The performance indexes of zirconium free composite cast steel coating 405B (hereinafter referred to as tl405b) are shown in the table below.
|Paint||Applicable material||Baume degree (° B é)||Specific gravity /g · ml-1||24h suspension (%)||Gas evolution /ml · g-1|
Tl405b is a coating product suitable for steel castings with fused corundum powder as the main aggregate. It can be used after being fully stirred, diluted with an appropriate amount of alcohol, and evenly stirred. It is suitable for steel castings with brush coating, flow coating and spraying processes. The coating has a Baume degree of 60 ° B é for 4 hours, and the suspension is more than 98%. The gas evolution at high temperature is lower than the industry standard. It is suitable for the production of high-end steel castings.
In the composition of cast steel coating, the refractory aggregate, carrier liquid, binder and suspending agent of cast steel coating were screened according to the material of casting and the characteristics of adhesion, leveling, coating and suspension stability of cast steel coating.
1. Refractory aggregate
Fused corundum powder is mainly used as refractory aggregate. The content (mass fraction) of Al2O3 in fused corundum powder is 99%. It has good chemical stability and high purity. It will not decompose other substances to form low melting point substances, which is helpful to improve the coating performance of cast steel and the smoothness of castings.
2. Carrier liquid
In order to reduce the cost of traditional casting alcohol based cast steel coatings, methanol will be widely used as the solvent carrier. At present, some industrial alcohol used in many casting factories is also methanol solvent. However, methanol is toxic and may cause contact or inhalation injury to workers. From the perspective of environmental protection and occupational health, we should adhere to the selection of industrial ethanol that makes the binder in cast steel paint more soluble and non-toxic, and use isopropanol with better flammability in proportion. Ethanol and isopropanol were mixed as the carrier liquid of composite cast steel coating.
The selection of binder adopts the combination of phenolic resin and inorganic binder. Phenolic resin has good low-temperature bonding performance and low gas evolution. Inorganic binder mainly ensures the adhesion and erosion resistance of cast steel coating at high temperature.
4. Suspending agent
The suspending agent can help stabilize the properties of cast steel coating and further improve the overall rheological properties. Traditional suspension agents such as organic bentonite, lithium bentonite and organic rectorite are mostly used to stabilize the suspension by thickening the carrier, which often has a great impact on the viscosity. In recent years, the research and test of crystalline hydrated magnesium aluminosilicate minerals with unique layer chain structure have shown a good application effect. Although the expansion performance of these minerals is not high, the special fibrous or rod structure makes them have unique rheological properties, which can significantly improve the thixotropic and brushing properties of cast steel coatings.