During the manufacturing process of the riser of the pump valve casting, in order to effectively avoid the defects of the product, the supplementary part above or beside the casting is added. In the casting mold of the pump valve, the cavity of the riser is stored liquid. Metal containers have many functions. The riser with different functions has different form, size and opening position. Therefore, the design of the riser should take into account the properties of casting alloy castings and the characteristics of castings.
Riser for pump valve castings For alloys with little volume shrinkage during solidification or for alloys that do not produce concentrated craters (such as tin bronze), the effect of the riser of the valve casting is mainly to discharge the gas and the collection flow in the cavity. Leading metal mixed with inclusions or oxide films at the leading edge to reduce defects on castings. This type of riser is often placed opposite the inner gate, and its size does not have to be too large.
For pump valve castings that require controlled microstructures, the riser can collect the cooled metal liquid at the front of the flow to avoid overcooling of the casting. The globe valve casting is a single-cast piston ring. A small riser is placed opposite the ingate to collect the cold metal. This will not cause white-colored tissue due to metal over-cooling, resulting in scrapping of the pump valve casting. The size and location of the risers of such castings shall be determined based on the microstructure of the castings.
For alloys with large volume shrinkage during solidification and tending to form concentrated shrinkage pores (such as cast steel, manganese brass, and aluminum bronze, etc.), the main effect of the riser of the valve casting is to compensate for the liquid shrinkage of the molten metal in the cavity. And the shrinkage of the pump valve during solidification to obtain a dense casting without shrinkage.http://www.pump-casting.com