F - Foundry Additives Glossary
FACINGS (See: FACING SAND-FOUNDRY FACING)
These are coating materials generally applied to the surface of cores or molds to protect the core or molding sand from the heat, the oxide and the chemical actions of the molten metal. Seacoal, blackings, carbons, pitch, gilsonite and others are commonly called, "facings." However, these carbons are additives to molding sand mixtures, which in a way, act only like a "facing." (Also See: BLACKINGMOLD COATINGS-PLUMBAGO FACINGS.)
FACING SAND (See: FACINGS-MOLDING SAND-SAND)
A sand mixture that is used as the interface refractory plane between the metal and the molding sand. It is the closest sand to the pattern and is often especially prepared for specific casting properties.
FERRIC OXIDE (See: HEMATITE-IRON ORE-IRON OXIDE KLEAN SURF)
This is the chemical name given to "iron oxide" or "hematite ore." Its chemical composition is [Fe2O3]. It is abundantly found in nature. Certain of the iron ores are used by the foundry industry as an iron oxide addition. From 0.5% to 6.0% iron oxide is added to sand mixtures. Iron oxides of different trade names generally function completely different in core and melding sand mixtures. The specific gravity of chemical grade ferric oxide varies from 4.0 to 5.2, but the mosi: popular foundry grades have a lower specific gravity and are between 3.0 to 4.5. These oxides contain mineralizers. When iron oxide is used for only its pigment value, it is often called "rouge." Iron oxides vary in color from a brown-red, to a purple-red, to a reddish-black, or even to a black texture. One of the better commercial ferric oxides is known as "Klean Surf." Iron oxide (Fe2O3) is non-magnetic and difficult to reclaim from a sand system or heap. Build-up of Wilstite (FeO), ferrous oxide, in the sand system or heap after casting may become a problem, if no new sand additions are made regularly.
1. The quality of the iron oxide is judged by its source, availability, chemistry, pH value, color, screen analysis, bulk density, and its economical value. Specifications should be established on all these properties when ordering.
2. Finely ground iron oxide is a useful inorganic mineral additive giving unique properties to sand mixtures when casting at higher temperatures than 600°F. (316°C.). Iron oxide increases the hot plasticity or hot deformation of the molding or core sand mixtures at higher temperatures. In some cases, it compensates for the high sand expansion created by other materials in the sand mixture. Klean Surf oxide neutralizes sudden volume changes in a sand mixture when heated.
3. The addition of iron oxide to a sand mixture decreases veining, metal penetration or burn-on. Thus, it reduces cleaning costs of the casting.
4. Iron oxide or ferric oxide is not a "cure-all" for poor foundry sand practice. It is a useful mineral when used correctly in 0.5 % to 6.0% additions.