How to ensure the quality of casting sand
In the process of casting at high temperature, due to the thermal expansion of molding sand, it is very easy to cause minor changes in the size of molding sand, which will affect the dimensional accuracy of castings and the appearance and performance of castings. At the same time, excessive thermal expansion coefficient of molding sand will cause casting defects such as sand inclusion, scab, rat tail, etc. All these factors make foundry enterprises more cautious in selecting molding sand, not only considering the thermal expansion coefficient of molding sand, but also taking into account the cost of molding sand.
The basic requirement of casting sand is to have high purity and cleanliness; High fire resistance and thermal stability; Suitable particle shape and particle composition; It is not easy to be wetted by liquid metal; And cheap and easy to get. In addition, the particle shape and particle composition of casting sand have an impact on the fluidity, compactness, permeability, strength and resistance to liquid metal permeability of molding sand, which are important indicators of the quality of casting sand.
In the early period, most of the natural silica sands containing clay, that is, mountain sands and river sands, had good plasticity, but now the emergence of casting sands can be said to be a good substitute, with relatively good characteristics and quality, which has a good prospect in the future trend.
As a kind of casting sand, Baozhu sand has the advantages of high temperature resistance, no breakage, no dust, spherical shape, high permeability, good filling ability, and no harm of silica dust. It is a green and environment-friendly sand. It is suitable for sand casting (molding sand, core sand), V-method casting, EPC (filling sand), coating (Baozhu sand powder) and other casting processes. It is widely used in automotive engines and auto parts, large steel castings, iron castings and other fields, and is known as green environment-friendly casting sand.
Baozhu sand can reduce thermal expansion in the casting process, and its strength will also increase a lot. The amount of resin can be appropriately reduced to reduce gas generation and save costs. Silica sand is relatively pure, followed by high refractoriness quartz sand, which has better roundness and casting finish.