Improvements in or relating to sintered metal tubes

937,573. Powder metallurgy. COMMISSARIAT A L'ENERGIE ATOMIQUE. Feb. 24, 1961 [March 11, 1960], No. 6904/61. Class 82. A process for zone sintering a powder metal tube comprises forming a tube by extrusion or centrifuging a mixture of a powdered metal and a binder, inserting the " green " tube into a refractory tube which is inclined at an angle of 5-30 degrees to the horizontal, rotating the assembly at a speed corresponding to at least 1 revolution during the time required for sintering, and moving a hot zone along the outer tube from the bottom to the top of the tube to effect sintering of the inner tube. The clearance between the diameter of the inner and outer tubes should be at least 0.5 mm. and the speed of rotation should be at least 1-6 revolutions per head. The metal powders specified are iron, bronze and nickel and the binders are collodion, P.V.A. or gum tragacanth. As shown in the drawing, a metal powder tube 6 is inserted into a refractory or stainless steel tube 1 which is rotated. A clearance of 1 mm. is allowed between the tubes and the outer tube is evacuated or purged with hydrogen. An annular electric resistance furnace 8 surrounds tube 1 and during rotation of the tube the furnace is moved progressively along the tube to effect the sintering of the inner tube at a temperature of 600-1200‹ C.