HIGH-STRENGTH STEEL HAVING HIGH YIELD RATIO AND EXCELLENT DURABILITY, AND METHOD FOR PRODUCING SAME

• Main Authors: NA, Hyun-Taek, KIM, Sung-Il
• Format: Patent
• Language: English; French; German
• Published: 14.09.2022
• 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

Thick high-strength steel having a high yield ratio and excellent durability, and a method for manufacturing same are provided.Thick high-strength steel having a high yield ratio and excellent durability, and a method for manufacturing same are provided. The thick high-strength steel having a high yield ratio and excellent durability of the present invention comprises, in percentage by weight: C: 0.05-0.15%; Si: 0.01-1.0%; Mn: 1.0-2.3%; Al: 0.01-0.1%; Cr: 0.005-1.0%; P: 0.001-0.05%; S: 0.001-0.01%; N: 0.001-0.01%; Nb: 0.005-0.07%; Ti: 0.005-0.11%; and Fe and unavoidable impurities, and has a microstructure comprising, in percentage by area: less than 5% of a pearlite phase; less than 10% of a bainite phase; and less than 5% of a martensite and austenite (MA) phase; and the remaining of a ferrite phase, and including nitrides and coarse carbides having a diameter of 1 µm or more, wherein the ratio of fatigue limit and yield strength is 0.15 or more and the yield ratio is 0.8 or more.