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Environment-friendly hot-rolling low-chromium ferrite stainless steel acid pickling method

An environmentally friendly, stainless steel technology, applied in the field of cold-rolled stainless steel production, can solve the problems of increased production cost per ton of steel, increased equipment investment and operating costs, environmental and human hazards, etc., to reduce maintenance times, prolong activity and service life, The effect of reducing the production cost

Inactive Publication Date: 2017-12-12
武汉众登科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] There is a layer of dense oxide scale on the surface of the hot-rolled low-chromium ferritic stainless steel strip. In order to reduce the hardness of the strip steel and improve the structure, the strip steel needs to be annealed. Scale, remove most of the scale on the surface of the strip steel, and then pass through the mixed acid (HNO 3 +HF) pickling removes the remaining scale on the surface of the strip and forms a passivation film on the surface of the strip, while the mixed acid pickling process will produce a large amount of highly polluted nitrogen-containing waste gas and nitrogen-containing wastewater, which will harm the environment and human beings. cause serious harm
[0003] At present, the Ministry of Environmental Protection of the People's Republic of China has formulated strict waste gas and wastewater discharge standards for the iron and steel industry. Most of them are around 1000mg / L. The new environmental protection law requires that the total nitrogen concentration of wastewater discharge is less than 15mg / L. If the total nitrogen discharge concentration of wastewater is to meet the standard, new environmental protection equipment must be installed, which will significantly increase equipment investment and operating costs. The emission concentration of nitrogen-containing exhaust gas is also high, and the general concentration is greater than 500mg / m 3 , while the new environmental protection law allows the emission concentration to be changed from the original 420mg / m 3 down to 150mg / m 3 , the above will lead to an increase of 50-200 yuan in production cost per ton of steel

Method used

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  • Environment-friendly hot-rolling low-chromium ferrite stainless steel acid pickling method

Examples

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Effect test

Embodiment 1

[0034] The present embodiment provides a hot-rolled 410S ferritic stainless steel (410S ferritic stainless steel is the lowest chromium content in ferritic stainless steel) pickling process, strip thickness 3mm, including the following steps:

[0035] 1) In the sulfuric acid pickling solution, H 2 SO 4 The concentration is 180g / L; the temperature of the sulfuric acid pickling solution is 77°C; the pickling treatment time is 45s.

[0036] 2) After pickling with sulfuric acid, the steel strip is immersed in the first section of nitric acid-free pickling solution for pickling. In the first nitric acid-free pickling solution, H 2 SO 4 Concentration is 16g / L, HCL concentration is 0g / L, Fe 3+ The concentration is 30g / L, Fe 2+ The concentration is 30g / L, the temperature is 35°C, and the pickling time is 45s.

[0037] 3) After the steel strip is pickled without nitric acid in the first stage, it is dipped in the second stage of nitric acid-free pickling solution for pickling. I...

Embodiment 2

[0041] This embodiment provides a pickling process for hot-rolled 410S ferritic stainless steel with a strip thickness of 3mm, including the following steps:

[0042] 1) In the sulfuric acid pickling solution, H 2 SO 4 The concentration is 250g / L; the temperature of the sulfuric acid pickling solution is 83°C; the pickling treatment time is 30s.

[0043] 2) After pickling with sulfuric acid, the steel strip is immersed in the first section of nitric acid-free pickling solution for pickling. In the first nitric acid-free pickling solution, H 2 SO 4 Concentration is 22g / L, HCL concentration is 1g / L, Fe 3+ The concentration is 40g / L, Fe 2+ The concentration is 10g / L, the temperature is 40°C, and the pickling time is 30s.

[0044] 3) After the steel strip is pickled without nitric acid in the first stage, it is dipped in the second stage of nitric acid-free pickling solution for pickling. In the second nitric acid-free pickling solution, H 2 SO 4 Concentration is 22g / L, H...

Embodiment 3

[0048] This embodiment provides a pickling process for hot-rolled 410S ferritic stainless steel with a strip thickness of 3mm, including the following steps:

[0049] 1) In the sulfuric acid pickling solution, H 2 SO 4 The concentration is 220g / L; the temperature of the sulfuric acid pickling solution is 80°C; the pickling treatment time is 40s.

[0050] 2) After pickling with sulfuric acid, the steel strip is immersed in the first section of nitric acid-free pickling solution for pickling. In the first nitric acid-free pickling solution, H 2 SO 4 Concentration is 18g / L, HCL concentration is 1g / L, Fe 3+ The concentration is 35g / L, Fe 2+ The concentration is 20g / L, the temperature is 38°C, and the pickling time is 40s.

[0051] 3) After the steel strip has been pickled without nitric acid in the first stage, it is dipped in the second stage of nitric acid-free pickling solution for pickling. In the second nitric acid-free pickling solution, H 2 SO 4 Concentration is 18...

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Abstract

The invention relates to an environment-friendly hot-rolling low-chromium ferrite stainless steel acid pickling method. The method comprises the step of sulfuric acid pickling, the step of first-stage non-sulfuric-acid pickling and the step of second-stage non-sulfuric-acid pickling. Main ingredients of acid liquor adopted in the steps of two stages of non-sulfuric-acid pickling comprise H2SO4, HCl, Fe3+ and Fe2+. In the acid pickling steps, the certain redox potential can be maintained by adding an oxidizing agent, and meanwhile the acid liquor contains a certain amount of additive (such as corrosion inhibitor and wetting agent). According to the stainless steel acid pickling method, the acid liquor for hot-rolling low-chromium ferrite stainless steel contains no nitric acid, high-pollution nitrogen-containing waste gas and waste water are not produced during acid pickling, accordingly, a waste gas denitriding device and a waste water denitriding device are omitted, and the equipment investment and the production cost are saved.

Description

technical field [0001] The invention belongs to the field of cold-rolled stainless steel production, and in particular relates to an environment-friendly pickling method for hot-rolled low-chromium ferritic stainless steel. Background technique [0002] There is a layer of dense oxide scale on the surface of the hot-rolled low-chromium ferritic stainless steel strip. In order to reduce the hardness of the strip steel and improve the structure, the strip steel needs to be annealed. Scale, remove most of the scale on the surface of the strip steel, and then pass through the mixed acid (HNO 3 +HF) pickling removes the remaining scale on the surface of the strip and forms a passivation film on the surface of the strip, while the mixed acid pickling process will produce a large amount of highly polluted nitrogen-containing waste gas and nitrogen-containing wastewater, which will harm the environment and human beings. cause serious harm. [0003] At present, the Ministry of Envi...

Claims

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Application Information

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IPC IPC(8): C23G1/08
CPCC23G1/081
Inventor 不公告发明人
Owner 武汉众登科技有限公司