Process for casting thick and large nodular cast iron valve plate

Abstract

The invention provides a process for casting a thick and large nodular cast iron valve plate. The process comprises the following steps of: (1) manufacturing a mould; (2) manufacturing a casting mould and a sand core; (3) drying and integrating; (4) smelting; (5) pouring; and (6) shaking out and cleaning. In the process, a large number of external chilling blocks and sand separation chilling blocks are used on upper and lower surfaces of a casting for chilling, appropriate placing positions and thickness are selected, and shrinkage cavity and shrinkage porosity of the casting are effectively avoided; meanwhile, a good graphite balling state is ensured by quickly chilling, a feeding head is avoided, the casting is easy to clean, 5 percent of molten iron using amount is saved, and production cost is reduced; a semi-closed casting system is adopted by a casting system, an ingate is uniformly distributed around the casting mould, and the casting mould is slightly scoured, and a good residue stopping effect is achieved; and under the action of chilling of chilling blocks, the thick and large nodular cast iron casting which is smelted by a cupola furnace is good in moulded surface, and meets production requirements, offscourings and sand are avoided, and process yield is improved by 5.9 percent.

Description

technical field [0001] The invention belongs to the field of casting and relates to a casting process of a thick ductile iron valve plate. Background technique [0002] Ductile iron is a widely used cast iron material. It obtains nodular graphite through spheroidization and inoculation treatment, which effectively improves the mechanical properties of cast iron, especially the plasticity and toughness, so as to obtain higher strength than carbon steel. [0003] The shape of the valve plate is simple, and its structure is as follows: figure 1 As shown, it is in the shape of a disc, the upper end of the disc is provided with a flat-bottomed boss, and the edge of the lower end of the disc is symmetrically provided with semi-annular lugs, and the annular lugs have holes, and the semi-annular lugs away from the edge of the disc The other end is closed. [0004] In the existing process of casting the valve plate with ductile iron as the material, due to the thin thickness of the...

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Problems solved by technology

[0006] 1. Due to the large thickness of the casting, and the solidification method of ductile iron is mushy solidification, if the natural cooling molding method is adopted, it is very easy to cause defects such as shrinkage cavity, shrinkage porosity, graphite floating and spheroidization recession in the casting, which cannot meet the production requirements. ;

[0007] 2. Setting the feeding riser will cause a lot of waste of molten iron, and after the casting is completed, it is difficult to clean the feeding riser, which is time-consuming and labor-intensive;

[0008] In addition, the castings cast by the cupola have a lot of dross and sand on the surface, and the process yield is low

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