Abstract: Plates of a heat exchanger plate pack are formed by a stack of plates defining at least two independent fluid flow circuits, each circuit comprising a central heater part and a border with a smooth surface. A cutout is produced on corners of each plate and on the border to be connected, of each plate to the adjacent plate, a fold is made in order to form a first flange. On this first flange a fold is made in order to form a second flange laying parallel to the central part of the corresponding plate and directed outward from the plate. The plates are superposed and held by applying the second flange of each plate to the second flange of the adjacent plate. A continuous sealed weld bead is made by completely melting the second superposed flanges of adjacent plates.

Abstract: The invention concerns a method for assembling plates (1) of a plate pack for a heat exchanger formed by a stack of plates. The invention is characterised in that it consists in producing on the edge of each plate (1) to be connected with the adjacent plate (1) a welt to form a first flange (7; 9); in producing on said first flange a welt to form a second flange (11; 13) of the adjacent plate; and in producing a continuous and sealed weld seam by melting the stacked second flanges (11; 13) of the adjacent plates (1).