How to reduce slag inclusion defects in lost foam castings?

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  • By:Hebrew Trade

The function of the lost foam casting coating is:

1. Improve the surface smoothness of high-quality railway castings, reduce the roughness of castings by 2–3 levels, and improve the surface quality and application performance of castings.

2. Reduce and avoid the defects of slag inclusion and sand holes.

3. It is beneficial for sand cleaning and sand shakeout.

4. Successfully complete the sprayed layer to flow out of the metal casting sand, avoiding the alloy liquid from penetrating into the sand mold and avoiding pores, metal material penetration, and carbon defects in the casting.

5. Improve shape strength and bending stiffness, prevent deformation and damage during transportation and sand filling vibration molding, and help improve the dimensional accuracy and yield of high-quality zinc alloy die castings. Coatings for lost wax casting are required to have a series of properties such as strength, air permeability, fire resistance, heat insulation, explosive heat crack resistance, rapid cooling, acute heat resistance, water absorption, cleanliness, coating and hanging properties, floating properties, and no fluidity. Performance: to avoid the shortcomings of welding tumors, the first requirement is that the coating has high strength and fire resistance. It is stipulated that the coating applied on the surface of the white mold will not produce cracks during drying and transportation, that is, the coating should have sufficient indoor temperature strength; in the case of pouring, under the effect of long-term high-temperature metal washing, the coating does not need to shed, have no cracks, or have high continuous high temperature strength.

When the shape memory alloy enters the metal mold, the straight inlet is tightly closed, the coating layer on the surface of the casting and the gating system do not fall off, and no cracks or dry cracks are the prerequisites for avoiding the defects of welding spars. If the sprue is sealed If the properties are not tight, the paint layer will fall off, crack,and a large amount of sand, paint, and inclusions will enter the metal to form weld defects. Intensity and air permeability are the two key properties of coatings. Sometimes it is stipulated that the lost foam casting coatings used in gating systems should have higher fire resistance than casting coatings, so as to resist the long-term washing effect of silica sol investment casting continuous high-temperature metal materials. The operator must ensure the uniformity of the paint during the brushing process.

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