Method for annealing and pickling 409L stainless steel

Abstract

The invention discloses a method for annealing and pickling 409L stainless steel through neutral salt electrolyzing and mixed acid pickling technology. The method comprises the steps as follows: a, annealing, controlling the concentration of excess oxygen to 3 to 5%, controlling the heating temperature to 950-1100 DEG C, wherein the heating time is 1 to 3 minutes per millimeter based on thickness; b, electrolyzing, and controlling the specific gravity of neutral salt to 1.2 to 1.24, pH to 3.5 to 4.5, temperature to 70 to 90 DEG C, and current strength in electrifying to 4500 to 5500A; and c, pickling, wherein pickling solution in the first stage includes 9 to 13% of HNO3 and 0.1 to 0.2% of HF, pickling solution in the second stage includes 11 to 15% of HNO3 and 0.1 to 0.2% of HF, the temperature of the pickling solutions in the two stages is at 50 to 60 DEG C, and the pickling time is 30 to 50 seconds. With the adoption of the method disclosed by the invention, the collinear annealing and pickling of FeCr system and FeCrNi system stainless steels can be achieved; and good 2D surface can be obtained.

Description

technical field [0001] The invention relates to a cold rolling process of FeCr series stainless steel, in particular to a method for annealing and pickling of 409L stainless steel on a FeCrNi series stainless steel annealing and pickling line. Background technique [0002] The cold rolling process of stainless steel mainly includes steps such as cold rolling, annealing, pickling, smoothing, finishing, etc., and the present invention specifically relates to a method for annealing and pickling of 409L stainless steel. [0003] Since the annealing and pickling of FeCrNi stainless steel mainly adopts neutral salt electrolysis + mixed acid pickling process, and FeCr stainless steel (409L stainless steel is one of the varieties with a very large market demand in FeCr stainless steel) due to its scale structure and other reasons Neutral salt electrolysis + mixed acid pickling process is difficult to effectively remove the scale on the surface, and most of the world uses nitric acid...

AI Technical Summary

Problems solved by technology

[0011] As the price of Ni in the international market has always remained high, the cost of 300 series stainless steel has risen and the profit margin has decreased. In order to adapt to the market situation and expand varieties, many companies are gradually developing 400 series stainless steel with higher yields. For stainless steel annealing and pickling, the results of annealing and pickling of FeCr stainless steel are not very satisfactory, and the surface quality is mostly EE level, mainly because the oxide scale cannot be completely removed.

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