How to solve the problem of air permeability in coated Sand Technology
The common defects and main causes in the process of using coated sand and the main causes of the name of the defect
(1) the loose surface of the mold (core) core pressure is too high or too low; the molded exhaust is not smooth; the mold runs because of the big clearance of the box surface; the fluidity of the resin coated sand is bad or the permeability is bad. Reasonable sand shooting pressure, improve the exhaust system, to prevent suffocating; the use of small deformation of the material for the core box; the use of good liquidity and permeability of coated sand.
(2) Unreasonable design of demoulding mold, the uneven temperature of the core box, low strength of the low-temperature part, the low melting point of resin coated sand, slow curing speed and low heat intensity. Improve the mold structure, so that the temperature distribution uniformity, select the high melting point, fast curing, high thermal strength of Resin.
(3) the casting air hole mold core exhausts are not free; the Resin Sand Gas volume is big or the gas speed is not suitable; the sand core solidifies is not thorough. Improve the exhaust system, improve the exhaust effect; choose a high concentration or coarse sand; use low-gas film coated matte process.
(4) The local strength of core-piercing sand core is low or loose; the crust thickness is thin. Improve the mold structure, make the temperature distribution uniform; select high melting point, fast curing speed, high heat intensity resin; adjust the sand pressure; improve the exhaust system.
(5) The content of Sio2 in sand adhered sand is low and the surface of the core is not dense. Adjust the jet pressure, improve the core box exhaust effect, make the core surface more compact; using high-temperature resin coated sand or zircon resin coated sand.
(6) uneven heating of the mold or the wall thickness of the mold may cause the shrinkage of the mold to be inconsistent during cooling The pouring pressure is too high to improve the mold structure, the temperature distribution is uniform, the molding tray is used to store the sand cores, the resin with low shrinkage rate is used to solidify, the resin with high-temperature resistance and low expansion is used to cover the film sand, the pouring system is improved (the non-pressure type is used) .
(7) The resin in the resin coated sand of the casting is burned at a high temperature to produce heat, which slows the solidification rate of Molten Iron and leads to shrinkage. The use of cooling type coated sand; in the shell, core placed cold iron.
(8) The Bright Carbon generated on the surface of the casting at high temperature is floating on the surface of the molten iron, and the surface of the casting is wrinkled when the casting solidifies. Phenol formaldehyde resin. Adding about 2% iron oxide powder, using high thermal conductivity of sand; core surface brush coating; coated sand with special accessories.