Method for continuous pickling of double-phase stainless steel coil

Abstract

The invention relates to a method for continuous pickling of a double-phase stainless steel coil, which comprises the following steps: connecting a high-Cr and high-Ni austenitic stainless steel coil at the front end and the rear end of the double-phase stainless steel coil after hot-roll annealing; performing shot blasting on the steel coil at a low rotational speed before pickling; passing the annealed steel coil through a chemical pretreatment stage, wherein a medium is H2SO4, the concentration of H2SO4 is between 300 and 400 g/l and a pickling temperature is between 88 and 90 DEG C. and pickling catalysts of NaCl and hydrogen peroxide are added into the annealed steel coil; passing the steel coil through No.1 and No.2 chemical mixed pickling stages, wherein a medium is HNO3 and HF, the concentration of HNO3 is between 180 and 270 g/l, the concentration of HF is between 45 and 80 g/l and the pickling temperature is between 45 and 60 DEG C; passing the steel coil through No.1 and No.2 troughs, wherein a temperature is between 45 and 60 DEG C; and cutting the austenitic stainless steel at the front end and the rear end of the double-phase stainless steel. After the method for the continuous pickling of the double-phase stainless steel coil is adopted, the iron scale of the double-phase stainless steel coil is removed, the surface of the steel coil is bright and has high lustrousness, and the steel coil meets the using requirements of No.1 in GB4237.

Description

technical field [0001] The invention relates to a method for continuous pickling of duplex stainless steel coils. Background technique [0002] Due to the particularity of the composition and structure of duplex stainless steel, compared with other stainless steels, duplex stainless steel has higher chromium oxide content and molybdenum oxide content in the inner scale than other stainless steels. When the nitrogen content increases to a certain amount, the enrichment of nitrogen is very obvious, and the highest enrichment amount can reach 14 times of the nitrogen content of the matrix. The enrichment of nitrogen can make the oxide film not easy to damage, and the combination of molybdenum and nitrogen , can significantly improve the stability of the oxide film. In the oxide layer, the more alloying elements are contained, the more complex the structure type of the oxide will be. This difference in scale is the root cause of the difficulty in pickling. When using the cont...

AI Technical Summary

Problems solved by technology

When using the continuous line coil pickling process before improvement, in order to obtain steel coils with better surface quality, the continuous line speed is relatively slow, but the continuous line has speed requirements for steel coils. If the speed is too slow, the steel coils will stay for a long time In the annealing furnace, it is easy to overburn. After pickling at the slowest speed allowed by the process, the surface of the steel coil will be black and the color will be poor, which cannot meet the requirements for use.