Thermodynamic Study of the High-Temperature Partitioning Process of Carbon Elements in Intercritical Quenching and Partitioning High-Strength Steels

The paper has investigated the effect of soaking time in the two-phase zone before quenching on 0.22C-1.5Si-2.0Mn-0.035Al hot-rolled steel. Based on the Dictra two-dimensional kinetic model, we explore the diffusion behavior of carbon under different conditions to uncover the mechanism behind the high-temperature partitioning behavior of the carbon and its impact on the stability of austenite. The results have shown that after intercritical quenching and partitioning (IQ&P) treatment, the tensile strengths of tested steels all exceeded 1000 MPa, and their elongation was also greater than 18.7%, resulting in overall mechanical properties superior to those of conventional quenching and partitioning (Q&P) steels. The Dictra calculation results suggest that high-temperature partitioning treatment can only ensure the volume fraction and carbon content of austenite in the ‘upper critical zone’ of the two-phase zone. After low-temperature partitioning treatment, more residual austenite can be preserved at room temperature, ultimately enhancing the strength and plasticity of tested steel.