Fixture for welding long workpieces

A welding fixture for holding a plurality of long component members that are welded along their lengths into an elongate product, having at least three stationary clamps disposed in spaced-apart relation with each other along the long component members, and at least three movable clamps disposed opposite to the stationary clamps, respectively, and cooperating the stationary clamps to clamp the component members in opposite clamping directions toward each other substantially perpendicular to the longitudinal direction of the component members. The fixture includes a pivot base disposed pivotally in a plane parallel to the clamping directions, and supporting at least one of the stationary clamps. The pivot base is supported by a supporting device pivotally about a pivot axis which is located on the component members clamped by the movable and stationary clamps. The base is pivoted by an actuator prior to welding of the component members along their lengths, in order to bend the component members so as to compensate for a warpage resulting from welding strains.