| The phases in a high speed steel (HSS) roll and a nickel-grain cast iron (Ni-grain) roll were quantitatively analyzed by Mo¨ssbauer spectroscopy. Particular emphasis was placed on the presence of retained austenite formed during heat treatment. Roll microstructures were examined by using Mo¨ssbauer spectroscopy as well as optical microscopy and X-ray diffraction analysis. In the HSS roll, austenite formed after austenitization disappeared after tempering. However, in the Ni-grain roll, austenite was formed during casting, and a considerable amount of austenite still remained after stress relief treatment at 450℃ for 30 min. From these results, the longer stress relief time or the higher stress relief temperature was suggested in order to remove the retained austenite in the Ni-grain roll. The Mo¨ssbauer analysis data matched well with the microstructures and the X-ray diffraction analysis data, confirming that the Mo¨ssbauer analysis is quite useful for the quantitative phase analysis of the rolls. |
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