The methods for improving the wall thickness accuracy of seamless pipes mainly include the following
1. Seamless steel pipe billet heating
The heating should be uniform, and the rapid temperature rise and fall is prohibited. Each temperature rise and fall should be kept steady and slow, and the maximum temperature rise and fall should not exceed 30°C.
2. Centering roller
Determine whether the installation of the centering roller is in place, adjust the center of the core-holding roller, the opening angle and the size of the opening of each action to be consistent, and the center of the core-holding roller should be on the rolling line.
3. Rolling center line
Make sure that the rolling center line of the piercing machine is consistent with the center line of the piercing trolley, avoid "upper rolling" or "lower rolling", so that the tube blank can maintain uniform force during piercing.
4. Rolling tools
Rolling tools such as worn plugs, guide plates, and rolls should be replaced in time.
5. Rolling tool installation
The center of roll distance and guide distance must be on the rolling line. Make sure that the center line of the guide distance and the roll distance is on the piercing and rolling center line, that is, the upper and lower roller distances are equal, and the left and right guide distances are equal.
6. Perforated ejector pin
The perforated ejector generally chooses a thick-walled pipe with an outer diameter of Φ108mm-Φ114mm, a wall thickness of ≥25mm and uniform wall thickness.
7. Rolling mandrel
The mandrel should be processed with a thick-walled tube with a thicker wall thickness. For the mandrel with a smaller size, a solid blank can be used instead. Thick-walled pipes and solid billets with uniform wall thickness can greatly reduce the probability of mandrel bending and deformation, and can effectively improve the wall thickness accuracy of steel pipes.
8. The precision of mandrel
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, a precision-machined pin is inserted between the two core rods for positioning, so as to prevent excessive deviation of the total straightness caused by welding.
9. Improve the process
Improve the process, prevent the occurrence of intermediate thinning and wall thickness increase beyond the control range, and improve the wall thickness accuracy.
1. Seamless steel pipe billet heating
The heating should be uniform, and the rapid temperature rise and fall is prohibited. Each temperature rise and fall should be kept steady and slow, and the maximum temperature rise and fall should not exceed 30°C.
2. Centering roller
Determine whether the installation of the centering roller is in place, adjust the center of the core-holding roller, the opening angle and the size of the opening of each action to be consistent, and the center of the core-holding roller should be on the rolling line.
3. Rolling center line
Make sure that the rolling center line of the piercing machine is consistent with the center line of the piercing trolley, avoid "upper rolling" or "lower rolling", so that the tube blank can maintain uniform force during piercing.
4. Rolling tools
Rolling tools such as worn plugs, guide plates, and rolls should be replaced in time.
5. Rolling tool installation
The center of roll distance and guide distance must be on the rolling line. Make sure that the center line of the guide distance and the roll distance is on the piercing and rolling center line, that is, the upper and lower roller distances are equal, and the left and right guide distances are equal.
6. Perforated ejector pin
The perforated ejector generally chooses a thick-walled pipe with an outer diameter of Φ108mm-Φ114mm, a wall thickness of ≥25mm and uniform wall thickness.
7. Rolling mandrel
The mandrel should be processed with a thick-walled tube with a thicker wall thickness. For the mandrel with a smaller size, a solid blank can be used instead. Thick-walled pipes and solid billets with uniform wall thickness can greatly reduce the probability of mandrel bending and deformation, and can effectively improve the wall thickness accuracy of steel pipes.
8. The precision of mandrel
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, a precision-machined pin is inserted between the two core rods for positioning, so as to prevent excessive deviation of the total straightness caused by welding.
9. Improve the process
Improve the process, prevent the occurrence of intermediate thinning and wall thickness increase beyond the control range, and improve the wall thickness accuracy.
