The Effects of Nitrogen Addition on the Production of Ultrafine/Nano Grained AISI ۲۰۱L Stainless Steel by Advanced Thermo-mechanical Process

In this study, the effects of nitrogen addition on the production of ultrafine/nano grained AISI ۲۰۱L stainless steel by advanced thermo-mechanical process were investigated. Cast samples were first homogenized at ۱۲۰۰ °C for ۴ h, hot-rolled at ۱۱۰۰ °C and finally, solution-annealed at ۱۱۵۰ °C for ۲.۵ h. Unidirectional and cross multipass cold rolling at ۲۵ °C was carried out to ۹۰% reduction in thickness, followed by annealing at temperature and time range of ۸۰۰–۹۰۰ °C and ۱۵–۱۸۰۰ s, respectively. The results showed that increasing nitrogen led to the decrease of delta ferrite content and austenite grain size after solution annealing. It was also found that decreasing nitrogen content and using cross rolling resulted in an increased volume fraction of the strain induced martensite (SIM) and reduced saturation strain of martensite formation during cold rolling. Also, the results from the reversion process revealed that with increasing nitrogen concentration, the formation of thermally induced martensite was suppressed.

Keywords:

Martensite thermomechanical processing , Nitrogen , ۲۰۱L stainless steel , Cold rolling , Reversion annealing