The Effect of Alloy Elements on the Austemper-Transformation of

• Main Authors: Been Yuan Lin, 林本源
• Other Authors: Tien Shou Lei
• Format: Others
• Language: zh-TW
• Published: 1995
• Online Access: http://ndltd.ncl.edu.tw/handle/03322196454715350019

博士 === 國立臺灣科技大學 === 機械工程研究所 === 83 === The investigation was conducted in three phases. First phase, a PC-controlled heat treating system was developed. A specimen was heated to austenitizing temperature and quench to a desired austempering temperature automatically. The change of electical resistivity during austempering was measured and was used to analyze the phase transformation. Second phase , heats containing Ni, Cu, Mn and Mo separately were melt, and bars in diameters of 3mm, 15mm and 75mm were poured. Then, the distribution of elements was quantitatively analyzed using EPMA. Finally, the Charpy impact test and Rockwell hardness measuring were performed for the comparision subject to segreation. Third phase, the .PHI.3mm bars were austempered by the PC-controlled heat treating system. The resistivity data were used to constructed the IT diagrams, and to compare the effect of alloy elements on the kinetics of austempering. Results show that the degree of segregation increases along with the increasing diameter of casting bars. The segregation of elements causes the span of processing window to reduce. The impact values of ADI with less degree of segregation are greater than that with significant segreation, even though the hardness is no difference. The changes of the resistivity curves show out two stages of reaction clearly during the austempering. From these curves, a partial IT diagram is constructed. The alloy elements have an influence on the first stage of bainite reaction, however, the effect on the second stage is no significant. It has been observed that the austempering temperature plays a major role in the processing window.