Stress Corrosion Test Research Of 316L Austenitic Stainless Steel In Complex Medium Condition

Stress corrosion crack accident occurs frequently in petroleum chemical equipments, which causes serious economical loss and human injury. Austenitic stainless steel, as the ordinary material of petroleum chemical equipments, many experts all over the world have made lots of stress corrosion research on it, and obtained many results. Because of the complex of effect factors and mechanism, there are still some problems should be discussed thoroughly.This paper choosed 316L austenitic stainless steel as the research object, slow strain rate test (SSRT) and constant strain pre-cracked specimen test are adopted to study the stress corrosion behavior of 316L in sulfureted hydrogen and chlorin hydronium solution. The tests are designed by even design method, the concentration and temperature are mainly considered as the effect parameters to the stress corrosion. By stepwise regression analysis of test results, the notabilities of effect on stress corrosion cracking susceptive indexes of medium parameters were revealed. The main conclusions of this paper are as follows:(1) The SSRT of 316L shows that among the parameter of the test condition, temperature and the concentration of chlorine hydronium have more effects on the stress corrosion sensitivity index. With temperature and the concentration of chlorine hydronium rising, the stress corrosion sensitivity index I_δincrease.(2) The stepwise regression analysis of the stress corrosion sensibility index I_δof 316L austenitic stainless steel shows that, in the condition of sulfureted hydrogen and chlorin ionmedium, the concentration of chlorin ion(x₁) and temperature (x₃) both effect the stress corrosion sensibility index I_δgreatly, the concentration of sulfureted hydrogen(x₂) and temperature (x₃) may interact to the stress corrosion sensibility index I_δ. The interaction math model of the stress corrosion sensibility index I_δand the test parameter is as follows:(3) The constant strain pre-cracked specimen test show that, the stress corrosion crack would occur in sulfureted hydrogen and chlorin ion condition, the cracking rate was about 10-9mm/s. The threshold stress intensity factors K_ISCC of the 316L base material is notbigger than 102.30 MPa(?) , the that of 316L heat affect zone material is not bigger than1.00.43 MPa(?).(4) The stress corrosion crack mechanism of 316L in the sulfureted hydrogen and chlorin ion medium is anodic dissolution, the chlorin ion oringenate the stress corrosion crack, and the sulfureted hydrogen accelerated the crack.