ROLLED SECTION OUT OF MEDIUM CARBON BORON CONTAINING STEEL OF UPGRADED HARDENABILITY Russian patent published in 2008 - IPC C21D8/06 C22C38/60 

FIELD: metallurgy.

SUBSTANCE: invention refers to production of rolled section of a diameter from 40 to 170 mm for fabricating spline shafts, piston rods, traverses and other products. To achieve rational conditions of cutting at simultaneous upgrading of hardenability, plasticity and viscosity rolled section is fabricated out of steel containing elements, mas.%: C-0.38-0.43, Mn - 0.50-0.80, Si - 0.17-0.37, Cr - 0.70-1.00, S - 0.005-0.040, Mo - 0.03-0.06, V - 0.04-0.08, Al - 0.020-0.045, Ti - 0.020-0.045, B - 0.001-0.003, N - 0.005-0.012, As - 0.0001-0.03, Sn - 0.0001-0.02, Pb - 0.0001-0.01, Zn - 0.0001-0.005, iron and unavoidable impurities - the rest, at a following ratio of elements: (As+Sn+Pb+5×Zn)≤0.07: Ti/48+Al/27-N/14≥0.6×10^-3. Rolled section has a following macrostructure - central porosity, pointed nonuniformity, a liquation square - not more, than 3 points for each type, subshrinking liquation not more, than 2 points, liquation strips not more, than 1 point, steel dirtyness with nonmetallic inclusions: a medium point for pointed sulphides, pointed oxides, lined oxides, fragile silicates, plastic silicates, nondeformed silicates not more, than 3.5 for each type of inclusion. Rolled section has a laminar ferrite pearlite structure; the dimension of an actual grain is 5-9 points; mechanical properties are as follows: after hardening and low tempering σ_t not less, than 1300 MPa, σ_0.2 not less, than 1210 MPa, δ not less, than 10%, ψ not less, than 55%. Hardenability is as follows: hardenability of a sample at end tempering at a distance of 10 mm from the end is not less, than 47 HRC. Cutting machinability is as follows: wear value on the back edge of a cutting tool (h₃) at an equal cutting path (L) is at L=1320m h₃ is not more, than 0.30 mm.

EFFECT: provision of rational conditions for cutting machinability at simultaneous upgrading of hardenability, plasticity and viscosity.

3 cl, 2 ex