Development and Practical Use of Toughened Austempered Ductile Iron

本研究分为以下三个步骤。(1)研制和评价一种新型奥贝球墨铸铁。通过拉伸试验、仪器夏比冲击试验和断裂韧性试验等试验结果，阐明了新研制的增韧奥贝球墨铸铁（TADI）比传统的奥贝球墨铸铁（ADI）具有更高的强度和韧性。此外，还澄清了ADI中延展性的损失是由于碳化物的形成和二次石墨的析出。(2)首先对taadiat进行了疲劳性能、耐久性和噪声评价，并进行了疲劳传播试验。试验结果表明，该材料的抗疲劳裂纹萌生能力和抗疲劳裂纹扩展能力均高于常规材料。其原因可以认为是由于残余奥氏体相的TRIP效应使裂纹成核能增加。其次，对TADI制造的齿轮进行了耐久性试验和噪声试验。经实践证明，TADI可以延长齿轮的使用寿命，降低齿轮的噪声。(3) TADI齿轮试验TADI齿轮已装入减速齿轮组合电机，并进行了耐久性试验。它已经发现，TADI齿轮几乎相同的耐久性与一个由SCM材料制成。从这些结果中我们可以有信心，TADI可以实际用作齿轮材料。

This research is consisting of three steps as follows.(1) Development and evaluation of a new austempered ductile cast ironfrom the results of various tests such as tensile test, instrumented Charpy impact test and fracture toughness test, it has been clarified that the newly developed toughened austempered ductile cast iron (TADI) has greater strength and toughness than the conventional austempered ductile cast iron (ADI). Moreover, it has been clarified that the loss of ductility in the ADI is due to the formation of chi-carbides and the precipitation of the secondary graphites.(2) Evaluation of fatigue properties, durabilty and noise of TADIat first, the fatigue propagation test has been conducted. It has been confirmed that both of the fatigue crack initiation resistance and fatigue crack propagation one are higher than the conventional ADI. Its cause can be considered due to the increasing of the crack nucleation energy by the TRIP effect in the retained austenite phase. Next, the durability test and the noise one have been conducted for the gear wheel made from the TADI. It has been confirmed that TADI can prolong the life time and lower the noise of the gear wheel.(3) Trial test of the TADI gear wheelThe TADI gear wheel has been put into the reduction gear combined motor and the durability test has been conducted. It has been found that the TADI gear wheel has almost the same durability with the one made from SCM material. We can have the confidence from these results that the TADI can be used practically as the gear wheel material.