Effect Of Zirconium Content On Austenite Structure During Hot Deformation Of Titanium Microalloyed Low Carbon Steel

Ti microalloy steel not only has low cost,but also has excellent comprehensive mechanical properties,which has become the main research and development direction of iron and steel industry.However,the chemical property of Ti is very active and the melting loss is large.Adding a small amount of Zr in Ti microalloy steel can improve the solid solubility of Ti in austenite,stabilize the precipitation of nano TiC at low temperature,which is conducive to obtain fine and uniform austenite structure in the process of controlled rolling,and improve the comprehensive mechanical properties of steel.At the same time,it has a certain guiding significance for the formulation of rolling process in the production process.In this paper,the self-designed Ti-Zr microalloy low carbon steel(0.035Zr steel,0.091Zr steel)and Ti microalloy low carbon steel(high Ti steel)are used as research objects,and the titanium microalloy is simulated by the Gleeble-3800 thermal simulation experimental machine Process of controlled low carbon steel,the dynamic recrystallization and hot deformation behavior of the test steel were studied,the critical strain value and hot deformation activation energy of the dynamic recrystallization of the Ti-Zr microalloyed low carbon steel were determined,and the Ti-Zr was established The hot working equation of the microalloyed low carbon steel,and finally,the deformation induced precipitation behavior of the microalloyed carbide during the hot deformation of the experimental steel was studied by transmission electron microscopy.By studying the single-pass thermal simulation deformation and multi-pass thermal simulation deformation behavior of the test steel,the dynamic recrystallization behavior,hot deformation behavior and precipitation behavior of the deformed austenite in the controlled rolling process of zirconium-titanium microalloyed low carbon steel were revealed.The influencing law of the preliminary discussion on the precipitation mechanism of the precipitation phase.The results of single pass thermal simulation show that:the increase of Zr content can inhibit the dynamic recrystallization behavior of Ti-Zr microalloyed low carbon steel,increase the critical strain value of dynamic recrystallization of Ti-Zr microalloyed low carbon steel,delay the growth rate of recrystallized grains and refine the recrystallized grains.The increase of Zr content can improve the activation energy of hot deformation of Ti-Zr microalloyed low carbon steel.The activation energy of hot deformation of 0.035Zr steel is 419.16 k J/mol,and that of 0.091Zr steel is 433.05 k J/mol.Thermal simulation isothermal and variable temperature multi-pass deformation research results show that both Ti-Zr microalloyed low carbon steel and Ti microalloyed low carbon steel can completely recrystallize deformed austenite when deformed above 1000?.With the increase of deformation temperature,the average grain size of austenite recrystallization of the three test steels increased.Comparing the three test steels,the average grain size of austenite recrystallization of Ti microalloyed low carbon steel is smaller than that of Ti-Zr microalloyed low carbon steel,but the austenite grains The size uniformity is poor.The Ti-Zr microalloyed low-carbon steel has a smaller precipitate size(<100 nm)after hot deformation.As the Zr content increases,the number of precipitated phases in the steel increases and its size decreases.In addition,in addition to the(Ti,Zr)C composite precipitation phase,there are two gourd-like twin precipitation phases of TiC+ZrC and Zr₂SC+Ti₂SC.