Kinetics of Carbon Partitioning during Non‐Isothermal Treatment and Mechanical Properties of the First Industrial Coils of Hot Rolled Quenched and Partitioned Steel

Abstract

In this study, an energy‐efficient processing route involving hot rolling, direct quenching, and air cooling partitioning (DQ&P) is proposed for the large‐scale industrial production. The carbon partitioning is completed through waste heat of the steel coils. The effect of quenching temperature (QT) and the kinetics of non‐isothermal carbon partitioning were investigated in a low carbon steel 0.19C‐1.5Si‐1.6Mn (wt%). A stable volume fraction of retained austenite (RA) ≈11.1–13.5% is obtained in the QT range of ≈240–360 °C, which provides a wide quenching window for industrial production. In addition, when the QT was 320 °C, the carbon partitioning was adequate at cooing rate of less than 1 °C s−1 and the volume fraction of RA was more than 11%. When the cooling rate is increased to 5 and 10 °C s−1, ≈10% RA with high carbon content of ≈1.3 wt% is interestingly obtained. A large scale industrial coils of hot Q&P (Quenched and Partitioned) steel is successfully produced using a commercial steel 0.13C‐1.2Si‐1.5Mn‐0.25Cr (wt%). The mechanical properties are uniform for the entire steel coil with tensile strength of ≈1258–1319 MPa and total elongation of ≈13.7–16%. The present work confirms the viability to introduce Q&P process in the hot rolling production line.