Low Silicon Steel Research Articles

Martensiteの焼戻におよぼすSiの影響について（第2報）

In order to study the effect of silicon on the tempering of martensite, magnetic analyses were performed. It was demonstrated in these analyses that the starting temperature of the second stage of the tempering was not affected by the silicon contents of steels, but the decomposition of the retained austenite at low temperature became smaller by the addition in steels. Moreover, it was found that the temperature at which the second stage progressed at the maximum velocity in high silicon steels was higher than that in low silicon steels, and, also that the carbides which were precipitated at each tempering stage in high silicon steels were equivalent to the carbides precipitated at the same tempering stages in low silicon steels.

物理化學的諸數値より見たる製鐵製鋼法

The physico-chemical principles involved in iron and steel making process were discussed. Presence of silicon reduced solubility of the carbon in iron. From this experimental data, it was concluded that the activity coefficient of the carbon diminished with the silicon. Since the diffusion constant of the silicon in iron is about one hundredth of that of the carbon, it is considered that carbon diffuses from a high-silicon steel to a low-silicon steel, even though the carbon content of the lower silicon is the greater. In steel making practice, it was found that 15min after the addition of ferrosilicon, the concentration of the silicon in the surface layer of molten bath was several times greater than that in the bottom layer, whereas, the carbon content of the surface was less than that of the bottom layer of the bath. According to J. Chipman, the reduction of silica in blast furnace slag by the carbon in molten pig iron did not reach eguilibrium even after a long period of holding at 1525°C. This results may be interpreted so that the reduction of silica forms the high-silicon layer which interrupts contact of the slag and the carbon in molten pig iron and prevent further reduction of silica. This high-silicon layer also affected upon the rate of desulphurisation of molten pig iron. Desulphurising power of the manganese increased as temperature went down. However, at 1200°C, 1% Mn in liguid iron could not lower the sulphur content to 0.47%. On the other hand, activity coefficient of the sulphur in pig iron was about five times greater than that in pure liguid iron. Therefore, it was expected that the pig iron contained about 0.09% S might be obtained by presence of 1% Mn.