Continuous pickling method for super austenitic stainless steel coil

Abstract

The invention relates to a continuous pickling method for a super austenitic stainless steel coil. The method comprises the following successive steps: I, connecting the front end and the rear end of a hot-rolled and annealed super austenitic stainless steel coil to duplex stainless steel coils; II, carrying out shot blasting on the super austenitic stainless steel coil at a low rotating speed before pickling; III, allowing the coil to pass through a chemical pretreatment section, with a medium being H2SO4 and a pickling speed being 13 to 18 m / min; IV, allowing the coil to pass through a first chemical mixed pickling section, with a medium being HNO3 + HF and a pickling temperature being 50 to 65 DEG C; V, allowing the coil to pass through a second chemical mixed pickling section, with a medium being HNO3 + HF; VI, allowing the coil to pass through a first water tank; VII, allowing the coil to pass through a second water tank; and VIII, cutting off the duplex stainless steel at the front end and the rear end of the hot-rolled and annealed super austenitic stainless steel. The surface of the steel coil pickled by using the continuous pickling method provided by the invention meets requirements on No. 1 plates by GB 4237, and high pickling efficiency is obtained.

Description

[0001] technical field [0002] The invention relates to a method for continuous pickling of super austenitic stainless steel coils, in particular to a method for pickling to remove oxide scales formed on the surface of super austenitic stainless steel coils after hot rolling and annealing. Background technique [0003] Due to the particularity of the composition of super austenitic stainless steel, the total mass percentage of chromium, nickel and molybdenum exceeds 50% of the matrix composition. The difference between super austenitic stainless steel and other ordinary stainless steel inner oxide scales lies in the oxide content of molybdenum It is much higher than that of other stainless steels. At the same time, because its composition contains a large amount of nickel, when the nickel content increases to a certain amount, the oxide film is extremely difficult to damage and has a strong repair ability. The combination of molybdenum and nickel can significantly improve t...

AI Technical Summary

Problems solved by technology

The existing method of continuous pickling of super austenitic stainless steel coils is pickled at a speed of 13-18m / min, the surface is blackened, and the oxide scale cannot be completely removed, which cannot meet the requirements of No.1 plate in GB4237

In order to obtain steel coils with better surface quality, the continuous line speed can only be reduced without changing the pickling process, and the speed is not greater than 8m / min, which reduces the pickling efficiency

At the same time, at a lower speed, other types of stainless steel coils connected with super austenitic stainless steel will stay in the annealing furnace longer than normal because the alloy content does not reach the grade of super austenitic stainless steel. to 3 times, it is easy to overburn, and after pickling at a speed not greater than 8m / min, the surface of the steel coil will turn black and the color will be poor