ROUND HOT-ROLLED BAR STOCK Russian patent published in 2013 - IPC C21D8/06 C22C38/00 C22C38/18 C22C38/22 C22C38/40 

FIELD: metallurgy.

SUBSTANCE: hot-rolled bar stock is obtained from steel containing the following components, wt %: carbon 0.31 - 0.35, manganese 0.75 - 0.95, silicon 0.30 - 0.45, chrome 0.80 - 1.2, molybdenum 0.50-0.65, nickel 0.30 - 0.50, aluminium 0.015-0.040, iron and inevitable impurities: sulphur of not more than 0.010, copper of not more than 0.20, phosphorus of not more than 0.015, and nitrogen of not more than 0.010. Rolled stock has macrostructure: central porosity, point non-homogeneity, segregation square of not more than 2 points for each type, sub-shrinkage segregation of not more than 1 point; the following is excluded: freckle-type segregation, edge freckle-type segregation, subsurface pinholes, intergranular cracks, non-metallic inclusions: oxides and silicates of not more than 4 points, non-deformable silicates of not more than 4.5 points, and sulphides of not more than 4 points. Size of austenitic grain comprises maximum 6 points. Rolled stock is subject to heat treatment by heating to 670-690°, exposure during 22 hours, cooling in the furnace to 600°, and then, cooling in the air so that the following mechanical properties are obtained: ultimate strength of not less than 1050 N/mm², yield strength of not less than 950 N/mm², relative elongation of not less than 15%, relative constriction of not less than 55%, impact strength of not less than 111 J/cm², and hardness of not more than 255 HB.

EFFECT: providing high mechanical properties.

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