The furnace bottom and furnace door of the coiling furnace and the coiling furnace

Abstract

This utility model relates to a furnace bottom door of a coiling furnace, comprising a base and a cover plate. The cover plate includes two spliced ​​cover plate segments, both of which are detachably mounted on the base and arranged sequentially along the length of the furnace bottom door. It also relates to a coiling furnace equipped with this furnace bottom door. In this utility model, the segmented design of the furnace bottom door cover plate effectively avoids excessive thermal expansion caused by an excessively large size of a single cover plate in one direction. The two cover plate segments can be independently disassembled and installed, allowing for replacement and maintenance tailored to their wear frequency, thus saving on furnace bottom door maintenance costs. Furthermore, the two cover plate segments can be designed with different specifications depending on their location, providing better heat insulation and sealing, and saving on the materials required for the furnace bottom door.

Description

Technical Field

[0001] This utility model belongs to the field of steel rolling technology, specifically relating to a furnace bottom door of a coiling furnace and a coiling furnace equipped with the furnace bottom door. Background Technology

[0002] A typical hot roll mill production line consists of one roughing mill and one coiling furnace at the front and rear of the mill. The coiling furnaces have openings at the bottom to facilitate the threading and coiling of the strip. To prevent high-temperature loss and overflow from the coiling furnace from damaging equipment such as the lower roller conveyor, and to guide the strip well into the coiling drum, an openable furnace door is usually installed at the bottom opening of the coiling furnace. This door serves both to insulate against high temperatures and to guide the strip.

[0003] During normal operation, the temperature inside the coiling furnace can reach 1050℃, making the high-temperature resistance of the furnace door particularly important. Currently, there are two main types of furnace door structures. One type uses a grid-like design at the top of the door, with high-temperature refractory material laid in the cavities of the grid. However, in actual use, the refractory material often detaches, affecting the surface quality of the strip. The other structure uses a thick steel plate at the top of the door to insulate against the high temperature, with a water trough at the bottom for cooling. However, this design is very complex, making maintenance and upkeep difficult. Furthermore, the high-frequency opening and closing of the furnace door, as well as the collisions and friction with the strip during threading, easily leads to cooling water leakage. Utility Model Content

[0004] This utility model relates to a furnace bottom and furnace door of a coiling furnace and a coiling furnace equipped with the furnace bottom and furnace door, which can at least solve some of the defects of the prior art.

[0005] This utility model relates to a furnace bottom and furnace door of a coiling furnace, including a base and a cover plate. The cover plate includes two cover plate segments that are spliced ​​together. Both cover plate segments are detachably mounted on the base, and the two cover plate segments are arranged sequentially along the length direction of the furnace bottom and furnace door.

[0006] As one implementation method, the two cover plate segments are a first cover plate segment and a second cover plate segment; the first cover plate segment is detachably fixed to the base, and the second cover plate segment is pressed onto the base by the first cover plate segment and the constraint structure on the base.

[0007] As one embodiment, the constraint structure includes a first pressure plate disposed on the base, and a first bearing plate matchedly disposed on the second cover plate section, wherein the first pressure plate presses against the top of the first bearing plate or near the upper surface of the first bearing plate.

[0008] As one embodiment, the first pressure plate is supported on the base by a first support plate, and the first pressure plate and the first support plate are connected to form an L-shaped plate; the first bearing plate is supported on the second cover plate section by a second support plate, and the first bearing plate and the second support plate are connected to form an L-shaped plate.

[0009] As one embodiment, a second pressure plate is provided at one end of the first cover plate segment near the second cover plate segment, and a second pressure plate is provided on the second cover plate segment in a matching manner. The second pressure plate presses against the upper surface of the second pressure plate or near the upper surface of the second pressure plate.

[0010] As one embodiment, the first cover plate segment and the base are respectively provided with socket holes. The insert plate passes through the socket holes on the first cover plate segment and the socket holes on the base in sequence and then protrudes from the base. The exposed plate body of the insert plate is provided with a pin hole and a pin is connected to it.

[0011] As one embodiment, the top of the insert plate is provided with a wing plate, and the socket on the first cover plate section is designed to be a stepped hole with a larger top and a smaller bottom, and the wing plate presses against the stepped surface of the socket.

[0012] As one embodiment, a plate holder is provided on the inner side plate surface of the first cover plate segment. The plate holder extends into the base, and the insertion hole on the first cover plate segment passes through the plate holder. The plate then passes through the first cover plate segment, the plate holder, and the base in sequence.

[0013] As one embodiment, a stop is provided on the base, and the stop abuts against the outer wall of the insert plate seat.

[0014] This utility model also relates to a coiling furnace, which is equipped with the furnace bottom and furnace door as described above.

[0015] This utility model has at least the following beneficial effects:

[0016] In this invention, the furnace bottom and furnace door cover plates are designed in sections, which can effectively avoid excessive thermal expansion caused by the excessive size of a single cover plate in one direction. The two cover plate sections can be disassembled and installed independently, so they can be replaced and maintained in a way that matches the wear frequency of the two cover plate sections, thereby saving the maintenance cost of the furnace bottom and furnace door. Moreover, the two cover plate sections can be designed with different specifications according to their location, which can better play the role of heat insulation and sealing, and save the materials required for the furnace bottom and furnace door. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the furnace door device provided in an embodiment of the present utility model;

[0019] Figure 2 A schematic diagram of the furnace door provided in an embodiment of this utility model;

[0020] Figure 3 A schematic diagram of the structure of the cover plate for the front furnace door provided in an embodiment of this utility model;

[0021] Figure 4 for Figure 3 Sectional view of AA;

[0022] Figure 5 This is a schematic diagram of the structure of the furnace bottom and furnace door provided in an embodiment of the present utility model;

[0023] Figure 6 This is a schematic diagram of the structure of the coiling furnace provided in an embodiment of the present utility model. Detailed Implementation

[0024] The technical solutions in the embodiments of this utility model are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0025] Example 1

[0026] like Figure 2 and Figure 5 This utility model embodiment provides a furnace door for a coiling furnace 4, including a bottom plate 102 and a cover plate 101. The cover plate 101 is supported on the bottom plate 102 by a support structure. The cover plate 101 and the bottom plate 102 are spaced apart and form a heat insulation cavity between them.

[0027] In one embodiment, such as Figure 2 The aforementioned support structure includes multiple stiffening ribs 103 disposed on the base plate 102, which effectively support the cover plate 101. Optionally, the multiple stiffening ribs 103 are arranged at intervals along the length of the furnace door, that is, the multiple stiffening ribs 103 are arranged at intervals along the threading direction.

[0028] The cover plate 101 needs to be fixedly connected to the base plate 102, or the cover plate 101 needs to be fixedly connected to the support structure. The fixed connection methods include, but are not limited to, welding, bolt connection, pin connection, etc., which will not be described in detail here.

[0029] Preferably, the cover plate 101 is made of heat-resistant steel plate, including but not limited to heat-resistant stainless steel plate, such as 309S / 310S heat-resistant stainless steel.

[0030] Preferably, the cover plate 101 has a relatively large thickness to ensure its heat resistance performance; in this embodiment, the thickness of the cover plate 101 is in the range of 25 to 45 mm, which can better balance the requirements of heat resistance performance and reducing the weight of the furnace door.

[0031] Among them, the heat resistance of the cover plate 101 itself and the heat insulation effect of the heat insulation cavity can effectively isolate the conduction of heat inside the furnace and protect the furnace bottom equipment.

[0032] The base plate 102 can also be made of heat-resistant steel plate, for example, the same material as the cover plate 101, or its heat resistance can be somewhat inferior to that of the cover plate 101. Optionally, the thickness of the base plate 102 is in the range of 25 to 45 mm.

[0033] Preferably, the cover plate 101 is arranged parallel to the bottom plate 102.

[0034] In one embodiment, the distance between the cover plate 101 and the base plate 102 is in the range of 130 to 150 mm, which can achieve a better heat insulation effect.

[0035] The aforementioned insulation cavity can be an open cavity, in which air from the surrounding environment circulates within it; or it can be a closed cavity, in which insulation gas is actively filled into it. When a closed cavity is used and insulation gas is continuously supplied into it, better insulation is achieved, and the cover plate 101 and bottom plate 102 can be cooled to a certain extent, thereby extending the service life of the furnace door, especially the cover plate 101.

[0036] When a closed cavity is used, a surrounding plate can be installed on the base plate 102. The surrounding plate can not only seal the heat-insulating cavity, but also reliably support the cover plate 101.

[0037] The insulating gas supplied to the sealed cavity can be room temperature air or air at a lower temperature than room temperature, or other gases such as argon.

[0038] The insulating gas can be supplied in a circulating manner. For example, an air inlet pipe and an air outlet pipe are provided on the furnace door. Both the air inlet pipe and the air outlet pipe are connected to the insulating cavity. The air outlet pipe is connected to the air inlet pipe through a circulation pipe. A circulation pump and a cooling mechanism can be installed on the circulation pipe. The cooling mechanism is used to cool the return gas to a set temperature before supplying it to the insulating cavity.

[0039] In optional embodiments, such as Figure 6 A purging mechanism 7 is provided at the inlet side of the coiling furnace 4 to clean the surface of the strip steel 5, thereby improving the cleanliness of the strip steel 5 and thus improving the quality of the strip steel 5 after coiling. The purging mechanism 7 includes an upper purging unit located above the strip steel running channel and / or a lower purging unit located below the strip steel running channel. The upper and lower purging units can be configured with multiple nozzles arranged on the purging beam. The heat insulation gas discharged from the heat insulation cavity can be used as the purging gas for the purging mechanism. That is, the exhaust pipe is connected to the air inlet of the upper / lower purging unit. Based on this method, on the one hand, the heat insulation gas can be utilized in stages; on the other hand, the heat insulation gas discharged from the heat insulation cavity is a high-temperature gas, which can preheat the strip steel 5 to a certain extent. Therefore, both of these aspects can achieve the effect of reducing energy consumption.

[0040] Example 2

[0041] like Figure 2 and Figure 5 This utility model embodiment provides a furnace door for a coiling furnace 4, including a base and a cover plate 101. The cover plate 101 is detachably installed on the base. Based on this method, the maintenance and replacement of the cover plate 101 can be facilitated to ensure the normal operation of the furnace door.

[0042] This embodiment can be used as an optimization of the first embodiment above. For example, the base plate 102 and the support structure in the first embodiment above can be configured as a base.

[0043] In one embodiment, such as Figure 2 and Figure 5 The cover plate 101 is detachably connected to the base via a pin 105 and a plate 104. Specifically, both the cover plate 101 and the base have socket holes. The plate 104 passes through the socket holes on the cover plate 101 and the base sequentially before protruding from the base. A pin hole is provided on the exposed portion of the plate 104, into which the pin 105 is engaged. This method allows for quick installation and removal of the cover plate 101.

[0044] The top of the insert plate 104 can be provided with a wing plate, which presses against the cover plate 101 and can effectively constrain the cover plate 101. The socket hole on the cover plate 101 can be designed as a stepped hole with a larger top and a smaller bottom. The wing plate presses against the stepped surface of the socket hole. This method can prevent the wing plate from being exposed on the surface of the cover plate 101 and interfering with the strip steel 5.

[0045] Optionally, such as Figure 2 , Figure 4 and Figure 5 A plate holder 1011 protrudes from the inner side of the cover plate 101, extending into the base. A socket hole on the cover plate 101 passes through the plate holder 1011. The plate 104 passes sequentially through the cover plate 101, the plate holder 1011, and the base. This improves the reliability of the connection between the plate 104 and the cover plate 101 and the base, thus enhancing the connection reliability between the cover plate 101 and the base. In a design where the base includes a bottom plate 102 and a supporting structure, when the plate holder 1011 extends to abut against the bottom plate 102, it further enhances the supporting effect of the bottom plate 102 on the cover plate 101.

[0046] Furthermore, such as Figure 2 A stop 106 is provided on the base, which abuts against the outer wall of the insert plate seat 1011 and can withstand part of the impact force on the cover plate 101 (mainly from the impact and friction between the strip steel 5 and the cover plate 101). In particular, in the strip threading direction, the stop 106 is located downstream of the insert plate seat 1011 (that is, the stop 106 and the furnace door material receiving end are located on the two sides of the insert plate seat 1011), which has a better effect in bearing the impact force of the cover plate 101.

[0047] In one embodiment, such as Figure 2 A first pressure plate 108 is provided on the base, and a first pressure plate 107 is provided on the cover plate 101. The first pressure plate 108 is located above the first pressure plate 107, that is, the first pressure plate 108 is located on the side of the first pressure plate 107 closer to the cover plate 101. The cooperation between the two can better limit and constrain the cover plate 101. Preferably, the surface of the first pressure plate 108 is parallel to the surface of the first pressure plate 107; otherwise, it is more preferably parallel to the surface of the cover plate 101. The distance between the first pressure plate 108 and the first pressure plate 107 is preferably controlled within 3mm, and a gap fit between the two is preferable, which can improve the constraint effect on the cover plate 101.

[0048] Furthermore, such as Figure 2 The first pressure plate 108 is supported on the base by the first support plate, and the first pressure plate 108 and the first support plate can be connected to form an L-shaped plate; the first bearing plate 107 is supported on the cover plate 101 by the second support plate, and the first bearing plate 107 and the second support plate can be connected to form an L-shaped plate.

[0049] When the base includes a base plate 102 and a supporting structure, the first pressure plate 108 can be set on the base plate 102, for example, the first support plate can be connected to the base plate 102; or the first pressure plate 108 can be set directly on the stiffening plate 103, which can save the production of the first support plate.

[0050] In the above structure, the cover plate 101 and the base are installed by a flat pushing method (for example, pushing the cover plate 101 flat on the base). After the flat pushing is in place, the first pressure plate 108 and the first bearing plate 107 are also in place. In addition, the cover plate 101 can also be positioned and installed by the cooperation of two sets of L-shaped plates, which improves the installation accuracy.

[0051] Furthermore, a stop 111 is provided on the cover plate 101 to guide the movement trajectory of the cover plate 101 during installation and to prevent the cover plate 101 from swinging significantly around the pin 105. Correspondingly, a guide unit that cooperates with the stop 111 can be provided on the base. Taking the base including the bottom plate 102 and multiple rows of stiffening plates 103 as an example, two or more rows of stop 111 can be provided. The spacing between two adjacent rows of stop 111 is adapted to the spacing between two adjacent rows of stiffening plates 103, so that the two rows of stop 111 contact or approach the two rows of stiffening plates 103 respectively. Through the interference cooperation between the two rows of stop 111 and the two rows of stiffening plates 103, the cover plate 101 can be guided and prevented from swinging.

[0052] In one embodiment, such as Figure 1 and Figure 3 The cover plate 101 is provided with lifting holes 112 to facilitate the installation and removal of the cover plate 101 by lifting. Optionally, the lifting holes 112 on the cover plate 101 are triangularly distributed.

[0053] In one embodiment, such as Figure 1 The cover plate 101 comprises multiple cover plate segments 1010, with a certain gap between adjacent cover plate segments 1010 to prevent structural damage due to thermal expansion. Optionally, the gap between adjacent cover plate segments 1010 is in the range of 25-30 mm. In this structure, each cover plate segment 1010 is mounted on a base, and therefore, each cover plate segment 1010 is detachably connected to the base via a set of pins 105 and insert plates 104. Each cover plate segment 1010 is provided with at least one first pressure plate 107, and each cover plate segment 1010 is provided with lifting holes 112, etc. Preferably, the cover plate segments 1010 are arranged sequentially along the width direction of the furnace door, that is, the arrangement direction of each cover plate segment 1010 is perpendicular to the threading direction.

[0054] Example 3

[0055] like Figure 1 and Figure 6 This utility model provides a furnace door device for a coiling furnace 4, including a front furnace door 1 and a rear furnace door 2. The front furnace door 1 is hinged to a fixed foundation. Along the threading direction, the rear furnace door 2 is located downstream of the front furnace door 1 and is hinged to it. The front furnace door 1 and the rear furnace door 2 are respectively equipped with a swing drive mechanism.

[0056] like Figure 6 When the front furnace door 1 and the rear furnace door 2 are in the strip-threading position, the strip steel 5 can be guided to the drum 6 by the cooperation of the front furnace door 1 and the rear furnace door 2; when the front furnace door 1 and the rear furnace door 2 are swung down, they can play a role in heat insulation.

[0057] Among them, the furnace door 1 with the front thread and / or the furnace door 2 with the rear thread can be the furnace doors provided in the above embodiment 1 / embodiment 2.

[0058] In one embodiment, such as Figures 2-4 Multiple transition blocks 110 are provided at the front end of the front furnace door 1 (that is, the end away from the rear furnace door 2). Each transition block 110 is arranged sequentially at intervals along the width direction of the front furnace door 1, that is, the arrangement direction of each transition block 110 is perpendicular to the strip threading direction. Multiple roller transition grooves are provided on the coiling furnace inlet roller 200. When the front furnace door 1 swings to the strip threading position, each transition block 110 is embedded into each roller transition groove in a corresponding manner. This method is conducive to the smooth operation of the strip 5 between the roller table and the front furnace door 1 during the strip threading process, thereby improving the reliability of strip threading.

[0059] The transition block 110 can be set on the cover plate of the front furnace door 1. Preferably, the transition block 110 is integrally formed with the cover plate of the front furnace door 1.

[0060] Preferably, such as Figure 3 The transition block 110 adopts a T-shaped structure that is smaller at the front and larger at the back. This significantly improves the bonding strength between the transition block 110 and the corresponding cover plate without affecting the fit between the transition block 110 and the roller transition groove. Optionally, such as... Figure 2 and Figure 4 The vertical cross-section of the end of the transition block 110 is triangular, which has a good cooperation effect with the inlet roller 200 and a good guiding effect on the strip 5.

[0061] In one embodiment, such as Figure 1 and Figure 2Multiple transition plates 109 are provided at the rear end of the front furnace door 1 (i.e., the end near the rear furnace door 2). The transition plates 109 are arranged sequentially at intervals along the width direction of the front furnace door 1. Multiple plate transition grooves 113 are provided at the front end of the rear furnace door 2. Each transition plate 109 and each plate transition groove 113 are arranged opposite to each other. When both the front furnace door 1 and the rear furnace door 2 are in the threading position, each transition plate 109 is embedded into each plate transition groove 113. When the front furnace door 1 and the rear furnace door 2 rotate relative to each other, the cooperation between each transition plate 109 and each plate transition groove 113 can ensure that there is no interference between the front furnace door 1 and the rear furnace door 2.

[0062] In one embodiment, such as Figure 1 and Figure 2 Multiple transition plates 109 are provided at the front end of the threaded furnace door 2 (that is, the end near the threaded furnace door 1), and the transition plates 109 are arranged sequentially at intervals along the width direction of the threaded furnace door 2. Multiple plate transition grooves 113 are provided at the rear end of the threaded furnace door 1, and each transition plate 109 and each plate transition groove 113 are arranged opposite to each other. When both the threaded furnace door 1 and the threaded furnace door 2 are in the threading position, each transition plate 109 is embedded into each plate transition groove 113. When the threaded furnace door 1 and the threaded furnace door 2 rotate relative to each other, the cooperation between each transition plate 109 and each plate transition groove 113 can ensure that there is no interference between the threaded furnace door 1 and the threaded furnace door 2.

[0063] Preferably, the transition plate 109 is a fan-shaped plate, the surface of which is parallel to the vertical and perpendicular to the surface of the corresponding cover plate. The fan-shaped plate can form a good transition as the strip 5 moves from the front furnace door 1 to the rear furnace door 2, avoiding collision between the strip 5 and the rear furnace door 2.

[0064] like Figure 1 and Figure 6 The aforementioned furnace door device also includes a furnace bottom door 3, wherein the furnace bottom door 3 is hinged to the fixed foundation, and along the belt threading direction, the furnace bottom door 3 is located downstream of the belt threading door 2, and the furnace bottom door 3 is equipped with a swing drive mechanism.

[0065] The furnace bottom door 3 mainly serves as heat insulation and does not require a guide strip 5. Alternatively, the furnace bottom door 3 can adopt the furnace door structure provided in Embodiment 1 / Embodiment 2 above.

[0066] Example 4

[0067] This utility model embodiment provides a furnace bottom and furnace door 3 for a coiling furnace 4, which can be applied to the above embodiment three.

[0068] The furnace bottom door 3 can adopt the furnace door structure provided in Embodiment 1 / Embodiment 2. Compared with the furnace door structure provided in Embodiment 1 / Embodiment 2, in this embodiment, the cover plate of the furnace bottom door 3 further includes two cover plate segments spliced ​​together. Both cover plate segments are set on the base, and the two cover plate segments are arranged sequentially along the length direction of the furnace bottom door 3.

[0069] The length direction of the furnace bottom door 3 is perpendicular to the axial direction of the coiling furnace 4. From another perspective, the two cover plate sections are arranged sequentially along the conveying direction of the roller conveyor below the furnace bottom door 3.

[0070] In the above scheme, by designing the cover plate 101 of the furnace bottom door 3 in segments along its length, it is possible to effectively avoid excessive thermal expansion caused by the excessive size of a single cover plate in one direction. The two cover plate segments can be disassembled and installed independently, so they can be replaced and maintained in a matched manner according to the wear frequency of the two cover plate segments, thereby saving maintenance costs of the furnace bottom door 3. Moreover, the two cover plate segments can be designed with different specifications according to their location, which can better play the role of heat insulation and sealing, and save the materials required for the furnace bottom door 3.

[0071] like Figure 1 and Figure 5 Both cover plate sections can adopt a segmented design structure that includes multiple cover plate segments 1010.

[0072] The two cover plate segments are defined as the first cover plate segment 302 and the second cover plate segment 301.

[0073] In one embodiment, such as Figure 5 The first cover plate section 302 is detachably fixed to the base, and the second cover plate section 301 is pressed onto the base by the first cover plate section 302 and the constraint structure on the base. This method can reduce the number of connecting parts between the cover plate 101 and the base, and can further improve the convenience and efficiency of maintenance of the furnace bottom and furnace door 3.

[0074] Preferably, the first cover plate segment 302 and the base can be detachably fixed together by means of a pin 105-insert plate 104 assembly; furthermore, a coupling structure of pressure plate-bearing plate can be coupled, as can be found in the relevant content of Embodiment 2.

[0075] For the second cover plate segment 301, it is fitted to the base through a pressure plate-bearing plate mating structure. Meanwhile, as... Figure 5A second pressure plate 303 is provided at one end of the first cover plate section 302 near the second cover plate section 301. A second pressure plate 304 is provided on the second cover plate section 301. The second pressure plate 303 is located on the side of the second pressure plate 304 away from the base (that is, on the side of the second pressure plate 304 near the furnace cavity). The second pressure plate 303 presses against the second pressure plate 304. In this way, the second cover plate section 301 can be reliably constrained to the base. The matching relationship between the second pressure plate 303 and the second pressure plate 304 can be referred to as the matching relationship between the first pressure plate 108 and the first pressure plate 107, which will not be described in detail here.

[0076] Example 5

[0077] like Figure 6 This utility model embodiment provides a coiling furnace 4, which is equipped with the furnace door device provided in the above embodiment 3. The specific structure of the furnace door device will not be described in detail here.

[0078] In the scheme where a purging mechanism 7 is provided on the inlet side of the coiling furnace 4, preferably, the heat insulation gas in the front furnace door 1, the rear furnace door 2, and the furnace bottom door 3 can be collected into a gas storage device 8 (including but not limited to a gas storage tank), and the gas storage device 8 is connected to the purging mechanism 7 through a gas supply pipe.

[0079] like Figure 6 The aforementioned purging mechanism 7 can be installed between the pinch roller 9 and the furnace door device.

[0080] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A furnace bottom furnace door of a coiling furnace, characterized by comprising: It includes a base and a cover plate. The cover plate includes two cover plate segments that are spliced ​​together. Both cover plate segments are detachably mounted on the base, and the two cover plate segments are arranged sequentially along the length direction of the furnace bottom and furnace door.

2. The hearth door of claim 1, wherein: The two cover plate segments are the first cover plate segment and the second cover plate segment; the first cover plate segment is detachably fixed to the base, and the second cover plate segment is pressed onto the base by the first cover plate segment and the constraint structure on the base.

3. The hearth door of claim 2, wherein: The constraint structure includes a first pressure plate disposed on the base, and a first bearing plate matchedly disposed on the second cover plate section, wherein the first pressure plate presses against the top of the first bearing plate or near the upper surface of the first bearing plate.

4. The hearth door of claim 3, wherein: The first pressure plate is supported on the base by the first support plate, and the first pressure plate and the first support plate are connected to form an L-shaped plate; the first bearing plate is supported on the second cover plate section by the second support plate, and the first bearing plate and the second support plate are connected to form an L-shaped plate.

5. The hearth door of claim 2, wherein: A second pressure plate is provided at one end of the first cover plate section near the second cover plate section, and a second pressure plate is provided on the second cover plate section in a matching manner. The second pressure plate presses against the upper surface of the second pressure plate or near the upper surface of the second pressure plate.

6. The hearth door of claim 2, wherein: The first cover plate segment and the base are detachably fixed together by a pin-plate assembly. The first cover plate segment and the base are respectively provided with socket holes. The plate passes through the socket holes on the first cover plate segment and the socket holes on the base in sequence and then protrudes from the base. The protruding plate body of the plate is provided with a pin hole and a pin is connected to it.

7. The hearth door of claim 6, wherein: The top of the insert plate is provided with a wing plate, and the socket on the first cover plate section is designed as a stepped hole with a larger top and a smaller bottom, and the wing plate presses against the stepped surface of the socket.

8. The hearth door of claim 6, wherein: An insert plate seat protrudes from the inner side of the first cover plate section. The insert plate seat extends into the base. The socket hole on the first cover plate section passes through the insert plate seat. The insert plate passes through the first cover plate section, the insert plate seat and the base in sequence.

9. The hearth door of claim 8, wherein: A stop is provided on the base, and the stop abuts against the outer wall of the insert plate seat.

10. A coiling furnace characterized by comprising: It is equipped with a furnace bottom and furnace door as described in any one of claims 1 to 9.

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