An investigation has been made on application of the cold HNO
3 and cold HNO
3-alcohol methods to analysis of nonmetallic inclusions in steels.
The results obtained are summarized as follows:
(1) The changes of natural potential and temperature of the cold HNO
3 solution through the reaction with iron depend on the concentration of the cold HNO
3.
According to the behavior of reaction with iron, the cold HNO
3 medium may be divided into 3 ranges, namely the high concentration range of (4+1) - (1+1) at-15°--5°C, the medium concentration range of (1+3) - (1+7) at-5°-0°C, and the low concentration range of (1+9) - (1+50) at 0°-5°C.
(2) The medium concentration range is most suitable for decomposition of Fe
3C, and the analytical condition of 200 m
l (-5°C) of HNO
3 (1+7) has been confirmed to be most recommendable for analysis of nonmetallic inclusions in killed steels (sample taken 1g).
(3) As compared with the cold HNO
3-H
2O system, the cold HNO
3-alcohol system has some different aspects; the natural potential and the dissolving rate for iron are rather lower, but the low concentration range of the system can be applied even below 0°C without freezing.
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