Phase transformation law of a Ti-microalloyed high-strength steel during continuous cooling
In order to study the phase transformation law of Ti-microalloyed high-strength steel under continuous cooling conditions,the microstructure changes and the undercooled austenite phase transformation law of low carbon steel(C-Mn steel)and Ti-microalloyed steel(Ti steel)during continuous cooling were studied through thermal expansion method and metallographic analysis.The influence of titanium element and deformation on the phase transformation law of the experimental steels was analyzed,and the relationship between continuous cooling transformation(CCT)and isothermal transformation(TTT)curves was discussed.The results show that with the increase of cooling rate,the main phase transformation microstructure of the experimental steels changes from ferrite to bainite.Adding titanium to the C-Mn steel improves the stability of undercooled austenite,inhibits the transformation of ferrite and pearlite,and promotes the transformation of bainite.The deformation in the unrecrystallized austenite zone causes the overall CCT curves of the experimental steel to shift to the upper left,increasing the starting temperature of phase transformation.Deformation increases the nucleation rate of ferrite,promotes ferrite phase transformation,and refines the ferrite structure.Deformation promotes bainite transformation,shortens lath bainite and refines bainite structure.
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