Square and rectangular tubes (such as a500 square tube or a500 rectangular tube) is a name for square tubes, that is, steel tubes with equal side lengths. It is made of strip steel after process treatment. Generally, the strip steel is unpacked, flattened, crimped, welded to form a round tube, and then rolled into a square tube by a round tube (such as a welded steel tube) and then cut to the required length.

Wall thickness control is a key point in the production of square and rectangular tubes. Today we will introduce nine measures to improve wall thickness accuracy:

(1) Centering roller

Determine whether the centering roller is installed in place, adjust the center of the core-holding roller, the opening angle and the opening size of each action to be consistent, and the center of the core-holding roller should be on the rolling line.

(2) Rolling tools

The worn out plugs, guide plates, rolls and other square tube rolling tools should be replaced in time.

(3) Perforated ejector pin

The perforated ejector generally chooses a thick-walled square tube with an outer diameter of Φ108mm-Φ114mm, a wall thickness of ≥25mm and uniform wall thickness.

(4) Mandrel precision

The slenderness of the mandrel is relatively large. Generally, the outer diameter is turned first and then the hole is welded, or the long material is directly turned into shape. The external processing accuracy of the mandrel is controlled at ±0.1mm, and the straightness deviation of the mandrel does not exceed 5mm. When welding, insert a finely machined pin between the two core rods for positioning to prevent excessive deviation of the total straightness caused by welding.

(5) Tube heating

The square rectangular tube should be heated evenly, and the temperature should not be raised or lowered rapidly. Each temperature rise and fall should be kept steady and slow, and the maximum temperature rise and fall should not exceed 30°C.

(6) Improve the process

Prevent the middle thinning and wall thickness increase from exceeding the control range, and improve the wall thickness accuracy.

(7) Rolling center line

Make sure that the rolling centerline of the piercing machine is consistent with the centerline of the piercing trolley, and avoid upper or lower rolling, so that the square and rectangular tube blanks can be evenly stressed during piercing.

(8) Tool installation

The center of roll distance and guide distance must be on the rolling line. Ensure that the center line of the guide distance and roll distance is on the center line of piercing and rolling, that is, the upper and lower roll distances are equal, and the left and right guide distances are equal.

(9) Rolling Mandrel

Mandrels should be processed with thick-walled square tubes with thicker walls. For mandrels with smaller specifications, solid blanks can be used instead. Thick-walled pipes and solid billets with uniform wall thickness can greatly reduce the probability of mandrel bending deformation, and can effectively improve the wall thickness accuracy of steel pipes.