Teach you how to solve the permeability problem in the process of coated sand

Common defects, main causes and solutions in the use of coated sand

1. The resin in the casting internal shrinkage coated sand burns at high temperature to generate heat, which slows down the solidification rate of molten iron and leads to shrinkage. Chilled coated sand is used; internal chilled iron is placed in the shell core.

2. The loose core injection pressure on the surface of the mold (core) is too high or too low; The mold does not exhaust smoothly; The mold runs sand due to the large gap between the box surfaces. Coated sand has poor fluidity or poor air permeability. Choose reasonable sand injection pressure to improve the exhaust system and prevent suffocation; use materials with small deformation as core boxes; choose coated sand with good fluidity and air permeability.

3. The mold for deformation and fracture of the mold (core) is unevenly heated, or the thickness of the core wall is greatly different, resulting in inconsistent shrinkage during cooling; Resin with large curing shrinkage rate is used; Deformation of core fork or uneven storage of sand core; Coated sand has poor high temperature performance; Excessive pouring pressure improves the mold structure and makes the temperature distribution uniform; Use molding tray to store sand core; Use resin with small curing shrinkage rate; Use high temperature resistant and low expansion coated sand; improved gating system (no pressure type).

4. casting surface bad phenolic resin at high temperature generated bright carbon floating in the molten iron surface, solidification of the casting surface produce wrinkled skin. About 2% iron oxide powder is added, raw sand with high thermal conductivity is used, the surface of the shell core is painted, and special accessories are added to the coated sand.

5. Shelling mold design is unreasonable, the core box temperature is not uniform, so that the low temperature part of the low strength and shelling; coated sand melting point is low, the curing speed is slow, the thermal strength is low. Improve the mold structure, so that the temperature distribution is uniform; choose high melting point, fast curing speed, high thermal strength of the resin.

6. The air hole core of the casting is not exhausted smoothly; The resin sand has a large amount of gas or the gas emission speed is inappropriate; The sand core is not completely cured. Improve the exhaust system, improve the exhaust effect; select high concentration or coarse raw sand; use low gas coating sanding process.

7. The local strength of the through-core sand core is low or loose; the thickness of the crust is thin. Improve the mold structure to make the temperature distribution uniform; select the resin with high melting point, fast curing speed and high thermal strength; adjust the sand shooting pressure; improve the exhaust system.

8. Casting sticky sand raw sand SiO2 content is low; core surface is not dense. Adjust the sand injection pressure to improve the exhaust effect of the core box and make the surface of the sand core denser; adopt high temperature resistant coated sand or zirconium sand coated sand.

This article is finished by coated sand, the point of view of this article does not represent the point of view of this site.