Chill iron for sand casting and its function

In order to increase the local cooling rate of the casting, the chilling material placed in the mold cavity and working surface is called chilling material. Cold syndrome can be divided into two categories: internal cold syndrome and external cold syndrome. The metal chill block that is placed in the mold cavity and can be melted into the casting is called an internal chill block; while the metal chill block that is placed on the surface of the model when the core is called an external chill block.

The internal chiller will eventually become part of the casting and should therefore be made of the same material as the casting. The external cold iron can be recycled and reused. Depending on the material of the casting and the strength of the chilling effect, the external chiller can be made of steel, cast iron, copper, aluminum, etc., or non-metallic materials can be used as the chiller, such as zircon sand, graphite, chromium magnesite, chromium sand , carbon sand, magnesia, etc., because their heat storage coefficient is larger than that of silica sand

Chill iron plays an important role in sand casting. Specifically, it is divided into the following three points:

1. Used in conjunction with the gating system and risers to control the solidification sequence of castings and increase the feeding distance of the risers.

1) Change the solidification sequence of the casting so that it solidifies sequentially.

2) The placement of the cold iron can increase the temperature gradient of the solidification process and make the solidification sequence more obvious.

3) Accelerate the solidification speed of the locally thick parts of the casting so that it solidifies simultaneously with the surrounding parts, eliminating local thermal stress and preventing cracks.

4) Placing cold iron in areas where it is difficult to install risers can prevent shrinkage cavities and pores.

5) The use of local cold iron can control the sequential solidification of castings and increase the feeding distance of the riser.

2. Accelerate the solidification speed of castings, refine the grain structure, and improve the mechanical properties of castings. In sand casting, an effective way to increase the solidification rate is to place cold iron, especially at the ends of the plate, where the solidification rate is faster than without cold iron. For aluminum alloy castings, due to the slow solidification speed, gas is easily precipitated in the alloy and pinholes are formed. Using a cold iron can reduce the degree of pinholes. This is due to the chilling effect of the cold iron, which accelerates the solidification speed and prevents the gas from precipitating, thereby reducing the degree of pinholes in the casting.

3. Chill iron can also be used to divide the feeding area of the riser, expand and control the feeding range of the riser, thereby improving the feeding efficiency.