Interaction of Chemically Active Melts With Ceramic Mold Materials in Vacuum

Abstract

To obtain precise castings from chemically active melts, a special method of precision cas¬ting according to removable models is traditionally used, consisting in the manufacture of ceramic molds on an ethyl silicate binder and further filling with melt in vacuum. At the same time, when forming castings of a responsible purpose by pouring titanium and heat-resistant nickel alloys in a vacuum, the current technology causes a high defect due to the identification of various surface casting defects that are unacceptable when working parts under the action of repeatedly repeated temperature changes and alternating mechanical loads. The analysis showed that the main reason for this defect is the lack of thermochemical resistance of ceramic corundum molds on an ethyl silicate binder to interaction with poured titanium and heat-resistant nickel al-loys in vacuum. The possibility of obtaining high-quality castings from chemically active alloys is reduced to the use as a binder of ceramic forms of materials that are resistant to thermal dissociation in vacuum at heating temperatures of 1913–1973 K. For this purpose, it is proposed to use a silica-free binder – an aqueous solution of aluminum phosphate concentrate. The composition of the mold made according to the proposed technology, in which there is no silica, excluded the harmful effect of oxidation processes in vacuum on the quality of castings from chemically active alloys. Ceramic electrocorundum molds based on aluminum phosphate concentrate are resistant to thermal dissociation and interaction with chemically active metals poured in vacuum. This will reduce defects in non-metallic inclusions and improve the quality of precision castings made of titanium and heat-resistant nickel alloys.