Excellent austenitic lightweight high-strength steel sheet and a method of manufacturing the same in yield ratio and ductility

摘要

The present invention relates to an austenitic, lightweight, high-strength steel sheet having a high yield ratio and ductility and a method for producing the same, and more particularly, to a high-strength steel sheet for automotive interior panels, exterior panels, and structural parts, and a method for producing the steel sheet. An aspect of the present invention provides austenitic, lightweight, high-strength hot rolled steel sheet , cold rolled steel sheet and coated steel sheet having a high yield ratio and ductility and a method for producing thereof including appropriate concentrations of alloying elements such as Mn, Si, and Al to obtain a tensile strength of 800 MPa or greater, an elongation of 30% or greater, and a yield ratio of 60% or greater that are difficult to obtain from high-carbon, high-manganese steel sheets or high-manganese, lightweight steel sheets of the related art. The present invention provides a steel sheet having a low specific gravity, a high yield ratio, and high ductility as compared to high-strength steel sheets of the related art such as advanced high strength steels (AHSS). The steel sheet of the present invention is effective in maintaining the rigidity of a structural member and have good press processing characteristics so that the steel sheet can be used for manufacturing automotive parts to reduce the weight of automobiles and combining a plurality of parts into a single module or as one part to simplify machining or assembly processes.