Foundry sand processing is an important part of the casting process, and its quality directly affects the precision and surface quality of castings. Foundry sand is mainly composed of raw sand, binder and additives. Through reasonable composition methods and processing processes, the performance of foundry sand can be improved to meet different casting needs.
Raw sand is the basic material of foundry sand. Commonly used raw sands include silica sand, zircon sand, chromite sand, etc. Silica sand is widely used because of its abundant resources and low cost. However, silica sand has poor refractoriness and thermal stability. Therefore, when casting high-temperature alloys or large castings, high-performance raw sands such as zircon sand or chromite sand are often selected.
Binders play the role of connecting sand particles and forming sand molds in foundry sand. Common binders include clay, resin and water glass. Clay binders are low in cost and suitable for ordinary castings; resin binders have high strength and fast hardening speed, and are suitable for high-precision castings; water glass binders are gradually valued because of their good environmental performance.
The addition of additives can improve certain properties of foundry sand. For example, adding coal powder can improve the anti-sticking performance of the sand mold; adding sawdust can improve the air permeability of the sand mold and reduce pore defects. In addition, other additives, such as graphite powder, coke powder, etc., can be added according to specific needs to improve the comprehensive performance of the sand mold.
The processing methods of foundry sand include sand mixing, compaction and regeneration. Sand mixing is to mix the original sand, binder and additives in a certain proportion to ensure the uniformity and stability of the sand mold. Compacting is to make the sand mold reach a certain degree of compactness through vibration, compaction and other methods to improve the strength and deformation resistance of the sand mold. Regeneration is to process and reuse the old sand, which not only saves resources but also reduces environmental pollution.
Through reasonable composition methods and processing processes, the performance of foundry sand can be improved, casting costs can be reduced, and the quality of castings can be improved.