HIGH TOUGHNESS WEATHER RESISTANT STEEL AND WELD JOINT THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a weld joint with reducing toughness when a cooling speed is low and enhancing toughness of a bond part in an Fe-Mn-Si-Al-based weather resistant steel disclosed so far.SOLUTION: There is provided a weld joint made from an Fe-Mn-Si-Al-based high toughness weather resistant steel containing Al of 0.1 to 3.5 mass%, Si of 0.1 to 3.5 mass%, n of 0.4 to 2.5 mass%, C of 0.10 to 0.20 mass% and B of 0.0002 to 0.0055 mass% and the balance Fe with inevitable component and having a multi variant structure constituted by fine bainite having a micro metal structure with largely different crystal orientation, with time t, for which weld joint bond part temperature changes from 800°C to 500°C during welding, of 5 to 30 seconds, and having a bond part structure which is the multi variant structure.SELECTED DRAWING: Figure 3