5th International High Manganese Steel Conference - HMNS 2022

In this work, it was shown that quenching and partitioning (Q&P) processing can be applied to interstitial alloyed CrMnNi austenitic steels capable of martensitic transformation during cryogenic cooling. With the aid of Q&P, ultra-high strength properties can be achieved with exceptional elongation even in the as-cast state. In the present study, the alloy Fe-15Cr-3Mn-3Ni-0.16C-0.12N (concentrations in wt.%) was used in the cast condition to demonstrate its excellent suitability for Q&P. The solution annealed steel was quenched to -120 °C to produce about 44 vol.% α´-martensite in the austenitic steel matrix. Subsequently, partitioning was carried out at 450 °C for various partitioning times (Pts), namely 3, 15 and 30 min. The austenite lattice parameter was found to increase slightly with increasing Pt from 3 min to 30 min., proving the enrichment of C and N in the austenite. After the Q&P processing, tensile tests with an initial strain rate of approximately 4 × 10-4 s-1 were performed on round type tensile specimens until fracture. The steel partitioned for 3 min achieved an ultimate tensile strength (UTS) of 1470 MPa accompanied by a total elongation (TE) of 32% at room temperature. As the partitioning time increases to 30 min, the tensile strength decreases only slightly, whereas the very good deformability can be maintained. The experimental results show that almost constant mechanical properties can be produced even if the partitioning time is varied over a wide range. In addition, the Q&P-treated cast steel met the US Department of Energy's 2017 proposed criteria for wrought 3rd generation Advanced High Strength steels (AHSSs) (UTS ≥ 1200 MPa, TE ≥ 30%).