Extrusion at Temperatures Approaching 5000 degs F
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
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Development of refractory metal alloys having high strength at temperatures in excess of 3000 degrees F requires methods of ingot breakdown or working at temperatures much higher than the use temperatures. Extrusion generally has been the most successful method. However, extrusion containers and other tooling melt in the temperature range 2400 degrees to 2600 degrees F and since maximum retention of billet temperature is desired, special handling methods are necessary. Accessories to permit extrusion at ultrahigh temperatures have been developed for a 1020-ton vertical extrusion press. These include a high-temperature atmosphere furnace, a rapid billet transfer device, an extrusion straightener, and an eight-tube extrusion retriever. The furnace permits heating for extrusions in either inert gas or hydrogen atmospheres to 5000 degrees F. The rapid billet transfer device currently permits an average extrusion time from furnace opening until extrusion is completed of 5 seconds. The straightener enables extrusions of refractory metals to be made with deviations of less than 14 inch from straightness over an 8-foot length. An extrusion retriever facilitates the removal of extrusions from the extrusion pit. Effects of various lubricants on extrusion quality have been observed but have not been definitely determined. The best quality extrusions have been obtained by the use of a calcium graphite grease for an extrusion temperature range of 1500 degrees to 2300 degree F. For an extrusion temperature range of 3000 degrees to 5000 degrees F, glass cloth impregnated with tungsten disulphide was best. Although extrusion quality has not been consistently good with these lubricants, a good yield of acceptable experimental materials has been obtained.
- Metallurgy and Metallography