A COATED CAST IRON CRUCIBLE FOR USE WITH EUTECTIC Al-Si ALLOY IN THE TEMPERATURE RANGE 595-650 C

The feasibility of the coated metal crucible as a container for eutectic Al--Si alloy was proven by test. Small enamel-coated east-iron pets have successfully withstood Al-- Si alloys and an oxidizing atmosphere for a period of 3 months at 725 deg C. A similarly coated east-iron crucible containing 450 pounds of eutectic Al--Si alloy was successfully tested for 144 days in a jacketing operation conducted at 595 deg to 650 deg C. Under the same conditions, the normal service life of clay-bonded graphite and silicon carbide crucibles rarely exceeds 45 days. The coating material for the iron crucible is a commercially available enamel capa ble of withstanding temperatures up to 790 deg C. lt is readily applied to the surface of a variety of ferrous metals and alloys; however, best results are obtained with alloys low in chromium and nickel which also have a low thermal expansion coefficient. (auth