shape shown in FIG. 2B in which the flange portion 21 extends in a disk shape in the outer diameter direction will be described as an example. In addition, as shown to FIG. 2 (A), it is applicable also to the shaft member which has the flange part 21 of the shape where the some flange part 21 was radially extended in the outer-diameter direction.
The fitting shaft portion 30 is formed on one end side of the shaft portion 10 (on the side opposite to the small-diameter shaft portion 12), is coaxially formed with the shaft portion 10 and is formed into a continuous, substantially cylindrical shape, and has a wheel (not shown). Center hole is fitted.
The fitting shaft portion 30 is formed with a brake rotor fitting portion 31 on the flange portion 21 side, and a wheel fitting portion 32 having a slightly smaller diameter than the brake rotor fitting portion 31 on the distal end side. Yes.
Further, as shown in FIG. 1, the surface around the center hole of the brake rotor 55 abuts on the rotor support surface 22 that is the surface of the flange portion 21 on the side of the fitting shaft portion 30.
As shown in FIG. 3, the shaft member 1 has a fitting shaft portion 30, an intermediate shaft portion 23, and a shaft portion 10 formed coaxially along the rotation axis direction. The intermediate shaft portion 23 includes a flange base portion 20 and a flange portion 21.
A concave forged concave portion 35 is formed on the inner diameter side of the fitting shaft portion 30.

Further, a part of the outer peripheral surface of the large-diameter shaft portion 11 in the vicinity of the boundary portion with the flange portion 21 (flange base portion 20) constitutes one bearing portion in a double row angular ball bearing as a rolling bearing. One inner ring raceway surface 18 is formed to be continuous in the circumferential direction.
Further, a seal surface 19 described later that is continuous in the circumferential direction is formed on a part of the outer peripheral surface adjacent to the first inner ring raceway surface 18 and close to the flange portion 21.
Further, an inner ring 42 having a second inner ring raceway surface 44 formed so as to be continuous in the circumferential direction is fitted on the outer circumferential surface of the small-diameter shaft portion 12. The inner ring 42 is fitted until it hits the inner ring abutting surface 12a.
And the protrusion part from the inner ring | wheel 42 in the small diameter shaft part 12 (shaft end part 15 in FIG. 1) is caulked radially outward to form a caulking part 17, and the caulking part 17 and the inner ring abutting surface 12a The inner ring 42 is fixed.

An outer ring 45 is disposed on the outer peripheral surface of the shaft portion 10 of the shaft member 1 while maintaining an annular space.
On the inner circumferential surface of the outer ring 45, the first outer ring raceway surface 46 facing the first inner ring raceway surface 18 formed on the shaft member 1 and the second inner ring raceway surface 44 formed on the inner ring 42 are opposed. A second outer ring raceway surface 47 is formed. Each inner ring raceway surface and each outer ring raceway surface are formed to be continuous in the circumferential direction on each surface.
Between the first inner ring raceway surface 18 and the first outer ring raceway surface 46, a plurality of first rolling elements 50 are held by a cage 52 and arranged so as to be able to roll. Further, between the second inner ring raceway surface 44 and the second outer ring raceway surface 47, a plurality of second rolling elements 51 are held by a cage 53 and arranged so as to be able to roll.
The plurality of first rolling elements 50 and the plurality of second rolling elements 51 are subjected to axial preload based on the caulking force when the caulking portion 17 is formed by caulking the end of the small diameter shaft portion 12. An angular ball bearing is provided.

Further, a vehicle body side flange 48 is integrally formed on the outer peripheral surface of the outer ring 45, and the vehicle body side flange is a mounting surface of a vehicle body side member such as a knuckle or a carrier supported by a vehicle suspension device (not shown). Fastened with bolts or the like.
A seal member 56 is press-fitted and assembled to the inner peripheral surface of the opening of the outer ring 45 adjacent to the first outer ring raceway surface 46. The tip of the lip 58 of the seal member 56 is in sliding contact (contact) with the seal surface 19 to seal the gap between the outer ring 45 and the shaft member 1.
The seal surface 19 is formed on a part of the outer peripheral surface adjacent to the first inner ring raceway surface 18 and close to the flange portion 21 (flange base portion 20) so as to be continuous in the circumferential direction.

● [Method of manufacturing shaft member 1 (FIGS. 4 and 5)]
Next, the manufacturing method of the shaft member 1 is demonstrated using FIG. 4, FIG.
FIGS. 4A to 4N show how the shaft member 1 is molded from the shaft-shaped material 7A through each step, and FIG. 5 shows the post-coating forging intermediate molding before being molded by cold forging. The external appearance of the product 7I (see FIG. 4I) is shown.
As shown in FIG. 4, the shaft member 1 described in the present embodiment has a heating process (B), a first hot forging process (C), and a second heat from the shaft-shaped material 7A shown in (A). Hot forging step (D), third hot forging step (E), first cooling step (F), second cooling step (G), first surface treatment step (H), second surface treatment step (I) It is manufactured through a cold forging process (J), a turning process (K), a heat treatment process (L), a drilling process (M), and a polishing process (N).
First, in FIG. 4A, prior to the heating step (B), a substantially cylindrical structural carbon steel having a carbon content of about 0.5%, such as S45C, S50C, S55C, etc., is cut into a predetermined length to form a shaft. A material 7A is formed.

[Heating step (FIG. 4B)]
The heating step is a step of heating the shaft-shaped material 7A to a hot temperature that is equal to or higher than the transformation point temperature to obtain a heated material 7B having fluidity (see FIG. 4B). For example, when the transformation point temperature is around 950 [° C.], the shaft-shaped material 7A is heated to 1000 [° C.] or higher. In this case, since the surface of the post-heating material 7B is at a temperature equal to or higher than the transformation point temperature, an oxide scale is generated.

[First Hot Forging Process (FIG. 4C) to Third Hot Forging Process (FIG. 4E)]
The hot forging step is a step for obtaining a forged intermediate molded product 7E by hot forging the post-heating material 7B having a fluidity and having a temperature equal to or higher than the transformation point temperature using a mold (FIG. 4C). (See (E)). In the example shown in FIG. 4, the hot forging process includes a first hot forging process (FIG. 4C) to a third hot forging process (FIG. 4E), and each heat In the intermediate forging process, the post-heating material 7B is molded stepwise. In this case, in the first hot forging process to the third hot forging process, the post-heating material 7B is a forged final molded product that is the shape of the shaft-shaped material 7A (corresponding to the shape of the steel material) and the final shape in forging. 7J (molded product obtained in the cold forging process shown in FIG. 4 (J)) and a forged intermediate molded product 7E having an intermediate shape are obtained in each hot forging step. Therefore, the intermediate mold product mold is used to form the forged intermediate molded product 7E via the intermediate molded products 7C, 7D and the like.
Moreover, since the post-heating material 7B is heated to a hot temperature (for example, 1000 [° C.] or higher) and has fluidity, the degree of freedom in molding is large, and the first hot forging process to the third hot forging process are performed. Each of the intermediate molds used in the above may be a mold having a relatively simple structure.
Further, the forged intermediate molded product 7E has a fitting shaft portion 30 ′, a flange portion 21 ′, and a shaft portion 10 ′ molded therein, and is a molded product of about 80% with respect to the forged final molded product 7J. For example, the diameter D1 of the flange portion 21 ′ of the forged intermediate molded product 7E is smaller than the diameter D2 of the flange portion 21 of the forged final molded product 7J, and the depth E1 of the forged concave portion 35 ′ of the forged intermediate molded product 7E is the final forged shape. It is shallower than the depth E2 of the forged recess 35 of the molded product 7J.
Moreover, although the example of FIG. 4 demonstrated the example which shape | molds the forge intermediate molded product 7E in steps in three hot forging processes (FIG.4 (C)-(E)), it is limited to 3 times. It is not a thing.

[First cooling step (FIG. 4F)]
In the first cooling step, the forged intermediate molded product 7E molded at a hot temperature equal to or higher than the transformation point temperature is cooled at a predetermined cooling rate by, for example, furnace cooling, and is subjected to an annealing treatment after annealing. This is a step of obtaining a product 7F (see FIG. 4F). That is, a 1st cooling process is a process of performing an annealing process. The forged intermediate molded product 7E has already been heated to the hot temperature in the hot forging process, so that it is not necessary to heat it again and the annealing process can be performed efficiently.
The forged intermediate molded product 7E is cooled to a preset temperature / time (for example, about 500 [° C.] and lower than the temperature during the hot forging step) in the first cooling step. And after annealing (spheroidizing) and cooling at a cooling rate of 100 [° C. or less], rigidity and ductility are improved, and a post-annealing forged intermediate molded product 7F having a composition suitable for cold forging and Become.
Further, at the beginning of the first cooling step, the forged intermediate molded product 7E is maintained for a predetermined time (for example, about 3 hours) at a temperature around the temperature at which austenite starts to be generated during heating (so-called AC1 transformation temperature), and then the intermediate setting is performed. You may make it cool with the cooling rate of cooling preset temperature / time until it becomes temperature.
The cooling rate of Patent Document 1 is disclosed as 0.25 ° C./s to 3 ° C./s (in terms of conversion, 900 [° C.] / Hour to 10800 [° C.] / Hour). It is a very rapid cooling rate for [° C.] or less / hour. In the present embodiment, an annealing process capable of obtaining desired rigidity and ductility is performed at a cooling rate that is much slower than that of Patent Document 1.

[Second Cooling Step (FIG. 4G)]
The second cooling step is a step of cooling the post-annealed forged intermediate molded product 7F cooled to an intermediate set temperature to room temperature to obtain a post-cooled forged intermediate molded product 7G (see FIG. 4G). In the second cooling step, the regulation of the cooling rate is not particularly required. For example, the cooling rate may be left in the room and cooled by air cooling until the temperature reaches room temperature. That is, the second cooling step is not a step of performing a special heat treatment but a step of simply cooling (leaving) to room temperature.
In the first cooling step and the second cooling step described above, the forged intermediate molded product 7E is cooled at a cooling rate of 100 [° C.] or less / hour until it reaches 500 [° C.] (for example, furnace cooling). An example of air cooling after leaving below [° C.] by leaving it to room temperature has been described. However, in the first cooling step and the second cooling step, the forged intermediate molded product 7E is cooled at a cooling rate of 30 [° C.] or less / hour until it reaches 600 [° C.] (for example, furnace cooling) to 600 [° C.]. After falling below, it may be allowed to air cool by leaving it to room temperature.

[First surface treatment step (FIG. 4H)]
The first surface treatment step is a step of obtaining an after-removed forged intermediate molded product 7H after removing the oxidized scale generated on the surface of the forged intermediate molded product 7G after cooling by hot forging. is there.
The post-cooling forged intermediate molded product 7G has a smooth surface by shot blasting, and an altered portion (oxidized scale portion) is appropriately removed.

[Second surface treatment step (FIG. 4I)]
Prior to the cold forging step, the second surface treatment step is performed by coating the surface of the post-removed forged intermediate molded product 7H with a coating that reduces friction with the mold in the cold forging, and the coating 36 is applied. This is a step for obtaining a forged intermediate product 7I after coating (see FIG. 4I). The coating 36 may be coated on at least one of the surface of the forged intermediate molded product 7H after surface removal or the surface in contact with the forged intermediate molded product 7H after surface removal in the mold. The example of FIG. 4 (I) shows an example in which the forged intermediate molded product 7H after the surface removal is coated.
For example, the post-surface removal forged intermediate molded product 7H becomes a post-coated forged intermediate molded product 7I coated with a phosphate coating with a phosphate as a lubricant applied to the surface.

[Cold forging process (FIG. 4 (J))]
In the cold forging step, the final forged product is formed by cold forging the post-coated forged intermediate molded product 7I (or the forged intermediate molded product 7H after the surface removal if the coating is applied only to the die). This is a step of obtaining a molded product 7J (see FIG. 4J).
Here, the external appearance of the post-coating forged intermediate molded product 7I is shown in FIGS. 5 (A) and 5 (B). The surface of the post-coating forged intermediate product 7I is so smooth that it has gloss, and it is possible to reduce friction with the mold. In addition, the post-coating forged intermediate molded product 7I is molded to a shape that is almost similar to the forged final molded product 7J (for example, a shape of about 80%). Therefore, since the amount of plastic deformation by the cold forging process may be very small (in this case, the remaining 20% may be sufficient), the final mold may be a simple mold and efficiently in a short time. Cold forging can be performed.
For example, the post-coating forged intermediate molded product 7I is used until the depth E1 of the forged recess 35 becomes the depth E2 of the forged final molded product 7J, and the diameter D1 of the flange portion 21 becomes the diameter D2 of the forged final molded product 7J. Molded by cold forging.
Further, the forged final molded product 7J formed by cold forging is more dimensional accuracy and surface smoothness than the case where the final forged molded product is formed by warm forging or hot forging for the reasons described above. In this case, the surface hardness can be improved.

[Turning process (Fig. 4K)]
The turning process is a process of turning a part of the forged final molded product 7J to obtain a final molded product 7K after the turning (see FIG. 4K). In the forged final molded product 7J, for example, the rotor support surface 22, the end surface 33 of the fitting shaft portion 30, the first inner ring raceway surface 18, the large diameter shaft portion 11, the small diameter shaft portion 12, and the inner ring abutting surface 12a are turned. The coating 36 is left on the part that is not turned (see FIG. 3).
In this turning process, at least the coating 36 of the wheel fitting portion 32 (see FIG. 3) of the fitting shaft portion 30 of the forged final molded product 7J is left without being turned.
In the present embodiment, as shown in FIG. 3, a seal surface 19 (adjacent to the surface of the flange portion 21 opposite to the rotor support surface 22 and the shoulder portion of the first inner ring raceway surface 18 is provided. Equivalent to the outer peripheral surface), the surface of the forged recess 35, and the end face of the shaft end portion 15 at the tip of the small diameter shaft portion 12 of the shaft portion 10 are also left without being turned. Then, the turning range is reduced by the amount of the coating film 36 left, and the turning process is easy and takes a short time.

[Heat treatment process (FIG. 4 (L))]
The heat treatment step (quenching and tempering step) is a step in which the first inner ring raceway surface 18 of the shaft portion 10 of the final molded product 7K after turning is induction-quenched and then tempered to obtain a final molded product 7L after the heat treatment (FIG. 4 (L)). As a result, a hardened layer S is formed around the first inner ring raceway surface 18 by quenching and tempering (see FIG. 3).
Note that the heat treatment step time can be shortened by not subjecting the seal surface 19, the outer peripheral surface of the small-diameter shaft portion 12, and the inner ring abutting surface 12a to induction hardening.
In the present embodiment, structural carbon steel having a relatively large amount of carbon and high hardness is used, so that a high frequency is provided at the boundary portion between the shaft portion 10 and the flange portion 21 (flange base portion 20) around the seal surface 19. The necessary strength can be ensured without quenching.

[Drilling process (Fig. 4 (M))]
The drilling step is a step of drilling the bolt holes 24 in the flange portion 21 of the final molded product 7L after heat treatment to obtain the final molded product 7M after drilling (see FIG. 4M).

[Polishing process (FIG. 4 (N))]
The polishing step is a step of polishing the first inner ring raceway surface 18 of the final molded product 7M after drilling to obtain a final molded product 7N after polishing (see FIG. 4 (N)).
The manufacturing process of the shaft member 1 of the rolling bearing device for wheels is thus completed, and the final molded product 7N after polishing obtained by the steps of FIGS.

In the conventional manufacturing method in which the final forged product is forged only by hot forging (forging at a temperature equal to or higher than the transformation temperature of the material), the degree of freedom of molding is large and the forging pressure can be reduced compared to cold forging. Therefore, it has the merit that a relatively small and simple mold may be used, but the dimensional accuracy and surface roughness are inferior to those of cold forging. It has a demerit that requires a process. The reason why the dimensional accuracy is inferior is that in hot forging, heat gathers in the thick part during cooling and deflection tends to occur, and the reason why the surface roughness is inferior is that the surface is oxidized when heated to a temperature above the transformation point. This is because scale occurs.
In addition, the conventional manufacturing method in which the final forged product is forged only by cold forging has the advantage of superior dimensional accuracy and surface roughness compared to hot forging, but the forging pressure is hot. Since it is higher than intermediate forging, it has the disadvantage of requiring a relatively large and complicated mold.
However, the manufacturing method of the shaft member 1 of the rolling bearing device for a wheel described in the present embodiment is an advantage of hot forging in an appropriate process of combining hot forging and cold forging in molding by forging. And the advantages of cold forging can be obtained.
That is, most of the molding is performed by hot forging with a large degree of freedom of molding to obtain the merits of hot forging, and then the remaining molding amount (less plastic deformation amount) is performed by cold forging. Get the benefits of cold forging. As described above, the hot forging die may be relatively small and simple, and the cold forging die having a small amount of plastic deformation may be relatively small and simple. Accordingly, forging can be performed more efficiently with a simpler mold.
Also, since most of the shaft member 1 is molded by hot forging, oxidized scale is generated on the surface, but the surface is smoothed by performing shot blasting to smooth the surface before cold forging. In addition, the altered portion can be appropriately removed.
Further, the annealing process of the forged intermediate molded product 7E is performed by using the heat at the time of hot forging after the hot forging and before the cold forging in the first cooling step, so it is necessary to heat it again. Therefore, the annealing process can be performed more efficiently. Further, the forged intermediate molded product 7E is cooled at an appropriate cooling rate or the like and is subjected to an annealing process, and becomes a post-cooling forged intermediate molded product 7G having both desired rigidity and ductility.
In addition, after performing the annealing process, which requires appropriate temperature control in the first cooling process, to an appropriate intermediate set temperature, the second cooling process cools (stands) to room temperature without special temperature control. In the second cooling process, no special equipment is required and the process is simple.
Moreover, by removing the oxide scale generated by hot forging by shot blasting (first surface treatment step), it is possible to ensure an appropriate surface roughness and to appropriately remove the altered portion.
And, by applying a film treatment in the second surface treatment step before the cold forging step, it is possible to reduce the resistance between the forged intermediate molded product and the die and perform cold forging more efficiently. The surface of the final forged product can be made smoother.
And when the forged final molded product 7J cold forged from the post-coated forged intermediate molded product 7I coated on the forged intermediate molded product 7H after surface removal is molded by warm forging or hot forging for the reasons described above. The dimensional accuracy is higher than that, the surface becomes smooth, and the surface hardness is improved.

The method of manufacturing the shaft member of the rolling bearing device for a wheel according to the present invention is not limited to the steps and processes described in the present embodiment, and various modifications, additions and deletions are possible without departing from the scope of the present invention. It is. Further, the shape or the like of the shaft member 1 to be manufactured is not limited to the shape or the like of the shaft member 1 described in the present embodiment.
Moreover, the manufacturing method of the rolling bearing device for wheels demonstrated in this Embodiment was demonstrated using the example of the axial part 10 in which the large diameter axial part 11, the small diameter axial part 12, and the inner ring butting surface 12a were formed. However, the wheel rolling bearing device manufacturing method described in the present embodiment is a wheel rolling bearing including a large-diameter shaft portion 11, a small-diameter shaft portion 12, and a shaft portion that does not have the inner ring abutting surface 12a. It is possible to apply also to the manufacturing method of the shaft member of an apparatus.
The numerical values used in the description of the present embodiment are examples, and are not limited to these numerical values.

1 Shaft member (shaft member of rolling bearing device for wheels)
DESCRIPTION OF SYMBOLS 10 Shaft part 11 Large diameter shaft part 12 Small diameter shaft part 12a Inner ring contact surface 15 Shaft end part 17 Caulking part 18 1st inner ring raceway surface 19 Seal surface (adjacent outer peripheral surface)
20 Flange base portion 21 Flange portion 30 Fitting shaft portion 36 Lubricant coating 42 Inner ring 44 Second inner ring raceway surface 45 Outer ring 46 First outer ring raceway surface 47 Second outer ring raceway surface 7A Shaft material 7E Forging intermediate molding 7J Forging final molding A Rolling bearing device for wheel

Claims (5)

A fitting shaft portion having a cylindrical shape with a recess opening in the axial direction;
A flange portion having a disk shape or a radial shape perpendicular to the axial direction;
In the method of manufacturing a shaft member of a rolling bearing device for a wheel in which a shaft portion having a columnar shape in which an inner ring raceway surface is formed on an outer peripheral surface, is disposed coaxially along the axial direction.
A heating step of heating the steel material to a hot temperature that is a temperature equal to or higher than the transformation point temperature of the steel material;
Forming the steel material at the hot temperature using a mold for intermediate molded product so as to be a forged intermediate molded product having an intermediate shape between the shape of the steel material and a forged final molded product which is a final shape in forging. A hot forging process,
Cold forging which forms the shape of the fitting shaft portion, the flange portion and the shaft portion into the shape of the forged final molded product by cold forging the forged intermediate molded product using a mold for the final molded product And having a process
Manufacturing method of shaft member of rolling bearing device for wheel. It is a manufacturing method of the shaft member of the rolling bearing device for wheels according to claim 1,
After the hot forging step, the first forged intermediate product is gradually cooled at a cooling set temperature / hour rate until it reaches an intermediate set temperature set lower than the temperature during the hot forging step. Having a cooling step,
Manufacturing method of shaft member of rolling bearing device for wheel. It is a manufacturing method of the shaft member of the rolling bearing device for wheels according to claim 2,
After the first cooling step, the second forging intermediate molded product cooled to the intermediate set temperature further has a second cooling step for cooling to room temperature.
Manufacturing method of shaft member of rolling bearing device for wheel. It is a manufacturing method of the shaft member of the rolling bearing device for wheels according to any one of claims 1 to 3,
Before the cold forging step, it has a first surface treatment step of shot blasting the surface of the forged intermediate molded product,
Manufacturing method of shaft member of rolling bearing device for wheel. It is a manufacturing method of the shaft member of the rolling bearing device for wheels according to claim 4,
After the first surface treatment step, the forged intermediate molded product is provided on at least one of the surface of the forged intermediate molded product that has been shot blasted or the surface that contacts the forged intermediate molded product in the mold for the final molded product. And a second surface treatment step of applying a coating treatment to reduce the frictional force between the final molded product mold,
Manufacturing method of shaft member of rolling bearing device for wheel.