HIGH STRENGTH STEEL SHEET AND MANUFACTURING METHOD THEREFOR

• Main Authors: KIZU TARO, TOYODA SHUNSUKE, KIDO AKIMASA, TADANI TETSUSHI
• Format: Patent
• Language: Chinese; English
• Published: 28.11.2017
• Subjects: ALLOYS; CHEMISTRY; FERROUS OR NON-FERROUS ALLOYS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUSMETALS OR ALLOYS; MAKING METAL MALLEABLE BY DECARBURISATION, TEMPERING OR OTHERTREATMENTS; METALLURGY; METALLURGY OF IRON; MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; TREATMENT OF ALLOYS OR NON-FERROUS METALS

The purpose of the present invention is to provide: a high strength steel sheet that has high strength such that tensile strength is at least 780 MPa, and excellent blanking quality combined with stretch-flangeability; and a manufacturing method therefor. Provided is a high strength steel sheet wherein: the steel sheet contains, in mass%, C: 0.05-0.30%, Si: 0.6-2.0%, Mn 1.3-3.0%, P: not more than 0.10%, S: not more than 0.030%, Al: not more than 2.0%, N: not more than 0.010%, and one or more of Ti, Nb and V: 0.01-1.0% each, the balance being obtained from iron and unavoidable impurities; the steel sheet comprises at least 50% area ratio of ferrite structure; the amount of Fe deposited is at least 0.04 mass%; the steel sheet contains a deposit in which the particle diameter is less than 20 nm; and C* defined by expression (1) and C*p defined by expression (2) satisfy the conditions in expressions (3)-(5). C*=([Ti]/48+[Nb]/93+[V]/51+[Mo]/96+[Ta]/181+[W]/184) * 12... (1) C*p=([Ti]p/48+[Nb]p/93+[V]p/51+[Mo]p/96+[