TUBE STOCK OUT OF LOW CARBON HEAT RESISTANT STEEL Russian patent published in 2008 - IPC C21D8/10 C22C38/60 C22C38/48 

FIELD: metallurgy.

SUBSTANCE: invention refers to production of tube stock of 80-180 mm diameter. To facilitate optimum ratio of hardness, plasticity and viscosity, of minimal level of anizotropy of mechanical properties, and also of upgraded properties of weldability and reduced tendency to temper brittleness a tube stock is fabricated out of steel containing elements wt %: carbon 0.08-0.15, manganese 0.40-0.70,silicon 0.40-0.70, chromium 1.60-1.90, vanadium 0.20-0.35, boron 0.0002-0.005, molybdenum 0.50-0.70, nickel 0.005-0.25, titanium 0.001-0.03, aluminium 0.01-0.06, sulphur 0.005-0.025, phosphorus 0.005-0.025, nitrogen 0.005-0.010, arsenic 0.0001-0.03, tin 0.0001-0.02, lead 0.0001-0.01, zinc 0.001-0.005, iron and unavoidable impurities - the rest, at maintaining of ratio N/(Ti+0.5×Al+10×B)≤0.21, (As+Sn+Pb+5Zn)≤0.07. As impurities steel contains (wt %) niobium not more, than 0.02 and copper not more, than 0.30. The tube stock is continuous cast and hot-rolled, it has laminar ferrite-pearlite structure and dimension of actual grain 6-9 points. On macrostructure it has central porosity, pointed non-uniformity, liquation square and sub-shrinking liquation not more, than 3 points in each kind, liquation strips not more, than 2 points. On non-metallic inclusions it has sulphides, pointed oxides, stripped oxides, fragile silicates, plastic silicates, non-deformed silicates not more than 4.0 points in each kind of inclusions, tensile strength 490-690 N/mm², yield point not less, than 275 N/mm², specific elongation not less, than 21%.

EFFECT: facilitating of optimum ratio of hardness, plasticity, and viscosity, minimal anisotropy of mechanical properties and also upgraded characteristics of weldability and reduced tendency to temper brittleness.

1 cl, 1 ex