KR102179303B1 - Scale removing apparatus and method for low chromium ferritic stainless steel hot-rolled steel sheet - Google Patents

Abstract

In the present specification, an apparatus and method for removing scale of a low chromium ferritic stainless hot-rolled steel sheet that can be applied to an automobile exhaust system are disclosed.
According to an exemplary embodiment, the disclosed scale removal apparatus includes a brush containing a hydrochloric acid bath and silicon carbide (SiC) abrasive particles, and satisfies the following equations (1) and (2).
(1) (1.04 + 0.000801*N + 0.00492*T + 0.00451*C) <1.5
(2) (-59 + 0.0243*N + 0.341*T + 4.29*C) <50
(Here, N: mesh number of the silicon carbide abrasive particles, T: immersion time (seconds) of the steel sheet immersed in the hydrochloric acid bath, C: refers to the hydrochloric acid concentration (wt%) of the hydrochloric acid bath).

Description

Scale removing apparatus and method for low chromium ferritic stainless steel hot-rolled steel sheet {Scale removing apparatus and method for low chromium ferritic stainless steel hot-rolled steel sheet}

The present invention relates to a scale removal apparatus and a method for removing scale generated during manufacture of a low-chromium ferritic stainless steel hot-rolled steel sheet.

Low chromium 409L ferritic stainless steel with a chromium content of 11% in steel is mainly used for automobile exhaust systems. In general, the annealing scale of the low-chromium ferritic stainless steel as described above contains chromium, so that the structure of the scale is very dense, and the scale is very difficult to remove due to good corrosion resistance.

Accordingly, the method of removing hot-rolled annealing scale of low-chromium ferritic stainless steel includes a step of firstly removing scale by a mechanical method such as a scale breaker, shot blasting, and a rough polishing brush, and a high temperature and high concentration sulfuric acid deposition step and nitric acid. It consisted of a very complex pickling process with a mixed acid deposition step consisting of hydrofluoric acid.

When nitric acid is used for the pickling process, there is a problem of increasing environmental pollution because NOx gas is generated during the pickling process and nitrogen is discharged from the waste acid discarded after pickling. Therefore, a DeNOx device for removing NOx gas during the pickling process and a denitrification device for removing nitrogen from waste acid are indispensable, and the treatment cost is high, and there is a problem that productivity is lowered because it usually takes several minutes or more for pickling time.

In addition, in the process of removing scale by mechanical methods such as shot blasting and rough polishing brush, there is a problem that the roughened surface affects even after cold rolling, so that the surface is not beautiful.

Korean Patent Registration Publication No. 1996-0004787 (announced on April 13, 1996)

In order to solve the above problems, the present invention can improve economic efficiency by simplifying a complex scale removal process, and is eco-friendly because there is no emission of pollutants such as wastewater containing NOx gas and nitrogen, and a low chromium ferritic system with improved surface quality. An object of the present invention is to provide a scale removal apparatus and a method for manufacturing a stainless hot rolled steel sheet.

The scale removal apparatus of a low-chromium ferritic stainless steel hot-rolled steel sheet according to an embodiment of the present invention includes a brush containing hydrochloric acid bath and silicon carbide (SiC) abrasive particles, and satisfies the following equations (1) and (2). do.

(1) (1.04 + 0.000801*N + 0.00492*T + 0.00451*C) <1.5

(2) (-59 + 0.0243*N + 0.341*T + 4.29*C) <50

(Here, N: mesh number of the silicon carbide abrasive particles, T: immersion time (seconds) of the steel sheet immersed in the hydrochloric acid bath, C: refers to the hydrochloric acid concentration (wt%) of the hydrochloric acid bath).

In addition, it may further include a scale breaker generating cracks on the scale surface.

In addition, the hydrochloric acid concentration (C) of the hydrochloric acid tank may be 18 to 21%, and the immersion time (T) may be 15 to 60 seconds.

In addition, the mesh number (N) may be 80 to 240.

A method of removing scale of a low-chromium ferritic stainless steel hot-rolled steel sheet according to another embodiment of the present invention includes the steps of immersing a low-chromium ferritic stainless steel hot-rolled steel sheet in a hydrochloric acid bath to perform pickling treatment, and the scale remaining on the surface of the steel sheet and the pickling treatment. The reactant formed later includes the step of removing using a brush containing silicon carbide (SiC) abrasive particles, and the following equations (1) and (2) are satisfied.

(1) (1.04 + 0.000801*N + 0.00492*T + 0.00451*C) <1.5

(2) (-59 + 0.0243*N + 0.341*T + 4.29*C) <50

(Here, N: mesh number of the silicon carbide abrasive particles, T: immersion time (seconds) of the steel sheet immersed in the hydrochloric acid bath, C: refers to the hydrochloric acid concentration (wt%) of the hydrochloric acid bath).

In addition, before immersing the steel sheet in the hydrochloric acid bath, the step of generating a crack on the scale surface using a scale breaker may be further included.

In addition, the hydrochloric acid concentration (C) of the hydrochloric acid tank may be 18 to 21%, and the immersion time (T) may be 15 to 60 seconds.

In addition, the mesh number (N) may be 80 to 240.

The scale removal apparatus and method for a low chromium ferritic stainless steel hot-rolled steel sheet according to the present invention are directly immersed in a hydrochloric acid bath for pickling treatment, so that the complex pickling process that goes through the sulfuric acid deposition step and the mixed acid deposition step can be simplified to reduce cost. have.

In addition, compared to the conventional stainless steel pickling process, it is eco-friendly because it does not emit pollutants such as NOx in that it does not use nitric acid because it does not use nitric acid.

In addition, the mechanical pickling process is simplified, and a stainless steel sheet having excellent surface quality can be provided even after cold rolling.

1 is a schematic diagram of a scale removal apparatus for a low-chromium ferritic stainless hot-rolled steel sheet according to the present invention.
2 is a photograph taken with an optical microscope of 100 times the stainless steel sheet of the present invention after cold rolling.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention may be modified into various other forms, and the technical idea of the present invention is not limited to the embodiments described below. In addition, embodiments of the present invention are provided in order to more completely explain the present invention to those with average knowledge in the art.

The terms used in the present application are only used to describe specific examples. So, for example, a singular expression includes a plural expression unless the context clearly has to be singular. In addition, terms such as "include" or "include" used in the present application are used to clearly refer to the existence of features, steps, functions, components or combinations thereof described in the specification, but other features It should be noted that it is not used to preliminarily exclude the presence of elements, steps, functions, components, or combinations thereof.

Meanwhile, unless otherwise defined, all terms used in this specification should be viewed as having the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Therefore, unless clearly defined in the specification, specific terms should not be interpreted in an excessively ideal or formal sense. For example, in the present specification, expressions in the singular include plural expressions unless the context clearly has exceptions.

In addition, "about", "substantially" and the like in the present specification are used at or close to the numerical value when manufacturing and material tolerances specific to the stated meaning are presented, and are accurate to aid understanding of the present invention. Or absolute figures are used to prevent unfair use of the stated disclosure by unconscionable infringers.

In addition, the "low chromium ferritic stainless steel hot-rolled steel sheet" of the present specification refers to a stainless steel hot-rolled steel sheet obtained by hot rolling a low chromium-containing ferritic stainless steel of 14% by weight or less, which is not annealed after hot rolling.

Low chromium 409L ferritic stainless steel with a chromium content of 11% in steel is mainly used for automobile exhaust systems. In general, the annealing scale of the low-chromium ferritic stainless steel as described above contains chromium, so that the structure of the scale is very dense, and the scale is very difficult to remove due to good corrosion resistance.

Accordingly, the method of removing hot-rolled annealing scale of low-chromium ferritic stainless steel includes a step of firstly removing scale by a mechanical method such as a scale breaker, shot blasting, and a rough polishing brush, and a high temperature and high concentration sulfuric acid deposition step and nitric acid. It consisted of a very complex pickling process with a mixed acid deposition step consisting of hydrofluoric acid.

When nitric acid is used for the pickling process, there is a problem of increasing environmental pollution because NOx gas is generated during the pickling process and nitrogen is discharged from the waste acid discarded after pickling. Therefore, a DeNOx device for removing NOx gas during the pickling process and a denitrification device for removing nitrogen from waste acid are indispensable, and the treatment cost is high, and there is a problem that productivity is lowered because it usually takes several minutes or more for pickling time.

In addition, in the process of removing scale by mechanical methods such as shot blasting and rough polishing brush, there is a problem that the roughened surface affects even after cold rolling, so that the surface is not beautiful.

Therefore, in order to solve the above-described problem, the present invention can improve economic efficiency by simplifying the complex scale removal process, and is eco-friendly because there is no emission of pollutants such as wastewater containing NOx gas and nitrogen, and low chromium ferrite with improved surface quality. An object of the present invention is to provide a scale removal apparatus and a method for manufacturing a stainless steel hot-rolled steel sheet.

The scale removal device of the present invention relates to a scale removal device of a low chromium ferritic stainless steel hot-rolled steel sheet, and the scale removal device according to an embodiment of the present invention includes a brush containing hydrochloric acid bath and silicon carbide (SiC) abrasive particles. do. Hereinafter, the low-chromium ferritic stainless steel hot-rolled steel sheet may be abbreviated as a stainless steel sheet for convenience.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, in the drawings, in order to clarify the present invention, portions not related to the description may be omitted, and sizes of components may be slightly exaggerated to help understanding.

1 is a schematic diagram of a scale removal apparatus of the present invention. The present invention will be described in detail with reference to FIG. 1, but FIG. 1 is an example of the present invention, and the present invention is not limited thereto.

Referring to FIG. 1, the scale removal apparatus of the present invention includes an immersion hydrochloric acid bath 3 for removing scale by depositing a stainless steel sheet 1 and pickling treatment, and the steel sheet transferred from the hydrochloric acid bath 3 (1) A brush (4) for removing scale remaining on the surface of and reactants formed after the pickling treatment, a washing device 5 for washing the brushed steel sheet 1, and a drying device for drying after washing with water It includes (6).

In addition, it may further include a scale breaker 2 capable of generating cracks on the scale surface before the steel plate 1 is immersed in the hydrochloric acid bath 3. Cracks on the surface of the scale formed by the scale breaker 2 facilitate acid penetration into the interface between the scale and the base material in the immersion process in the hydrochloric acid bath 3, so that the scale can be effectively removed. In addition, the scale breaker 2 can make the shape of the stainless steel plate 1 flat.

The hydrochloric acid tank 3 of the present invention is a mechanism for removing scale of Cr and Fe components formed on the surface of a stainless steel sheet. In the hydrochloric acid tank 3 of the present invention, the stainless steel plate 1 is immersed in the hydrochloric acid tank 3 containing the hydrochloric acid solution without going through the high concentration sulfuric acid deposition step and the mixed acid deposition step consisting of nitric acid and hydrofluoric acid to remove scale. Since the conventional complicated pickling process is simplified, cost is reduced.

In order to efficiently remove the scale formed on the steel plate 1, the higher the concentration and the immersion time of the hydrochloric acid solution contained in the hydrochloric acid tank 3, the better. However, if the concentration and immersion time exceed a certain level, the base material may be dissolved after the scale is removed, and excessive surface reactants may be formed on the dissolved base material, so that foreign substances to be removed from the brush 4 may become excessive. Not desirable. Therefore, for proper pickling, the concentration and immersion time of the hydrochloric acid solution must be limited. As an example of the present invention, the hydrochloric acid concentration in the hydrochloric acid tank 3 may be 18 to 21%, and the immersion time may be 15 to 60 seconds.

The pickled steel sheet 1 is transferred from the hydrochloric acid tank 3 to the brush 4, and in the brush 4, the scale remaining on the surface of the transferred steel sheet 1 and the reactants formed after the pickling treatment are mechanically removed from the surface. Separate and remove.

The brush hair constituting the brush 4 can be implemented with a material containing silicon carbide (SiC) abrasive particles rather than a conventional nylon material, and the SiC abrasive particles can be used up to mesh numbers #80 to #1200 in consideration of roughness. . If the mesh number of the SiC abrasive particles is less than #80, the surface quality of the steel sheet 1 may be rather deteriorated, and if it exceeds #240, there is little polishing ability, and thus residual scale and side reactants may exist. Therefore, the mesh number of the SiC abrasive particles constituting the brush bristle in the present invention is preferably controlled in the range of #80 to #240.

In addition, the scale removal device of the present invention includes a washing device 5 for washing the stainless steel sheet 1 passing through the brush 4 and a drying device for drying the stainless steel sheet 1 passing through the washing device 5 ( 6).

Since the surface quality of the hot-rolled steel sheet affects the surface quality of the final cold-rolled steel sheet afterwards, it is important to manage the surface quality of the hot-rolled steel sheet. The surface quality of the stainless steel hot-rolled steel sheet is determined by the hydrochloric acid concentration and immersion time of the hydrochloric acid bath and the size (mesh number) of the SiC abrasive grains of the brush, and the following shows the condition of surface roughness (Ra, ㎛) after pickling and brush treatment. It is secured when the condition of Equation (1) and the following Equation (2) indicating the condition of the area ratio (%) where the surface is not polished by the brush is satisfied.

(1) (1.04 + 0.000801*N + 0.00492*T + 0.00451*C) <1.5

(2) (-59 + 0.0243*N + 0.341*T + 4.29*C) <50

Here, N: mesh number of the silicon carbide abrasive particles, T: immersion time (seconds) of the steel sheet immersed in the hydrochloric acid bath, C: refers to the hydrochloric acid concentration (weight %) of the hydrochloric acid bath. In addition, in Equations (1) and (2), the surface roughness after the above-described pickling and brush treatment and the area ratio of the surface not polished by the brush can be expressed by the following Equations (3) and (4), respectively.

(3) Surface roughness (Ra, ㎛) = (1.04 + 0.000801*N + 0.00492*T + 0.00451*C)

(4) Area ratio (%) = (-59 + 0.0243*N + 0.341*T + 4.29*C)

Therefore, in order to improve the surface quality of the hot-rolled steel sheet, scale is removed by appropriately controlling the mesh number (N), immersion time (T), and hydrochloric acid concentration (C) to satisfy the above equations (1) and (2). It is desirable to do.

The scale removal method using the scale removal device of the stainless steel sheet according to the disclosed embodiment includes the steps of immersing a stainless steel sheet that is hot-rolled and not subjected to hot rolling annealing in a hydrochloric acid bath to be pickled, and after the scale remaining on the surface of the steel sheet and pickling treatment. It may include removing the formed reactant using a brush, washing the steel sheet passing through the brush, and drying after washing with water.

In addition, for effective removal of scale and flatness of the stainless steel sheet, the step of generating a crack on the scale surface of the steel sheet using a scale breaker before immersing the steel sheet in a hydrochloric acid bath may be further included.

In addition, the scale removal method of the present invention can remove the scale in various ways with reference to the contents described with reference to FIG. 1, and a description of overlapping contents will be omitted. In addition, it is preferable to satisfy Equations (1) and (2) for surface quality as described above. Equations (1) and (2) are omitted since they have been described above.

The present invention will be described in more detail through the following examples. However, the following examples are intended to illustrate the present invention in more detail, and the technical idea of the present invention is not limited to the following examples.

{Example}

In each of the following inventive examples and comparative examples, the surface roughness according to the hydrochloric acid concentration and the immersion time, the mesh number of the silicon carbide abrasive particles of the brush and the area ratio of the surface not polished by the brush were measured at a hydrochloric acid bath temperature of 80°C. Hereinafter, the mesh number of the silicon carbide abrasive particles of the brush is abbreviated as a mesh number for convenience.

The surface roughness was measured Ra value (㎛) by using a roughness meter at the time of contact. Hereinafter, it is abbreviated as illuminance for convenience.

The area ratio (%) where the surface was not polished by the brush was measured through an image analysis method after photographing 100 times with an optical microscope. Hereinafter, the area ratio (%) where the surface is not polished by the brush is abbreviated as an area ratio for convenience.

Determination of good/defective surface quality after pickling was determined according to the presence or absence of defects caused by areas where the surface was not polished by the brush after the final cold rolling. When a defect did not occur, it was indicated as good (○), and when a defect occurred, it was indicated as defective (X). 2 shows defects generated in the stainless steel sheet after cold rolling, and is a photograph taken with an optical microscope 100 times.

Table 1 below is a table showing the results measured through an experiment at a hydrochloric acid temperature of 80°C, a mesh number of #80 to #1200, an immersion time of 15 to 60 seconds, and a hydrochloric acid concentration of 18 to 24% by weight under the conditions described above.

Mesh
number deposition
time
(second) Hydrochloric acid
density
(%) Illuminance
(Ra,㎛) Area ratio
(%) Good
/
Bad Invention Example 1 240 30 18 1.48 38 O Comparative Example 1 240 45 18 1.53 40 X Comparative Example 2 240 60 18 1.62 45 X Invention Example 2 240 30 21 1.47 48 O Comparative Example 3 240 45 21 1.58 51 x Comparative Example 4 240 60 21 1.72 53 x Invention Example 3 100 30 18 1.38 30 O Invention Example 4 100 45 18 1.41 33 O Inventive Example 5 100 60 18 1.48 41 O Inventive Example 6 100 30 21 1.33 43 O Invention Example 7 100 45 21 1.49 45 O Comparative Example 5 100 60 21 1.48 56 x Invention Example 8 80 15 18 1.28 24 O Inventive Example 9 80 30 18 1.31 28 O Inventive Example 10 80 45 18 1.39 35 O Invention Example 11 80 60 18 1.48 42 O Inventive Example 12 80 45 21 1.42 46 O Comparative Example 6 80 60 21 1.47 54 x Comparative Example 7 400 30 18 1.73 47 x Comparative Example 8 400 30 21 1.75 61 x Comparative Example 9 800 60 18 2.05 57 x Comparative Example 10 800 60 21 2.12 68 x Comparative Example 11 1200 30 21 2.25 65 x Comparative Example 12 1200 45 21 2.31 78 x Comparative Example 13 1200 60 21 2.35 82 x Comparative Example 14 1200 60 18 2.42 69 x Comparative Example 15 80 60 24 1.52 64 x Comparative Example 16 100 45 24 1.44 62 x Comparative Example 17 240 30 24 1.49 59 x

With reference to Table 1, the measurement results of each invention example and comparative example were compared and evaluated.

Referring to Table 1 regarding the immersion time (T, sec), it can be seen that the longer the immersion time, the higher the values of the roughness (Ra, ㎛) and area ratio (%).

Comparing Inventive Example 1 and Comparative Example 1,2, as the immersion time increases, the area ratio is 50% or less, but the value of the surface roughness exceeds 1.5 µm, so that the steel sheet of Comparative Example 1,2 has rolling defects during the final cold rolling. Has occurred.

In addition, when comparing Inventive Example 2 and Comparative Examples 3 and 4, which are the results of higher hydrochloric acid concentration (21% by weight), the area ratio exceeded 50% and the surface roughness value exceeded 1.5 μm as the immersion time increased. . During the final cold rolling, rolling defects occurred in the steel sheets of Comparative Examples 3 and 4.

Comparing Inventive Example 12 and Comparative Example 6, as the immersion time increased, the surface roughness value was less than 1.5 µm, but the area ratio exceeded 50%, and thus rolling defects occurred in the steel sheet of Comparative Example 6 during final cold rolling.

Referring to Table 1 with respect to the hydrochloric acid concentration (C, wt%), it can be seen that as the hydrochloric acid concentration increases, the roughness (Ra, µm) and area ratio (%) values increase. At this time, it can be seen that the increase rate of the area ratio value is significantly greater than the increase rate of the illuminance value.

Comparing Inventive Example 5 and Comparative Example 5, as the hydrochloric acid concentration increased, the value of the surface roughness was less than 1.5 μm, but the area ratio exceeded 50%, resulting in rolling defects in the steel sheet of Comparative Example 5 during final cold rolling.

Comparing Inventive Example 11 and Comparative Example 15, as the hydrochloric acid concentration increased, the surface roughness value exceeded 1.5 μm, and the area ratio also exceeded 50%, so that rolling defects occurred in the steel sheet of Comparative Example 15 during final cold rolling.

When comparing Inventive Example 4 and Comparative Example 16, as the hydrochloric acid concentration increased, the value of the surface roughness was less than 1.5 μm, but the area ratio exceeded 50%, so that rolling defects occurred in the steel sheet of Comparative Example 16 during final cold rolling.

Comparing Inventive Example 1 and Comparative Example 17, as the hydrochloric acid concentration increased, the value of the surface roughness was less than 1.5 μm, but the area ratio exceeded 50%, so that rolling defects occurred in the steel sheet of Comparative Example 17 during final cold rolling.

In addition, in Comparative Examples 15 to 17 in which the hydrochloric acid concentration exceeded 21%, as the hydrochloric acid concentration became excessive, side-reactants were rather formed, and foreign substances to be removed by the brush became excessive. As a result, the area ratio increased considerably, resulting in defects during the final cold rolling.

Referring to Table 1 with respect to the mesh number (N), it can be seen that as the mesh number increases, the roughness (Ra, μm) and area ratio (%) values increase.

Comparing Inventive Examples 10 and 11 and Comparative Examples 1 and 2, the area ratio value was less than 50% as the mesh number increased, but the surface roughness exceeded 1.5 µm. Has occurred.

Comparing Inventive Example 12 and Comparative Example 3, as the mesh number increased, the surface roughness exceeded 1.5 μm, and the area ratio value also exceeded 50%, so that rolling defects occurred in the steel sheet of Comparative Example 3 during final cold rolling.

Comparing Inventive Examples 1, 3, 9 and Comparative Example 7, as the mesh number increases, the area ratio value is less than 50%, but the surface roughness exceeds 1.5 µm, so that rolling defects occur in the steel sheet of Comparative Example 7 during final cold rolling. I did.

Comparing Inventive Examples 2 and 6 and Comparative Example 8, as the mesh number increased, the surface roughness exceeded 1.5 µm, and the area ratio value also exceeded 50%, resulting in rolling defects in the steel sheet of Comparative Example 8 during final cold rolling. .

In addition, Comparative Examples 7 to 14, which have a larger mesh number than 240, have a very small abrasive particle size or a nylon brush that has no polishing ability, so most of them have a surface roughness exceeding 1.5 μm, and an area ratio of 50 In excess of %, a rolling defect occurred during the final cold rolling.

Referring to the above, if the surface roughness (Ra, µm) value is less than 1.5 µm and the area ratio (%) value is less than 50% as in each of the invention examples, rolling defects occur in the stainless steel sheet during final cold rolling. It can be seen that it did not occur.

Therefore, the surface quality of the final cold-rolled steel sheet is the following equation (1) representing the surface roughness (Ra, μm) after pickling and brushing, and the following equation representing the area ratio (%) that the surface is not polished by the brush ( If 2) is satisfied, it can be seen that it is secured.

(1) (1.04 + 0.000801*N + 0.00492*T + 0.00451*C) <1.5

(2) (-59 + 0.0243*N + 0.341*T + 4.29*C) <50

(Here, N: mesh number of the silicon carbide abrasive particles, T: immersion time (seconds) of the steel sheet immersed in the hydrochloric acid bath, C: refers to the hydrochloric acid concentration (weight %) of the hydrochloric acid bath).

According to the above, since the scale removal apparatus and method of the low chromium ferritic stainless steel hot-rolled steel sheet according to the present invention directly immerse the steel sheet in a hydrochloric acid bath for pickling treatment, it is possible to simplify the complex pickling process through the sulfuric acid deposition step and the mixed acid deposition step. I can.

In addition, compared to the conventional stainless steel pickling process, it is eco-friendly because it does not emit pollutants such as NOx in that it does not use nitric acid because it does not use nitric acid.

In addition, the mechanical pickling process is simplified, and a stainless steel sheet having excellent surface quality can be provided even after cold rolling.

As described above, although exemplary embodiments of the present invention have been described, the present invention is not limited thereto, and those of ordinary skill in the art are within the scope not departing from the concept and scope of the following claims. It will be appreciated that various modifications and variations are possible.

1: Low chromium ferritic stainless steel hot rolled steel sheet
2: scale breaker
3: hydrochloric acid bath
4: brush
5: flushing device
6: drying device

Claims (8)

delete delete delete delete Immersing a low-chromium ferritic stainless steel hot-rolled steel sheet in a hydrochloric acid bath for pickling treatment; And
Removing scale remaining on the surface of the steel sheet and a reactant formed after the pickling treatment using a brush containing silicon carbide (SiC) abrasive particles,
It satisfies the following formula (1) and formula (2),
The hydrochloric acid concentration (C) of the hydrochloric acid bath is 18 to 21%, the immersion time (T) is 15 to 60 seconds,
The mesh number of the silicon carbide (SiC) abrasive particles is 80 to 240,
Before the steel sheet is immersed in the hydrochloric acid bath, the step of generating a crack on the surface of the scale using a scale breaker.
(1) (1.04 + 0.000801*N + 0.00492*T + 0.00451*C) <1.5
(2) (-59 + 0.0243*N + 0.341*T + 4.29*C) <50
(Here, N: mesh number of the silicon carbide abrasive particles, T: immersion time (seconds) of the steel sheet immersed in the hydrochloric acid bath, C: refers to the hydrochloric acid concentration (wt%) of the hydrochloric acid bath). delete delete delete

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