Small knowledge of precision casting process

1) The pouring position should try to make the important large surface in a vertical or inclined state, which is conducive to the smooth filling of the molten metal and the gradual vaporization of the plastic pattern, so that the air gap pressure is small and the balance is maintained.


2) The pouring system preferentially selects closed bottom pouring, step pouring or side pouring to ensure the smooth flow of molten metal and avoid a large amount of air from entering the cavity during the pouring process.


3) Increase the pouring temperature of molten metal and reduce the pouring speed, which is conducive to the full vaporization and rapid discharge of the foamed plastic pattern. Practice has proved that increasing the pouring temperature can effectively reduce a series of casting defects such as porosity. The pouring temperature of steel castings should be above 1600℃. At this time, the coating should have high high temperature strength, otherwise it will cause serious sand sticking.


4) Adhere to the pouring principle of "slow-fast-slow". First, use a small flow of molten metal to point through the sprue, and quickly fill the sprue cup with a large flow to close the sprue to ensure the vacuum until the molten metal in the sprue cup does not sink. Estimated from the amount of molten steel poured in, when the liquid level is about to reach the top surface of the casting, slow down the pouring speed and reduce the flow of the molten metal to ensure that the gas in the molten metal or that may invade escapes the coating or precipitates from the molten metal.