热分析检测球墨铸铁和灰铸铁凝固特性的实践

Practice of Thermal Analysis in Detecting the Solidification Process of Ductile Iron and Gray Iron

利用热分析系统分别检测了球墨铸铁和灰铸铁的凝固特性,获取到铁液类型、热导率系数和缩孔缩松概率等关键参数。在不同的铸造厂比较了亚共晶、共晶、过共晶球墨铸铁,以及加入不同孕育剂的灰铸铁的热分析检测结果。在将铁液倒入热分析样杯的同时浇注了试块。经检测,与共晶铁液相比,亚共晶铁液的缩孔概率数值更大,并且缩孔概率的大小与这两种铁液浇注试块剖切后发现缩孔缩松的大小规律一致;过共晶球墨铸铁样杯金相中有轻微的石墨开花和聚集,而共晶球墨铸铁样杯金相中没有;与加入硅铁孕育剂的铁液相比,加入硅钡孕育剂缩松概率数值更小,并且缩松概率的大小与试块的缩松缺陷大小规律一致。通过对比试块的宏观缩孔、微观金相和热分析系统获取到的参数,验证了该热分析系统具有一定的实用性。

The solidification characteristics of ductile iron and gray iron were tested by thermal analysis system,and some key parameters such as molten iron type,thermal conductivity coefficient,and shrinkage porosity probability were obtained.The thermal analysis results of hypoeutectic,eutectic,hypereutectic nodular cast iron and gray iron with different inoculants were compared in different foundries.The test blocks were poured while the liquid iron was poured into the thermos-analysis sample cup.According to the test results,compared with eutectic iron liquid,the shrinkage probability of hypoeutectic iron liquid is larger,and the size of shrinkage probability is consistent with the size law of shrinkage hole and porosity found after cutting the test block.There is a slight flowering and aggregation of graphite in the metallography of the hypereutectic nodular cast iron cup,but there is no flowering and aggregation in the eutectic ductile iron sample cup.The practicability of the thermal analysis system is verified by comparing the macroscopic shrinkage hole,microscopic metallography of the test block with the parameters obtained from the thermal analysis system.