Effect of tempering temperature on microstructures and properties of niobium and titanium microalloying low carbon bainite steel

Abstract

Abstract. The effect of tempering temperature on microstructures and mechanical properties of niobium and titanium microalloying low carbon bainite steel was investigated. The results indicate that the mechanical properties change is mainly controlled by the structure evolution, and as the structure evolution during tempering is complex, the mechanical properties do not monotonously increase or decrease with the increasing of tempering temperature. IntroductionHight strength low carbon bainite steel is a new developed steel, which always shows high strength, high toughness and excellent welding performance, and it has been widely used in the engineering machinery, shipbuilding, oil and gas transmission pipeline, etc. Especialy in engineering machinery area, along with the development trends of large scale and lightweight, request for higher yield strength, impact toughness and welding performance of the structural parts has been put forward. At present, the widely used bainite steel with the yield strength of 460 MPa or 550 MPa is mainly prepared by a low cost process named TMCP[1], for the higher yield strength bainite steel, it is widely manufacturated by tempering after reheating and quenching process [2]. As the cost of tempering after reheating and quenching is high, so using tempering after TMCP process to instead it is of great significance. During this new process, through reasonable design of rolling and cooling, the high density dislocation that formed during the low temperature severe finishing rolling can be reserved, then the nuclear point during the phase deformation will be increased, the microstructures is refined, after tempering, the comprehensive mechanical properties of the steel will be finally improved [3]. In this paper, niobium and titanium microalloying steel was chosen as the study object, by tempering after TMCP process, bainite steel with higher yield strength was finally prepared, the effect of tempering temperature on microstructures and mechanical properties of this steel was investigated.

A multi-scale crystal plasticity model for cyclic plasticity and low-cycle fatigue in a precipitate-strengthened steel at elevated temperature

“…Recently, Huang et al (2013) have shown, through Charpy impact test, that the reduced activation ferritic martensitic steel (similar to the material examined in the current work), with M 23 C 6 coarsened by heat treatment, has less absorbed energy than the material with no such coarsening. The absorbed energy in Charpy impact tests for low carbon bainite steels with different tempering temperatures has been shown to have almost positive correlation with ductility (tensile elongation) by Li et al (2012). Therefore, the result of Huang et al (2013) implies that the coarsening M 23 C 6 reduces material ductility.…”