Method of highly-densifying powdered metal

Abstract

Abstract AN AIR-TIGHT CAN IS PREPARED FROM HEAT-RESISTANT MATERIAL, SUCH AS ORDINARY STEEL OR STAINLESS STEEL HAVING ON AT LEAST ONE END A TUBULAR STEM THROUGH WHICH THE CAN IS FILLED WITH THE POWDERED METAL TO BE COMPACTED. THE INTERIOR OF THE CAN IS THEN EXHAUSTED TO A HGIH VACUUM BY CONNECTING THE STEM TO A VACUUM PUMP, WHEREUPON THE STEM IS SEALED OFF AS BY WELDING WHILE MAINTAINING THE HIGH VACUUM. THE THUS POWDER-FILLED EVACUATED CAN IS THEN HEATED TO A HIGH TEMPERATURE WHICH IN ONE EXAMPLE WAS 2150* F. FOR ABOUT ONE HOUR. WHILE AT THAT HEAT IT IS PLACED IN THE DIE CAVITY OF A PRESS WITH THE STEM PROJECTING INTO A SUFFICIENTLY DEEP RECESS IN EITHER THE LOWER PUNCH OR IN THE UPPER PUNCH. THE UPPER PUNCH (AND IN A MODIFICATION ALSO THE LOWER PUNCH) IS MADE OF SMALLER DIAMETER THAN THE DIE CAVITY SO AS TO LEAVE AN ANNULAR CLEARANCE SPACE BETWEEN THE SIDE WALL OF THE DIE CAVITY AND THE PUNCH. THE UPPER PUNCH IS THEN LOWERED INTO THE DIE CAVITY IN A PRESSING STROKE WHICH FLATTENS THE CAN WHILE COMPRESSING THE METAL POWDER THERIN WITHOUT RUPTURING THE CAN OR LOWERING THE VACUUM THEREIN. AS THE COMPRESSION OF THE CAN AND ITS CONTENTS CONTINUES, AND THE DENSITY OF THE POWDERED METAL MASS APPROACHES 100 PERCENT, THE SIDE WALLS OF THE CAN DO NOT COLLAPSE, BUCKLE OR CRINKLE, AS HAS HITHERTO OCCURRED IN PRIOR ATTEMPTS AT COMPRESSING POWDERED METALS WITHIN CANS. INSTEAD, THE PERIPHERAL PORTION OF THE CAN AND ITS CONTENTS DEFORM AXIALLY INTO THE CLEARANCE SPACE BETWEEN THE PLUNCH AND THE DIE CAVITY SIDE WALL. IF THE PRESSING IS CONTINUED UNTIL THE DENSITY EXCEEDS 100 PERCENT, THE SURPLUS METAL POWDER AND THE PERIPHERAL PORTION OF THE CAN CONTINUE TO MOVE AXIALLY INTO THE ABOVE-MENTIONED ELEARANCE SPACE, THEREBY PRODUCING AN AXIALLY-PROJECTING LIP EXTENDING AROUND THE PERIPHERY OF THE CAN AND CONTAINING METAL POWDER AT A SOMEWHAT LOWER DENSITY THAN THE METAL IN THE REMAINING PORTION OF THE CAN. THE WALLS OF THE CAN ARE THEN REMOVED BY MACHINING OR BY PICKLING, TOGETHER WITH THE LESS DENSE PERIPHERAL PORTION OF THE NOW SUBSTANTIALLY SOLIDIFIED METAL DISC OR "PANCAKE."

Inventors

• 👤 John Haller

Bibliographic Details