Basic characteristics of Gray Iron Castings

The basic characteristic of high density moulding sand for gray iron castings is that the addition of pulverized coal is also low. Therefore, the following points should be grasped when blending sand.

 

1. Clay content and mud content.

 

The strength of moulding sand with high clay content increases with the increase of specific pressure, and the effective bentonite is usually controlled in the range of 7% 10%. The sum of effective clay and dead clay in moulding sand is equivalent to the mud content, which is generally controlled in the range of 12% 16%. Too high or too low mud content will affect the performance of moulding sand.

 

2. Moisture.

 

The moisture content in sand made by lost foam casting is the main factor that determines the plasticity and adhesion of clay. When the moisture content is too high, it is easy to worsen the cohesive force of clay, decrease the fluidity of molding sand, and can not get uniform mold density. When the moisture content is too low, the molding sand is not easy to mix, the strength of the molding sand is low, the brittleness is high, and the molding ability is poor, which is easy to cause sand adhesion defects in the castings. In general, the moisture content should be 10% 20% higher than that when the wet compression strength peak is obtained.

 

3. Grain size of raw sand.

 

In high-density molding, the sand mold has high density and large expansion during pouring, so the grain size of the original sand should not be too concentrated, and the original sand particles are round or polygonal, generally choose three-sieve sand or four-sieve sand.

 

Gray iron castings have obvious advantages. Kunfeng Foundry Factory specializes in casting, welcome to consult and customize.