WWW.07MET.TK Casting & Working of Metals Lab Manuals
PRACTICAL # 6 PRACTICE FOR MAKING PERMANENT MOLD CASTINGS
Overview: In permanent mold casting method, molten metal is poured into metal molds and around metal cores. The metal molds are coated with a mold surface coating and preheated before being filled with molten metal. A premeasured amount of molten metal is poured into the permanent mold under gravity. Permanent molds are made in two halves; they may be designed with vertical parting line or with horizontal line as in ordinary sand molding. The mold material is usually a good grade of cast iron, although die steel, graphite, copper, and aluminum are also being used. Cores for permanent molds can be sand, plaster, collapsible metal cores, or simply heavily tapered metal cores which are removed while the casting is still hot. Permanent mold castings have been made commercially of tin, zinc, lead, aluminum, magnesium, copper, and cast iron, and from their alloys. Higher production rates are obtained in permanent mold castings than sand casting.
Equipment:
A. Permanent Metal Mold B. Brushes
Chemicals / Materials: Aluminum scrap, refractory wash
Procedure: 1. Clean the mold by brushing or blasting with warm air. 2. Maintain it at proper casting temperature by a gas or oil flame. 3. Paint or spray the mold surface with a thin refractory wash or blacken it by depositing carbon from a reducing oil or gas flame. 4. Insert cores, if necessary and close the mold by hand or automatic action if available. 5. Pour the molten aluminum metal from the crucible into permanent mold. 6. Allow the sufficient time for the casting to solidify. 7. Then, open the metal mold and eject the casting from it automatically or by hand. 8. Finally, machine the casting to get the finished shape.
WWW.07MET.TK Casting & Working of Metals Lab Manuals