Yûnoshin Imai and Hikotarô Imai
This paper describes the results of mechanical tests on several series of low-carbon (0.05 ∼ 0.08%), low-alloy (0.3 ∼ 0.5% Mo) steels containing boron (0.003%), tested in a hardened-tempered condition. Like the results of tests under normalized condition, in a 550°-tempered condition, the mechanical properties of these types of steels are improved markedly by addition of boron, the max. stress rising from 55 kg/mm2 to 75 ∼ 85 kg/mm2 and the yield stress, from 40 kg/mm2 to 70 ∼ 80 kg/mm2. The reduction of area or impact values are not effected so much; the former remaining at 55 ∼ 65% and the latter showing the considerably high values of 7.5 ∼ 12.0 kg · m/cm2. The elongation is slightly decreased from 30% to 20 ∼ 25%. An addition of Mn or Cr, in the order of 1.0% or an increase of carbon-content up to 0.2%, are very effective to raise their strength much as in samples prepared under normalized condition.
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