Microstructures and Properties of a Low-Carbon-Chromium Ferritic Stainless Steel Treated by a Quenching and Partitioning Process

Abstract

Low chromium ferritic stainless steel has great potential in automobile structures for improved strength. In this study, quenching and partitioning (Q-P) treatment was applied to a low-carbon-chromium ferritic stainless steel and compared with traditional heat treatment (quenching-tempering [Q-T] and annealing) in terms of microstructure, mechanical properties, corrosion resistance, and deformation of plate. The results show that the quenching and partitioning (Q-P) treatment has a series of advantages over conventional heat treatments (quenching-tempering and annealing). In terms of mechanical properties, it achieves a good match between strength and plasticity by combining the advantages of “soft state” with high elongation resulting from conventional annealing and high strength "hard state” through the traditional quenching-tempering process. The material possesses better crash safety; for the quenching-partitioning (Q-P) process, quenching-tempering process, and annealing process, the production of strength plasticity is about 16 GPa%, 15 GPa%, and 14 GPa%, respectively. The material has low yield strength, high work hardening index (compared with Q-T), a smooth tensile curve, and no yield plateau (compared with annealing), so it has better forming performance and processing surface, and the corrosion resistance has also improved. The pitting potential of the samples produced by the quenching treatment of Q-P and Q-T increased by about 0.2 V, which is about 20% higher than the one by the traditional annealing process.

Microstructure development of quenching and partitioning-processed martensitic stainless steels with different manganese content

“…In earlier studies focused on stainless steels, researchers noted the presence of M 23 C 6 -type Cr-carbides in ferritic stainless steels after undergoing the Q&P treatment. 32,33 However, a key question remains unanswered: whether these carbides formed during the initial quenching 27 or during the subsequent partitioning step. In contrast, when examining Q&P-treated martensitic stainless steels in prior research, [17][18][19][20][21]34 investigators consistently detected M 3 C and M 7 C 3 carbides within the martensitic structure, but there was no evidence of M 23 C 6 carbides in any of the studies conducted.…”