Abstract
The author analysed the quantjty of retained austenite employing the integrated intensity of X ray diffraction lines and Hurlbut counter to quantify the results of dimensional stability of ball bearing steel mentioned in Report No.1 and 2. The results were as follows:
1) The retained austenite increased with higher quenching temperature, and repeated quenching increased it too.
2) The retained austenite increased by tempering immediately after quenching.
3) The retained austenite.decreased about 3-4% by one day of air cooling after quenching and prior to tempering, or by employing secondary tempering, compared with specimens tempered immediately after quenching.
4) The retained austenite decreased by subzero treatment and even after marquenching.
5) The quantity of spheroidized carbide decreased by higher quenching temperature and also by repeated quenching.
6) The crystal structure before quenching affects the diffusion of spheroidized carbide into matrix. Increase of the retained austenite was proportional to the degree of spheroidized carbide diffusion into matrix. The dimensional stability was also influenced by the crystal structure.
7) The quantity of retained austenite was influenced by the cooling rate according to the mass of specimens.
The above results can quantitatively prove the experiments on dimensional stability of ball bearing steel introduced by the previous two reports. Moreover, he studied relations between the .dimensional changes by heat treatment and the retained austenite and magnetic properties, for further considerations on ball-bearing steel problems.
