STRENGTH STEEL HAVING AN HAZ WITH EXCELLENT TOUGHNESS, AND A MANUFACTURING METHOD THEREOF, CAPABLE OF INCREASING THE TOUGHNESS OF WELD ZONE

摘要

PURPOSE: Strength steel having an HAZ(heat affected zone) with excellent toughness, and a manufacturing method thereof are provided to reduce the content of MA(Martensite Austenite Constituent) and free nitrogen such that the toughness of weld zone increases.;CONSTITUTION: Strength steel having an HAZ(heat affected zone) with excellent toughness contains C 0.03~0.19wt.%, Si 0.01~0.5wt.%, Mn 0.4~2.0wt.%, Ti 0.005~0.2wt.%, Al 0.1~1.2wt.%, N 0.006~0.025wt.%, O 0.002~0.008wt.%, B 0.0003~0.005wt.%, less than 0.03wt.% P, less than 0.03wt.% S, residual Fe, and inevitable impurities. The Ti, N, B, Al, and O satisfy following formulas. 1.2ΔTi/NΔ2.5, 10ΔN/BΔ40, 10ΔAl/NΔ100, 35ΔAl/OΔ190, 40Δ(Ti+Al)/OΔ200, 10Δ(Ti+Al+4B)/NΔ110.;COPYRIGHT KIPO 2012