【摘要】 热裂纹是厚壁实心冲击垫块出现的主要缺陷。从铸件材质、金相显微组织、浇注温度等方面对热裂纹的成因进行了综合分析。由于垫块表面层含C量低、含S、N量偏高等使表面热裂倾向增大。浇注温度的试验证明了降低浇注温度可以减轻热裂纹的分布,确定了浇注温度为1550℃左右。计算分析铸件凝固过程凝固时间的分布特征,找出了铸件表面脱碳、组织粗大的原因,分析了铸件易形成应力集中的部位。采取了使用75%锆英粉与25%的石墨粉的混合涂料、向钢液中加入稀土元素、在铸型相应位置加暗冷铁和控制浇注温度在1550℃左右的措施,最终消除了热裂纹缺陷。更多还原

【Abstract】 Hot crack is one of the main defects of the thick and large impact cushion block.The reason of the hot crack was comprehensively analyzed from several aspects such as the material,metallographic microscopic structure,pouring temperature,etc.Results show that the hot crack tendency in the surface was higher because the surface has lower carbon content and higher sulfur and nitrogen content.Decreasing the pouring temperature can reduce the hot crack tendency and the optimal pouring temperature was confirmed at about 1 500 ℃ by the experiments.The reasons of decarburization and grain coarsening were further proved and the stress concentration areas were also verified by simulating the distribution characteristics of solidification time.The technologies for removing hot cracks were plotted according to the above analysis,that is:using the composite coating of 75% zircon powder and 25% graphite powder;adding rare-earth elements to molten steel;laying external chill to the down face of the impact cushion block;controlling the pouring temperature to 1 550 ℃.Finally the hot cracks were eliminated.更多还原