Research On Second Phase Precipitation, Mechanical Properties And Deformation Behavior Of Microalloy Steel On CSP

Been studied for several decades, microalloy technology on traditional process have became a complete theoretical system. In contrast, Thin Slab Continuous Casting and Rolling have new characteristics of microalloy technology because of its hight casting speed, great cooling intensity and direct hot charge rolling features compared with traditional process.The article have studied microalloy steel G600 which is a trial production on line of CSP in a factory. According to calculating the precipitates quantity of (Nb,V,Ti) carbonitride on every process temperature range at static state and balance condition, the author have preliminarily discussed the effect of carbonitride. The experiment parts include detecting the microstructure and the second phase of G600, testing mechanical properties in room temperature and high temperature , ascertaining the temperature range of low plastic and simulating the process of hot strip mill on CSP.Thermodynamic calculation show that, in G600, micro amounts of Ti mainly precipitated at Solidification Process and high Temperature region of austenite. Nb keep solid solution condition at the soaking temperature, mainly precipitated at process of hot strip mill. All V being solid solution condition in austenite, mainly precipitated atγ→αregion and in ferrite. The detecting of the Microstructure and the Second Phase show that, the microstructures about hot rolled plate of G600 mainly is bainite,the grain size above standard of ASTM 10. The size of the second phase about microalloy is reached 5nm, distribution is very uniform. The strength of G600 is quite high, vertical yield strength is above 585MPa , plastic is quite low , the difference of vertical and horizontal is relatively large. yield ratio keep a high level. it is necessary to improve the mechanical properties of G600. the 3rd region of brittle is between 740℃and 860℃,the 1st is between 1240℃and 1300℃, it has a excellent thermoplastic compared with Q235B. The Experiment of thermal simulation Show that, deformation , deformation temperature and cooling speed after rolling have a great effect on final strength. The larger deformation , the lower deformation temperature and the higher cooling speed after rolling will make a higher final strength. The effect of deformation rate is not obvious.