| 摘要 |
PURPOSE: A method for manufacturing an alloy steel wire rod and bar for mechanical structural steel is provided, which is characterized in that a portion of ferrite and pearlite occupies more than 85 % in microstructure of the alloy steel wire rod by cooling rate on the course of control cooling after hot rolling, thus it can exclude quenching and tempering processes. CONSTITUTION: The method for manufacturing an alloy steel wire rod and bar for mechanical structural steel includes the steps of hot rolling a wire rod comprising C 0.2 to 0.6 wt.%, Si 0.1 to 1.0 wt.%, Mn 0.1 to 1.5 wt.%, at least one element selected from the group consisting of Cr 0.1 to 2.0 wt.%, Ni 0.1 to 5.0 wt.%, Mo 0.1 to 1.5 wt.% and B 5 to 200 ppm, a balance of Fe and incidental impurities; cooling the hot rolled wire rod to 700°C at a cooling rate of greater than 5 deg.C/sec; and cooling the hot rolled wire rod to 500°C at a cooling rate of less than 0.5 deg.C/sec, wherein ferrite+pearlite occupies more than 85 % in microstructure 260, vickers hardness of the alloy steel wire rod and bar is less than 260 and incidental impurities is characterized by comprised of 0.1 wt.% or less of Al, 0.01 wt.% or less of N, 0.02 wt.% or less of P, 0.02 wt.% or less of S.
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