| 摘要 |
PURPOSE:To inexpensively prepare steel having high toughness and high strength, by successively applying hot rolling, quenching and tempering to steel containing C, Si, Mn, Mo, Ti, Nb, Ti and Al in a specific ratio under a specific condition. CONSTITUTION:Steel containing, on a wt. basis, 0.04-0.10% C, 1.0% or less Si, 0.50-2.00% Mn, 0.1-1.0% Mo, 0.005-0.5% Ti, 0.005-0.05% Nb, 0.01% or less B, 0.1% or less Al, according to necessity, one or more of 1% or less Cr, 0.1% or less V, 1% or less Cu and 0.01% or Ca and comprising the remaindr of iron and inevitable impurites are hot rolled at a heating temp. of 1,150 deg.C or more and a rolling finish temp. 850 deg.C or more. After rolling, the rolled steel is directly quenched to 200 deg.C or less and subjected to tempering heat treatment at a Ac1 point max. By this method, steel with tensile strength of about 80kg/mm.<2> is inexpensively prepared. |
