ROUND MERCHANT SHAPE MADE FROM MEDIUM-CARBON CHROMIUM-CONTAINING STEEL Russian patent published in 2006 - IPC C21D8/06 C22C38/24 

FIELD: metallurgy; production of merchant shapes for manufacture of spherical pins, end-pieces of rods and spherical supports for automobile suspensions.

SUBSTANCE: merchant shapes are molten from steel containing the following components, mass-%: carbon, 0.35-0.42; manganese, 0.50-0.80; silicon, 0.17-0.37; chromium, 0.80-1.10; sulfur, 0.020-0.040; vanadium, 0.005-0.020; calcium, 0.001-0.010; oxygen, 0.001-0.015; nickel, up to 0.25; copper, no more than 0.25; molybdenum, no more than 0.10; arsenic, no more than 0.08; nitrogen, no more than 0.015; the remainder being iron and unavoidable admixtures at oxygen-to-calcium ratio equal to 1-4.5 and calcium-to-sulfur ratio ≥0.065. Proposed merchant shapes contains nonmetallic inclusions of sulfide having double-layer structure; maximum contamination with nonmetallic inclusions pertaining to sulfides, oxides, silicates and nitrides does not exceed 3 points; it contains also structure consisting of 80% of granular pearlite; size of actual grain is 5-10 points at diameter ranging from 10 to 30 mm; provision is made for decarbonized layer not exceeding 1.5% of diameter, magnitude of cold upsetting is no less than 1/3 of height, rupture strength does not exceed 600 Mpa; relative elongation is no less than 18% and relative reduction in area is no less than 60%.

EFFECT: enhanced machinability at full hardenability of shapes up to 30 mm in diameter; retaining of technological ductility of steel.

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