Method of production of a steel tuble a very high resistance, with a remarkably ductility and a

摘要

P the present invention relates to the production of steel tubes. / p & & p & the method of the invention comprises the preparation of a blank of the tubes by hot extrusion of a steel containing 15,0 to 18,5% by weight of nickel, 12,5 to 15,0% by weight of cobalt, 5,0 to 6,9% by weight of molybdenum, 1,0 to 1,28% by weight of titanium, 0,01 to 0,20% by weight of aluminum, the remainder being iron, the cold working of this tube, the temperature rise to 800 - 950°C. in 20 minutes to 2 hours, the holding at this temperature for 30 minutes to 3 hours, the cooling down to or - below ambient temperature, and the vieilisseement at a temperature of 450 - 550°C. for 1 to 10 hours. / p & & p & the tube obtained has a tensile strength greater than 225 kg / mm * * 2. / p