含硼素強靱鋼に關する研究 (II)

概要

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In sequence of to the former report, the effect of boron addition on mechanical properties of constructional alloy steels in different conditions of heat treatment were studied. Results obtained were summarized as follows. 1. Proper Al-Ti-B treatment gave favourable effect on notch toughness when the steel was completely hardened and tempered at temperatures lower than 400℃, but if excess addition of boron was made, some adverse effect appeared at higher tempering temperatures. 2. In the case of incompletely hardened and tempered states, if the microstructure of as-hardened specimen consisted of martensite and bainite, boron gave benefical effact on strength and toughness because it increased the percentage of martensite, but if hardening was so unsuffi-cient that there appeared proeutectoid ferrite and pearlite at the grain boundary with smaller percentage of martensite, slight decrease in notch-toughness occurred as well as in fully annealed states. 3. Also effects of intermediate transformations by austempering on the mechanical properties and low temperature notch-toughness were studied.
1953-07-25