LOW YIELD RATIO STEEL PRODUCTS EXCELLENT IN UNIFORM ELONGATION

• Main Authors: TAKEI MASAMITSU, SUJITA YASUTOSHI
• Format: Patent
• Language: English
• Published: 30.04.2004
• Edition: 7
• 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 provide the high strength, high uniform elongation and low yield ratio steel products which can absorb a large amount of earthquake energy, and resist to thermal softening induced by temperature rising, and shows less degradation after welding such as spot welding. SOLUTION: The steel products contain 0.15-0.40mass% C and 0.8-2.0mass% Si, and further ≥0.50mass% (Cr+Mo+V+Nb), and the steel products are hot-rolled, and variant worked to form a projection or a hollow almost uniformly over full length of the steel products in a finishing process, and cooled at a cooling rate of at least 0.3°C/s and not more than 15°C/s to form a bainite structure, the steel products exhibit tensile strength of not more than 1,650N/mm2, yield strength of at least 930N/mm2, yield ratio of not more than 85% and uniform elongation of at least 5%. COPYRIGHT: (C)2004,JPO