Comparison of the Influence of Austenitization and Quenching Conditions on the Microstructure of HSLA 38MNVS6 Steel

Abstract The study investigates the effect of various heat treatment conditions on HSLA steel 38MnVS6, aiming to expand its potential applications in the automotive industry. The study focuses on optimizing the parameters of austenitizing, quenching, and low-temperature tempering. The objective was to achieve a predominantly martensitic microstructure and ensure a minimum hardness of 50 HRC throughout the cross-section of the material. Three heat treatment regimes were applied to the samples at an austenitizing temperature of 870°C. In the first two regimes, quenching was performed in oil at 120°C and 70°C, while in the third regime, a different quenching oil was used at the same temperature of 70°C. For each sample, surface and core hardness were measured using the Rockwell method, followed by detailed microstructural analysis. The results showed that increasing the carbon potential in the furnace reduced the ferrite fraction at the surface and positively affected surface hardness. A key finding was that the use of low-viscosity quenching oil enables the achievement of the critical cooling rate required for the desired hardness. Moreover, lowering the oil temperature effectively suppressed the formation of undesirable fine lamellar pearlite (troostite). The results indicate the potential of the experimental material for applications subjected to high dynamic loading. Therefore, further research should include fatigue strength and tribological testing to further validate the material performance.