溶融亜鉛めつき工程における焼鈍前酸化促進処理によるシリコン含有鋼板のめっき性改善

摘要

The effect of accelerated oxidation prior to annealing on the galvanizability of 1.4 mass% Si-bearing steel was investigated. Oxidation process accelerated by ammonium sulfate improved the galvanizability of the steel under the oxidation condition where the steel without ammonium sulfate showed poor galvanizability: iron oxides containing more than 0.42 g·m~(-2) oxygen were found to improve the galvanizability. Iron oxides produced during accelerated oxidation prior to annealing improved the galvanizability because a continuous pure reduced iron layer formed on the surface of the steel was free of the surface segregation of silicon and manganese during annealing. This is because silicon and manganese were internally oxidized beneath the reduced iron layer as silica and complex oxides of silicon and manganese by oxygen in iron oxides. It is proposed that the amount of iron oxides required for the improvement of galvanizability is that of iron oxides which can supply that of oxygen required for capturing silicon and manganese as the internal oxides during annealing.%SiやMnなどの易酸化元素を含有する高強度鋼板素材の合金化溶融亜鉛めつき鋼板(GA)を溶融亜鉛めっきライン(CGL)で製造する場合には，めつき性劣化や合金化遅延といった課題を解決する必要がある.焼鈍の還元炉の前にNOF(Non-Oxidizing Furnace)を有する酸化還元型CGLでは，還元炉での焼鈍の前にNOFで鋼板を酸化させること(焼鈍前酸化)で上記課題を解決できることが報告されているははば.本技術では還元鉄中を成分元素が表面まで拡散しないように焼鈍条件を制御することが重要であると報告されており，また改善の機構として還元鉄中に成分元素の酸化物が分散することが挙げられている.