The Effect of Inclusions on a Medium Temperature Transformation Microstructure and Toughness of High-Strength HSLA Steel

Abstract

In this study, the evolution of high-strength HSLA steel microstructure was studied using high-temperature laser confocal microscopy and SEM, TEM, and EPMA techniques. The effect of precipitates on grain boundary migration of austenite during high-temperature heating and the effect of inclusions in undercooled austenite on AF phase transformation were studied. The effect of multiphase microstructure on impact toughness was studied by Gleeble thermal simulation at 550, 600, and 650 °C. The results show that the austenite grain is refined by TiN pinning at high temperatures, and a large number of NbC and VCN are precipitated in ferrite for precipitation strengthening. The (Ti-Mn-O) + (Al + Si + Mn-O) + MnS composite inclusions with smaller sizes have a greater promoting effect on the nucleation of acicular ferrite than single-phase MnS. With a decrease in isothermal temperature, the content of acicular ferrite increases. When the isothermal temperature is 550 °C, an increase in the maximum impact toughness of acicular ferrite with large-angle grain boundary is clearly observable.

Thermodynamic Modelling for Heat Analysis and Prediction in Precision Transmission Systems: A Focus on Gear Operation

“…Traditional studies on gear heat have predominantly centered around conventional thermodynamic theories and empirical formulas, which have demonstrated the capacity to yield reasonably accurate results under specific conditions [25,26]. Nonetheless, these methodologies often reveal their limitations when confronted with intricate working environments characterized by variable loads, speeds, and lubrication conditions [27][28][29][30]. This is particularly evident when the dynamic characteristics and nonlinear behavior of gears are taken into consideration, domains in which traditional approaches exhibit deficiencies in terms of predictive accuracy and responsiveness.…”