ArcelorMittal S.A.
METHOD OF PRODUCING PRESS-HARDENED AND COATED STEEL PARTS AT A HIGH PRODUCTIVITY RATE

Abstract:

A fabrication method for a press hardened part is provided. A sheet or a steel substrate blank for heat treatment is provided. A pre-coating is applied. The pre-coating has at least one layer of aluminum or aluminum alloy in contact with the steel substrate on at least one of the principal faces of the sheet or blank. Then a polymerized layer is deposited on the pre-coating. The polymerized layer has a thickness between 2 and 30 .mu.m. The polymerized layer does not contain silicon, has a nitrogen content of less than 1% by weight and carbon pigments in a quantity between 3 and 30% by weight. The blank or the sheet is heated to obtain an interdiffusion between the steel substrate and the pre-coating and to give the steel a partly or totally austenitic structure. Then the blank or the sheet is hot stamped to obtain a part. The part is cooled by holding the part in a stamping tool so that the microstructure of the steel substrate includes, at least in a portion of the part, martensite or bainite.