Simultaneous Precipitation and Recrystallization during Hot Deformation of Ti, Nb and V Microalloyed Steel

Abstract

Recrystallization is a major means for controlling the grain size of steel during hot deformation. Usually, small grain sizes deliver superior mechanical properties. To aid the grain size controlling effect of recrystallization, small precipitates of carbo-nitride particles can be utilized to hinder the movement of grain boundaries. Interestingly, these particles are not only effective during grain growth, but also during recrystallization. In the present work, a recently developed state-parameter based model is introduced that is capable of describing both, the individual processes of static recrystallization, dynamic and static recovery and precipitation as well as the mutual interaction of these mechanisms in the course of elevated temperature processing. The evolution of state parameters within the model is discussed and the simulation results are compared to experimental information. Within our approach, a vast amount of experimental data for microalloyed steel is reproduced on basis of a single set of input parameters

Influence of Hot Deformation and Precipitates on the Recrystallization of Nb-V-Ti Free-Cutting Steel

“…(2) The hot deformation activation energy of the Nb-V-Ti free-cutting steel was calculated to be 398.13kJ/mol. The constitutive equation of the peak stress for the steel can be described by a hyperbolic sine equation, as follows: 𝜀̇= 1.33 × 10 16 [sinh (0.01049σ) 6.017 ]exp (− 398138 𝑅𝑇 )…”

“…Therefore, the dynamic activation energy Q and the related parameters of the experimental steel can be obtained, as reported in Table 3. By substituting the calculated dynamic recrystallization parameters into Equation (3), the hot processing equations of the experimental Nb-V-Ti free-cutting steel can be obtained, as in Equation (10): 𝜀̇= 1.33 × 10 16 [sin ℎ (0.01049𝜎) 6.017…”

“…In the deformation process, the greater the Z [39,40] value is, the lower the degree of dynamic recrystallization. 𝑍 = 𝜀ė𝑥𝑝 ( 398130 8.134𝑇 ) = 1.33 × 10 16 [sin ℎ (0.01049𝜎)] 6.017 (13) By substituting the calculated dynamic recrystallization parameters into Equation (3), the hot processing equations of the experimental Nb-V-Ti free-cutting steel can be obtained, as in Equation ( 10):…”

“…This reflects the relationship between flow stress and strain, strain rate, and deformation temperature. Buken et al [16] studied the recrystallization process of Nb-V-Ti microalloyed steel, and proposed a state parameter-based model to describe static recrystallization, dynamic and static recovery, and precipitation during high temperature processes. Qian et al [17] used a 3D atomic distribution map to characterize the relationship between power dissipation efficiency value and area.…”