Due to improper loading, unloading, handling, or storage, square rectangular tubes often appear bent, elliptical, or partially bruised. It must be processed during installation to make it meet the standard of use. The square rectangular tube should carefully check the deformed part and analyze the cause of the deformation before processing. There are usually two methods of inspection, namely visual inspection and rolling method. Visual inspection is suitable for inspecting shorter square tubes. When checking, lift one end of the square tube and look from one end to the other with one eye. If multiple points on the surface of the tube are in a straight line, it is a straight tube, otherwise, it is a curved tube.

The rolling method is suitable for inspecting long rectangular pipes. When inspecting, place the square pipe flat on two parallel steel pipes or square wood, and roll it gently. When the pipe rolls at a uniform speed without swinging, it is a straight pipe; If the rolling speed is uneven and swings back and forth, the downside when it stops is convex, and it is marked for straightening. Generally speaking, when the side length of the square rectangular tube is greater than 100mm, the possibility of bending the tube is small, and it is not easy to straighten. If there is a curved part, it can be removed and used in other places that need to bend the pipe. Pipes whose nominal size is less than 100mm in side length can be straightened. There are two straightening methods: hot adjustment and cold adjustment.

The cold adjustment method is generally used for square and rectangular pipes whose nominal side length is less than 50mm and whose bending degree is not large. According to different specific operation methods, it is divided into lever straightening method, hammer straightening method, and special straightening method table straightening method. In the lever straightening method, the bending part of the pipe is used as the fulcrum, and the force is applied to the force point by hand. When straightening, the fulcrum position must be constantly changed, so that the curved pipe can be straightened evenly without deformation. Hammer straightening method: This method is used for long pipes with small side lengths. When the bending of the square pipe is determined, place the pipe on two parallel square kinds of wood at a certain distance. One person stands at one end of the pipe to observe the bending part of the pipe, and the other person taps it with a hammer according to the instructions of the observer. After several repetitions Knock, and the pipe can be straightened.

Special Straightening Bench Straightening Method When the side length of the square tube is large but not more than 100mm, straighten it on the straightening platform, place the bent part of the square tube between the two straightening blocks, and the convex part upwards. The distance between the support blocks can be adjusted according to the length of the bending part of the square tube, and then the screw is rotated to press down the pressing block and gradually press down the protruding part. After repeated rotation and adjustment, the square tube can be straightened.

The straightening method of the large curved clip straightener: it is to use the large curved clip straightener to move freely on the spot to straighten the bend of the rectangular pipe. The quality of the pipes straightened by the big bend card straightener is better, and other suitable straighteners can be made according to local conditions at the construction site. Square tube straightening can also be applied to hydraulic presses, manual presses, or jacks. The straightening of large-diameter pipe sections requires the use of pneumatic or hydraulic presses. The 30-ton vertical hydraulic press can straighten steel pipes with a diameter of 108mm and a wall thickness of 6mm. To straighten steel pipes with a diameter of 219mm and a wall thickness of 8mm, a 100-ton hydraulic press can be used to make pressed elbows. For larger diameter pipes, a 200-ton vertical hydraulic press is required.