CTOD THICK STEEL SHEET HAVING EXCELLENT CTOD PROPERTIES IN MULTILAYER WELDED JOINTS AND MANUFACTURING METHOD FOR THICK STEEL SHEET

摘要

A multi-layered welded joint of small to medium heat welded joints with excellent CTOD characteristics and a method of manufacturing the same. Wherein the composition of C is 0.03 to 0.10%, Si is 0.5% or less, Mn is 1.0 to 2.0%, P is 0.015% or less, S is 0.0005 to 0.0050%, Al is 0.005 to 0.060% 0.001 to 0.0050% of Ca, 0.0005 to 0.0060% of Ca, and at least one of Cu and the like, if necessary, in the range of 0.5 to 2.0%, 0.005 to 0.030% of Ti, 0.0015 to 0.0065% In the specific range of values of Ti / N, Ceq, Pcm and ACR, the effective grain size of the base material in the center of the plate thickness is 20 탆 or less, And a composite inclusion having a circle-equivalent diameter of not less than 0.1 탆 is present in a specific amount. The steel of the above composition is heated at a specific temperature, then hot-rolled and cooled.