The control of the wall thickness of steel pipes is a difficult point in the production of steel pipes. The measures to improve the wall thickness accuracy in production mainly include the following aspects:
1. Tube billet heating: The heating should be uniform, and the rapid rise and fall temperature is prohibited. Each temperature should be kept steady and slow, and the maximum lifting temperature should not exceed 30 °C.
2. Centering roller: Determine whether the centering roller installation is in place, adjust the center of the relevant core roller, the opening angle and the opening size of each action. The center of the core roller should be on the rolling line.
3. Rolling center line: Make sure that the center line of the punching machine is consistent with the center line of the perforated car, avoiding “up rolling” or “down rolling”, so that the tube blank maintains uniform force during perforation.
4. Rolling tools: for the wear of the head, guides, rolls and other rolling tools should be replaced in time.
5. Rolling tool installation: The center of the roll distance and lead distance must be on the rolling line. Ensure that the center line of the lead distance and the roll distance is on the center line of the piercing and rolling, that is, the upper and lower roll distances are equal, and the left and right lead distances are equal.
6. Perforated ejector: The perforated ejector generally selects thick-walled tubes with an outer diameter of 108mm-114mm, a wall thickness requirement of 25mm and a uniform wall thickness.
7. Rolling mill core rod: The core rod should be processed with thick wall tube with thick wall thickness. For the core rod with smaller specification, solid blank can be used instead. Thick-walled tubes and solid billets with uniform wall thickness can greatly reduce the probability of bending and deformation of the mandrel bar, and can effectively improve the wall thickness accuracy of the steel pipe.
8. The precision of the mandrel: the length of the mandrel is relatively large, generally using the outer diameter of the first car and then breaking the mouth welding, or using long material direct turning. The external machining accuracy of the mandrel is controlled to ±0.1 mm, and the straightness deviation of the mandrel is not more than 5 mm. When welding, a finished pin is inserted between the two core rods for positioning to prevent excessive deviation of the total straightness caused by welding.
9. Improve the process: Improve the process, prevent the intermediate thinning and wall thickness from increasing beyond the control range, and improve the wall thickness accuracy.
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