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AssigneeNippon Steel Corporation
InventorsTadashi Ishikawa, Kiyotaka Nakashima, Tetsuro Nose
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A method of improvement of toughness of a heat affected zone in a multi-layer welded joint, a fillet welded joint, and a one-pass or several-pass large heat input welded joint of a steel plate is provided, that is, a method of improvement of toughness of a heat affected zone in a welded joint of a steel plate characterized subjecting a surface of a heat affected zone formed by a last pass of a multi-layer welded joint of a steel plate to impacts by an ultrasonic vibration tool or shot peening by ultrasonic vibration steel balls to thereby make an average of longitudinal axis of crystal grains up to a depth of 2 mm or more from the surface of the steel plate in the microstructure adjacent to a fusion line (FL) of a weld metal and a steel plate matrix in said heat affected zone formed by the last pass the equivalent of the crystal grain size of the steel plate matrix before the welding at a depth of ¼ of a thickness t from the surface of the steel plate.
A method of improvement of toughness of a heat affected zone in a welded joint of a steel plate, wherein said steel plate has a plate thickness t, characterized by subjecting a surface of a heat affected zone formed by a last pass of a multi-layer welded joint of a steel plate to impacts by an ultrasonic vibration tool using one or more pins having a diameter of 10 to 30 mm with an oscillating amplitude of between 20 to 60 μm to thereby make an average of longitudinal axis of crystal grains to a depth of at least 2 mm from the surface of the steel plate in the microstructure adjacent to a fusion line (FL) of a weld metal and a steel plate matrix in said heat affected zone formed by the last pass equivalent to the crystal grain size of the steel plate matrix before the welding at a depth of ¼ of the thickness t from the surface of the steel plate.
A method of improvement of toughness of a heat affected zone in a welded joint of a steel plate, wherein said steel plate has a plate thickness t, characterized by subjecting a vicinity of a toe portion of a fillet welded joint of a steel plate to impacts by an ultrasonic vibration tool using one or more pins having a diameter of 10 to 30 mm with an oscillating amplitude of between 20 to 60 μm to thereby make an average of longitudinal axis of crystal grains to a depth of at least 2 mm from the surface of the steel plate in the microstructure adjacent to a fusion line of a weld metal and a steel plate matrix in the heat affected zone in the vicinity of the toe portion equivalent to the crystal grain size of the steel plate matrix before the welding at a depth of ¼ of a thickness t from the surface of the steel plate.
Dependencies are inferred from the claim text.