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Cold-rolled 409L ferrite stainless steel strip steel acid pickling process

A technology of stainless steel strip and ferrite, applied in the field of cold-rolled stainless steel production, can solve the problems of high surface roughness of strip steel, shortened service life of acid solution, slow mixed acid pickling speed, etc. Wastewater treatment costs and the effect of reducing maintenance downtime

Inactive Publication Date: 2019-11-19
WISDRI ENG & RES INC LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0002] When pickling cold-rolled 409L ferritic stainless steel strip, mixed acid (HNO 3 +HF) pickling process, however, in the pickling process, as the reaction proceeds, the concentration of metal ions in the solution increases gradually, and the metal ions will combine with F ˉ ions to form fluoride precipitation, resulting in a decrease in the concentration of F ˉ ions in the solution , so that the activity of the acid solution is continuously reduced, the efficiency of mixed acid pickling is reduced, the service life of the acid solution is shortened, and the amount of acid solution waste is increased, resulting in an increase in production costs
At the same time, insoluble fluoride can easily block pumps and pipelines, and the cost of subsequent wastewater treatment will also increase. This is because Fˉ ions can prevent the decomposition of nitric acid solution, but Fˉ ions can accelerate the dissolution of scale through pitting corrosion
[0003] However, due to the poor density of the passivation film on the surface of the chromium-based stainless steel metal substrate, the metal substrate is easily corroded by hydrofluoric acid. If the concentration of hydrofluoric acid is high , will cause the surface roughness of the strip after pickling to be high and dull; and when the concentration of hydrofluoric acid is small, the pickling speed of mixed acid is too slow
[0004]In addition, with the prolongation of pickling time, the formed fluoride precipitates will adhere to the surface of the steel strip and affect the quality of pickling, and will also be deposited in the circulation system In pipelines and circulation tanks, it is easy to block acid pipelines and affect the circulation of acid liquid; moreover, the oxide scales on the surface of strip steel will combine with fluoride precipitation to form hard sludge, which is difficult to remove, resulting in the need for frequent shutdowns for maintenance and reduced production efficiency

Method used

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  • Cold-rolled 409L ferrite stainless steel strip steel acid pickling process

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Embodiment 1

[0043] The present embodiment provides a pickling process for cold-rolled 409L ferritic stainless steel strip, the thickness of the strip to be treated is 1.4mm; the method comprises the following steps:

[0044] 1) Pickling is carried out by immersing the steel strip in an electrolytic cell with an electrolyte, the electrolyte being Na 2 SO 4 and H 2 SO 4 Mixture, where Na 2 SO 4 The concentration is 195g / L, by adding H 2 SO 4 Adjust the pH of the electrolyte to 3.2, the temperature of the electrolyte to 81°C, and the current density to 10A / dm 3 , The electrolytic pickling time is 15s.

[0045] 2) Grinding and scrubbing the strip steel after electrolytic pickling, the diameter of the roller brush used is 0.8mm, the bristles contain 180 mesh silicon carbide abrasives, the motor speed is set to 800rpm, and the motor current is 180A.

[0046] 3) The strip steel after grinding and brushing is immersed in the first mixed acid solution for pickling, in the first mixed acid ...

Embodiment 2

[0049] The present embodiment provides a pickling process for cold-rolled 409L ferritic stainless steel strip, the thickness of the strip to be treated is 1.2mm; the method comprises the following steps:

[0050] 1) Pickling is carried out by immersing the steel strip in an electrolytic cell with an electrolyte, the electrolyte being Na 2 SO 4 and H 2 SO 4 Mixture, where Na 2 SO 4 The concentration is 188g / L, by adding H 2 SO 4 Adjust the pH of the electrolyte to 2.8, the temperature of the electrolyte to 80°C, and the current density to 8.5A / dm 3 , The electrolytic pickling time is 14s.

[0051] 2) Grinding and scrubbing the electrolytic pickled steel strip, using a roller brush with a diameter of 0.8mm and containing 180 mesh silicon carbide abrasives, setting the motor speed to 700rpm, and the motor current to 175A.

[0052] 3) The strip steel after grinding and brushing is immersed in the first mixed acid solution for pickling, in the first mixed acid solution, HNO...

Embodiment 3

[0055] The present embodiment provides a pickling process for cold-rolled 409L ferritic stainless steel strip, the thickness of the strip to be treated is 1.1mm; the method comprises the following steps:

[0056] 1) Pickling is carried out by immersing the steel strip in an electrolytic cell with an electrolyte, the electrolyte being Na 2 SO 4 and H 2 SO 4 Mixture, where Na 2 SO 4 The concentration is 183g / L, by adding H 2 SO 4 Adjust the pH of the electrolyte to 2.6, the temperature of the electrolyte to 78°C, and the current density to 7.5A / dm 3 , The electrolytic pickling time is 14s.

[0057] 2) Grinding and scrubbing the electrolytic pickled steel strip, using a roller brush with a diameter of 0.8mm and containing 180-mesh silicon carbide abrasive, setting the motor speed to 600rpm, and the motor current to 170A.

[0058] 3) The strip steel after grinding and scrubbing is immersed in the first mixed acid solution for pickling. In the first mixed acid solution, HNO...

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Abstract

The invention relates to a cold-rolled 409L ferrite stainless steel strip steel acid pickling process. The cold-rolled 409L ferrite stainless steel strip steel acid pickling process comprises the following steps of S1, carrying out electrolytic pickling; S2, carrying out grinding and scrubbing; S3, carrying out first-stage mixed acid pickling; and S4, carrying out second-stage mixed acid pickling.In the step S1, strip steel is immersed in an electrolytic tank with an electrolyte for acid pickling; in the step S2, the strip steel after grinding and scrubbing is subjected to electrolytic pickling; in the step S3, the strip steel after grinding and scrubbing is immersed in a first mixed acid solution for acid pickling; and in the step S4, the strip steel after the first-stage mixed acid pickling is immersed in a second mixed acid solution for acid pickling. According to the process, not only can the acid pickling quality of the surface of the strip steel be improved, but also blockage ofa pipeline or a circulating tank is avoided, the shutdown maintenance frequency is reduced, and the production efficiency is improved.

Description

technical field [0001] The invention relates to the technical field of cold-rolled stainless steel production, in particular to a pickling process for cold-rolled 409L ferritic stainless steel strip. Background technique [0002] When pickling cold-rolled 409L ferritic stainless steel strip, mixed acid (HNO 3 +HF) pickling process, however, in the pickling process, as the reaction proceeds, the concentration of metal ions in the solution increases gradually, and the metal ions will combine with F ˉ ions to form fluoride precipitation, resulting in a decrease in the concentration of F ˉ ions in the solution , so that the activity of the acid solution is continuously reduced, the efficiency of mixed acid pickling is reduced, the service life of the acid solution is shortened, and the amount of acid solution waste is increased, resulting in an increase in production costs. At the same time, insoluble fluoride can easily block pumps and pipelines, and the cost of subsequent was...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C25F1/06C23G1/08
CPCC23G1/085C25F1/06
Inventor 谢霞乔军贺立红尚志广
Owner WISDRI ENG & RES INC LTD
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