Development and present situation of casting coating

1. Casting coating theory

(1) The mechanism of anti sticking sand, including sintering stripping theory, bright carbon theory and so on.

(2) In order to prevent the coating from cracking and peeling off, it is pointed out that the rapid thermal expansion of the coating and the sand mold (core) should be basically similar.

(3) Bingham model and Carson model.

2. Coating performance test

Baume reading: Baume hydrometer; viscosity: viscosity cup; density: baroid mud balance

3. Type of coating

(1) Water based quick drying coating: the thickness of the coating interface is generally 0.1-1mm, and the penetration depth is 2.5-4mm. The binder used in the coating is mainly water-soluble organic and / or inorganic binder.

(2) Transfer coating: called K-Y method. The coating can accurately duplicate the shape of the pattern or the inner cavity of the core box. It can obviously improve the dimensional accuracy of castings.

(3) Electrostatic powder coating: the principle of corona discharge is that the powder coating catches a certain electric charge in the corona discharge area at the head of the spray gun and is charged, and is sprayed on the surface of the sand mold under the action of electric field force and wind force. Refractory powder such as zircon powder, quartz powder and other particles are coated with a layer of resin binder (such as thermoplastic phenolic resin and hexamethylenetetramine) film.

(4) Base materials with metallurgical effect, such as tellurium, tin, chromium, aluminum, silicon, cobalt, etc.