Heat treatment method and heat treatment apparatus

Abstract

To provide a heat treatment method and a heat treatment apparatus that can relatively easily and appropriately handle heat treatment of heating objects of various shapes.SOLUTION: A heat treatment method according to the present invention is a method for performing heat treatment on a heating object 51, where the heating object 51 is disposed inside a hollow member 2 that has heat resistance and insulation properties while allowing magnetic flux to pass through, and the atmosphere around the heating object 51 is adjusted, the heating object 51 is heated by induction heating based on the application of electric current to a heating coil 3 located outside the hollow member 2, and the hollow member 2 manufactured by additive manufacturing is used.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a heat treatment method and a heat treatment apparatus used for heat treatment such as quenching of an object to be heated by induction heating.

Background Art

[0002] As an example of heat treatment, high-frequency quenching of the surface of a steel object to be heated is generally performed in the atmosphere. In this case, even with short-time heating and rapid cooling, an oxide film is formed on the surface of the object to be heated, so it is necessary to remove it by polishing, grinding, etc. in subsequent processes.

[0003] On the other hand, in so-called non-oxidizing quenching, for example, while adjusting the atmosphere around the object to be heated by supplying, for example, nitrogen gas or other atmosphere gases, the object to be heated is quenched by induction heating. Thereby, the formation of an oxide film on the surface of the object to be heated can be suppressed. As a technique related to such non-oxidizing quenching, there is, for example, the one described in Patent Document 1.

[0004] Patent Document 1 proposes, for the purpose of "being able to simultaneously quench the head and the waist of a spool and, moreover, preventing scale from occurring on the quenched surface", "a non-oxidizing high-frequency quenching method characterized in that a work held in a work accommodation container filled with an inert gas or a reducing gas and having an open lower end is heated by a high-frequency heating coil disposed outside the work accommodation container so as to face the surface of the work to be quenched, and then the holding of the work is released, and the work is dropped into a tank filled with a quenching liquid and attached to the lower part of the work accommodation container and immersed in the quenching liquid". Further, in this Patent Document 1, "a non-oxidizing high-frequency quenching apparatus characterized by comprising a work accommodation container filled with an inert gas or a reducing gas and having an open lower end, means for holding a work in this work accommodation container, a high-frequency heating coil disposed outside the work accommodation container so as to face the surface of the work to be quenched, means for releasing the holding of the work, and a tank filled with a quenching liquid and attached to the lower part of the work accommodation container" is also proposed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In heat treatment such as the above-described non-oxidizing quenching, the object to be heated can be arranged inside the hollow member, and in that state, the object to be heated can be heated by induction heating using a heating coil outside the hollow member. At this time, by adjusting the atmosphere around the object to be heated inside the hollow member, formation of an oxide film on the surface of the object to be heated can be suppressed. The hollow member used for such heat treatment is required to be made of a material that allows magnetic flux to pass through and has heat resistance and insulation so that induction heating of the object to be heated inside can be performed.

[0007] Here, the objects to be heated include various ones with different shapes of themselves and dimensions or shapes of the heated portions such as the surfaces on which the heat treatment is performed. The hollow members in which the objects to be heated are arranged inside need to have various dimensions and shapes corresponding to the shapes of such respective objects to be heated.

[0008] However, it is difficult to cover all hollow members with various dimensions and shapes with off-the-shelf members such as cylindrical members that are available on the market by purchase. Also, depending on the material of the hollow member, processing may be difficult in some cases. When performing the above-described heat treatment, it is desired that such hollow members with various dimensions and shapes can be easily obtained.

[0009] This invention addresses the above-described problems, and its object is to provide a heat treatment method and a heat treatment apparatus that can relatively easily and appropriately respond to heat treatment of objects to be heated with various dimensions or shapes.

Means for Solving the Problems

[0010] The heat treatment method of the present invention is a method for performing heat treatment on an object to be heated. While passing magnetic flux and arranging the object to be heated inside a hollow member having heat resistance and insulation, the object to be heated is heated by induction heating based on energization of a heating coil located outside the hollow member while adjusting the atmosphere around the object to be heated. As the hollow member, a hollow member manufactured by three-dimensional modeling is used.

[0011] In the above heat treatment method, the hollow member may be a laminated molded product.

[0012] In the above heat treatment method, the adjustment of the atmosphere around the object to be heated may be performed by supplying an atmosphere gas to the inside of the hollow member.

[0013] In this case, the atmosphere gas can be a non-oxidizing gas.

[0014] In the above heat treatment method, the hollow member has a cylindrical portion, the object to be heated has a rod-shaped portion, and the heating coil may have a portion that spirally extends around the cylindrical portion outside the cylindrical portion of the hollow member.

[0015] In the above heat treatment method, the hollow member can be made of glass or resin.

[0016] In the above heat treatment method, the object to be heated may be cooled after being heated.

[0017] The above heat treatment method may be used for quenching the object to be heated.

[0018] The heat treatment apparatus of the present invention is a heat treatment apparatus used for performing heat treatment on an object to be heated, and includes a hollow member that allows magnetic flux to pass through, has heat resistance and insulation properties, and has the object to be heated disposed inside thereof, and a heating coil that is located outside the hollow member and through which an electric current flows to cause induction heating of the object to be heated, and the hollow member is a laminated object.

[0019] The above heat treatment apparatus may have a gas supply unit that supplies an atmospheric gas inside the hollow member.

[0020] The gas supply unit can be configured to supply a non-oxidizing gas as the atmospheric gas.

[0021] In the above heat treatment apparatus, the hollow member may have a cylindrical portion, the object to be heated may have a rod-shaped portion, and the heating coil may have a portion that spirally extends around the cylindrical portion outside the cylindrical portion of the hollow member. [[ID=I4]]

[0022] The hollow member of the above heat treatment apparatus can be made of glass or resin.

[0023] The above heat treatment apparatus may have a cooling unit that cools the object to be heated heated by the heating coil.

[0024] The above heat treatment apparatus may be used for quenching the object to be heated.

Advantages of the Invention

[0025] According to the heat treatment method or heat treatment apparatus of the present invention, it is possible to relatively easily and appropriately cope with heat treatment of objects to be heated having various dimensions or shapes.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The heat treatment method according to one embodiment of the present invention is a method of performing heat treatment on an object to be heated. In this heat treatment method, for example, in a heat treatment apparatus 1 as shown in FIG. 1, while passing magnetic flux and placing the object to be heated 51 inside a hollow member 2 having heat resistance and insulation properties, an electric current is passed through a heating coil 3, and the object to be heated 51 is heated by induction heating based thereon. The object to be heated 51 is heat-treated by induction heating with the heating coil 3 while the atmosphere around it is adjusted inside the hollow member 2.

[0028] And here, as the hollow member 2, one produced by three-dimensional modeling is used. Since the hollow member 2 is produced by three-dimensional modeling, it is possible to prepare various shapes and dimensions according to objects to be heated having various dimensions and shapes. Therefore, according to the heat treatment method and the heat treatment apparatus 1 of this embodiment, it is possible to relatively easily and appropriately cope with heat treatment such as non-oxidizing quenching of objects to be heated having various shapes.

[0029] (Object to be heated) The object to be heated 51 is not limited as long as it can be heat-treated by induction heating. Typically, this embodiment can be used when performing quenching, which involves heating and then cooling, as heat treatment on the whole or a part (such as a heated part on the surface) of a metal object to be heated 51 made of steel or the like.

[0030] The object to be heated 51 has various dimensions and shapes as described above. In this embodiment, heat treatment such as non-oxidizing quenching can be performed on such objects to be heated 51 having various dimensions and shapes while suppressing the formation of an oxide film on the surface.

[0031] The object to be heated 51 shown in FIGS. 1 and 2 is, as an example, a hollow rack bar used together with a pinion gear (not shown) in a vehicle steering system. More specifically, the illustrated object to be heated 51 has a plurality of tooth portions 53 that mesh with the above-mentioned pinion gear formed in a part of the circumferential direction in a portion near one end portion 52a in the axial direction (the left-right direction in FIGS. 1 and 2) of a tubular main body portion 52 such as a circular tube, and are formed at positions recessed inward on the inner peripheral side along the axial direction. This object to be heated 51 has a hollow rod-shaped portion as the tubular main body portion 52. Although not shown, it is also possible to use an object to be heated having a solid rod-shaped portion. Note that a thin-walled portion 54 that is slightly thinner than other portions is provided in a part of the circumferential direction at a location adjacent to the other end portion 52b side of the plurality of tooth portions 53 in the axial direction of the object to be heated 51.

[0032] Here, taking as an example the case where heat treatment is performed on the vicinity of the surface of the tooth portion 53 in the object to be heated 51 as the hollow rack bar shown in FIGS. 1 and 2 as the portion to be heated, this will be described in detail. However, the object to be heated 51 can also be various other parts, members, or other products, and is not limited to the illustrated example.

[0033] (Heat treatment apparatus) The heat treatment apparatus 1 is used to perform heat treatment on the object to be heated 51 as described above, and has at least a hollow member 2 in which the object to be heated 51 is disposed inside, and a heating coil 3 located outside the hollow member 2.

[0034] Here, the hollow member 2 is manufactured by three-dimensional modeling and is typically a laminated object. Three-dimensional modeling is a method of supplying materials based on three-dimensional data related to a three-dimensional shape to form a three-dimensional object. Among them, laminated modeling means inputting three-dimensional data of a target product to be modeled into a computer, horizontally slicing the three-dimensional data on the computer to create two-dimensional data, and laminating and modeling materials based on these data. As a result of the material being laminated and shaped in layers, laminated traces remain in the laminated object. Therefore, by using visual inspection, a scanning electron microscope, etc. to check for the presence or absence of such laminated traces, it is possible to determine whether the hollow member 2 is a laminated object.

[0035] There are various methods for this laminated modeling, but the method used to manufacture the hollow member 2 according to this embodiment is not particularly limited.

[0036] The dimensions and shape of the hollow member 2 can be appropriately changed according to the dimensions and shape of the object 51 to be heated disposed inside it. In the illustrated embodiment, as an example, the hollow member 2 is cylindrical with an inner diameter larger than the outer diameter of the object 51 to be heated so that the object 51 to be heated can be disposed inside it with its axial direction substantially coinciding with that of the object 51 to be heated. Therefore, it can be said that this hollow member 2 has a cylindrical portion. Although not shown, the hollow member can also be provided with a joint used for connection to a gas supply portion as described later.

[0037] As shown in FIG. 1, the hollow member 2 only needs to be able to dispose the object 51 to be heated inside it such that at least the heated portion of the object 51 to be heated (in this example, the portion near the surface of a plurality of tooth portions 53) enters. Therefore, even if other portions (portions on the other end portion 52b side) of the object 51 to be heated are located outside the hollow member 2, it does not matter. This is because the unheated portion of the object 51 to be heated does not need to adjust the surrounding atmosphere with the hollow member 2.

[0038] The hollow member 2 is made of a material that allows magnetic flux to pass through and has heat resistance and insulation properties in order to enable induction heating of the inner object 51 to be heated. For example, it can be made of glass (heat-resistant glass) or resin (heat-resistant resin). Specifically, borosilicate glass is suitable as the glass, and polyamide resin is suitable as the resin. As an example of borosilicate glass, there is one with an SiO2 content of 80.7% by mass, a B2O3 content of 12.9% by mass, a Na2O content of 3.8% by mass, an Al2O3 content of 2.2% by mass, and a K2O content of 0.4% by mass, but it is not limited to this. In some cases, it may be preferable to use a heat-resistant resin hollow member that is less likely to crack than a heat-resistant glass hollow member. As an example of polyamide resin, there is one composed of a diamine component containing 40 mol% or more of bis(aminomethyl)cyclohexane and a dicarboxylic acid component containing 50 mol% or more of isophthalic acid, but it is not limited to this.

[0039] The laminated fabrication of the hollow member 2 made of the material as described above can be performed, for example, by inputting the three-dimensional data of the target product to be fabricated into a computer, horizontally slicing the three-dimensional data on the computer to create two-dimensional data, melting the material based on these data and discharging it in layers and then solidifying it, or repeatedly arranging powder in layers and sintering it by laser irradiation or the like, and stacking (laminating) the layers thus formed. Thereby, the hollow member 2 of the laminated object is obtained. Although there are various methods of laminated fabrication, the method used to manufacture the hollow member 2 according to the present embodiment is not particularly limited.

[0040] Also, here, the heating coil 3 located outside the hollow member 2 may be any one that is located outside the hollow member 2 and can heat the heated portion of the object 51 to be heated disposed inside the hollow member 2 by induction heating or high-frequency heating. In the illustrated typical example, the heating coil 3 is provided in contact with the outer surface of the hollow member 2 and extending spirally around the cylindrical portion. However, the heating coil 3 may be provided with a tape or the like (not shown) interposed between it and the hollow member 2 without directly contacting the hollow member 2.

[0041] The heating coil 3 can be connected to a power source 4 that the heat treatment apparatus 1 can include, for example, at each end of the portion that extends in a spiral shape thereof. By passing an electric current from the power source 4 through the heating coil 3, the heating coil 3 is energized, and based on the induced heating thereby, an object 51 to be heated disposed further inside the hollow member 2 inside the heating coil 3 can be heated.

[0042] The heat treatment apparatus 1 may further include a gas supply unit 5. The gas supply unit 5 is, for example, disposed in the vicinity of the hollow member 2 and can supply an atmospheric gas inside the hollow member 2. Thereby, since the atmosphere containing oxygen present inside the hollow member 2 can be replaced with the atmospheric gas, the atmosphere around the object 51 to be heated inside the hollow member 2 during heating can be adjusted more easily and surely.

[0043] The atmospheric gas supplied from the gas supply unit 5 to the inside of the hollow member 2 is preferably a non-oxidizing gas. Specific examples of the non-oxidizing gas include inert gases such as helium gas and argon gas, and nitrogen gas. In this case, the gas supply unit 5 can be configured to be capable of supplying a non-oxidizing gas, for example, by being connected to a tank or other gas supply source in which the non-oxidizing gas is stored.

[0044] However, even if the atmospheric gas is not supplied to the inside of the hollow member, since the object 51 to be heated is disposed inside the hollow member 2, the oxygen concentration decreases or oxygen almost disappears inside the hollow member 2 by heating at a relatively high temperature, and thus it may be possible to suppress the formation of an oxide film on the surface of the object 51 to be heated. For this reason, it is not always necessary to supply the atmospheric gas to the inside of the hollow member 2 or for the heat treatment apparatus 1 to include the gas supply unit 5, and they are optional configurations. Note that it is preferable to use the atmospheric gas as a non-oxidizing gas because it is possible to more surely approach non-oxidizing quenching.

[0045] In the illustrated heat treatment apparatus 1, the gas supply unit 5 is disposed near the opening of the hollow member 2 located on the other end portion 52b side of the object to be heated 51. In this case, as indicated by the arrow in FIG. 1, the atmosphere gas can be supplied from the gas supply unit 5 through the opening of the hollow member 2 to the inside thereof. Alternatively, although not shown, when a joint communicating with the inside is provided in the hollow member, the gas supply unit may be connected to the joint, and the atmosphere gas may be supplied from the joint to the inside.

[0046] Also, for example, when quenching the object to be heated 51 as the heat treatment, a cooling unit 6 for cooling the object to be heated 51 after heating with the heating coil 3 can be provided in the heat treatment apparatus 1. The cooling unit 6 is provided at a position adjacent to the heating coil 3 or the like, and may be configured to wipe a gas such as air or an aqueous solution in which a polymer is dissolved or a liquid such as water toward the object to be heated 51 from the vicinity around the object to be heated 51 in a cylindrical or other shape, as indicated by the arrow in FIG. 2. Thereby, at least the heated portion of the object to be heated 51 heated by induction heating with the heating coil 3 can be cooled.

[0047] In addition, if necessary, the heat treatment apparatus 1 may be provided with a chuck or other holding unit 7 for holding an arbitrary portion such as the other end portion 52b of the object to be heated 51 by sandwiching or the like. In this case, while holding the object to be heated 51 with the holding unit 7, it can be moved inside the hollow member 2, or after heating with the heating coil 3, it can be moved from the inside of the hollow member 2 to the inside of the cooling unit 6 as indicated by the white arrow in FIG. 2.

[0048] (Heat Treatment Method) The heat treatment method according to the embodiment of the present invention can be implemented using the heat treatment apparatus 1 as described above. This heat treatment method includes a heating step, and may further include a cooling step if necessary.

[0049] The heating process can be performed, for example, while holding the other end portion 52b of the object to be heated 51 by the holding portion 7, after moving the object to be heated 51 inside the hollow member 2 as shown in FIG. 1. In the heating process, a high-frequency current is passed from the power source 4 through the heating coil 3, and at least the portion to be heated of the object to be heated 51 is heated by induction heating based on the energization.

[0050] At this time, since the object to be heated 51 is disposed inside the hollow member 2, the object to be heated 51 is heated while the atmosphere around the object to be heated 51 is adjusted inside. As a result, formation of an oxide film on the surface of the object to be heated 51 can be suppressed.

[0051] In order to more reliably suppress the formation of the oxide film, when heating the object to be heated 51, an atmosphere gas can be supplied from the opening on the other end portion 52b side of the hollow member 2 to the inside thereof using the gas supply portion 5. The atmosphere gas is preferably a non-oxidizing gas, and may be nitrogen gas as an example. According to three-dimensional shaping or laminated shaping, hollow members 2 having various dimensions and shapes can be produced, and thus the hollow member 2 can have dimensions and a shape such that the atmosphere gas supplied to the inside is less likely to leak to the outside. For example, it is also conceivable to use a hollow member 2 in which the opening is blocked to some extent.

[0052] When performing the cooling process after the heating process is completed, for example, the holding portion 7 can be moved together with the object to be heated 51, and the object to be heated 51 can be disposed inside the cooling portion 6. In the cooling process, at least the portion to be heated of the object to be heated 51 is wiped with a gas such as air or an aqueous solution in which a polymer is dissolved or a liquid such as water to cool the portion. In this way, quenching of the portion to be heated of the object to be heated 51 can be performed.

[0053] As described above, the hollow member 2 used in the heating process is made by three-dimensional modeling, and typically may be a laminated object made by laminated modeling among three-dimensional modeling. Therefore, the hollow member 2 having dimensions and a shape suitable for heating objects 51 of various dimensions and shapes can be easily prepared. Even if a hollow member 2 having dimensions and a shape suitable for a heating object 51 of a predetermined dimension and shape cannot be obtained on the market, it can be made by three-dimensional modeling and used for heat treatment. Therefore, according to this embodiment, it is possible to easily and appropriately respond to heat treatment of heating objects of various dimensions or shapes. In this case, processing such as cutting for forming the hollow member 2 becomes unnecessary, and outsourcing of special-order products and the like become unnecessary, and the manufacturing cost may be reduced.

Explanation of reference numerals

[0054] 1 Heat treatment apparatus 2 Hollow member 3 Heating coil 4 Power supply 5 Gas supply section 6 Cooling section 7 Holding section 51 Heating object 52 Tubular main body section 52a One end portion 52b The other end portion 53 Tooth portion 54 Thin-walled portion

Claims

1. A method for heat-treating an object to be heated, comprising: while passing a magnetic flux and placing the object to be heated inside a hollow member having heat resistance and insulation properties, adjusting the atmosphere around the object to be heated, and heating the object to be heated by induction heating based on energization of a heating coil located outside the hollow member; A heat treatment method using, as the hollow member, a hollow member produced by three-dimensional modeling.

2. The heat treatment method according to claim 1, wherein the hollow member is a laminated structure.

3. The heat treatment method according to claim 1 or 2, wherein the adjustment of the atmosphere around the object to be heated is performed by supplying an atmosphere gas into the hollow member.

4. The heat treatment method according to claim 3, wherein the atmosphere gas is a non-oxidizing gas.

5. The hollow member has a cylindrical portion, and the object to be heated has a rod-shaped portion, The heat treatment method according to claim 1 or 2, wherein the heating coil has a portion that spirally extends around the outside of the cylindrical portion of the hollow member.

6. The heat treatment method according to claim 1 or 2, wherein the hollow member is made of glass or resin.

7. The heat treatment method according to claim 1 or 2, further comprising cooling the object to be heated after heating.

8. The heat treatment method according to claim 1 or 2, which is used for quenching the object to be heated.

9. A heat treatment apparatus used for heat-treating an object to be heated, comprising: a hollow member that allows a magnetic flux to pass through and has heat resistance and insulation properties, with the object to be heated disposed inside; and a heating coil located outside the hollow member, through which an electric current flows to cause induction heating of the object to be heated and having The heat treatment apparatus, wherein the hollow member is a laminated structure.

10. The heat treatment apparatus according to claim 9, further comprising a gas supply unit for supplying an atmosphere gas into the hollow member.

11. The heat treatment apparatus according to claim 10, wherein the gas supply unit is configured to be capable of supplying a non-oxidizing gas as the atmosphere gas.

12. The hollow member has a cylindrical portion, and the object to be heated has a rod-shaped portion, The heat treatment apparatus according to any one of claims 9 to 11, wherein the heating coil has a portion that spirally extends around the outside of the cylindrical portion of the hollow member.

13. The heat treatment apparatus according to any one of claims 9 to 11, wherein the hollow member is made of glass or resin.

14. The heat treatment apparatus according to any one of claims 9 to 11, having a cooling unit that cools the object to be heated heated by the heating coil.

15. The heat treatment apparatus according to any one of claims 9 to 11, which is used for quenching the object to be heated.

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