MANUFACTURE OF SUPER 100KGF/MM2 CLASS HOT-ROLLED STEEL PLATE WITH SUPERIOR WORKABILITY

• Main Authors: SHITAMACHI TAKASHI, HONDA TOMOKI, NAKAMURA MAKOTO, ITAMI ATSUSHI, KOYAMA KAZUO
• Format: Patent
• Language: English
• Published: 29.08.1987
• 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

PURPOSE:To obtain a super 100kgf/mm class hot-rolled steel plate with superior workability markedly improved in stretch-flange formabilities and bendability, by forming the structure after rolling into uniform bainite by combining special hot rolling conditions in a simple C-Si-Mn steel. CONSTITUTION:The steel has a composition containing, by weight, 0.15-0.30% C, 0.5-1.7% Si, >2.0%-2.5% Mn, <=0.01% P, <=50ppm S, and 0.01-0.1% Al, satisfying Eq=6C+1.2Si+Mn>=3.5, and further containing, if necessary, <=50ppm Ca. This steel is treated so that its finish rolling is finished at Ar3+50 deg.C-Ar3+150 deg.C. The finish-rolled steel plate is cooled within two seconds from the temp. region higher than Ar3 to 400-550 deg.C at <10-80 deg.C/sec cooling rate and then wound up. In this way, the titled hot-rolled steel plate remarkably excellent, as compared with conventional one, in stretch-flange formabilities and bendability which are important workabilities required of high-strength members for automobile use can be obtained.