含Mn鋼の歪時効におよぼすN, C添加の影響

抄録

Steels containing Mn were heat-treated to have different grain size, hydrogen-treated and N or C charged, the content of which was measured by the Snoek peak height. Strain aging index (SAI) was measured by 7.5% straining and 100°C×1 hr aging. In this case, strain rates, and N or C content were changed. The following conclusions were obtained. SAI increased sharply from zero when N content increased from zero to about 10 ppm in 0.3%Mn steel, and it became almost constant when N content was over 20∼40 ppm. SAI increased sharply from zero, when C content increased from zero to under 5 ppm, and it continuously increased with increasing C content, and after passing through a maximum, decreased. The content corresponding to the maximum of SAI, shifted to lower C content when the grain size was larger and the strain rate lower. The effect of Mn content on SAI was small in N-charged 0.3%Mn steel. In the case of C, sometimes 2∼3 kg/mm² SAI was observed even when the Snoek peak height was zero, and in a range of higher C content, SAI tended to decrease with increasing C content. This behavior was different from that observed in the pure iron.