The Study on the Phase Transformation of High Silicon Cast Steels during Austempering

• Main Authors: Chuen En Wang, 王主恩
• Other Authors: Tien Shou Lei
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/66456163075204381513

碩士 === 國立臺灣科技大學 === 機械工程系 === 88 === The purpose of this study was to investigate the phase transformation of high silicon cast steels, the effect of austenitizing temperature, austempering temperature, carbon and silicon elements on the phase transformation was investigated. The specimens of length 100mm, width 2.5mm and height 2.5mm was installed in vacuum heat treating system controlled by a personal computer and loaded with a austempering program. The change of electrical resistivity of high silicon cast steels during austempering was measured in this system via a real-time scheme. The fractions of retained austenite were measured with χ-ray diffraction and compared with the data of electrical resistivity. Results of this study show that the resistivity of high silicon cast steels during austempering changed with time and showed three sequences of phase transformation, first stage, the processing and second stage. This result was similar to that of ductile iron, therefore, the phase transformation of high silicin cast steels during austempering is composed of two stage of bainite reactions. The study were also showed the austenitizing temperature have no influence on the phase transformation, but austempering temperature have an influence; at high austempering temperature and two stage reactions was finish quick. Decreasing the austempering temperature results in a reduce of the reaction rate and also cause the widen of the processing window. The C, Si elements have an influence on the second stage of bainite reaction, however, the effect on the first stage is no significant. In the processing window has the maximum amount of retained austenite.