| 摘要 |
PURPOSE:To prepare a steel plate for the spiral fin of a heat exchanger excellent in processability and high temp. oxidation resistance, by a method wherein steel with a specific composition is subjected to cold rolling and annealing under a specific condition after hot rolling and, after slits are formed thereto in a narrow width, the rooled steel is annealed under a specific condition. CONSTITUTION:Steel containing 0.15% or less C, 0.5% or less Si, 0.10-0.35% Mn 0.03% or less P, 0.01% or less S, 0.5-5% Cr, 0.01-0.08% Al and 0.0060% or less N is melted to be formed into a slab and this slab is hot rolled to be taken up at about 650 deg.C or less. After descaling, the rolled steel is subjected to cold rolling at a draft ratio of 40-70% and the cold rolled steel is annealed in an atmospheric gas containing 30% or more of H2 at a temp. range within a recrystallization temp.-700 deg.C. After the obtained steel plate is slitted in a narrow width, the slitted steel plate is annealed in an atmospheric gas containing 30% or more of H2 at a temp. range of 700 deg.C- an Ar3 transformation point. |
