Tough Ductile Ultra High Strength Steels Through Direct Quenching and Partitioning—An Update
The TMR-DQP* processing route comprising thermomechanical rolling followed by direct quenching and partitioning, has shown huge potential for the development of tough, ductile ultra-high-strength steels, both for structural and wear-resistant applications. The approach comprised designing suitable chemical compositions, establishing appropriate DQP processing conditions with the aid of physical simulation, and finally testing laboratory rolled DQP material with the emphasis on cost-effective process development, amenable for industrial hot strip production. Evaluation of DQP processed samples cooled slowly following DQP processing, thus simulating coiling, confirmed achieving the desired martensite-austenite microstructures and targeted mechanical properties. Ausforming in no-recrystallization regime (Tnr) resulted in extensive refining and randomization of the martensite packets/laths besides fine division of interlath austenite, thus resulting in an all-round improvement of mechanical properties. Preliminary investigations on alloys designed with 0.2 C have shown promising properties not only for structural applications, but also wear-resistance purposes.
KeywordsDirect quenching and partitioning Thermomechanical processing Martensite Bainite Austenite
The work was carried out under the auspices of Light and Efficient Solutions Program of FIMECC (Finnish Metals and Engineering Competence Cluster) Ltd. The authors gratefully acknowledge the financial support from Tekes (Finnish Funding Agency for Technology and Innovation) and SSAB Europe Oy (formerly, Rautaruukki Oyj).
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