Effect of Controlled Rolling on the Strength and Toughness of Low-Alloy Martensitic Steel

Low-carbon martensitic steel is the key material of automobile lightweight. Unfortunately, the strategies for increasing the material strength, such as processing to create line defects (dislocations), tend to decrease the ductility. Herein, a strategy to circumvent this problem in an inexpensive, microalloy low-carbon (0.32%) martensitic steel by regulating the accelerated cooling stop temperature after hot rolling is developed. Steel with fine austenite grains embedded in a highly dislocated martensite matrix is developed by cold rolling followed by saltwater quenching and low-temperature tempering. This deformed process produces dislocation hardening, but retains high ductility both through the glide of intensive mobile dislocations. The proposed strategy provides a pathway for the development of high-strength, high-ductility materials. The original austenitic grains of low-carbon martensitic steel by adjusting the rolling structure are studied, which result in more reversed austenite being retained in the slat boundary; in addition, more mobile dislocations in the fine grains show good mechanical properties.image (c) 2024 WILEY-VCH GmbH