Boron, oxygen, sulphur, nickel, copper or zirconium was added to high purity iron to study the effect of alloying elements on austenite grain size. The results are summarized as follows;
1) Boron showed a strong effect upon coarsening the austenite grain size within the range of the concentration from 0.0012 to 0.0127%.
2) Oxygen had a weak effect upon coarsening the austenite grain size when it was dissolved in austenite or precipitated as wiistite, but an inverse explanation could be made on the effect of wastite from the view point of dissolution of wastite. Further investigation is necessary to clarify the effect of dissolved oxygen and wastite. Alumina type oxygen had a tendency to inhibit the grain coarsening.
3) Austenite grain size was not affected by the addition of sulphur within the range from 0010 to 0.39%.
4) Nickel showed a strong effect upon refining the austenite grain size up to about 10%, while it had a effect upon coarsening the austenite grain when the content of nickel was higher than 10%.
5) Austenite grain size was not affected by the addition of copper within the range from 0.008 to 1.00% but was refined by the addition of 294% copper.
6) Austenite grain size was slightly refined by acid soluble zirconium within the range from 0.047 to 1.82% while the refining effect was not so obvious within the range where Fe2Zr was assumed to be precipitated.
