1969 Volume 55 Issue 9 Pages 846-860
Fundamental study on isolation and determination of oxide inclusions in steels was carried out by means of nitric acid, iodine-alcohol, bromine-ester and chlorination methods.
The results are as follows.
1. In the halogen-organic solution method, the oxide inclusions are isolated and determined by decomposing the plate-like specimen with iodine-alcohol or bromine-ester solution at their boiling points without considering the existence of sulphides and M3C type carbides. This method is applicable to semi-killed and killed carbon steels. In bromine-ester method, decomposition of specimen is easier and faster than in the iodine-alcohol method, and sulphides in steel are decomposed perfectly.
2. In the chlorination method, the stable oxide inclusions are isolated and determined by such procedure that the plate-like specimen is decomposed directly with chlorine at 500°C and the vaporizable chlorides are separated from the residue by heating at about 900°C in vacuo. By use of the apparatus dsiegned for this experiment, five specimens are able to chlorinate at the same time, and so the efficiency of operation is very improved. This method is applicable to semi-killed, killed carbon steels and low alloy steel, and it's precision is comparatively high because of complete decomposition of sulphides, carbides and nitrides. On the other side, there is a fault that the oxide inclusions consisting of lower valency cation tend to decompose disproportionally in the isolation process.
3. Nitric acid method is the most simple and convenient, and can be applied to killed carbon steel and low alloy steel containing aluminum.
Further, the behavior of non-metallic inclusions in various isolation processes are examined by opticalmicrography, electromicrography, X-ray and electron diffractions.