Method for improving the qualified rate of surface pickling of 430 stainless steel hot-rolled coils

Abstract

The present invention discloses a method for improving the qualified rate of surface pickling of 430 stainless steel hot-rolled coils, which is applied to the hot-rolled pickling line of 430 stainless steel hot-rolled coils. It includes the control of the scale breaker parameters in the descaling process of the hot-rolled pickling line, the process control of the shot blasting machine in the shot blasting process of the hot-rolled pickling line, the stepped acid concentration control process in the sulfuric acid tank and the mixed acid tank of the hot-rolled pickling line, and the process control of the brushing machine after the sulfuric acid tank process of the hot-rolled pickling line. By using the present invention, the residual rate of hot-line scale of 430 stainless steel hot-rolled coils is reduced from 4.5% in the prior art to 1.3%, and the proportion of the residual defect of scale on the cold plate is reduced from 0.5% in the prior art to below 0.1%. Thus, the re-washing rate of the residual hot-line scale is significantly reduced, and the qualified rate of the cold plate is significantly improved. Thereby, the loss caused by the need for secondary re-washing due to the residual scale can be reduced, and the rejection loss caused by the non-conformity of the residual scale on the cold plate can be reduced, having a significant effect of cost reduction and efficiency increase.

Description

Technical Field

[0001] The present invention belongs to the technical field of cold rolling and pickling of stainless steel, and more specifically relates to a method for improving the pickling qualification rate of the surface of 430 stainless steel hot rolled coils. Background Art

[0002] 430 stainless steel is a representative of ferritic stainless steel. It has better thermal conductivity than austenitic stainless steel and a smaller thermal expansion coefficient than austenitic stainless steel. It is a general steel grade with good corrosion resistance and is widely used in industries such as household appliances, home appliance parts, tableware, and architectural decoration.

[0003] The production process of 430 stainless steel is as follows: smelting and continuous casting in a steel mill, removing surface defects of the billet by grinding, then rolling the billet into a hot rolled coil with a thickness of 2.0 - 8.0 mm through hot rolling. The hot rolled coil is annealed in a bell-type annealing furnace to fully recrystallize the material. After bell annealing, the coil is subjected to descaling, shot blasting, and pickling through a hot rolling pickling line (hereinafter referred to as hot line pickling) to remove the surface scale, and a 430 stainless steel coil with a NO.1 surface is obtained. The 430 stainless steel coil with a NO.1 surface can be directly used for end uses on the one hand, and on the other hand, it can be processed by a bright annealing line or a cold rolling pickling line (hereinafter referred to as cold line pickling) after cold rolling. After leveling, a BA or 2B surface can be obtained, or a 2D surface can be obtained after passing through a tension leveling line, or a NO.4 or HL surface can be obtained after passing through a grinding line.

[0004] Due to the recrystallization treatment in a bell-type furnace, the 430 stainless steel product needs to be kept at 850 °C for 8 hours, plus the heating and cooling processes, resulting in a long oxidation time on the surface of the coil, a thick and dense oxide layer. This brings relatively great difficulties to hot line pickling. After the hot line pickling process, there will still be scale residue defects on the NO.1 surface of some 430 stainless steel coils.

[0005] After actual measurement, the proportion of scale residue defects after hot line pickling in the early stage is 4.5%. On the one hand, for the coils found with scale on the hot line, only the method of passing through the line again to eliminate the defects can be adopted, which will increase the cost by 185 yuan per ton of steel; on the other hand, when the 430 stainless steel coils with a NO.1 surface having scale residue defects after hot line pickling are cold rolled into cold plates with 2B or BA surfaces later, the proportion of cold plates with scale residue defects reaches 0.5%. The cold plates with scale residue defects cannot meet the requirements for delivery and use, and finally can only be treated as scrap steel, resulting in a loss of up to 5500 yuan per ton of steel. Summary of the Invention

[0006] In order to solve the above technical problems existing in the prior art, the present invention provides a method for improving the pickling qualification rate of the surface of 430 stainless steel hot rolled coils, so as to reduce the scale residue rate of 430 stainless steel hot rolled coils during hot line pickling and improve the first pass rolling qualification rate of cold plates.

[0007] The method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils of the present invention is applied to the hot-rolling pickling line of 430 stainless steel hot-rolled coils. The method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils includes: controlling the parameters of the descaling machine in the descaling process of the hot-rolling pickling line, controlling the process of the shot blasting machine in the shot blasting process of the hot-rolling pickling line, the stepped acid concentration control process in the sulfuric acid tank and the mixed acid tank of the hot-rolling pickling line, and controlling the process of the brushing machine after the sulfuric acid tank process of the hot-rolling pickling line, wherein:

[0008] In the control of the descaling machine parameters, the descaling machine adopts an elongation control mode, and different elongation rates are adopted according to the thickness specifications of 430 stainless steel hot-rolled coils. Specifically:

[0009] Thickness h (mm) Elongation δ (%) h≤3.0 2.0 ≤ δ < 3.0 3.0＜h≤4.0 1.2 ≤ δ < 2.0 4.0＜h≤5.0 0.6 ≤ δ < 1.2 5.0＜h≤6.0 0.3 ≤ δ < 0.6

[0010] And in the control of the descaling machine parameters, the roll gap of the descaling rolls of the descaling machine is determined according to the thickness specifications of 430 stainless steel hot-rolled coils in the following manner:

[0011] Thickness h (mm) Reduction of 1# descaling roll / mm Reduction of 2# descaling roll / mm Reduction of 3# descaling roll / mm h≤4.0 100～138 100～138 60～70 4.0＜h≤5.0 80～100 80～100 50～60 5.0＜h≤6.0 55～65 55～65 30～40

[0012] In the control of the shot blasting machine process, the steel shots sprayed by the shot blasting machine are high-carbon cast steel shots, and their chemical composition by mass percentage is: C content 0.85 - 1.2%, Si content ≥ 0.4%, Mn content ≥ 0.4%, S content ≤ 0.05%, P content ≤ 0.05%, the diameter of the steel shots is 0.125 - 0.85 mm, and the mixing ratio control of the shot blasting machine bin is:

[0013] Shot diameter 0.18 mm 0.3 mm 0.355 mm 0.425 mm 0.5 mm Ratio ≥ 5% and ≤ 15% ≥15％ ≥30％ ≥30％ ≤10％

[0014] The balance is steel shots of other diameter specifications;

[0015] In the stepped acid concentration control process, the pickling equipment used is 1# sulfuric acid tank + 2# sulfuric acid tank + 1# mixed acid tank + 2# mixed acid tank. The sulfuric acid tanks control the acid concentration and iron ion concentration according to the following parameters:

[0016] Sulfuric acid tank Sulfuric acid concentration (g / l) Iron ion concentration (g / l) 1# sulfuric acid tank 220～280 ≤75 2# sulfuric acid tank 180～220 ≤60

[0017] The mixed acid tanks control the acid concentration and iron ion concentration according to the following parameters:

[0018] Mixed acid tank Hydrofluoric acid concentration (g / l) Nitric acid concentration (g / l) Iron ion concentration (g / l) 1# mixed acid tank 10～15 120～150 ≤45 2# mixed acid tank 6～10 80～120 ≤45

[0019] In the process control of the brushing machine, in the brushing machine configured after the 2# sulfuric acid tank, the brush rolls use bristles containing abrasives. The diameter of the bristles is 1.0 mm to 1.5 mm. The bristle material is a blend of nylon 612 and nylon 610, where the ratio of nylon 612 to nylon 610 is 2:1. The proportion of abrasives in the bristles is 15% to 30%. The abrasive material is SiC, and the diameter of the abrasives is 0.125 mm to 0.18 mm. The rotational speed of the brush rolls is 300 to 400 revolutions per minute, and the current of the brush rolls is 100 A to 150 A.

[0020] As a specific implementation, in the method for improving the surface pickling qualification rate of 430 stainless steel hot-rolled coils:

[0021] In the scale breaker parameter control, according to the following method, different elongation rates are adopted according to the thickness specifications of 430 stainless steel hot-rolled coils:

[0022] Thickness h (mm) Elongation δ (%) h≤3.0 2.5 3.0＜h≤4.0 1.6 4.0＜h≤5.0 0.9 5.0＜h≤6.0 0.5

[0023] And in the scale breaker parameter control, the roll gap of the scale breaker is determined according to the thickness specifications of 430 stainless steel hot-rolled coils in the following manner:

[0024] Thickness h (mm) Reduction of 1# descaling roll / mm Reduction of 2# descaling roll / mm Reduction of 3# descaling roll / mm h≤4.0 138 135 60 4.0＜h≤5.0 80 85 50 5.0＜h≤6.0 57 58 30

[0025] In the process control of the shot blasting machine, the steel shots sprayed by the shot blasting machine are high-carbon cast steel shots. Its chemical composition by mass percentage is: C content 1.1%, Si content 0.6%, Mn content 0.65%, S content 0.02%, P content 0.02%. The mixing ratio control of the shot blasting machine hopper is:

[0026] Shot diameter 0.125 mm 0.18 mm 0.3 mm 0.355 mm 0.425 mm 0.5 mm 0.6 mm Ratio 0.11％ 8.24％ 19.35％ 34.65％ 30.12％ 7.40％ 0.13％

[0027] In the stepped acid concentration control process, the sulfuric acid tank and the mixed acid tank control the acid concentration and iron ion concentration according to the following parameters respectively:

[0028] Sulfuric acid tank Sulfuric acid concentration (g / l) Iron ion concentration (g / l) 1# sulfuric acid tank 256 54 2# sulfuric acid tank 201 35

[0029] Mixed acid tank Hydrofluoric acid concentration (g / l) Nitric acid concentration (g / l) Iron ion concentration (g / l) 1# mixed acid tank 12 135 41 2# mixed acid tank 7 95 29

[0030] In the process control of the brushing machine, the diameter of the bristles is 1.2 mm, the proportion of abrasives in the bristles is 19.62%, the rotational speed of the upper brush roll is 350 revolutions per minute and the current is 125 A, and the rotational speed of the lower brush roll is 350 revolutions per minute and the current is 131 A

[0031] The method for improving the surface pickling qualification rate of 430 stainless steel hot-rolled coils of the present invention has the following advantages and beneficial effects:

[0032] By using the present invention, the residual rate of hot-line scale on 430 stainless steel hot-rolled coils is reduced from 4.5% in the prior art to 1.3%, and the proportion of residual scale defects on cold plates is reduced from 0.5% in the prior art to below 0.1%. As a result, the re-washing rate of residual hot-line scale is significantly reduced, and the qualification rate of cold plates is significantly improved. Thereby, it is possible to reduce the losses caused by the need for secondary re-washing due to residual scale, as well as the rejection losses caused by non-conforming residual iron scales on cold plates, showing a significant effect of cost reduction and efficiency improvement. Detailed Embodiments

[0033] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] The method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils of the present invention is applied to the hot-rolling pickling line of 430 stainless steel hot-rolled coils, and includes the control of the scale breaker parameters in the scale breaking process of the hot-rolling pickling line, the control of the shot blasting machine process in the shot blasting process of the hot-rolling pickling line, the stepped acid concentration control process in the sulfuric acid tank and the mixed acid tank of the hot-rolling pickling line, and the control of the brushing machine process after the sulfuric acid tank process of the hot-rolling pickling line, wherein:

[0035] In the control of the scale breaker parameters, the scale breaker adopts an elongation control mode, and different elongation rates are used according to the thickness specifications of 430 stainless steel hot-rolled coils. Specifically:

[0036] Thickness h (mm) Elongation δ (%) h≤3.0 2.0 ≤ δ < 3.0 3.0＜h≤4.0 1.2 ≤ δ < 2.0 4.0＜h≤5.0 0.6 ≤ δ < 1.2 5.0＜h≤6.0 0.3 ≤ δ < 0.6

[0037] And in the control of the scale breaker parameters, the roll gap reduction amount of the scale breaker is determined according to the thickness specifications of 430 stainless steel hot-rolled coils in the following manner:

[0038] Thickness h (mm) Reduction of 1# descaling roll / mm Reduction of 2# descaling roll / mm Reduction of 3# descaling roll / mm h≤4.0 100～138 100～138 60～70 4.0＜h≤5.0 80～100 80～100 50～60 5.0＜h≤6.0 55～65 55～65 30～40

[0039] In the control of the shot blasting machine process, the steel shots sprayed by the shot blasting machine are high-carbon cast steel shots, and their chemical compositions by mass percentage are: C content 0.85 - 1.2%, Si content ≥ 0.4%, Mn content ≥ 0.4%, S content ≤ 0.05%, P content ≤ 0.05%. The diameter of the steel shots is 0.125 - 0.85 mm, and the mixing ratio control of the shot blasting machine bin is:

[0040] Shot diameter 0.18 mm 0.3 mm 0.355 mm 0.425 mm 0.5 mm Ratio ≥ 5% and ≤ 15% ≥15％ ≥30％ ≥30％ ≤10％

[0041] The balance is steel shots of other diameter specifications;

[0042] In the stepped acid concentration control process, the pickling equipment used is 1# sulfuric acid tank + 2# sulfuric acid tank + 1# mixed acid tank + 2# mixed acid tank. The acid concentration and iron ion concentration in the sulfuric acid tanks are controlled according to the following parameters:

[0043] Sulfuric acid tank Sulfuric acid concentration (g / l) Iron ion concentration (g / l) 1# sulfuric acid tank 220～280 ≤75 2# sulfuric acid tank 180～220 ≤60

[0044] The acid concentration and iron ion concentration in the mixed acid tanks are controlled according to the following parameters:

[0045] Mixed acid tank Hydrofluoric acid concentration (g / l) Nitric acid concentration (g / l) Iron ion concentration (g / l) 1# mixed acid tank 10～15 120～150 ≤45 2# mixed acid tank 6～10 80～120 ≤45

[0046] In the process control of the brushing machine, in the brushing machine configured after the 2# sulfuric acid tank, the brush roll uses bristles containing abrasives. The diameter of the bristles is 1.0 mm to 1.5 mm. The bristle material is a blend of nylon 612 and nylon 610, and the ratio of nylon 612 to nylon 610 is 2:1. The proportion of abrasives in the bristles is 15% to 30%. The abrasive material is SiC, and the diameter of the abrasives is 0.125 mm to 0.18 mm. The rotational speed of the brush roll is 300 to 400 revolutions per minute, and the current of the brush roll is 100 A to 150 A.

[0047] In the method for improving the surface pickling qualification rate of 430 stainless steel hot-rolled coils of the present invention, the descaling machine adopts an elongation control mode, and different elongation rates are used according to the thickness specifications of the 430 stainless steel hot-rolled coils. The principle is that the elongation rate of the oxide scale on the surface of the steel coil is smaller than that of the substrate. When the steel strip passes through the descaling machine, it is repeatedly bent under the pressure of the descaling rolls and the tension of the front and rear tension rolls. When the elongation rate is controlled within the range of 0.3% to 3.0%, the surface oxide scale can fall off and become loose, which can play a descaling role. In addition, after the 430 stainless steel hot-rolled coils are annealed in the hood, the plate shape is generally double-sided wave, and the uneven plate shape affects the uniformity of shot blasting descaling and also has a certain impact on the pickling uniformity. Therefore, in the method for improving the surface pickling qualification rate of 430 stainless steel hot-rolled coils of the present invention, descaling by the descaling machine is adopted, which has the effect of improving the plate shape.

[0048] In the method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils in the present invention, the chemical components C, Si, and Mn are used as the steel shot for the shot blasting machine as required. After centrifugal casting and tempering, a tempered martensite or tempered troostite structure is obtained, which has high hardness, with an HRC of 41-50, and certain toughness. It is thrown by a high-speed rotating impeller head and can effectively remove the surface scale when hitting the steel plate surface. In addition, the diameter of the steel shot sprayed by the shot blasting machine is at least 0.125 mm and at most 0.85 mm. When the diameter of the steel shot is large, the impact force on the surface scale of the steel plate is strong, and the scale removal is fast, but the coverage is not complete. Therefore, large particles cannot be pursued only, and an appropriate amount of small-sized steel shot needs to be combined to increase the impact coverage. Therefore, in the method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils in the present invention, in order to take into account the surface roughness, the mixing ratio in the shot blasting machine hopper is controlled in the above manner.

[0049] The functions of sulfuric acid pickling are as follows: First, it directly reacts with the scale (Fe2O3, Fe3O4, FeO) to eliminate the scale; second, it reacts with the matrix Fe to generate hydrogen, playing a role in skin bursting. The functions of mixed acid pickling are as follows: Using a mixed solution composed of hydrofluoric acid and nitric acid, it removes the remaining surface scale and eliminates the Cr-depleted layer on the stainless steel surface, making the surface passivated and white. In the conventional pickling process control method, the acid concentration control ranges of the 1# and 2# sulfuric acid tanks are the same, and the acid concentration controls of the 3# and 4# mixed acid tanks are the same. In the method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils in the present invention, the purpose of designing the stepped acid concentration control process is as follows: The high-concentration sulfuric acid in the 1# sulfuric acid tank quickly removes the surface scale, and the low-concentration sulfuric acid in the 2# sulfuric acid tank further reacts with the matrix to generate hydrogen for skin bursting and reacts with the remaining scale; the high-concentration nitric acid in the 1# mixed acid tank quickly reacts with the remaining tiny scale on the surface to remove the surface Cr-depleted layer, and the low-concentration nitric acid in the 2# mixed acid tank mainly passivates the surface. In addition, in the method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils in the present invention, the iron ion concentration in the mixed acid solution should be strictly controlled to avoid the direct reaction of hydrofluoric acid with iron ions to produce FeF3 precipitation and cause caking.

[0050] In the method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils in the present invention, the brushing machine applied after the 2# sulfuric acid tank is composed of a brush roll and a rubber roll (back pressure roll) symmetrically arranged up and down, which is used to improve the surface brushing effect and serve as a supplementary descaling after sulfuric acid descaling.

[0051] The following illustrates the method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils in the present invention with specific embodiments.

[0052] Example 1

[0053] The method for improving the pickling qualification rate of the surface of 430 stainless steel hot-rolled coils in Example 1 includes:

[0054] In the scale breaker parameter control, the scale breaker adopts an elongation control mode and uses different elongations according to the thickness specifications of the 430 stainless steel hot-rolled coils. Specifically:

[0055] Thickness h (mm) Elongation δ (%) h≤3.0 2.5 3.0＜h≤4.0 1.6 4.0＜h≤5.0 0.9 5.0＜h≤6.0 0.5

[0056] And in the scale breaker parameter control, the roll gap of the scale breaker is determined according to the thickness specifications of the 430 stainless steel hot-rolled coils in the following manner:

[0057] Thickness h (mm) Reduction of 1# descaling roll / mm Reduction of 2# descaling roll / mm Reduction of 3# descaling roll / mm h≤4.0 138 135 60 4.0＜h≤5.0 80 85 50 5.0＜h≤6.0 57 58 30

[0058] In the shot blasting machine process control, the steel shots sprayed by the shot blasting machine are high-carbon cast steel shots. Their chemical composition by mass percentage is: C content 1.1%, Si content 0.6%, Mn content 0.65%, S content 0.02%, P content 0.02%. The hardness of the steel shots is HRC 47. The mixing ratio control of the shot blasting machine hopper is:

[0059] Shot diameter 0.125 mm 0.18 mm 0.3 mm 0.355 mm 0.425 mm 0.5 mm 0.6 mm Ratio 0.11％ 8.24％ 19.35％ 34.65％ 30.12％ 7.40％ 0.13％

[0060] In the stepped acid concentration control process, the pickling equipment used is 1# sulfuric acid tank + 2# sulfuric acid tank + 1# mixed acid tank + 2# mixed acid tank. The sulfuric acid tanks control the acid concentration and iron ion concentration according to the following parameters:

[0061] Sulfuric acid tank Sulfuric acid concentration (g / l) Iron ion concentration (g / l) 1# sulfuric acid tank 256 54 2# sulfuric acid tank 201 35

[0062] The mixed acid tanks control the acid concentration and iron ion concentration according to the following parameters:

[0063] Mixed acid tank Hydrofluoric acid concentration (g / l) Nitric acid concentration (g / l) Iron ion concentration (g / l) 1# mixed acid tank 12 135 41 2# mixed acid tank 7 95 29

[0064] In the brushing machine process control, the brush rolls of the brushing machine configured after the 2# sulfuric acid tank use bristles containing abrasives. The bristle diameter is 1.2 mm. The bristle material is a blend of nylon 612 and nylon 610, and the ratio of nylon 612 to nylon 610 is 2:1. The abrasive accounts for 19.62% in the bristles. The abrasive material is SiC, and the abrasive diameter is 0.125 mm to 0.18 mm. The rotational speed of the upper brush roll is 350 rpm and the current is 125 A. The rotational speed of the lower brush roll is 350 rpm and the current is 131 A.

[0065] Using the method for improving the surface pickling qualification rate of 430 stainless steel hot-rolled coils in Embodiment 1 of the present invention, 7500 coils of 430 stainless steel hot-rolled coils are produced. Among them, 98 coils are judged for heavy pickling of scale in the hot line, and the heavy pickling rate is 1.3%, that is, the residual rate of scale in the hot line is only 1.3%. After pickling the 430 stainless steel hot-rolled coils by the above hot line, 4013 coils of cold-rolled sheets are produced. Among them, 4 coils are scrapped due to residual scale, that is, the proportion of cold-rolled sheets with residual scale defects is reduced to less than 0.1%.

[0066] In summary, compared with the prior art, the method for improving the surface pickling qualification rate of 430 stainless steel hot-rolled coils of the present invention has the following advantages and beneficial effects:

[0067] The residual rate of scale in the hot line of 430 stainless steel hot-rolled coils is reduced from 4.5% in the prior art to 1.3%, and the proportion of cold-rolled sheets with residual scale defects is reduced from 0.5% in the prior art to below 0.1%. Thus, the heavy pickling rate of residual scale in the hot line is significantly reduced, and the qualification rate of cold-rolled sheets is significantly improved. Thereby, it is possible to reduce the losses caused by the need for secondary re-pickling due to residual scale, and reduce the scrapping losses caused by non-conforming residual scale on cold-rolled sheets. Through actual measurement, for a production line with an annual pickling of 360,000 tons of 430 products in the hot line and a cold-rolled sheet supply of 200,000 tons / year, it is possible to reduce the re-pickling of residual scale by 11,520 tons / year, save costs of 2.1312 million yuan / year, and reduce the scrapping of residual scale by 600 tons / year, increasing efficiency by 4.4 million yuan / year. By applying the method for improving the surface pickling qualification rate of 430 stainless steel hot-rolled coils of the present invention, the annual cost reduction and efficiency increase can be as high as 6.5312 million yuan.

[0068] It should be noted that in this article, the term "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device.

[0069] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the present invention.

Claims

1. A method for improving the qualified rate of surface pickling of 430 stainless steel hot-rolled coils, which is applied to the hot-rolling pickling line of 430 stainless steel hot-rolled coils, and is characterized in that, It can reduce the residual rate of scale on the hot-rolled coil of 430 stainless steel during hot-line pickling and improve the qualified rate of the first cold rolling. The method for improving the pickling qualified rate of the surface of the 430 stainless steel hot-rolled coil includes: controlling the parameters of the descaling machine in the descaling process of the hot-rolled pickling line, controlling the process of the shot blasting machine in the shot blasting process of the hot-rolled pickling line, the stepped acid concentration control process in the sulfuric acid tank and the mixed acid tank of the hot-rolled pickling line, and the process control of the brushing machine after the sulfuric acid tank process of the hot-rolled pickling line. Among them: In the control of the descaling machine parameters, the descaling machine adopts an elongation control mode and uses different elongations according to the thickness specifications of the 430 stainless steel hot-rolled coil. Specifically: And in the control of the descaling machine parameters, the roll gap of the descaling rolls of the descaling machine is determined according to the thickness specifications of the 430 stainless steel hot-rolled coil in the following manner: In the process control of the shot blasting machine, the steel shots sprayed by the shot blasting machine are high-carbon cast steel shots, and their chemical composition by mass percentage is: C content 0.85 - 1.2%, Si content ≥ 0.4%, Mn content ≥ 0.4%, S content ≤ 0.05%, P content ≤ 0.05%. The diameter of the steel shots is 0.125 - 0.85 mm, and the mixing ratio control of the shot blasting machine hopper is: The balance is steel shots of other diameter specifications; In the stepped acid concentration control process, the pickling equipment used is 1# sulfuric acid tank + 2# sulfuric acid tank + 1# mixed acid tank + 2# mixed acid tank. The sulfuric acid tank controls the acid concentration and iron ion concentration according to the following parameters: The mixed acid tank controls the acid concentration and iron ion concentration according to the following parameters: In the process control of the brushing machine, in the brushing machine configured after the 2# sulfuric acid tank, the brush rolls use bristles containing abrasives. The diameter of the bristles is 1.0 mm - 1.5 mm, and the bristle material is a blend of nylon 612 and nylon 610, where the ratio of nylon 612 to nylon 610 is 2:

1. The proportion of abrasives in the bristles is 15% - 30%, the abrasive material is SiC, the diameter of the abrasives is 0.125 mm - 0.18 mm, the rotational speed of the brush rolls is 300 - 400 rpm, and the current of the brush rolls is 100 A - 150 A.

2. The method for improving the qualified rate of surface pickling of 430 stainless steel hot-rolled coils according to claim 1, characterized in that: In the control of the descaling machine parameters, different elongations are adopted according to the thickness specifications of the 430 stainless steel hot-rolled coil in the following manner: And in the control of the descaling machine parameters, the roll gap of the descaling rolls of the descaling machine is determined according to the thickness specifications of the 430 stainless steel hot-rolled coil in the following manner: In the process control of the shot blasting machine, the steel shots sprayed by the shot blasting machine are high-carbon cast steel shots, and their chemical composition by mass percentage is: C content 1.1%, Si content 0.6%, Mn content 0.65%, S content 0.02%, P content 0.02%. The mixing ratio control of the shot blasting machine hopper is: In the stepped acid concentration control process, the sulfuric acid tank and the mixed acid tank respectively control the acid concentration and iron ion concentration according to the following parameters: In the process control of the brushing machine, the diameter of the bristles is 1.2 mm, the proportion of abrasives in the bristles is 19.62%, the rotational speed of the upper brush roll is 350 rpm and the current is 125 A, and the rotational speed of the lower brush roll is 350 rpm and the current is 131 A.