Abstract:
A cold rolled and coated steel sheet having a composition including of the following elements, expressed in percentage by weight: 0.140%≤Carbon≤0.2%, 1.5%≤Manganese≤2.15%, 0.5%≤Silicon≤0.8%, 0.4%≤Aluminum≤0.8%, 0%≤Phosphorus≤0.09%, 0%≤Sulfur≤0.09%, 0%≤Nitrogen≤0.09%, 0.01%≤Niobium≤0.1%, 0.01%≤Titanium≤0.1%, and can contain one or more of the following optional elements 0%≤Chromium≤0.1%, 0%≤Nickel≤0%, 0%≤Calcium≤0.005%, 0%≤Copper≤2%, 0%≤Molybdenum≤0.5%, 0%≤Vanadium≤0.1%, 0%≤Boron≤0.003%, 0%≤Cerium≤0.1%, 0%≤Magnesium≤0.010%, 0%≤Zirconium≤0.010% the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet including in area fraction, 40 to 60% Inter-critical Ferrite, 25 to 45% Transformed Ferrite, 8% to 20% and 5% to 20% Fresh Martensite, 0 to 10% Bainite, wherein the cumulated amount of Inter-critical and Transformed Ferrite is between 75% and 85%.