Heat treatment apparatus

Abstract

To provide a heat treatment apparatus which has a structure that is unlikely to become complicated and can solve problems such as energy loss.SOLUTION: A heat treatment apparatus 10 comprises a treatment tank 11 which can at least execute cooling treatment to an object. The treatment tank 11 comprises: an inner wall 15 which surrounds an opening part 12; a heat insulation material 16 which is arranged at the outside of the inner wall 15; and an end face material 20 which forms an end face 20a around the opening part 12. A material of the end face material 20 has a thermal conductivity lower than that of the inner wall 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In the field of metal heat treatment, sub-zero treatment is carried out to rapidly cool quenched steel to below 0°C in order to prevent deformation over time and improve the wear resistance and hardness of steel (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-60524 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-169220 Summary of the Invention [Problem to be solved by the invention]

[0004] The typical cooling temperature for sub-zero treatment is around -80°C, but there is an increasing trend for ultra-sub-zero treatment with cooling performance below -100°C, with some requests for temperatures between -196°C and -120°C. There is also a demand for low-temperature tempering, which involves heating to around +200°C, in conjunction with sub-zero treatment.

[0005] If sub-zero treatment and low-temperature tempering are performed in separate equipment, it will require the cost and space of two pieces of equipment, and it will also require the effort of transferring the treated products.For this reason, it is desirable to have a single heat treatment device that can handle temperatures from ultra-sub-zero treatment to low-temperature tempering (-196°C to +200°C).

[0006] To ensure the thermal insulation of the treatment tank, the walls of the treatment tank are sometimes filled with insulating material. Furthermore, to ensure the airtightness of the space in the treatment tank where the object is placed, packing is sometimes placed between the treatment tank and the lid. In this case, the internal structure of the wall or the structure between the treatment tank and the lid becomes complex, and if the temperature range that changes during heat treatment becomes wide, the impact of distortion of the structural materials due to thermal contraction and expansion becomes significant. Furthermore, if frost forms on the exterior surface of the treatment tank at low temperatures or if the exterior surface of the treatment tank overheats at high temperatures, issues such as energy loss arise.

[0007] The present invention has been proposed in view of the above-mentioned conventional circumstances, and aims to provide a heat treatment apparatus that is less likely to be complicated in structure and that can solve problems such as energy loss. [Means for solving the problem]

[0008] In order to achieve the above object, the present invention provides the following means. [1] A heat treatment device having a treatment tank capable of at least cooling an object, wherein the treatment tank has an inner wall surrounding an opening, a heat insulating material arranged on the outside of the inner wall, and an edge material that forms the edge surface around the opening, and the material of the edge material has a lower thermal conductivity than the material of the inner wall. [2] The heat treatment device according to [1], characterized in that the material of the end surface material has a larger specific heat capacity than the material of the inner wall. [3] The heat treatment device described in [1] or [2], characterized in that the treatment tank has an outer wall that covers the outside of the insulation material and a reinforcing material that connects the inner wall and the outer wall, and the material of the reinforcing material has a lower thermal conductivity than the material of the inner wall. [4] The heat treatment device according to [3], wherein the material of the reinforcing material has a specific heat capacity greater than that of the material of the inner wall. [5] The heat treatment device described in any one of [1] to [4] is characterized in that the heat treatment device comprises a lid facing the treatment tank and closing the opening, and a gasket arranged between the lid and the end surface material, and the position at which the gasket contacts the end surface material is a position at which the gasket faces the insulating material or a position at which the gasket faces outward from the insulating material. [6] The heat treatment device according to any one of [1] to [5], wherein the temperature inside the treatment tank is controlled within a range of -196°C to +200°C. [7] The heat treatment device described in any one of [1] to [6], characterized in that the heat treatment device comprises a lid facing the treatment tank and closing the opening, and a gasket placed between the lid and the end surface material, the end surface of the end surface material facing the lid being flat, and the opposing surface of the lid facing the end surface material being flat. [Effects of the Invention]

[0009] According to the heat treatment apparatus of the present invention, the structure is not complicated and problems such as energy loss can be solved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a vertical cross-sectional view showing an example of a heat treatment apparatus according to an embodiment of the present invention. [Figure 2] 1 is a perspective view showing a main part of a heat treatment apparatus according to an embodiment of the present invention; [Figure 3] FIG. 10 is a perspective view showing a main part of a comparative heat treatment apparatus. [Figure 4] 1 is a cross-sectional view showing an example of a heat treatment apparatus according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, characteristic parts may be shown schematically for the sake of convenience in order to make the features easier to understand. The number of components and dimensional ratios may not necessarily be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited to them. Appropriate changes may be made within the scope of the present invention.

[0012] Fig. 1 is a longitudinal sectional view showing an example of a heat treatment apparatus 10 of the present embodiment. Fig. 2 is a perspective view showing a main part of the heat treatment apparatus of the present embodiment. Fig. 3 is a perspective view showing a main part of a comparative heat treatment apparatus. Fig. 4 is a transverse sectional view showing an example of the heat treatment apparatus 10 of the present embodiment.

[0013] 1, a heat treatment apparatus 10 according to this embodiment includes a treatment tank 11 capable of at least cooling an object (not shown). The object is an object to be heat-treated. The treatment tank 11 has an opening 12 for placing the object in the treatment tank 11 and an internal space 13 for accommodating the object in the treatment tank 11.

[0014] The treatment tank 11 allows an object to be put into and taken out of the internal space 13 through the opening 12. The treatment tank 11 also allows an object to be heat-treated while it is housed in the internal space 13. The heat treatment preferably includes at least a cooling treatment, and may also include a heating treatment.

[0015] The treatment tank 11 has a wall 14 surrounding the internal space 13. The wall 14 in the illustrated example includes a side wall portion 14a disposed closer to the opening 12 and an opposing wall portion 14b disposed behind the opening 12. When the opening 12 faces upward in the treatment tank 11, the opposing wall portion 14b may be a bottom wall portion. When the opening 12 faces forward in the treatment tank 11, the opposing wall portion 14b may be a rear wall portion.

[0016] The shape of the treatment tank 11 is not particularly limited, but examples thereof include a rectangular pillar shape, a cylindrical shape, etc. The shape of the opening 12 is not particularly limited, but may be a polygonal shape such as a rectangle, or a curved shape such as a circle.

[0017] The wall 14 of the treatment tank 11 has an inner wall 15 surrounding the opening 12 and a heat insulating material 16 arranged on the outside of the inner wall 15. Furthermore, the wall 14 in the illustrated example has an outer wall 17 on the outside of the heat insulating material 16. In this case, the heat insulating material 16 is filled between the inner wall 15 and the outer wall 17. Specific examples of the heat insulating material 16 include, but are not limited to, glass wool, rock wool, etc. Other materials may be used as long as they have excellent heat resistance and cold resistance according to the intended use of the treatment tank 11.

[0018] The illustrated inner wall 15 includes an inner wall frame 15f and an inner wall plate 15p, as shown in Fig. 2. The illustrated outer wall 17 includes an outer wall frame 17f and an outer wall plate 17p, as shown in Fig. 2. In this case, the inner wall frame 15f and the outer wall frame 17f serve as frameworks for maintaining the shape of the treatment tank 11 surrounding the internal space 13. The inner wall plate 15p and the outer wall plate 17p are plates that allow the treatment tank 11 to have an airtight structure for the internal space 13.

[0019] The structure of the wall 14 is not limited to the illustrated example, and various structures can be adopted. Examples of materials for the inner wall 15 and the outer wall 17 include iron and iron alloys such as stainless steel (SUS304) and carbon steel. Other materials may be used as the structural material for the wall 14 as long as they can withstand the heat treatment temperature. Furthermore, if a reactive agent such as a gas is used during the heat treatment, a material that does not react with the agent is preferred.

[0020] From the viewpoint of durability against low-temperature brittleness, it is preferable to use stainless steel such as SUS304 for at least the inner wall plate 15p. Since the heat treatment device 10 is generally installed in a factory or the like, it is preferable to use stainless steel such as SUS304 for the outer wall plate 17p as well from the viewpoint of durability against the installation environment.

[0021] The materials for the inner wall frame 15f and the outer wall frame 17f can be selected appropriately depending on factors such as the strength of the framework, ease of cutting and welding, and cost. Iron and iron alloys other than stainless steel may also be used for the framework. Sealing the framework on both the inside and outside with the inner wall plate 15p and outer wall plate 17p prevents outside air from entering the interior of the wall 14, suppressing moisture accumulation and condensation and freezing during cooling.

[0022] 1, the heat treatment apparatus 10 of this embodiment includes an end surface material 20 that forms an end surface 20a around the opening 12. The material of the end surface material 20 has a lower thermal conductivity than the material of the inner wall 15.

[0023] 2, the inner wall 15 and the outer wall 17 are spaced apart at the position of the edge member 20. For example, when the inner wall 15, such as the inner wall frame 15f and the inner wall plate 15p, is made of metal, resin can be used as the material for the edge member 20. If the thermal conductivity depends on temperature, the thermal conductivity at around room temperature, for example, 20 to 25°C, may be compared.

[0024] 3, the material of the end surface material 18 constituting the end surface of the wall 14 is a material having the same thermal conductivity as the inner wall 15. For example, when the inner wall frame 15f and the inner wall plate 15p are made of metal, the material of the end surface material 18 of the comparative example can be metal. 2 and 3, the heat insulating material 16 filled between the inner wall 15 and the outer wall 17 is not shown.

[0025] When a cooling process is performed in the processing tank 11, the inner wall 15 is also cooled. Furthermore, when a heating process is performed in the processing tank 11, the inner wall 15 is also heated. In contrast, the edge surface material 18 has high thermal conductivity, so heat is likely to transfer from the inner wall 15 to the outside through the edge surface material 18. During the cooling process, cold is likely to be transferred from the inside to the outside (heat is likely to be transferred from the outside to the inside), and the temperature of the edge surface material 18 is likely to drop. Furthermore, during the heating process, heat is likely to be transferred from the inside to the outside, and the temperature of the edge surface material 18 is likely to rise.

[0026] According to the heat treatment apparatus 10 of this embodiment, the inner wall 15 and the outer wall 17 are thermally separated by the end face material 20 and the insulating material 16, which have low thermal conductivity. This suppresses heat conduction between the inner wall 15 and the outer wall 17. Even when the interior of the treatment vessel 11 is undergoing a cooling process, the effects of a temperature drop on the outer wall 17, such as frosting, can be suppressed. Furthermore, even when the interior of the treatment vessel 11 is undergoing a heating process, the effects of a temperature rise on the outer wall 17, such as overheating, can be suppressed. Similarly, even when the wall 14 of the treatment vessel 11 has an external structure outside the insulating material 16 that is different from the external wall 17 in the illustrated example, heat conduction between the inner wall 15 and the external structure of the treatment vessel 11 can be suppressed, thereby suppressing frosting, overheating, and the like.

[0027] It is preferable that the material of the end surface material 20 has a larger specific heat than the material of the inner wall 15. If the specific heat of the end surface material 20 is larger than that of the inner wall 15, the temperature change of the end surface material 20 can be suppressed even if a temperature change occurs in the inner wall 15 due to the influence of heat treatment. If the specific heat depends on temperature, the specific heat may be compared at around room temperature, for example, 20 to 25°C.

[0028] Specific examples of the end surface material 20 include thermosetting resins such as Bakelite (phenolic resin). The resin may be impregnated into a fiber substrate such as paper, cloth, or glass. Other materials may be used as long as they have excellent heat resistance and cold resistance according to the intended use of the treatment tank 11, and fillers may be blended into the resin.

[0029] The edge material 20 described above can maintain a small temperature difference between the edge material 20 and the outer wall 17 for a longer period of time. This can also suppress heat conduction between the outer wall 17 and the edge material 20. For example, even if the outer wall 17 is made of a material with high thermal conductivity and low specific heat, such as metal, it is possible to effectively suppress heat conduction between the inner wall 15 and the outer wall 17. The same applies when the wall 14 of the treatment tank 11 has an external structure outside the heat insulating material 16 that is different from the outer wall 17 in the illustrated example.

[0030] 1, the heat treatment apparatus 10 of this embodiment includes a reinforcing member 21 that connects the inner wall 15 and the outer wall 17. The material of the reinforcing member 21 is preferably a material with lower thermal conductivity than the material of the inner wall 15. For example, when the inner wall 15 is made of metal, the material of the reinforcing member 21 may be resin. When the thermal conductivity depends on temperature, the thermal conductivity may be compared at around room temperature, for example, at 20 to 25°C.

[0031] Like the edge surface member 20 described above, the reinforcing member 21 is also a member that connects the inner wall 15 and the outer wall 17. Because the reinforcing member 21 is made of a material with a lower thermal conductivity than the material of the inner wall 15, the inner wall 15 and the outer wall 17 are thermally separated by the edge surface member 20, reinforcing member 21, and insulating material 16, which have low thermal conductivity. Therefore, heat conduction between the inner wall 15 and the outer wall 17 can be suppressed.

[0032] Furthermore, it is preferable that the material of the reinforcing material 21 has a higher specific heat than the material of the inner wall 15. When the specific heat of the reinforcing material 21 is higher than that of the inner wall 15, the temperature change of the reinforcing material 21 can be suppressed even if a temperature change occurs in the inner wall 15 due to the influence of heat treatment. If the specific heat depends on temperature, the specific heat may be compared at around room temperature, for example, 20 to 25°C.

[0033] Specific examples of the reinforcing material 21 include thermosetting resins such as Bakelite (phenolic resin). The resin may be impregnated into a fiber substrate such as paper, cloth, or glass. Other materials may be used as long as they have excellent heat resistance and cold resistance according to the application of the treatment tank 11, and fillers may be blended into the resin. The material of the reinforcing material 21 may be the same as or different from the material of the end surface material 20.

[0034] According to the above-described reinforcing material 21, it is possible to maintain for a longer period a state in which the temperature difference between the reinforcing material 21 and the outer wall 17 is small. This also makes it possible to suppress heat conduction between the outer wall 17 and the reinforcing material 21. For example, even if the outer wall 17 is made of a material with high thermal conductivity and low specific heat, such as a metal, it is possible to effectively suppress heat conduction between the inner wall 15 and the outer wall 17.

[0035] The edge surface material 20 in the treatment tank 11 is preferably arranged around the entire periphery of the opening 12 so that the entire edge surface 20a of the wall 14 surrounding the opening 12 is made up of the edge surface material 20. In the illustrated example, the edge surface material 20 is arranged on the edge surface farthest from the opposing wall portion 14b, and the opening area of ​​the opening 12 is approximately equal to the cross-sectional area of ​​the internal space 13. Although not particularly shown, if a wall portion extends from the end surface of the side wall portion 14a parallel to the opposing wall portion 14b on the same plane as the opening 12, the edge surface material 20 can also be arranged on that extended wall portion. In this case, the opening area of ​​the opening 12 can be set smaller than the cross-sectional area of ​​the internal space 13.

[0036] The placement of the reinforcing material 21 in the treatment tank 11 can be appropriately set in part of the gap filled with the insulating material 16. For example, between the opening 12 and the opposing wall 14b of the treatment tank 11, the reinforcing material 21 may be placed in two locations, near the opening 12 and near the opposing wall 14b, as shown in Fig. 1. In the side wall 14a surrounding the internal space 13 of the treatment tank 11, the reinforcing material 21 may be placed in one or more locations on each surface of the wall 14, as shown in Fig. 4.

[0037] 1, the heat treatment apparatus 10 of this embodiment may include a lid 22 that faces the treatment tank 11 and closes the opening 12. The outer periphery of the lid 22 is disposed facing the end face 20a of the end face material 20. The heat treatment apparatus 10 preferably includes a packing 23 disposed between the lid 22 and the end face material 20.

[0038] When a temperature change occurs in the inner wall 15 during heat treatment, a certain degree of temperature change also occurs in the edge material 20 in contact with the inner wall 15. Furthermore, if the components constituting the wall 14, such as the inner wall 15, experience thermal contraction or thermal expansion, the effects of distortion may reduce the airtightness of the heat treatment device 10. By disposing a packing 23 between the edge material 20 and the lid 22, the effects of distortion can be absorbed and mitigated.

[0039] The material of the packing 23 is not particularly limited, but examples thereof include soft synthetic resin, rubber such as silicone, elastomer, etc. The cross-sectional shape of the packing 23 is not particularly limited, but hollow packing such as P-type, D-type, or Tomoe-type (a-type) is preferred.

[0040] To airtightly close the opening 12 using the lid 22, it is necessary to evenly fit the packing 23 to the end face 20a around the opening 12. By using the end face material 20 described above, it is possible to suppress temperature changes in the outer wall 17 even if temperature changes occur in the inner wall 15 during heat treatment. This reduces the effects of distortion of the structural material due to thermal contraction and expansion accompanying temperature changes, and it is possible to suppress a decrease in the airtightness of the heat treatment device 10 at the lid 22.

[0041] Although the packing 23 can be fixed to the end face 20a side of the treatment tank 11, it is preferable to fix the packing 23 to the lid 22. Examples of fixing members for fixing the packing 23 to the lid 22 or the treatment tank 11 include bolts.

[0042] The position where the packing 23 contacts the end surface material 20 is preferably a position where the packing 23 faces the insulating material 16 or a position where the packing 23 faces outward from the insulating material 16. Compared to when the packing 23 faces the inner wall 15, the dimensions of the end surface material 20 disposed between the packing 23 and the inner wall 15 can be made larger. This makes it possible to suppress temperature changes in the packing 23 even if temperature changes occur in the inner wall 15 during heat treatment.

[0043] It is preferable that the end surface 20a of the end surface material 20 that faces the lid 22 is flat. It is also preferable that the opposing surface 22a of the lid 22 that faces the end surface material 20 is flat. When the end surface 20a and the opposing surface 22a are flat, the packing 23 can more easily absorb and mitigate the effects of distortion than when the end surface 20a and the opposing surface 22a have grooves or other irregularities, and the effects of distortion due to temperature changes and deterioration of airtightness can be suppressed. In particular, when the cooling temperature reaches a low temperature such as -50°C or below, even if the packing 23 hardens at low temperatures and its flexibility decreases, airtightness can be more easily maintained between flat surfaces.

[0044] The internal temperature of the treatment tank 11 can be controlled within a desired range depending on the heat treatment requirements for the object. The cooling temperature performance is not particularly limited, but examples include -200°C or higher, -150°C or higher, -100°C or higher, and -50°C or higher. The heating temperature performance is not particularly limited, but examples include +200°C or lower, +150°C or lower, and +100°C or lower. The internal temperature of the treatment tank 11 may be controlled within a range of -196°C to +200°C. This makes it possible to use the same heat treatment device 10 for processes ranging from ultra-subzero treatment to low-temperature tempering treatment.

[0045] According to the heat treatment device 10 of this embodiment, temperature changes in the external structure of the treatment vessel 11, such as the outer wall 17, can be suppressed, thereby reducing temperature drops during the cooling process and temperature increases during the heating process. The temperature of the external structure of the treatment vessel 11 can be maintained at approximately the same temperature as room temperature without the need to heat the external structure of the treatment vessel 11 during the cooling process or to dissipate heat from the external structure of the treatment vessel 11 during the heating process. Since distortion of the external structure of the treatment vessel 11 due to temperature changes is reduced, the airtightness of the heat treatment device 10 can be ensured without complicating the structure or function of the heat treatment device 10.

[0046] Although not specifically shown, the interior of the lid 22 is preferably filled with insulating material 16, similar to the wall 14 of the treatment tank 11. The wall of the lid 22 may include an inner wall 15 and an outer wall 17. The inner wall 15 of the lid 22 may be composed of an inner wall frame 15f and an inner wall plate 15p. The outer wall 17 of the lid 22 may be composed of an outer wall frame 17f and an outer wall plate 17p.

[0047] Although not particularly shown, it is preferable that the lid 22 be connected to the treatment tank 11 using a hinge or the like. The entire opening 12 may be covered by a single lid 22, or multiple lids 22 may be combined to cover the opening 12. From the viewpoint of flattening the end surface 20a of the treatment tank 11 and the opposing surface 22a of the lid 22, it is preferable that the structure connecting the treatment tank 11 and the lid 22 be arranged on an external structure such as the outer wall 17. Although not particularly shown, the lid 22 may be provided separately from the treatment tank 11 and detachably. It is also possible to close the internal space 13 by combining two treatment tanks 11 so that their openings 12 face each other.

[0048] While the present invention has been described above based on preferred embodiments, the present invention is not limited to the above-described embodiments and various modifications are possible without departing from the spirit of the present invention. Modifications include addition, substitution, omission, and other changes to components in each embodiment. [Example]

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples described below.

[0050] In the wall 14 of the treatment tank 11, the inner wall plate 15p and the outer wall plate 17p were made of SUS304, and the inner wall frame 15f and the outer wall frame 17f were made of iron. Furthermore, the end surface material 20 and the reinforcing material 21 were made of 10 mm thick bakelite (phenolic resin), the heat insulating material 16 was made of 160 mm thick rock wool, and the packing was made of silicone rubber.

[0051] As shown in Figure 1, the reinforcing material 21 is arranged in two locations on two sides consisting of the left and right side wall portions 14a of the four sides that form a rectangle including the opening 12 and the opposing wall portion 14b of the treatment tank 11: near the opening 12 and near the opposing wall portion 14b.

[0052] The position of the reinforcing member 21 near the opening 12 was selected so that the reinforcing member 21 could be fixed to the inner wall plate 15p and the outer wall plate 17p without coming into contact with the end surface member 20, as shown in Fig. 2. The position of the reinforcing member 21 near the opposing wall portion 14b is not specifically shown, but similarly to that shown in Fig. 1, a position was selected so that the reinforcing member 21 could be fixed to the inner wall plate 15p and the outer wall plate 17p within the range of the side wall portion 14a at the location farthest from the opening 12. The arrangement of the reinforcing member 21 in the cross-sectional view shown in Fig. 4 was such that it divided each of the four sides of the quadrangle formed by the side wall portion 14a around the interior space 13 into thirds.

[0053] The method of installing the reinforcing material 21 was such that, when the opening 12 was on the upper side of the treatment tank 11, the inner wall frame 15f and the outer wall frame 17f were positioned so as to satisfy the following conditions (1) to (3), and the reinforcing material 21 was fixed to each of the inner wall frame 15f and the outer wall frame 17f with bolts.

[0054] (1) The height of the upper end surface of the inner wall frame 15f is the same as the height of the upper end surface of the outer wall frame 17f. (2) When viewed from above facing the opening 12, the clearance between the inner wall frame 15f and the outer wall frame 17f is uniform. (3) The reinforcing member 21 intersects perpendicularly with the inner wall frame 15f and the outer wall frame 17f of the tank, and is arranged horizontally.

[0055] <Cooling treatment test> In the heat treatment device 10 of the embodiment, after the internal temperature of the treatment tank 11 was lowered to -150°C and the -150°C state was maintained for one hour, it was confirmed that airtightness could be ensured between the treatment tank 11 and the lid 22, and that the surface temperature of the outer wall 17 of the treatment tank 11 was approximately the same as room temperature, and that frost did not form on the outer wall 17.

[0056] <Heat treatment test> In the heat treatment device 10 of the embodiment, after the internal temperature of the treatment tank 11 was raised to +200°C and maintained at +200°C for one hour, it was confirmed that the surface temperature of the outer wall 17 of the treatment tank 11 was approximately the same as room temperature, and that it was safe to touch with bare hands, and that the outer wall 17 was not overheated. [Explanation of symbols]

[0057] 10...heat treatment device, 11...treatment tank, 12...opening, 13...internal space, 14...wall, 14a...side wall portion, 14b...opposing wall portion, 15...inner wall, 15f...inner wall frame, 15p...inner wall plate, 16...insulating material, 17...outer wall, 17f...outer wall frame, 17p...outer wall plate, 18...comparative end surface material, 19...comparative reinforcing material, 20...end surface material, 20a...end surface, 21...reinforcing material, 22...lid, 22a...opposing surface, 23...gasket

Claims

1. A heat treatment device having a treatment tank capable of at least cooling an object, the treatment tank includes an inner wall surrounding an opening, a heat insulating material disposed on the outer side of the inner wall, and an end surface material constituting an end surface around the opening, The heat treatment apparatus is characterized in that the material of the end surface material has a lower thermal conductivity than the material of the inner wall.

2. The heat treatment apparatus according to claim 1 , wherein the material of the end surface member has a specific heat greater than that of the material of the inner wall.

3. The treatment tank includes an outer wall that covers the outside of the heat insulating material, and a reinforcing material that connects the inner wall and the outer wall, The heat treatment apparatus according to claim 1 , wherein the material of the reinforcing member has a lower thermal conductivity than the material of the inner wall.

4. The heat treatment apparatus according to claim 3 , wherein the material of the reinforcing member has a specific heat greater than that of the material of the inner wall.

5. the heat treatment device includes a lid facing the treatment tank and closing the opening, and a packing disposed between the lid and the end surface material, 2. The heat treatment apparatus according to claim 1, wherein the position where the packing contacts the end surface material is a position where the packing faces the heat insulating material or a position where the packing faces outward from the heat insulating material.

6. 2. The heat treatment apparatus according to claim 1, wherein the temperature inside the treatment tank is controlled within a range of -196°C to +200°C.

7. the heat treatment device includes a lid facing the treatment tank and closing the opening, and a packing disposed between the lid and the end surface material, 2. The heat treatment apparatus according to claim 1, wherein the end surface of the end member facing the lid is flat, and the opposing surface of the lid facing the end member is flat.

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