Rectangular hollow steel profile stretch bending forming method and special clamping device thereof

The invention relates to a rectangular hollow steel profile stretch bending forming method and a special clamping device thereof. The rectangular hollow steel profile stretch bending forming method comprises the following steps of 1, putting elastic core iron in a rectangular hollow steel profile blank, plugging one end, filling with sand, and compacting the sand by a mechanical vibration device; 2, plugging the other end of the rectangular hollow steel profile blank; 3, putting the rectangular hollow steel profile blank into a stretch bending machine; 4, pressing the rectangular hollow steel profile blank by the clamping device; 5, applying pre-stretch tensions at the two ends of the rectangular hollow steel profile blank; 6, bending the rectangular hollow steel profile blank along a stretch bending copying die; 7, supplementing the tension to enable the rectangular hollow steel profile blank to form tightly along the bending copying die; 8, unloading the tension, and taking off a forming piece from the stretch bending machine. The special clamping device comprises a screw rod, a support frame and a cover plate, wherein the screw rod is detachably and fixedly connected with the support frame, and the screw rod is detachably and fixedly connected with the cover plate through a circular groove. The method and the device can effectively prevent products from generating warpage, depression, wrinkles and rebounding.