在浇铸如图1的青铜(3-7-5-1)接头时,原来采用金属型泥心铸造。铸出的铸件在下部的孔与孔之间产生裂纹和缩孔。这是因为铸件下部较厚,最后冷却,不能从冒口中得到补缩;因此产生裂纹和缩孔。后来将下边的四个孔改用金属型心,上部的四个孔仍用砂心。 When casting the bronze (3-7-5-1) fitting as shown in Fig. 1, the original cast metal heart was used. The castings cast cracks and shrink holes between the lower holes and the holes. This is because the lower part of the casting is thick and finally cools and can not be refilled from the riser; cracks and shrinkage occur. Later, the following four holes to switch to metal heart, the upper four holes still use sand heart.