METHOD FOR PRODUCING OF SPHEROIDAL ROLLED BAR FROM LOW-CARBON STEEL FOR COLD BULK PRESSING OF COMPOUND-PROFILED FASTENING PARTS Russian patent published in 2004 - IPC

FIELD: metallurgy, in particular, production of rolled parts of specifically complex shape from low-carbon steel.

SUBSTANCE: method involves melting steel in electric furnace; providing processing beyond furnace; pouring into casting molds while providing protection of flow; hot rolling of ingots and obtaining blank; providing controlled rolling of blank; winding rolled product into rolls; gauging rolled products at deformation extent of 15-20% and providing spheroidizing annealing process; melting steel at following ratio of components, wt%: carbon 0.27-0.32; manganese 0.30-0.65; silicon 0.01-0.25; sulfur 0.005-0.020; niobium 0.005-0.02; calcium 0.001-0.010; iron the balance, with following ratios being provided:12/C - Mn/0.03 equal to or exceeding 20; Ca/S equal to or exceeding 0.065. Process of microalloying of steel with niobium inhibits steel recrystallization process at rolling finishing temperature of 950-1,000⁰C to allow controlled rolling on existing equipment and formation of fine-grained structure. Spheroidizing annealing process is performed by high-speed heating of cold deformed metal at intercritical temperature range, followed by regulated cooling within temperature range of 650-730⁰C at cooling rate of 1.0-1.5⁰C/min and further cooling in thermal chamber at temperature of cooling medium of 100-150⁰C. Method allows spheroidizing process time to be reduced by 5-10 times.

EFFECT: increased efficiency and provision for producing of rolled bars having structure providing adequate conditions for cold bulk pressing of compound profiled high-strength fastening parts from steel with improved ductility and toughness.

2 cl, 1 ex