Abstract: A butt joint deep penetration laser welding method is used for joining facing end sections of flat steel products, each having a carbon content CS<0.02%. In order to improve such a method such that an improved weld quality in terms of geometry and strength is achievable with it, at least one carbon-containing carrier material is inserted into a butt joint gap between the end sections, the carbon content of which is CT?20·CS, preferably CT?100·CS, and/or carbon is inserted into the butt joint gap or applied to at least one end section, such that the volume of the carbon inserted into the butt joint gap corresponds to 1% to 20% of the volume of a melt produced by a butt joint deep penetration laser welding process.

Abstract: A butt joint deep penetration laser welding method is used for joining facing end sections of flat steel products, each having a carbon content CS<0.02%. In order to improve such a method such that an improved weld quality in terms of geometry and strength is achievable with it, at least one carbon-containing carrier material is inserted into a butt joint gap between the end sections, the carbon content of which is CT?20·CS, preferably CT?100·CS, and/or carbon is inserted into the butt joint gap or applied to at least one end section, such that the volume of the carbon inserted into the butt joint gap corresponds to 1% to 20% of the volume of a melt produced by a butt joint deep penetration laser welding process.