Coated sand is generally composed of aggregate, binder, curing agent, lubricant, and additives.
Aggregate is the main material of coated sand. The requirements for aggregate (raw sand) are: high fire resistance, low volatile matter, relatively round particles, high compressive and impact strength. Scrub silica sand is generally used, mainly because Its reserves are abundant and the price is cheap. Generally, it can meet the requirements of customers. Only when special steel castings and cast iron parts have special requirements, special sands such as zircon sand, chromite sand, or artificial special sands such as precious pearl sand are used. The general requirements for silica sand are:
⑴SiO2 content:> 90% for cast iron and non-ferrous alloy parts,> 97% for cast steel parts;
Mud content: <0.2%;
⑶ particle size distribution: 3-5 sieve distribution should be used;
⑷AFS fineness: different fineness should be selected according to the size and surface roughness requirements of the casting, generally AFS50-65;
⑸ Grain shape: Raw sand with a round shape should be used as much as possible, and the angle factor is <1.3;
⑹Neutral material, pH value is about 7;
⑺Silicon sand must be scrubbed with water. If there are special requirements, pickling or high temperature activation treatment (900 ° C roasting) is required.
Since the new century, many man-made foundry sands have been rapidly applied in the coated sand industry. Among them, the pearl sand is a relatively good comprehensive property and is widely used.
Qinbao pearl sand is a new type of foundry sand developed by Luoyang Kailin Casting Co., Ltd. in the late 1990s. Its main chemical components are Al2O3 and SiO2, and the main mineral phases are mullite and corundum.