High-strength austenitic stainless steel strip having excellent flatness and method of manufacturing same

A method of manufacturing a high-strength austenitic stainless steel strip excellent in flatness of shape with Vickers hardness of 400 or more, which comprises the steps of:

• providing an austenitic stainless steel strip having a composition comprising C up to 0.20 mass %, Si up to 4.0 mass %, Mn up to 5.0 mass %, 4.0-12.0 mass % Ni, 12.0-20.0 mass % Cr, 0.24-5.0 mass % Mo, N up to 0.15 mass %, optionally at least one or more of Cu up to 3.0 mass %, Ti up to 0.5 mass %, Nb up to 0.50 mass %, Al up to 0.2 mass %, B up to 0.015 mass %, REM (rare earth metals) up to 0.2 mass %, Y up to 0.2 mass %, Ca up to 0.1 mass % and Mg up to 0.10 mass %, and the balance being Fe except inevitable impurities under the condition that a value Md(N) is 0-125 defined by a formula:
• Md(N)=580-520C-2Si-16Mn-16Cr-23Ni-26Cu-300N-10Mo;
• solution-heating said austenitic stainless steel strip;
• cold-rolling said austenitic stainless steel strip to generate a deformation-induced martensite phase;
• and
• re-heating said cold-rolled austenitic stainless steel strip at 500-700° C. to induce a phase reversion, by which an austenitic phase is generated at a ratio of 3 vol. % or more in a matrix composed of said deformation-induced martensite phase.