ROD OF MICRO-ALLOY MEDIUM-CARBON STEEL Russian patent published in 2007 - IPC C21D8/06 C22C38/24 C22C38/60 

FIELD: metallurgy, namely production of rolled bars such as calibrated round rods of medium-carbon micro-alloy steel with improved cutting ability used for making rods of automobile shock absorbers.

SUBSTANCE: rolled calibrated round rods are melted from medium-carbon micro-alloy steel containing next ingredients, mass %: carbon, 0.40 - 0.52; manganese, 0.40 - 0.95; silicon, 0.17 - 0.37; chrome, 0.01 - 0.025; sulfur, 0.020 - 0.045; vanadium, 0.005 - 0.02; aluminum, 0.03 - 0.05; calcium, 0.001 - 0.010; nitrogen, 0.005 - 0.015, nickel, no more than 0.25; copper, no more than 0.25; molybdenum, no more than 0.10; arsenic, no more than 0.08; phosphorus, no more than 0.030; iron and inevitable impurities, the balance while next relation is satisfied: calcium/sulfur is equal to 0.065 or more. Rolled piece has lamella type ferrite-pearlite structure with real size of grain 5 - 8 points and with diameter of rolled piece 10 - 30 mm. It has decarburated layer (ferrite + transition zone) consisting of no more than 1,5% of rod diameter, hardness of blank 229 - 255, temporary tensile strength no less than 640 MPa, percentage elongation no less than 6%, percentage narrowing no less than 30 %. Invention provides through calcination of rolled bars with diameter up to 30 mm.

EFFECT: improved cutting capability of steel at favorable relation of strength, ductility and viscosity, minimum anisotropy of mechanical properties at enhanced characteristics of calcination capability.

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