| 摘要 |
PURPOSE: To minimize toughness difference between heat affected zone and steel matrix, TiN precipitates, which show superior thermal resistance, are homogeneously diffused in steel slab. CONSTITUTION: The method for manufacturing steel plate having superior toughness in weld heat-affected zone includes: (i) manufacture of a slab comprising C 0.03-0.17%, Si 0.01-0.5%, Mn 0.4-2.0%, Ti 0.005-0.2%, Al 0.0005-0.1%, N 0.008-0.030%, B 0.0003-0.01%, W 0.001-0.2%, P 0.03% or less, S 0.03% or less, O 0.005% or less, a balance of Fe and inevitable impurities, wherein the slab satisfies below inequalities: 1.2 <=Ti/N<=2.5, 10<=N/B<=40, 2.5<=Al/N<=7, 6.5<=(Ti+2Al+4B)/N<=14; (ii) hot rolling the slab at a reduction ratio higher than 40% within temperature range for austenite recrystallization after heating the slab in the temperature range 1100 to 1250deg.C for 60-180min; and (iii) cooling the slab at a cooling rate higher than 1deg.C/min to terminal temperature±10deg.C of ferrite transformation.
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