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若干年前,球墨铸铁在汽车上的应用还只限于承受一般应力的零件。球铁制的凸轮轴、曲轴、连杆、轮毂和其它零件,已列为轿车的标准零件。但也只是在球墨铸铁被宣布能用来代替锻钢制造汽车后桥双曲线主、从动齿轮以后,它在汽车上的应用才开拓了一个新领域。后桥传动齿轮所受的应力,比球铁过去所代替的其它零件高。这种齿轮必须具备高抗拉强度、硬度、抗冲击和韧性等综合性能。这通过对球铁进行一般的淬火处理是不能达到的。然而,用等温淬火处理可使这种齿轮获得所需要的性能。在霍尔克罗夫特(Holcroft)和菲亚特工厂,已经装备了能进行等温淬火的各种设备。
A few years ago, the application of ductile iron in the car is only limited to the general stress of the parts. Ductile iron camshafts, crankshafts, connecting rods, hubs and other parts have been listed as standard parts for cars. But it is only after the ductile iron was announced that it can be used instead of forged steel to make the hyperbolic main and driven gears of the rear axle of the automobile, and its application in the automobile has only opened up a new field. The stress on the rear axle drive gear is higher than other parts replaced by ductile iron in the past. This gear must have high tensile strength, hardness, impact and toughness and other comprehensive performance. This can not be achieved by the general quenching of ductile iron. However, this gear can be obtained with the required properties by the austempering process. At Holcroft and Fiat plants, there are already a variety of equipment that can be isothermal quenched.