High tension steel with high cold notch toughness - for making petroleum or natural gas pipe lines for use in freezing zones

摘要

High tension steel for low temp. use, comprises C 0.01-0.20%, Si 0.005-0.50%, Mn 0.30-2.50%, P =0.020, S 0.006%, Ni 0.30-6.0%, Cr 1.0%, Mo =0.50%, soluble al 0.005-0.150%, and balance Fe. Yield point in cross rolling ratio 10 is 50kg/mm2, C direction (at right angles to direction of rooling) vTres of Charpy test is less than - 75 degrees C, C direction of DWTT test (plate thickness 20mm) being 85% ductile brittle transition temp. less than - 30 degrees C and anisotropy of vTrs is less than 0.20. The alloy is used in constructing pipelines for transportation of petroleum or natural gas in freezing zones and has excellent cold notch toughness in the C direction.