Coating of precision steel castings

Ensure the coating quality of precision steel castings.

(1) The selection of high temperature and good air permeability coating, improve the permeability and wettability of the coating, reduce the air pressure in the air gap, and ensure the smooth filling of metal liquid. Dry sand mold with dry sand casting, dry sand mold than the paint is much higher permeability, the permeability of the paint mainly depends on the size of the paint permeability. Under the condition of low gas permeability, the gas permeability of the coating is much less than the pyrolysis rate of the face, the pressure of the alloy liquid in the air gap before the alloy flow is very large, and the flow front of the liquid metal is very unstable, resulting in enrolling and inspiratory gas.

(2) Uniform coating, coating should be uniform, high temperature strength should be reduced, generally controlled in 0.5~1mm.

(3) The paint should be fully dried, and the shape after drying should be poured in time to avoid moisture.

On this basis, through the above three measures, the silica sand particle size from the original 0.071mm(200 mesh) to 0.080mm(180 mesh); The latex is changed from the original 25kg to 20kg; Cellulose from the original 4kg to 5kg. The high temperature strength and air permeability of the coating are improved, and it is not easy to crack.

Set up the slag collection and discharge risers.

The gas decomposition products in the shape of polystyrene foam are all coated and leave the cavity. Due to the fast filling speed of the metal liquid, the liquid pyrolysis products cannot be fully cracked and evaporated, which makes the liquid products or residues easily form pores in the dead corners or top of the casting. In this way, these parts should have small risers, which are coated with many small holes, so that the liquid product that easily accumulates is discharged when it finally evaporates. The riser size can be set according to the size of the product, and it can be easily removed. The results show that these small risers can effectively eliminate slag inclusion and porosity defects in castings.