Abstract
An investigation has been made on application of the cold HNO3 and cold HNO3-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 HNO3 solution through the reaction with iron depend on the concentration of the cold HNO3.
According to the behavior of reaction with iron, the cold HNO3 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 Fe3C, and the analytical condition of 200 ml (-5°C) of HNO3 (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 HNO3-H2O system, the cold HNO3-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.
