Granges Nyby Ab

Peter Nilsson

Christer Aslund

A process for the after-treatment of powder-metallurgically produced extruded tubes of stainless steel or highly alloyed nickel steels, pressings initially being produced by introducing into a capsule of thin sheet steel a powder consisting predominantly of spherical particles which have been produced from the required starting material by sputtering and, after the capsule has been closed, the density of the powder is increased to at least about 80% to about 93% of the theoretical density by cold isostatic pressing and the pressings obtained are then extruded into tubes at temperatures around 1200.degree. C. using glass as the lubricant and the extruded tubes still surrounded by the capsule are initially treated with aqueous sulphuric acid to remove the glass still present on their surface, subsequently cold-worked by drawing or reciprocating rolling and, after cold-working, are annealed in an oxidising atmosphere until the capsule has been converted into scale to such an extent that a surface free from capsule residues is obtained after pickling with mild pickles.

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Aby, Sweden

Peter Nilsson