| 摘要 |
PURPOSE: A method for heat treating hot rolled 420-type martensitic stainless steel is provided to reduce a time required to transform austenite into a mixed phase of ferrite and carbide in a batch annealing furnace(BAF) by replacing a portion of carbon, a main constituent of cast segregation, with nitrogen. CONSTITUTION: In the heat treatment method of a 420-type martensitic stainless steel where the 420-type martensitic stainless steel is manufactured by reheating a martensitic stainless steel slab comprising C 0.05-0.15wt.%, Mn 1.0wt.% or less, P 0.045wt.% or less, S 0.045wt.% or less, Si 1.0wt.% or less, Cr 12-14wt.%, N 0.08-0.15wt.%, the balance Fe and inevitable impurities, and then it is hot roll followed by annealed, the heat treatment method includes: (i) hot rolling of a reheated martensitic stainless steel in conventional hot rolling temperature range; (ii) heating and maintaining the hot rolled martensitic stainless steel over an Ac1 temperature ranging from 850 to 870deg.C to form austenitic structure; (iii) heat treating the martensitic stainless steel in the temperature range of 700±25deg.C for 1-2hrs to transform austenitic structure to ferrite and carbide; (iv) annealing in a conventional manner.
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