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Gases In Metal Casting
Gases During The Manufacture Of A Casting
The molten metal used during the casting process may trap and contain gases. There are various reasons that gases are absorbed into the metal melt during manufacture. Turbulent flow of the casting material through the system may cause it to trap gas from the air. Gases may be trapped from material or the atmosphere in the crucible when the melt is being prepared. Gases may be trapped from reactions between the molten metal and the mold material.
Since liquid metal has a much higher solubility than solid metal, as the casting solidifies these gases are expelled. If they can not escape they may form vacancies in the material, causing porosity in the metal casting.
Whether a vacancy in a cast material is a result of gases or shrinkage is sometimes hard to tell. If the vacancies are spherical and smooth they are most likely a result of gases. Angular and rough vacancies are most likely a result of shrinkage. Gross absences of material within the metal casting are a result of shrinkage.
Prevention Of Gas Defects When Manufacturing A Part By Casting
The selection of proper materials is important in the design of a metal casting process. Here are a few things to remember when selecting manufacturing materials.