Cold annealing and acid pickling technology of 204 Cu stainless steelwith thickness smaller than or equal to 1.5 mm

Abstract

The invention discloses a cold annealing and acid pickling technology of 204 Cu stainless steel with the thickness smaller than or equal to 1.5 mm. The cold annealing and acid pickling technology of the 204 Cu stainless steel with the thickness smaller than or equal to 1.5 mm comprises the steps of cold rollingannealing and mixed acid pickling, in the cold rolling annealing step, different temperatures are set in heating areas Z1 to Z10 in a furnace hearth of an annealing furnace, the mixed acid pickling step comprises the steps of neutral saltelectrolysis, mixed acid pickling andbrushing through brush rollers, and working modes of the brush rollers comprise that the current of the first brush roller and the second brush roller is 15.4-26.8 A, the rotating speed of the first brush roller and the second brush roller is600-800 rmp, and the load of thefirst brush roller and the second brush roller is 2-3 mm; and the current of the thirdbrush roller and the fourth brush roller is10.7-16.4A, the rotating speed of the third brush roller and the fourth brush roller is600-800 rmp,and the load ofthe third brush roller and the fourth brush roller is2-3 mm. Compared with the prior art, the cold annealing and acid pickling technology of the 204 Cu stainless steel with the thickness smaller than or equal to 1.5 mm has the advantages that annealing temperature standard is detailed accordingto the thickness interval, the cold annealing and acid pickling technology is applied to preparing the 204 Cu stainless steel with the thickness smaller than or equal to 1.5 mm, the thickness of oxide skin is decreased, uniformity of the oxide skin is improved, white spots do not exist on the upper surface and the lower surface of a stainless steel plate in full width, and the surface quality ofa product is improved.

Description

technical field [0001] The invention belongs to the technical field of stainless steel production, in particular to a cold annealing and pickling process for eliminating white spots on the surface of stainless steel. Background technique [0002] According to its metal structure, stainless steel is divided into five categories: austenitic stainless steel, ferritic stainless steel, austenitic-ferritic (duplex) stainless steel, martensitic stainless steel and precipitation hardening stainless steel. At present, the commonly used stainless steel is mainly austenitic Stainless steel accounts for about 80% of the market share, among which 304 stainless steel is more popular. According to its chemical composition, austenitic stainless steel is divided into two series of chromium-nickel series (300 series in the United States) austenitic stainless steel and chromium-manganese series (200 series in the United States) austenitic stainless steel. Chromium-manganese (200 series) auste...

AI Technical Summary

Problems solved by technology

[0012] Due to the existing technology of 204Cu steel grade stainless steel after cold rolling and rolling, the steel plate comes out of the continuous annealing furnace during annealing, and the full width of the upper and lower surfaces of the strip steel is irregular, and black oxide scales are piled up, and after electrolysis of sodium sulfate (Na 2 SO 4 solution electrolysis), mixed acid (HF solution + HNO 3 solution) after pickling, the surface of the steel plate does not have agglomerated black scale, but there are agglomerated white spot defects on the upper and lower sides of the strip steel, which cannot be eliminated by grinding with sandpaper, which seriously affects the quality of the stainless steel plate and cannot be used for surface purposes, thereby affecting product sales.

[0013] After a lot of research and analysis, it is concluded that after the horizontal continuous annealing of 204Cu stainless steel, the surface oxide skin of the steel plate is thicker, and the furnace temperature plays a decisive role in the thickness of the oxide skin, so the above defects are mainly caused by the surface oxide skin during furnace annealing. Uneven generation leads to

The reasons: 1. The annealing temperature benchmark is too broad. At present, the thickness of 204Cu stainless steel after cold rolling and rolling is 0-2.0mm, and the width is not limited. The annealing temperature benchmark in this thickness range only divides 2 temperature benchmark intervals; (2) The annealing temperature is too high , the current annealing reference temperature is too high, especially the Z1&Z2 temperature is too high, the steel plate absorbs too much heat to increase the thickness of the scale on the surface of the strip, and the high temperature increases the unevenness of the scale on the surface of the strip, and the scale remains after pickling There are group-shaped white spot defects; (3) The brush roller is not strong enough to destroy the oxide scale on the surface of the strip, resulting in residual oxide scale on the surface

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