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研究了两种使球铁基体组织微细化的热处理方法。首先将试样于880℃正火一小时,使之具有片状珠光体组织。工艺一是在奥氏体区的下部反复奥氏体化及随后空冷。此工艺可使珠光体球化。工艺二是将试样快速加热至共析转变的上部温区、热后空冷。此工艺可获得晶粒直径为5～6μ的F+P的基体组织。 在共晶团附近区域富M_n贫Si,因而在其周围趋于保留粗大的珠光体。为使铸铁整个基体达到微细化,就必须保证基体各部分的转变温度大致相同,要达到这一点,除保证低的M_n量及几乎不含微量元素而外,铸铁必须进行高温长时间均匀化退火。
Two kinds of heat treatment methods were studied to make the ductile iron matrix microstructure fine. First, the sample is normalized at 880 ° C for one hour to give a flaky pearlite structure. Process one is austenitic austenite in the lower part of the repeated and then air-cooled. This process can pearlite ball. Process two is the rapid heating of the sample to the eutectoid transformation of the upper temperature zone, air cooling after the heat. This process can be obtained in the grain diameter of 5 ~ 6μ F + P matrix organization. In the vicinity of the eutectic group, Mn-rich Si is depleted and thus tends to retain coarse pearlite around it. In order to make the entire matrix of the cast iron to be miniaturized, it is necessary to ensure that the transition temperatures of the various parts of the base body are about the same. To achieve this, the cast iron must be annealed at a high temperature for a long time in addition to the low M_n content and almost no trace elements .