PRODUCTION OF HEAT-INSULATING COMPOSITE PIPE BY TWO-STAGE CASTING

摘要

PURPOSE:To improve mechanical strength and operability by casting a molten metal for forming an outside layer into a centrifugal casting mold through one aperture thereof as the 1st stage and casting a molten metal for forming an inside layer into said mold through the other aperture as the 2nd stage. CONSTITUTION:A cylindrical core material P consisting of heat insulating fibers P3 are disposed between an outside core pipe P1 and a circular core pipe P2 having plural gas vent holes. These pipes and core material are grapsed by means of a 1st stage side ring and a 2nd stage side ring 42 and are fixed to the casting mold 1. The molten metal M1 for the outside layer is cast from a 1st stage side hopper 31 into a molten metal pool A1 while the mold 1 is rotated. The molten metal M1 is filled in a space C by which the outside layer is formed. The molten metal M2 for the inside layer is then cast therein from a second stage side hopper 32 and is filled in a space B, by which the inside layer is formed. Mixing of the molten metals M2 and M1 for the inside and outside layers is obviated and the change in the volume of the alloy components in the inside layer of the composite pipe is prevented by the above-mentioned method. Since the inside layer is cast before the formation of solid solution of the outside layer, the mechanical strength and operability are improved.