Study On Microstructure And Properties Of3Cr13Martensitic Stainless Steel

The strength of traditional martensite chromium stainless steel can be greatly improved by quenching and tempering treatment, which affects the ductility and toughness of materials and greatly limits the application of this kind of stainless steel in industrial production.In recent years, people gradually realize the potential of residual austenite in the aspect of improving the toughness of martensite steel, and quenched partition technology is the effective way to obtain stable residual austenite. Based on3Cr13as tested steel, a variety of Q&P heat treatment system was designed in view of quenching temperature, partition temperature and partition time. And the influence of Q&P heat treatment process on the microstructure transformation and mechanical properties of3Cr13were investigated by charactering the tested steel samples and comparing its mechanical properties. The evaluation of the possibility of the application Q&P heat treatment process in the traditional martensitic stainless steel was done as well. The conclusion was obtained as follows:1.The beginning temperature(Ms) of the transformation of supercooled austenite to martensite in tested steel which was completely austenitizied was about120℃. The content of martensite increased, as quenching temperature declined. The residual austenite content at room temperature was around12%and the lowest carbon content of retained austenite at room temperature was stable at around0.9%.2. After Q&P treatment, the microstructure of the steel was composite microstructure of martensite+retained austenite, and the maximum value of retained austenite was up to1.2%. With decreasing quenching temperature, residual austenite content increased first and then decreased, and the highest value of residual austenite content appeared at60℃(35%). When the quenching temperature changed from350℃to400℃, there was little difference in the content of retained austenite. Specimens partitioned at450℃had the highest residual austenite content. 3. When the quenching temperature was below60℃, the tested steels after Q&P treatment could obtain the ideal coordination of strength and ductility. The main feature of the tested steel was the low yield strength, high tensile strength and uniform elongation rate. When the quenching temperature was below55℃, with the increasing of QT, the yield strength of steel decreased gradually, and the tensile strength increased gradually as well, and when the QT was40℃, the maximum elongation appeared.4. The parameters of Q&P process had little effect on tensile strength and impact ductility. The yield strength of steel increased obviously with the rising of partitioning temperature and the prolongation of the partitioning time, when the partitioning temperature were at350℃and400℃. When the partitioning temperature was at450℃, the yield strength of the steel continuously increased. When partitioning temperature was at450℃and the partitioning time was beyond40min, the plasticity decreased.