SAE 1541鋼の遅れ破壊特性および機械的性質に及ぼすS, Pの影響

概要

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Cr-Mo type steel like JIS SCM 440H is currently used for high strength bolts heat treated to the strength of 120 to 140kgf/mm2. Lower alloy steels such as boron treated steel or manganese steel had not been substituted for SCM 440H so far because of high susceptibility of delayed fracture.In accordance with these circumstances, this study has been made to clarify the effect of impurities such as sulphur and phosphorus on the delayed fracture resistance and other mechanical properties.As a result, it has been confirmed that manganese steel SAE 1541 shows markedly improved delayed fracture resistance which is equivalent to that of SCM 440H by reducing the sulphur and phosphorus contents less than 0.005 and 0.015% respectively. Furthermore, the toughness of this clean steel is also remarkably improved. These advancements of clean 1541 steel are considered due to the suppression of impurities segregation along the prior austenite grain boundaries and the reduction of non-metallic inclusion, MnS.
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