Casting shrinkage, porosity, mainly due to trachoma produced?
This is also called the subcutaneous needle stomatal stoma.Causes of shrinkage: in the process of cooling and solidification, the volume of molten metal contracts and the metal liquid is not effectively addedTrachoma causes: into the debris do not pay attention during the operation process; coating, casting, metal liquid core is washed out; a part of the casting process by the molten metal from the outside or the runner into the debris.
The pouring temperature of liquid metal solidifies the decision time is just the gas peak, such invasive gas is the solidification of casting.The causes of reactive pores: metal in the casting process, the molten metal or metal oxide, and the mold core (or coating) reaction gas is not discharged and the solidification of casting.
The causes of the three defects varyThere are three kinds of stomata: precipitation pore, invasive pore and reactive stoma. The cause of formation is differentThe reason for the formation of the porosity is that the metal liquid attracts too much gas during the smelting process, and then it does not take measures to remove the gas. During the process of pouring cooling, it will precipitate - usually the final cooling and solidification partsThe causes of blowhole: mold and core (including its coating) initiated too much (such as moisture and organic matter), and the permeability is poor.
