Yûnoshin Imai and Hikotarô Imai
Following the preceding two papers, this paper describes the results of mechanical tests on several series of 0.15 ∼ 0.20% C, 1.0% Cr, 0.3 ∼ 0.7% Cu-steels containing boron, tested in normalized or hardened and tempered conditions. In the normalized condition, all these series of steels did not show any effects of boron-addition. But in the hardened and tempered condition of several steels, such as condaining 0.15 ∼ 0.20% C, 1.0% Cr, 0.3 ∼ 0.5% Cu, boron is revealed as a very useful element; i.e., the max. and yield stresses are enhanced in the degree of 15 ∼ 25 kg/mm2, the reduction of area and the elongation are not decreased, only the results on impact tests indicate slight decrease, but their values are rather high in view of their high max. and yield stresses. Mn-additions, in the order of 0.5 ∼ 2.0%, to these steels, are not so effective in either the normalized or the heat-treated condition. In the carburizing tests of these steels, the results also indicated very desirable features. From the results above mentioned, these steels are more suitable as structual low-alloy steels, or as the carburizing steels, than low-grade Ni-Cr steels.
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