| 摘要 |
PROBLEM TO BE SOLVED: To provide a weatherproof steel capable of forming a dense weatherproof rust in an early stage even in a coastal area and its production. SOLUTION: This weatherproof steel is a steel having a composition consisting of, by weight, 0.01-0.3% C, 0.05-0.5% Si, 0.3-2% Mn, 0.005-0.1% sol.Al, 0-1.5% Cr, 0-0.6% Mo, 0-0.5% Ni, 0-1% Cu, 0-0.1% Nb, 0-0.1% Ti, 0-0.1% V, and the balance Fe with inevitable impurities and also having a structure composed of mixed phases of two or more phases, and further, the difference of average hardness between hard phases and soft phases is 80-200 Vickers hardness and the average spacing between mutual hard phases is <=50μm. This process of producing the weatherproof steel comprises hardening treatment from a two phase state of ferrite and austenite.
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