Phenolic resin as coated sand for molding and core making
Using the characteristics of high tensile strength and low gas evolution of Fused Ceramic sand, the coated sand with high temperature resistance, low expansion, easy collapse, high strength and low gas evolution can be made by resin coating. For particularly complex cores, it can also solve the problem of inaccurate shooting.
The application of Fused Ceramic sand shell mold precision casting process has developed rapidly in recent years, from the initial bucket teeth of engineering machinery to the current general parts such as valves and water heaters, auto parts to tool hardware parts, from cast iron, cast carbon steel, to stainless steel, heat-resistant steel and non-ferrous alloys, to various fields of original sand mold casting, metal mold casting and precision casting, Good economic and social benefits have been achieved.
Basic phenolic resin molding and core making
The strength of alkaline phenolic resin self-hardening sand increases with the increase of resin content, but the strength increases slowly at a certain amount. The increase of resin dosage will not only increase the production cost, but also increase the residual alkali in resin sand and the carbonaceous coating on the sand surface, which will affect the quality and strength of recycled sand and the regeneration rate of used sand. In order to reduce the production cost, improve the quality of reclaimed sand, and make the strength meet the production needs, the amount of resin should be reduced as far as possible.
Sodium Silicate modeling
Because the metal static head of large steel castings is high and the pouring time is relatively long, the thermal, mechanical and chemical reactions between the metal and the mold are very strong. On the surface of the casting, especially in the hollow of the sand core or mold, it is easy to produce metal penetration and sand sticking. This phenomenon will not only reduce the quality of the casting surface, but also worsen the conditions of the casting cleaning labor. More seriously, it may cause the sand cleaner to suffer from silicosis after working for several years.
Add 3%~5% sodium silicate into the pearl sand, mix the sand, fill the mixed sodium silicate pearl sand in the part a where the sand is easy to stick, and then fill the rest parts with sodium silicate quartz sand, and apply after hardening. After pouring, the casting is easy to clean and has high surface finish, which plays a role in preventing sand sticking.
In the local part of Fused Ceramic sand filling, it is easy to produce sintering, sand sticking and iron coated sand. After filling with Fused Ceramic sand, not only the phenomenon of sand sticking is changed, but also the phenomenon of casting cracks caused by poor yielding of sodium silicate quartz sand after sintering is eliminated. The use of Fused Ceramic sand in the internal included angle, groove, slender small hole hot junction and other parts of large steel (cast iron) castings that are easy to stick to sand can eliminate the local sand sticking or iron coated sand phenomenon, reduce the cleaning cost of castings, improve the performance quality of castings, and prevent cracks at the internal corners.
At present, Fused Ceramic sand can be directly used in sodium silicate sand molding, and its application in sodium silicate sand after mixing with chromite sand can also give play to the respective advantages of Fused Ceramic sand and chromite sand.
In addition to directly using CO2 hardened sodium silicate for molding, Fused Ceramic sand also has significant advantages in ester hardened sodium silicate and can greatly improve the tensile strength of ester hardened sodium silicate self-hardening sand. It can be expected that the amount of binder added in Fused Ceramic sand can be reduced by 30% ~ 50% on the premise of meeting the casting requirements.