低温焼もどしを施した 0.35%C-B 鋼の破壊靱性への B と N の影響

概要

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Effects of boron, nitrogen, and controlling factors on fracture toughness K_<IC> of boron-treated 0.35%C steels tempered at low temperature were investigated. 1) K_<IC> linearly increased with a value of β=34.0 B-13.3N, where B and N are boron and nitrogen contents (wtppm), respectively. Aluminium content gave little effect on K_<IC>. 2) Concentrations of boron and nitrogen in solution in austenite in equilibrium with BN and Fe_2B were calculated from solubility products in the iron-boron-nitrogen systems. 3) High content or concentration in solution of boron resulted in higher K_<IC> because of suppression of both decohesion at inclusion-matrix interface and intergranular fracture. Quasi-cleavage like cracks were observed in steels having high content or concentration in solution of nitrogen, and K_<IC> was reduced. However, effect of nitrogen on K_<IC> was less than that of boron. 4) Optimum amounts of boron and nitrogen required for high K_<IC> were found from the iron-boron-nitrogen equilibrium phase diagram.
社団法人日本鉄鋼協会の論文
1983-02-01