Double phase stainless steel strip for steel belt

Abstract

A high-strength dual-phase stainless steel strip has a chemical composition consisting of 0.04-0.15 mass % C, 10.0-20.0 mass % Cr, 0.5-4.0 mass % Ni and the balance being Fe except inevitable impurities, and a metallurgical structure composed of 20-85 vol. % martensite grains and the balance ferrite grains with prior austenite grains controlled to 10 μm or less in size. The stainless steel strip is conditioned to hardness of HV 300 or more. Transformation strains are uniformly distributed in a steel matrix during martensitic transformation, so that the steel strip is formed and straightened to a belt shape without Lüders band. Consequently, steel belts with fine external appearance are manufactured from the stainless steel strip.

1 . A dual-phase stainless steel strip for use as steel belts, which has: 
 a chemical composition consisting of 0.04-0.15 mass % C, 10.0-20.0 mass % Cr, 0.5-4.0 mass % Ni and the balance being Fe except inevitable impurities,    a transformed structure composed of 20-85 vol. % martensite grains and the balance being ferrite grains with prior austenite grains controlled to 10 μm or less in size, and    hardness of HV 300 or more. cm  2 . The dual-phase stainless steel strip defined by  claim 1 , wherein the chemical composition further contains one or more of Si up to 2.0 mass %, Mn up to 2.0 mass %, not more than 0.050 mass % of P, not more than 0.020 mass % of S, 0-0.10 mass % of Al, 0-0.10 mass % of N, 0-1.0 mass % of Mo, 0-2.0 mass % of Cu, 0.01-0.50 mass % of Ti, 0.01-0.50 mass % of Nb, 0.01-0.30 mass % of V, 0.01-0.30 mass % of Zr, 0.0010-0.0100 mass % of B, 0-0.02 mass % of Y, 0-0.05 mass % of Ca. and 0-0.1 mass % of REM (rare earth metals). cm  3 . The dual-phase stainless steel strip defined by  claim 1  or  2 , wherein an expansion rate during martensitic transformation of austenite is controlled to 9% or less in average.