HIGH STRENGTH HOT ROLLED STEEL PLATE EXCELLENT IN UPSET BUTT WELDABILITY AND FORMABILITY, PRODUCED BY CONTINUOUS HOT ROLLING PROCESS, AND ITS PRODUCTION

• Main Authors: WAKITA JUNICHI, KONO OSAMU, MIYAZAKI YASUNOBU, MIZUI MASAYA, SUGI KOJI, TAKAHASHI MANABU, IKENAGA NORIO
• Format: Patent
• Language: English
• Published: 17.06.1997
• Edition: 6
• 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

PROBLEM TO BE SOLVED: To secure the uniformity of material in the same coil by producing a steel plate of specific composition by a continuous hot rolling process and providing specific properties. SOLUTION: The composition of the steel plate is regulated so that it consists of, by weight, 0.07-0.12% C, 0.1-0.6% Si, >2.0-2.5% Mn, <=0.02% P, <=0.01% S, 0.004-0.05% Al, 0.025-0.06% Nb, >0.10-0.15% Ti, and the balance Fe with inevitable impurities. The steel is heated to >=1230 deg.C, and, in the continuous hot rolling process, the temp. in a finish rolling mill is regulated to Ar3 to 900 deg.C and the resultant plate is coiled at 500-690 deg.C. By this procedure, a fine- grained ferrite structure having <=5μm average grain size in an as-rolled state is formed. Moreover, tensile strength and the product of TS and uniform elongation are regulated to >=780N/mm and 10000N/mm .%, respectively, and further, the fluctuation of TS in the coil is regulated to <100N/mm . By this method, the amount of discard of the head and the tail end of the steel plate can be reduced, and also yield can be improved.