Development and Practical Use of Toughened Austempered Ductile Iron

(1)新型等温淬火球墨铸铁的研制与评定从拉伸试验、示波冲击试验和断裂韧性试验等试验结果可以看出，新研制的增韧等温淬火球墨铸铁(TAI)比传统的ADI具有更高的强度和韧性。(2)疲劳性能、耐久性能和噪声的评定首先进行了疲劳扩展试验。结果表明，疲劳裂纹萌生抗力和疲劳裂纹扩展抗力均高于常规ADI。其原因可以认为是残余奥氏体相中的TRIP效应提高了裂纹形核能。其次，对TADI制造的齿轮进行了耐久性试验和噪声试验。试验证明，TADI能延长齿轮的使用寿命，降低齿轮的噪声。(3)TADI齿轮的试车试验将TADI齿轮安装在减速齿轮组合电机中，并进行了耐久性试验。结果表明，TADI齿轮与SCM材料的齿轮具有几乎相同的耐久性。从这些结果中，我们可以有信心，TaI可以作为齿轮材料实际使用。

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.