QUENCHING METHOD AND RESTRAINT QUENCHING DEVICE

TECHNICAL FIELD

[0001]The present disclosure relates to a quenching method and a restraint quenching device.

BACKGROUND ART

[0002]Performing the heat treatment may cause unintended deformation of a target object. In this respect, there is known so-called press quenching that achieves both implementation of heat treatment of a target object and reduction in deformation of the target object. Patent Literature 1 discloses a press quenching device.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

[0004]The press quenching device disclosed in Patent Literature 1 is used for one target object as a target. That is, the press quenching device disclosed in Patent Literature 1 cannot perform press quenching on a plurality of target objects at a time. On the other hand, a heat treatment step may employ a so-called batch treatment in which a plurality of target objects are treated at a time. Therefore, in the technical field of heat treatment, there are demands for a quenching method and a restraint quenching device capable of performing press quenching on a plurality of quenching target objects.

[0005]According to the present disclosure, a quenching method and a restraint quenching device capable of performing press quenching on a plurality of quenching target objects are described.

Solution to Problem

[0006]An aspect of the present disclosure is a quenching method for a quenching target object which has a disc-shaped area and is provided with a through-hole. A quenching method according to one aspect includes: a step of preparing a restraint quenching device capable of switching between a restraint state in which the quenching target objects are restrained and an unrestraint state in which the quenching target objects are not restrained; a step of arranging a plurality of the heated quenching target objects in the restraint quenching device that is in the unrestraint state; a step of restraining restraint target areas of the quenching target objects by the restraint quenching device by causing the restraint quenching device to switch from the unrestraint state to the restraint state; and a step of cooling the restrained quenching target object.

[0007]In the quenching method described above, the plurality of quenching target objects arranged in a predetermined mode are restrained, and then the quenching target objects in the restraint state are cooled. Hence, the plurality of quenching target objects can be subjected to press quenching.

[0008]The quenching method described above may further include a step of immersing the plurality of heated quenching target objects in a coolant before the step of the restraining. The step of the restraining and the step of the cooling may be performed in a state in which the quenching target objects are not immersed in the coolant. These steps enable the high-temperature quenching target objects to be quickly cooled by the coolant.

[0009]The step of the arranging of the quenching method described above may include a step of arranging the plurality of quenching target objects on a positioning member of the restraint quenching device, and a step of arranging a plurality of restraint members of the restraint quenching device individually between the plurality of the quenching target objects. These steps enable the plurality of quenching target objects to be subjected to the press quenching.

[0010]In the step of the arranging of the quenching method described above, the plurality of quenching target objects may be arranged on the positioning member along axial lines of the through-holes of the quenching target objects. This step enables the plurality of quenching target objects to be restrained by a simple operation.

[0011]In the step of the restraining of the quenching method described above, a first restraint member of the restraint members may be abutted on, as any one of the restraint target areas, a principal surface in any one of the disc-shaped areas of the quenching target objects, and a second restraint member may be abutted on a back surface in any one of the disc-shaped areas. This step enables deformation of the disc-shaped areas of the quenching target objects to be curbed.

[0012]The quenching method described above may further include a step of immersing the quenching target objects arranged in the restraint quenching device in a coolant after the step of the restraining. The step of the restraining may be performed in a state in which the quenching target objects are not immersed in the coolant. The step of the cooling may have a first period in which the cooling is performed in the state in which the quenching target objects are not immersed in the coolant. The step of the cooling may have, following the first period, a second period in which the cooling is performed in a state in which the quenching target objects are immersed in the coolant. This step enables a time from the arrangement to the restraint to be ensured.

[0013]The step of the restraining and the step of the cooling of the quenching method described above may be performed in a state in which the quenching target objects are not immersed in a coolant. This step also enables a time from the arrangement to the restraint to be ensured.

[0014]Another aspect of the present disclosure is a restraint quenching device provided for quenching target objects which have respective disc-shaped areas and are provided with respective through-holes. The restraint quenching device according to the another aspect includes: a positioning member configured to maintain positions and postures of a plurality of the quenching target objects; a plurality of restraint members capable of coming into contact with restraint target areas of the quenching target objects; and a push mechanism configured to push the restraint members toward the restraint target areas. The restraint members and the push mechanism switch between a restraint state in which the quenching target objects are restrained and an unrestraint state in which the quenching target objects are not restrained. This device also enables the plurality of quenching target objects to be subjected to press quenching.

Advantageous Effects of Invention

[0015]According to a quenching method and a restraint quenching device of the present disclosure, a plurality of quenching target objects can be subjected to press quenching.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is a schematic view illustrating a quenching facility to which a quenching method and a press quenching device of the present disclosure are applied.

[0017]FIG. 2 is a cross-sectional view of a workpiece.

[0018]FIG. 3 is a front view of the workpiece.

[0019]FIG. 4(a) is a graph illustrating a temperature change of the workpiece. FIG. 4(b) is a view illustrating a mode immediately after the workpiece is immersed in a coolant. FIG. 4(c) is a view schematically illustrating a mode during a rapid cooling period in which a vapor film is separated from the workpiece. FIG. 4(d) is a view schematically illustrating a mode during a slow cooling period in which the workpiece is in contact with the coolant.

[0020]FIG. 5 is an exploded cross-sectional view illustrating a structure of the press quenching device.

[0021]FIG. 6 is a cross-sectional view illustrating a positioning jig of the press quenching device.

[0022]FIG. 7(a) is a cross-sectional view illustrating an unrestraint state of the press quenching device. FIG. 7(b) is a cross-sectional view illustrating a restraint state of the press quenching device.

[0023]FIG. 8 is a flowchart of the quenching method of the present disclosure.

[0024]FIG. 9 is a schematic view illustrating main steps of the quenching method.

[0025]FIG. 10(a) is a view illustrating a mode of a step of putting a plurality of workpieces together with a conveyance jig into a heating furnace. FIG. 10(b) is a view illustrating a mode of a step of disposing the positioning jig in the coolant with which a cooling tank is filled.

[0026]FIG. 11 is a view illustrating a mode of a step of moving, above the coolant, the conveyance jig on which the plurality of workpieces are arranged, after the conveyance jig is taken out from the heating furnace.

[0027]FIG. 12 is a view illustrating a mode of a step of arranging the plurality of workpieces on the positioning jig.

[0028]FIG. 13 is a view illustrating a mode after the conveyance jig is removed from the workpieces.

[0029]FIG. 14 is a view illustrating a mode of a step of moving a restraint jig above the coolant.

[0030]FIG. 15 is a view illustrating a mode of a step of disposing the restraint jig around the workpieces.

[0031]FIG. 16 is a view illustrating a mode of a step of disposing a second positioning jig in the coolant with which the cooling tank is filled.

[0032]FIG. 17 is a view illustrating a mode of a step of seating a plurality of workpieces on the second positioning jig.

[0033]FIG. 18 is a view illustrating a mode after a second conveyance jig is removed from the workpieces.

[0034]FIG. 19 is a view illustrating a mode of a step of moving a second restraint jig above the coolant.

[0035]FIG. 20 is a view illustrating a mode of a step of disposing a push unit.

[0036]FIG. 21 is a view illustrating a mode of a step of performing press quenching.

[0037]FIG. 22 is a flowchart of a quenching method of Modification Example 1.

[0038]FIG. 23 is a flowchart of a quenching method of Modification Example 2.

[0039]FIG. 24 is a view illustrating a modification example of the positioning jig.

[0040]FIGS. 25(a), 25(b), and 25(c) illustrate workpieces that can be quenched by the quenching methods and the press quenching device.

DESCRIPTION OF EMBODIMENTS

[0041]Hereinafter, embodiments of a quenching method and a restraint quenching device of the present disclosure will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and the redundant description thereof will be omitted.

[0042]FIG. 1 is a schematic view illustrating a quenching facility to which a press quenching device 1 (restraint quenching device) is applied. A workpiece 600 is a component of a bearing. For example, the workpiece 600 is used in a needle thrust bearing, a needle shell bearing, a thin-walled bearing, a large-diameter bearing, and the like. The press quenching device 1 restrains a plurality of workpieces 600 in a coolant 504s.

[0043]The plurality of workpieces 600 are conveyed by a conveyance jig 501. The conveyance jig 501 is connected to a moving mechanism 502. The moving mechanism 502 moves the conveyance jig 501 from a heating furnace 503 to a cooling tank 504. In the quenching facility, batch processing of a substantial number of workpieces 600 is performed.

<Quenching Target Object>

[0044]As illustrated in FIGS. 2 and 3, the workpiece 600 includes a disc-shaped lace 601 (disc-shaped area) and a cylindrical lip 602. The shape of the workpiece 600 is not limited to that illustrated in FIGS. 2 and 3. Some other shapes of the workpiece 600 will be exemplified in the following modification examples.

[0045]The lace 601 is a thin plate having a thickness smaller than an outer diameter thereof. When the workpiece 600 is heated to 750° C. to 900° C. and then the workpiece 600 is immersed in the coolant 504s, a front surface of the workpiece 600 in contact with the coolant 504s is rapidly cooled. As a result, heat sequentially moves from an inside of the workpiece 600 to the front surface of the workpiece 600. Strictly speaking, there is a difference in cooling mode between the front surface and the inside of the workpiece 600. However, the thickness of the workpiece 600 exemplified in the present disclosure is thin. Hence, it can be considered that there is substantially no difference in cooling mode between the front surface and the inside of the workpiece 600. A “thin plate” described in the present disclosure means a plate that can be regarded as having substantially no difference in cooling mode between the front surface and the inside at the time of cooling.

[0046]The lace 601 has a lace principal surface 601a, a lace back surface 601b, and a lace through-hole 601h. The lace principal surface 601a is a flat surface without substantial unevenness. A lip 602 is provided on the lace back surface 601b. The lip 602 extends from the lace back surface 601b in a normal direction of the lace back surface 601b. The lace 601 and the lip 602 are press-molded from a single plate material. Hence, there is no physical boundary between the lace 601 and the lip 602.

[0047]A central axis of the lip 602 coincides with a central axis of the lace 601. The lip 602 and the lace 601 are coaxially disposed. The lip 602 has a lip proximal end 602a, a lip distal end 602b, and a lip through-hole 602h. The lip proximal end 602a is connected to the lace back surface 601b. The lip distal end 602b is a free end. A height of the lip 602 may be smaller than an outer shape of the lip 602. The lip through-hole 602h forms a workpiece through-hole 600h, together with the lace through-hole 601h. An inner diameter of the lip through-hole 602h is the same as an inner diameter of the lace through-hole 601h.

[0048]A result of quenching can be evaluated from, for example, warpage of the lace 601 and roundness of the lip 602. When a state of quenching is not uniform, the warpage of the lace 601 may occur. When a state of quenching is not uniform, the roundness of the lip 602 may be degraded.

<Mechanism of Quenching>

[0049]The cooling of the workpiece 600 will be described in more detail with reference to FIG. 4. In order to generate a desired metal texture such as martensite in the workpiece 600, a cooling rate is important. Specifically, in a case where a cooling rate when the workpiece 600 is immersed in the coolant 504s is lower than a reference cooling rate determined based on experimental results or the like, another metal texture such as pearlite is generated in addition to martensite. Hence, the cooling rate of the workpiece 600 does not need to be lower than the reference cooling rate.

[0050]FIG. 4(a) is a graph illustrating a temperature change of the workpiece 600 which occurs when the workpiece 600 is immersed in the coolant 504s. A graph G4a illustrates a temperature change of a lower portion (position B1) of the lace 601 in the workpiece 600 illustrated in FIG. 4(b). A graph G4d represents a first cooling reference line. In a case where temperature history at the time of cooling the workpiece 600 is present in a range on the left side of the graph G4d, martensite is formed.

[0051]Attention is attracted to the graph G4a. Immediately after the workpiece 600 is immersed in the coolant 504s, a vapor film V1 is generated on the front surface of the workpiece 600 (see FIG. 4(b)). The vapor film V1 has a heat insulating effect. Hence, the vapor film V1 prevents heat transfer from the workpiece 600 to the coolant 504s. As a result, a temperature of the workpiece 600 gradually decreases (a period T4a: a period in which the vapor film is present). Thereafter, the vapor film V1 starts peeling off from the front surface of the workpiece 600 due to some causes (see FIG. 4(c)). At a moment when the peeling is started, the front surface of the workpiece 600 comes into direct contact with the coolant 504s. A phenomenon in which the vapor film V1 is separated from the front surface of the workpiece 600 may be referred to as boiling. The vapor film V1 separated from the workpiece 600 may be referred to as foam V2. When the workpiece 600 comes into direct contact with the coolant 504s, the temperature of the workpiece 600 rapidly decreases (a period T4b: a rapid cooling period). A period in which the temperature of the workpiece 600 rapidly decreases may be referred to as a boiling period. After the temperature of the workpiece 600 decreases to a predetermined value, the temperature of the workpiece 600 decreases slowly (a period T4c: a slow cooling period). For example, during the slow cooling period, the vapor film V1 is not present on the front surface of workpiece 600. The workpiece 600 is in direct contact with the coolant 504s.

<Press Quenching Device>

[0052]Hereinafter, the press quenching device 1 will be described. As illustrated in FIG. 5, the press quenching device 1 includes a first restraint unit 2A, a second restraint unit 2B, and a push unit 3 (push mechanism). The first restraint unit 2A, the second restraint unit 2B, and the push unit 3 are used integrally when restraining the workpiece 600, but are not mechanically connected. For example, when the workpieces 600 are loaded in the press quenching device 1, the first restraint unit 2A, the second restraint unit 2B, and the push unit 3 are in a disassembled state to be respective independent components.

[0053]The first restraint unit 2A will be described. A configuration and an operation of the second restraint unit 2B are the same as a configuration and an operation of the first restraint unit 2A. Hence, the first restraint unit 2A will be described in detail, and the detailed description of the second restraint unit 2B will be omitted. In a case where there is no need to distinguish the first restraint unit 2A and the second restraint unit 2B, the first restraint unit 2A and the second restraint unit 2B are simply referred to as the “restraint unit 2”.

[0054]The restraint unit 2 curbs deformation of the workpieces 600. The restraint unit 2 curbs the occurrence of unintended deformation of the workpieces 600 that may occur at the time of quenching. In the present disclosure, an operation for curbing the occurrence of unintended deformation of the workpieces 600 is referred to as “restraining”. As will be described below, a function of simply maintaining positions of the workpieces 600 is not included in “restraining”.

[0055]The restraint unit 2 includes a positioning jig 21 (positioning member) and a restraint jig 22.

[0056]The positioning jig 21 positions the workpiece 600. Specifically, the positioning jig 21 maintains the plurality of workpieces 600 at predetermined intervals. The positioning jig 21 has a function of maintaining the positions of the workpieces 600. However, the positioning jig 21 does not have a function of restraining deformation of the workpieces 600. The positioning jig 21 is, for example, a plate member having a rectangular shape in plan view.

[0057]As illustrated in FIG. 6, the positioning jig 21 has a workpiece arrangement surface 211 on which the workpieces 600 are arranged. The workpiece arrangement surface 211 has a plurality of positioning slits 212. Arrangement intervals of the positioning slits 212 are arrangement intervals of the workpieces 600. One workpiece 600 is inserted into one positioning slit 212. The lace 601 of the workpiece 600 is inserted into the positioning slit 212. A slit width 212t and a depth 212d of the positioning slit 212 may be set to the extent that the inserted workpiece 600 does not fall down.

[0058]As illustrated in FIG. 5 again, the restraint jig 22 restrains the workpieces 600. The restraint jig 22 fulfills a function of curbing the occurrence of deformation of the workpieces 600. The restraint jig 22 includes a plurality of press blocks 221 (a plurality of restraint members), a block connecting portion 222, and a plurality of springs 223.

[0059]The plurality of press blocks 221 are connected to the block connecting portion 222. The plurality of press blocks 221 are individually arranged at intervals along a predetermined axial line (X axis). The X axis coincides with a direction of a center axial line A of the workpiece through-hole 600h. The plurality of press blocks 221 can individually reciprocate with respect to the block connecting portion 222 along the X axis.

[0060]As illustrated in FIGS. 7(a) and 7(b), the press block 221 has a block principal surface 221s, a block back surface 221b, a block connection surface 221c, and a block free surface 221f.

[0061]The block principal surface 221s is in contact with a workpiece principal surface of the workpiece 600. The block principal surface 221s has a shape suitable for the workpiece principal surface. In the present disclosure, the workpiece principal surface is a flat lace principal surface 601a. Hence, the block principal surface 221s is also a flat surface. The block back surface 221b is in contact with a workpiece back surface of the workpiece 600. The block back surface 221b has a shape suitable for the workpiece back surface. In the present disclosure, the workpiece back surface has a flat lace back surface 601b and a lip 602 projecting from the lace back surface 601b. Hence, the block back surface 221b has a flat surface portion 221p in contact with the lace back surface 601b and a hole portion 221h which receives the lip 602. The shapes of the block principal surface 221s and the block back surface 221b may be changed depending on the shape of the workpiece 600, as appropriate.

[0062]The block connection surface 221c is connected to the block connecting portion 222. The block free surface 221f is a portion in contact with the positioning jig 21. The block free surface 221f is not fixed to the positioning jig 21. The restraint jig 22 is not fixed to the positioning jig 21.

[0063]One or a plurality of springs 223 are disposed between the press blocks 221 adjacent to each other. FIGS. 5 and 7 illustrate a structure in which two springs 223 are disposed between the press blocks 221 adjacent to each other. However, the number of springs 223 is not limited to two. A first end portion of the spring 223 is inserted into a spring hole 221e provided in the block principal surface 221s of the press block 221. A second end portion of the spring 223 is inserted into a spring hole 221e provided in the block back surface 221b of the press block 221.

[0064]A natural length of the spring 223 defines an interval between the press blocks 221 adjacent to each other. The natural length of the spring 223 is longer than at least a width of the workpiece 600 disposed on the positioning jig 21. Specifically, the natural length of the spring 223 is longer than a height of the lip 602 of the workpiece 600.

[0065]The spring 223 can contract to have a length shorter than a distance from a bottom surface of a spring hole 221e of a first press block 221 to a bottom surface of a spring hole 221e of a second press block 221 adjacent to the first press block 221. The press blocks 221 can be in contact with an adjacent press block 221.

[0066]The spring 223 is a compression spring. The spring 223 contracts by a force that the restraint unit 2 receives from the push unit 3. When the force that the restraint unit 2 receives from the push unit 3 is released, the spring 223 returns to have the natural length by the restoring force. The spring 223 contributes to switching from a restraint state illustrated in FIG. 7(b) to an unrestraint state illustrated in FIG. 7(a).

[0067]As illustrated in FIG. 5 again, the push unit 3 includes a first push block pair 31A, a second push block pair 31B, a first push plate 32, and a second push plate 33.

[0068]The first push block pair 31A corresponds to the first restraint unit 2A. The first push block pair 31A includes two push blocks 311 and 312. The push block 311 pushes the press block 221 disposed at the rightmost end of the first restraint unit 2A. The push block 311 has an abutting surface 311s that is abutted on the press block 221. The abutting surface 311s is not fixed to the press block 221. A surface opposite to the abutting surface 311s is fixed to the first push plate 32.

[0069]The push block 312 pushes the press block 221 disposed on the leftmost side of the first restraint unit 2A. The push block 312 also has an abutting surface 312s that is abutted on the press block 221. The abutting surface 312s is also not fixed to the press block 221. A surface opposite to the abutting surface 312s is fixed to the second push plate 33.

[0070]The second push block pair 31B corresponds to the second restraint unit 2B. Since a specific configuration of the second push block pair 31B is the same as that of the first push block pair 31A, the detailed description thereof is omitted.

[0071]Two push blocks 311 are attached to the first push plate 32. Two push blocks 312 are attached to the second push plate 33. The first push plate 32 and the second push plate 33 receive respective forces from an actuator 4 driven by hydraulic pressure, pneumatic pressure, or the like. The first push plate 32 and the second push plate 33 transmit the forces received from the actuator 4 to the push blocks 311 and 312.

[0072]An unrestraint mode and a restraint mode realized by the restraint unit 2 will be described. The restraint unit 2 can switch between the unrestraint mode and the restraint mode. FIG. 7(a) illustrates the unrestraint mode. In the unrestraint state, the restraint unit 2 receives no force from the push unit 3. Hence, the spring 223 has a natural length 223L. An interval between the press blocks 221 adjacent to each other is determined depending on the natural length 223L of the spring 223. An interval 221L between the press blocks 221 adjacent to each other is longer than a height 600L of the workpiece 600.

[0073]FIG. 7(b) illustrates the restraint mode. In the restraint state, the restraint unit 2 receives a force generated by the actuator 4. The block principal surface 221s is abutted on the lace principal surface 601a. The flat surface portion 221p of the block back surface 221b is abutted on the lace back surface 601b. Since the lace 601 receives forces from both the surfaces thereof, the lace is in a restrained state. In the restrained state, deformation due to an increase in thickness of the lace 601 is not allowed. In the restrained state, deformation such as distortion of the lace 601 in a thickness direction (X-axis direction) is not allowed. An outer circumferential surface 602s of the lip 602 is in contact with an inner circumferential surface 221q of the hole portion 221h of the block back surface 221b. In this state, expansion and deformation of the lip 602 is curbed. The hole portion 221h of the block back surface 221b restrains the lip 602 so that an outer diameter of the lip 602 does not become larger than a predetermined value.

[0074]Hence, deformation of the lace 601 is restricted in the restraint state. As a result, in this state, deterioration in flatness of the lace 601 is curbed. In the restraint state, deformation of the lip 602 is restricted. As a result, in this state, deterioration of roundness of the lip 602 is curbed.

[0075]The press quenching device 1 can restrain the plurality of workpieces 600 by a single push operation. The press quenching device 1 can perform so-called batch processing of collectively processing the plurality of workpieces 600.

<Quenching Method>

[0076]A quenching method using the press quenching device 1 will be described with reference to the flowchart illustrated in FIG. 8 and FIGS. 9 to 21.

[0077]As illustrated in FIG. 9, the quenching method includes a step of heating the workpiece 600 by the heating furnace 503 (step S13), a step of conveying the workpiece 600 (step S22), a step of cooling the workpiece 600 by the cooling tank 504 (steps S23 to S31), and a step of preparing the next workpiece 600.

[0078]The workpieces 600 are arranged on first to N-th conveyance jigs 501 (step S11). Here, N represents a plurality of integers. The conveyance jig 501 is a round bar. A diameter of the conveyance jig 501 is substantially the same as or slightly smaller than an inner diameter of the workpiece through-hole 600h. A step is provided on an outer circumferential surface of the conveyance jig 501. Positions of the workpieces 600 are determined by this step. Determining the positions of the workpieces 600 means defining intervals between the workpieces 600 adjacent to each other. The conveyance jig 501 may employ, for example, a steel material having a carbon content of about 0.7 percent or more and 1.2 percent or less.

[0079]Next, the plurality of workpieces 600 are put together with the first to N-th conveyance jigs 501 in the heating furnace 503 (step S12, see FIG. 10(a)). Subsequently, the plurality of workpieces 600 are heated together with the first to N-th conveyance jigs 501 (step S13, see FIG. 10(a)). An inside of a heating chamber of the heating furnace 503 can be set to the vacuum. Hence, the workpieces 600 are arranged under a vacuum environment at a predetermined temperature for a predetermined time. As an example, the workpieces 600 are heated to a temperature between 750° C. and 900° C. A temperature between 750° C. and 900° C. is maintained for about 5 minutes to 30 minutes.

[0080]Next, a first positioning jig 21 is disposed in the coolant 504s with which the cooling tank 504 is filled (step S21, see FIG. 10(b)). Subsequently, the first conveyance jig 501 on which the plurality of workpieces 600 are arranged is taken out from the heating furnace 503. Subsequently, the first conveyance jig 501 is moved above the coolant 504s (step S22, see FIG. 11). Subsequently, the plurality of workpieces 600 are sunk together with the first conveyance jigs 501 in the coolant 504s (step S23). When the workpieces 600 in a high temperature state are brought into contact with the coolant 504s, the vapor film V1 is generated on the front surface of the workpiece 600. Subsequently, the first positioning jig 501 on which the plurality of workpieces 600 are arranged is further sunk, and thereby the plurality of workpieces 600 are arranged on the first positioning jig 21 (step S24, see FIG. 12). The plurality of workpieces 600 are inserted into the plurality of positioning slits 212, respectively. A state in which the plurality of workpieces 600 are arranged on the first positioning jig 21 is referred to as “seating”.

[0081]Next, the first conveyance jig 501 is removed from the workpieces 600 (step S25, see FIG. 13). A mechanism for removing the first conveyance jig 501 is not particularly limited. Since the plurality of workpieces 600 are seated on the first positioning jig 21, a standing state thereof is maintained even when the first conveyance jig 501 is removed. Even after step S25 is completed, the vapor films V1 are present on the respective front surfaces of the workpieces 600.

[0082]Next, a first restraint jig 22 is moved above the coolant 504s (step S26, see FIG. 14). A mechanism 505 (see FIG. 1) for moving the first restraint jig 22 is not particularly limited. Even after step S26 is completed, the vapor films V1 are present on the respective front surfaces of the workpieces 600.

[0083]Next, the first restraint jig 22 is disposed around the workpieces 600 (step S27, see FIG. 15). Specifically, the first restraint jig 22 is sunk in the coolant 504s until the block free surfaces 221f in the first restraint jig 22 come into contact with the workpiece arrangement surface 211 of the first positioning jig 21. As a result, in this state, one workpiece 600 is disposed between the press blocks 221 adjacent to each other. Even after step S27 is completed, the vapor films V1 are present on the respective front surfaces of the workpieces 600.

[0084]Steps 21 to 27 described above are repeated as many times as the number of the conveyance jigs 501. For example, a second positioning jig 21 is disposed in the coolant 504s with which the cooling tank 504 is filled (step S21, see FIG. 16). Subsequently, a second conveyance jig 501 on which the plurality of workpieces 600 are arranged is taken out from the heating furnace 503. Subsequently, the second conveyance jig 501 is moved above the coolant 504s (step 22). Subsequently, the plurality of workpieces 600 are sunk together with the second positioning jig 501 in the coolant 504s, and thereby the plurality of workpieces 600 are seated on the second positioning jig 21 (step S24, see FIG. 17). Next, the second conveyance jig 501 is removed from the workpieces 600 (step S25, see FIG. 18). Next, a second restraint jig 22 is moved above the coolant 504s (step S26, see FIG. 19). Next, the second restraint jig 22 is disposed around the workpieces 600 (step S27).

[0085]Every time steps S21 to S27 are repeated, determination of whether or not all the workpieces 600 are arranged may be implemented (step S28). In a case where the workpieces 600 still remain in the heating furnace 503 (step S28: NO), steps S21 to S27 are performed again. In a case where the workpieces 600 do not remain in the heating furnace 503 (step S28: YES), it can be determined that the arrangement of all the workpieces 600 has been completed.

[0086]Next, the push unit 3 is disposed (step S31, see FIG. 20). Subsequently, press quenching is performed (step S32, see FIG. 21). The press quenching device 1 is switched from the unrestraint state to the restraint state. Specifically, the push unit 3 applies a force to the first restraint unit 2A and the second restraint unit 2B. The intervals between the press blocks 221 adjacent to each other are gradually narrowed. Meanwhile, the lips 602 are inserted into the respective hole portions 221h. In this state, the lips 602 are supported by the respective hole portions 221h. Hence, lower ends of the workpieces 600 do not need to be supported by the positioning jigs 21. As a result, the positioning jigs 21 can be removed from the lower ends of the laces 601. In this state, the workpieces 600 are not restrained in a push direction. Hence, as the intervals between the press blocks 221 are narrowed, the intervals between the workpieces 600 are also narrowed. The block principal surfaces 221s are in contact with the lace principal surfaces 601a. The block back surfaces 221b are in contact with the lace back surfaces 601b. More specifically, the block principal surfaces 221s and the block back surfaces 221b are abutted on the lace principal surfaces 601a and the lace back surfaces 601b by a force which can resist a force due to the deformation of the lace 601 (see FIG. 7(b)).

[0087]In the unrestraint state, the vapor films V1 are present on the respective front surfaces of workpieces 600 (see FIG. 20). In the restraint state, the press blocks 221 are in direct contact with the workpieces 600. The unrestraint state is maintained during a first period (T4a) in which the temperature gradually decreases as illustrated in a graph G4a of FIG. 4. While the unrestraint state is switched to the restraint state, the vapor films V1 are separated from the front surfaces of the workpieces 600. In other words, rapid cooling of the workpiece 600 is started. The restraint state is maintained during a second period (T4b) in which the temperature rapidly decreases as illustrated in the graph G4a of FIG. 4. In the present disclosure, a period from a timing when the workpieces 600 are immersed in the coolant 504s to a timing when the vapor films V1 start peeling off from the front surfaces of the workpieces 600 is not regarded as a rapid cooling period for quenching. In the present disclosure, the timing at which the vapor films V1 start peeling off is considered as a time when rapid cooling is started (a time when a quenching treatment is started). There may be a mode in which the heat of the workpiece 600 moves to the coolant 504s by direct contact between the workpiece 600 and the coolant 504s, and a mode in which the heat of the workpiece 600 moves to the press block 221 by direct contact between the workpiece 600 and the press block 221.

[0088]The vapor film V1 is unstably present. Hence, the vapor film V1 may be separated over time regardless of the closeness of the press block 221. When the vapor film V1 is separated, rapid cooling is started. The press quenching device 1 curbs deformation of the workpiece 600 which occurs at the time of rapid cooling. Hence, the switching from the unrestraint state to the restraint state needs to be completed before the rapid cooling is started. For example, a period from when the workpieces 600 are sunk in the coolant 504s to when the vapor films V1 naturally start peeling off is about several seconds (about 3 seconds to 7 seconds). Hence, all the steps from step S21 to step S32 are completed within this period of several seconds.

[0089]Next, a load is removed (step S33). The press quenching device 1 is switched from the restraint state to the unrestraint state. Subsequently, the workpieces 600 are sequentially taken out together with the positioning jig 21 from the coolant 504s (step S34). The workpieces 600 are taken out from the positioning jig 21 (step S35). Through the above steps, quenching of the plurality of workpieces 600 is completed.

[0090]Operations and effects of the press quenching device 1 and the quenching method of the present disclosure will be described.

[0091]The quenching method of the present disclosure is provided for the workpieces 600 including the respective laces 601 and having the respective workpiece through-holes 600h. The quenching method includes the step of preparing the press quenching device 1 capable of switching between the restraint state in which workpieces 600 are restrained and an unrestraint state in which the workpieces are not restrained, the step of arranging the plurality of heated workpieces 600 in the press quenching device 1 that is in the unrestraint state, the step of restraining the restraint target areas of the workpieces 600 by the press quenching device 1 by causing the press quenching device 1 to switch from the unrestraint state to the restraint state, and the step of cooling the restrained workpieces 600.

[0092]In the quenching method of the present disclosure, the plurality of workpieces 600 arranged in a predetermined mode are restrained, and then the workpieces 600 in the restraint state start to be cooled. The “start of cooling” means that the vapor films V1 start peeling off. Hence, the plurality of workpieces 600 can be subjected to press quenching. Since the workpieces 600 obtained by performing the press quenching are curbed from being deformed due to the heat treatment, it is possible to curb generation of a defective product which does not satisfy requirements for accuracy of the shape. The quenching method of the present disclosure can curb deformation of the workpieces 600 due to the heat treatment, thus being capable of curbing generation of a defective product. It is possible to improve the yield in a case where the plurality of workpieces 600 are subjected to the heat treatment at a time.

[0093]The quenching method further includes the step of immersing the plurality of workpieces 600 in the coolant 504s before the step of the restraining. The step of the restraining and the step of the cooling are performed in the state in which the workpieces 600 are immersed in the coolant 504s. These steps enable the high-temperature workpieces 600 to be quickly cooled by the coolant 504s.

[0094]The step of the arranging includes the step of arranging the plurality of workpieces 600 on the positioning jig 21 of the press quenching device 1, and the step of arranging the plurality of restraint jigs 22 of the press quenching device 1 individually between the plurality of workpieces 600. These steps enable the plurality of workpieces 600 to be subjected to the press quenching.

[0095]In the step of the arranging, the plurality of workpieces 600 are arranged on the positioning jig 21 along the axial lines of the through-holes of the workpieces 600. This step enables the plurality of workpieces 600 to be restrained by a simple operation.

[0096]in the step of the restraining, the first restraint jig 22 is abutted on, as a restraint target area, a lace principal surface 601a in the lace 601 of the workpiece 600, and the second restraint jig 22 is abutted on the lace back surface 601b in the lace 601. This step enables deformation of the lace 601 of the workpiece 600 to be curbed.

[0097]The press quenching device 1 is provided for the workpieces 600 including the respective laces 601 and having the respective workpiece through-holes 600h. The press quenching device 1 includes the positioning jig 21 configured to maintain the positions and postures of the plurality of the workpieces 600, the plurality of press blocks 221 that come into contact with restraint target areas of the workpieces 600, and the push unit 3 configured to push the press blocks 221 toward the restraint target areas. The press blocks 221 and the push unit 3 switch between the restraint state in which the workpieces 600 are restrained and the unrestraint state in which the workpieces 600 are not restrained. This device also enables the plurality of workpieces 600 to be subjected to the press quenching.

[0098]The quenching method and the restraint quenching device of the present disclosure are not limited to the above-described embodiments.

Modification Example 1

[0099]In the quenching method of the present disclosure, the rapid cooling of the workpieces 600 is performed in the coolant 504s. In the quenching treatment, the workpieces 600 do not need to be sunk in the coolant 504s as long as the workpieces can be cooled depending on a predetermined cooling rate. For example, when the press blocks 221 have a sufficiently large heat capacity, the quenching can be performed without sinking the workpieces in the coolant 504s.

[0100]FIG. 22 is a flowchart of a quenching method according to Modification Example 1. In the quenching method of Modification Example 1, the quenching treatment is performed without using the coolant 504s. A press quenching device 1 used in the quenching method of Modification Example 1 is the same as the press quenching device 1 used in the quenching method of the present disclosure.

[0101]The plurality of workpieces 600 are subjected to the heat treatment. Steps S11, S12, and S13 for the heating treatment of Modification Example 1 are the same as steps S11, S12, and S13 of the present disclosure.

[0102]Next, an n-th positioning jig 21 is disposed (step S21A). In the quenching method of the present disclosure, the nth positioning jig 21 is disposed in the coolant 504s. In the quenching method of Modification Example 1, the n-th positioning jig 21 is disposed in the atmosphere. The n-th positioning jig 21 is not sunk in the coolant 504s. Subsequently, the plurality of workpieces 600 are arranged on the n-th positioning jig 21 (step S24A). The workpieces 600 are arranged on the n-th positioning jig 21 in the atmosphere. In the quenching method of Modification Example 1, the moving of the plurality of workpieces 600 above the coolant 504s (step S22) and the sinking of the plurality of workpieces 600 in the coolant 504s (step S23) performed in the embodiments are not performed.

[0103]Next, an n-th conveyance jig 501 is removed from the plurality of workpieces 600 (step S25A). Subsequently, an n-th restraint jig 22 is moved and disposed around the workpieces 600 (steps S26A and S27A). After the arrangement of all the workpieces 600 is completed (step S28: YES), the push unit 3 is disposed (step S31A). The press quenching is performed (step S32A). Thereafter, a load is removed (step S33A), and then the workpieces 600 are taken out from the positioning jig 21 (step S35A).

[0104]The restraining steps (steps S21A to S28) and a cooling step (step S32A) of the quenching method of Modification Example 1 are performed in a state in which the workpieces 600 are not immersed in the coolant 504s. This step enables a time from the arrangement to the restraint to be ensured. The quenching method of Modification Example 1 also enables the plurality of workpieces 600 to be subjected to the press quenching at a time.

Modification Example 2

[0105]In the quenching method of Modification Example 1, the rapid cooling of the workpieces 600 is performed in the atmosphere. For example, the rapid cooling of the workpieces 600 may be performed in the atmosphere and the coolant 504s. FIG. 23 is a flowchart of a quenching method of Modification Example 2. In the quenching method of Modification Example 2, first, switching from the unrestraint state to the restraint state is performed in the atmosphere. Next, after a predetermined time has elapsed, the press quenching device 1 in the restraint state is sunk in the coolant 504s.

[0106]As illustrated in FIG. 23, steps S11, S12, and S13 for the heat treatment are performed. Subsequently, steps S21B to S27B for preparation of press quenching in the atmosphere are performed. Steps S21B to S27B are the same as steps S21A to S27A of Modification Example 1.

[0107]Next, after the push unit 3 is disposed (step S31B), the press quenching is performed (step S32B1). The press quenching device 1 is switched from the unrestraint state to the restraint state. Next, after a predetermined time has elapsed after the switching to the restraint state is performed, the press quenching device 1 in the restraint state is sunk in the coolant 504s (step S32B2). Subsequently, after a load is removed (step S33B), the workpieces 600 are taken out from the coolant 504s (step S34B). The workpieces 600 are taken out from the press quenching device 1 (step S35B).

[0108]The quenching method of Modification Example 2 further includes, after the restraining step (step S32B1), the step (step S32B2) of immersing the workpieces 600 arranged in the press quenching device 1 in the coolant 504s. The restraining step (step S32B1) is performed in a state in which the workpieces 600 are not immersed in the coolant 504s. A cooling step has a first period (step S32B1) in which cooling is performed in the state in which the workpieces 600 are not immersed in the coolant 504s. The cooling step has, following the first period, a second period (step S32B2) in which the cooling is performed in a state in which the workpieces 600 are immersed in the coolant 504s. This step enables a time from the arrangement to the restraint to be ensured. In addition, the quenching method of Modification Example 2 also enables the plurality of workpieces 600 to be subjected to the press quenching at a time.

[0109]According to the quenching method of Modification Example 2, even in a case where the heat capacity of the press block 221 is not sufficiently large, the workpieces 600 can be sufficiently cooled because the workpieces are immersed in the coolant 504s (step S32B2). Even with a small press block 221 having a relatively small heat capacity, the plurality of workpieces 600 can be subjected to the press quenching at a time.

<Modification Example of Positioning Jig>

[0110]The positioning jig can employ a configuration illustrated in FIG. 24. FIG. 24 illustrates a positioning jig including a pair of prismatic members 21A. The prismatic member 21A has a plurality of positioning slits arranged to be separated from each other in a longitudinal direction. Such a configuration also enables the plurality of workpieces 600 to be held.

<Exemplification of Quenching Target Object>

[0111]A workpiece 600A illustrated in FIG. 25(a) includes a lace 601A and a lip 602A. A lace through-hole 601h is formed in the lace 601A. The lip 602A stands from an outer circumferential edge of the lace 601A. The lip 602A extends linearly from the lace 601A. The lip 602A does not have a folded portion between a portion connected to the lace 601A and a distal end.

[0112]A workpiece 600B illustrated in FIG. 25(b) includes a lace 601B and a lip 602B. A lace through-hole 601h is formed in the lace 601B. The lip 602B stands from an outer circumferential edge of the lace 601B. The lip 602B has a curl portion 603 between a portion connected to the lace 601B and a distal end. The lip 602B is bent inward from the curl portion 603 as a starting point. An inner diameter of a distal end portion of the lip 602B is smaller than an outer diameter of the lace 601B.

[0113]A workpiece 600C illustrated in FIG. 25(c) includes a lace 601C, an inner lip 604C, and an outer lip 602C. The inner lip 604C forms a workpiece through-hole 600h, together with a lace through-hole 601h provided in the lace 601C. The outer lip 602C stands from an outer circumferential edge of the lace 601C. A direction in which the outer lip 602C stands is the same as a direction in which the inner lip 604C stands. A height of the outer lip 602C may be higher than that of the inner lip 604C.

REFERENCE SIGNS LIST