Low temperature toughness of the heat affected zone of weld and the tensile strength is excellent and a method of manufacturing the high-strength structural steel

摘要

A structural high intensity steel and a manufacturing method thereof are provided to have enough toughness and intensity by controlling the structure of the steel with the structure consisting of polygonal ferrite, pearlite or degenerated pearlite. A structural high intensity steel comprises follows. The inner structure is consisting of polygonal ferrite whose average grain size is 5mum or less, and pearlite or degenerated pearlite whose average grain size is 10mum or less. The area fraction of the polygonal ferrite is 95% through 70. The area fraction of the pearlite or the degenerated pearlite is 30% through 5. The structural high intensity steel having the superior low temperature toughness and the tensile strength of a weld heat-affected part includes one kind or two kind selected from a group consisting of Cr: 0.05~1.0 weight%, Ni: 0.01~2.0 weight% or Cu: 0.01~1.0 weight%.