PROCESS DEVELOPMENT OF REFRACTORY METAL INGOTS AND SHEET BAR.

Arc melting Ta-30Cb-7.5V was successful including electron beam melting purification, first arc melting and second arc melting. Sound, homogeneous ingots were produced. Major porblems were encountered while centrifugal casting Ta-30Cb-7.5V 6-in. diameter ingots. Only one pour produced a full sized ingot of which less than 50-percent was sound. Centrifugally cast Ta-30Cb-7.5V sheetbars were cast but contained centerline shrinkage. The sheetbars were warm rolled at 800 F, and the centerline porosity apparently healed. Tensile properties were obtained at room temperature and 1500 F. Arc melting Mo-1.25Ti-0.3Zr-0.15C into 8-in. diameter ingots was unsuccessful in that internal soundness was never achieved on a reproducible basis. Centrifugal casting Mo-1.25Ti-0.3Zr-0.15C did not produce sound 6-in. diameter ingots. Internal cracking was present in all parts cast. Presence of sound 2-in. thick lengths at the chill end led to the possibility of casting sheetbars for direct rolling. Centrifugal cast Mo-1.25Ti-0.3Zr-0.15C sheetbars 1-in. x 4.5-in. x 13-in. were cast in graphite molds. Internal centerline porosity existed. Rolling evaluation showed that internal porosity healed during hot working. Tensile testing was performed. Author