(p694) Development of an air hardened forging steel with medium manganese content

摘要

The design and development of a new air hardened martensitic steel grade (LHD) which combines the mechanicalproperties of quenched and tempered (QT) steels with the short process chain of a precipitation hardened ferriticpearlitic(PHFP) steel is presented in this paper. The martensitic hardening after a slow cooling on air is attainedwith addition of 4 wt% manganese and micro alloying of 30 ppm boron and 330 ppm titanium. First investigationson laboratory scale reveal a martensitic hardening with t8/5 < 2180 s. The yield and tensile strengths of this newlydeveloped steel are approximately 900 MPa and 1,500 MPa, respectively. Despite the high strength the elongationshows values of about 12 %. It is demonstrated that the LHD steel has a broad process window for achieving therequested tensile properties. This characteristic is suitable for forged components with varying cross sections andtherefore different cooling conditions.