Wall thickness control is a key point in the production of square 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 relevant core roller, the opening angle and the opening size of each action to be consistent, and the center of the core roller should be on the rolling line.

2. Rolling tools

Worn square tube rolling tools such as top heads, guide plates, and rollers, should be replaced in time.

3. Perforated ejector rod

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

4. Mandrel precision

The mandrel is relatively long and thin and generally uses the outer diameter to be turned first, and then the opening is broken for welding or long materials are 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. During welding, a precision-machined pin is inserted between the two mandrels for positioning to prevent excessive deviation in total straightness caused by welding.

5. Heating of tube billets

The heating of square tubes should be uniform, and rapid temperature rise and fall is prohibited. Each temperature rise and fall should be stable and slow, and the maximum temperature rise and fall should not exceed 30°C.

6. Perfecting the process

Preventing the occurrence of intermediate thinning and wall thickness increase beyond the control range, and improving the wall thickness accuracy.

7. Rolling center line

Ensure that the rolling center line of the piercing machine is consistent with the center line of the piercing trolley, avoid rolling up or down, and keep the square tube billet under uniform force during piercing.

8. Tool installation

The center of the roller pitch and the guide pitch must be on the rolling line. Ensure that the center line of the guide pitch and the roller pitch is on the piercing rolling center line, that is, the upper and lower roller pitches are equal, and the left and right guide pitches are equal.

9. Mandrel of the rolling mill

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