Effects of electrochemical corrosion characteristis on electrochemical cold drawing of Q235 steel bar

摘要

In this work, the electrochemical corrosion behaviors of Q235 steel bar in tap water, NaCl, NaCl + HCl and H2SO4 aqueous solutions, and their effects on electrochemical cold drawing (ECD) were investigated, as well as on cold drawing in air for comparison. The results indicate that the higher the corrosion rate and the more uniform the corrosion are, the larger the decrement of drawing force of ECD is, and the drawing force in the H2SO4 solution is decreased by 39% compared with DIA. Previous electrochemical corrosions in these solutions can slightly soften the steel surface layer, but further obviously decrease the drawing force of ECD, and these two phenomena are all proportional to the corrosion rate. The surface softening of the previous electrochemical corrosions is verified by positron annihilation technology to be mainly attributed to the formation of vacancies. The further decrease of the drawing force should be chiefly contributed to the relaxation effect of the already formed vacancies on dislocations. But the effects of the electrochemical corrosions occurred during ECD are very limited because the time for corrosions is quite short. So the decrease in drawing force might be ascribed to the additional dislocation flux originated from the simultaneous effects of current, chemical corrosion and stress during ECD.