METHOD OF MANUFACTURING A DUPLEX STEEL SHEET HAVING ENHANCED FORMABILITY

摘要

The invention relates to a method of manufacturing a duplex steel sheet having a microstructure comprising 10 - 50 vol.% ferrite in an austenite matrix, and having a steel composition, in wt.%, Mn: 5-30% Al: 3-12% C: 0.3-1.0% inevitable impurities: <0.1% the remainder being iron provided that %AI/%Mn <=%C, and the process comprising the steps of: a) casting an ingot from the composition; b) heating the cast ingot to a temperature above 1050 °C; c) hot rolling the heated cast ingot to obtain a hot rolled strip having a reduced thickness; d) quenching the hot rolled strip from the final hot rolling temperature (FRT) at a rate of at least 75 °C/second to a temperature below 200 °C; e) pickling the quenched strip, f) cold rolling the pickled strip to a sheet having a further reduced thickness; g) annealing the sheet having a further reduced thickness at a temperature in the range of 700-1200°C for a period of time of 0.5-8 minutes; h) quenching the annealed sheet from the annealing temperature at a rate of at least 75 °C/second to a temperature below 200 °C.