Variable Section

an elongated metal product whose cross section varies continuously or in steps along its length. Sections with continuously variable cross sections are produced mainly by continuously varying the distance between the rolls while rolling. Sections with stepwise variable cross sections are produced mainly by pressing, or extrusion, through a die. In order to obtain sections with variable external dimensions, the dies are changed during the pressing process. Hollow sections with variable internal dimensions are produced by changing the position of a stepped pin (mandrel) within the die. A variable section can also be obtained by stamping separate portions of an elongated profile of constant cross section. Variable sections are used for the production of cantilever structures and of welded or riveted structures when thicker material is required to achieve joints of equal strength.