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

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

SUBSTANCE: method involves melting steel in electric furnace; processing beyond furnace; continuously pouring while protecting metal flow with argon; hot rolling of continuously cast bar and winding of rolled product into rolls. Melted steel contains, wt%: carbon 0.17-0.25; manganese 0.30-0.65; silicon 0.01-0.17; chromium 0.01-0.50; sulfur 0.005-0.020; vanadium 0.005-0.07; niobium 0.005-0.02; calcium 0.001-0.010, iron the balance, with following ratio being met: 12/C-Mn/0.02≥27; 0.46≥6xV+8xNb≥0.22; Ca/S≥0.065. Steel microalloying with vanadium inhibits steel recrystallization processes at rolling final temperature of 900-950⁰C and allows controlled rolling process to be provided, and microalloying with niobium - at steel heating temperature of 1,000-1,100⁰C to provide for fine-grained structure of austenite favorable for accelerated steel spheroidization process. Hot rolling of bars is initiated at temperature of 900-950⁰C and finished at temperature of 740-850⁰C at deformation extent of at least 20% in final passes. Upon completing of rolling process within temperature range of 600-730⁰C, rolled product is cooled at cooling rate of 5-20⁰C/min. Method allows additional spheroidizing annealing procedure to be omitted.

EFFECT: provision for producing of rolled bars having structure allowing adequate cold bulk pressing conditions to be created and improved steel deformability characteristics of continuously pressed bars to be provided.

2 cl, 1 ex