In the 1980 s，CTI( Casting Technology International ) has studied and introduced the steel Lost foam precision casting technology (Replicast CS method, R method), is an important development.
R method can be briefly described: High density EPS pattern,Silica sol shell making,cold shell vacuum casting. Using this way in the production of steel casting could eliminate carburization defect completely. This method is applicable to any steel material especially in low carbon steel, high alloy steel, and it can produce a much bigger product than investment castings, its dimensional accuracy and surface roughness can be achieved as good as small piece of lost wax product.
The process of R method:
- Using high density EPS pattern.As long as the density increase, it can improve the dimension precision of shape, reduce the surface roughness，therefore beneficial to the improvement of casting quality;
- According to the size of the casting piece, apply 3-4 layers of colloidal silica coatings, each layer need to be coating sand and dry them.
- Heat 5 minutes the the 950℃stove， burn the EPS pattern, meanwhile sintering the shell mold;
- Put cooled shell in a special vacuum flask,fill in the dry sand, vacuum when pouring;
- Stop the vacuum when it is poured to prevent mould for casting shrinkage and avoid hot crack defects occur;
- Recycle the old sand;
R method compared with others：