JP7611033B2 - Evaluation method for the cooling process of heat treatment - Google Patents

Description

An embodiment of the present invention relates to a method for evaluating the cooling process of heat treatment.

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 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 evenly onto the workpiece.

In order to apply uniform heat treatment to the area of the workpiece to be heat-treated, it is preferable to cool the area to be heat-treated uniformly. If the workpiece has a simple shape, such as a cylinder, and the area to be heat-treated is the side surface of the cylinder, it is expected that the area to be heat-treated can be uniformly cooled by spraying the coolant uniformly onto the workpiece.

Japanese Unexamined Patent Publication No. 51-146274

However, if the shape of the workpiece is complex, spraying the cooling liquid evenly does not necessarily result in uniform cooling of the area to be heat treated. In this case, a cooling jacket is made to match the shape of the workpiece, but even if a cooling jacket is made to match the shape of the workpiece, whether the area to be heat treated is uniformly cooled cannot be determined until the workpiece is actually heat treated and samples are taken from the workpiece after heat treatment and evaluated. Furthermore, even if the heat treatment is non-uniform, it is difficult to determine whether this is due to non-uniformity of the cooling liquid, and remaking the cooling jacket must be done by trial and error. For this reason, heat treatment of workpieces with complex shapes often requires a lot of time for preparation and high initial costs.

The purpose of the embodiment is to provide a method for evaluating the cooling process of heat treatment that can achieve uniform cooling even when the workpiece has a complex shape.

A method for evaluating the 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.

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

A method for evaluating the cooling process of a heat treatment according to an embodiment of the present invention includes a step 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 a step of measuring the pressure distribution of the cooling medium using the pressure sensor sheet while spraying the cooling medium onto the workpiece.

According to an embodiment of the present invention, it is possible to realize a method for evaluating the cooling process of heat treatment that can achieve uniform cooling even when the shape of the workpiece is complex.

FIG. 1A is a perspective view showing an evaluation method according to a first embodiment, and FIG. 1B 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 the first 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 the first embodiment. FIG. 5A is a perspective view showing an evaluation method according to the second embodiment, and FIG. 5B is a partial cross-sectional view thereof. FIG. 6 is a partial cross-sectional view showing an evaluation method according to the third embodiment. FIG. 7A is a development view showing the ejection surface of a cooling jacket used in the fourth embodiment, and FIG. 7B is a plan view showing a pressure sensor sheet used in the fourth embodiment. 8A to 8H 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.

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 term "heat treatment" here is a general term for quenching, annealing, tempering, etc., and includes not only the heating process but also the cooling process.

FIG. 1A is a perspective view showing an evaluation method according to this embodiment, and FIG. 1B 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.

As shown in Figs. 1(a) and (b), the workpiece 100 used in this embodiment is, for example, a member that will become the wheels 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.

When the workpiece 100 is used as a train wheel, an axle (not shown) is inserted through the through hole 101a. The outer peripheral surface 103a of the rim portion 103 is the 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.

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 below 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".

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.

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 portions other than the bend line 13.

2, a cooling jacket 50 is prepared. The cooling jacket 50 has a shape that surrounds the workpiece 100. The cooling jacket 50 has an injection surface 60 provided with injection holes 61 for injecting a cooling liquid.
The cooling jacket 50 has a cylindrical shape, for example. However, the shape of the cooling jacket 50 is not limited to a cylindrical shape and may have a shape corresponding to the shape of the workpiece. A plurality of injection holes 61 are formed on the injection surface 60.

Below, an example of the arrangement of the injection holes 61 will be described. 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 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.

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 on its axis. When actually subjecting the workpiece to heat treatment, the workpiece is often rotated on its axis during the heating and cooling processes. In this embodiment, when the workpiece 100 is rotated on its axis, it is preferable that a sensor connector (not shown) is fixed to the workpiece 100 and the sensor connector and computer (not shown) are connected wirelessly.

Next, 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 portion of the planned heat treatment area 110.

For example, as shown in FIG. 3, assume that the pressure of the cooling liquid is low near the bend line 13. In this case, as shown in FIG. 4, the cooling liquid 70 forms a pool 70a near the boundary line 105 between the outer circumferential surface 103a of the rim portion 103 and the upper surface 104a of the flange 104, and it is possible that the contact of the cooling liquid immediately after being sprayed from the spray hole 61 near the boundary line 105 is hindered, resulting in a decrease in cooling efficiency. For this reason, there is a possibility that the heat treatment will 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 hole 61 or the angle at which the cooling liquid is sprayed so that sufficient cooling liquid hits the vicinity of the boundary line 105.

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 intended heat treatment area 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, if the spray of the coolant is non-uniform, the cooling jacket can be efficiently designed by referring to the measurement results of the pressure distribution.

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 below.

In addition, in this embodiment, a cooling liquid (e.g., water) is shown as being 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." This also applies to the other embodiments described below.

Second Embodiment
FIG. 5A is a perspective view showing the evaluation method according to this embodiment, and FIG. 5B is a partial cross-sectional view thereof.

As shown in Figures 5(a) and (b), the workpiece 100 used in this embodiment is the same as that in the first embodiment. In this embodiment, a pressure sensor sheet 21 is attached to the outer peripheral surface 103a of the rim portion 103 of the workpiece 100, and a pressure sensor sheet 22 is attached to the upper surface 104a of the flange 104. In other words, separate 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 configuration of the pressure sensor sheets 21 and 22 is the same as that of the pressure sensor sheet 10 in the first embodiment. However, the pressure sensor sheets 21 and 22 may be unbendable or uncurvable.

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 the selection of the pressure sensor sheet. In addition, bending the pressure sensor sheet will not damage it. The configuration, operation, and effects of this embodiment other than the above are the same as those of the first embodiment described above.

Third Embodiment
FIG. 6 is a partial cross-sectional view showing the evaluation method according to this embodiment.
As shown in Fig. 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.

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

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.

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. 7A is a development view showing the ejection surface of a cooling jacket used in this embodiment, and FIG. 7B is a plan view showing a pressure sensor sheet used in this embodiment.

As shown in FIG. 7(a), multiple injection holes 61 are periodically arranged on the injection surface 60. For example, multiple injection holes 61 arranged in a line along the axial direction of the injection surface 60 constitute one row 62, and the multiple rows 62 are periodically arranged 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. 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.

As shown in FIG. 7(b), in the pressure sensor sheet 40 used in this embodiment, multiple 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.

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

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 portion of the circumference of the workpiece 100, the pressure distribution around the entire circumference can be obtained by outputting pressure measurements at a predetermined time interval while rotating the workpiece 100.

In addition, if measurements are continued for a certain period of time without rotating the workpiece 100, the change in pressure over time in a specific area can be obtained. This makes it possible to estimate, for example, the behavior of the cooling liquid on the surface of the workpiece 100.

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.

<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.
8A to 8H 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.

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

In the injection surface 60 shown in FIG. 8(a), all of the injection holes 61 are normally open. In other words, the cooling liquid is injected from all of the injection holes 61. In this case, as shown in FIG. 8(e), the pressure distribution of the cooling liquid is generally uniform, although some fluctuations can be observed.

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), an area 75 where the pressure is lower than the surrounding area is observed. It is presumed that the area 75 corresponds to the clogged injection hole 61x.

In the injection surface 60 shown in FIG. 8(c), six injection holes 61x arranged continuously in the axial direction are intentionally clogged. In this case, as shown in FIG. 8(g), an area 76 was observed where the pressure was lower than the surrounding area. The longitudinal direction of the area 76 was the axial direction. It is presumed that the area 76 corresponds to the clogged injection holes 61x.

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 are 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 region 77 was a diagonal direction inclined with respect to both the axial and circumferential directions. Region 77 is presumed to correspond to the clogged injection hole 61x.

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 succession 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 is small, clogging of the injection holes 61 can be easily detected.

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 it may be difficult to achieve the cooling rate if clogging of the injection holes 61 occurs as described above. 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.

Quenching is, for example, high-frequency induction heating, and high-frequency induction heating devices have a heating section that heats the workpiece and a cooling section that sprays a coolant to cool the workpiece. The heating section and the cooling section may be integrated or separate.

The above-mentioned 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-mentioned embodiments in which some components are added, deleted, or changed. The above-mentioned 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 complex 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 complex shape.

In the first embodiment, a pressure sensor sheet is attached to a first surface and a second surface of the 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 pressure sensor sheet is attached between two consecutive surfaces and bent between the two surfaces. However, the pressure sensor sheet may be attached between three consecutive surfaces, such as a U-shaped surface, and bent between the three surfaces.

In the second embodiment, a first pressure sensor sheet is attached to a first surface of the 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, but it may be implemented in a manner in which a pressure sensor sheet is attached to each of three or more surfaces.

10: Pressure sensor sheet 11: First portion 12: Second portion 13: Bending line 21, 22, 30, 40: Pressure sensor sheet 41: Pressure sensor element 41C: Arrangement period of pressure sensor elements in axial direction 41S: Arrangement period of pressure sensor elements in circumferential direction 50: Cooling jacket 60: Ejection surface 61: Ejection hole 61C: Arrangement period of ejection holes in axial direction 61S: Arrangement period of ejection holes in circumferential direction 61x: Clogged ejection hole 62: Row 70: Cooling liquid 70a: Reservoir 75, 76, 77: Area 100: Workpiece 101: Boss portion 101a: Through hole 102: Plate portion 103: Rim portion 103a: Outer circumferential surface 104: Flange 104a: Upper surface 105: Boundary line 106: Part 110: Area to be heat-treated 200: Workpiece 201: curved region 210: region to be heat treated

Claims (6)

A step of attaching a pressure sensor sheet to a first surface and a second surface of a workpiece that are in contact with each other 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;
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: 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 . 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 step 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. 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. 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. The method for evaluating a cooling step of a heat treatment according to any one of claims 1 to 5 , wherein the cooling medium is a cooling liquid.

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