PROCESS FOR PRODUCING HIGH-STRENGTH COLD ROLLED STEEL SHEET EXCELLING IN CHEMICAL TREATABILITY AND RELEVANT PRODUCTION EQUIPMENT

摘要

A method using a continuous annealing furnace where a cooling method of a cooling zone including part or all of the temperature range of the steel sheet of 600 to 250°C following the heating for recrystallization is one or more of gas cooling, effusion cooling, and coaling pipe cooling, or a joint cold rolled steel sheet/hot dip galvanized steel sheet facility having such a contiguous annealing furnace, to continuously anneal cold rolled steel sheet to produce high strength cold rolled steel sheet, characterized by exposing the steel sheet surface to an iron-oxidizing atmosphere in the steel sheet temperature range to make the surface oxidize, pickling the sheet at the outlet side of the annealing furnace, then iron- or Ni-plating the sheet to 1 to 50 mg/m 2 .