51 steel pipe network latest knowledge of pipe recommended: uneven wall thickness of steel pipe is mainly reflected in the uneven spiral wall thickness, uneven wall thickness and head and tail wall thickness thick, thin and so on. The influence of the continuous rolling process adjustment is an important factor that causes the wall thickness of the finished pipe to be uneven. Specifically:
1. The cause of uneven wall thickness in the spiral is:
1) The wall thickness of the piercing mill is not uniform, the inclination angle of the two rolls is not equal, or the amount of rolling before the head is too small, etc. The uneven wall thickness caused by the adjustment causes a spiral distribution along the entire length of the steel pipe.
2) The uneven wall thickness caused by the premature opening of the centering roll, misalignment of the centering roll, and jerking of the ejector pin during the rolling process are generally distributed helically along the entire length of the steel tube.
Measures:
1) Adjust the center line of the piercing mill so that the inclination angles of the two rolls are equal, and adjust the rolling mill according to the given parameters of the rolling table.
2) For the second case, adjust the centering roll opening time according to the capillary exit speed. Do not open the centering roll too early during the rolling process to prevent the top rod from shaking and causing uneven wall thickness. The opening degree of the centering roll needs to be adjusted appropriately according to the change of the diameter of the capillary tube, and the size of the capillary bounce is taken into consideration.
2. Causes of uneven linear wall thickness:
1) The height of the mandrel pre-worn saddle is not adjusted properly. When the mandrel is pre-worn, the mantle comes into contact with the capillary tube on one side of the mandrel. As a result, the temperature drop of the capillary on the contact surface is too fast, resulting in uneven wall thickness and even pulling and concave defects.
2) The gap between tandem rolls is too small or too large.
3) Roller centerline deviation.
4) Uniform and double-rack unbalanced rolling results in linear symmetric deviations in the ultra-thin (super-thick) and double-sheath direction of the single-pipe direction of the steel pipe.
5) The safety 臼 fracture, the difference between the inner and outer roll gaps will cause the linear asymmetrical deviation of the steel tube.
6) Improper adjustment of continuous rolling, steel rolling, pull steel rolling will cause linear wall thickness uneven.
Measures:
1) Adjust the height of the mandrel pre-worn saddle and ensure that the mandrel is aligned with the capillary tube.
2) When changing the hole type and rolling specification, the roll gap should be measured so that the actual roll gap is consistent with the rolling table.
3) The optical centering device is used to adjust the rolling center line, and the center line of the pipe rolling mill must be corrected during the annual overhaul.
4) Replace the safety and breakage racks in time and carry out the measurement of the roll gaps inside and outside the roll. Problems will occur and they will be replaced in time.
5) During continuous rolling, steel and steel stacking should be avoided.
3, head and tail wall thickness uneven causes:
1) The slope of the front end of the tube blank is too large, and the centering hole of the tube blank is not easy to cause uneven wall thickness of the steel tube head.
2) When the perforation, the extension coefficient is too large, the rotational speed of the roller is too high, and the rolling is unstable.
3) The instability of the thrower's throwing steel can easily cause uneven wall thickness at the end of the capillary tube.
Measure 1) Check the quality of the tube blank to prevent the taper of the front end of the tube from being cut off, and the amount of reduction is large. The centering hole should be corrected when changing the hole shape or overhauling.
2) Use a lower perforation speed to ensure the stability of the rolling and the uniformity of the capillary wall thickness. When the roller speed is adjusted, the matching guide plate is adjusted accordingly.
3) Concerned about the status of the use of the guide plate and increase the inspection of the guide plate bolts to reduce the turbulence of the guide plate during rolling and ensure the stability of the thrower.
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1. The cause of uneven wall thickness in the spiral is:
1) The wall thickness of the piercing mill is not uniform, the inclination angle of the two rolls is not equal, or the amount of rolling before the head is too small, etc. The uneven wall thickness caused by the adjustment causes a spiral distribution along the entire length of the steel pipe.
2) The uneven wall thickness caused by the premature opening of the centering roll, misalignment of the centering roll, and jerking of the ejector pin during the rolling process are generally distributed helically along the entire length of the steel tube.
Measures:
1) Adjust the center line of the piercing mill so that the inclination angles of the two rolls are equal, and adjust the rolling mill according to the given parameters of the rolling table.
2) For the second case, adjust the centering roll opening time according to the capillary exit speed. Do not open the centering roll too early during the rolling process to prevent the top rod from shaking and causing uneven wall thickness. The opening degree of the centering roll needs to be adjusted appropriately according to the change of the diameter of the capillary tube, and the size of the capillary bounce is taken into consideration.
2. Causes of uneven linear wall thickness:
1) The height of the mandrel pre-worn saddle is not adjusted properly. When the mandrel is pre-worn, the mantle comes into contact with the capillary tube on one side of the mandrel. As a result, the temperature drop of the capillary on the contact surface is too fast, resulting in uneven wall thickness and even pulling and concave defects.
2) The gap between tandem rolls is too small or too large.
3) Roller centerline deviation.
4) Uniform and double-rack unbalanced rolling results in linear symmetric deviations in the ultra-thin (super-thick) and double-sheath direction of the single-pipe direction of the steel pipe.
5) The safety 臼 fracture, the difference between the inner and outer roll gaps will cause the linear asymmetrical deviation of the steel tube.
6) Improper adjustment of continuous rolling, steel rolling, pull steel rolling will cause linear wall thickness uneven.
Measures:
1) Adjust the height of the mandrel pre-worn saddle and ensure that the mandrel is aligned with the capillary tube.
2) When changing the hole type and rolling specification, the roll gap should be measured so that the actual roll gap is consistent with the rolling table.
3) The optical centering device is used to adjust the rolling center line, and the center line of the pipe rolling mill must be corrected during the annual overhaul.
4) Replace the safety and breakage racks in time and carry out the measurement of the roll gaps inside and outside the roll. Problems will occur and they will be replaced in time.
5) During continuous rolling, steel and steel stacking should be avoided.
3, head and tail wall thickness uneven causes:
1) The slope of the front end of the tube blank is too large, and the centering hole of the tube blank is not easy to cause uneven wall thickness of the steel tube head.
2) When the perforation, the extension coefficient is too large, the rotational speed of the roller is too high, and the rolling is unstable.
3) The instability of the thrower's throwing steel can easily cause uneven wall thickness at the end of the capillary tube.
Measure 1) Check the quality of the tube blank to prevent the taper of the front end of the tube from being cut off, and the amount of reduction is large. The centering hole should be corrected when changing the hole shape or overhauling.
2) Use a lower perforation speed to ensure the stability of the rolling and the uniformity of the capillary wall thickness. When the roller speed is adjusted, the matching guide plate is adjusted accordingly.
3) Concerned about the status of the use of the guide plate and increase the inspection of the guide plate bolts to reduce the turbulence of the guide plate during rolling and ensure the stability of the thrower.
Learn more about pipe knowledge: http://?id=3
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