Causes of too high carbon content in precision castings
1. The pouring conditions of alloy steel castings are s […]
1. The pouring conditions of alloy steel castings are set unreasonably: if the pouring filling process is set too long, the temperature of the molten steel is low during the pouring process, especially where the wall thickness of the casting increases, and the solidification rate of the molten steel is slow. As a result, the liquid-solid residence time is longer, which promotes the increase of the action time of the molten steel and the thermal decomposition products of the pattern, and increases the carburizing and carbon deposits of the cast steel.
2. The carbon content in the smelting ingredients for the production of alloy steel castings is not strictly controlled, especially the carbon content in various scrap steels and whether there are other alloy components in the various scrap steels.
3. The setting of the casting system of alloy steel castings is unreasonable: especially the configuration of the vacuum pumping system and the casting flask, or the casting process molding configuration is unreasonable, causing the vacuum degree in the casting flask to vary during the casting process of precision castings , The deviation is too large, or the actual vacuum is insufficient, and the vacuum pressure gauge shows an incorrect value that meets the technical parameter requirements, so that the thermal decomposition products of the pattern cannot be quickly and quickly discharged from the casting cavity, causing carburization or carbon deposition of the casting.