| 摘要 |
PURPOSE:To produce a hot-dip galvanized steel sheet excellent in workability by reducing the surface of a sheet of low-carbon Al-killed steel free from solid- solution N and successively carrying out spray coating with zinc alloy, cooling, and overageing treatment under respectively specified conditions. CONSTITUTION:The surface of a sheet of a low-carbon Al-killed steel (about 0.001-0.08% C) free from solid-solution N is reduced in a reducing atmosphere of about 750-850 deg.C, by which a surface oxide film is removed and the size of recrystallized grain is increased. Subsequently, after this surface is subjected to spray coating with a zinc alloy heated to 650-850 deg.C and having >=650 deg.C melting point, this steel sheet is cooled rapidly down to <=400 deg.C at an average cooling rate from 650 deg.C of >=50 deg.C/sec and then held at 200-400 deg.C for 2-10min to undergo overageing treatment. By this method, the hot-dip galvanized steel sheet excellent in workability and corrosion resistance can be produced with high productivity. |
