Effect of Cr and Ni on the microstructure and properties of corrosion-resistant steel
Based on the base chemistry of Q345GNH steel,the steel samples with different Cr(mass fraction of 0.5％,2％,3％,4％and 5％)and Ni(mass fraction of 0.5％and 1％)contents were prepared and their performances were compared by series of tests.Meanwhile,the effect mechanism of Cr and Ni on properties of steel was analyzed by thermodynamic calculations.The results show that with increas-ing Cr content from 2％to 3％,the yield strength and tensile strength increased by 83 MPa and 122 MPa,respectively,mainly because of bainite formation,and when content of Cr exceed 4％,the elongation rate was less than 10％caused by more than 80％bainite in the steel.When compared with the Q345GNH steel,with more than 2％Cr addition can provide the relative corrosion rate of steel less than 70％after 120 h salt spray corrosion.This improvement was due to formation of stable Cr-contain-ing corrosion products and self-corrosion potential shift positively caused by Ni.Comprehensively con-sidering each individual index,the optimum additions for Cr was 2％and for Ni was 1％.
corrosion-resistant steelsCrNimechanical performanceneutral salt spray corrosionpo-tential-pH diagram
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