JP2024029100A - Shaft enlargement processing method and shaft enlargement processing device - Google Patents

Abstract

An object of the present invention is to provide a shaft enlargement processing method and a shaft enlargement processing apparatus that can increase the enlargement rate, suppress the occurrence of cracks due to enlargement, and reduce running costs.
[Solution] A shaft member W is held by a pair of holders 2 and 3 with an interval in the axial direction, and an axial compressive force is applied to an intermediate portion Wa of the shaft member W disposed between the pair of holders 2 and 3. A shaft enlargement processing method in which the intermediate portion Wa is enlarged by applying an alternating load in a direction intersecting the axial direction, and the temperature of the intermediate portion Wa is increased to a temperature exceeding the blue brittle temperature range of the shaft material W. Then, the temperature of the holders 2 and 3 is set to a temperature lower than the tempering temperature range of the holders 2 and 3, and the intermediate portion Wa is enlarged.
[Selection diagram] Figure 3

Description

The present invention relates to a shaft enlargement processing method and a shaft enlargement processing apparatus.

Conventionally, when providing a large diameter part in the middle of a shaft material, it is necessary to cut the thick shaft material, form it by plastic processing such as forging and finish it by cutting, or add a separate part to the shaft material. The method used was to join by welding. However, when cutting the material, it is not only time-consuming but also wasteful of material, which is uneconomical. It was difficult to get it out. Furthermore, the method of joining separate parts to a material by welding has the problem of being affected by welding heat.

In order to solve this problem, there is a shaft enlarging method in which the intermediate portion of the shaft material is enlarged by applying rotation, compressive force, and bending to the shaft material. According to this technique, a large diameter portion can be easily formed in the middle portion of the shaft material, so there is no need for cutting or welding as in the conventional method.

To explain this conventional technique in detail, a linear shaft member is held by a pair of holders spaced apart at a predetermined interval. Then, rotation is applied around the axis of this shaft member, and in this state, at least one of the holders is moved in a direction approaching the other, and one of the pair of holders is gradually biased in a direction that intersects the axis. . As a result, compressive force and bending force are applied to the rotating shaft member under the condition that compressive stress is always applied even on the outside of bending, and plastic deformation in the diametrical direction is caused in the shaft member between both holders. Thereafter, the deflection of the holder is gradually restored while maintaining the condition that compressive stress acts on the outside of the bending, thereby enlarging the intermediate portion of the shaft member.

However, in the above technology, when applying bending and rotation to the shaft material, compression force is applied and rotation is performed, bending is performed to obtain the desired shape, and then the shaft material is bent back and compression and rotation are stopped. Therefore, when the shaft material is made of high-strength steel or large-sized shaft steel, a high compressive force is required, and it is essential to increase the size of the equipment that applies the shaft enlargement process to the shaft material. On the other hand, if the compressive force is low, the number of rotations required for the shaft enlargement process will increase until the desired shape is obtained, so there is a problem in that it takes time. Furthermore, the limit is to obtain an enlargement rate of about twice (the outer diameter of the enlarged middle portion of the shaft material/the diameter of the material of the shaft material), and the parts to which it can be applied are also limited.

Therefore, in the shaft enlargement processing method described in Patent Document 1, the deformation resistance of the shaft member is reduced by heating the shaft member before or during the shaft enlargement processing. According to this, it becomes possible to enlarge the intermediate portion of the shaft member with a small compressive force, and it is possible to avoid increasing the size of the device. Furthermore, since it becomes possible to improve the plastic deformability of the shaft material, it becomes possible to increase the enlargement rate more than before.

In addition, in the shaft enlargement processing method described in Patent Document 2, when the shaft material is heated to the blue brittle region, effects such as blue brittleness occur, and the shaft material is hardened and the deformation resistance increases. In view of the fact that the desired enlarged portion may not be obtained and problems such as cracks occurring in the shaft material may occur, the shaft material is heated to a temperature exceeding the blue brittle region. As an example, Patent Document 2 states that when the shaft material is made of structural carbon steel JIS-S45C, when the temperature of the shaft material is about 400°C or less, the expansion rate of the shaft material is affected by blue brittleness. It is stated that heating the shaft material has no effect, and that by heating the shaft material to a temperature of 580° C. or higher, an enlargement rate of more than double can be obtained, and the occurrence of cracking damage can also be suppressed.

Japanese Patent Application Publication No. 2005-88066 Japanese Patent Application Publication No. 2007-167882

In forging that plastically deforms a workpiece in the same way as axial enlargement processing, in so-called warm forging, the workpiece is typically heated to 700°C to 850°C, and in hot forging (including subhot forging), the workpiece is heated to 700°C to 850°C. is typically heated to 950°C or higher. Therefore, when performing shaft enlargement processing by heating the shaft material to 580°C or higher, it is necessary to heat the shaft material to a warm range (700°C to 850°C) or a hot range (950°C or higher), similar to forging. is possible. However, when applying rotation, compressive force, and bending to the shaft material during shaft enlargement processing, a load also acts on the holder that holds the shaft material. The holder is generally made of tool steel such as die steel and high speed steel, and the tempering temperature range of these tool steels is approximately 500°C to 580°C. Furthermore, the time during which the shaft material and the holder are in contact is relatively longer than the time during which the workpiece and the die are in contact during forging. Therefore, when the shaft material is heated to a warm or hot temperature range, there is a possibility that the holder will be tempered and the hardness of the holder will decrease. When the hardness of the holder decreases, the durability of the holder against repeated use decreases, resulting in a shortened lifespan of the holder.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a shaft enlargement processing method and a shaft enlargement processing apparatus that can increase the enlargement rate, suppress the occurrence of cracks due to enlargement, and reduce running costs. With the goal.

In the shaft enlargement processing method according to one aspect of the present invention, a shaft member is held by a pair of holders at intervals in the axial direction of the shaft member, and an intermediate portion of the shaft member disposed between the pair of holders is A shaft enlarging method for enlarging the intermediate portion by applying a compressive force in the axial direction and applying an alternating load in a direction crossing the axial direction, the method comprising: The intermediate portion is enlarged by setting the temperature to a temperature exceeding the thermal brittle temperature range and setting the temperature of the holder to a temperature below the tempering temperature range of the holder.

A shaft enlargement processing device according to one aspect of the present invention includes a pair of holders that are arranged at intervals in the axial direction of a shaft material and hold the shaft material, and a shaft material that is arranged between the pair of holders. a pressure unit that applies a compressive force in the axial direction to the intermediate portion; an alternating load generating unit that applies an alternating load in a direction intersecting the axial direction to the intermediate portion of the shaft member; and the intermediate portion of the shaft member. The temperature of the intermediate portion of the shaft member exceeds the blue brittle temperature range of the shaft member during the period in which the compressive force and the alternating load are applied to the part, and the pair of members holding the shaft member A heating unit is provided that heats at least a portion of the shaft material so that the temperature of the holder is lower than the tempering temperature of the holder.

According to the present invention, the enlargement rate can be increased, the occurrence of cracks due to enlargement can be suppressed, and running costs can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an example of a shaft enlargement processing apparatus for explaining an embodiment of the present invention. It is a graph showing the relationship between temperature and tensile strength of various steel materials with different carbon contents. (A) to (E) are schematic diagrams illustrating an example of a shaft enlargement processing method using the shaft enlargement processing apparatus of FIG. 1. FIG. It is a schematic diagram explaining another example of the shaft enlargement processing method for explaining the embodiment of the present invention. It is a schematic diagram explaining other examples of the shaft enlargement processing method for explaining the embodiment of the present invention. It is a schematic diagram explaining another example of the shaft enlargement processing method for explaining the embodiment of the present invention. It is a schematic diagram explaining another example of the shaft enlargement processing method for explaining the embodiment of the present invention. It is a graph showing the results of measuring the number of rotations required to obtain a predetermined enlargement rate in an experimental example and the results of checking the presence or absence of cracks. It is a graph which shows the evaluation result of the ellipse amount of an experimental example. It is a schematic diagram of an example of the heating part of the shaft enlargement processing apparatus for explaining the embodiment of the present invention. It is a schematic diagram of another example of the heating part of the shaft enlargement processing apparatus for explaining the embodiment of the present invention. It is a schematic diagram of another example of the heating part of the shaft enlargement processing apparatus for explaining the embodiment of the present invention. It is a schematic diagram of another example of the heating part of the shaft enlargement processing apparatus for explaining the embodiment of the present invention.

FIG. 1 shows an example of a shaft enlargement processing apparatus for explaining an embodiment of the present invention.

The shaft enlarging processing device 1 shown in FIG. A compressive force in the axial direction is applied to the intermediate portion of the shaft material W disposed between the holders 2 and 3, and a compressive force in the axial direction is applied to the intermediate portion of the shaft material W disposed between the pair of holders 2 and 3. By applying an alternating load in the direction of the shaft member W, the intermediate portion of the shaft member W is enlarged while being compressed in the axial direction.

The holder 2 is supported by a support base 4 so as to be movable along a reference line A along which the shaft member W is arranged, and is moved by a translation drive unit (pressure unit) 5. By moving the holder 2 toward the holder 3 along the reference line A, an axial compressive force is applied to the intermediate portion of the shaft material W held by the holders 2 and 3, and the intermediate portion of the shaft material W is is compressed.

Then, the shaft enlarging processing device 1 applies an alternating load in a direction intersecting the axial direction to the intermediate portion of the shaft material W by adding a bending angle to the intermediate portion of the shaft material W and rotating the shaft material W. . The holder 3 is tilted with respect to the reference line A by the tilting drive unit (alternating load generating unit) 6, and a bending angle is added to the intermediate portion of the shaft member W. Then, the holder 3 is rotated by the rotation drive section (alternating load generation section) 7 with the bending angle being applied to the middle portion of the shaft member W. As the holder 3 is rotated, the shaft member W held by the holder 3 is rotated, and the holder 2 holding the shaft member W is also rotated following the holder 3 and the shaft member W.

The control section 8 controls the translation drive section 5, the tilt drive section 6, and the rotation drive section 7 based on the set machining conditions.

In the shaft enlargement method of the present invention, the intermediate portion of the shaft material W is heated before and/or during the shaft enlargement process. Note that only the intermediate portion may be heated, or the entire shaft member W including the intermediate portion may be heated.

The shaft material W can be heated using a furnace such as a combustion furnace or an electric furnace. Moreover, resistance heating and induction heating can also be used as another heating method. Resistance heating involves bringing an electrode into contact with a conductive material to be heated, applying electricity directly to the material to be heated, and causing the material to generate heat using the Joule heat. In induction heating, a heating coil connected to an AC power source is placed close to the material to be heated, and the alternating magnetic flux generated by the heating coil intersects with the material to be heated, thereby creating eddy currents on the surface of the material to be heated. The Joule heat causes the surface of the heated material to generate heat.

Resistance heating can locally heat the middle part of the shaft material W held by a pair of holders 2 and 3 by bringing an electrode into contact with the middle part, while induction heating can heat the middle part of the shaft material W held by a pair of holders 2 and 3. A heating coil can be placed close to the middle part of the material W to locally heat the middle part, and both can be suitably used for heating during shaft enlargement processing. Among these, induction heating, which can heat the shaft material W without contacting it, is suitable.

In the shaft enlargement processing method of the present invention, the temperature of the intermediate portion of the shaft material W is set to a temperature exceeding the blue brittle region of the shaft material W and below the tempering temperature range of the holders 2 and 3, The middle part becomes enlarged.

FIG. 2 shows the relationship between temperature and tensile strength (stress) of various steel materials with different carbon contents.

The graph shown in FIG. 2 is from "Steel Materials Handbook," edited by the Japan Institute of Metals, Japan Iron and Steel Institute, 1st edition, Maruzen Co., Ltd., June 1967, p. 552'', and basically the tensile strength of steel decreases as the temperature of the steel increases. This means that in the shaft enlarging process, by increasing the temperature of the shaft material W, the deformation resistance when enlarging the intermediate portion of the shaft material W can be reduced. However, in the blue brittle region (approximately 200°C to 400°C in the example shown), the tensile strength increases with increasing temperature; On the other hand, the tensile strength decreases again.

Therefore, in the shaft enlargement processing method of the present invention, the temperature of the intermediate portion of the shaft material W is set to a temperature exceeding the blue brittle region of the shaft material W. Thereby, it is possible to reduce the deformation resistance when the intermediate portion of the shaft material W is enlarged, increase the enlargement rate, and suppress the occurrence of cracks due to enlargement.

As the shaft material W, a solid round bar or a hollow round bar with a circular cross section is used, which is made of a steel material such as carbon steel for machine structures (for example, JIS-S45C) or alloy steel for machine structures (for example, JIS-SCr420H). The upper end temperature of the blue brittle region of -S45C is a little less than 400°C, and the upper end temperature of the blue brittle region of JIS-SCr420H is also a little less than 400°C. Therefore, the temperature of the intermediate portion of the shaft member W is preferably 400° C. or higher.

At temperatures exceeding the blue brittle region, the tensile strength monotonically decreases as the temperature of the intermediate portion of the shaft material W increases. Therefore, from the viewpoint of increasing the enlargement rate and suppressing the occurrence of cracks due to enlargement, there is no upper limit to the temperature of the intermediate portion of the shaft material W. However, the temperature of the holders 2, 3 increases due to heat conduction from the shaft material W to the holders 2, 3, and when the temperature of the holders 2, 3 reaches the tempering temperature range, the hardness of the holders 2, 3 decreases due to tempering. There is a possibility. Therefore, in the shaft enlargement processing method of the present invention, the temperature of the holders 2 and 3 is set to be lower than the tempering temperature range of the holders 2 and 3. Thereby, the hardness of the holders 2 and 3 can be prevented from decreasing due to tempering, and the life of the holders 2 and 3 can be extended.

The holders 2 and 3 are generally made of tool steel such as die steel (for example, JIS-SKD61) or high-speed steel (for example, JIS-SKH51), and the tempering temperature range of JIS-SKD61 is 500°C to 560°C. -The tempering temperature range of SKH51 is 560°C to 580°C. Therefore, the temperature of the holders 2 and 3 is preferably less than 580°C, more preferably less than 500°C.

The temperature of the holders 2 and 3 rises due to heat conduction from the shaft material W. Considering the loss of heat conduction, the upper limit of the temperature of the intermediate portion of the shaft material W in the shaft enlargement processing method of the present invention is determined by the temperature of the holders 2 and 3. Temperatures slightly higher than the tempering temperature range of No. 3 can be tolerated. For example, with respect to the general tempering temperature range (500°C to 580°C) of the holders 2 and 3, the upper limit of the temperature of the intermediate portion of the shaft material W can be set to 700°C. Preferably, the upper limit of the temperature of the intermediate portion of the shaft material W is below the tempering temperature range of the holders 2 and 3, thereby reliably preventing the temperature of the holders 2 and 3 from reaching the tempering temperature range.

With reference to FIG. 3, an example of a shaft enlargement processing method using the shaft enlargement processing apparatus 1 will be described.

In this example, as shown in FIG. 3(A), the intermediate portion Wa of the shaft material W is heated by the heating unit 9 before the shaft enlargement process. Note that the entire shaft material W may be heated. Here, the temperature of the intermediate portion Wa exceeds the blue brittle region of the shaft material W at least at the time when the shaft enlarging process is started, and preferably within the period until all processes of the shaft enlarging process are completed. Heat radiation after heating is taken into consideration so that the temperature of the material W is maintained at a temperature exceeding the blue brittle region, and furthermore, the holders 2 and 3 holding the shaft material W are maintained at a temperature below the tempering temperature range. In consideration of heat conduction from the shaft material W to the holders 2 and 3, the intermediate portion Wa or the entire shaft material W is heated.

Next, as shown in FIG. 3(B), the shaft member W is held by the holders 2 and 3. The axial length L ₀ of the intermediate portion Wa of the shaft material W before processing is defined as the axial length L of the enlarged intermediate portion Wa in relation to D ₀ , with the outer diameter of the intermediate portion Wa being D ₀ It is determined appropriately according to the outer diameter D.

Next, as shown in FIG. 3(C), while the shaft member W is held by the holders 2 and 3, the holder 2 is translated along the reference line A by the translation drive unit 5 (see FIG. 1). , an axial compressive force is applied to the intermediate portion Wa of the shaft member W. Further, the holder 3 is tilted with respect to the reference line A by the tilt drive unit 6 (see FIG. 1), and rotated by the rotation drive unit 7 (see FIG. 1).

The shaft member W held by the holders 2 and 3 is bent around a bending center O on the reference line A of the intermediate portion Wa, and rotated around the central axis. As the shaft member W bends and rotates, an alternating load is applied to the bent intermediate portion Wa in a direction intersecting the axial direction of the shaft member W. The bending angle θ added to the intermediate portion Wa, that is, the inclination angle of the holder 3 with respect to the reference line A, is an angle in which the bending of the shaft member W falls within the deformation of the elastic limit, and varies depending on the elastic limit of the material of the shaft member W. However, it is typically about 2° to 4°.

Next, as shown in FIG. 3(D), the bending inner side of the intermediate portion Wa of the shaft member W bulges due to plastic flow. Then, as the shaft member W is compressed and rotated, a bulge due to plastic flow grows over the entire circumference, and the intermediate portion Wa gradually enlarges. Then, when the distance between the holders 2 and 3 reaches a predetermined distance, the compression of the shaft material W due to the translational movement of the holder 2 is stopped. With this, the process of enlarging the intermediate portion Wa of the shaft material W is completed.

Next, as shown in FIG. 3(E), a compressive force is continuously applied to the shaft member W whose compression has been stopped by the translation drive unit 5 via the holders 2 and 3. Then, the holder 3 tilted with respect to the reference line A is placed again along the reference line A, and the shaft member W is bent back. By bending back the shaft member W, the thickness of the enlarged intermediate portion (hereinafter referred to as enlarged portion) Wa is made even over the entire circumference. Through the above process, the shaft enlarging process on the shaft material W is completed, and the rotation of the shaft material W is stopped. Thereafter, the enlarged portion Wa is subjected to a cutting process or the like as necessary, and the enlarged portion Wa is formed into a desired shape (for example, a cylindrical shape).

Since the temperature of the intermediate portion Wa of the shaft material W exceeds the blue brittle region of the shaft material W, and the deformation resistance of the shaft material W is reduced, the enlargement rate can be increased, for example, the enlargement is doubled or more. In addition, it is possible to suppress the occurrence of cracks due to enlargement. Furthermore, since the holders 2 and 3 are maintained below the tempering temperature range, it is possible to prevent the hardness of the holders 2 and 3 from decreasing due to tempering, extend the life of the holders 2 and 3, and reduce running costs. can. In order to maintain the holders 2 and 3 below the tempering temperature range, the upper limit of the temperature of the intermediate portion Wa of the shaft material W is set to a temperature slightly higher than the tempering temperature range of the holders 2 and 3, and a temperature lower than the warm range. Since decarburization of the intermediate portion Wa can be suppressed, it is possible to remove scale generated on the surface of the intermediate portion Wa due to decarburization, and to remove a decarburized layer whose strength has decreased due to decarburization. It is possible to reduce the amount of cutting required and save material. Furthermore, the energy required to heat the shaft material W can be saved and running costs can be reduced.

In the examples shown in FIGS. 3(A) to 3(E), the intermediate portion Wa of the shaft material W is heated before the shaft enlargement process, but the intermediate portion Wa is heated during the shaft enlargement process. or may be heated before and during the shaft enlargement process. By heating the intermediate portion Wa during the shaft enlarging process, a decrease in temperature due to heat radiation can be suppressed, and the temperature of the intermediate portion Wa can be reliably maintained at a temperature exceeding the blue brittle region. Thereby, the enlargement rate can be further increased, and the occurrence of cracks due to enlargement can be further suppressed.

Furthermore, the explanation has been made assuming that the holder 3 is tilted with respect to the reference line A to bend the shaft member W, and then the shaft member W is rotated around the central axis to apply an alternating load to the intermediate portion Wa of the shaft member W. The method of applying an alternating load to the intermediate portion Wa is not limited to this.

The example shown in FIG. 4 is similar to the shaft enlargement processing method shown in FIGS. 3(A) to 3(E) in that alternating loads are applied to the intermediate portion Wa by bending and rotating the shaft material W, but Instead of tilting the shaft member W, the shaft member W is bent by sliding the holder 3 in a direction intersecting the reference line A.

In the example shown in FIG. 5, the shaft member W is held in a non-rotatably restrained state by the holder 2, the shaft member W is held in a rotatably unrestricted state by the holder 3, and the holder 3 is rotated around the reference line A. By doing so, the intermediate portion Wa of the shaft material W is bent, and an alternating load is applied to the bent intermediate portion Wa of the shaft material W.

In the example shown in FIG. 6, the ends of the shaft material W are held in a non-rotatable state by the holders 2 and 3, and by reciprocating the holder 3 around the reference line A, the intermediate portion Wa of the shaft material W is fixed. It is designed to apply an alternating load.

In the example shown in FIG. 7, an alternating load is applied to the intermediate portion Wa of the shaft member W by applying bending or torsional vibration to the shaft member W from the vibration generator OSC.

An experimental example will be explained below.

In Experimental Example 1, a shaft material made of JIS-SCr420H was heated in an electric furnace before being subjected to shaft enlargement processing, and was heated at a compression force of 2000 kN and a bending angle of 4 using the above-mentioned shaft enlargement processing apparatus 1. Axial enlargement processing was performed under the condition of .0°. The upper temperature of the blue brittle region of JIS-SCr420H is a little less than 400°C. The temperature of the shaft material (temperature at the start of shaft enlargement processing) was varied, and the number of rotations required until the enlargement rate reached 3.0 was measured, and the presence or absence of cracks in the obtained enlarged portion was confirmed. The presence or absence of cracks was confirmed by color checking using a dye penetrant tester. The results are shown in FIG. In addition, in FIG. 8, samples in which cracks were confirmed are indicated by "x", and samples in which cracks were not confirmed are indicated by "○".

As shown in FIG. 8, it can be seen that the higher the temperature of the shaft material, the smaller the number of rotations required for the enlargement ratio to reach 3.0, which indicates that the deformation resistance is smaller. In all of the samples whose shaft material temperature was below 400°C, cracks were confirmed in the enlarged part, whereas in the samples whose shaft material temperature was 400°C or higher, no cracks were observed in the enlarged part. Ta. From the above, it can be seen that by performing shaft enlargement processing at a temperature of the intermediate portion of the shaft material exceeding the blue brittle region, the enlargement rate can be increased and the occurrence of cracks due to enlargement can be suppressed.

Next, in Experimental Example 2, a shaft material is made of JIS-SCr420H and the solidification pattern observed in the cross section of the rolled steel bar is elliptical, and a shaft material is made of JIS-SCr420H and the solidification pattern observed in the cross section of the rolled steel bar is elliptical. A rectangular shaft material was subjected to shaft enlargement processing under the same processing conditions as in Experimental Example 1, varying the temperature of the shaft material (temperature at the start of shaft enlargement processing) until the enlargement rate reached 3.0. The amount of ellipse, which is the difference between the major axis and the minor axis of the obtained enlarged part, was evaluated. The solidification pattern of the shaft material is the cross-sectional shape of the shaft material manufactured by continuous casting and rolling at the time of casting, and the solidification pattern is generally related to the isotropy and anisotropy of the plastic deformation of the shaft material. . The results are shown in FIG.

As shown in FIG. 9, whether the solidification pattern is elliptical or rectangular, the higher the temperature of the shaft material, the smaller the amount of ellipse. In other words, the enlargement progresses isotropically, which also shows that the higher the temperature of the shaft material, the lower the deformation resistance, and in addition, it is less affected by the solidification pattern, and deformation in the circumferential direction progresses uniformly. Recognize. For example, when the enlarged part is machined into a cylindrical shape by cutting after the shaft enlargement process, the smaller the ellipse amount, the smaller the cutting allowance and the less waste of material, which is more economical.

Next, the heating section 9 will be explained.

In the example shown in FIG. 10, the heating unit 9 heats the intermediate portion of the shaft material W or the entire shaft material W including the intermediate portion before the above-mentioned shaft enlargement process. The heating method for the shaft material W is furnace heating, resistance heating, or induction heating. The heating unit 9 is adjacent to the pair of holders 2 and 3, and the shaft material W heated in the heating unit 9 is transferred from the heating unit 9 to the pair of holders 2 and 3 by the robot 10. Then, the shaft material W is held by the pair of holders 2 and 3, and the shaft material W held by the pair of holders 2 and 3 is subjected to the above-mentioned shaft enlargement process.

In the example shown in FIG. 11, the heating unit 9 heats the intermediate portion of the shaft material W held by one of the pair of holders 2 and 3 by induction heating before the shaft enlargement process described above. The heating section 9 has a spiral heating coil 11 . The heating coil 11 is moved along the reference line A, and the shaft member W held by the holder 2 is inserted through the heating coil 11. A high-frequency alternating current is supplied to the heating coil 11, and the intermediate portion of the shaft member W housed inside the heating coil 11 is heated by induction. Note that when the middle portion of the shaft material W is longer than the entire length of the heating coil 11, the heating coil 11 is moved along the reference line A as appropriate. After heating the intermediate portion of the shaft member W, the heating coil 11 is moved along the reference line A, and the shaft member W is removed from the heating coil 11. Next, the heating coil 11 is retracted from above the reference line A. Then, the shaft material W is held by the pair of holders 2 and 3, and the shaft material W held by the pair of holders 2 and 3 is subjected to the above-mentioned shaft enlargement process.

In the example shown in FIG. 12, the heating unit 9 guides the intermediate portion of the shaft material W held by the pair of holders 2 and 3 before and/or during the shaft enlargement process. Heat by heating. The heating section 9 has an arc-shaped heating coil 12. The heating coil 12 is brought close to the middle part of the shaft material W held by the pair of holders 2 and 3, and the heating coil 12 is brought into contact with the inner peripheral surface of the heating coil 12 and the outer peripheral surface of the middle part of the shaft material W facing each other. 12 are placed. A high-frequency alternating current is supplied to the heating coil 12, and the middle portion of the shaft member W facing the inner peripheral surface of the heating coil 12 is heated by induction. When the shaft material W is rotated by the rotational drive unit 7 (see FIG. 1), the intermediate portion of the shaft material W is induction heated over the entire circumference. Note that when the middle portion of the shaft member W is longer than the entire length of the heating coil 12, the heating coil 12 is moved along the reference line A as appropriate. Further, when the intermediate portion of the shaft material W is induction heated during the shaft enlargement process, the heating coil 12 is appropriately moved toward the outer diameter side in accordance with the enlargement of the intermediate portion of the shaft material W. The shaft material W thus heated is subjected to the shaft enlargement process described above.

In the example shown in FIG. 13, the heating unit 9 heats the intermediate portion of the shaft material W held by the pair of holders 2 and 3 with resistance before and/or during the shaft enlargement process. Heat by heating. The heating unit 9 has a pair of electrodes 13 and 14 connected to the holders 2 and 3. A direct current or an alternating current is passed between the pair of electrodes 13 and 14 via the pair of holders 2 and 3 and the intermediate portion of the shaft member W held by the pair of holders 2 and 3, and the intermediate portion of the shaft member W is is resistively heated. The shaft material W thus heated is subjected to the shaft enlargement process described above.

1 Axial enlargement processing device 2 Holder 3 Holder 4 Support stand 5 Translation drive section (pressure section)
6 Tilting drive section (alternating load generation section)
7 Rotation drive section (alternating load generation section)
8 Control part 9 Heating part 10 Robot 11 Heating coil 12 Heating coil 13 Electrode 14 Electrode A Reference line W Shaft material Wa Intermediate part (enlarged part)

Claims (7)

A shaft member having an elliptical solidification pattern observed in a cross section is held by a pair of holders at intervals in the axial direction of the shaft member, and a middle portion of the shaft member disposed between the pair of holders is A axial enlargement processing method for enlarging the intermediate portion by applying a compressive force in the axial direction and applying an alternating load in a direction intersecting the axial direction,
A shaft enlargement processing method in which the temperature of the intermediate portion is set to a temperature exceeding the blue brittle temperature range of the shaft material, and the temperature of the holder is set to a temperature lower than the tempering temperature range of the holder to enlarge the middle part. The shaft enlargement processing method according to claim 1,
A method for enlarging the shaft by increasing the temperature of the intermediate portion to 400° C. or higher and setting the temperature of the holder to less than 580° C. The shaft enlargement processing method according to claim 1 or 2,
A method for enlarging the shaft by enlarging the intermediate portion by setting the temperature of the intermediate portion to 400° C. or higher and 700° C. or lower. The shaft enlargement processing method according to claim 1 or 2,
A method for enlarging a shaft by setting the temperature of the intermediate portion to a temperature exceeding a blue brittle temperature range of the shaft material and below a tempering temperature range of the holder. The shaft enlargement processing method according to any one of claims 1 to 4,
A shaft enlargement processing method that heats at least a portion of the shaft material including the intermediate portion before enlarging the intermediate portion. The shaft enlargement processing method according to any one of claims 1 to 5,
A method for enlarging a shaft by heating the intermediate portion while enlarging the intermediate portion. a pair of holders arranged at intervals in the axial direction of a shaft member whose solidification pattern observed in a cross section is elliptical, and holding the shaft member;
a pressure unit that applies a compressive force in the axial direction to an intermediate portion of the shaft member disposed between the pair of holders;
an alternating load generator that applies an alternating load in a direction intersecting the axial direction to the intermediate portion of the shaft member;
During a period in which the compressive force and the alternating load are applied to the intermediate portion of the shaft material, the temperature of the intermediate portion of the shaft material exceeds the blue brittle temperature range of the shaft material, and the shaft material is maintained. a heating unit that heats at least a portion of the shaft material so that the temperature of the pair of holders is lower than the tempering temperature of the holders;
A shaft enlargement processing device equipped with.

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