热分析法(记录冷却曲线)是研究合金结晶过程的基本方法之一。很多研究家在研究球墨铸铁结晶过程时,都曾采用了这种方法。从记录下来的冷却曲线来看,不可否认的事实是,加镁或铈处理的球墨铸铁的共晶转变温度要比同成分片状石墨铸铁低(通常叫做过冷度大)。现在许多学派,如认为过冷度大是生成球状石墨的先决条件。此外De—Sy,Wittmoser,Piwowarsky,都曾指出,在球墨铸铁冷却曲线上没有发现共晶转变等温平台,而共晶转变是在一个温度区间内进行的。De-Sy,Wittmoser根据这一现象,认为球墨铸铁的一次结晶不是按共晶系,面是按固溶体系完成的,也就是就,初生晶只能是过饱和的γ固溶体,而石墨相则是在过饱和奥氏体颗粒中析出来的。把这一现象看做是,在球墨铸 Thermal analysis (recording cooling curve) is one of the basic methods to study the crystallization process of alloys. Many researchers have used this method when studying the crystallization of ductile iron. Judging from the recorded cooling curves, it is undeniable that the eutectic transformation temperature of ductile cast iron with or without magnesium is lower (usually called subcooling) than that of the same flake graphite cast iron. Now many schools, such as that the undercooling is a prerequisite for the formation of spherical graphite. In addition, De-Sy, Wittmoser, Piwowarsky, have pointed out that in the cooling curve of ductile iron did not find eutectic transformation isothermal platform, and eutectic transformation is carried out in a temperature range. De-Sy, Wittmoser According to this phenomenon, it is considered that the primary crystallization of ductile iron is not eutectic and that the surface is formed by solid solution system, that is, the primary crystal can only be a supersaturated γ solid solution and the graphite phase is Precipitated in supersaturated austenite grains. Think of this phenomenon as being in ductile casting