the effect of heat treatment on microstructure and mechanical properties of steel CK67
Now, with the development of rapid-fire system operating conditions, high rate of fire, requires high temperature and high impact of increasing, in addition to having sufficient strength material, ablation resistance, the toughness requirements are getting higher and higher. Researchers with CK67 steel, for example, the material is heat-treated, namely: quenching and tempering (Q & T), isothermal quenching and tempering (A & T), quenching and carbon allocation and tempering (Q & P & T), by means of an optical microscope ( OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), hardness test, tensile test, impact experiments, the researchers heat treatment process on microstructure and properties of test steel, optimizing its organization and performance, and better tap the potential of its toughness regard. The results showed that:
(1) After Q & P & T and Q & T process, the organization of test steel are tempered martensite and residual austenite (including retained austenite between martensite laths is mainly distributed in, showing a thin film (10 ~ 40nm) and tempered martensite laths inside precipitates fine carbides dispersed ε- (100nm or so); after isothermal (Austempering) process, organizational test steel is martensite, bainite and residual austenite , matrix dispersion precipitation of fine cementite; compared with Q & T process technology and A & T, Q & P & T amount of retained austenite process up 8.8%;
(2) After the Q & P & T process, the yield strength of test steel, tensile strength and toughness are 1011.0MPa, 1630.6MPa and 109.7J / cm2, its impact toughness than after Q & T treatment increased 19.8%, compared by A & T handle After the increase of 9.7%, while its yield ratio decreased from 0.82 (A & T) to 0.62; film-like tissue in the presence of residual austenite is the main reason for increased impact toughness;
(3) impact toughness test steel with retained austenite, lower bainite volume fraction increased with the increase, while the contribution of retained austenite impact toughness greater than the lower bainite; the intensity of the martensite strength (back Fire martensite strength), lower bainite strength, fine grain strengthening and other factors determine; by Q & T, A & T, after the Q & P & T process, fracture mode test steel are ductile fracture.
