THERMOMECHANICAL PROCESSING OF ADVANCED HIGH STRENGTH STEELS IN PRODUCTION HOT STRIP ROLLING

Hot strip rolling of low carbon Advanced High Strength Sheet Steels (AHSS) is challenging due to non-traditionalchemical compositions required to attain the unique mechanical properties in AHSS products. In hotstrip rolling, TMP implies various types of controlled rolling where temperature, strain rate and rollingreductions are carefully selected to produce the target austenite microstructure, which is either fullyrecrystallized or fully pancaked austenite before starting cooling. Microalloying of HSLA in combinationwith suitable TMP provides an efficient tool to control austenite recrystallization prior to the beginningof cooling. However, the existing TMP routes cannot be easily applied to AHSS that have much more sophisticatedalloying and lower level of microalloying. TMP of AHSS in the finishing train of hot strip mill shouldbe designed so as to ensure controlled type and extent of transformation on run-out table by precise control ofstrip temperature and rolling speed with account for mill configuration and capabilities, product dimensions,gauge and shape tolerances. Further complications can be brought about by high sensitivity ofAHSS to various aspects of hot strip rolling and cooling parameters. These aspects are discussed in the paperalong with various practical implications