Causes and solutions for pores in silica sol precision casting

Porosity is a common precision casting defect. Porosity refers to the smooth hole defect in individual positions of silica sol precision casting. Porosity is usually discovered after processing. Combined with years of workshop production experience, the causes and prevention methods of pores in precision castings are summarized:

I. Causes of formation:

1. In most cases, the generation of pores is mainly due to insufficient roasting of the shell of the silica sol precision casting crystallizer. When pouring molten steel, the shell of the crystallizer cannot be discharged smoothly, and then invades the liquid metal to form pores.

II. Due to the shell making process or shell material, the permeability of the shell is too poor, and it is difficult to discharge gas from the cavity. The pores are formed by entering the liquid metal.

3. Casting pores caused by the failure of air in the molten steel during the pouring process.

II. Prevention methods

1. When the conditions of precision casting allow, the exhaust hole is set at the highest point of the complex structure of the casting.

2. When designing the pouring system, the exhaust requirements of the shell should be fully considered.

3. The baking temperature and time of the shell should be reasonable, and the insulation time should be sufficient.

4. The wax should be completely removed during dewaxing.

5. Appropriately shorten the distance from the pouring gate to the pouring cup to make the pouring speed uniform to ensure that the cavity in the molten steel is filled and stable, and as little air as possible is involved in the molten steel, so that the gas in the cavity and the molten steel can be discharged smoothly.