The Effects of Nitrogen Addition on the Production of Ultrafine/Nano Grained AISI 20IL Stainless Steel by Advanced Thermo-mechanical Process

In this study, the effects of nitrogen addition on the production of ultrafine/nano grained AISI 201L stainlesssteel by advanced thermo-mechanical process were investigated. Cast samples were first homogenized at 1200 °C for 4 h, hot-rolled at 1100 °C and finally, solution-annealed at 1150 °C for 2.5 h. Unidirectional and cross multipass cold rolling at 25 °C was carried out to 90% reduction in thickness, followed by annealing at temperature and time range of 800–900 °C and 15–1800 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.