EXTRA THIN-WALL TUBE FROM AUSTENITE BORON-CONTAINING STEEL FOR COVER OF FUEL ELEMENT, AND METHOD FOR ITS MANUFACTURE Russian patent published in 2011 - IPC C21D8/10 C21D6/00 C22C38/58 

FIELD: power industry.

SUBSTANCE: tube is made from steel containing components at their following ratio, wt %: carbon 0.05-0.09, silicium 0.3-0.6, manganese 1.0-2.0, sulphur not more than 0.010, phosphorus 0.010-0.025, chrome 15.0-16.5, nickel 18.0-25.0, molybdenum 1.9-2.5, titanium 0.25-0.45, niobium 0.1-0.4, vanadium 0.1-0.15, boron 0.001-0.005, cerium 0.15 is design; ferrum is the rest; at that, at 700°C at single-axis axial tension it has long-term strength of 14.0-15.0 kg/mm at test period of 10000 hours and steady-state creep at stress of 14 kg/mm², which is equal to (1.0-1.1)×10^-4%/h. Tube manufacturing method involves cycles of heating and hot deformation of ingot, tube workpiece and cold deformation of workpiece with further heat treatments and final cold deformation; at that, prior to hot deformation on the ingot and during tube conversion the homogenising annealing is performed at temperature which is by 40-110°C less than temperature of formation of boride eutectic, but higher than the temperature at which boron content in solid solution is not less than 20 ppm (20×10^-4 wt %).

EFFECT: improving long-term strength, reducing creep speed and deformation of covers of fuel elements at irradiation owing to improving swelling resistance.

3 cl, 3 dwg, 2 tbl, 1 ex