In order to effectively solve the problem of core breaking during sintering of water jacket and oil passage of cylinder block, ZHY casting’s water jacket and oil passage sand core are mixed with a certain proportion of ceramic sand (70 / 140 mesh). The ceramic sand is smooth and round with good fluidity. The sand core produced is smooth and compact. The coating is not easy to cover and penetrate on the surface of the sand core, and the coating spalling defect occurred in the water jacket of casting. In order to improve the adhesion and permeability of the coating, through discussion with the supplier, the refractory, suspension agent, active agent and binder were adjusted to improve the permeability and adhesion of the coating, and the problem was solved. However, the waste products of broken core at the thinnest part of water jacket in gen3 and other cylinder blocks increase obviously. The analysis shows that the penetration layer is too deep, which has a great impact on the high temperature strength of the weak part of water jacket. When the penetration layer depth is adjusted to about 2 ~ 3 mm, the broken core defect of the weak part of water jacket can be effectively controlled.
For the sand core with smooth and compact surface, the permeability and adhesion of the coating should be improved to avoid the coating being too thin or falling off. The best performance of the coating should be explored in combination with different core making processes or different core making materials. However, the single index should not be pursued unilaterally, and the correlation effect of various process parameters should be fully considered.