Abstract
Following the preceding papers, this paper describes the results of mechanical tests on several samples of the series of 0.15% C, 1.0% Cr, 1.0% Mn, 0.3∼0.7% Si-steels and 0.15% C, 1.0% Cr, 1.0% Mn, 0.3∼0.5% Mo-steels containing boron, tested in normalized or quenched and tempered conditions. In the normalized conditions, the former series did not show any effects of boron-addition, but the latters showed considerably good effects of boron-addition. In the quenched and tempered conditions, the former show the fairly good effects of boron-addition when the amount of Ti was increased to the degree of 0.3% and the content of Si was in the order of 0.3∼0.5%, while the latter the showed the good effects of boron when the amount of Ti added was limitted within 0.2%.
