A method for treating a build-up on a furnace bottom roll

Abstract

The application discloses a kind of processing methods of furnace bottom roller nodulation, first type plate body is sent into the furnace roller way of heat treatment furnace, make first type plate body pass through the nodulation on furnace bottom roller, first type plate body is used to erase nodulation;Second type plate body is sent into the furnace roller way of heat treatment furnace, make second type plate body pass through the nodulation on furnace bottom roller, second type plate body is used to leave the indentation of nodulation, the position information of nodulation, height size, width size and erasing degree are determined by indentation.The processing method of furnace bottom roller nodulation provided by the application, the nodulation on furnace bottom roller is specifically rolled and erased by first type plate body of large thickness, the erasing degree is judged by forming indentation of nodulation on second type plate body of small thickness, and the elimination of nodulation on furnace bottom roller is realized by cooperation of first type plate body and second type plate body.

Description

Technical Field

[0001] This invention relates to Heat treatment furnace The field of technology relates, in particular to a method for treating nodules on the bottom rollers of a furnace. Background Technology

[0002] Roller hearth heat treatment furnaces are widely used in the steel plate heat treatment industry, capable of performing normalizing, quenching, and tempering heat treatment processes. Roller hearth heat treatment furnaces are characterized by uniform heating, good sealing, high output, low energy consumption, and a high degree of automation. However, in practical applications, roller hearth heat treatment furnaces are prone to indentation on the lower surface of the steel plate due to nodule buildup on the furnace bottom rollers. The indentation depth is generally between 0.15-0.5 mm, requiring grinding to remove the indentation. This grinding process is noisy, dusty, and involves harsh working conditions and high labor intensity. In some cases, the indentation depth can reach 1 mm. If the steel plate thickness is insufficient, this will directly lead to the steel plate exceeding the thickness tolerance and becoming unsaleable, resulting in significant losses. Summary of the Invention

[0003] In view of the above problems, the present invention is proposed to provide a method for treating furnace bottom roller nodules that overcomes or at least partially solves the above problems.

[0004] A method for treating nodules on furnace bottom rollers is provided, comprising:

[0005] The first type of plate is fed into the furnace roller conveyor of the heat treatment furnace, so that the first type of plate passes through the nodules on the furnace bottom roller. The first type of plate is used to wipe away the nodules.

[0006] The second type of plate is fed into the furnace roller conveyor of the heat treatment furnace, so that the second type of plate passes over the nodules on the furnace bottom roller. The second type of plate is used to leave indentations on the nodules. The location information, height dimension, width dimension and degree of removal of the nodules are determined by the indentations.

[0007] The temperature inside the heat treatment furnace is set to above 850℃, and the height ratio of the first type of plate to the second type of plate is 2 to 6:1.

[0008] Optionally, the position of the first type of plate on the furnace roller conveyor is determined based on the location information of the nodules; the width of the first type of plate is determined based on the width of the nodules.

[0009] Optionally, the location, height, width, and extent of erasure of the nodule can be determined by indentation, including:

[0010] The location of the nodules is determined based on the distance between the indentation and the center line of the second type of plate.

[0011] Determine the height of the nodule based on the depth of the indentation;

[0012] Determine the width of the nodule based on the width of the indentation;

[0013] The degree of nodule removal was determined based on the difference in indentation depth before and after nodule removal.

[0014] Optionally, the degree of nodule removal can be determined based on the difference in indentation depth before and after a nodule removal process, including:

[0015] Record the first depth value of the indentation on the second type of plate before one erasure of the nodule, and record the second depth value of the indentation on the second type of plate after one erasure of the nodule. The difference between the first depth value and the second depth value is directly proportional to the degree of nodule erasure.

[0016] Optionally, the thickness of the first type of plate is 120-160mm, and the thickness of the second type of plate is 30-50mm.

[0017] Optionally, the first type of plate and the second type of plate have a density of 7.8 g / cm³. 3 The above metal plates.

[0018] Optionally, the first type of plate is a steel plate, which is shot blasted to a quality grade of not less than SA2.5.

[0019] Optionally, the temperature inside the heat treatment furnace is set to 880–900℃; the rotation speed of the furnace bottom roller is 0.6–1 m / min; and the time for the first and second type plates to pass through the heat treatment furnace is more than 8 minutes.

[0020] Optionally, it also includes feeding multiple first-type plates and multiple second-type plates into the furnace roller conveyor of the heat treatment furnace at intervals until the depth of the indentation left by the Nth second-type plate is zero; where N is a positive integer greater than 2.

[0021] The technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0022] The method for treating furnace bottom roller nodules provided in this invention involves targeted rolling and wiping away the nodules on the furnace bottom roller using a thick first-type plate, and judging the degree of wiping by forming indentations on the nodules using a thinner second-type plate. The first and second types of plates work together to eliminate the nodules on the furnace bottom roller. Compared with the prior art, the technical solution provided in this invention does not have special requirements for furnace temperature. The first and second types of plates enter the heat treatment furnace sequentially along with the steel plates in production, without requiring a shutdown to remove the nodules, thus minimizing the impact on production. In addition, this invention can precisely roll and remove individual stubborn furnace bottom roller nodules that cannot be eliminated by dragging the furnace or washing the furnace. This method is simple to operate, highly efficient, reduces energy waste, and effectively improves the surface quality of the steel plate. It is particularly effective in the early stages of furnace bottom roller nodule development when the number of nodules is small.

[0023] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0025] Figure 1 This is a flowchart illustrating the process of treating nodules on the furnace bottom rollers in an embodiment of the present invention.

[0026] Figure 2 This is a scene illustration of an example of furnace bottom roller nodule treatment in an embodiment of the present invention;

[0027] Among them, 1 is the furnace pressure plate, 2 is the container plate, 3 is the exploration plate, 4 is the experimental plate, and 5 is the furnace bottom roller. Detailed Implementation

[0028] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings.

[0029] The accompanying drawings illustrate various structural schematics according to embodiments of the present invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

[0030] To better understand the above technical solutions, the following will describe the above technical solutions in detail with reference to specific implementation methods. It should be understood that the embodiments of this disclosure and the specific features in the embodiments are detailed descriptions of the technical solutions of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0031] This invention provides a method for treating nodules on the furnace bottom rollers. Please refer to [the relevant documentation]. Figure 1 , Figure 1 The flowchart of the furnace bottom roller nodule removal process in this embodiment of the invention includes: feeding a first type of plate into the furnace roller channel of the heat treatment furnace, so that the first type of plate passes through the nodules on the furnace bottom roller, and the first type of plate is used to wipe off the nodules;

[0032] The second type of plate is fed into the furnace roller conveyor of the heat treatment furnace, so that the second type of plate passes over the nodules on the furnace bottom roller. The second type of plate is used to leave indentations on the nodules. The location information, height dimension, width dimension and degree of removal of the nodules are determined by the indentations.

[0033] The temperature inside the heat treatment furnace is set to above 850℃, and the height ratio of the first type of plate to the second type of plate is 2 to 6:1.

[0034] Existing technologies mostly employ furnace washing or dragging methods to eliminate nodules on the furnace bottom rollers. Furnace washing requires adjusting the furnace temperature to 500℃, 800℃, or 900℃, and then repeatedly moving the washing plate inside the furnace at a speed of 20 meters per minute until the nodules on the furnace bottom rollers are crushed into thin sheets and adhered to the rollers. This method requires emptying the furnace of steel plates that are normally being used beforehand, which has a certain impact on production.

[0035] The furnace dragging method removes nodules from the furnace bottom rollers through mutual friction and impact between a specially processed dragging plate and the bottom rollers. This method requires specially processed dragging plates and requires the furnace temperature to be lowered to 500℃. The dragging process takes about 8 hours, and with the heating and cooling time, the total time is about 32 hours, which has a significant impact on production. This method is complex to operate and requires auxiliary equipment such as winches.

[0036] The technical solution of this invention uses a thick first-type plate to specifically roll and wipe away nodules on the furnace bottom roller. The degree of removal is judged by the indentation formed by a thinner second-type plate on the nodules. The first and second types of plates work together to eliminate nodules on the furnace bottom roller. Compared to existing technologies, the technical solution provided by this invention has no special requirements for furnace temperature. It only requires the heat treatment furnace to be turned on at its normal operating temperature. It does not require removing the steel plates currently being produced from the furnace. The first and second types of plates enter the heat treatment furnace sequentially along with the steel plates being produced, and no shutdown is required for nodule removal. Therefore, it has minimal impact on production.

[0037] Furthermore, the method of this invention can precisely roll away stubborn nodules on the furnace bottom rolls that cannot be eliminated by furnace dragging or washing. This method is simple to operate, highly efficient, reduces energy waste, and effectively improves the surface quality of the steel plate. It is particularly effective in the early stages of nodule development when the number of nodules is small.

[0038] In an optional implementation, the position of the first type of plate on the furnace roller conveyor is determined based on the location information of the nodules; the width of the first type of plate is determined based on the width of the nodules. The width of the first type of plate does not need to cover the entire furnace roller conveyor, but only the portion of the furnace bottom roller with nodules. Compared with the existing furnace dragging and washing methods, the method of the present invention can improve the accuracy of the nodule removal process on the furnace bottom roller, as it only crushes the nodule-covered portion, without damaging the surface of other nodule-free furnace bottom rollers. Furnace dragging and washing methods involve friction and crushing the entire surface of the furnace bottom roller, thus causing relatively less overall damage to the surface of the furnace bottom roller.

[0039] In an optional implementation, the location, height, width, and degree of erasure of the nodule are determined by indentation, including: determining the location of the nodule based on the distance between the indentation and the center line of the second type of plate; determining the height of the nodule based on the depth of the indentation; determining the width of the nodule based on the width of the indentation; and determining the degree of erasure of the nodule based on the difference in depth of the indentation before and after erasing the nodule.

[0040] In an optional implementation, the degree of nodule removal is determined based on the difference in indentation depth before and after a nodule removal process, including:

[0041] Record the first depth value of the indentation on the second type of plate before one erasure of the nodule, and record the second depth value of the indentation on the second type of plate after one erasure of the nodule. The difference between the first depth value and the second depth value is directly proportional to the degree of nodule erasure.

[0042] In an optional embodiment, the thickness of the first type of plate is 120–160 mm, and the thickness of the second type of plate is 30–50 mm. Compared with the second type of plate, the first type of plate has the advantage of thickness in crushing and eliminating nodules on the furnace bottom roller, while the second type of plate has the advantage of thinness, allowing for sufficient heating after entering the heat treatment furnace to collect nodule indentations, thereby determining the degree of nodule elimination.

[0043] In an optional embodiment, the first type of plate and the second type of plate have a density of 7.8 g / cm³. 3 The above refers to metal plates. Metal plates have a certain weight; thicker plates can be used for the first type of plate to crush and remove nodules; thinner plates can be used for collecting indentations to determine the degree of nodule removal.

[0044] In an optional implementation, the first type of plate is a steel plate, which is shot-blasted to a quality grade of not less than SA2.5. SA indicates the shot blasting or blasting rust removal grade, and the rust removal grade specification can be found in GB8923-88 "Rust and Rust Removal Grades of Steel Surfaces Before Painting". The SA grade can be divided into four levels: Sa1 is light sandblasting rust removal, requiring the surface to be free of visible dirt, grease, loosely adhered scale, paint coatings, rust, and impurities. Sa2 is thorough sandblasting rust removal, requiring the surface to be largely free of visible grease, dirt, scale, rust, paint coatings, and impurities, with any residue firmly adhered. Sa2.5 is very thorough sandblasting rust removal, requiring the surface to be free of visible grease, scale, dirt, paint coatings, and impurities, with any residue only showing slight streaks or spots. Sa3 grade involves sandblasting to remove rust until the steel surface is clean, requiring no visible grease, dirt, scale, rust, paint coatings, or impurities, and a uniform metallic luster. The first type of plate has a large thickness, absorbs heat slowly in the heat treatment furnace, and has high hardness. After the nodules on the furnace bottom rollers are removed by rolling and wiping, it undergoes another shot blasting treatment before being reused for the next rolling and wiping of nodules on the furnace bottom rollers.

[0045] In an optional embodiment, the temperature inside the heat treatment furnace is set to 880–900°C; the rotation speed of the furnace bottom roller is 0.6–1 m / min; and the time for the first and second type plates to pass through the heat treatment furnace is more than 8 minutes. The method of this invention does not have special temperature requirements; maintaining normal temperature and speed settings in the heat treatment furnace is sufficient to eliminate nodules on the furnace bottom roller, thus having minimal impact on production. Traditional furnace dragging has an impact of approximately 32 hours on production, and furnace washing has an impact of approximately 4–6 hours. The present invention's furnace pressing method occupies approximately 1 hour of production time.

[0046] In an optional embodiment, the process further includes feeding a plurality of first-type plates and a plurality of second-type plates into the furnace roller conveyor of the heat treatment furnace at intervals until the depth of the indentation left by the Nth second-type plate is zero; wherein N is a positive integer greater than 2. Typically, the first-type plates and the plurality of second-type plates are fed into the heat treatment furnace three times to completely eliminate the nodules on the furnace bottom rollers.

[0047] The following examples and... Figure 2 The implementation process steps of the embodiments of the present invention are described in detail.

[0048] Most steel mills use furnace washing or furnace dragging methods to remove nodules from the furnace bottom rollers. Furnace washing requires adjusting the furnace temperature to 500℃, 800℃, or 900℃, and then repeatedly moving a washing plate within the furnace at a speed of 20 meters per minute until the nodules on the bottom rollers are crushed into thin sheets and adhered to the rollers. This method requires emptying the furnace beforehand, which impacts production. Furnace dragging removes nodules from the bottom rollers through the mutual friction and impact between a specially processed dragging plate and the bottom rollers. This method requires specially processed dragging plates and lowering the furnace temperature to 500℃. The dragging process takes approximately 8 hours, and with the heating and cooling time, the total time is about 32 hours, significantly impacting production. This method is complex and requires auxiliary equipment such as winches.

[0049] Currently, the following patent applications in the existing technology mainly involve solutions to the problem of nodule formation on the bottom rollers of heat treatment furnaces:

[0050] CN102851477A discloses a method for reducing furnace bottom roller indentation defects on steel plate surfaces. This method controls nodule formation by controlling shot blasting, furnace atmosphere, production organization, and roller grinding. Nodules are eliminated through weekly roller grinding. However, roller grinding requires emptying the furnace of steel plates, which has some impact on production.

[0051] CN104896963B discloses a method for removing nodules from the bottom rollers of a heat treatment furnace. This method utilizes two temperature states—normalizing and tempering—and removes the nodules by mutual friction and impact between a specially processed steel plate with a fishbone-shaped lower surface and the bottom rollers. However, this method requires specially processed furnace support plates, resulting in high costs and requiring approximately 8 hours of furnace support, which is time-consuming and significantly impacts production efficiency.

[0052] CN102914174A discloses a method for preventing nodule formation on the bottom rollers of a heat treatment furnace. The method mainly involves opening the front and rear furnace doors at a high temperature of 800°C and repeatedly moving a thick-gauge furnace support plate inside the furnace to crush the nodules on the bottom rollers into thin sheets that adhere to the rollers. However, this method will lead to increasingly severe nodule formation as the iron oxide scale continues to increase, eventually resulting in failure.

[0053] CN101968320A discloses a method for removing nodules from the bottom rollers of a heat treatment furnace. The method removes the nodules by utilizing the friction between the furnace support plate and the bottom rollers at a temperature of 500°C. However, this method is complex to operate, requires auxiliary equipment such as winches, and has a high cost.

[0054] CN108118131A discloses a method for rapidly removing nodules from the bottom rollers of a heat treatment furnace at high temperatures. This method involves a reciprocating motion of a steel plate from the middle to the outlet of the furnace. During this motion, the steel plate crushes and rubs against the nodules on the bottom rollers, causing them to fall off. The method also involves placing the head of the steel plate against a stop device on the outlet roller conveyor of the furnace, while simultaneously loading the remaining steel plates into the furnace rapidly, with the head of each plate pressing against the tail of the previous plate. This method requires all steel plates to be removed from the furnace before these operations can be performed, which can impact production.

[0055] To achieve the technical solution of this invention, the first type of plate is functionally named a furnace pressure plate, and the second type of plate is named a exploratory plate or experimental plate. For example... Figure 2 As shown, Figure 2 This is a scenario diagram illustrating the treatment of furnace bottom roller nodules in an embodiment of the present invention. Using the technical solution of the present invention, under normal production conditions, the furnace bottom roller nodules are crushed and eliminated by the weight of the furnace pressure plate itself, in conjunction with corresponding furnace pressure operation steps. Specifically, the process includes the following steps:

[0056] (1) Prepare 1 furnace press plate in advance. The furnace press plate is 120mm thick, 800mm wide, and 8m long. It is made of ordinary carbon steel and there are 3 pieces in total.

[0057] (2) When the 345R container plate 2 is produced in batches and normalized, the steel plate specifications are 38*3720*9160, the heat treatment normalization temperature of 345R container plate 2 is 880℃, the holding time is 10 minutes, and after two days of continuous production, furnace bottom roller marks appear.

[0058] (3) Select a 345R steel plate that has been shot blasted and is ready for production as the test plate 3. First, check the quality of the lower surface of the steel plate to confirm that there are no quality problems such as indentations or scratches, so as to avoid confusion with the indentations of the furnace bottom roller 5.

[0059] (4) Place the exploration plate 3 on the furnace roller conveyor and center it at the centering device before entering the furnace. The center line of the exploration plate 3 coincides with the center line of the heat treatment furnace roller conveyor.

[0060] (5) The exploration plate 3 is put into the furnace normally and the production is carried out normally according to the process requirements. The heating temperature is set to 880℃, the furnace time is executed according to the system time, the heat preservation time is 10 minutes, and the furnace is cooled to room temperature after being taken out of the furnace.

[0061] (6) Hoist the test plate 3 to the inspection stand and inspect the indentation on the lower surface. Determine that the distance between the indentation and the center line of the width of the test plate 3 is 1128mm. The indentation is usually circular or elliptical. The measured diameter of the indentation here is 20mm, indicating that the width of the indentation is 20cm; the depth is 0.25mm, indicating that the height of the nodule reaches 0.15mm; the spacing is 1.19m, indicating that the distance between the indentations reaches 1.19m.

[0062] (7) Based on the distance of 1128mm between the indentation and the center line of the steel plate width, the distance of the nodule position of the furnace bottom roller 5 from the center line of the furnace bottom roller 5 is calculated to be 1128mm.

[0063] (8) Adjust the position of the press plate on the furnace feed roller. The distance between the center line of the press plate and the center line of the furnace bottom roller 5 is 1128mm. The width of the press plate can cover the nodule area of ​​the furnace bottom roller 5.

[0064] (9) The thickness of the furnace plate is set to be above 120mm, the width is set to 800mm, and the length is set to 8m; it is put into the furnace normally after the steel plate produced, with a spacing of 1 meter;

[0065] (10) Follow the press plate with another normal production plate as test plate 4. Before entering the furnace, check the quality of the lower surface of test plate 4 to confirm that there are no quality problems such as indentations or scratches, so as to avoid confusion with the indentations of the furnace bottom roller 5.

[0066] (11) After the experimental plate 4 was cooled after being taken out of the furnace, it was hoisted to the inspection stand and the lower surface was inspected. It was found that the indentation was 0.13, which showed that the indentation was becoming shallower and the nodules on the furnace bottom roller 5 were showing an improvement trend. Steps (7), (8), and (9) were repeated, and it was found that the indentation on the second experimental plate was 0.02, which showed that the indentation was becoming shallower again. Steps (7), (8), and (9) were repeated again, and it was found that there were no indentations on the third experimental plate, which proved that the nodules on the furnace bottom roller 5 were completely eliminated.

[0067] like Figure 2 As shown, the 345R container plate 2 can be sandwiched between the press plate 1, the exploration plate 3, and the experimental plate 4. Normal production can proceed without stopping production to remove nodules, thus having a minimal impact on production.

[0068] The technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0069] The method for treating furnace bottom roller nodules provided in this invention involves targeted rolling and wiping away the nodules on the furnace bottom roller using a thick first-type plate, and judging the degree of wiping by forming indentations on the nodules using a thinner second-type plate. The first and second types of plates work together to eliminate the nodules on the furnace bottom roller. Compared with the prior art, the technical solution provided in this invention does not have special requirements for furnace temperature. The first and second types of plates enter the heat treatment furnace sequentially along with the steel plates in production, without requiring a shutdown to remove the nodules, thus minimizing the impact on production. In addition, this invention can precisely roll and remove individual stubborn furnace bottom roller nodules that cannot be eliminated by dragging the furnace or washing the furnace. This method is simple to operate, highly efficient, reduces energy waste, and effectively improves the surface quality of the steel plate. It is particularly effective in the early stages of furnace bottom roller nodule development when the number of nodules is small.

[0070] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0071] Similarly, it should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof. However, this method of disclosure should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into this detailed description, wherein each claim itself is a separate embodiment of the invention.

[0072] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. The invention can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In the unit claims enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

Claims

1. A method of treating a build-up on a furnace bottom roll, characterized by, The method comprises: sending a first type of plate body into a furnace roller of a heat treatment furnace, so that the first type of plate body passes through a nub on a furnace bottom roller, and the first type of plate body is used to erase the nub; sending a second type of plate body into the furnace roller of the heat treatment furnace, so that the second type of plate body passes through the nub on the furnace bottom roller, and the second type of plate body is used to leave a mark of the nub, and the position information, height size, width size and erasing degree of the nub are determined through the mark; The temperature in the heat treatment furnace is set to be above 850℃, the rotating speed of the furnace bottom roller is 0.6-1 m / min, the first type of plate body and the second type of plate body pass through the heat treatment furnace for more than 8 minutes, the thickness of the first type of plate body is 120-160 mm, the thickness of the second type of plate body is 30-50 mm, the first type of plate body and the second type of plate body are made of metal with a density of 7.8 g / cm 3 The above metal plate; determining the position of the first type of plate body on the furnace roller according to the position information of the nub; determining the width of the first type of plate body according to the width size of the nub.

2. The method of claim 1 wherein the step of applying the coating is performed after the step of applying the first layer of the coating. The method further comprises: determining the position information of the nub according to the distance between the mark and the center line of the second type of plate body; determining the height size of the nub according to the depth of the mark; determining the width size of the nub according to the width of the mark; determining the erasing degree of the nub according to the depth difference of the mark before and after erasing the nub once.

3. The method of claim 2, wherein the step of applying the coating is performed after the step of applying the first layer of the coating. The method further comprises: recording a first depth value of the mark on the second type of plate body before erasing the nub once, recording a second depth value of the mark on the second type of plate body after erasing the nub once, and the difference between the first depth value and the second depth value is in a proportional relationship with the erasing degree of the nub.

4. The method of claim 1 wherein the step of applying the coating is performed after the step of applying the first layer of the coating. The first type of plate body is a steel plate, and the steel plate is subjected to a shot blasting treatment, and the shot blasting quality grade is not less than SA2.5 grade.

5. The method of claim 1 wherein the step of applying the coating composition to the surface of the furnace bottom roll is performed by a process selected from the group consisting of spraying, dipping, and combinations thereof. The temperature in the heat treatment furnace is set to 880-900 ℃.

6. The method of claim 1 wherein the step of applying the coating composition to the surface of the furnace bottom roll is performed by a process selected from the group consisting of spraying, dipping, and combinations thereof. The method further comprises: sending a plurality of first type of plate bodies and a plurality of second type of plate bodies into the furnace roller of the heat treatment furnace at intervals until the depth of the mark left by the Nth second type of plate body is zero; wherein N is a positive integer greater than or equal to 2.

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