Method and apparatus for quenching steel bars

Abstract

To provide a method and apparatus for quenching steel bars that allows for simple and rapid quenching of the entire steel bar. [Solution] A steel bar 1 is held by a pair of centers 2 and 2', and the outer surface 1b1 in the short direction of one end 1b is held by a first chuck 3. Furthermore, while rotating the steel bar 1 in the short direction around the central axes 1a and 1a', the pair of centers 2 and 2' and the first chuck 3 are moved in the direction of the heating section 4a and the cooling section 4b. At this time, before the other end 1b' passes through the cooling section 4b and the one end 1b enters the heating section 4a, the outer surface 1b1' in the short direction of the other end 1b' that has passed is held by a second chuck 3' while maintaining the holding, rotation and movement. Then, the holding of the first chuck 3 is released, and the steel bar is passed through the heating section 4a and the cooling section 4b while maintaining the holding by the pair of centers 2 and 2' and the second chuck 3', the rotation by the second chuck 3', and the movement in the hardening direction Qu. This is a method for hardening a steel bar.

Description

Technical Field

[0001] The present invention relates to a quenching method and a quenching apparatus for steel bars.

Background Art

[0002] Conventionally, quenching of steel materials such as steel bars has been performed by supporting both ends of the steel material with a chuck and a center, or holding both ends of the steel material with chucks (see Patent Documents 1 to 3).

[0003] Patent Document 1 describes that "In the rack manufacturing method of the present embodiment, high-frequency induction heating is performed while rotating the workpiece 1 that has undergone machining (cutting or forging).", "The high-frequency quenching apparatus 10 used in the quenching step of the present embodiment is as shown in FIG. 3. That is, the high-frequency quenching apparatus 10 is constituted by a rotating shaft 11, a center 12, a brake roller 13, an induction heating coil 15, and a high-frequency power source, a cooling device, and a workpiece moving device (not shown).", "The rotating shaft 11 is rotated by receiving power from a motor 20 and a speed reducer (not shown), and is provided with a chuck 21 that holds the workpiece 1.", "The center 12 is provided at a position facing the chuck 21." (Paragraph

[0016] ), and "In the rack manufacturing method of the present embodiment, both ends of the workpiece 1 that has undergone the machining step are supported by the chuck 21 and the center 12. That is, one end side of the workpiece 1 is supported by the center 12, and the other end side of the workpiece 1 is gripped by the chuck 21." (Paragraph

[0017] ). The high-frequency quenching apparatus 10 of FIG. 3 described in Patent Document 1 is shown in FIG. 12.

[0004] Patent Document 2 states that, "When surface hardening a predetermined shaft portion of a flanged shaft, it is necessary to hold the flange portion perfectly vertically and rotate it at a constant speed at all times in order to suppress distortion that may occur during hardening. For this reason, flanged shaft hardening devices such as those shown in Figures 1a and 1b have been conventionally used. 1 and 2 are a head center and a tail center arranged opposite each other on a straight line, and both can move forward and backward by cylinders 3 and 4. ... The right end of the hollow rotating shaft 9 in the figure above extends outside the head stock 5, and the back surface of a chuck 15 with a U-shaped cross-section is fixed to its end face. As shown in Figure 1b, the base portion 152 of the chuck 15 is disc-shaped, and the base portion 152 For example, on the upper and lower circumferential portions separated by 180°, claws 151, 151 are integrally formed, protruding perpendicularly to the respective circumferential portions, and the ends of the claws 151, 151 are bent downward and upward, respectively, to form an L-shape. The distance A between the connection points of each claw 151, 151 connected to the circumferential portion of the base 152 is set to be sufficiently larger than the diameter D of the flange portion WF of the flanged shaft W which is the workpiece to be hardened, and the distance between the bent tips of the claws 151, 151 is set to be smaller than the diameter D of the flange portion WF. Furthermore, a through hole 153 is formed in the center of the base 152, and the head center 1 can advance through the through hole 153 to the position between the tips of the claws 151, 151." (Column 1, line 26 to Column 3, line 4) Figure 13 shows the chuck 15 of Figure 1b described in Patent Document 2.

[0005] Patent Document 3 states, "In order to process a long rod according to the present invention, both ends of the rod are firmly grasped by chucks (22, 24) (Figure 1) that can be tightened or loosened with a socket wrench (not shown), as is customary in the industry. ...When the chucks (22, 24) are mounted to be rotatable, at least one gear motor M and a chain drive (33) are provided to rotate the rod B while tension is applied and stretched by a hydraulic cylinder (36)." (Page 4, upper left column, bottom 5 lines to upper right column) (Lines 7-7) "A conventional heating power supply (not shown) is connected to the induction coil. After the rod is heated by the induction coil, a conventional pump and supply tank (not shown) are connected to the quenching coil (42) to direct a suitable spray of quenching fluid onto the rod B so as to cool the outer surface of the rod B while moving the carriage (46) to the left in Figure 1. ...In Figure 1, the portion of the rod B held by the chucks (22, 24) and the portion adjacent to the chucks are not processed." (Page 4, bottom left, line 10 - bottom right, line 3) As described above, the hardening methods described in Patent Documents 1 to 3 have the problem that the part gripped by the chuck and the part adjacent to the chuck are not hardened.

[0006] On the other hand, there is also known heat treatment equipment that automatically heat-treats (quenches) both ends of a steel material (see Patent Document 4). Patent Document 4 states, "When the heat treatment of one side of the workpiece is completed, the other side of the workpiece is subsequently heat-treated by the second heat treatment apparatus 20B. The workpiece W placed on the transfer table 15 is moved in the Yb direction by the drive means 16 which drives the transfer table 15 (STEP 31), and when it is moved to the second position of the second heat treatment apparatus 20B (STEP 32), the transfer table stops and the workpiece W is loaded into the second heat treatment apparatus 20B (STEP 33)." (Paragraph

[0037] ) "The workpiece W loaded into the second heat treatment apparatus 20B is then gripped by the chuck 28 of the second heat treatment apparatus 20B on the side that has been quenched and tempered by the first heat treatment apparatus 20A, and the opposite side is subjected to the first heat treatment apparatus Similar to 20A, the quenching and tempering heat treatment is performed by the same operation as in STEP 6 to STEP 30 of the above process (STEP 34). However, the direction of movement of the workpiece is the opposite of that of the first heat treatment apparatus 20A described above." (Paragraph

[0038] ) "The workpiece W, whose ends have been heat-treated in this way, returns to the standby position, the chuck is released and placed on the extraction table 50, the extraction table 50 is driven by the driving means 51 and the workpiece moves (STEP 35), stops at the discharge position (STEP 36), the workpiece is discharged and the operation is completed (STEP 37). The above process allows both ends of the workpiece to be heat-treated automatically." (Paragraph

[0039] ) [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2014-133924 [Patent Document 2] Special Publication No. 61-57893 [Patent Document 3] Japanese Patent Application Publication No. 1-156419 [Patent Document 4] Japanese Patent Publication No. 2002-105531 [Overview of the project] [Problems that the invention aims to solve]

[0008] Conventional hardening apparatuses and methods have the problem that the portion held by the chuck, as described in Patent Documents 1 to 3, is not hardened. On the other hand, Patent Document 4 describes a heat treatment apparatus that automatically heat-treats (hardens) both ends of a steel material by changing the side that is held by the chuck. However, this apparatus is characterized by arranging a first heat treatment apparatus and a second heat treatment apparatus, each with an induction heating apparatus facing in the opposite direction, with their axes parallel, and then hardening and tempering one end of the pipe member to be treated with the first heat treatment apparatus, and then hardening and tempering the other end of the member with the second heat treatment apparatus, thereby heat-treating both ends of the member. This results in a complex hardening apparatus and the problem that it takes time to move the workpiece (steel material).

[0009] In view of the above-mentioned prior art, the object of the present invention is to provide a method and apparatus for quenching a steel bar that can quench the entire steel bar, including the portion gripped (or held; the same applies hereinafter) by the chuck, in a simple and rapid manner. [Means for solving the problem]

[0010] To solve the above problems, the present invention employs the following means. (1) The ends of the central axis in the longitudinal direction of the steel bar are held by a pair of centers, and the outer circumferential surface in the short direction of one end of the steel bar, which is on the upstream side in the hardening direction, is held by a first chuck, and while the steel bar is rotated in the short direction about the central axis by the first chuck, the pair of centers and the first chuck are moved from the other end of the steel bar toward the heating and cooling section located downstream in the hardening direction, so that the other end passes through the cooling section, and the one end A method for quenching a steel bar, wherein, before the end enters the heating section, the outer circumferential surface of the other end that has passed through is held by a second chuck in the short direction while maintaining the holding, rotation, and movement; then, the holding by the first chuck is released; and the bar is passed through the heating section and cooling section to the one end while maintaining the holding by the pair of centers and the second chuck, the rotation by the second chuck, and the movement in the quenching direction by the pair of centers and the second chuck. (2) The method for quenching a steel bar according to (1), wherein the holding by the second chuck is performed while rotating the second chuck in the same direction as the rotation by the first chuck. (3) The method for quenching a steel bar according to (1) or (2), wherein the first chuck releases the holding by the first chuck while rotating the first chuck in the same direction as the rotation by the second chuck. (4) A steel bar quenching apparatus comprising: a pair of centers that hold both end faces of the central axis in the longitudinal direction of the steel bar; a first chuck that holds the outer circumferential surface in the short direction of one end of the steel bar, which is on the upstream side in the quenching direction, and rotates the steel bar in the short direction about the central axis; a heating section and a cooling section arranged on the downstream side in the quenching direction; a second chuck that holds the outer circumferential surface in the short direction of the other end of the steel bar, which is on the downstream side in the quenching direction, and rotates the steel bar in the short direction about the central axis; and means for moving the pair of centers and the first chuck from the other end side toward the heating section and cooling section, wherein the apparatus is configured to switch between the holding of the outer circumferential surface in the short direction of one end of the steel bar and the rotation of the steel bar by the first chuck, and the holding of the outer circumferential surface in the short direction of the other end of the steel bar and the rotation of the steel bar by the second chuck. [Effects of the Invention]

[0011] The present invention provides a method and apparatus for quenching steel bars, which allows for the simple and rapid quenching of the entire steel bar, including the portion held by the chuck. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic diagram showing the first step of a method for quenching a steel bar according to one embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram showing the second step of a quenching method for steel bars according to one embodiment of the present invention. [Figure 3] Figure 3 is a schematic diagram showing the third step of a quenching method for steel bars according to one embodiment of the present invention. [Figure 4] Figure 4 is a schematic diagram showing the fourth step of a quenching method for steel bars according to one embodiment of the present invention. [Figure 5] Figure 5 is a schematic diagram showing the fifth step of a quenching method for steel bars according to one embodiment of the present invention. [Figure 6] Figure 6 is a schematic diagram showing the sixth step of a quenching method for steel bars according to one embodiment of the present invention. [Figure 7]FIG. 7 is a schematic diagram showing the seventh step of the steel bar quenching method according to one embodiment of the present invention. [Figure 8] FIG. 8 is a schematic diagram showing the eighth step of the steel bar quenching method according to one embodiment of the present invention. [Figure 9] FIG. 9 is a schematic diagram showing the ninth step of the steel bar quenching method according to one embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram showing the tenth step of the steel bar quenching method according to one embodiment of the present invention. [Figure 11] FIG. 11 is a schematic diagram showing the eleventh step of the steel bar quenching method according to one embodiment of the present invention. [Figure 12] FIG. 12 is a schematic diagram of a high-frequency quenching apparatus of the prior art (see Patent Document 1). [Figure 13] FIG. 13 is a schematic diagram of a chuck of the prior art (see Patent Document 2). [Mode for Carrying Out the Invention]

[0013] A steel bar quenching method and quenching apparatus according to one embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described with reference to FIG. 1 to FIG. 11.

[0014] In this embodiment, the method for quenching a steel bar involves holding both end faces 1a1 and 1a1' of the central axes 1a and 1a' in the longitudinal direction of the steel bar 1 with a pair of centers 2 and 2'. Additionally, the outer circumferential surface 1b1 of one end 1b of the steel bar 1, which is upstream in the quenching direction Qu, in the short direction is held by a first chuck 3. Furthermore, while rotating the steel bar 1 in the short direction around the central axes 1a and 1a' using the first chuck 3, the pair of centers 2 and 2' and the first chuck 3 are moved from the other end 1b' side towards the heating section 4a and cooling section 4b located downstream in the quenching direction Qu. During this movement, before the other end 1b' passes through the cooling section 4b and the other end 1b enters the heating section 4a, the outer peripheral surface 1b1' in the shorter direction of the other end 1b' that has passed is held by the second chuck 3' while maintaining the holding (holding by the pair of centers 2, 2' and the first chuck 3), the rotation (rotation by the first chuck 3), and the movement (movement of the pair of centers 2, 2' and the first chuck 3 in the hardening direction Qu). Then, the holding of the first chuck 3 is released, and while maintaining the holding by the pair of centers 2, 2' and the second chuck 3', the rotation by the second chuck 3', and the movement of the pair of centers 2, 2' and the second chuck 3' in the hardening direction Qu, the other end 1b' is allowed to pass through the heating section 4a and the cooling section 4b.

[0015] The steel bar quenching apparatus according to this embodiment includes a pair of centers 2, 2' that hold both end faces 1a1, 1a1' of the central axes 1a, 1a' in the longitudinal direction of the steel bar 1, a first chuck 3 that holds the outer peripheral surface 1b1 in the short direction of one end 1b of the steel bar 1 which is on the upstream side in the quenching direction Qu, and rotates the steel bar 1 in the short direction around the central axes 1a, 1a', a heating section 4a and a cooling section 4b (quenching section 4) arranged on the downstream side in the quenching direction Qu, and the outer peripheral surface 1 in the short direction of the other end 1b' of the steel bar 1 which is on the downstream side in the quenching direction Qu The device comprises a second chuck 3' that holds b1' and rotates the steel bar 1 in the short direction around the central axes 1a and 1a', and means for moving a pair of centers 2 and 2' and the first chuck 3 from the other end 1b' side toward the heating section 4a and the cooling section 4b, and is configured to switch between the first chuck 3 holding the outer circumferential surface 1b1 in the short direction of one end 1b of the steel bar 1 and rotating the steel bar 1, and the second chuck 3' holding the outer circumferential surface 1b1' in the short direction of the other end 1b' of the steel bar 1 and rotating the steel bar 1.

[0016] The steel bar quenching method and apparatus according to this embodiment allow for the entire steel bar 1, including the portion held by the chuck, to be quenched simply and quickly in order to perform the quenching described above.

[0017] In other words, the steel bar quenching method and apparatus according to this embodiment hold one end 1b of the steel bar 1, which is on the upstream side in the quenching direction Qu, with the first chuck 3, and move the other end 1b' in the quenching direction Qu without holding it with the second chuck 3', and quench it by passing it through the heating section 4a and the cooling section 4b in that order from the other end 1b' side, and before the other end 1b' passes through the cooling section 4b and the one end 1b enters the heating section 4a, the other end 1b' that has passed (quenched) is held with the second chuck 3', and then the holding of the first chuck 3 is released (i.e., the holding by the first chuck 3 is switched to the holding by the second chuck 3'), and the steel bar 1 is passed through the heating section 4a and the cooling section 4b until the one end 1b is reached, so that the entire steel bar 1, including the portion held by the chuck, can be quenched.

[0018] Furthermore, the method and apparatus for quenching steel bars according to this embodiment is simple because the steel bars 1 are quenched against a heating section 4a and a cooling section 4b (quenching section 4) arranged in the quenching direction Qu by being held, rotated, and moved by a pair of centers 2, 2', a first chuck 3, and a second chuck 3'. Moreover, when switching from holding by the first chuck 3 to holding by the second chuck 3', the movement is maintained during the process, allowing for rapid quenching.

[0019] The method and apparatus for quenching steel bars according to this embodiment will be described in more detail below. Each step of the hardening method for steel bars according to this embodiment will be explained with reference to Figures 1 to 11. First, as shown in Figure 1, the steel bar 1, which is the member to be hardened, is placed on the first mounting section 30. The first mounting section 30 has multiple drive mounting sections 30c, each connected to the drive section 30a and capable of being driven vertically (in the direction of the Y arrow and its opposite direction, the same applies hereinafter), and having a holding section 30b at its upper end that holds a part of the longitudinal direction of the steel bar 1 from the short direction. These drive mounting sections 30c are provided parallel to each other in the left-right direction (in the direction of the X arrow and its opposite direction: hardening direction Qu, the same applies hereinafter). The steel bar 1 is held by the multiple drive mounting sections 30c along the left-right direction, and mounted so that the longitudinal direction of the steel bar 1 is in series and coaxial with the left-right direction. Steel bar 1 refers to steel that has been hot-rolled into a bar shape and cut to a predetermined length.

[0020] Next, as shown in Figure 2, the end faces 1a1 and 1a1' of the central axes 1a and 1a' in the longitudinal direction of the steel bar 1 placed on the first mounting section 30 are held by a pair of centers 2 and 2'. In other words, it has a first mounting section 30 on which the steel bar 1, which is the member to be hardened, is placed along the longitudinal direction of the steel bar 1. The pair of centers 2 and 2' are rotatable in the short direction of the steel bar 1, in conjunction with or linked to the rotation of the first chuck 3 and the second chuck 3', which will be described later, with respect to the central axes 2a and 2a', which are in series and coaxial with the central axes 1a and 1a' in the longitudinal direction of the steel bar 1.

[0021] The pair of centers 2 and 2' comprises a first center 2 positioned upstream of the hardening direction Qu (opposite to the direction of the arrow X, hereafter the same) in the hardening direction Qu (on the opposite side of the direction of the arrow X, hereafter the same) and a second center 2' positioned downstream of the hardening direction Qu (on the side of the direction of the arrow X, hereafter the same).

[0022] When the bar 1 is held by a pair of centers 2 and 2', the first center 2 moves downstream and the second center 2' moves upstream toward both end faces 1a1 and 1a1' of the bar 1 placed on the first mounting section 30 by a drive unit (not shown), and the end faces 1a1 and 1a1' of the central axis 1a and 1a' in the longitudinal direction of the bar 1 are held at the tip. When the second center 2' holds the end face 1a1' toward the upstream side, the second center 2' passes through the heating section 4a and the cooling section 4a.

[0023] Next, as shown in Figure 3, the outer circumferential surface 1b1 in the short direction of one end 1b of the steel bar 1, which is on the upstream side in the hardening direction Qu, is held by the first chuck 3. Holding by the first chuck 3 involves the first chuck 3, which is initially in its position (for example, Figure 1), being moved by a drive unit (not shown) to a position where it can grasp one end 1b of the steel bar 1 placed on the first mounting section 30, and then grasping and holding it. The first chuck 3 is located upstream of the first mounting portion 30 in the hardening direction Qu, and is positioned around the first center 2.

[0024] Next, as shown in Figure 4, while maintaining the holding of the pair of centers 2, 2' and the first chuck 3, the first chuck 3 rotates the steel bar 1 in the shorter direction around the central axes 1a, 1a'.

[0025] In this embodiment, after gripping and holding the steel bar 1 with the first chuck 3, before rotating the first chuck 3, each holding part 30b of the plurality of drive mounting parts 30c on the first mounting part 30 on which the steel bar 1 is placed is moved (retracted) downward (in the opposite direction of the Y arrow, the same applies hereinafter) by the drive part 30a. At that time, each holding part 30b is retracted downward to a position where it does not come into contact with the first chuck 3 which is moving in the hardening direction Qu. Note that the downward retraction of each holding part 30b may be performed after holding both end faces 1a1, 1a1' of the steel bar 1 with the pair of centers 2, 2', but before gripping and holding the steel bar 1 with the first chuck 3.

[0026] Next, as shown in Figures 5 and 6, while maintaining the holding by the pair of centers 2, 2' and the first chuck 3 (hereinafter referred to as pre-switching holding) and the rotation by the first chuck 3 (hereinafter referred to as pre-switching rotation), the pair of centers 2, 2' and the first chuck 3 are moved (hereinafter referred to as pre-switching movement) from the other end 1b' side, which is downstream in the quenching direction Qu of the steel bar 1, towards the heating section 4a and cooling section 4b located downstream in the quenching direction Qu. In this way, the steel bar 1 moves from the other end 1b' side towards the heating section 4a and cooling section 4b, and while rotating in the shorter direction from the other end 1b' side, it passes through the heating section 4a and the cooling section 4b (quenching section 4) in this order. The heating section 4a and the cooling section 4b (quenching section 4) are located downstream of the first mounting section 30 in the quenching direction Qu, and are arranged in this order between the first mounting section 30 and the second center 2'.

[0027] Next, as shown in Figure 7, while maintaining the pre-switching hold, pre-switching rotation, and pre-switching movement, the other end 1b' passes through the heating section 4a and then through the cooling section 4b (being hardened as it passes through), and before one end 1b enters the heating section 4a, the outer peripheral surface 1b1' in the short direction of the other end 1b' that has passed through (become hardened) is held by the second chuck 3'. The second chuck 3' is located upstream of the cooling section 4b in the quenching direction Qu, and is positioned around the second center 2'. Holding by the second chuck 3' involves the second chuck 3', in its initial position (e.g., Figure 7), gripping and holding the other end 1b' that has passed through the heating section 4a and the cooling section 4b.

[0028] Furthermore, after holding the other end 1b' with the second chuck 3', the rotation before switching (rotation by the first chuck 3) is changed to rotation by the second chuck 3' (hereinafter referred to as rotation after switching). That is, the rotational drive by the first chuck 3 is changed to the rotational drive by the second chuck 3'. This change in rotational drive is achieved by reducing the drive output that was driving the rotation with the first chuck 3 and increasing the drive output with the second chuck 3'.

[0029] It is preferable that the holding by the second chuck 3' is performed while rotating the second chuck 3' in the same direction as the rotation by the first chuck 3. The pair of centers 2 and 2' rotate in the short direction of the steel bar 1, in conjunction with or linked to the rotation of the first chuck 3 and the second chuck 3', around their central axes 2a and 2a', which are in series and coaxial with the central axes 1a and 1a' in the longitudinal direction of the steel bar 1. In this way, rotation can be continued after the switch without stopping the rotation before the switch, thus enabling uniform hardening in the longitudinal and transverse directions of the steel bar 1. Furthermore, damage caused by friction between the rotating steel bar 1 and the second check 3 when it is held in place can be reduced.

[0030] Next, as shown in Figure 8, the holding of the first chuck 3 is released while maintaining the pre-switching hold, post-switching rotation, and pre-switching movement. Before the release of the hold, the second chuck 3' also moves in the hardening direction Qu in sync with the pair of centers 2, 2' and the first chuck 3. After the release, the pair of centers 2, 2' and the second chuck 3' move in the hardening direction Qu (hereinafter referred to as post-switching movement). It is preferable to release the holding by the first chuck 3 by rotating the first chuck 3 in the same direction as the rotation by the second chuck 3'. This method reduces damage caused by friction between the rotating steel bar 1 and the second check 3' when removing the check 3' from the bar.

[0031] Next, as shown in Figure 9, while maintaining the post-switching hold, post-switching rotation, and post-switching movement, the steel bar 1 is passed through the heating section 4a and the cooling section 4b up to one end 1b. During this process, the first center 2 passes through the heating section 4a and the cooling section 4b.

[0032] Next, as shown in Figure 10, the (hardened) steel bar 1 that has passed through the heating section 4a and the cooling section 4b is placed on the second mounting section 30'. The second mounting section 30' has multiple drive mounting sections 30c' arranged parallel to each other in the left-right direction, each drive section 30a' and a holding section 30b' connected to the drive section 30a' that can be driven vertically and has an upper end that holds a portion of the longitudinal direction of the steel bar 1 from the short direction. The steel bar 1 is held by the multiple drive mounting sections 30c' along the left-right direction and mounted so that the longitudinal direction of the hardened steel bar 1 is in series and coaxial with the hardening direction Qu.

[0033] In this embodiment, while the second mounting section 30' passes through the heating section 4a and the cooling section 4b from being held by the second chuck 3' to one end 1b of the steel bar 1, each of the holding sections 30b' is retracted downward by the drive section 30a'. After the second check 3' passes above the drive section 30a', the holding section 30b' is driven upward by the drive section 30a' to place the steel bar 1. The second mounting section 30' is positioned between the heating section 4a and the cooling section 4b (quenching section 4) and the second chuck 3', and is retracted below the second chuck 3' when the other end 1b' of the steel bar 1 is held by the second check 3'. Finally, as shown in Figure 11, the holding of the other end 1b' of the steel bar 1 by the second check 3' and the holding of the pair of centers 2, 2' are released, and the hardened steel bar 1 placed on the second mounting section 30' is retrieved.

[0034] The maximum outer diameter D1 of the steel bar 1 in the short direction is less than the maximum inner diameter D3 of the heating section 4a in the short direction, and less than the maximum inner diameter D4 of the cooling section 4b in the short direction. Also, the maximum outer diameter D2 of the pair of centers 2 and 2' in the short direction is less than or equal to the maximum outer diameter D1 of the steel bar 1 in the short direction. The maximum outer diameter D1 of the steel bar 1 is, for example, 140 mm. The maximum longitudinal length of the steel bar 1 is, for example, 2000 mm. The maximum inner diameter D3 of the heating section 4a and the maximum inner diameter D4 of the cooling section 4b are, for example, 200 mm. The maximum outer diameter D2 of the pair of centers 2, 2' is, for example, 100 mm.

[0035] The means for moving the steel bar 1, the pair of centers 2, 2', and the first and second chucks 3, 3' in the hardening direction Qu are not limited, but for example, means such as being attached to a drive unit (not shown) and moving them in the hardening direction Qu may be employed. As a means for rotating the first and second chucks 3 and 3', for example, a motor like the one described in Patent Document 1 can be used. The rotation during the opening of chuck 3 and the loading of chuck 3' can be performed by synchronous control of the motor.

[0036] As the first and second chucks 3 and 3', chucks like those described in Patent Document 2 can be used. That is, the bases 3b and 3b' of the chucks 3 and 3' are disc-shaped, and two jaws 3a, 3a and 3a', 3a' are integrally formed on the upper and lower circumferential portions of the bases 3b and 3b', separated, for example by 180°, respectively, projecting perpendicular to the circumferential portion. The ends of the jaws 3a, 3a and 3a', 3a' are bent downward and upward, respectively, to form an L-shape. The spacing between the connection points of the jaws 3a, 3a and 3a', 3a' that connect to the circumferential portions of the bases 3b and 3b' is set to be sufficiently larger than the diameter of the steel bar 1 to be hardened, and the spacing between the bent ends of the jaws 3a, 3a and 3a', 3a' is set to be smaller than the diameter of the steel bar 1. Furthermore, through holes are formed in the center of the base portions 3b and 3b', allowing them to advance through these through holes to a position between the tips of the claws 3a, 3a and 3a', 3a'.

[0037] Furthermore, the first and second chucks 3 and 3' can also be air chucks consisting of three jaws, as described in Patent Document 4, which are driven to open and close with air to grip and release the ends of the steel bar 1. In this case, an opening and closing jaw chuck with bifurcated jaws for gripping the workpiece can be used.

[0038] Furthermore, as mentioned above, when the first chuck 3 is holding the steel bar 1 with its jaws 3a, 3a, the jaws 3a', 3a' of the second chuck 3' are released to remove the steel bar 1, and when the second chuck 3' is holding the steel bar 1 with its jaws 3a', 3a', the jaws 3a, 3a of the first chuck 3 are released to remove the steel bar 1.

[0039] A ball screw can be used as the steel bar 1. Ball screws and other feed screw components are frequently used in machine tools to move machining heads and other components. Since these feed screw components require wear resistance, it is preferable to machine them from a rod and then harden the surface by heat treatment to impart wear resistance. The hardening method of this embodiment is applicable to ball screws with a diameter of 8 to 140 mm and a length of 700 to 2000 mm.

[0040] Furthermore, the heating section 4a can be a high-frequency heating device having a high-frequency induction heating coil. The quenching temperature can be 950 to 1100°C if the steel bar 1 is a threaded component.

[0041] A water-cooled jacket can be used as the cooling section 4b. The steel bar 1 is hardened by injecting a cooling fluid from the water-cooled jacket into the steel bar 1 when it reaches the hardening temperature. The water-cooling jacket may be made relatively movable to accommodate the expansion and contraction of the screw pitch when the steel bar 1 is a threaded member. If the screw pitch has expanded too much, it can be contracted by bringing the cooling section 4b (water-cooling jacket) closer to the heating coil of the heating section 4a.

[0042] The timing for moving (retracting) each holding portion 30b of the multiple drive mounting portions 30c on the first mounting portion 30 on which the steel bar 1 is placed, downward (opposite direction of the Y arrow, the same applies hereafter) by the drive unit 30a can be set as appropriate, as long as it does not come into contact with the moving first chuck 3. Similarly, the timing for driving the holding portion 30b' of the second mounting portion 30' upward can also be set as appropriate, as long as it does not come into contact with the moving second check 3'. [Industrial applicability]

[0043] Since the quenching method and apparatus of the present invention can be used to quench an entire steel bar easily and quickly, it has high industrial applicability. [Explanation of Symbols]

[0044] 1 steel bar 1a, 1a' Central axis of steel bar 1 1a1, 1a1' End faces of the central axes 1a and 1a' in the longitudinal direction of the steel bar 1 1b One end of steel bar 1 1b' The other end of the steel bar 1 1b1 Outer surface of one end 1b of the steel bar 1 in the short direction 1b1' Outer circumferential surface in the short direction of the other end 1b' of the steel bar 1 2, 2' Pair of centers 2a, 2a' The central axis of a pair of centers 2 and 2' 3. First Chuck 3' Second Chuck 3a, 3a' First and second chucks, 3 and 3' jaws 3b, 3b' Base of the first and second chucks 3 and 3' 4. Hardening equipment 4a Heating section of the quenching apparatus 4b Cooling section of the quenching device 30 First mounting section 30' Second mounting section 30a, 30a' Drive unit for the first and second mounting sections 30, 30' 30b, 30b' Holding parts for the first and second mounting parts 30, 30' 30c, 30c' Drive mounting section of the first and second mounting sections 30, 30'

Claims

1. The two end faces of the central axis in the longitudinal direction of the steel bar are held by a pair of centers, and the outer circumferential surface of one end of the steel bar in the short direction, which is on the upstream side in the hardening direction, is held by a first chuck, and while the steel bar is rotated in the short direction about the central axis by the first chuck, the pair of centers and the first chuck are moved from the other end of the steel bar toward the heating and cooling sections located downstream in the hardening direction. Before the other end passes through the cooling section and the one end enters the heating section, the outer circumferential surface of the other end in the shorter direction that has passed is held by the second chuck while maintaining the holding, rotation, and movement. Subsequently, the holding by the first chuck is released, A method for quenching a steel bar, which involves passing the bar through the heating section and the cooling section to one end while maintaining holding by the pair of centers and the second chuck, rotation by the second chuck, and movement in the quenching direction by the pair of centers and the second chuck.

2. The method for quenching a steel bar according to claim 1, wherein the holding by the second chuck is performed while rotating the second chuck in the same direction as the rotation by the first chuck.

3. The method for quenching a steel bar according to claim 1 or 2, wherein the release of the holding by the first chuck is performed by rotating the first chuck in the same direction as the rotation by the second chuck.

4. A pair of centers that hold both end faces of the central axis in the longitudinal direction of the steel bar, A first chuck that holds the outer circumferential surface in the short-side direction of one end of the steel bar, which is on the upstream side in the hardening direction, and rotates the steel bar in the short-side direction about the central axis, A heating section and a cooling section are arranged downstream in the quenching direction, A second chuck holds the outer circumferential surface in the short-side direction of the other end of the steel bar, which is downstream in the quenching direction, and rotates the steel bar in the short-side direction about the central axis, The system includes means for moving the pair of centers and the first chuck from the other end side toward the heating and cooling sections, A steel bar quenching apparatus configured to switch between holding the outer circumferential surface of one end of the steel bar in the short direction and rotating the steel bar by the first chuck, and holding the outer circumferential surface of the other end of the steel bar in the short direction and rotating the steel bar by the second chuck.

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