| 摘要 |
PURPOSE: To improve both toughness of weld heat affected zone and strength of steel plate, TiN+CuS precipitates are homogeneously formed in steel plate that is designed to have a complex microstructure of pearlite and ferrite with a grain size smaller than 20μ m. CONSTITUTION: The method for manufacturing high strength steel plate having superior toughness in weld heat-affected zone includes: (i) heating a steel slab in the temperature range of 1100 to 1250deg.C for 60-80min wherein the steel slab comprises 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%, Cu 0.1-1.5%, P 0.03%or less, S 0.003-0.05%, O 0.005% or less, a balance of Fe and other inevitable impurities, and further satisfies following equations: 1.2<=Ti/N<=2.5, 10<=N/B<=40, 2.5<=Al/N<=7, 6.5<=(Ti+2Al+4B)/N<=14, 10<=Cu/S <=90; (ii) hot rolling of the heated steel slab within the temperature range for austenite recrystallization at a reduction ratio higher than 40%; and (iii) cooling the hot rolled slab to terminal temperature±10deg.C for ferrite transformation at a cooling rate 1deg.C/min. Further, the steel slab comprises (i) one or two element selected from Ni 0.1-3.0%, Cu 0.1-1.5%, Nb 0.01-0.1%, Mo 0.05-1.0%, Cr 0.05-1.0%; (ii) one or two selected from Ca 0.0005-0.005%, Rem 0.005-0.05%; and (iii) V 0.01-0.2%, wherein V/N is 0.3-9, 7<= (Ti+2Al+4B+V)/N<=17.
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