Effect of Hot-Deformation Processes on Phase Transformation of Low-Alloyed, Multiphase, High-Strength Steel

Low-alloyed, multiphase, high-strength steels are strong and tough with good weldabilities and high cost-to-performance ratios. They have long-term research value and broad application prospects. However, there are many types of phase transformations and complicated transformation processes that occur in these steels, which must be studied in detail. Understanding the phase transformations and their relationships to the mechanical properties of steels can theoretically facilitate material property enhancement and support the application and production of such steels. Herein, a Gleeble-3800 thermosimulation test system is used to simulate the rolling process with different hot-rolling process parameters. The effects of various parameters, such as the deformation, temperature, and velocity, on the phase-transformation process and microstructural characteristics of low-alloyed, multiphase, high-strength steel are studied under hot deformation and subsequent cooling. The results show that low-alloyed, multiphase, high-strength steels generally undergo multiple types of phase transformations in a fixed order. The conditions during hot deformation have a critical influence on the phase transformation, i.e., they change the order of the phase transformations by promoting or suppressing certain phase-transformation types. This causes different phase-transformation types to predominate and results in different steel microstructures.