Analysis Of Surface Defects Caused By Pickling In Hot Rolled BN1G Stainless Steel Sheets And Determination Of Annealing Process For 2205 Duplex Phase Stainless Steel

In the iron and steel metallurgy field, the pickling is an important process in the steel surface treatment and a key process before cold rolled production. The aim of pickling mainly removes the oxide layer and chromium depleted layer forming in the surface of a sheet during hot rolling and annealing processes. Besides, the stainless steel surface is performed by passivation treatment to improve the corrosion resistance of sheet and the clear surface of the sheet is obtained. By trace statistics for different time stages in near two years, it found that the surface defects of BN1 G steel(Fe-13.56Cr-1.31Ni-9.88Mn-0.45Si-0.09C)sheets caused by pickling mainly contain oxide skin residues,pickling spots, pickling patterns, color difference, while the probability of mechanical damage is relative low. Therefore, this thesis analyzes the origins of the surface defects caused by pickling and gives the corresponding resolving methods.2205 duplex stainless steel especially suitable for making various industrial heat exchanger,and thus duplex stainless steel requires the combination of strength and elongation. Rolling hard state of 2205 duplex stainless steel(00Cr22Ni5Mo3N) often exists temperature anomaly in bright annealing, which results in lower strength due to too high temperature or lower elongation due to too low temperature. Therefore,the thesis studied at first various heat treatments including heating temperature and holding time, and then measured their mechanical properties, finally determine the optimum annealing process.