Evaluation method for the cooling process of heat treatment

Abstract

To provide a method for evaluating a cooling step of heat treatment capable of uniformizing the cooling even if a shape of a workpiece is complicated.SOLUTION: A method for evaluating a cooling step of heat treatment includes the steps of: sticking one pressure sensor sheet on a first surface and a second surface which come into contact with each other and intersect with each other in a work-piece: and bending the pressure sensor sheet between a first portion stuck on the first surface and a second portion stuck on the second surface; and measuring the pressure distribution of a cooling medium by the pressure sensor sheet while jetting the cooling medium to the work-piece.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] An embodiment of the present invention relates to a method for evaluating a cooling step of a heat treatment. [Background technology]

[0002] There are heat treatment devices that use a heating section and a cooling section to heat treat a workpiece. The cooling section cools the workpiece, for example, by spraying a cooling liquid from around the workpiece. In this case, a cooling jacket is used that surrounds the workpiece and distributes the cooling liquid so that the cooling liquid is sprayed uniformly onto the workpiece.

[0003] In order to perform uniform heat treatment on the region of the workpiece to be heat-treated, it is preferable to uniformly cool the region to be heat-treated. If the workpiece has a simple shape such as a cylinder and the region to be heat-treated is the side surface of the cylinder, it is expected that the region to be heat-treated can be uniformly cooled by uniformly spraying the coolant onto the workpiece. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 51-146274 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the shape of the workpiece is complex, the area to be heat-treated is not necessarily uniformly cooled even if the cooling liquid is sprayed uniformly. In this case, a cooling jacket is made to match the shape of the workpiece, but even if a cooling jacket corresponding to the shape of the workpiece is made, whether the area to be heat-treated is uniformly cooled or not cannot be determined unless the workpiece is actually heat-treated and a sample is taken from the workpiece after heat treatment and evaluated. Even if the heat treatment is non-uniform, it is difficult to determine whether it is due to the non-uniformity of the cooling liquid, and the re-making of the cooling jacket is unavoidable by trial and error. For this reason, heat treatment of a workpiece with a complex shape often requires a lot of time for preparation and has a high initial cost.

[0006] An object of the embodiment is to provide a method for evaluating a cooling process of a heat treatment that can achieve uniform cooling even if the shape of a workpiece is complex. [Means for solving the problem]

[0007] A method for evaluating a cooling process of a heat treatment according to an embodiment of the present invention includes the steps of attaching a pressure sensor sheet to a first surface and a second surface of a workpiece that are in contact with and intersect each other, and bending the pressure sensor sheet between a first portion attached to the first surface and a second portion attached to the second surface, and measuring the pressure distribution of the cooling medium using the pressure sensor sheet while spraying the cooling medium onto the workpiece.

[0008] A method for evaluating a cooling process of a heat treatment according to an embodiment of the present invention includes the steps of attaching a first pressure sensor sheet to a first surface of a workpiece and attaching a second pressure sensor sheet to a second surface of the workpiece, and measuring the pressure distribution of the cooling medium using the first and second pressure sensor sheets while spraying the cooling medium onto the workpiece.

[0009] A method for evaluating a cooling process of a heat treatment according to an embodiment of the present invention comprises the steps of attaching a pressure sensor sheet to a curved area on the surface of a workpiece and curving the pressure sensor sheet along the area, and measuring the pressure distribution of the cooling medium using the pressure sensor sheet while spraying the cooling medium onto the workpiece. Effect of the Invention

[0010] According to an embodiment of the present invention, it is possible to realize a method for evaluating a cooling process of a heat treatment that can achieve uniform cooling even if the shape of a workpiece is complex. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1(a) is a perspective view showing an evaluation method according to a first embodiment, and FIG. 1(b) is a partial cross-sectional view thereof. [Diagram 2] FIG. 2 is an exploded perspective view showing the evaluation method according to the first embodiment. [Diagram 3] FIG. 3 is a graph showing an example of the measurement results of pressure distribution in the first embodiment, with the horizontal axis representing position and the vertical axis representing pressure. [Figure 4] FIG. 4 is a partial cross-sectional view showing a state of the cooling liquid on the workpiece in the first embodiment. [Diagram 5] FIG. 5(a) is a perspective view showing an evaluation method according to the second embodiment, and FIG. 5(b) is a partial cross-sectional view thereof. [Figure 6] FIG. 6 is a partial cross-sectional view showing an evaluation method according to the third embodiment. [Figure 7] FIG. 7(a) is a development view showing the ejection surface of a cooling jacket used in the fourth embodiment, and (b) is a plan view showing a pressure sensor sheet used in the fourth embodiment. [Figure 8] 8(a) to 8(h) are diagrams showing the relationship between the distribution of clogged injection holes on the injection surface formed in the cooling jacket and the pressure distribution of the coolant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <First embodiment> Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The heat treatment of this embodiment has a heating process and a cooling process. In the cooling process, a coolant (e.g., water) is sprayed onto the workpiece to cool it. This embodiment is a method for evaluating the cooling process of the heat treatment by measuring the pressure distribution of the coolant on the surface of the workpiece. Note that the "heat treatment" referred to here is a general term for quenching, annealing, tempering, etc., and includes not only the heating process but also the cooling process.

[0013] FIG. 1(a) is a perspective view showing an evaluation method according to this embodiment, and (b) is a partial cross-sectional view thereof. FIG. 2 is an exploded perspective view showing the evaluation method according to the first embodiment. FIG. 3 is a graph showing an example of the measurement results of pressure distribution in this embodiment, with the horizontal axis representing position and the vertical axis representing pressure. FIG. 4 is a partial cross-sectional view showing the state of the cooling liquid on the workpiece in this embodiment.

[0014] 1(a) and (b), the workpiece 100 used in this embodiment is, for example, a member that will become a wheel of a train. The workpiece 100 is provided with a boss portion 101, a plate portion 102, a rim portion 103, and a flange 104 from the center toward the periphery. A through hole 101a is formed in the boss portion 101. The workpiece 100 is integrally formed from a steel material.

[0015] When the workpiece 100 is used as a wheel of a train, an axle (not shown) is inserted through the through hole 101a. The outer peripheral surface 103a of the rim portion 103 is a tread surface that comes into contact with a rail (not shown). The upper surface 104a of the flange 104 also comes into contact with the rail. The outer peripheral surface 103a of the rim portion 103 and the upper surface 104a of the flange 104 are in contact with each other and also intersect with each other.

[0016] The outer peripheral surface 103a of the rim portion 103 and the upper surface 104a of the flange 104 are the heat treatment planned area 110, and are heat treated to a predetermined depth. However, in this embodiment, the pressure sensor sheet 10 is attached to the workpiece 100 as described later to measure the pressure distribution of the cooling liquid, so the workpiece 100 is not heat treated. Therefore, the heat treatment planned area 110 of the workpiece 100 is not heat treated to become a train wheel. After the evaluation of the cooling process, the pressure sensor sheet 10 may be removed from the workpiece 100 and the workpiece 100 may be heat treated. In this case, the workpiece 100 becomes a train wheel. In addition, a dummy workpiece having the same or similar shape as a train wheel may be used as the workpiece 100. The dummy workpiece may be, for example, a resin molded product. In this specification, such a dummy workpiece is also included in the "workpiece".

[0017] In this embodiment, one pressure sensor sheet 10 is attached to the outer peripheral surface 103a of the rim portion 103 of the workpiece 100 and the upper surface 104a of the flange 104. In the pressure sensor sheet 10, a plurality of pressure sensor elements are arranged two-dimensionally. The plurality of pressure sensor elements are periodically arranged, for example, in a matrix or staggered pattern. Each pressure sensor element measures pressure and outputs the result as an electrical signal. The pressure sensor sheet 10 is connected to a computer (not shown) via a sensor connector (not shown) by wire or wirelessly. The pressure sensor sheet 10 can output the measurement result of each pressure sensor element at a predetermined frequency, for example, 100 times per second. The pressure sensor sheet 10 is bendable.

[0018] The pressure sensor sheet 10 is bent between the first portion 11 attached to the outer peripheral surface 103a of the rim portion 103 and the second portion 12 attached to the upper surface 104a of the flange 104. That is, in the pressure sensor sheet 10, the boundary between the first portion 11 and the second portion 12 forms a bend line 13. In this specification, "bend" means to fold. The curvature along the line from the first portion 11 to the second portion 12 on the surface of the pressure sensor sheet 10 has a large value only in the vicinity of the bend line 13, and has a value close to zero in the portion other than the bend line 13.

[0019] On the other hand, a cooling jacket 50 is prepared as shown in Fig. 2. The cooling jacket 50 has a shape that surrounds the workpiece 100. The cooling jacket 50 has an ejection surface 60 provided with ejection holes 61 for ejecting a cooling liquid. The shape of the cooling jacket 50 is, for example, cylindrical. However, the shape of the cooling jacket 50 is not limited to cylindrical and may be a shape corresponding to the shape of the workpiece. A plurality of injection holes 61 are formed on the injection surface 60.

[0020] An example of the arrangement of the injection holes 61 will be described below. The multiple injection holes 61 are arranged periodically. For example, injection holes 61 arranged in a line along the direction in which the central axis of the injection surface 60 extends (hereinafter also referred to as the "axial direction") form a row 62, and the multiple rows 62 are arranged periodically along the circumferential direction of the injection surface 60. Furthermore, between adjacent rows 62, the positions of the injection holes 61 in the axial direction are shifted by half the arrangement period of the injection holes 61 in the axial direction.

[0021] Next, the workpiece 100 is inserted into the space surrounded by the ejection surface 60. At this time, the workpiece 100 may or may not be rotated. When actually subjecting the workpiece to heat treatment, the workpiece is often rotated in the heating and cooling steps. In this embodiment, when the workpiece 100 is rotated, it is preferable that a sensor connector (not shown) is fixed to the workpiece 100 and the sensor connector and a computer (not shown) are connected wirelessly.

[0022] Next, the cooling liquid is sprayed onto the workpiece 100 through the spray holes 61 of the spray surface 60. The cooling liquid is sprayed almost uniformly from the inner surface of the spray surface 60. The pressure sensor sheet 10 then measures the pressure distribution of the cooling liquid. This makes it possible to measure the pressure distribution of the cooling liquid in the area on the surface of the workpiece 100 where the pressure sensor sheet 10 is affixed, i.e., in a part of the area 110 to be heat-treated.

[0023] For example, assume that the pressure of the cooling liquid is low near the bending line 13 as shown in FIG. 3. In this case, as shown in FIG. 4, the cooling liquid 70 forms a pool 70a near the boundary line 105 between the outer peripheral surface 103a of the rim portion 103 and the upper surface 104a of the flange 104, and the cooling efficiency may be reduced because the contact of the cooling liquid immediately after being sprayed from the spray holes 61 is hindered near the boundary line 105. For this reason, the heat treatment may be insufficient in the portion 106 near the boundary line 105 of the workpiece 100. As a countermeasure in this case, for example, it is possible to adjust the arrangement of the spray holes 61 or the angle at which the cooling liquid is sprayed so that a sufficient amount of cooling liquid hits the vicinity of the boundary line 105.

[0024] According to this embodiment, even if the shape of the workpiece 100 is complex, the pressure distribution of the sprayed coolant can be directly measured in the heat treatment planned region 110 of the workpiece 100. This makes it possible to determine whether or not the cause of poor heat treatment is non-uniform spray of the coolant. Furthermore, when the spray of the coolant is non-uniform, the cooling jacket can be efficiently designed by referring to the measurement result of the pressure distribution.

[0025] In this embodiment, a train wheel is shown as an example of a workpiece, but the workpiece is not limited to this. For example, the workpiece may be a gear, an automobile crankshaft, or a constant velocity joint. The effect of this embodiment is greater when the shape of the workpiece is complex. The same applies to the other embodiments described later.

[0026] In this embodiment, a cooling liquid (e.g., water) is sprayed onto the workpiece to cool it, but the cooling agent is not limited to this. The cooling agent may be a cooling gas (e.g., nitrogen) or a cooling solid (e.g., solid carbon dioxide). In this embodiment, the concept of cooling liquid, cooling gas, and cooling fixation is called a "cooling medium." The same applies to the other embodiments described below.

[0027] <Second embodiment> FIG. 5(a) is a perspective view showing the evaluation method according to this embodiment, and (b) is a partial cross-sectional view thereof.

[0028] As shown in Figures 5(a) and (b), the workpiece 100 used in this embodiment is similar to that in the first embodiment. In this embodiment, the pressure sensor sheet 21 is attached to the outer peripheral surface 103a of the rim portion 103 of the workpiece 100, and the pressure sensor sheet 22 is attached to the upper surface 104a of the flange 104. That is, different pressure sensor sheets are attached to the outer peripheral surface 103a and the upper surface 104a, and the pressure sensor sheet is not bent at the boundary line 105. The configurations of the pressure sensor sheets 21 and 22 are similar to that of the pressure sensor sheet 10 in the first embodiment. However, the pressure sensor sheets 21 and 22 may be unbendable or uncurvable.

[0029] The method of evaluating the cooling process in this embodiment other than the above is the same as that in the first embodiment. That is, while spraying the cooling liquid onto the workpiece 100, the pressure distribution of the cooling liquid is measured by the pressure sensor sheets 21 and 22. According to this embodiment, even if the shape of the workpiece 100 is complex, there is no need to bend the pressure sensor sheet, so there is a high degree of freedom in selecting the pressure sensor sheet. In addition, the pressure sensor sheet is not damaged by bending it. The configuration, operation, and effects of this embodiment other than the above are the same as those of the first embodiment described above.

[0030] <Third embodiment> FIG. 6 is a partial cross-sectional view showing the evaluation method according to this embodiment. 6, the workpiece 200 used in this embodiment has a curved region 201 on its surface. This curved region 201 is a region to be heat-treated 210, and is to be hardened to a predetermined depth. In this specification, "curved" means bent in an arch shape.

[0031] In this embodiment, the pressure sensor sheet 30 is attached to the area 201 of the workpiece 200, and is curved along the area 201. The pressure sensor sheet 30 is flexible and can be curved to a certain extent. The curvature of the surface of the pressure sensor sheet 30 along the cross section shown in FIG. 6 is a substantially uniform value.

[0032] The method of evaluating the cooling process in this embodiment other than the above is the same as that in the first embodiment. That is, while spraying the cooling liquid onto the workpiece 200, the pressure distribution of the cooling liquid is measured by the pressure sensor sheet 30. According to this embodiment, a spatially continuous pressure distribution can be obtained for the curved region 201 of the workpiece 200. The configuration, operation, and effects of this embodiment other than the above are the same as those of the first embodiment described above.

[0033] <Fourth embodiment> This embodiment is a method for evaluating the effect of the state of the cooling jacket on the pressure distribution of the coolant by measuring the pressure distribution of the coolant. FIG. 7(a) is a development view showing the ejection surface of a cooling jacket used in this embodiment, and (b) is a plan view showing a pressure sensor sheet used in this embodiment.

[0034] 7(a), a plurality of injection holes 61 are periodically arranged in the injection surface 60. For example, a plurality of injection holes 61 arranged in a line along the axial direction of the injection surface 60 constitute one row 62, and the plurality of rows 62 are periodically arranged along the circumferential direction of the injection surface 60. In addition, between adjacent rows 62, the positions of the injection holes 61 in the axial direction are shifted by half the arrangement period of the injection holes 61 in the axial direction. The arrangement period of the injection holes 61 in the axial direction of the injection surface 60 is 61C, and the arrangement period of the injection holes 61 in the circumferential direction of the injection surface 60 is 61S.

[0035] 7(b), in the pressure sensor sheet 40 used in this embodiment, a plurality of pressure sensor elements 41 are arranged in a matrix. As in the first embodiment described above, when the workpiece is placed inside the cooling jacket, the arrangement period of the pressure sensor elements 41 in the axial direction of the ejection surface 60 is 41C, and the arrangement period of the pressure sensor elements 41 in the circumferential direction of the ejection surface 60 is 41S.

[0036] In this embodiment, the arrangement period 41C of the pressure sensor elements 41 in the axial direction of the ejection surface 60 is equal to or less than the arrangement period 61C of the ejection holes 61 (equal to or less than half in FIG. 7), and the arrangement period 41S of the pressure sensor elements 41 in the circumferential direction of the cooling jacket 60 is equal to or less than the arrangement period 61S of the ejection holes 61 (equal to or less than half in FIG. 7). That is, 41C≦61C (41C≦61C / 2 in FIG. 7) and 41S≦61S (41S≦61S / 2 in FIG. 7).

[0037] This makes the spatial resolution of the pressure sensor sheet 40 finer than the arrangement period of the injection holes 61, and under certain conditions, it becomes possible to identify the pressure distribution corresponding to each injection hole 61. As a result, for example, it becomes possible to detect clogging of the injection holes 61. In this case, even if the pressure sensor sheet is attached to only a part of the circumferential direction of the workpiece 100, it is possible to obtain the pressure distribution of the entire circumference by outputting pressure measurements at predetermined time intervals while rotating the workpiece 100.

[0038] Furthermore, if the measurement is continued for a certain period of time without rotating the workpiece 100, the change in pressure over time in a specific region can be obtained. This makes it possible to estimate, for example, the behavior of the coolant on the surface of the workpiece 100.

[0039] The method of evaluating the cooling process in this embodiment other than the above is the same as that in the first embodiment. That is, while spraying the cooling liquid onto the workpiece 100, the pressure distribution of the cooling liquid is measured by the pressure sensor sheet 40. The configuration, operation, and effects of this embodiment other than the above are the same as those of the first embodiment described above.

[0040] <Test Example> Next, a test example showing the effect of the fourth embodiment will be described. This test example is for detecting clogging of the injection holes of the cooling jacket. In this test example, some of the injection holes 61 in the injection surface 60 formed in the cooling jacket 50 were intentionally clogged, and the pressure distribution of the coolant was measured. 8(a) to 8(h) are diagrams showing the relationship between the distribution of clogged injection holes on the injection surface formed in the cooling jacket and the pressure distribution of the coolant.

[0041] 8(a)-(d) are diagrams showing the injection surface of the cooling jacket. The vertical direction in FIG. 8(a)-(d) corresponds to the axial direction of the injection surface 60, and the horizontal direction corresponds to the circumferential direction. The dashed lines extending vertically in the diagrams represent rows 62 and do not represent actual shapes. The "x" figures represent injection holes 61x that are intentionally clogged. FIG. 8(e)-(h) are diagrams showing pressure distribution. In FIG. 8(e)-(h), the whiter the area, the higher the pressure. The short line segments extending vertically in FIG. 8(e)-(h) correspond to the dashed lines representing rows 62 shown in FIG. 8(a)-(d). FIG. 8(a)-(h) are scaled to each other.

[0042] In the injection surface 60 shown in Fig. 8(a), all the injection holes 61 are normally open. That is, the coolant is injected from all the injection holes 61. In this case, as shown in Fig. 8(e), the pressure distribution of the coolant is generally uniform, although some fluctuations are observed.

[0043] In the injection surface 60 shown in FIG. 8(b), one injection hole 61x is intentionally clogged. No cooling liquid is injected from the clogged injection hole 61x. In this case, as shown in FIG. 8(f), a region 75 where the pressure is lower than the surroundings is observed. The region 75 is presumed to correspond to the clogged injection hole 61x.

[0044] In the injection surface 60 shown in FIG. 8(c), six injection holes 61x arranged continuously in the axial direction were intentionally clogged. In this case, as shown in FIG. 8(g), a region 76 was observed in which the pressure was lower than the surroundings. The longitudinal direction of the region 76 was the axial direction. The region 76 was presumed to correspond to the clogged injection holes 61x.

[0045] In the injection surface 60 shown in FIG. 8(d), four injection holes 61 arranged in a row along a diagonal direction inclined with respect to both the axial and circumferential directions were intentionally clogged. In this case, as shown in FIG. 8(h), a region 77 was observed where the pressure was lower than the surrounding area. The longitudinal direction of the region 77 was a diagonal direction inclined with respect to both the axial and circumferential directions. The region 77 is presumed to correspond to the clogged injection hole 61x.

[0046] Thus, according to this test example, clogging of the injection holes 61 could be detected based on the pressure distribution of the cooling liquid. In particular, as shown in Figures 8(c) and (d), when multiple injection holes 61 arranged in series were clogged, it was possible to detect it with high accuracy. As a result, clogging of the injection holes 61 can be detected without removing the cooling jacket. Furthermore, even when it is difficult to detect clogging of the injection holes 61 visually, such as when there are a large number of injection holes 61 or when the diameter of the injection holes 61 is small, clogging of the injection holes 61 can be easily detected.

[0047] The above-mentioned heat treatment is preferably a quenching treatment. In the quenching treatment, in the cooling step, the workpiece needs to be quenched at a cooling rate at which martensite is formed, and if clogging of the injection holes 61 occurs as described above, it may be difficult to achieve the cooling rate. Therefore, by applying the evaluation method for the cooling step of the heat treatment according to this embodiment to the quenching treatment, the quenching treatment can be stabilized, which is more preferable.

[0048] The hardening process is, for example, a high-frequency induction heating process. The high-frequency induction heating device has a heating section that heats the workpiece and a cooling section that injects a cooling liquid to cool the workpiece. The heating section and the cooling section may be integrated or separated.

[0049] The above-described embodiments are examples of the present invention, and the present invention is not limited to these embodiments. For example, the present invention also includes the above-described embodiments in which some components are added, deleted, or changed. The above-described embodiments may be implemented in combination with each other. For example, by combining two or more of the first to third embodiments, it is possible to obtain the pressure distribution of the cooling liquid for a workpiece having a more complicated shape. Furthermore, by combining at least one of the first to third embodiments with the fourth embodiment, it is possible to evaluate the effect of each injection hole of the cooling jacket on the pressure distribution in a workpiece having a complicated shape.

[0050] In addition, in the first embodiment, a single pressure sensor sheet is attached to a first surface and a second surface of a workpiece that are in contact with and intersect each other, and the pressure sensor sheet is bent between a first portion attached to the first surface and a second portion attached to the second surface, i.e., a single pressure sensor sheet is attached between two consecutive surfaces and bent between the two surfaces. However, the present invention may also be embodied in a manner in which a single pressure sensor sheet is attached between three consecutive surfaces, such as a U-shaped surface, and bent between the three surfaces.

[0051] In addition, in the second embodiment, a first pressure sensor sheet is attached to a first surface of a workpiece and a second pressure sensor sheet is attached to a second surface of the workpiece, i.e., a pressure sensor sheet is attached to each of two surfaces. However, it may also be implemented in a manner in which a pressure sensor sheet is attached to each of three or more surfaces. [Explanation of symbols]

[0052] 10: Pressure sensor sheet 11:First part 12:Second part 13: Bent line 21, 22, 30, 40: Pressure sensor sheet 41: Pressure sensor element 41C: Arrangement period of pressure sensor elements in the axial direction 41S: Arrangement period of pressure sensor elements in the circumferential direction 50: Cooling jacket 60: Injection surface 61: Injection hole 61C: Arrangement period of injection holes in the axial direction 61S: Circumferential arrangement period of injection holes 61x: Clogged nozzle 62: Column 70:Cooling liquid 70a: Reservoir 75, 76, 77: Area 100: Work 101: Boss Department 101a: Through hole 102: Board part 103: Rim section 103a: Outer surface 104: Flange 104a:Top surface 105: Borderline 106: Part 110: Heat treatment area 200: Work 201: Curved Area 210: Heat treatment area

Claims

1. a step of attaching a pressure sensor sheet to a first surface and a second surface of a workpiece, the first surface and the second surface being in contact with each other and intersecting each other, and bending the pressure sensor sheet between a first portion attached to the first surface and a second portion attached to the second surface; a step of measuring a pressure distribution of the cooling medium by the pressure sensor sheet while spraying the cooling medium onto the workpiece; The method for evaluating a cooling process of a heat treatment comprising:

2. A step of attaching a first pressure sensor sheet to a first surface of a workpiece and attaching a second pressure sensor sheet to a second surface of the workpiece; a step of measuring a pressure distribution of the cooling medium by the first and second pressure sensor sheets while spraying the cooling medium onto the workpiece; Equipped with A method for evaluating a cooling step of a heat treatment, wherein the second surface is in contact with and intersects with the first surface.

3. The cooling medium is injected through a plurality of injection holes of a cooling jacket in which a plurality of injection holes are periodically arranged, 3. The method for evaluating a cooling process in a heat treatment according to claim 1, wherein an arrangement period of the pressure sensor elements of the pressure sensor sheet is equal to or less than an arrangement period of the plurality of injection holes.

4. 4. The method for evaluating a cooling step in a heat treatment according to claim 1, wherein the workpiece is rotated in the step of measuring the pressure distribution of the cooling medium.

5. 4. The method for evaluating a cooling step in a heat treatment according to claim 1, wherein the workpiece is not rotated in the step of measuring the pressure distribution of the cooling medium.

6. 6. The method for evaluating a cooling step in a heat treatment according to claim 1, wherein the cooling medium is a cooling liquid.

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