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HIGH STRENGTH STEEL AND HIGH STRENGTH BOLT EXCELLENT IN DELAYED FRACTURE RESISTANCE AND METHODS OF PRODUCTION OF SAME
HIGH STRENGTH STEEL AND HIGH STRENGTH BOLT EXCELLENT IN DELAYED FRACTURE RESISTANCE AND METHODS OF PRODUCTION OF SAME
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机译:高强度钢和高强度螺栓具有出色的抗断裂断裂性能和相同的生产方法
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摘要
A steel which is excellent in delayed fracture resistance containing, by mass %, C: 0.10 to 0.55%, Si: 0.01 to 3%, and Mn: 0.1 to 2%, further containing one or more of Cr: 0.05 to 1.5%, V: 0.05 to 0.2%, Mo: 0.05 to 0.4%, Nb: 0.001 to 0.05%, Cu: 0.01 to 4%, Ni: 0.01 to 4%, and B: 0.0001 to 0.005%, and having a balance of Fe and unavoidable impurities, the structure being a mainly tempered martensite structure, the surface of the steel being formed with (a) a nitrided layer having a certain thickness range and a nitrogen concentration higher than the nitrogen concentration of the steel by 0.02 mass % or more and (b) a low carbon region having a certain depth range from the surface of the steel and having a carbon concentration of 0.9 time or less the carbon concentration of the steel.
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