Heat Treatment Jig

Abstract

To provide a heat treatment jig having excellent strength and durability without requiring a special material.SOLUTION: A heat treatment jig has at least two column portions 30 erected on a base tray 10, at least one beam portion 40a that couples between adjacent column portions 30, and a workpiece holding portion 50 for connecting the column portions 30 to hold a workpiece W, in which the beam portion 40a has a first rib portion 41 and a second rib portion 42 provided on at least one of above and below the first rib portion 41, is narrower in width than the first rib portion 41 and connected with the first rib portion 41 by a connecting column 43, and the second rib portion 42 is intermittently formed between one column portion 30 and the other column portion 30 connected by the beam portion 40a.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a heat treatment jig. [Background technology]

[0002] In the manufacturing process of gears, shafts, etc., various heat treatments such as carburizing and quenching are performed. When these heat-treated items are subjected to heat treatment, the items are subjected to the heat treatment while being held in a heat treatment jig. Examples of heat treatment jigs that are used to hold the items include trays, baskets, holders, grids, wire mesh, and standing rods. The heat treatment jig is required to have excellent strength for holding the items to be heat-treated and durability for withstanding the thermal stress and deformation that accompanies the heat treatment.

[0003] Patent Document 1 discloses a heat treatment jig that is made of a C / C composite and is used for heat treatment in a reducing or neutral atmosphere, or in a vacuum. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-123219 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the heat treatment jig (heat treatment jig) described in Patent Document 1 has a problem in that it is expensive because it uses a C / C composite, which is an expensive material.

[0006] The present invention has been made to solve such problems, and has as its object to provide a heat treatment jig that has excellent strength and durability without requiring special materials. [Means for solving the problem]

[0007] A heat treatment jig in one embodiment has at least two support pillars erected on a base tray, at least one beam portion connecting adjacent support pillars, and a work holding portion connecting the support pillars to hold a workpiece, wherein the beam portion has a first rib portion and a second rib portion provided at least above or below the first rib portion, the second rib portion being narrower than the first rib portion and connected to the first rib portion by a connecting column, and the second rib portion is formed intermittently between one support pillar and the other support pillar connected to the beam portion. Effect of the Invention

[0008] According to the present invention, it is possible to provide a heat treatment jig having excellent strength and durability without requiring a special material. [Brief description of the drawings]

[0009] [Figure 1] 1 is a photograph showing the overall configuration of a heat treatment jig into which the configuration according to the first embodiment is incorporated. [Diagram 2] FIG. 2 is a top view of a base tray constituting the heat treatment jig according to the first embodiment. [Diagram 3] 2 is a front view of a support column unit constituting the heat treatment jig according to the first embodiment. FIG. [Figure 4] 2 is a top view of a support column unit constituting the heat treatment jig according to the first embodiment. FIG. [Diagram 5] 2 is a side view of a support column unit constituting the heat treatment jig according to the first embodiment. FIG. [Figure 6] 1 is a front view of a workpiece holding portion that constitutes a heat treatment jig according to a first embodiment. [Figure 7] 1 is a top view of a workpiece holding portion that constitutes the heat treatment jig according to the first embodiment. FIG. [Figure 8] FIG. 2 is a diagram showing a beam portion of an embodiment. [Figure 9] FIG. 9 is a side cross-sectional view taken along line II-II in FIG. 8. [Figure 10] FIG. 13 is a diagram showing a beam portion of a comparative example. [Figure 11]FIG. 1 is a diagram showing a beam portion of Reference Example 1. [Figure 12] FIG. 11 is a diagram showing a beam portion of Reference Example 2. [Figure 13] FIG. 11 is a diagram showing a beam portion of Reference Example 3. [Figure 14] FIG. 4 is a diagram showing heat treatment conditions using the heat treatment jig according to the first embodiment. [Figure 15] FIG. 4 is a diagram showing calculation results of principal stresses generated in the heat treatment jig according to the first embodiment. [Figure 16] 4 is a graph comparing principal stress differences occurring at intersections of the heat treatment jig according to the first embodiment. [Figure 17] 5A to 5C are diagrams illustrating a difference in deformation amount in a beam portion of the heat treatment jig according to the first embodiment. [Figure 18] 4 is a graph comparing differences in deformation amounts in beam portions of the heat treatment jig according to the first embodiment. [Figure 19] FIG. 13 is a diagram showing the rate of increase / decrease of the principal stress difference and the deformation amount difference. [Figure 20] FIG. 13 is a diagram showing a state in which a crack occurs in the heat treatment jig of the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] First embodiment Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment. In addition, in order to clarify the description, the following description and drawings are appropriately simplified. In the following description, the extension direction of the beam part is the X direction, the width direction of the beam part which is perpendicular to the X direction is the Y direction, and the height direction of the beam part which is perpendicular to the X direction and the Y direction is the Z direction.

[0011] First, the basic configuration of the heat treatment jig according to this embodiment will be described with reference to FIG. 1. In this embodiment, a heat treatment jig used for heat treating a plurality of annular workpieces (workpieces to be heat treated) such as transmission gears will be described as an example. FIG. 1 is a photograph showing the overall configuration of a heat treatment jig incorporating the configuration according to the first embodiment. FIG. 1 shows the overall configuration of a heat treatment jig including the configuration according to a comparative example. As shown in FIG. 1, the heat treatment jig is a jig that holds the axis of the workpiece W horizontally, and is manufactured using stainless steel or heat-resistant cast steel. The heat treatment jig is composed of a base tray 10, a support unit 20, and a workpiece holding portion 50. Each heat treatment jig incorporating the configurations of the examples, comparative examples, and reference examples 1 to 3 described below has a different shape of a part of the support unit 20.

[0012] The heat treatment jig according to the present embodiment will be described with reference to Figs. 2 to 7. First, Fig. 2 is a top view of a base tray constituting the heat treatment jig according to the first embodiment. The base tray 10 shown in Fig. 2 has a mesh structure with a plurality of voids penetrating a flat base member in the Z direction, and is configured to allow atmospheric gas and quenching medium to flow through. The base tray 10 has a substantially rectangular outer frame 11 along the XY plane, and an auxiliary frame 12 in which the inside of the outer frame 11 is arranged in a substantially square mesh shape. Furthermore, substantially circular engagement holes 13 penetrating in the Z direction are formed at each vertex position of each square of the auxiliary frame 12. Furthermore, the engagement holes 13 are formed at each vertex position of the rectangle of the outer frame 11, at the intersection positions of the outer frame 11 and the auxiliary frame 12 existing in the X direction, and at the intersection positions of the auxiliary frame 12 at the center parts of each side of the outer frame 11 along the Y direction.

[0013] Next, the support unit 20 will be described with reference to Fig. 3 to Fig. 5. Fig. 3 is a front view of the support unit constituting the heat treatment jig according to the first embodiment. Fig. 4 is a top view of the support unit constituting the heat treatment jig according to the first embodiment. Fig. 5 is a side view of the support unit constituting the heat treatment jig according to the first embodiment.

[0014] In this embodiment, the support column unit 20 has at least two support columns 30 erected on the base tray 10, and at least one beam section 40 connecting adjacent support columns 30. Furthermore, the support column unit 20 has a bottom section 21 and an engagement section 25. In the support column unit 20, three support columns 30 are arranged at a predetermined interval in the X direction. And, between two adjacent support columns 30, three beam sections 40 are arranged at a predetermined interval in the Z direction. That is, in this embodiment, six beam sections 40 are formed for three support columns 30.

[0015] First, the support part 30 constituting the support unit 20 will be described. As shown in FIG. 5, the support part 30 has a support body 31 and a plurality of arms 32. The support body 31 has a mesh structure in which a plurality of voids 33 are provided penetrating a flat plate-like member in the X direction. In this embodiment, two substantially square voids 33 are arranged in parallel in the Y direction of the support body 31 that is substantially rectangular along the YZ plane, and six sets of voids 33 are arranged in parallel in the Z direction, each set consisting of the two voids 33. With this configuration, the support body 31 has ends 34, 36 and a central part 35 extending in the Z direction. In addition, the lower end of the support body 31 along the Y direction is connected to the bottom 21 of the support unit 20.

[0016] The arms 32 are formed to protrude symmetrically in the Y direction from the ends 34, 36 of the column body 31, and support the workpiece holding part 50 described later. The arm 32 shown in FIG. 5 is formed as two substantially U-shaped arms 32 symmetrically with respect to the column body 31. Both ends of the two substantially U-shaped arms 32 are connected to the ends 34, 36 of the column body 31. The lower ends of the two substantially U-shaped arms 32 along the Y direction are connected to the bottom 21 of the column unit 20. The two substantially U-shaped arms 32 support the workpiece holding part 50 by their upper ends extending along the Y direction opposite to the lower ends.

[0017] Furthermore, two substantially triangular arms 32 are formed on the upper sides of the two substantially U-shaped arms 32, which are formed symmetrically with respect to the pillar body 31. One sides of the two substantially triangular arms 32 are connected to ends 34, 36 of the pillar body 31. The two substantially triangular arms 32 are perpendicular to the side connected to the pillar body 31, and support the workpiece holding part 50 by their upper ends extending along the Y direction.

[0018] In this manner, four arms 32 are provided for one support column 30. The arms 32 provided on each support column 30 are arranged parallel to the X direction at the upper and lower positions, and the space between two adjacent arms 32 in the X direction is a holding space for the workpiece W. Two protrusions 32a formed on the upper end surface of each arm 32 regulate the movement of the workpiece holding part 50 in the Y direction when the workpiece holding part 50, which will be described later, is installed on the arm 32. Note that the beam part 40 is provided at the portion indicated by the dashed line in FIG. 5.

[0019] Next, the beam portion 40 constituting the support unit 20 will be described. Fig. 3 shows the support unit 20 including the configuration according to the embodiment. In the following description, for the sake of convenience, specific examples will be described using individual reference numerals when distinguishing between the multiple support bodies 31 present. In Fig. 3, the support bodies 31 are denoted by reference numerals 31a to 31c.

[0020] The detailed shape of the beam portion 40 will be described later with reference to an embodiment, a comparative example, and reference examples 1 to 3. The embodiment, comparative example, and reference examples 1 to 3 described later each have a different shape of the beam portion 40, but they have in common that the beam portion 40 extends in the X direction and is installed to connect adjacent support portions 30. The beam portion 40 protrudes in the X direction from near the intersection of the stitches in the center portion 35 of the support body 31, and extends from one adjacent support body 31 to the other support body 31.

[0021] Next, the bottom 21 constituting the support unit 20 will be described. As shown in FIG. 4, the bottom 21 has a mesh structure in which a plurality of voids 24 are provided penetrating the flat plate-like member in the Z direction. The bottom 21 has a substantially rectangular outer frame 22 along the XY plane, and an auxiliary frame 23 in which the inside of the outer frame 22 is assembled in a substantially rectangular mesh shape. For example, four voids 24 are provided in the bottom 21, and the auxiliary frame 23 is assembled in a cross shape. Then, the support parts 30 are erected at three locations, namely, two sides of the outer frame 22 along the Y direction and a side of the auxiliary frame 23 along the Y direction. In addition, the side of the auxiliary frame 23 along the X direction and the beam part 40 are arranged so as to overlap each other in the X direction. With this configuration, the bottom 21 functions to prevent the support parts 30 arranged on the outside of the heat treatment jig from expanding and deforming in the outward direction of the heat treatment jig. An engagement part 25 is provided at the part indicated by the dashed line in FIG. 5.

[0022] Next, the engaging portion 25 constituting the support column unit 20 will be described. The engaging portion 25 is formed in a cylindrical shape that can engage with the engaging hole 13 of the base tray 10. The engaging portion 25 of the support column unit 20 engages with the engaging hole 13 of the base tray 10, whereby the support column 30 is erected on the base tray 10. As shown in Figs. 3 to 5, the engaging portion 25 is formed to protrude from the lower end surface of the bottom portion 21 opposite to the upper end surface of the bottom portion 21 on which the support column 30 is provided. The engaging portion 25 is provided on a side along the Y direction of the bottom portion 21 corresponding to the arrangement position of each support column 30, and is configured to be able to engage with one of the engaging holes 13 of the base tray 10 in alignment with each other. For example, in Fig. 5, the engaging portion 25 is provided in two engaging portions 25 spaced apart from each other at positions corresponding to the end portions 34 and 36 of the support column main body 31.

[0023] Next, the workpiece holding part 50 will be described with reference to Fig. 6 and Fig. 7. Fig. 6 is a front view of the workpiece holding part constituting the heat treatment jig according to the first embodiment. Fig. 7 is a top view of the workpiece holding part constituting the heat treatment jig according to the first embodiment.

[0024] The workpiece holding part 50 is inserted into an axial hole existing in the axial direction of the workpiece W and is installed on a pair of adjacent arms 32 in the X direction to connect adjacent support parts 30 to hold the workpiece W on the heat treatment jig. As shown in Figs. 6 and 7, the workpiece holding part 50 has a workpiece holding part main body 51 formed from a long and thin plate-like member shaped into a substantially U-shape, and two hook parts 56 protruding from the workpiece holding part main body 51. The workpiece holding part main body 51 has two insertion parts 52 formed into a substantially rectangular shape that is long in the X direction along the XZ plane, which are arranged side by side in the Y direction, and the two insertion parts 52 are connected by an auxiliary part 53 extending in the Y direction.

[0025] A plurality of grooves 54a cut in the Z direction are formed symmetrically at the top and bottom of the upper and lower ends of the insertion part 52 at a predetermined distance, and a groove 54b cut in a direction longer than the groove 54a in the X direction is formed symmetrically at the tip side. The part connecting the base ends of the two insertion parts 52 is a workpiece locking part 55. When the workpiece holding part 50 is attached to the workpiece W, the tip side of the workpiece holding part main body 51 (insertion part 52) ​​is inserted into the workpiece W, and the workpiece locking part 55 is configured to restrict the axial movement of the workpiece W.

[0026] The hook portion 56 is formed to protrude from the workpiece locking portion 55 in the X direction toward the outside of the workpiece holding portion main body 51, and grooves 54c cut in the Z direction are formed symmetrically on the top and bottom of the upper and lower ends of the approximately rectangular plate-like member along the XZ plane. The groove 54c is cut out to have a greater length in the X direction than the groove 54a. The workpiece holding portion 50 is installed so as to be hooked onto the arm 32 by fitting either the upper or lower grooves 54b, 54c between the two protrusions 32a of each arm 32, and between the protrusion 32a on the support main body 31 side and the support main body 31.

[0027] The distance between the two hooking portions 56 in the Y direction is narrower than the distance between the two insertion portions 52 in the Y direction. Therefore, even when multiple work holding portions 50 are installed consecutively in the X direction on the support unit 20, the insertion portion 52 of one work holding portion 50 and the hooking portion 56 of the other work holding portion 50 can be installed on one arm 32 without interfering with each other.

[0028] Next, the detailed shapes of the beam sections 40a to 40e in the example, comparative example, and reference examples 1 to 3 will be described with reference to Figs. 8 to 13. In this embodiment, six beam sections 40 are formed for three pillar bodies 31a, 31b, and 31c, and the six beam sections 40 have the same shape or shapes symmetrical with respect to the pillar body 31b arranged in the middle of the three pillar bodies 31a, 31b, and 31c. Therefore, in the following description, the shape of one beam section 40 provided between the adjacent pillar bodies 31a and 31b will be described as an example.

[0029] (Example) 8 and 9, the beam portion 40a of the embodiment extends in the X direction and is installed so as to connect adjacent support columns 30 (between the support column main body 31a and the support column main body 31b). The beam portion 40a has a first rib portion 41 and a second rib portion 42 that is provided at least above or below the first rib portion 41, has a width narrower than that of the first rib portion 41, and is connected to the first rib portion 41 by a connecting column 43. The second rib portion 42 is formed intermittently between one support column 30 and the other support column 30 to which the beam portion 40a is connected.

[0030] For ease of explanation, when there are a plurality of second rib portions 42 and connecting posts 43, individual reference numerals are used to distinguish between them. In Fig. 9, the second rib portions 42 are denoted by reference numerals 42a to 42g, and the connecting posts 43 are denoted by reference numerals 43a to 43h.

[0031] 3 and 5, the first rib portion 41 is a portion that protrudes in the X direction from near the intersection of the stitches in the center portion 35 of the pillar body 31 and extends continuously from one adjacent pillar body 31 to the other pillar body 31. The width of the first rib portion 41 in the Y direction is formed slightly narrower than the width of the center portion 35 of the pillar body 31 in the Y direction.

[0032] As shown in Figs. 8 and 9, the second rib portion 42 is provided parallel to the first rib portion 41 at a position spaced apart from the first rib portion 41 in the Z direction by a predetermined distance. The width of the second rib portion 42 in the Y direction is configured to be narrower than the width of the first rib portion 41 in the Y direction. The second rib portion 42 is partially formed at a predetermined position along the X direction. That is, the second rib portion 42 is a portion that is formed intermittently along the X direction between adjacent support portions 30. The first rib portion 41 and the second rib portion 42 are connected by a plurality of connecting columns 43 that are formed at predetermined positions in the X direction at intervals and extend in the Z direction.

[0033] In this embodiment, three second rib portions 42a, 42b, and 42c are formed on the upper side of the first rib portion 41, each of which is spaced apart from the other. In two of the three second rib portions 42a, 42b, and 42c, one end of the second rib portion 42a is connected to the center portion 35 of the support body 31a, and one end of the second rib portion 42c is connected to the center portion 35 of the support body 31b. The other end of the second rib portion 42a is connected to a connecting column 43a provided in the vicinity of the support body 31a, and the other end of the second rib portion 42c is connected to a connecting column 43d provided in the vicinity of the support body 31b. The remaining second rib portion 42b formed on the upper side of the first rib portion 41 is disposed between the two second rib portions 42a and 42c, and both ends of the second rib portion 42a and 42c are connected to the first rib portion 41 by the corresponding connecting columns 43b and 43c.

[0034] On the other hand, two sets of second ribs (one set of 42d and 42e, and one set of 42f and 42g) are formed at a distance from each other on the lower side of the first rib portion 41, with two second ribs connected to each other via one connecting pillar 43. Of the two sets of second ribs, one end of the second rib portion 42d is connected to the center portion 35 of the support body 31a, and one end of the second rib portion 42g is connected to the center portion 35 of the support body 31b. The other end of the second rib portion 42d is connected to the connecting pillar 43e, and the other end of the second rib portion 42g is connected to the connecting pillar 43h. Both ends of the second rib portion 42e are connected to the corresponding connecting pillars 43e, 43f, and both ends of the second rib portion 42f are connected to the corresponding connecting pillars 43g, 43h.

[0035] For example, the dimensions of one first rib portion 41 are 249.5 mm in the X direction, 30 mm in the Y direction, and 7 mm in the Z direction. The dimensions of one connecting column 43 are 8 mm in the X direction, 9 mm in the Y direction, and 21.5 mm in the Z direction. The connecting column 43a is provided at an interval of 37.5 mm from one support column main body 31a in the X direction, and three connecting columns 43b to 43d are provided at a pitch of 45 mm from this connecting column 43a toward the other support column main body 31b. The connecting columns 43 are provided symmetrically above and below the first rib portion 41, so that the connecting columns 43e to 43h are provided on the lower side of the first rib portion 41 at the same intervals as the connecting columns 43a to 43d provided on the upper side of the first rib portion 41.

[0036] The second rib portion 42 has second rib portions 42a and 42d having dimensions of 37.5 mm in the X direction, 9 mm in the Y direction, and 9 mm in the Z direction, which are connected to one of the pillar main bodies 31a, and are provided symmetrically above and below the first rib portion 41. The other second rib portions 42b to 42c, 42e to 42g have dimensions of 45 mm in the X direction, 9 mm in the Y direction, and 9 mm in the Z direction, and are provided intermittently above and below the first rib portion 41 along the X direction from each of the second rib portions 42a and 42d toward the other pillar main body 31b. The intersecting portions of the pillar main body 31 and the second rib portion 42, the connecting pillar 43 and the first rib portion 41, and the connecting pillar 43 and the second rib portion 42 each have a curved shape that is curved with a predetermined radius of curvature.

[0037] Although the specific shape of the beam portion 40a of the embodiment has been described above, the shape of the beam portion 40a is not limited to the above. For example, the pattern in which the second rib portion 42 is formed may be provided on at least one of the upper side or the lower side of the first rib portion 41, such as the second rib portions 42b, 42e, and 42f, and a part of the second rib portion 42 may be provided both above and below the first rib portion 41, such as the second rib portions 42a and 42d and the second rib portions 42c and 42g. The pattern in which the second rib portion 42 is formed and the shape and arrangement of each part constituting the beam portion 40a are appropriately designed in consideration of the strength, weight, and efficiency of the heat treatment jig of the heat treatment.

[0038] (Comparative Example) The shape of the beam section 40b of the comparative example will be described with reference to Fig. 10. Fig. 10 is a diagram showing the beam section of the comparative example. The beam section 40b of the comparative example has the same configuration as the beam section 40a of the embodiment, except that the formation pattern of the second rib section is different. Like the beam section 40a, the beam section 40b has a first rib section 41 that extends continuously from one adjacent support body 31 to the other support body 31, and a plurality of connecting columns 43a to 43h that are formed at predetermined positions in the X direction and spaced apart from each other and extend in the Z direction.

[0039] On the other hand, in the beam portion 40b, second rib portions 44a, 44b are provided parallel to the first rib portion 41 at a position spaced a predetermined distance from the first rib portion 41 in the Z direction, and have a shape formed continuously between adjacent support portions 30. That is, the beam portion 40b is formed in a mesh shape with five voids penetrating in the Y direction arranged in parallel in the X direction above and below the first rib portion 41. The beam portion 40b of the comparative example configured in this way has a structure that ensures rigidity while being lightweight, compared to the beam portions 40c to 40e of Reference Examples 1 to 3 described later.

[0040] (Reference example 1) The shape of the beam section 40c of Reference Example 1 will be described with reference to FIG. 11. FIG. 11 is a diagram showing the beam section of Reference Example 1. As shown in FIG. 11, the beam section 40c extends continuously from one adjacent column body 31 to the other column body 31, and has a plate shape that spreads along the XZ plane. In addition, a plurality of grooves cut in the Y direction are arranged in parallel with a space in the X direction. Therefore, in the beam section 40c, thick parts 45a and thin parts 45b corresponding to the grooves are alternately formed along the X direction. The thick parts 45a at both ends of the beam section 40c are connected to the central parts 35 of the two adjacent column bodies 31. The external dimensions of the beam section 40c in the three directions of X, Y, and Z are configured to be the same as the external dimensions of the beam section 40a in the three directions of X, Y, and Z of the embodiment.

[0041] (Reference example 2) The shape of the beam portion 40d of Reference Example 2 will be described with reference to Fig. 12. Fig. 12 is a diagram showing the beam portion of Reference Example 2. As shown in Fig. 12, the beam portion 40d of Reference Example 2 has a shape in which a substantially square void 46 penetrating in the Y direction is provided in the thin-walled portion 45b of the beam portion 40c of Reference Example 1, and otherwise has the same configuration as the beam portion 40c of Reference Example 1.

[0042] (Reference example 3) The shape of the beam section 40e of Reference Example 3 will be described with reference to Fig. 13. Fig. 13 is a diagram showing the beam section of Reference Example 3. As shown in Fig. 13, the beam section 40e extends continuously from one adjacent pillar body 31 to the other pillar body 31, and has a quadrangular prism shape. The outer dimensions in the two directions, X and Y, of the beam section 40e are configured to be the same as the outer dimensions in the two directions, X and Y, of the beam section 40a of the embodiment. The beam section 40e of Reference Example 3 is configured to have an outer dimension in the Z direction shorter than the other beam sections 40a to 40d.

[0043] The workpieces W were set in five types of heat treatment jigs each having the beam portions 40a to 40e of the above-mentioned Example, Comparative Example, and Reference Examples 1 to 3, and then the workpieces W were loaded into a carburizing furnace and carburized under the heat treatment conditions shown in Fig. 14. Fig. 14 is a diagram showing the heat treatment conditions using the heat treatment jig according to the first embodiment. As shown in Fig. 14, the carburization process applied to this embodiment includes a heating process in step S1, a carburizing process in step S2, a quenching process in step S3, and an air-cooling process in step S4.

[0044] The operation of each process was as follows: the inside of the carburizing furnace was heated at room temperature until it reached 950°C in 4320-5280 seconds (step S1), and then the carburizing was performed by holding the temperature at 950°C for 10800-13200 seconds (T1-T2) (step S2). After that, the temperature was lowered to 130°C by oil cooling in 240 seconds (T2-T3) (step S3), and further, it was air-cooled to room temperature of 20°C in 500 seconds (T3-T4) (step S4). Then, the stress and deformation due to temperature change were investigated for the five types of heat treatment jigs that had been subjected to the carburizing treatment.

[0045] Next, referring to FIG. 15 and FIG. 16, the principal stress generated in each heat treatment jig will be described. FIG. 15 is a diagram showing the calculation result of the principal stress generated in the heat treatment jig according to the first embodiment. FIG. 16 is a graph comparing the principal stress difference generated at the intersection of the heat treatment jig according to the first embodiment. FIG. 15 and FIG. 16 show the principal stress difference generated at the completion of heating to 950°C by heating and the principal stress difference generated at the completion of cooling to 20°C by cooling under the heat treatment conditions shown in FIG. 14. Also, as shown in FIG. 15, the location where the principal stress is generated is the intersection 60 where the support body 31 and each beam part 40a to 40e are connected. The numerical values ​​described in FIG. 15 and FIG. 16 show the difference between the maximum principal stress and the minimum principal stress generated at the intersection 60 calculated as the principal stress difference. The maximum principal stress is mainly a positive value and represents a tensile stress. On the other hand, the minimum principal stress is mainly a negative value and represents a compressive stress. Therefore, the greater the difference between the maximum principal stress and the minimum principal stress at a certain point (principal stress difference), the more likely defects such as cracks will occur around that point.

[0046] The principal stress difference calculated in this manner was 206 MPa at the completion of the heating in the comparative example, and 300 MPa at the completion of the cooling. In the example, the principal stress difference was 102 MPa at the completion of the heating, and 292 MPa at the completion of the cooling. In Reference Example 1, the principal stress difference was 190 MPa at the completion of the heating, and 680 MPa at the completion of the cooling. In Reference Example 2, the principal stress difference was 177 MPa at the completion of the heating, and 655 MPa at the completion of the cooling. In Reference Example 3, the principal stress difference was 120 MPa at the completion of the heating, and 414 MPa at the completion of the cooling.

[0047] Next, the deformation amount of each beam portion 40a to 40e will be described with reference to FIG. 17 and FIG. 18. FIG. 17 is a diagram for explaining the deformation amount difference in the beam portion of the heat treatment jig according to the first embodiment. FIG. 18 is a graph comparing the deformation amount difference in the beam portion of the heat treatment jig according to the first embodiment. As shown in FIG. 17, the beam portion 40 subjected to the carburizing treatment is distorted due to thermal expansion according to the temperature change of the carburizing treatment. Therefore, the difference between the maximum value δ2 and the minimum value δ1 of the height along the Z direction of each beam portion 40a to 40e was calculated as the deformation amount difference. The deformation amount difference calculated in this way was 0.065 mm in the comparative example, 0.047 mm in the embodiment, 0.118 mm in the reference example 1, 0.124 mm in the reference example 2, and 0.063 mm in the reference example 3.

[0048] Next, the results of comparing the principal stress difference and deformation amount difference obtained as described above among the Example, the Comparative Example, and Reference Examples 1 to 3 with the Comparative Example as a reference will be described with reference to Fig. 19. Fig. 19 is a diagram showing the rate of increase / decrease of the principal stress difference and the deformation amount difference.

[0049] The principal stress difference occurring at the completion of the temperature rise was lower than that of the comparative example in all of the embodiment and reference examples 1 to 3. When comparing the rate of increase or decrease with the comparative example, with the principal stress difference occurring in the beam portion 40b of the comparative example at the completion of the temperature rise set as the standard (zero), the embodiment showed the largest decrease of 50%, Reference example 1 showed an 8% decrease, Reference example 2 showed a 14% decrease, and Reference example 3 showed a 42% decrease.

[0050] On the other hand, the principal stress difference occurring at the completion of cooling was lower in the Example than in the Comparative Example, but higher in Reference Examples 1 to 3 than in the Comparative Examples. When comparing the rate of increase or decrease with the Comparative Examples, with the principal stress difference occurring in the beam portion 40b of the Comparative Example at the completion of cooling set as the base (zero), the Example decreased by 3%, Reference Example 1 increased by 127%, Reference Example 2 increased by 118%, and Reference Example 3 increased by 38%.

[0051] Furthermore, the deformation difference was smaller in the Example and Reference Example 3 than in the Comparative Example, but was larger in Reference Examples 1 and 2 than in the Comparative Example. When comparing the rate of increase or decrease with the deformation difference in the beam portion 40b of the Comparative Example set as the base (zero), the decrease was the largest in the Example, at 28%, while it was only a 3% decrease in Reference Example 3. Also, it increased by 82% in Reference Example 1, and by 91% in Reference Example 2.

[0052] Here, when a beam structure is provided to impart strength and durability to the heat treatment jig, the shape of the beam portion 40e of Reference Example 3, which is simply a rectangular prism, is considered. However, the beam portion 40e is large in size, and the volume difference between the beam portion 40e and the support body 31 to which the beam portion 40e is connected becomes large. If this volume difference is large, the temperature difference between the beam portion 40e and the support body 31 increases during heating, and the amount of expansion of the beam portion 40e increases. Furthermore, the thermal stress generated in the intersection portion 60 during heating and cooling also increases, and this thermal stress exceeds the yield stress. As a result, such beam portion 40e is prone to defects such as deformation and cracks due to heat.

[0053] In order to reduce this volume difference, various shapes that reduce the volume of the beam portion 40 can be considered. However, even if the heat treatment jig has the shape of the beam portion 40b of the comparative example, the volume of the beam portion 40b is still large, and defects such as cracks often occur at the intersection 60. Fig. 20 is a diagram showing a state in which a crack has occurred in the heat treatment jig of the comparative example. In Fig. 20, a crack C has occurred at the connection end (around the intersection 60) of the second rib portion 44a of the beam portion 40b.

[0054] On the other hand, the beam portion 40a of Example 1 is lighter and smaller in volume than the beam portion 40b of the comparative example. In other words, the beam portion 40a is configured to have a small volume difference between the beam portion 40a and the support body 31 to which the beam portion 40a is connected. With this configuration, the temperature difference between the beam portion 40a and the support body 31 is reduced during heating, and the amount of expansion of the beam portion 40a is reduced. Furthermore, the thermal stress generated in the intersection portion 60 during heating and cooling is also reduced.

[0055] Furthermore, a heat treatment jig including the beam portion 40b of the comparative example and a heat treatment jig including the beam portion 40a of the embodiment were subjected to multiple cycles of carburizing treatment under the heat treatment conditions shown in FIG. 14, and the jig life until crack C occurred was compared. As a result, crack C occurred in the beam portion 40b of the comparative example at the 99th cycle of carburizing treatment, as shown in FIG. 20. In contrast, the beam portion 40a of the embodiment was able to extend the jig life until the 137th cycle of carburizing treatment. In this way, reducing the thermal stress and thermal expansion occurring in parts of the heat treatment jig where defects such as deformation and crack C are likely to occur is effective in improving the strength and durability of the heat treatment jig.

[0056] As described above, the heat treatment jig according to this embodiment holds the workpiece W between the support columns 30 erected on the base tray 10, and at least one beam portion 40a is provided between adjacent support columns 30, thereby imparting strength to the heat treatment jig. The beam portion 40a has a first rib portion 41 formed continuously from one adjacent support column 30 to the other adjacent support column 30. Furthermore, the beam portion 40a has a second rib portion 42 formed intermittently between one support column 30 and the other support column 30. The second rib portion 42 is provided at least above or below the first rib portion 41, and is connected to the first rib portion 41 via a connecting column 43. The width of the second rib portion 42 is configured to be narrower than the width of the first rib portion 41.

[0057] In this way, by providing the beam portion with a rib structure formed intermittently and configuring it to have the desired strength, it is possible to reduce the volume of the beam portion while ensuring its strength. This reduces the volume difference between the beam portion and the support portion to which the beam portion is connected, thereby suppressing the expansion of the member due to heating and reducing the principal stress difference associated with thermal stress occurring in areas where cracks and the like are likely to occur. This therefore suppresses the occurrence of defects such as deformation and cracks due to heat, improves the strength and durability of the heat treatment jig, and extends the jig's lifespan.

[0058] For example, as in Patent Document 1, when a heat treatment jig is made using a C / C composite, which is a porous material containing many pores, if the workpiece after heat treatment is immersed in oil together with the heat treatment jig and quenched, the oil penetrates and remains in the pores of the C / C. If the heat treatment jig with the oil remaining is used in the next cycle, the oil may carbonize during the heat treatment and have adverse effects such as adhesion of foreign matter to the product.

[0059] In contrast, the heat treatment jig according to the present embodiment does not have the above-mentioned problems caused by using a special and expensive material such as a C / C composite, and the strength and durability of the heat treatment jig can be improved by devising the shape. In addition, additional processing such as surface treatment is not required. According to the heat treatment jig according to the present embodiment, the shape is designed taking into consideration not only the rigidity of the heat treatment jig but also the thermal stress generated in the heat treatment jig, thereby improving the jig life.

[0060] 10 Base Tray 11 Outer Frame 12 Support slots 13 Engagement hole 20 Support Unit 21 Bottom 22 Outer Frame 23 Support slots 24, 33, 46 void 25 Engagement part 30 Support section 31, 31a, 31b, 31c Post body 32 Arm 32a Convex part 34, 36 End 35 Central part 40, 40a, 40b, 40c, 40d, 40e Beam section 41 First rib section 42, 42a, 42b, 42c, 42d, 42e, 42f, 42g Second rib section 43, 43a, 43b, 43c, 43d, 43e, 43g, 43h connecting column 44a, 44b Second rib portion 45a Thick wall part 45b Thin wall part 50 Work holding part 51 Work holding unit body 52 Insertion section 53 Auxiliary part 54a, 54b, 54c groove 55 Work retaining part 56 Latch part 60 Intersection C Crack Double work

Claims

[Claim 1] At least two support columns erected on the base tray; At least one beam portion connecting adjacent support portions; A workpiece holding portion that connects the support portions to each other and holds a workpiece, The beam portion is A first rib portion; a second rib portion provided at least one above or below the first rib portion, the second rib portion having a narrower width than the first rib portion, and connected to the first rib portion; The second rib portion is formed intermittently between one of the support pillar portions to which the beam portion is connected and the other support pillar portion, and one end is connected to the first rib portion via the support pillar portion or one connecting pillar, and the other end is connected to the first rib portion via another connecting pillar.

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