PRE-COATED STEEL SHEET COMPRISING AN ADDITIONAL COATING FOR INCREASING THE MECHANICAL STRENGTH OF THE WELD METAL ZONE OF A WELDED STEEL PART PREPARED FROM SAID PRE-COATED SHEET

• Main Authors: MACWAN, Andrew, ZHOU, Yunhong (Norman), BIRO, Elliot, GERLICH, Adrian Piotr, SAHA, Dulal Chandra, KHAN, Shehryar
• Format: Patent
• Language: English; French
• Published: 01.07.2021
• Subjects: CHEMICAL SURFACE TREATMENT; CHEMISTRY; CLADDING OR PLATING BY SOLDERING OR WELDING; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATIONOR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY IONIMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; COATING MATERIAL WITH METALLIC MATERIAL; COATING METALLIC MATERIAL; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; DIFFUSION TREATMENT OF METALLIC MATERIAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION INGENERAL; MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR; METALLURGY; PERFORMING OPERATIONS; SOLDERING OR UNSOLDERING; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THESURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; TRANSPORTING; WELDING; WORKING BY LASER BEAM

The invention mainly relates to a pre-coated steel sheet wherein at least a region at the periphery (7) of at least one (6a;6b) of the opposite faces (6a,6b) of said pre-coated sheet (1,1') is coated with an additional coating (8) selected for increasing the vapor pressure between the pre-coating (2) and said additional coating (8) during a laser welding method up to a critical pressure at which the pre-coating (2) is ejected away from the weld (14). Preferably, the vaporization temperature of the additional coating (8) is greater than the vaporization temperature of the pre-coating (2) and the additional coating comprises gammagene elements like carbon and/or nickel. The invention also relates to a steel part obtained by laser welding, preferably butt laser welding, of at least a first and second pre-coated steel sheet (1,1') as above indicated. L'invention concerne principalement une tôle d'acier pré-revêtue dans laquelle au moins une région à la périphérie (7) d'au moins un (6a ; 6b) des faces opposées (6a, 6b) de ladite tôle pré-revêtue (1, 1') est revêtue d'un revêtement supplémentaire (8) choisi pour augmenter la pression de vapeur entre le pré-revêtement (2) et ledit revêtement supplémentaire (8) pendant un procédé de soudage au laser jusqu'à une pression critique à laquelle le pré-revêtement (2) est éjecté de la soudure (14). De préférence, la température de vaporisation du revêtement supplémentaire (8) est supérieure à la température de vaporisation du pré-revêtement (2) et le revêtement supplémentaire comprend des éléments gammagènes comme le carbone et/ou le nickel. L'invention concerne également une pièce en acier obtenue par soudage au laser, de préférence par soudage au laser bout à bout, d'au moins une première et une seconde tôle d'acier pré-revêtue comme indiqué ci-dessus.