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                                                               Talking about the Four Reasons for the Blackening of Valve Castings
In the field of machining, due to the particularity of valve castings, there will be blackening during use. Why? What are the reasons for this?
1. Internal reasons. Many valve casting manufacturers will not do any cleaning work after die casting and machining, and some even just use water flushing, which is difficult to clean thoroughly. Corrosive substances such as release agents, cutting fluids, saponification liquids and other stains remaining on the surface of the die casting will accelerate the blackening of the mold.
2. The impact of the external environment. Under certain conditions of temperature and humidity, the castings are prone to oxidative blackening or mildew, which is actually determined by the characteristics of the casting itself.
3. The process design is unreasonable. Improper handling of valve castings after cleaning or pressure inspection will create certain conditions for moulding and blackening of castings and accelerate the formation of mildew. Moreover, if the cleaning agent is selected to be highly corrosive, it may cause corrosion and oxidation of the casting.
4. The storage management is not in place. The castings are stored at different heights in the warehouse, and the mildew conditions are also different.

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