铸铁石墨化共晶膨胀对粘砂的影响

Effect of Graphitized Eutectic Expansion of Cast Iron on Penetration

为了解铸铁共晶膨胀粘砂产生原因,用带L型结构的阶梯试块验证灰铸铁共晶膨胀粘砂现象,发现共晶膨胀粘砂部位固定,均处于孤立热节处。通过对粘砂组织进行检验分析,认为粘砂发生于共晶凝固后期,当金属表面凝固一层固体外壳后,铸铁的共晶凝固石墨膨胀会将剩余液态金属渗透到靠近热节的砂型或砂芯中形成粘砂,且共晶膨胀粘砂与碳、磷含量和孕育有一定关系,与铁液温度、铁液静压力和动压力没有关系。

In order to understand the causes of expansion penetration defects.The gray cast iron expansion penetration was verified by the reproduction of the stepped test block with L-shaped structure.The results show that the expansion penetration appears position fixed near the hot spot of the test block.According to the inspection and analysis of metallographic tissue,it is believed that penetration occurs in the late period of eutectic solidification.When the metal surface is solidified with a solid shell,As the eutectic solidification of cast iron,expansion will penetrate excess liquid metal from the casting into the core or mold near the hot spot to form penetration.Expansion penetration has a certain relationship with carbon content,phosphorus content and inoculation.but has no relationship with the temperature,metallostatic and dynamic pressure of the molten metal.