Improvements relating to the manufacture of metal strip

A process in which metal (e.g. Ni, Fe) powder is compacted into strip by passage between horizontal rolls arranged side by side (prior to sintering) is characterized in that the powder is a mixture of "A" and "B" powders the proportion of "A" being from 25 to 95 per cent by weight. "A" powder consists wholly or mainly of discrete, more or less rounded particles: "B" powder is wholly or mainly of a fibrous structure which may be formed from agglomeration of more or less rounded particles. These differences are most marked in carbonyl Ni and carbonyl Fe powders, the bulk densities of which are respectively "A" type 2 to 2.8 gm. per ccm; "B" type 0.6 to 1.4 gm. per ccm. Preferably rolls of diameter from 50 to 100 mm. are used, the compacted strip having a thickness between 0.1 and 0.25 mm. In an example, a mixture of 50 per cent each of the "A" and "B" Ni carbonyl powders is used, the bulk densities being 2.6 gm/ccm. and 0.9 gm/ccm respectively whilst the "A" particles are approximately 4 m and the "B" particles approximately 3 m in size. The mixture is compacted between rolls 66.7 mm. in diameter, at 3 meters per minute to form continuous strip 0.15 mm. thick and 50 mm. wide. The strip is passed directly through a tube furnace having a zone 0.6 m. long maintained at 900 DEG to 1200 DEG C. the atmosphere being hydrogen or cracked ammonia. The strip may then be cold-rolled in four or five stages with intermediate annealing treatments carried out by passage at 3 m. per min. through the sintering furnace maintained at 900 to 1200 DEG C. The thickness of strip may be reduced by 70 per cent and will be free from porosity.