What aspects should be considered in the design of the riser? Let's have a look!

The form, size and location of the riser with different functions are not the same, so the design of the riser should consider the nature of the casting alloy and the characteristics of the casting.

1. For alloys with small volume shrinkage during solidification (such as gray cast iron), or alloys that do not produce concentrated shrinkage holes (such as tin bronze), the role of the riser is mainly to discharge the gas in the cavity and collect the liquid metal mixed with inclusions or oxide films at the front of the flow to reduce the defects on the casting. The riser is mostly placed on the opposite side of the inner gate, and its size need not be too large.

2. For castings requiring control of microstructure, the riser can collect the cooled metal liquid at the front of the flow to avoid supercooled microstructure on the casting. The piston ring of the single casting is provided with a small riser on the opposite side of the inner gate to collect the cold metal, where there will be no white tissue due to the metal being too cold, leading to the scrap of the casting. The size and location of such riser should be determined according to the microstructure requirements of the casting.

3, for large volume shrinkage during solidification and tend to form concentrated shrinkage of the alloy (such as cast steel, manganese brass and aluminum bronze, etc.), the main role of the riser is to compensate for the liquid shrinkage of the metal liquid in the cavity and the shrinkage of the casting solidification process, in order to obtain a dense casting without shrinkage. When the casting is cooled in the mold, the thin part solidifies first, and its shrinkage can be compensated by the thicker part nearby; When the thicker part solidifies, it can be compensated by the thickest part; When the thickest part solidifies, if no external compensation is obtained, large shrinkage holes will be formed there. In this case, the role of the riser is to compensate for the solidified part of the casting, so it should be placed above or on the side of the thickest part of the casting, and its solidification requirements are later than the thickest part of the casting.

The above content is for reference only. Welcome to inquire!