PROCESS FOR APPLYING AN INSULATING LAYER

摘要

A process is disclosed for applying to sheet steel an electrically insulating layer whose main purpose is to permit a satisfactory welding of the sheets when they have been blanked and stacked. The sheet steel is contacted with a treating liquor which contains a resin adapted to be diluted in an alkaline aqueous medium, and a fluoride of a polyvalent metal, particularly aluminum fluoride, in an amount of 0.1 to 80 parts by weight per 100 parts by weight of resin. The treating liquor is subsequently dried and the sheet is subjected to a stress-relieving annealing, if required. In accordance with a preferred embodiment, the treating liquor additionally contains borates and/or dispersed particles made of silicate and/or polymers, and is applied by means of rollers before being dried at 120 to 350.degree.C.