METHOD FOR PRODUCING FROM CONTINUOUSLY CAST ROLLED BAR WITH SPHEROIDIZED STRUCTURE OF BORON STEEL FOR COLD BULK PRESSING OF HIGH-STRENGTH FASTENING PARTS

摘要

FIELD: metallurgy.;SUBSTANCE: method involves melting steel, with components being used in the following ratio, wt%: carbon 0.17-0.34; manganese 0.90-1.40; silicon 0.01-0.20; chromium 0.005-0.40; boron 0.0005-0.0050; titanium 0.01-0.04; sulfur 0.005-0.020; aluminum 0.02-0.06; calcium 0.001-0.010; nitrogen 0.005-0.015; iron and inevitable contaminants the balance, with following ratio being met: N/(Ti+0.5Al+10B)≤0.21; Ca/S≥0.065; deoxidizing discharged melt and alloying in ladle with the use of deoxidizers and alloying elements with low nitrogen content; at the stage of processing beyond furnace, alloying with titanium and boron in vacuumizer; pouring metal while protecting metal flow from contacting with air; cooling ingot and subjecting to hot rolling, with initial hot rolling temperature being within the range of 950-900⁰C and final hot rolling temperature being within the range of 850-740⁰C at deformation extent of at least 20% in outer passes; providing cold gauging deformation with following spheroidizing annealing by high-speed heating to temperature of A_s1+(10-30)⁰C and regulated cooling to temperature of 730-650⁰C at cooling rate of 0.5-1.0⁰C/min and further cooling in thermal chamber at medium temperature of 100-200⁰C.;EFFECT: provision for producing of rolled bars having structure allowing adequate cold bulk pressing conditions to be created for producing of compound-shaped high-strength fastening parts with increased hardenability characteristics of steel.;4 cl