Patent ID: 7181847

Claim:
A process for the manufacture of a cylindrical hollow body with circular cross-section from solid rough material of corrosion-resistant, martensitic chromium steel, comprising providing a remelting block of the chromium steel; making a tube blank having an axial borehole from the remelting block; shaping the tube blank into a tube at hot forming temperature by extrusion at a deformation ratio of at least 6; and cutting the hollow body from the tube; wherein the steel comprises, in weight percent: from 12 to 29 chromium (Cr); from 0.02 to 5.9 molybdenum (Mo); from 0.05 to 0.8 carbon (C); from 0.15 to 0.8 nitrogen (N); provided that the sum (C+N) is not higher than 1.4.