Quenching apparatus

Abstract

To provide a quenching apparatus capable of effectively quenching a ridge part on an outer peripheral surface of a rod-like steel material.SOLUTION: A quenching apparatus 1 is used for a rod-like steel material 51 in which a ridge part 52 and a groove part 53 are formed, and quenches the ridge part. The quenching apparatus includes a driving section, a heating section 21 and a cooling section. The driving section rotates the rod-shaped steel material around the center axis CL and advances it to one side in the axial direction. The heating section is configured to sequentially heat a portion 52a to be heated of the ridge part of the rod-shaped steel material, the portion making transition along a direction in which the spiral ridge part extends, in accordance with rotation and advancement of the rod-shaped steel material by the driving section. The cooling section cools the rod-like steel material down and includes a first coolant injection section 32 that injects a coolant toward a heating-completed portion 52b located on a front side of the portion to be heated in a rotation direction of the steel rod, and a second coolant injection section 34 that injects a coolant toward a heating-adjacent portion 53a of the groove part 53 adjacent to the portion to be heated of the ridge in the axial direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a quenching device used for a rod-shaped steel material having ridges and grooves formed on the outer periphery thereof. [Background technology]

[0002] The rod-shaped steel material may be a hollow cylindrical or solid columnar material having spiral ridges and grooves formed on the outer circumferential surface along at least a portion of the axial direction. In such a rod-shaped steel material, the ridges and grooves are alternately positioned adjacent to each other in the axial direction on the outer circumferential surface and are provided in a manner extending spirally around the central axis.

[0003] The screw shaft of a ball screw, which is a specific example of such a rod-shaped steel material, has threads and grooves formed on its outer surface as screw threads and screw grooves, and when used as part of a ball screw, it rotates inside the nut and functions to convert linear motion into rotational motion or rotational motion into linear motion.

[0004] When the rod-shaped steel material described above is used as, for example, a screw shaft of a relatively large ball screw or other feed screw, a large external force may be applied to the crests during use. For this reason, in order to increase the strength and wear resistance of the crests formed on the outer peripheral surface of the rod-shaped steel material, it may be necessary to partially quench or temper the crests by heating and rapid cooling (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 4-13812 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a quenching device that can effectively quench the peaks on the outer peripheral surface of a rod-shaped steel material. [Means for solving the problem]

[0007] The quenching device of this invention is used for rod-shaped steel material having ridges and grooves formed on its outer peripheral surface in at least a portion of the axial direction, extending spirally around a central axis, and quenches the ridges. The quenching device comprises a drive unit that rotates the rod-shaped steel material around the central axis and advances it in one axial direction, a heating unit that sequentially heats the heating target portions of the ridges, which transition along the extending direction of the spiral ridges, as the drive unit rotates and advances the rod-shaped steel material, and a cooling unit that cools the rod-shaped steel material. The cooling unit has a first refrigerant injection unit that injects refrigerant toward a heating completion portion that is located forward of the heating target portion in the rotation direction of the rod-shaped steel material, and a second refrigerant injection unit that injects refrigerant toward a heating-adjacent portion of the groove that is adjacent to the heating target portion of the ridge in the axial direction.

[0008] In the above-described quenching device, it is preferable that the first coolant injection section is provided so that the position and / or the direction of the injection port can be changed.

[0009] In the above-mentioned quenching device, it is preferable that the second refrigerant injection sections are arranged on both the front and rear sides of the direction of travel of the rod-shaped steel material, separated from the heating section in the axial direction, and that each of the second refrigerant injection sections is capable of injecting refrigerant at a flow rate different from each other.

[0010] It is preferable that the above-mentioned quenching device further includes a partition plate arranged between the heating section and the second refrigerant injection section to separate the heated area from the heated adjacent area and to prevent the refrigerant injected from the second refrigerant injection section from flowing toward the heated area.

[0011] In this case, it is preferable that the partition plate is made of resin and is provided at a position where it contacts the surface of the groove portion of the rod-shaped steel material.

[0012] In the above-mentioned quenching device, it is preferable that the injection port of the second refrigerant injection section is positioned and oriented to inject refrigerant toward the heating-adjacent area of ​​the groove section adjacent to the heating target area of ​​the peak section in the axial direction, which is located rearward of the heating section in the rotational direction.

[0013] In the above-described quenching device, it is preferable that the second refrigerant injection section has a plurality of injection ports which inject the refrigerant in different directions.

[0014] In the above-mentioned quenching device, it is preferable that the second refrigerant injection section is provided at least rearward of the heating section in the direction of travel of the rod-shaped steel material, and that the cooling section further has a third refrigerant injection section that is provided further rearward of the second refrigerant injection section in the direction of travel and injects refrigerant onto the rod-shaped steel material.

[0015] In the above-described hardening device, the heating section preferably has an induction heating coil.

[0016] In the above-mentioned hardening device, it is preferable that the drive unit has a rotary drive source that rotates the rod-shaped steel material around the central axis, and a motion conversion mechanism that is fitted into the ridge portion and / or the groove portion of the rod-shaped steel material and converts the rotational motion of the rod-shaped steel material by the rotary drive source into linear motion in the axial direction. [Effects of the Invention]

[0017] According to the above-described quenching device, the peaks on the outer peripheral surface of the rod-shaped steel material can be effectively quenched. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a side view showing a quenching device according to an embodiment of the present invention, with a rod-shaped steel material placed therein; [Figure 2] FIG. 2 is an enlarged side view showing a main part of FIG. 1. [Figure 3]2 is a perspective view showing a heating section and a second refrigerant injection section of a cooling section provided in the quenching device of FIG. 1, and a partition plate disposed between them. FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0019] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The quenching device 1 illustrated in FIG. 1 is used for a rod-shaped steel material 51, and quenches a ridge 52 formed on the outer peripheral surface of the rod-shaped steel material 51.

[0020] The rod-shaped steel material 51 to be hardened by the quenching apparatus 1 is made of a material such as carbon steel and has a solid cylindrical shape in the axial direction (left and right direction in FIG. 1), or a cylindrical or other rod shape with at least a portion of the axial direction being hollow. As shown in FIG. 1, the rod-shaped steel material 51 has ridges 52 and grooves 53 that extend spirally around the central axis CL formed on its outer circumferential surface in at least a portion of the axial direction.

[0021] The illustrated rod-shaped steel material 51 can be used, for example, as a screw shaft for a feed screw such as a ball screw mounted in various manufacturing facilities or machines. The rod-shaped steel material 51 includes a threaded portion 54a having a thread portion 52 and a groove portion 53 formed on its outer circumferential surface, which function as a screw thread and a screw groove, respectively, and a trunk portion 54b integrally formed at one axial end (the right end in FIG. 1 ) of the threaded portion 54a and having a smooth outer circumferential surface without a thread portion or groove. In the threaded portion 54a, groove portions 53 recessed radially inward relative to the position of the outer circumferential surface of the trunk portion 54b are formed in a spiral shape extending from one side to the other in the axial direction while circling around the central axis CL. Between adjacent axial groove portions 53, a thread portion 52 is defined, the crest of which is located at approximately the same radial position as the outer circumferential surface of the trunk portion 54b.

[0022] For example, when a rod-shaped steel material 51 is used as the screw shaft of a relatively large ball screw, a large external force acts on the crests 52 on the outer peripheral surface of the threaded portion 54a each time a nut (not shown) is threaded onto the threaded portion 54a and rotates around the central axis CL while repeatedly moving in the axial direction, which makes the crests 52 prone to damage and wear. In response to this, a quenching device 1 can be used to harden the crests 52 in order to improve the strength and wear resistance of the crests 52. In the quenching device 1 of this embodiment, the crests 52 are hardened, but at least a portion of the crests 52, such as the bottoms of the grooves 53, is not hardened.

[0023] The quenching device 1 generally includes a drive unit 11 that rotates a rod-shaped steel material 51 around a central axis CL and moves it to one side in the axial direction (left side in Figure 1), as shown by the white arrow in Figure 1, a heating unit 21 that heats the peak portion 52 of the rod-shaped steel material 51, and a cooling unit 31 that cools the rod-shaped steel material 51.

[0024] Here, various mechanisms can be employed for the driving unit 11 as long as they drive the rod-shaped steel material 51 to move in the axial direction while rotating it about the central axis CL. In the illustrated embodiment, the driving unit 11 is made up of a rotational driving source 12 that rotates the rod-shaped steel material 51 about the central axis CL, and a motion conversion mechanism 13 that converts the rotational motion of the rod-shaped steel material 51 caused by the rotational driving source 12 into linear motion in the axial direction by utilizing spiral ridges 52 or grooves 53 formed on the outer peripheral surface of the rod-shaped steel material 51.

[0025] More specifically, in this quenching apparatus 1, a plurality of pairs of rotatable support rollers 41 are arranged adjacent to each other with a rod-shaped steel material 51 separated in the depth direction of the paper surface of Fig. 1, and the rod-shaped steel material 51 is placed between the pairs of support rollers 41 and on the support rollers 41. One or more engaging rollers 13a are arranged above the rod-shaped steel material 51 as a motion conversion mechanism 13. As shown in the figure, the engaging rollers 13a are fitted into grooves 53 of the rod-shaped steel material 51 so as to sandwich the rod-shaped steel material 51 between the supporting rollers 41.

[0026] In this state, when the rod-shaped steel material 51 is rotationally driven by the application of a rotational driving force from the rotational driving source 12, the engagement rollers 13a, which are fixed so as not to move in the axial or circumferential directions, roll within the spiral groove 53 in accordance with the rotational motion of the rod-shaped steel material 51. As a result, an external force directed from the engagement rollers 13a to one side in the axial direction acts on the rod-shaped steel material 51, and the rotational motion by the rotational driving source 12 is converted into linear axial motion, causing the rod-shaped steel material 51 to advance to one side in the axial direction. Note that the rotational driving source 12 is provided so as to be movable in the axial direction, and when a rotational driving force is applied to the rod-shaped steel material 51, it moves in the axial direction together with the rod-shaped steel material 51.

[0027] As described above, the illustrated rotary drive source 12 and motion converting mechanism 13 can rotate the rod-shaped steel material 51 around the central axis CL while moving it in one axial direction. In this example, the motion converting mechanism 13 is a fitting roller 13a that fits into the groove 53 of the rod-shaped steel material 51, but it is also possible to convert rotational motion into linear motion by fitting into the ridges 52 in addition to or instead of the grooves 53. Although not shown, the motion converting mechanism 13 may be, for example, a nut that fits into the grooves 53 and / or the ridges 52 around the entire circumference of the rod-shaped steel material 51.

[0028] The drive unit 11 can also have separate drive sources for rotating the rod-shaped steel material 51 and for linearly moving it in the axial direction, but in this case, it is necessary to precisely synchronize the operations of the drive sources. As in the illustrated embodiment, configuring the drive unit 11 with a rotational drive source 12 and a motion conversion mechanism 13 for converting the rotational motion generated by the rotational drive source 12 into linear motion is preferable because it makes effective use of the ridges 52 and grooves 53 formed in the rod-shaped steel material 51 and enables accurate control of the rotation and progress of the rod-shaped steel material by simply adjusting the operation of the rotational drive source 12.

[0029] In the quenching apparatus 1 of this embodiment, the heating section 21 is fixed to a portion of the rod-shaped steel material 51 in the axial direction and to a portion of the circumferential direction (see FIGS. 2 to 4). When the rod-shaped steel material 51 is rotated and moved toward one side in the axial direction by the driving section 11, the movement of the rod-shaped steel material 51 causes each portion of the peak portion 52 of the rod-shaped steel material 51 to pass positions where the heating section 21 is provided in sequence, and as the portions pass, the portions are heated in sequence by the heating section 21. Here, the portion of the peak portion 52 that reaches the position where the heating section 21 is provided and is heated by the heating section 21 is referred to as the heating target portion 52a. The heating target portion 52a moves along the extension direction of the spiral peak portion 52 in accordance with the movement of the rod-shaped steel material 51.

[0030] The heating unit 21 may include an induction heating coil 22 that heats heating target locations 52a of the peaks 52 of the rod-shaped steel material 51 by electromagnetic induction based on the passage of a high-frequency current. Here, as shown in FIGS. 2 to 4 , the induction heating coil 22 has a shape that sandwiches the peaks 52 from both sides in the axial direction at positions slightly spaced apart from the peaks 52 along a portion of the circumferential direction of the rod-shaped steel material 51. More specifically, the induction heating coil 22 includes two U-shaped portions 22a located at one end and the other end of the extension of the peaks 52, rod-shaped portions 22b that are disposed in the grooves 53 adjacent to both sides of the peaks 52 in the axial direction and extend so as to connect the tips of the U-shaped portions, and a connecting portion 22c that connects the two U-shaped portions 22a at their centers at a position away from the peaks 52. Two conductors 23 are connected to one of the U-shaped portions 22a, sandwiching the connecting portion of the connecting portion 22c. However, the induction heating coil 22 is not limited to this specific shape as long as it can heat the heating target portion 52a of the peak portion 52.

[0031] Furthermore, the cooling section 31 provided in the quenching device 1 includes at least a first refrigerant injection section 32 and a second refrigerant injection section 34 as refrigerant injection sections that inject liquid such as water, gas, or other refrigerants toward the rod-shaped steel material 51.

[0032] Of these, in the illustrated example, the first refrigerant injection section 32 is located at approximately the same position in the axial direction as the heating section 21, as shown in Figures 1 and 2, and as shown in Figure 4, for example, is located forward of the heating section 21 in the rotation direction of the rod-shaped steel material 51 (the tip side of the direction of the black arrow indicating the rotation direction drawn on the rod-shaped steel material 51 in Figure 4), that is, at a position through which the heating target area 52a heated by the heating section 21 passes immediately after heating, and is arranged at a distance from the outer surface of the rod-shaped steel material 51.

[0033] The first refrigerant injection unit 32 injects the refrigerant toward a heating completion point 52b located forward in the rotational direction from the heating target point 52a by the heating unit 21. Here, the heating completion point 52b refers to a portion of the peak portion 52 adjacent to the heating target point 52a on the rotational direction. By injecting the refrigerant from the first refrigerant injection unit 32 toward the heating completion point 52b, the heating completion point 52b is rapidly cooled from the high temperature state immediately after heating by the heating unit 21. By the heating unit 21 and the first refrigerant injection unit 32, the peak portion 52 is continuously quenched at the heating target point 52a and the heating completion point 52b as the rod-shaped steel material 51 rotates and advances. The arrangement of the first refrigerant injection unit 32 is not limited to the above-mentioned position as long as it can inject the refrigerant toward the heating completion point 52b.

[0034] In the illustrated embodiment, as shown in FIGS. 2 and 4, the first refrigerant jetting section 32 is provided on a nozzle member 33c attached by a screw or the like to the tip of a connecting member 33b supported by a support rod 33a. The support rod 33a is configured by two linear rod members 33d and 33e connected by an adjustment member 33f, which are oriented at approximately right angles to each other in a side view. Although not necessarily clear from the drawings, the adjustment member 33f, which may be cylindrical, has two holes formed at positions offset in the axial direction (depth direction in FIG. 2), through which the two rod members 33d and 33e are attached. Furthermore, as shown in FIG. 4, the rod member 33d is also inserted into a hole 33g formed in the connecting member 33b. The position and / or orientation of the nozzle opening of the nozzle member 33c can be changed by rotating the rod members 33d and 33e in the holes of the adjustment member 33f or by moving the rod member 33d in the insertion / removal direction within the holes 33g of the connecting member 33b, thereby enabling hardening of the peaks 52 of rod-shaped steel materials 51 of various dimensions and shapes.

[0035] Two pipes 33h are attached to the sides of the nozzle member 33. The refrigerant is supplied to the nozzle member 33 from the pipes 33h and sprayed from the nozzle openings of the nozzle member 33.

[0036] In the illustrated example, the second refrigerant injection unit 34 is composed of pipes or the like arranged on both sides of the heating unit 21 in the axial direction, and injects refrigerant from there toward the inner areas of each groove 53 adjacent to the heating target areas 52a of the peaks 52 in the axial direction (referred to as "heat-adjacent areas 53a"). This prevents unintended preheating, residual heat, or residual heat in each heating-adjacent area 53a, allowing the area to be sufficiently cooled. The second refrigerant injection unit 34 does not necessarily have to be provided on both sides of the heating unit 21 in the axial direction; as long as it is provided on at least one side, the effect of preventing the above-mentioned preheating or residual heat on that side can be obtained.

[0037] In particular, at the heating adjacent portion 53a adjacent to the heating target portion 52a on the rear side in the traveling direction (the right side in FIG. 2 ), the coolant is sprayed from the second coolant spray unit 34 to the heating adjacent portion 53a, and the portion of the peak portion 52 adjacent to the heating target portion 52a on the rear side in the traveling direction is sufficiently cooled, preventing unintended preheating by the heating unit 21. In this state, the portion of the peak portion 52 then reaches the heating target portion 52a and the heating completion portion 52b in that order, and is effectively quenched by heating by the heating unit 21 and rapid cooling by the first coolant spray unit 32. Therefore, in order to cool the heating adjacent portion 53a on the rear side of the heating target portion 52a in the traveling direction more than the heating adjacent portion 53a on the front side (the left side in FIG. 2 ), it may be preferable to spray a larger amount of coolant at the rear second coolant spray unit 34 than at the front second coolant spray unit 34. In order to enable such control of the refrigerant injection flow rate, it is preferable that the second refrigerant injection portions 34 on the front and rear sides in the traveling direction are configured to be able to inject refrigerant at flow rates different from each other.

[0038] As shown in Fig. 3, a plurality of pipes having nozzles as second refrigerant spray units 34 may be provided on one and / or the other axial side of heating unit 21, such as two on each side. In this case, the pipes also have a plurality of nozzles. For example, if it is difficult for the refrigerant to sufficiently reach the bottom of groove 53 due to a narrow width of groove 53, the nozzles of the plurality of pipes serving as second refrigerant spray units 34 can be oriented in different directions to adjust the direction of cooling inside groove 53.

[0039] The second refrigerant injection unit 34 is preferably provided with an injection port positioned and oriented to inject refrigerant toward the heating-adjacent area 53a, which is located rearward in the rotational direction from the heated area 21, in the groove 53 axially adjacent to the heating-target area 52a of the peak 52. In other words, the heating-adjacent area 53a to which the second refrigerant injection unit 34 injects refrigerant is preferably located rearward in the rotational direction from the heated area 21, in the groove 53 axially adjacent to the heating-target area 52a, and the injection port of the second refrigerant injection unit 34 is preferably positioned and oriented to inject refrigerant toward the heating-adjacent area 53a. This allows the heating-adjacent area 53a of the groove 53 to be sufficiently cooled by the refrigerant injected from the second refrigerant injection unit 34 before passing adjacent to the heating-target area 52a, thereby more effectively suppressing heating of the heating-adjacent area 53a when passing adjacent to the heating-target area 52a.

[0040] When refrigerant is sprayed from the second refrigerant spray unit 34 toward the heating-adjacent area 53a, some of the refrigerant may flow into or splash onto the heating target area 52a, potentially hindering heating of the heating target area 52a by the heating unit 21. To address this issue, as in the illustrated embodiment, it is preferable to provide a partition plate 35 between the heating unit 21 and the second refrigerant spray unit 34 to separate the heating target area 52a from the heating-adjacent area 53a. This prevents the refrigerant sprayed from the second refrigerant spray unit 34 from flowing toward the heating target area 52a.

[0041] The partition plate 35 may be made of, for example, a heat-resistant resin. In this case, it is preferable to position the resin partition plate 35 in a position where it can come into contact with the surface of the groove portion 53, such as by slightly pressing it against the surface of the bottom of the groove portion 53 of the rod-shaped steel material 51. This effectively prevents the refrigerant from leaking or passing through between the partition plate 35 and the surface of the groove portion 53 toward the heated adjacent portion 53a. Furthermore, if the partition plate 35 is made of an insulating resin, it can be directly attached to the side of the induction heating coil 22 of the heating unit 21, as in the illustrated embodiment. Furthermore, a pipe serving as the second refrigerant injection unit 34 may be attached to the side of the partition plate 35.

[0042] The partition plate 35 may be disposed on the side of the heating unit 21 in the axial direction where the second refrigerant injection unit 34 is provided. As shown in the figure, when second refrigerant injection units 34 are provided on both sides of the heating unit 21 in the axial direction, it is preferable to dispose two partition plates 35 between each second refrigerant injection unit 34 and the heating unit 21. Although not shown, when a second refrigerant injection unit is provided on only one side of the heating unit in the axial direction, it is sufficient to dispose one partition plate between the second refrigerant injection unit and the heating unit.

[0043] As shown in FIGS. 1 and 2 , the cooling section 31 may further include a third refrigerant injection section 36. The third refrigerant injection section 36 is, for example, a block-shaped member having a number of injection ports formed on the front surface thereof. The third refrigerant injection section 36 is located further rearward of the second refrigerant injection section 34, which is located rearward of the heating section 21 in the direction of travel of the rod-shaped steel material, and is located behind the rod-shaped steel material in the depth direction in FIGS. 1 and 2 . The third refrigerant injection section 36 injects refrigerant onto the peaks 52 and grooves 53 to sufficiently cool them before they approach the heating target area 52 a. This allows the heating section 21 to more effectively heat the heating target area 52 a and the first refrigerant injection section 32 to more effectively rapidly cool the heating-completed area 52 b, while also effectively preventing the heating section 21 from unintentionally heating the grooves 53.

[0044] By using the above-described quenching device 1, the grooves 53 on the outer peripheral surface of the rod-shaped steel material 51 are not quenched, while the peaks 52 can be effectively quenched. [Explanation of symbols]

[0045] 1. Quenching equipment 11 Drive unit 12 Rotational drive source 13 Motion conversion mechanism 13a Fitting roller 21 Heating section 22 Induction heating coil 22a U-shaped part 22b Rod-shaped part 22c Connecting part 23 Conductor 31 Cooling section 32 First refrigerant injection section 33 Nozzle member 33a Support rod 33b Connecting member 33c Nozzle member 33d, 33e Rod member 33f Adjustment member 33g hole 33h Piping 34 Second refrigerant injection section 35 Partition 36 Third refrigerant injection section 41 Support roller 51 Rod-shaped steel material 52 Yamabe 52a Heating target area 52b Heating completed area 53 Groove 53a Adjacent heated area 54a Threaded part 54b Torso CL center axis

Claims

1. A quenching device used for a rod-shaped steel material having ridges and grooves formed on an outer peripheral surface thereof along at least a portion of an axial direction thereof, the quenching device quenching the ridges, a driving unit that rotates the rod-shaped steel material around a central axis and advances it in one axial direction; a heating unit that sequentially heats heating target locations of the spiral peaks that transition along the extending direction of the spiral peaks as the driving unit rotates and advances the rod-shaped steel material; and a cooling unit that cools the rod-shaped steel material, The cooling section is a quenching device having a first refrigerant injection section that injects refrigerant toward a heating completion point that is located forward of the heating target point in the rotation direction of the rod-shaped steel material, and a second refrigerant injection section that injects refrigerant toward a heating adjacent point of the groove portion that is adjacent to the heating target point of the ridge portion in the axial direction.

2. The quenching device according to claim 1, wherein the first coolant injection section is provided so that the position and / or the direction of the injection port can be changed.

3. the second refrigerant injection portions are arranged on both sides of the front side and the rear side in the advancing direction of the rod-shaped steel material, with the heating portion separated in the axial direction, 3. The quenching device according to claim 1, wherein each of the second refrigerant injection sections is capable of injecting refrigerant at a flow rate different from each other.

4. 3. The quenching device according to claim 1, further comprising a partition plate disposed between the heating section and the second refrigerant injection section to separate the heated area from the adjacent heated area and to prevent the refrigerant injected from the second refrigerant injection section from flowing toward the heated area.

5. 5. The quenching device according to claim 4, wherein the partition plate is made of resin and is provided at a position where it contacts the surface of the groove portion of the rod-shaped steel material.

6. 3. The quenching device according to claim 1, wherein an injection port of the second refrigerant injection portion is disposed at a position and in a direction to inject refrigerant toward the heating-adjacent portion of the groove portion adjacent to the heating target portion of the peak portion in the axial direction, the heating-adjacent portion being located rearward of the heating portion in the rotational direction.

7. 3. The quenching device according to claim 1, wherein the second coolant injection section has a plurality of injection ports which inject the coolant in different directions.

8. the second refrigerant injection section is provided at least rearward of the heating section in the direction of travel of the rod-shaped steel material, 3. The quenching device according to claim 1, wherein the cooling section further comprises a third refrigerant injection section provided further rearward in the direction of travel of the second refrigerant injection section and injecting refrigerant onto the rod-shaped steel material.

9. 3. The hardening device according to claim 1, wherein the heating section has an induction heating coil.

10. 3. The hardening device according to claim 1, wherein the drive unit comprises a rotary drive source that rotates the rod-shaped steel material around a central axis, and a motion conversion mechanism that is fitted into the crest and / or groove of the rod-shaped steel material and converts the rotational motion of the rod-shaped steel material caused by the rotary drive source into linear motion in the axial direction.

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