Quenching Method and Restraint Quenching Device

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

is a schematic view illustrating a quenching facility to which a press quenching device(restraint quenching device) is applied. A workpieceis a component of a bearing. For example, the workpieceis used in a needle thrust bearing, a needle shell bearing, a thin-walled bearing, a large-diameter bearing, and the like. The press quenching devicerestrains a plurality of workpiecesin a coolant

The plurality of workpiecesare conveyed by a conveyance jig. The conveyance jigis connected to a moving mechanism. The moving mechanismmoves the conveyance jigfrom a heating furnaceto a cooling tank. In the quenching facility, batch processing of a substantial number of workpiecesis performed.

As illustrated in, the workpieceincludes a disc-shaped lace(disc-shaped area) and a cylindrical lip. The shape of the workpieceis not limited to that illustrated in. Some other shapes of the workpiecewill be exemplified in the following modification examples.

The laceis a thin plate having a thickness smaller than an outer diameter thereof. When the workpieceis heated to 750° C. to 900° C. and then the workpieceis immersed in the coolant, a front surface of the workpiecein contact with the coolantis rapidly cooled. As a result, heat sequentially moves from an inside of the workpieceto the front surface of the workpiece. Strictly speaking, there is a difference in cooling mode between the front surface and the inside of the workpiece. However, the thickness of the workpieceexemplified 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. 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.

The lacehas a lace principal surface, a lace back surface, and a lace through-hole. The lace principal surfaceis a flat surface without substantial unevenness. A lipis provided on the lace back surface. The lipextends from the lace back surfacein a normal direction of the lace back surface. The laceand the lipare press-molded from a single plate material. Hence, there is no physical boundary between the laceand the lip.

A central axis of the lipcoincides with a central axis of the lace. The lipand the laceare coaxially disposed. The liphas a lip proximal end, a lip distal end, and a lip through-hole. The lip proximal endis connected to the lace back surface. The lip distal endis a free end. A height of the lipmay be smaller than an outer shape of the lip. The lip through-holeforms a workpiece through-hole, together with the lace through-hole. An inner diameter of the lip through-holeis the same as an inner diameter of the lace through-hole

A result of quenching can be evaluated from, for example, warpage of the laceand roundness of the lip. When a state of quenching is not uniform, the warpage of the lacemay occur. When a state of quenching is not uniform, the roundness of the lipmay be degraded.

The cooling of the workpiecewill be described in more detail with reference to. In order to generate a desired metal texture such as martensite in the workpiece, a cooling rate is important. Specifically, in a case where a cooling rate when the workpieceis immersed in the coolantis 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 workpiecedoes not need to be lower than the reference cooling rate.

is a graph illustrating a temperature change of the workpiecewhich occurs when the workpieceis immersed in the coolant. A graph Gillustrates a temperature change of a lower portion (position B) of the lacein the workpieceillustrated in. A graph Grepresents a first cooling reference line. In a case where temperature history at the time of cooling the workpieceis present in a range on the left side of the graph G, martensite is formed.

Attention is attracted to the graph G. Immediately after the workpieceis immersed in the coolant, a vapor film Vis generated on the front surface of the workpiece(see). The vapor film Vhas a heat insulating effect. Hence, the vapor film Vprevents heat transfer from the workpieceto the coolant. As a result, a temperature of the workpiecegradually decreases (a period T: a period in which the vapor film is present). Thereafter, the vapor film Vstarts peeling off from the front surface of the workpiecedue to some causes (see). At a moment when the peeling is started, the front surface of the workpiececomes into direct contact with the coolant. A phenomenon in which the vapor film Vis separated from the front surface of the workpiecemay be referred to as boiling. The vapor film Vseparated from the workpiecemay be referred to as foam V. When the workpiececomes into direct contact with the coolant, the temperature of the workpiecerapidly decreases (a period T: a rapid cooling period). A period in which the temperature of the workpiecerapidly decreases may be referred to as a boiling period. After the temperature of the workpiecedecreases to a predetermined value, the temperature of the workpiecedecreases slowly (a period T: a slow cooling period). For example, during the slow cooling period, the vapor film Vis not present on the front surface of workpiece. The workpieceis in direct contact with the coolant

Hereinafter, the press quenching devicewill be described. As illustrated in, the press quenching deviceincludes a first restraint unitA, a second restraint unitB, and a push unit(push mechanism). The first restraint unitA, the second restraint unitB, and the push unitare used integrally when restraining the workpiece, but are not mechanically connected. For example, when the workpiecesare loaded in the press quenching device, the first restraint unitA, the second restraint unitB, and the push unitare in a disassembled state to be respective independent components.

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

The restraint unitcurbs deformation of the workpieces. The restraint unitcurbs the occurrence of unintended deformation of the workpiecesthat may occur at the time of quenching. In the present disclosure, an operation for curbing the occurrence of unintended deformation of the workpiecesis referred to as “restraining”. As will be described below, a function of simply maintaining positions of the workpiecesis not included in “restraining”.

The restraint unitincludes a positioning jig(positioning member) and a restraint jig.

The positioning jigpositions the workpiece. Specifically, the positioning jigmaintains the plurality of workpiecesat predetermined intervals. The positioning jighas a function of maintaining the positions of the workpieces. However, the positioning jigdoes not have a function of restraining deformation of the workpieces. The positioning jigis, for example, a plate member having a rectangular shape in plan view.

As illustrated in, the positioning jighas a workpiece arrangement surfaceon which the workpiecesare arranged. The workpiece arrangement surfacehas a plurality of positioning slits. Arrangement intervals of the positioning slitsare arrangement intervals of the workpieces. One workpieceis inserted into one positioning slit. The laceof the workpieceis inserted into the positioning slit. A slit widthand a depthof the positioning slitmay be set to the extent that the inserted workpiecedoes not fall down.

As illustrated inagain, the restraint jigrestrains the workpieces. The restraint jigfulfills a function of curbing the occurrence of deformation of the workpieces. The restraint jigincludes a plurality of press blocks(a plurality of restraint members), a block connecting portion, and a plurality of springs.

The plurality of press blocksare connected to the block connecting portion. The plurality of press blocksare 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. The plurality of press blockscan individually reciprocate with respect to the block connecting portionalong the X axis.

As illustrated in, the press blockhas a block principal surface, a block back surface, a block connection surface, and a block free surface

The block principal surfaceis in contact with a workpiece principal surface of the workpiece. The block principal surfacehas a shape suitable for the workpiece principal surface. In the present disclosure, the workpiece principal surface is a flat lace principal surface. Hence, the block principal surfaceis also a flat surface. The block back surfaceis in contact with a workpiece back surface of the workpiece. The block back surfacehas a shape suitable for the workpiece back surface. In the present disclosure, the workpiece back surface has a flat lace back surfaceand a lipprojecting from the lace back surface. Hence, the block back surfacehas a flat surface portionin contact with the lace back surfaceand a hole portionwhich receives the lip. The shapes of the block principal surfaceand the block back surfacemay be changed depending on the shape of the workpiece, as appropriate.

The block connection surfaceis connected to the block connecting portion. The block free surfaceis a portion in contact with the positioning jig. The block free surfaceis not fixed to the positioning jig. The restraint jigis not fixed to the positioning jig.

One or a plurality of springsare disposed between the press blocksadjacent to each other.illustrate a structure in which two springsare disposed between the press blocksadjacent to each other. However, the number of springsis not limited to two. A first end portion of the springis inserted into a spring holeprovided in the block principal surfaceof the press block. A second end portion of the springis inserted into a spring holeprovided in the block back surfaceof the press block.

A natural length of the springdefines an interval between the press blocksadjacent to each other. The natural length of the springis longer than at least a width of the workpiecedisposed on the positioning jig. Specifically, the natural length of the springis longer than a height of the lipof the workpiece.

The springcan contract to have a length shorter than a distance from a bottom surface of a spring holeof a first press blockto a bottom surface of a spring holeof a second press blockadjacent to the first press block. The press blockscan be in contact with an adjacent press block.

The springis a compression spring. The springcontracts by a force that the restraint unitreceives from the push unit. When the force that the restraint unitreceives from the push unitis released, the springreturns to have the natural length by the restoring force. The springcontributes to switching from a restraint state illustrated into an unrestraint state illustrated in.

As illustrated inagain, the push unitincludes a first push block pairA, a second push block pairB, a first push plate, and a second push plate.

The first push block pairA corresponds to the first restraint unitA. The first push block pairA includes two push blocksand. The push blockpushes the press blockdisposed at the rightmost end of the first restraint unitA. The push blockhas an abutting surfacethat is abutted on the press block. The abutting surfaceis not fixed to the press block. A surface opposite to the abutting surfaceis fixed to the first push plate.

The push blockpushes the press blockdisposed on the leftmost side of the first restraint unitA. The push blockalso has an abutting surfacethat is abutted on the press block. The abutting surfaceis also not fixed to the press block. A surface opposite to the abutting surfaceis fixed to the second push plate.

The second push block pairB corresponds to the second restraint unitB. Since a specific configuration of the second push block pairB is the same as that of the first push block pairA, the detailed description thereof is omitted.

Two push blocksare attached to the first push plate. Two push blocksare attached to the second push plate. The first push plateand the second push platereceive respective forces from an actuatordriven by hydraulic pressure, pneumatic pressure, or the like. The first push plateand the second push platetransmit the forces received from the actuatorto the push blocksand.

An unrestraint mode and a restraint mode realized by the restraint unitwill be described. The restraint unitcan switch between the unrestraint mode and the restraint mode.illustrates the unrestraint mode. In the unrestraint state, the restraint unitreceives no force from the push unit. Hence, the springhas a natural lengthL. An interval between the press blocksadjacent to each other is determined depending on the natural lengthL of the spring. An intervalL between the press blocksadjacent to each other is longer than a heightL of the workpiece.

illustrates the restraint mode. In the restraint state, the restraint unitreceives a force generated by the actuator. The block principal surfaceis abutted on the lace principal surface. The flat surface portionof the block back surfaceis abutted on the lace back surface. Since the lacereceives 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 laceis not allowed. In the restrained state, deformation such as distortion of the lacein a thickness direction (X-axis direction) is not allowed. An outer circumferential surfaceof the lipis in contact with an inner circumferential surfaceof the hole portionof the block back surface. In this state, expansion and deformation of the lipis curbed. The hole portionof the block back surfacerestrains the lipso that an outer diameter of the lipdoes not become larger than a predetermined value.

Hence, deformation of the laceis restricted in the restraint state. As a result, in this state, deterioration in flatness of the laceis curbed. In the restraint state, deformation of the lipis restricted. As a result, in this state, deterioration of roundness of the lipis curbed.

The press quenching devicecan restrain the plurality of workpiecesby a single push operation. The press quenching devicecan perform so-called batch processing of collectively processing the plurality of workpieces.