Fixtures for heat treatment and heat treatment methods

Abstract

To provide a jig for heat treatment and a heat treatment method that can support a metal plate without unnecessary restraint. [Solution] The plate is restrained in such a way that displacement is allowed in a direction parallel to the periphery of the plate, but displacement is prevented in a direction perpendicular to it, and then heat treatment is performed.

Description

Technical Field

[0001] The following disclosure relates to a jig and a heat treatment method for subjecting a flat plate to heat treatment after forming, and more particularly to a jig and a heat treatment method that can appropriately cope with the expansion and contraction of the plate accompanying the heat treatment.

Background Art

[0002] For forming a metal plate such as a thin steel plate, conventionally, pressing, bending, or ironing has been used, and as a relatively recent method, sequential forming such as die-less forming has been studied. In any method, heat treatment such as annealing may be additionally performed for the purpose of adjusting material changes such as hardening and residual stress caused by processing.

[0003] During heat treatment, expansion and contraction naturally occur due to temperature changes, and deformation also occurs due to the release of residual stress. As a result of stress due to expansion, contraction, or deformation concentrating on a specific part, secondary deformation that cannot be repaired such as buckling may occur. In order to prevent unintended deformation, it is necessary to appropriately support the formed metal plate. Patent Document 1 discloses a method using a correction jig.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Since the correction jig does not expand thermally in the same way as the metal plate, it often forces unnecessary deformation on the metal plate. The heat treatment using a correction jig has a limited effect despite a non-negligible cost burden, and moreover, it can be said that there is a concern about a decrease in surface quality. The technology disclosed below was conceived in view of such problems. [Means for solving the problem]

[0006] The plate is constrained in such a way that displacement is allowed in a direction parallel to the periphery of the plate, but displacement is prevented in a direction perpendicular to it, and then heat treatment is performed. [Effects of the Invention]

[0007] This allows for the support of metal plates without unnecessary restraint, preventing unintended deformation and damage. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic perspective view of the jig and the formed flat plate. [Figure 2] Figure 2 is a schematic perspective view of a jig and a flat plate in an example where the jig is divided into multiple parts, each allowing for displacement. [Figure 3] Figure 3 is a schematic cross-sectional elevation view of a jig and a flat plate supported by the jig that has undergone molding, where (a) shows the state after molding and (b) shows the heat treatment process. [Figure 4] Figure 4 is a schematic cross-sectional elevation view of a jig and a flat plate in an example where a low-friction coating is used for support. [Figure 5] Figure 5 is a schematic cross-sectional elevation view of a jig and a flat plate in an example where a rotating body is used for support. [Figure 6] Figure 6 is a schematic cross-sectional elevation view of a jig and a flat plate in an example of support using a controllable gap. [Figure 7] Figure 7 is a schematic cross-sectional elevation view of a jig and a flat plate, in which an example is provided with both a fixing means and a restraining means that allows in-plane displacement, where (a) shows the configuration during the molding stage and (b) shows the configuration during the heat treatment stage. [Figure 8] Figure 8 is a schematic cross-sectional elevation view of a jig and a flat plate according to another example, which includes both a fixing means and a restraining means that allows in-plane displacement, where (a) represents the configuration during the molding stage and (b) represents the configuration during the heat treatment stage. [Figure 9] Figure 9 is a schematic partial cross-sectional elevation view illustrating an example where jig displacement is permitted. [Modes for carrying out the invention]

[0009] Several exemplary embodiments are described below with reference to the attached drawings. Particular attention should be paid to the fact that the drawings are not necessarily to scale, and therefore the dimensional relationships are not limited to those shown. Throughout the following description and the attached claims, and for the sake of explanatory convenience, we will distinguish between top and bottom, but embodiments in which the structure can be arbitrarily inverted, rotated, and reversed are possible.

[0010] Referring mainly to Figures 1 and 3(a), a flat plate 3 made of a metal such as steel is supported by a jig and subjected to forming such as die-less forming, and for example, has a formed portion 5 that is recessed downwards near its center. The jig is, for example, a pair of frames A and B, which supports the flat plate 3 by sandwiching its periphery from both sides. Needless to say, Figures 1 and 3(a) are merely illustrative, and the formed portion can be of various shapes, and the formed portion is not limited to one, but can be two or more, continuous or discontinuous with respect to each other.

[0011] The flat plate 3 having the molded portion 5 is subjected to a heat treatment such as annealing, together with the frame pair 1, as shown in Figure 3(b). Preferably, the frame pair is the same during molding and heat treatment, or it may be replaced as appropriate during heat treatment. Heating is performed, for example, by introducing the object into an atmosphere furnace 7 and exposing the flat plate 3 to thermal radiation H using a heating means 9 such as a ceramic heater. Of course, heating may be carried out in an open atmosphere without using a furnace, and heating can be performed by induction heating, exposure to hot air or flame, contact heating, etc., rather than thermal radiation from a heater, or by a combination of two or more of these.

[0012] During the heating process, the plate 3 expands and contracts, and residual stresses are released, resulting in displacements d in various directions. Our studies have shown that even if the plate 3 is restrained as a whole, the desired effect cannot be achieved, and that restraining the area around the molded portion 5 is more important. In particular, restricting displacement in a direction parallel to the periphery of the plate 3 leads to stress concentration in unexpected locations, causing undesirable secondary deformations such as buckling. Similarly, insufficient restraint in the direction perpendicular to the periphery also tends to result in undesirable deformations. Therefore, it is preferable that the restraint by the frame pair 1 allows displacement df in the direction parallel to the periphery of the plate 3, while preventing or limiting displacement dv in the direction perpendicular to the periphery.

[0013] One restraining means that makes such restraint possible is shown in Figure 4, for example. That is, frames A and B may consist of frame bodies 11a and 11b, respectively, covered with low-friction coatings 13a and 13b. The low-friction coatings 13a and 13b cover at least the surfaces of the frame bodies 11a and 11b facing the periphery of the flat plate 3, and allow a displacement df in a direction parallel to the periphery of the flat plate 3. Needless to say, the low-friction coatings 13a and 13b may also cover other surfaces. Any material that has sufficient heat resistance while reducing the coefficient of friction can be used for the low-friction coatings 13a and 13b, and examples of such materials include fluororesin, nylon, polyacetal, diamond-like carbon, and diamond. A mixture of two or more of these may also be used. With the low-friction coatings 13a and 13b, the flat plate 3 can be restrained in a direction perpendicular to the surface while allowing a displacement df in the surface direction.

[0014] Alternatively, instead of or in addition to the low-friction coating, a support utilizing rotating bodies 15a and 15b, as illustrated in Figure 5, may be used. The rotating bodies 15a and 15b are embedded in the frame bodies 11a and 11b, respectively, and can rotate R in all directions, thereby constraining the flat plate 3 in the vertical direction while allowing displacement df. To facilitate rotation R, a smaller rotating body may be interposed between the rotating bodies 15a and 15b and the frame bodies 11a and 11b, or a low-friction coating may be used instead of or in addition to the small rotating body. Such a support is available on the market under names such as ball transfer unit, but is not limited to this. The rotating bodies 15a and 15b can also constrain the flat plate 3 in the direction perpendicular to the surface while allowing displacement df in the surface direction.

[0015] Alternatively, or in addition to, the means illustrated in Figures 4 and 5, a similar effect can be achieved by maintaining a gap between the frame bodies 11a and 11b and the flat plate 3, as shown in Figure 6. For example, a ball screw or hydraulic actuator can be used to cause a controllable vertical movement V in the frame bodies 11a and 11b, maintaining an appropriate gap with respect to the flat plate 3. Since there is no friction in the plane direction due to the gap, a displacement df can be tolerated, and if the gap is sufficiently small, the displacement in the direction perpendicular to the plane can also be sufficiently limited.

[0016] The frame pair 1 composed of frames A and B may further include means for fixedly restraining the flat plate 3 in addition to means for restraining the flat plate 3 while allowing displacement df in the plane direction. That is, as shown in FIG. 7, for example, the frames A and B each include, in addition to frame bodies 11a and 11b provided with rotators 15a and 15b, clamp bodies 17a and 17b for fixedly supporting. For example, using a ball screw or a hydraulic actuator, the frame bodies 11a and 11b and the clamp bodies 17a and 17b can be independently moved up and down. As shown in FIG. 7(a), if the clamp bodies 17a and 17b are pressed against the flat plate 3, the flat plate 3 is fixed by the frame pair 1 and becomes immovable both in the plane direction and in the direction perpendicular to the plane. As shown in FIG. 7(b), if only the frame bodies 11a and 11b are pressed against the flat plate 3 and the clamp bodies 17a and 17b are moved away from the flat plate 3 as indicated by arrows M1a and M1b, the frame pair 1 can restrain the flat plate 3 in the direction perpendicular to the plane while allowing displacement df in the plane direction. For example, molding can be performed in the state of FIG. 7(a) and heat treatment can be performed in the state of FIG. 7(b). Therefore, according to the present embodiment, it is advantageous to perform both molding and heat treatment without replacing the frame pair 1.

[0017] Alternatively, the configuration illustrated in Figure 8 is also possible. Instead of having independent clamping bodies, the frame pair 1 has fixed surfaces 19a and 19b that restrain the flat plate 3 in the in-plane direction, and restraining means that allow in-plane displacement at a portion away from the fixed surfaces. In the example in Figure 8, the latter means are rotating bodies 15a and 15b, but these may be replaced with, or in addition to, the low-friction coating or gaps already described. Furthermore, the surface having the restraining means may be configured to form a certain angle with respect to the former fixed surface, as in the example in Figure 8, and to be rotatable. As shown in Figure 8(a), when the fixed surfaces are pressed against the flat plate 3, the flat plate 3 is fixed by the frame pair 1. As shown in Figure 8(b), by using appropriate actuators to rotate the frame bodies 19a and 19b as indicated by arrows M2a and M2b, the fixed surfaces separate from the flat plate 3, and instead, the restraining means that allow displacement come into contact with the flat plate 3. Thus, the frame pair 1 can restrain the flat plate 3 in a direction perpendicular to the surface while allowing displacement df in the surface direction. For example, molding can be performed in the state shown in Figure 8(a), and heat treatment can be performed in the state shown in Figure 8(b). Therefore, according to this embodiment, it is advantageous to perform both molding and heat treatment without replacing the frame pair 1.

[0018] Furthermore, as illustrated in Figure 9, the frames A and B themselves may be movable in the planar direction. Unlike the above description, for example, frames A and B may directly contact and support the flat plate 3 without being equipped with means such as a low-friction coating. Alternatively, an anti-slip or other appropriate means may be interposed between them. Furthermore, frames A and B are supported by displacement means such as supports 21a and 21b equipped with rotating bodies 23a and 23b, respectively, thereby allowing displacement of the frame pair 1 in the planar direction. Frames A and B may be moved in accordance with the displacement of the flat plate 3, or they may be actively displaced by an external power source. In this way, the frame pair 1 can restrain the flat plate 3 in a direction perpendicular to the planar direction while allowing displacement df in the planar direction.

[0019] The frame pair 1 does not necessarily have to be a pair as shown in FIG. 1, and may be divided according to the displacement means as shown in FIG. 2. That is, the frame pair 1 is composed of divided frame pairs 1a, 1b, 1c, 1d, ···, each of which includes frames A1, B1, A2, B2, A3, B3, A4, B4, ···, and independently supports the periphery of the flat plate 3. Each has displacement means as exemplified in FIG. 9 and can be displaced independently as shown by arrows D1, D2, D3, D4, ···. In this way, even if the displacement of the flat plate 3 is locally large, the frame supporting the corresponding part can follow it. No locally large stress occurs in the flat plate 3, and no secondary deformation such as buckling occurs.

[0020] According to any of the above embodiments, the displacement due to the expansion / contraction of the flat plate 3 and the release of the residual stress is allowed by the jig, while the restraint by the jig in the direction perpendicular to the surface of the flat plate 3 is sufficient. Therefore, no secondary deformation such as buckling occurs in the flat plate 3. Before and after the heat treatment, the metal plate can be supported without unnecessary restraint, and the occurrence of unintended deformation and scratches can be prevented.

[0021] Although several embodiments have been described, it is possible to modify or deform the embodiments based on the above disclosure.

Industrial Applicability

[0022] There is provided a jig and a heat treatment method that can support a metal plate without unnecessary restraint and prevent the occurrence of unintended deformation and scratches.

Explanation of Reference Numerals

[0023] 1 Frame pair 1a, 1b, ·· Blocks 3 Flat plate 5 Forming part 7 Furnace 9 Heater 11a, 11b Frame body [[ID=३५]] 13a, 13b Coating 15a, 15b Rotating body 17a, 17b Clamp body 19a, 19b Frame body 21a,21b Support 23a, 23b Solids of revolution A,B,A1,B1,A1,B1, Frame d, df, dv displacement H Thermal radiation M1a, M1b Vertical motion M2a, M2b Rotation R rotation V Vertical motion

Claims

1. A jig for subjecting a molded flat plate to heat treatment, A pair of frames that sandwich the periphery of the flat plate, each of which is equipped with a restraining means that allows displacement of the periphery in a direction parallel to the periphery but restrains the periphery in a direction perpendicular to it. A jig equipped with the following features.

2. The jig according to claim 1, wherein the restraining means is a low-friction coating that covers the peripheral-facing surface of the frame pair.

3. The jig according to claim 2, wherein the low-friction coating is made of one or more of the following: fluororesin, nylon, polyacetal, diamond-like carbon, and diamond.

4. The jig according to claim 1, wherein the restraining means is a rotating body that can rotate in all directions.

5. The fixture according to claim 1, wherein the restraining means is a controllable gap relative to the periphery.

6. The jig according to claim 1, wherein the restraining means is one or more displacement means that allow displacement of the frame pair in a direction parallel to the periphery.

7. The jig according to claim 6, wherein the pair of frame bodies are divided according to the displacement means and each is configured to be displaced independently.

8. The jig according to claim 1, wherein the pair of frame bodies further comprises a fixing surface that restrains the periphery in a direction parallel to the periphery.

9. A method for annealing a formed flat plate, The periphery of the flat plate is supported by one or more pairs of frames such that displacement of the periphery is permitted in a direction parallel to the periphery, but the periphery is constrained in a direction perpendicular to it. The supported flat plate is heat-treated. A method to prepare for that.

10. In the aforementioned frame pair, the surface facing the periphery is pre-coated with a low-friction coating. The method of claim 9, further comprising the above.

11. The method of claim 10, wherein the low-friction coating is made of one or more of the following: fluororesin, nylon, polyacetal, diamond-like carbon, and diamond.

12. In the aforementioned pair of frame bodies, a rotating body that can rotate in all directions is interposed in advance on the surface facing the periphery. The method of claim 9, further comprising the above.

13. In the frame pair, a gap is maintained between the surface facing the periphery and the periphery. The method of claim 9, further comprising the above.

14. The method of claim 9, wherein in the heat treatment step, the pair of frame bodies is supported such that displacement of the pair of frame bodies is permitted in a direction parallel to the periphery.

15. The method according to claim 14, wherein the frame pairs are divided and each frame pair is supported so as to be displaced independently.

16. The method of claim 9, wherein the pair of frame bodies further comprises a fixing surface that restrains the periphery in a direction parallel to the periphery.

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