STEEL FOR BOLTS AND BOLT

• Main Authors: UCHIDA TATSUNORI, KOCHI TAKUYA
• Format: Patent
• Language: English; Japanese
• Published: 28.06.2022
• 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

To provide a steel for bolts that shows sufficient resistance to delayed fracture even with a tensile strength of 1600 MPa or more after quenched and tempered.SOLUTION: A steel for bolts is composed of C: 0.35 mass% to 0.50 mass%, Si: 1.52 mass% to 2.50 mass%, Mn: 0.10 mass% to 0.40 mass%, P: more than 0 mass% to 0.015 mass% or less, S: more than 0 mass% to 0.010 mass% or less, Cu: 0.11 mass% to 0.50 mass%, Ni: 0.11 mass% to 1.0 mass%, Cr: 0.1 mass% to 2.4 mass%, Ti: 0.05 mass% to 0.19 mass%, Al: more than 0 mass% to 0.10 mass% or less, B: 0.0003 mass% to 0.01 mass%, N: more than 0 mass% to 0.015 mass% or less, with the balance being iron and unavoidable impurities. After quenched and tempered, the steel for bolts has a tensile strength of 1600 MPa or more.SELECTED DRAWING: None 【課題】調質後に、引張強度が１６００ＭＰａ以上であっても十分な耐遅れ破壊特性を示すボルト用鋼を提供する。【解決手段】成分組成が、Ｃ：０．３５～０．５０質量％、Ｓｉ：１．５２～２．５０質量％、Ｍｎ：０．１０～０．４０質量％、Ｐ：０質量％超０．０１５質量％以下、Ｓ：０質量％超０．０１０質量％以下、Ｃｕ：０．１１～０．５０質量％、Ｎｉ：０．１１～１．０質量％、Ｃｒ：０．１～２．４質量％、Ｔｉ：０．０５～０．１９質量％、Ａｌ：０質量％超０．１０質量％以下、Ｂ：０．０００３～０．０１質量％、Ｎ：０質量％超０．０１５質量％以下、および残部：鉄および不可避不純物からなり、調質後の引張強度が１６００ＭＰａ以上であるボルト用鋼。【選択図】なし