| 摘要 |
PURPOSE: A process for preparing high tensile strength steel having a low yield ratio of 80% or less and a tensile strength of 60kgf/mm¬2 even if a finish rolling temperature is raised by direct quenching at a finish rolling temperature of 900deg.C, heating and tempering at a lamelleriating temperature is provided, which improves productivity. CONSTITUTION: The titled steel is prepared by the process consisting of: forming a low alloy steel ingot; heating the ingot at 1,100 to 1,300; hot-rolling at a reduction ratio of 20% or more; cooling water to 300deg.C or less in the first time after finish rolling at 900deg.C or more; cooling to 300deg.C or less in the second stage; and cooling air to ordinary temperature after heating at 500 to 650deg.C, wherein the second half of hot rolling is carried out two or three times before finish hot rolling after the heating process.
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