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测定了300M超高强度钢在蒸馏水和3.5％NaCl水溶液环境下的应力腐蚀断裂性能。试验结果表明,300M钢经淬火和低温回火获得回火马氏体组织。当抗拉强度为1915MPa时,其应力腐蚀界限强度因子为20.8MPam~(1/2) ,应力腐蚀裂纹扩展速率为0.014mm/min。当抗拉强度提高到2020MPa,则K_(ISCC)下降17.8％△a/△t增加64％。采用250℃等温淬火,获得下贝氏体和马氏体混合组织,300M钢的应力腐蚀性能有了明显的改善。1200°高温淬火,因奥氏体晶粒粗大,杂质元素沿晶界偏聚增多,虽K_(ISCC)值略有升高,而△a/△t比常规热处理时增大10倍。
The stress corrosion cracking behavior of 300M ultra high strength steel in distilled water and 3.5% NaCl aqueous solution was measured. The test results show that the tempered martensite structure of 300M steel is obtained by quenching and tempering at low temperature. When the tensile strength of 1915MPa, the stress corrosion limit strength factor of 20.8MPam ~ (1/2), stress corrosion crack growth rate of 0.014mm / min. When the tensile strength is increased to 2020MPa, K_ (ISCC) decreases 17.8% △ a / △ t increases 64%. Using 250 ℃ isothermal quenching to obtain lower bainite and martensite mixed structure, 300M steel stress corrosion has been significantly improved. As the austenite grain size is large, the segregation of impurity elements along the grain boundaries increases. Although the value of K_ (ISCC) slightly increases, the △ a / Δt increases by 10 times than that of the conventional heat treatment.