鋼に対する合金元素としての窒素（第7報）青熱脆性機構の実験的考察

Abstract

The present investigation has been carried out to ascertain the effect of silicon and oxygen on the blue brittleness in steels.In the 3rd and the 4th reports under this title it has been shown that the blue brittleness would not occur in steels free from the nitrogen and that the more nitrogen content in steels is the more clearly the blue brittleness appears.But, on the other hand, the blue brittleness by carbon would likely to appear more than by nitrogen, as the nitrogen in steel diminished at the upper temperature range.To ascertain the effect of silicon, the short time tensile properties at the temperature range of 0∼320° for steels were determined as shown in Table 1∼2.All specimens employed for this investigation were air cooled from 950°, and then slowly cooled after being tempered for 3 hours at 550°. The tensile value of each steel is plotted in Figs. 1∼14, and the increased percentage of tensile strength and the decreased percentage of elongation or reduction of area at blue brittleness range are plotted in Fig. 7, and the effect of silicon on the tensile strength (σB), elongation (δ), and reduction of area (φ) at room temperature are shown in Fig. 15.To ascertain the effect of oxygen, the short time tensile properties of steels were studied, as shown in Table 3, the result of which are plotted in Figs. 16∼19, and in Fig. 20 is shown the diagram of percentage of blue brittleness versus oxygen percentage.These figures show that the blue brittleness decreases with the increase of silicon content, and by the addition of oxygen in steel the blue brittleness increases a little in the property of elongation.