FUNAKAWA Yoshimasa FUJITA Takeshi YAMADA Katsumi
NANOHITENTM in 780 MPa grade of tensile strength has achieved excellent stretch flange formability as the same level of 440 MPa grade with ferrite grains strengthened by nanometer-sized carbides. Uniform fine carbides in NANOHITENTM are dispersed into ferrite grains by interphase-precipitation phenomena. The diameter of the fine carbides became 1/10 compared with the conventional TiC, and the amount of precipitation-strengthening increased to 300 MPa. Since fine carbides in NANOHITENTM are hardly coarsened, NANOHITENTM is suitable to warm stamping. Experimental results of warm stamping indicated that warm stamped NANOHITENTM with 980 MPa grade showed good formability at the same level of cold stamped high strength steel with 590 MPa grade.