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.
Highlights
In recent years, advanced high strength steels (AHSSs) have been in development for automotive applications [1,2,3,4]
The experimental material was prepared by a ~100 kg vacuum induction melted (VIM) ingot hot-rolled from 100 mm to 6 mm in thickness with a starting temperature of 1150 ◦ C and finishing temperature of 900 ◦ C, which was annealed at 680 ◦ C for 4 h and cold-rolled to 1.5 mm in thickness
The results show that treatment can make the supersaturated carbon element in martensite diffuse results show that quenching and partitioning (Q-P) treatment can make the supersaturated carbon element in martensite diffuse into the untransformed austenite and increase stability.itsTherefore, untransformed into thesurrounding surrounding untransformed austenite and its increase stability.theTherefore, the austenite changes into retained austenite at room temperature
Summary
In recent years, advanced high strength steels (AHSSs) have been in development for automotive applications [1,2,3,4]. AHSSs require a good combination of strength and ductility to meet the weight reduction, reduced fuel consumption and CO2 emission, and passenger safety requirements [2,5]. Some efforts have been contributed to the replacement of galvanized AHSS by stainless steels for vehicle body applications (austenitic, ferritic-austenitic, and ferritic stainless steel) [17,18,19,20,21]. Austenitic and ferritic-austenitic stainless steels have superior corrosion resistance, their applications are limited by relatively high
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