The control of the wall thickness of the steel pipe is a difficult point in the production of the steel pipe. The measures to improve the accuracy of the wall thickness of the seamless tube in the production mainly include the following aspects:
1. Tube billet heating
The heating should be uniform, and it is forbidden to rapidly increase or decrease the temperature. Each time the temperature rise and fall should be kept steady and slow, and the maximum rise and fall temperature should not exceed 30℃.
2. Centering roller
Determine whether the centering roll is installed in place, adjust the center, opening angle and opening size of each action of the relevant core roll to be consistent, and the center of the core roll should be on the rolling line.
3. Rolling center line
Ensure that the rolling center line of the piercing machine is consistent with the center line of the piercing trolley, and avoid “up rolling” or “down rolling”, so that the tube blank can be uniformly stressed during piercing.
4. Rolling tools
For the worn plugs, guide plates, rolls and other rolling tools, they should be replaced in time.
5. Installation of rolling tools
The center of 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 rod is generally selected as a thick-walled pipe with an outer diameter of Φ108mm-Φ114mm, a wall thickness of ≥25mm and a uniform wall thickness.
7. Rolling mandrel
The mandrel should be processed by a thick-walled tube with a thicker wall. For a mandrel with a smaller size, a solid billet can be used instead. Thick-walled pipes and solid billets with uniform wall thickness can greatly reduce the probability of bending deformation of the mandrel, and can effectively improve the wall thickness accuracy of the steel pipe.
8. The accuracy of the mandrel
The length and slenderness of the mandrel is relatively large. Generally, the outer diameter is first turned and then the opening is welded, or the long material is directly turned and formed. The external machining accuracy of the mandrel is controlled within ±0.1mm, and the straightness deviation of the mandrel does not exceed 5mm. When welding, a precision-machined pin is inserted between the two mandrels for positioning to prevent excessive deviation of the overall straightness caused by welding.
9. Improve the craftsmanship
Improve the process to prevent the thinning in the middle and the increase of the wall thickness from exceeding the control range, and improve the accuracy of the wall thickness.