Abstract: As a new forming process for patternless casting, the extrusion-milling forming technology broke through the conventional sand mold manufacturing method and provided a new notion for the preparation of gradient sand molds. In the processes of gradient sand molds, the supplementary pressure on the surface layers of the sand mold would cause changes in the strength, permeability and thickness of the surface layers, which in turn would affect the casting performance. For this problem, the strength, air permeability and cutting force of the gradient sand molds with different cavity depths were studied. It is found that the distance of supplementary pressure has a great impact on the performance of the sand mold. In the 2~12 mm range of supplementary pressure distance, the larger the distance, the higher the strength, the smaller the air permeability, the higher the hardness and the greater the cutting force. Considering the air permeability, strength and cutting force of the sand mold surface layers, the optimal supplementary distance for different cavity depths was obtained. Finally, the superiority of gradient sand mold was verified by the ZL114A aluminum alloy casting tests.

Key words: patternless casting, gradient sand mold, near net shape, extrusion-milling forming

摘要： 作为一种新的无模铸造成形工艺，挤压切削一体化成形技术突破常规铸型制造方法，给梯度砂型的制备提供了新思路。在梯度砂型成形过程中，对砂型型面层的补压会引起其强度、透气性能及型面层厚度的变化，进而影响铸件性能。针对该问题，从强度、透气性和切削力等方面对不同型腔深度的梯度砂型型面层进行了研究。结果发现，对于相同型腔深度砂型，补压位移对砂型型面层性能影响很大，当补压位移在2~12 mm范围内时，补压位移越大，则砂型型面层强度越高，透气性越小，切削力越大。综合考虑砂型型面层透气性、强度和切削力，得到了不同型腔深度砂型的最优补压距离，并通过ZL114A铝合金浇注试验验证了梯度砂型的优越性。

关键词: 无模铸造, 梯度砂型, 近净成形, 挤压成形