Study on process for manufacturing billets of a high strength and good ductility TRIP steel

Abstract

Transformation induced plasticity (TRIP) steel is a grade of advanced
high strength steels (AHSS). The steel has a multiphase
microstructure of ferrite, bainite, martensite and retained austenite
with a certain volume fraction and extrafine grain size of phases, in
which, grain size of ferrite is less finer than 15µm. This paper shows
studied results of making a TRIP steel with high strength and good
ductility which exceeds those of HSLA steels in same chemical
composition. The sponge iron melted-TRIP steel has low level of
impurities, forged and rolled, then, heat treated in inter-critical
temperature that has two phases (ferrite and austenite) and
isothermal-cooled in bainitic temperature to generate the
transformation of austenite to bainite. The study has created the steel
with ultimate tensile strength over 800 MPa and elongation over 30%
through creating a desired multiphase microstructure. The process
was experimentally confirmed and can be used for building
processing procedures to make billets for manufacturing high forcedparts of cars and weapon.