Heat Treatment Equipment

Abstract

To provide a heat treatment device capable of suppressing leakage of an atmospheric gas from a boundary between adjacent muffles and the like in the plurally divided muffles.SOLUTION: A heat treatment device comprises: ceramic muffles 11 formed with heat treatment spaces S for heat-treating work-pieces W; and a metallic cover 30 covering the muffles 11. The muffles 11 are formed plurally divided, and the plurally divided muffles are arranged side by side so as to connect the heat treatment spaces S. The cover 30 comprises: plural main covers 31 covering a boundary K1 between neighboring muffles of the plurally divided muffles; and auxiliary covers 32 cross-linking the plural main covers 31.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Patent Document 1 discloses a heat treatment furnace that includes a retort in which the outside of a ceramic tube is covered with a metal shell, and is configured to heat treat a workpiece while transporting it in the axial direction inside the ceramic tube. In this heat treatment furnace, the ceramic tube is divided into multiple segments in the axial direction, and the multiple segments are inserted into one metal shell. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-83919 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the heat treatment furnace described in Patent Document 1, it is not easy to completely eliminate gaps at the boundaries between adjacent divided bodies of the ceramic tube, and there is a possibility that atmospheric gas may leak or external gas may infiltrate through these gaps. On the other hand, since the divided bodies are covered with a metal shell, the leakage of atmospheric gas from the gaps is suppressed to a certain extent. However, the metal shell is more susceptible to thermal deformation than the ceramic tube. Furthermore, the metal shell is composed of one long cylinder. And since the cylinder covers all of the divided bodies, it has a large volume. When the volume of the cylinder is large, the cylinder is more likely to be warped by heat. Therefore, the amount of deformation of the metal shell due to heat is large. Therefore, there is a risk that the metal shell will partially float up from the ceramic tube, and the gaps will not be sufficiently blocked.

[0005] An object of the present invention is to provide a heat treatment apparatus capable of suppressing leakage of atmospheric gas from the boundaries between adjacent muffles divided into a plurality of muffles. [Means for solving the problem]

[0006] (1) The present invention provides a heat treatment apparatus comprising a ceramic muffle having a heat treatment space formed therein for heat treating a workpiece, and a metal cover for covering the muffle, the muffle being divided into a plurality of muffles, the plurality of muffles being arranged in a line so as to connect the heat treatment space, The cover includes a main cover that covers the boundaries between adjacent muffles in the multiple divided muffles; and a sub-cover bridging the plurality of main covers.

[0007] According to the above configuration, the muffle divided into multiple parts is covered by the main cover and the sub-cover. That is, the cover is divided into the main cover and the sub-cover, and the area of ​​each single cover is small. Therefore, compared to a case where the cover is not divided, it is possible to suppress deformation of the main cover and the sub-cover due to heat. Therefore, it is possible to suppress the main cover from floating up from the muffle, and to suppress leakage of atmospheric gas from the boundary to the outside of the muffle and penetration of external gas into the muffle. In addition, the cover has a sub-cover that bridges the multiple main covers. Therefore, the main cover is pressed from the outside by the sub-cover. This further suppresses the main cover from floating up from the muffle.

[0008] (2) Preferably, at least one of the main covers covers a plurality of the boundaries. With this configuration, the total number of covers can be reduced compared to when one main cover is placed for one boundary.

[0009] (3) Preferably, the heat treatment apparatus includes a holding mechanism for limiting relative movement between the main cover and the sub-cover. With this configuration, it is possible to prevent the main cover and the sub-cover from coming apart from each other. Effect of the Invention

[0010] According to the present invention, in a muffle divided into a plurality of muffles, leakage of atmospheric gas from the boundaries between adjacent muffles can be suppressed. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic view of a heat treatment apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Diagram 3] FIG. 3 is a cross-sectional view of the muffle and cover taken along line BB in FIG. 2. [Figure 4] FIG. 2 is a schematic perspective view showing a muffle and a cover. [Diagram 5] 4A is a cross-sectional view of the cover at part C in FIG. 3, and FIG. 4B is a view taken along the line D in FIG. [Figure 6] 4 is a cross-sectional view of the cover at a portion E in FIG. 3. [Figure 7] FIG. 3 is a cross-sectional view of the muffle and cover in part F of FIG. 2. [Figure 8] FIG. 11 is a cross-sectional view showing a cover in a second embodiment of the present invention. [Figure 9] FIG. 11 is a cross-sectional view showing a holding mechanism in a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a schematic diagram of a heat treatment apparatus according to one embodiment of the present invention, Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, Fig. 3 is a cross-sectional view of a muffle taken along line BB in Fig. 2. The heat treatment apparatus of this embodiment is a continuous heat treatment furnace 10. The continuous heat treatment furnace 10 performs heat treatment while sequentially transporting a plurality of workpieces W. In the following description, the transport direction of the workpieces W is indicated by the symbol X, the width direction of the muffle 11 perpendicular to the transport direction X of the workpieces W is indicated by the symbol Y, and the up-down direction perpendicular to the directions X and Y is indicated by the symbol Z.

[0013] The continuous heat treatment furnace 10 includes a muffle 11, a conveying device 12, a heat insulating wall 13, a heating device 14, a gas supply pipe 15, a cover 30, and the like. The muffle 11 is formed in a cylindrical shape and has a heat treatment space S therein. The muffle 11 is formed long in the transport direction X of the workpiece W, and the heat treatment space S also extends in the same direction X. Therefore, the workpiece W is transported in the longitudinal direction of the muffle 11. In the following description, the longitudinal direction of the muffle 11 may also be denoted by the symbol X.

[0014] The muffle 11 has a bottom 21, a pair of sidewalls 22, and a ceiling 23. A space surrounded by the bottom 21, the sidewalls 22, and the ceiling 23 forms a heat treatment space S.

[0015] The bottom 21 of the muffle 11 has a flat upper surface 21a. The pair of side wall portions 22 extend linearly upward from both ends of the bottom portion 21 in the width direction Y of the muffle 11. The ceiling portion 23 is provided so as to straddle the upper ends of the pair of side wall portions 22.

[0016] In the muffle 11 of this embodiment, the side wall portion 22 and the ceiling portion 23 are integrated, and these are configured as separate bodies from the bottom portion 21. The lower ends of the pair of side wall portions 22 are in contact with the upper surface 21a of the bottom portion 21. The muffle 11 of this embodiment is also formed of ceramic, which is a nonmetallic heat-resistant material. Ceramics are nonmetallic / inorganic solid materials, and include materials other than metal materials such as iron, aluminum, and copper, and organic materials such as plastics and wood. More specifically, typical ceramics include old ceramics such as pottery, refractory materials (firebricks), glass, and cement, as well as new ceramics (fine ceramics).

[0017] The muffle 11 is divided into a plurality of parts. Specifically, the muffle 11 is composed of a plurality of divided bodies 40, and is configured by arranging the plurality of divided bodies 40 in the conveying direction X of the workpiece W. The divided bodies 40 are composed of a lower divided body 11A constituting the bottom portion 21, and an upper divided body 11B constituting the side wall portion 22 and the ceiling portion 23.

[0018] As shown in FIG. 1, a cylindrical or gate-shaped metal chamber 18 is connected to both ends of the muffle 11 in the transport direction X of the workpiece W, in other words, to the relatively low temperature areas of the inlet and outlet of the workpiece W in the muffle 11.

[0019] The conveying device 12 conveys the workpiece W in the heat treatment space S in the muffle 11 in the longitudinal direction X of the muffle 11. In this embodiment, a plurality of (for example, three) conveying devices 12 are arranged side by side at intervals in the width direction Y of the muffle 11. The conveying device 12 in this embodiment is a chain conveyor having a conveying chain 12a and sprockets 12b and 12c. The chain 12a moves on a rail 21b provided on the upper surface 21a of the bottom 21 of the muffle 11. The chain 12a is wound around a driving sprocket 12b and a driven sprocket 12c, and moves in the longitudinal direction X in the muffle 11. A tray T for placing the workpiece W is provided on the chain 12a. In this embodiment, a plurality of trays T are stacked at intervals in the vertical direction Z, and the workpiece W is placed on each tray T. The conveying device 12 may be of another type, such as a belt conveyor or a roller conveyor.

[0020] 2, the insulating wall 13 has a lower insulating wall 13a arranged below the muffle 11, side insulating walls 13b arranged on both sides of the muffle 11 in the width direction Y, and an upper insulating wall 13c above the muffle 11. The muffle 11 is arranged in a space surrounded by the lower insulating wall 13a, the side insulating wall 13b, and the upper insulating wall 13c. The insulating wall 13 can be made of a thermal insulating material formed into a thick plate shape using, for example, ceramic fiber.

[0021] The heating device 14 has a heater disposed below the muffle 11. The heating device 14 heats the muffle 11 from the outside, and heats the heat treatment space S in the muffle 11 to a predetermined temperature. The heating device 14 may be an electric resistance heating type or a gas combustion heating type. The arrangement and type of the heating device 14 are not particularly limited, and may be disposed, for example, on the side of the muffle 11 in the width direction Y, above the muffle 11, or the like. The heating device 14 may be embedded in the insulating wall 13.

[0022] The gas supply pipe 15 generates a predetermined atmosphere by supplying gas into the muffle 11. In this embodiment, for example, nitrogen gas is used. The gas supply pipe 15 is disposed so as to run along the upper surface 21a of the bottom 21 of the muffle 11. Specifically, the gas supply pipe 15 is placed on the upper surface 21a of the bottom 21 and is supported from below by the upper surface 21a.

[0023] The gas supply pipe 15 extends in the conveying direction X of the workpiece W. The gas supply pipe 15 is provided on both outer sides of the conveying device 12 in the width direction Y of the muffle 11 and between the adjacent conveying devices 12. Therefore, in this embodiment, a total of four gas supply pipes 15 are provided in the muffle 11. An outlet port for discharging gas is formed on the outer circumferential surface of the gas supply pipe 15. A plurality of outlet ports are formed at intervals in the conveying direction X of the workpiece W. The gas supply pipes 15 arranged on both outer sides of the conveying device 12 in the width direction Y of the muffle 11 have outlet ports formed so as to discharge gas obliquely upward toward the workpiece W located inside in the same direction Y. Each gas supply pipe 15 arranged between the adjacent conveying devices 12 has an outlet port formed so as to discharge gas obliquely upward toward the workpiece W arranged on both sides of the width direction Y of the muffle 11.

[0024] Of the two gas supply pipes 15 arranged between the adjacent transport devices 12, one of the gas supply pipes 15 is adjacently arranged with a gas introduction pipe 16. In this embodiment, the two gas introduction pipes 16 are adjacently arranged on both sides of the gas supply pipe 15 in the width direction Y of the muffle 11. This gas introduction pipe 16 is used to introduce a gas within the muffle 11 and send it out of the muffle 11 in order to detect the concentration of a predetermined gas within the muffle 11, etc.

[0025] FIG. 4 is a schematic perspective view showing the muffle and the cover. 2 to 4, the cover 30 covers the muffle 11 from the outside. Specifically, the cover 30 covers the side wall portion 22 and the ceiling portion 23 of the muffle 11 from the outside. Therefore, the cover 30 is formed into a U-shape with an open bottom by a portion 30a covering the side wall portion 22 and a portion 30b covering the ceiling portion 23. The cover 30 is formed from a heat-resistant metal, for example, a nickel alloy such as Inconel 601 ("Inconel" is a registered trademark) or stainless steel such as SUS310 or SUS304.

[0026] The cover 30 includes a main cover 31 and a sub-cover 32. A plurality of main covers 31 and a plurality of sub-covers 32 are provided. The main covers 31 and the sub-covers 32 are arranged alternately in the transport direction X of the workpiece W. Therefore, the plurality of main covers 31 are arranged at intervals in the transport direction X of the workpiece W, and the plurality of sub-covers 32 are arranged at intervals in the transport direction X of the workpiece W. The interval between the main covers 31 arranged side by side in the transport direction X of the workpiece W is set so that they do not interfere with each other when the main covers 31 stretch due to heat. The interval between the sub-covers 32 arranged side by side in the transport direction X of the workpiece W is set so that they do not interfere with each other when the sub-covers 32 stretch due to heat.

[0027] Each main cover 31 covers the boundary K1 between adjacent divided bodies 40 of the muffle 11. Specifically, the main cover 31 has a length in the conveying direction X of the workpiece W that is slightly longer than the length of the divided body 40 in the same direction X, and straddles two boundaries K1 located on both sides of each divided body 40, covering these two boundaries K1 from the outside. Therefore, the main cover 31 suppresses the atmospheric gas in the muffle 11 from leaking from the boundary K1 of the divided body 40 and the infiltration of external gas into the muffle 11.

[0028] Each sub-cover 32 is disposed across adjacent main covers 31 in the transport direction X of the workpiece W. In other words, the sub-cover 32 is disposed across adjacent main covers 31, bridging both main covers 31. Each sub-cover 32 covers the end of the adjacent main cover 31 from the outside. Therefore, the main cover 31 and the sub-cover 32 overlap each other at their ends in the transport direction X of the workpiece W. The sub-cover 32 is formed one size larger than the main cover 31, and is disposed with a gap equivalent to the thickness of the main cover 31 from the outer surface of the muffle 11.

[0029] The sub-cover 32 holds down the main cover 31 by covering the end of the main cover 31 from the outside. In particular, the portion of the main cover 31 covering the ceiling portion 23 of the muffle 11 is held down from above by the weight of the sub-cover 32. This makes the sub-cover 32 a "weight" for the main cover 31, and can suppress the main cover 31 from floating up from the muffle 11. In addition, the portion of the main cover 31 covering the side wall portion 22 of the muffle 11 is held down from the outside in the width direction Y of the muffle 11 by the sub-cover 32. This can suppress the main cover 31 from spreading outward or floating up from the muffle 11 in the width direction Y of the muffle 11. Therefore, the sub-cover 32 enhances the effect of the main cover 31 blocking the boundary K1 of the divided body 40, and can effectively suppress the leakage of atmospheric gas and the intrusion of external gas from the boundary K1. In addition, the sub-cover 32 further prevents outside air from entering the muffle 11 by sealing the gap between adjacent main covers 31 .

[0030] The main cover 31 and the sub-cover 32 cover the entire muffle 11 from the outside, thereby preventing heat from the muffle 11 from escaping to the outside. The main cover 31 and the sub-cover 32 also prevent uneven heat distribution throughout the muffle 11. The main cover 31 and the sub-cover 32 are made of metal and have the property of absorbing oxygen. Therefore, for example, if it is desired to fill the inside and outside of the muffle 11 with a predetermined gas such as nitrogen gas and maintain the atmosphere within the muffle 11 in a low-oxygen state, the main cover 31 and the sub-cover 32 can absorb oxygen, making it easier to maintain the atmosphere within the muffle 11 in a low-oxygen state.

[0031] The cover 30 is divided into a main cover 31 and a sub-cover 32, and the volume of each cover is small, so that the thermal deformation of each cover 31, 32 can be reduced compared to when the entire cover is composed of a single cover. This makes it possible to prevent the main cover 31 from lifting up from the boundary K1 of the divided body 40. Similarly, since the thermal deformation of the sub-cover 32 can be reduced, it is possible to prevent the sub-cover 32 from lifting up from the main cover 31, and ensure the effect of the sub-cover 32 holding down the main cover 31.

[0032] The main cover 31 and the sub-cover 32 have approximately the same length in the transport direction X of the workpiece W. Therefore, the amount of deformation due to heat is approximately the same for both covers. In other words, the main cover 31 and the sub-cover 32 can be assumed to have approximately the same range in which they are likely to warp and rise due to heat, making it easier to manage the overlapping margin between the covers 31 and 32 that is required for the sub-cover 32 to press the main cover 31. As a result, the gap between the covers 31 and 32 is also suppressed, and the occurrence of a gap between the muffle 11 and the cover 30 can be suppressed.

[0033] 5(a) is a cross-sectional view of the cover at part C in FIG. 3, and FIG. 5(b) is a view seen from the direction of arrow D in FIG. 5(a). The main cover 31 and the sub-cover 32 are restricted in relative movement in the transport direction X of the workpiece W. Specifically, a rod-shaped protrusion 51 is provided on the outer surface of the end of the main cover 31 so as to protrude upward. A hole 52 into which the protrusion 51 is inserted is formed at the end of the sub-cover 32. The hole 52 is an elongated hole that is long in the transport direction X of the workpiece W. In this embodiment, the protrusion 51 and the hole 52 are provided in the portion 30b of the main cover 31 and the sub-cover 32 that covers the ceiling portion 23 of the muffle 11. However, the protrusion 51 and the hole 52 may be provided in the portion 30a of the main cover 31 and the sub-cover 32 that covers the side wall portion 22 of the muffle 11.

[0034] When the main cover 31 and the sub-cover 32 expand in the transport direction X of the workpiece W due to heat, the relative movement between them is permitted within the range of the length of the hole 52, and the relative movement in the transport direction X of the workpiece W is restricted in a range exceeding the length of the hole 52. This restriction of the relative movement maintains the state in which the main cover 31 and the sub-cover 32 are overlapped, and maintains the state in which the main cover 31 covers the boundary K1 between the adjacent divided bodies 40. Therefore, leakage of atmospheric gas from the boundary K1 is suppressed. Here, the protrusions 51 and the holes 52 constitute a holding mechanism 50 that maintains the state in which the main cover 31 covers the boundary K1 between the adjacent divided bodies 40. In addition, the holding mechanism 50 maintains the state in which the main cover 31 and the sub-cover 32 cover the muffle 11 from the outside, thereby suppressing the heat of the muffle 11 from escaping to the outside.

[0035] The length of the hole 52 of the retaining mechanism 50 (the relative movement amount between the main cover 31 and the sub-cover 32) is set so that the main cover 31 and the sub-cover 32 are maintained overlapping and covering the boundary K1, depending on the amount of overlap between the main cover 31 and the sub-cover 32, the amount of thermal expansion of the main cover 31 and the sub-cover 32, etc.

[0036] FIG. 6 is a cross-sectional view of the cover at a portion E in FIG. The main cover 31 arranged at the end of the conveying direction X of the work W has one end connected to the sub-cover 32 via a holding mechanism 50, and the other end is fixed to the metal chamber 18 connected to the inlet and outlet of the muffle 11. Specifically, a rod-shaped protrusion 53 is provided on the outer surface of the metal chamber 18 so as to protrude upward, and a hole 54 into which the protrusion 53 is inserted is formed at the end of the main cover 31. The hole 54 is a round hole having an inner diameter slightly larger than the diameter of the protrusion 53. Therefore, the main cover 31 in which the hole 54 is formed is substantially fixed to the metal chamber 18. In this way, by fixing the main covers 31 arranged at both ends of the conveying direction X of the work W in the same direction X, the amount of movement of the other main covers 31 and sub-covers 32 arranged therebetween can be limited, and the overlap between the main cover 31 and the sub-cover 32 can be suppressed from coming off. Furthermore, it is possible to suppress the main covers 31 from being displaced from the boundary K1 of the divided body 40 due to the accumulation of the movements of these covers 31 and 32.

[0037] FIG. 7 is a cross-sectional view of the muffle and cover at part F in FIG. 7, in the main cover 31, the portion 30a covering the side wall portion 22 of the muffle 11 covers from the outside the boundary K2 between the side wall portion 22 and the bottom portion 21. Therefore, it is possible to suppress leakage of the atmospheric gas from the boundary K2 and infiltration of the external gas from the boundary K2.

[0038] FIG. 8 is a cross-sectional view showing a cover according to the second embodiment of the present invention. In this embodiment, the multiple main covers 31 each cover one boundary K1 between adjacent divided bodies 40. Therefore, each main cover 31 has a shorter length in the transport direction X of the workpiece W than the main cover 31 in the first embodiment. In addition, the sub-covers 32 overlapping the main cover 31 have a narrower interval between adjacent ones in the transport direction X of the workpiece W.

[0039] This embodiment also has the same effect as the above embodiment. In addition, in this embodiment, the multiple main covers 31 each cover one boundary K1 between adjacent divided bodies 40. Therefore, the main cover 31 only needs to cover the periphery of at least one boundary K1, so that the length in the conveying direction X of the workpiece W can be formed shorter than that of the first embodiment. Therefore, the main cover 31 can have a smaller area than the main cover 31 of the first embodiment, and the amount of deformation due to heat can be reduced compared to the main cover 31 of the first embodiment. Therefore, the lifting of the main cover 31 from the divided body 40 can be further suppressed, and the leakage of the atmospheric gas from the boundary K1 to the outside of the muffle 11 and the intrusion of the external gas into the muffle 11 can be suppressed.

[0040] FIG. 9 is a cross-sectional view showing a holding mechanism according to the third embodiment of the present invention. In this embodiment, the configuration of the holding mechanism 50 is different from that in the above-described embodiment. In this embodiment, a rod-shaped protrusion 55 is provided on the inner surface of the end of the sub-cover 32 so as to protrude downward. The amount of protrusion of the protrusion 55 is smaller than the thickness of the main cover 31. A groove 56 into which the protrusion 55 is inserted is formed on the outer surface of the end of the main cover 31. The groove 56 is a long groove that is long in the transport direction X of the workpiece W.

[0041] Therefore, in this embodiment as well, the relative movement between the main cover 31 and the auxiliary cover 32 in the transport direction X of the workpiece W is limited within the range of the length of the groove 56, the main cover 31 and the auxiliary cover 32 are maintained in an overlapping state, and the main cover 31 is maintained in a state covering the boundary K1.

[0042] In this embodiment, the groove 56 can be changed to a hole penetrating the main cover 31. Also, in the first embodiment shown in Fig. 5, the amount of protrusion of the projection 51 can be made smaller than the thickness of the sub-cover 32, and the hole 52 can be changed to a groove (long groove) formed in the lower surface of the sub-cover 32.

[0043] The continuous heat treatment furnace 10 according to the embodiment described above includes a non-metallic muffle 11 having a heat treatment space S formed therein for heat-treating the workpiece W being transported, and a metallic cover 30 covering the outside of the muffle 11. The muffle 11 has at least three divided bodies 40 (for example, three divided bodies arranged side by side in FIG. 3 and FIG. 8; hereinafter, these are also referred to as a "first divided body", a "second divided body", and a "third divided body"). These first to third divided bodies 40 are arranged in the transport direction X of the workpiece W. The cover 30 has a main cover (hereinafter, also referred to as a "first main cover") 31 that covers the boundary K1 between the first divided body 40 and the second divided body 40, and a main cover (hereinafter, also referred to as a "second main cover") 31 that covers the boundary K1 between the second divided body 40 and the third divided body 40. With this configuration, the multiple boundaries K1 of the divided bodies 40 are covered by the multiple main covers 31. Therefore, the cover 30 is divided into a plurality of main covers 31, and the area of ​​each cover is reduced. Therefore, it is possible to suppress deformation of each main cover 31 due to heat, compared to a case where the cover 30 is not divided. This makes it possible to suppress lifting of each main cover 31 from the muffle 11, and to suppress leakage of atmospheric gas from the boundary K1 to the outside of the muffle 11 and infiltration of external gas into the muffle 11.

[0044] In the above embodiment, the cover 30 is disposed across the first main cover 31 and the second main cover 31, and has the sub-cover 32 that overlaps the first main cover 31 and the second main cover 31 from the outside. Therefore, the first and second main covers 31 are pressed from the outside by the sub-cover 32, and the boundary K1 between the adjacent divided bodies 40 can be covered by the first and second main covers 31. In particular, the first and second main covers 31 are pressed from above by the weight of the sub-cover 32. Therefore, the sub-cover 32 acts as a weight for the first and second main covers 31, and the first and second main covers 31 are prevented from floating up from the muffle 11.

[0045] In the above-described first embodiment, the muffle 11 further has a divided body 40 (hereinafter also referred to as a "fourth divided body") arranged side by side with the third divided body 40 in the transport direction X of the workpiece W, and the second main cover 31 also covers the boundary K1 between the third divided body 40 and the fourth divided body 40. In other words, the cover 30 has the second main cover 31 that covers a plurality of boundaries K1. Therefore, the total number of covers 30 can be reduced compared to the case where the second main cover 31 covers only one boundary K1.

[0046] In the above embodiment, the continuous heat treatment furnace 10 is provided with a holding mechanism 50 that limits the relative movement between the first main cover 31, the second main cover 31, and the sub-cover 32 that straddles them. This makes it possible to prevent the first and second main covers 31 and the sub-cover 32 from coming out of overlap with each other. Furthermore, by providing the holding mechanism 50, it is possible to prevent the first and second main covers 31 from shifting from the boundary K1. Therefore, it is possible to prevent the atmospheric gas from leaking from the muffle 11 and the external gas from entering the muffle 11.

[0047] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention described in the claims.

[0048] For example, the main cover 31 may have a length in the conveying direction X of the workpiece W that covers three or more boundaries K1. The cover 30 may also be provided with multiple types of main covers 31 that differ in the number of boundaries K1 that can be covered. For example, for manufacturing reasons such as ease of fabrication of the muffle 11, if the individual divided bodies 40 are formed small and a large number of these divided bodies 40 are arranged, it is more effective to combine and arrange multiple types of main covers 31 as described above.

[0049] For example, in the muffle 11, the side wall portion 22 and the ceiling portion 23 are configured as separate bodies from the bottom portion 21, but this is not limited thereto. For example, the muffle 11 may be an integral body. Also, the muffle 11 may have the side wall portion 22 and the bottom portion 21 integrated with the ceiling portion 23 being a separate body. Also, the muffle 11 may have an upper and lower portions configured as separate bodies with the middle portion of the side wall portion 22 in the vertical direction Z as the boundary.

[0050] Although the cover 30 covers the side wall portion 22 and the ceiling portion 23 of the muffle 11 in the above embodiment, the cover 30 may cover either one of them. Also, the cover 30 may cover the bottom portion 21. [Explanation of symbols]

[0051] 10: Continuous heat treatment furnace 11: Muffle 30: Cover 31: Main cover 32: Secondary cover 40: Divided body 50: Holding mechanism K1: Boundary K2: Boundary S: Heat treatment space W: Work X: Transport direction

Claims

1. A heat treatment apparatus comprising: a ceramic muffle having a heat treatment space formed therein for heat treating a workpiece; and a metal cover covering the muffle, the muffle being divided into a plurality of muffles, the plurality of muffles being arranged in a line so as to connect the heat treatment space; The cover includes a main cover that covers the boundaries between adjacent muffles in the multiple divided muffles; and a sub-cover bridging the plurality of main covers.

2. The thermal processing apparatus of claim 1 , wherein at least one of the main covers covers a plurality of the boundaries.

3. The heat treatment apparatus according to claim 1 , further comprising a holding mechanism for limiting relative movement between the main cover and the sub-cover.

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