The selection of product pouring position is closely related to the product structure, production conditions of the factory, quality requirements of nodular iron castings and other factors, and also directly affects the determination and implementation of the final casting process plan. The pouring position of nodular cast iron cylinder is generally divided into two types, namely, the split is poured downward and the split is poured upward.
(1) Analysis of the advantages and disadvantages of the split face down pouring
The molten iron enters the mold cavity through the split. After the mold filling is completed, the oxide slag at the front end of the molten iron mold filling will be dispersed on the surface area of the nodular cast iron blank, reducing the surface quality, and a large amount of polishing and finishing will be required later. Although it can meet the flaw detection requirements, there is a risk of excessive grinding resulting in wall thickness exceeding the tolerance. In this scheme, the core head of the sand core can be set within the contour of the split plane. The contour size of the selected sand box is small and the amount of sand used is small. The sand core is assembled first and then the sand mold is assembled. The wall thickness uniformity between cores is difficult to control, the size detection is difficult, and the box closing operation is complex. When pouring molten iron, the sand core is easy to float under the buoyancy of molten iron, resulting in dimensional deviation.
(2) Analysis of advantages and disadvantages of upward-pouring of split
The molten iron enters the mold cavity through the flange of the steam inlet pipe and the thick arc surface at both ends. The oxide slag at the front end of the molten iron mold filling is finally distributed on the upper surface of each partition belt and the split, which are all machined surfaces. The oxide slag can be completely removed in the processing process without manual polishing. The scheme needs to adopt suspended sand core design. The sand core head is set outside the contour of the split plane, which makes the contour size of the selected sand box larger and uses more sand. During box closing, the sand mold is assembled first, and then the sand core. The uniformity of wall thickness between the cores can be effectively guaranteed, the accuracy of size detection is high, and the box closing operation is simple. During molten iron pouring, the risk of sand core floating up is greatly reduced due to the compaction of the upper box mold.
The advantages and disadvantages of the two pouring position selection schemes are comprehensively compared and analyzed, and the pouring position with the split facing up is finally determined. The reason is that although the program uses a large amount of sand, the operation process is simpler and the quality stability is higher, and qualified nodular iron castings meeting the technical requirements can be obtained.