CN113959222B

CN113959222B - High temperature furnace

Info

Publication number: CN113959222B
Application number: CN202111423462.0A
Authority: CN
Inventors: 于雪; 何虎; 秦少鹏; 吴胜娜; 李鑫; 李鑫酉; 罗志福; 刘国辉
Original assignee: China Institute of Atomic of Energy
Current assignee: China Institute of Atomic of Energy
Priority date: 2021-11-26
Filing date: 2021-11-26
Publication date: 2022-10-28
Anticipated expiration: 2041-11-26
Also published as: CN113959222A

Abstract

The embodiment of the invention discloses a high-temperature furnace, which comprises: furnace body, bell, heat-insulating body, interior furnace body and electric heating body. The furnace body limits and forms the top and has the holding chamber of open-ended. The furnace cover is used for opening or closing the opening of the accommodating cavity. The heat preservation body detachably install hold the intracavity, the heat preservation body is inside to be formed with the heat preservation chamber. The inner furnace body is detachably arranged in the heat preservation cavity and is used for accommodating a sample to be heated. The electric heating body is detachably arranged in the heat preservation cavity and used for heating the inner furnace body. According to the technical scheme, a user can replace different heat insulators and/or inner furnace bodies according to different requirements, and the use scene of the high-temperature furnace is increased.

Description

High temperature furnace

Technical Field

The invention relates to the technical field of high-temperature furnaces, in particular to a high-temperature furnace.

Background

The hearth material of the high-temperature furnace basically determines the use temperature of the high-temperature furnace. For example, the use temperature of the graphite hearth can reach more than 1500 ℃; the service temperature of the quartz hearth can only reach 1100 ℃ at most. In addition, in the heating process, harmful gas, water vapor and/or oil vapor can be generated after a sample in the hearth is subjected to high temperature, so that different use scenes have different requirements on the oxidation resistance and the corrosion resistance of the hearth.

Disclosure of Invention

The embodiment of the invention provides a high-temperature furnace, which comprises:

a furnace body defining a receiving chamber having an opening formed thereon;

the furnace cover is used for opening or closing the opening of the accommodating cavity;

the heat insulation body is detachably arranged in the accommodating cavity, and a heat insulation cavity is formed in the heat insulation body;

the inner furnace body is detachably arranged in the heat-insulating cavity and is used for accommodating a sample to be heated; and

and the electric heating body is detachably arranged in the heat insulation cavity and is used for heating the inner furnace body.

The embodiment of the invention provides the high-temperature furnace with the hearth convenient to replace, thereby increasing the use scenes of the high-temperature furnace.

Drawings

Other objects and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings, and will assist in a comprehensive understanding of the invention.

FIG. 1 is a schematic block diagram of a high temperature furnace according to an embodiment of the invention;

FIG. 2 is a schematic view of the high temperature furnace shown in FIG. 1 with the furnace body and furnace cover omitted;

FIG. 3 is a schematic illustration of the insulation of FIG. 1;

FIG. 4 is a schematic and diagrammatic view of a high temperature furnace according to another embodiment of the present invention; and

fig. 5 is a schematic diagram of the protective container shown in fig. 4.

In the drawings:

10. a high temperature furnace; 11. a furnace body; 110. an accommodating chamber; 111. a power supply interface; 112. an exhaust interface; 113. a control valve; 114. an air inlet interface; 115. a vacuum pumping port; 12. a furnace cover;

20. a thermal insulator; 21. a heat preservation body; 211. a first abdicating channel; 212. a heat preservation cavity; 213. installing a channel; 214. a second yield channel; 215. a wire channel; 22. a heat-preserving cover body;

30. a protective container; 31. a container body; 310. an air outlet channel; 311. an air outlet pipeline; 312. a wire transfer interface; 313. sealing the cavity; 314. an air inlet; 315. an air intake line; 32. a container lid;

40. an inner furnace body; 50. an electric heater; 51. an electrical wire interface; 52. a line; 60. a support plate; 70. a support; 80. a connecting rod.

It should be noted that the figures are not drawn to scale and that elements of similar structure or function are generally represented by like reference numerals throughout the figures for illustrative purposes. It should also be noted that the drawings are only for convenience in describing the preferred embodiments and are not intended to limit the invention itself. The drawings do not show every aspect of the described embodiments and do not limit the scope of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. It should be apparent that the described embodiment is one embodiment of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.

Fig. 1 is a schematic diagram of a high temperature furnace according to an embodiment of the present application. As shown in fig. 1, the high temperature furnace 10 of the embodiment of the present application may include: furnace body 11, furnace cover 12, heat insulator 20, inner furnace body 40 and electric heater 50.

The furnace body 11 defines a receiving chamber 110 having an opening formed thereon. The furnace cover 12 is used to open or close the opening of the receiving chamber 110. In some embodiments, the lid 12 is pivotally attached to the body 11. For example, the furnace lid 12 may be pivotally connected to the upper end of the furnace body 11 by a pivot. In other embodiments, the furnace cover 12 may be directly covered on the furnace body 11.

The insulation 20 is removably mounted within the receiving cavity 110. The thermal insulator 20 is made of a thermal insulating material. The heat insulating material is low density porous ceramic, rock wool, aluminum silicate, foam glass, etc. The insulation 20 may be a porous structure.

Fig. 2 is a schematic view of the high temperature furnace shown in fig. 1, with the furnace body and the furnace cover omitted. Referring to fig. 2, the insulation 20 has an insulation cavity 212 formed therein.

The insulation 20 may include an insulation body 21 and an insulation cover 22. The thermal insulation body 21 defines a groove with an opening at the upper part; the thermal insulation cover 22 covers the thermal insulation body 21 and defines a thermal insulation cavity 212 together with the thermal insulation body 21.

The inner furnace body 40, which may also be referred to as a firebox, is removably mounted within the holding chamber 212 for holding a sample to be heated. And the electric heater 50 is detachably arranged in the heat preservation cavity 212 and is used for heating the inner furnace body 40. The electric heater 50 may be installed as an integrated structure with the inner furnace body 40, thereby reducing a disassembly and assembly process. Of course, the electric heater 50 may be provided separately from the inner furnace body 40.

In some embodiments, the electric heater 50 may surround the outer surface of the circumferential wall of the inner furnace body 40. For example, the electric heater 50 may include a plurality of electric heating tubes that surround the outer surface of the circumferential wall of the inner furnace body 40 with or without space.

With the high temperature furnace 10 of the embodiment of the present application, since the heat insulator 20 is detachably installed in the accommodating cavity 110 of the furnace body 11, and the inner furnace body 40 and the electric heating body 50 are detachably installed in the heat insulating cavity 212 of the heat insulator 20, the heat insulator 20 of the high temperature furnace 10 can be replaced alone or the inner furnace body 40 and the electric heating body 50 of the high temperature furnace 10 can be replaced alone, or the heat insulator 20 and the inner furnace body 40 and the electric heating body 50 of the high temperature furnace 10 can be replaced simultaneously. Therefore, the high temperature furnace 10 of the embodiment of the present application can change the use temperature of the high temperature furnace 10 according to the user's requirement, and the temperature range of the high temperature furnace 10 is expanded.

In addition, the heat preservation body 20 of different materials is applicable to the different samples of heating, because the heat preservation body 20 of removable high temperature furnace 10 of this application to the kind of the sample that high temperature furnace 10 was suitable for the heat treatment has been expanded.

Since the heat insulator 20, the inner furnace body 40 and the electric heater 50 of the high temperature furnace 10 are all detachable, the problem of wiring of the electric heater 50 needs to be considered.

Referring to fig. 1, in the embodiment of the present application, a power supply interface 111 is provided on a furnace wall of the furnace body 11; the electric heater 50 has an electric wire interface 51, and the electric wire interface 51 of the electric heater 50 is electrically connected to the power supply interface 111 through a line 52.

Referring to fig. 2, the insulation 20 is provided with a wire channel 215 for passage of the wires 52.

The two ends of the line 52 may be respectively provided with connectors to be respectively plugged with the power supply interface 111 and the wire interface 51, thereby facilitating the disassembly and assembly.

The power supply interface 111 may be a CF interface, and a sealing terminal is used to ensure the sealing of the furnace body 11.

In some embodiments, the high temperature furnace 10 includes more than two insulation bodies 20, each insulation body 20 being of a different material; an insulation body 20 is detachably mounted in the receiving chamber 110. In other words, the high temperature furnace 10 of the present application may be provided with a plurality of heat insulators 20, so that heat insulators 20 of different materials may be used when facing different temperatures or processing different materials.

For example, when the temperature of the high temperature furnace 10 is lower than 800 degrees centigrade, the rock wool heat insulator 20 may be used, and when the temperature of the high temperature furnace 10 is higher than 1000 degrees centigrade, the ceramic heat insulator 20 may be used.

In some embodiments, the high temperature furnace 10 includes more than two inner furnace bodies 40, and the material of each inner furnace body 40 is different; an inner furnace body 40 is detachably mounted in the holding chamber 212. In other words, the high temperature furnace 10 of the present application may be provided with a plurality of inner furnace bodies 40, so that inner furnace bodies 40 of different materials may be used when facing different use temperatures or processing different materials. The material of the inner furnace body 40 may be quartz, graphite, high alumina brick, corundum, etc.

Referring to fig. 1, the peripheral wall of the heat insulator 20 is spaced apart from the furnace body 11 and the furnace cover 12. In other words, the peripheral wall of the heat insulator 20 does not contact the furnace body 11 and the furnace cover 12, and thus a thermal insulating layer of air is formed between the heat insulator 20 and the furnace body 11, thereby further improving the thermal insulating effect.

The high temperature furnace 10 may further include: and a support portion for supporting the heat insulator 20 in the receiving chamber 110.

Referring to fig. 1, the support may be a support plate 60 disposed at the bottom of the thermal insulator 20. Thus, the heat insulator 20, the inner furnace body 40 and the electric heater 50, etc. contained therein are supported by the support plate 60.

In an alternative embodiment, the support portion may also be a support frame.

The high temperature furnace may further include: at least one support 70 arranged on the bottom wall of the furnace body 11; the support plate 60 is removably mounted to at least one support 70.

The support of the support 70 can fix the position of the heat insulator 20 and prevent the heat insulator 20 from directly contacting with the peripheral wall of the furnace body 11, thereby reducing the heat conduction between the heat insulator 20 and the furnace body 11.

To further ensure the thermal insulation effect, the support 70 is made of a thermal insulation material (i.e., a non-thermally conductive material). For example, the support 70 may be made of ceramic.

The support 70 may be fixedly disposed on the bottom wall of the furnace body 11. The number of the holders 70 may be plural, and the plural holders 70 are provided at intervals on the bottom wall of the furnace body 11. The number of standoffs 70 can be, for example, 2, 3, 4, or more.

The high temperature furnace 10 further includes: and a mounting portion for detachably mounting the heat insulator 20 and the support plate 60 to the holder 70.

Referring to fig. 1 and 2, the mounting portion is a connecting rod 80, the connecting rod 80 penetrates through the thermal insulation body 21 and the support plate 60, the upper end of the connecting rod 80 is detachably connected with the thermal insulation body 21, and the lower end of the connecting rod 80 is detachably connected with the support 70.

Referring to fig. 3, the heat insulation body 21 may be provided with an installation channel 213, and the support plate 60 may be provided with an abdicating through hole for the connection rod 80 to pass through.

The upper and lower ends of the connecting rod 80 may be respectively provided with screw threads, and accordingly, a screw hole is formed in the support 70, and screw threads are provided in the installation passage 213, so that the connecting rod 80 is screw-coupled to the thermal insulation body 21 and the support 70.

In an embodiment not shown, the upper end of the connecting rod 80 may also extend through the insulating cover 22. It will be readily appreciated that the mounting channel 213 may not be threaded, but rather may be a nut fit to provide a removable connection between the insulation 20, support plate 60 and support 70.

In some embodiments, the furnace 11 has evacuation ports 115 in the walls thereof. Thus, the high temperature furnace 10 of the embodiment of the present application can be used for vacuum heat treatment.

In some embodiments, the furnace wall of the furnace body 11 is provided with an air inlet port 114 for the gas to enter the accommodating chamber 110. Therefore, the high temperature furnace 10 of the embodiment of the present application may be vented to the protective atmosphere through the gas inlet port 114 during the heating process.

In some embodiments, the furnace body 11 is provided with an exhaust interface 112 on the wall thereof for exhausting the gas in the accommodating chamber 110 to the outside.

Fig. 4 is a schematic view of a high temperature furnace according to another embodiment of the present invention. Referring to fig. 4, in some embodiments, the high temperature furnace 10 may further include: the protective container 30 is detachably arranged in the heat preservation cavity 212. A sealed chamber 313 is formed inside the protective container 30, and both the inner furnace body 40 and the electric heating body 50 are detachably disposed in the sealed chamber 313.

In the embodiment of the application, the protective container 30 is arranged, so that the inner furnace body 40 can be isolated from the heat insulator 20, and gas generated after the sample in the inner furnace body 40 is heated can be prevented from being adsorbed by the heat insulator 20, or the sample or gas generated by heating the sample can be prevented from reacting with the heat insulator 20, so that adverse effect can be caused on the heat insulator 20, or adverse effect can be caused on the next heated sample; or prevent the insulator 20 from generating gas to affect the sample in the inner furnace body 40.

Referring to fig. 5, the protective container 30 includes: a container body 31 and a container lid 32. The container body 31 defines a recess with an opening formed above; the container cover 32 is disposed on the container body 31 and forms a sealed cavity 313 together with the groove of the container body 31.

The container body 31 is provided with an air outlet pipeline 311 communicated with the sealing cavity 313, and the air outlet pipeline 311 is detachably connected with the exhaust interface 112 in a sealing way. Referring to fig. 1 to 3, a first relief passage 211 for allowing the outlet pipe 311 to pass therethrough is formed inside the heat insulator 20. It will be readily appreciated that for embodiments where the high temperature furnace 10 includes a plurality of insulation bodies 20, the insulation bodies 20 may not all be provided with the first yield channel 211, i.e., some insulation bodies 20 are provided with the first yield channel 211 and some insulation bodies 20 are not provided with the first yield channel 211. The insulation 20 can be installed in the receiving cavity 110 as required.

According to the embodiment of the application, the gas outlet pipeline 311 is arranged, so that gas generated by heating the sample in the inner furnace body 40 is discharged to the outside of the high-temperature furnace 10 through the gas outlet pipeline 311 and the exhaust interface 112, and adverse effects on the heat insulator 20 are avoided.

Referring to fig. 5, the gas outlet line 311 may be provided at the bottom of the container body 31. In other words, the bottom of the container body 31 is provided with an air outlet communicating with the seal chamber 313, and the air outlet line 311 communicates with the air outlet.

Of course, the air outlet pipe 311 may be provided on the peripheral wall of the container body 31 or the container lid 32.

The bottom of the container body 31 is contracted to form a funnel-shaped air outlet channel 310, and the air outlet pipeline 311 is communicated with the air outlet channel 310. With the funnel-shaped air outlet channel 310, after the sample in the inner furnace 40 is heated, the temperature of the sample in the inner furnace 40 is lowered, and at this time, the gas in the container body 31 may be liquefied into liquid, and the liquid may automatically flow into the funnel-shaped air outlet channel 310 under the action of gravity and further flow to the air outlet interface 112 through the air outlet pipeline 311.

It is easily understood that the accommodating space of the inner furnace body 40 for accommodating the sample to be heated is communicated with the sealed cavity 313, so that the gas generated by heating the sample in the inner furnace body 40 enters the sealed cavity 313.

Referring to fig. 4, the inner furnace body 40 may define an accommodating space having an opening formed thereon. In an alternative embodiment, the inner furnace body 40 may also define a receiving space with a lateral opening.

In some embodiments, there may be a gap between the outer circumferential surface of the inner furnace body 40 and the circumferential wall of the protective container 30.

For example, the inner furnace body 40 may have a transverse dimension (e.g., an inner diameter or a side length) smaller than that of the sealed cavity 313, the inner furnace body 40 may have a height smaller than that of the sealed cavity 313, and the inner furnace body 40 may be supported in the sealed cavity 313 by supports disposed at intervals, so that the accommodating space of the inner furnace body 40 communicates with the sealed cavity 313. Thus, the gas in the inner furnace body 40 can enter the sealing cavity 313 and then enter the gas outlet pipeline 311 through the sealing cavity 313.

Referring to fig. 5, in some embodiments, the container body 31 is provided with an air inlet 314, which is detachably and sealingly connected to the air inlet port 114 via an air inlet line 315. Specifically, the two ends of the air inlet pipeline 315 may be respectively provided with joints to be respectively plugged with the air inlet 314 and the air inlet interface 114, so as to facilitate the disassembly and assembly.

Referring to fig. 3, the interior of the insulation 20 defines a second relief passage 214 that allows the air intake line 315 to pass therethrough. In such embodiments, the shielding gas or reactive gas can enter the sealed cavity 313 directly without being adsorbed by the insulation 20 or reacting with the insulation 20.

The gas in the sealed cavity 313 can be exhausted out of the high temperature furnace 10 through the gas outlet pipeline 311, or, when the gas content is low, the gas in the sealed cavity 313 can be remained in the sealed cavity 313 and can be exhausted outwards according to the requirement.

Referring to fig. 1, a control valve 113 may be disposed at the exhaust port 112 to control the conduction or the closure of the exhaust port 112. Control valves may be provided at least one of the intake interface 114, the exhaust interface 112, the vacuum port 115, and the intake port 314 to ensure relative sealing of the receiving chamber 110 and/or the sealing chamber 313 when intake or exhaust is not required. It is easy to understand that the air inlet line 315 and the air outlet line 311 can be provided as quick connectors to facilitate the connection with the corresponding interfaces.

The peripheral wall of the protective container 30 is provided with a wire adapter 312, and the electric heater 50 is electrically connected to the power supply interface 111 through the wire adapter 312. Specifically, the wire interface 51 may be directly plugged into one end of the wire adapter interface 312, or electrically connected to one end of the wire adapter interface 312 through the line 52, and the other end of the wire adapter interface 312 is electrically connected to the power supply interface 111 through the line 52.

In some embodiments of the present application, whether or not the protective container 30 is detachably installed in the high temperature furnace 10 may be determined according to actual needs of a user. For example, when the sample needs to be heated in a vacuum environment, the protective container 30 may not be provided in the high temperature furnace 10. The air inside the accommodating chamber 110 is pumped to the outside through the vacuum port 115, and the accommodating space of the inner furnace body 40 is also in a vacuum environment because the heat insulator 20 is not sealed or even has a porous structure.

When the sample needs to be heated under a protective atmosphere, a protective container 30 may be provided. Also, an inlet line 315 may be connected between the inlet port 114 and the inlet port 314, an outlet line 311 may be connected between the outlet port 112 and the outlet passage 310, and the protective atmosphere may enter the protective container 30 through the inlet port 114 and be discharged to the outside of the high temperature furnace 10 through the outlet port 112.

When the sample does not need to be heated under a protective atmosphere and the sample does not react with the heat insulator 20 after being heated or the components generated by heating do not have adverse effects on the heat insulator 20, the protective container 30 may not be disposed in the high temperature furnace 10. In this case, the heat insulator 20 without the first and

second relief passages

211 and 214 may be selectively installed in the receiving cavity 110.

Therefore, the protective container 30 which can be selectively installed by a user is arranged, so that the application embodiment further improves the use scene of the high-temperature furnace 10.

It will be readily appreciated that when the high temperature furnace 10 of the present embodiment includes a plurality of alternative insulation bodies 20, at least one of the insulation bodies 20 is structurally adapted to the protective vessel 30 such that the protective vessel 30 has the above-described functions of air intake and exhaust.

When the heat insulator 20 or the inner furnace body 40 is replaced, the pipeline or the circuit can be detached from the corresponding interface of the furnace body 11, and then the connecting rod 80 is separated from the support 70, so that the supporting plate 60 and the heat insulator 20 can be taken out from the furnace body 11. The insulation 20 and inner furnace body 40, etc. can then be reinstalled as needed.

It should also be noted that, in the case of the embodiments of the present invention, features of the embodiments and examples may be combined with each other to obtain a new embodiment without conflict.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and the scope of the present invention is subject to the scope of the claims.

Claims

1. A high temperature furnace, comprising:

a furnace body defining a receiving chamber having an opening formed thereon;

the inner furnace body is detachably arranged in the heat preservation cavity and is used for accommodating a sample to be heated; and

the electric heating body is detachably arranged in the heat preservation cavity and is used for heating the inner furnace body;

an exhaust interface is arranged on the furnace wall of the furnace body and used for exhausting the gas in the accommodating cavity to the outside;

the high temperature furnace further comprises: the protective container is detachably arranged in the heat preservation cavity, a sealed cavity is formed inside the protective container,

the protective container includes:

a container body defining a recess having an opening formed therein; and

the container cover body is covered on the container body and forms the sealed cavity together with the container body;

the inner furnace body and the electric heating body are both detachably arranged in the sealing cavity;

the container body is provided with an air outlet pipeline communicated with the sealing cavity, and the air outlet pipeline is detachably and hermetically connected with the exhaust interface.

2. The high temperature furnace of claim 1, wherein the insulation comprises:

the heat preservation body is limited to form a groove with an opening above; and

the heat preservation cover body covers the heat preservation body and is limited together with the groove of the heat preservation body to form the heat preservation cavity.

3. The high-temperature furnace according to claim 1, wherein the high-temperature furnace includes two or more heat retaining bodies, each of which is made of a different material;

one of the heat insulators is detachably mounted in the accommodating cavity.

4. The high-temperature furnace according to claim 1, wherein a power supply interface is arranged on the furnace wall of the furnace body;

the electric heating body is provided with an electric wire interface, and the electric wire interface of the electric heating body is electrically connected with the power supply interface through a line;

and the heat insulator is provided with a wire channel for the line to pass through.

5. A high-temperature furnace according to claim 4, wherein the furnace wall of the furnace body is provided with an air inlet interface for air to enter the accommodating cavity.

6. The high temperature furnace of claim 1,

and a first abdicating channel allowing the air outlet pipeline to pass through is formed in the heat insulator.

7. The high temperature furnace of claim 1, wherein the gas outlet line is disposed at a bottom of the vessel body.

8. The high-temperature furnace of claim 7, wherein the bottom of the container body is shrunk to form a funnel-shaped air outlet channel,

the air outlet pipeline is communicated with the air outlet channel.

9. The high-temperature furnace as claimed in claim 7, wherein the inner furnace body defines a receiving space with an opening at the upper part for receiving a sample to be heated,

the accommodating space is communicated with the sealing cavity.

10. The high-temperature furnace as claimed in claim 5, wherein the container body is provided with an air inlet which is detachably connected with the air inlet interface in a sealing way through an air inlet pipeline;

and a second abdicating channel allowing the air inlet pipeline to pass through is formed in the heat insulator.

11. The high-temperature furnace of claim 4, wherein the peripheral wall of the protective container is provided with a wire adapter, and the electric heating body is electrically connected with the power supply interface through the wire adapter.

12. The furnace of claim 10, wherein a control valve is provided at the exhaust port, the inlet port and/or the inlet port.

13. The high-temperature furnace according to claim 1, wherein the furnace body has a vacuum-pumping port in a wall thereof.

14. A high temperature furnace according to claim 1, wherein a gap is provided between a peripheral wall of the heat retaining body and the furnace cover.

15. The high temperature furnace of claim 1, further comprising: and the supporting part is used for supporting the heat insulator in the accommodating cavity.

16. The high temperature furnace of claim 15, wherein the support is a support plate disposed at a bottom of the heat retainer.

17. The high temperature furnace of claim 16, further comprising: the support is arranged on the bottom wall of the furnace body;

the support plate is removably mounted on the at least one support.

18. The high temperature furnace of claim 17, wherein the pedestal is made of a thermally insulating material.

19. The high temperature furnace of claim 18, further comprising: and the mounting part is used for detachably mounting the heat insulator and the supporting plate on the support.

20. The high temperature furnace of claim 19, wherein the mounting portion is a tie bar that extends through at least a portion of the insulation and the support plate, the tie bar having an upper end that is removably coupled to the insulation and a lower end that is removably coupled to the pedestal.

21. A high temperature furnace according to claim 1, wherein the furnace cover is rotatably attached to the furnace body.