The position of the casting in the mold during casting affects the quality of the precision casting, the dimensional accuracy, and the difficulty of the molding process.
The selection principle of the pouring position:
1. The important processing surface of the
precision casting or the main processing surface is facing down or on the side: when pouring, the gas, molten slag and the sand in the mold will float upward, which may cause pores and slag inclusions in the upper part of the casting. Defects such as blisters, and the possibility of defects in the lower part of the casting, the organization is denser.
a. The casting position of the machine bed should face the rail face down to ensure the quality of the important working face. The quality of the circumferential surface is relatively high. The vertical casting scheme is adopted to make the circumferential surface on the side to ensure uniform quality.
2. The casting of the precision casting is directed downward or obliquely: due to the strong thermal radiation of the molten metal on the upper part of the casting, the top sand-shaped expansion arches are even cracked, causing sand, blisters, etc. in the large plane. defect. The large flat face down or the oblique casting method can avoid large-scale production casting defects.
3. The thin wall of the precision casting is facing down, sideways or inclined: in order to prevent cold partitioning of the thin part of the casting and no defects, the thin wall with a larger area should be placed in the lower part of the casting or placed on the side wall or Tilt position.
4. The thickness of the precision casting should be placed on the top or on the side of the parting surface. The main purpose is to facilitate the feeding of the riser in the thick part.
Stainless steel casting is to use a suitable investment material to make the investment mold. Repeat the coating of the refractory coating, refractory sand, hardening and drying on the investment mold, and then melt the internal investment material; then, the strength is sufficient by roasting. A shell type without residual investment material for casting molten metal to obtain a high-precision casting. The lost wax casting process is adopted, the investment material is paraffin and stearic acid, the wax mold making and shell making process adopts an automatic assembly line, and the coating uses water glass as a binder.
The precision casting has a high production efficiency and a small footprint. For the middle part, various high-pressure molding machine production lines and air-punching molding lines can be selected to meet the requirements of fast and high-precision molding production lines. Selection: high-efficiency core making methods such as cold core box, hot core box and shell core. Medium-sized large castings can be considered for the application of resin self-hardening sand molding and core making.
One of the more common problems encountered in the process of precision casting is that there are pores inside the product. For some parts with higher requirements, the pores inside are not allowed inside, so the silica sol is precision cast in processing. It is necessary to prevent stomata.
The choice of precision castings in terms of their methods and methods should be considered, mainly for the adaptability of the method, and whether advanced modeling or core-making technology can be used to improve work efficiency through equipment. For the casting of ferrous metals, it can be precision cast. Moreover, depending on the characteristics of the casting, it can be used to produce some thin-walled castings.
