Dynamic Recrystallization Behavior of Q370qE Bridge Steel

Bridge steel has been widely used in recent years for its excellent performance. Understanding the high-temperature Dynamic Recrystallization (DRX) behavior of high-performance bridge steel plays an important role in guiding the thermomechanical processing process. In the present study, the hot deformation behavior of Q370qE bridge steel was investigated by hot compression tests conducted on a Gleeble 3800-GTC thermal-mechanical physical simulation system at temperatures ranging from 900 ℃ to 1100 ℃ and strain rates ranging from 0.01 s^(−1) to 10 s^(−1). The obtained results were used to plot the true stress-strain and work-hardening rate curves of the experimental steel, with the latter curves used to determine the critical strains for the initiation of DRX. The Zener-Hollomon equation was subsequently applied to establish the correspondence between temperature and strain rate during the high-temperature plastic deformation of bridge steel. In terms of the DRX volume fraction solution, a new method for establishing DRX volume fraction was proposed based on two theoretical models. The good weathering and corrosion resistance of bridge steel lead to difculties in microstructure etching. To solve this, the MTEX technology was used to further develop EBSD data to characterize the original microstructure of Q370qE bridge steel. This paper lays the theoretical foundation for studying the DRX behavior of Q370qE bridge steel.

Effect of Deformation on Microstructure and Mechanical Properties of Medium Carbon Steel During Heat Treatment Process

The current research of the Q-P and Q-P-T process has been focused on controlling the heating temperature and holding time,or adding alloy elements into the steel to induce precipitation strengthening and improve the strength and plasticity of the steel.In this article,based on a quenching-partitioning-tempering(Q-P-T)process combined with a hot deformation technology,a deforming-quenching-partitioning-tempering(D-Q-P-T)process was applied to medium carbon steel.The effect of the heat treatment parameters on the microstructure and mechanical properties of experimental steel under deformation was studied.Through use of a scanning electron microscope(SEM),transmission electron microscopy(TEM)and tensile tests,the optimal heat treatment conditions for realizing high strength and plasticity that meet the safety requirements were obtained.The mechanism for the D-Q-P-T process to improve the strength and plasticity of experimental steel was discussed.A multiphase composite structure of lath martensite and retained austenite was obtained.Compared with the Q-P-T process,use of the D-Q-P-T process can increase the strength of steel by 57.77 MPa and the elongation by 5%.This study proposes a method to improve the strength and plasticity of steel.