Continuous annealing and acid washing method for medium-chromium ultrapure ferrite stainless steel

Abstract

A continuous annealing and acid washing method for medium-chromium ultrapure ferrite stainless steel comprises the process flow of cold rolling, annealing heat treatment, acid washing, final water washing, drying, flattening and packaging, and is characterized in that in the acid washing process flow, the acid washing solution is prepared from 120-150g / L of 65% nitric acid, 2-4g / L of 40% hydrofluoric acid and water. According to the invention, in the chemical acid washing stage, reasonable concentration ratio of nitric acid to hydrofluoric acid is adopted and proper acid washing speed is controlled to carry out acid washing on medium-chromium ferrite stainless steel. As a result, on one hand, the performance of a medium-chromium ferrite stainless steel passivation film is obviously improved, and the corrosion resistance of the surface of a medium-chromium ferrite stainless steel 2B board is significantly improved, and on the other hand, the process flow of the existing production factory is not needed to be changed, a special passivation treatment procedure is not needed, and the production cost is significantly lowered.

Description

technical field [0001] The invention relates to the surface treatment of the stainless steel plate in the continuous annealing and pickling production process of the stainless steel cold-rolled plate, especially a new process for improving the corrosion resistance of the medium chromium ultra-pure ferritic stainless steel. Background technique [0002] In recent years, the problem of global environmental pollution has aroused great attention from countries all over the world to the automobile exhaust emission system. In many countries, the graded requirements for automobile fuel economy and automobile exhaust emissions are becoming more and more stringent. The traditional cast metal and aluminum-plated carbon steel materials for exhaust systems can no longer meet the requirements. The green environmental protection material stainless steel that meets the 3R requirements is especially high The performance of ferritic stainless steel has been widely used. [0003] The automob...

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Problems solved by technology

[0004] In general, the medium-chromium ultra-pure ferritic stainless steel plate for automobile exhaust pipe is 2B plate, and the main process flow of 2B plate production is cold rolling → annealing → cooling → drying → sodium sulfate electrolysis → water washing → nitric acid electrolysis → water Rinsing→chemical pickling→water rinsing→drying→leveling→packing, the chemical pickling process is the final process that affects the performance of the passivation film on the surface of ultra-pure ferritic stainless steel 2B. However, in the actual production process, the existing acid The passivation film on the surface of ultra-pure ferritic stainless steel produced by washing process cannot meet the corrosion resistance requirements of automobile exhaust pipes