Problems and Solutions of Furan Resin Sand Casting Sand Mould Brushing Coatings1.0

1. Paint buildup
reason:
1.11 The flow of paint is slow. Since paint is a thixotropic fluid, there is a network structure and yield value. Yield value and viscosity are the two main factors that cause the accumulation of paint. The yield value of the coating is too high and the viscosity is too large, resulting in poor fluidity of the coating.
1.12 The flow marks produced by the coating during the flow process flow along the sand mold, and when it encounters the grooves, it accumulates, resulting in unclear edges and corners of the sand mold.
1.13 The inclination angle of the sand mold is not suitable, the flow rate is small, and the paint does not flow down, causing accumulation.
1.14 Due to insufficient pressure, the flow rate is slow, resulting in accumulation.
Take measures:
1.21 Considering the on-site operation, the Baume degree of the coating should be reduced. It has been proved by practice that the fluidity of the paint is the best when the Baume degree of the flow coating is between 22-26. Considering the factors of the coating itself, it is necessary to reduce the yield value and viscosity of the coating.
1.22 Remove the flow marks by blowing with an air duct or with a brush dipped in thinner.
1.23 Sand mold placement angle requirements: use the crane to hoist the sand mold to the top of the coating tank and form an angle of 75-90 degrees with the horizontal for flow coating, increase the cross-sectional area of the flow coating rod head and the hose, in order to increase the flow, generally used flow coating The rod head and the hose are 4 pipes. If the cross-sectional area is increased, 4 pipes and 6 pipes can be used respectively, or both can be used with 6 pipes at the same time.
1.24 Increasing the wind pressure can increase the flow rate. In order to obtain a suitable coating thickness, the flow rate of the coating from the flow coater is preferably 100-200mm/s, and the wind pressure is generally between 0.4×105Pa-0.6×105Pa. If it is too large It is easy to produce splashes.

2. The coating thickness is not enough
reason:
2.11 The paint flows directly without forming a sufficient coating thickness.
2.12 The coating penetrates into the molding sand, resulting in insufficient coating thickness.
2.13 There is a release agent on the surface of the sand mold, which reduces the permeability of the coating and directly affects the thickness of the coating.
Take measures:
2.21 Increase the viscosity of the coating (the maximum value is not more than 7s), thereby improving the coating and hanging properties and avoiding excessive flow of the coating.
2.22 Improve the compactness of the sand mold, which can effectively avoid excessive penetration of the coating. The compactness of the sand mold is suitable between 45% and 55%.
2.23 The mold release agent on the surface of the pattern can be fully dried before production. The parts of the sand mold partially stained with the mold release agent are ground off with fine sandpaper and then flow-coated.

3. Thickness requirements for wet coating thickness of furan resin sand casting iron castings:
Thin wall casting 0.15mm-0.30mm Medium casting 0.30mm-0.75mm Thick wall casting 0.75mm-1.00mm Extra thick casting 1.00mm-2.00mm

4. The coating surface peels off
During the assembly process, when the operator blows the floating sand in the cavity with an air duct, the surface of the coating layer will occasionally fall off.
reason:
4.11 Coating strength is low.
4.12 The paint layers are not sufficiently combined to form a whole.
Take measures:
4.21 The small amount of binder in the coating will easily lead to insufficient coating strength, so it is necessary to increase the proportion of binder in the coating.
4.22 Insufficient combustion of the paint will easily affect the bonding between layers. For castings above 3 tons, the surface of the coating is prone to peeling off. This problem can be solved as long as the ignition time is reasonably controlled. Generally, 3-5 seconds after the upper box flow coating is suitable for ignition, and 5-7 seconds after the lower box flow coating is the best ignition. it is good. Gas fire can also be used for baking, but the time cannot be too long, otherwise the coating will crack.

5. Casting sticky sand
The refractoriness of the coating is not enough, and the coating or sand mold is in contact with the high-temperature molten metal to cause a chemical reaction, which makes the surface of the casting form a substance that is extremely difficult to clean, usually called sticky sand, and the flow coating method also produces sticky sand.
Solution:
5.11 Change the composition of coating aggregate and improve the refractoriness of the coating, choose high alumina bauxite powder, zircon powder and other refractory fillers.
5.12 Increase the thickness of the coating, but the thickness cannot exceed the required maximum thickness of the coating. Too thick will cause casting defects such as coating skin.
5.13 Improve the Baume degree of the flow coating coating, the highest is not more than 28, otherwise the fluidity will be reduced.
5.14 Some castings have local overheating phenomenon, and flow coating is very easy to stick to sand. Before flow coating, apply a coating with high refractoriness at the hot spot position, which can effectively prevent sand sticking.

Qingdao Sanzhuji Equipment Manufacturing Co., Ltd. specializes in the production of Green Sand Molding Line,Self-hardening sand molding line,foundry machines,Sand molding machine,Sand casting equipment,sand mixer,GS high efficiency rotary mixer,Resin sand mixer,no-bake resin sand mixer,Jolt squeeze molding machine/Jolt-squeezing moulding machines,Multi- Piston Moulding Machine/Hydraulic multi-piston moulding machine,sand casting molding machine,sand reclamation equipment，foundry molding machine,flaskless moulding machine,shot blasting machine,dust collector,according to the amount of old sand recovered Carry out plan customization, and provide sand reclamation equipment installation, commissioning, and training. Welcome guests to visit the factory.