In this study, production of nanostructure 301 austenitic stainless steel by cold rolling-annealing thermomechanical process is investigated. In used steel, austenite transforms to strain induced martensite by cold rolling. Reversion of strain induced martensite to austenite in subsequent annealing leds to formation of ultra fine grain austenitic structure. For this purpose, annealing parameters of cold rolled 301 stainless steel was studied to produce a nanostructured austenite. Phase transformations, was studied by means of XRD, feritscope and dilatometer, also microstructures was observed by means of optic and scanning electron microscopes. Results showed that by 60% cold roll after quenching at -10°C, all of the austenite was transformed to strain induced martensite. Annealing of the 90% cold rolled 301 stainless steel at temperatures above 700°C showed a decrease followed by an increase of the martensite volume fraction. Increase of the martensite content after annealing was related to carbide precipitation, matrix carbon depletion and increasing of M s temperature above room temperature, causing thermally-induced martensite formation during cooling. The sample annealed at 800°C for 10 s exhibited the smallest average austenite grain size of 240 nm with almost fully austenitic structure. Tension test results for samples before and after thermomechanical process, showed a noticeable increase in yield strength from 452 MPa to 966 Mpa and tensile strength from 815 Mpa to 1470 Mpa after process. Keywords Martensite reversion, Nano/submicron grain structure, Austenitic stainless steels, Thermomechanical treatment.
