The size defects of seamless pipes include uneven wall thickness, excessive wall thickness, excessive outer diameter, bending
Uneven wall thickness of seamless pipe
1. Features: The wall thickness of the seamless pipe is uneven on the same section, and the maximum wall thickness and the minimum wall thickness differ greatly.
2. Causes:
1) The tube blank is heated unevenly.
2) The rolling line of the piercer is not adjusted, and the centering mixer is unstable.
3) The plug is worn or the back hole of the plug is eccentric.
4) Correction of the centering hole of the tube blank.
5) The bending degree and cutting slope of the tube blank are too large.
3. Inspection: Measure one by one, and the end with uneven wall thickness should be removed.
The wall thickness of the seamless pipe is out of tolerance
1. Features: The wall thickness of the seamless pipe is one-way out of tolerance, and those with super positive deviation are called super thick wall thickness; those with super negative deviation are called ultra thin wall thickness.
2. Causes:
1) The tube blank is heated unevenly.
2) Improper adjustment of the punching machine.
Inspection and Judgment: Measure one by one, the end of tolerance should be cut off, the whole length of tolerance should be changed or rejected.
The outer diameter of the seamless pipe is out of tolerance
1. Features: The outer diameter of the seamless pipe exceeds the standard. Those who exceed the positive difference are called large outer diameters, and those who exceed the negative difference are called small outer diameters.
2. Causes:
1) The wear of the pass of the sizing machine is too large, or the design of the new pass is unreasonable.
2) The final rolling temperature is unstable.
3. Judgment: measure one by one, if it exceeds the standard, the judgment should be changed or rejected.
seamless pipe bending
1. Features: The seamless pipe is not straight along the length direction or the bend in the shape of a goose head at the end of the steel pipe is called "goose head bend".
2. Causes:
1) It is caused by local water cooling during manual thermal inspection.
2) Improper adjustment during straightening, light straightening and serious wear.
3) Improper processing, assembly and adjustment of the sizing machine.
4) Bending during hoisting and transportation.
3. Judgment: When the curvature exceeds the standard, it can be straightened again, otherwise it will be judged invalid. The "goose-bend" that cannot be straightened should be excised.
Uneven wall thickness of seamless pipe
1. Features: The wall thickness of the seamless pipe is uneven on the same section, and the maximum wall thickness and the minimum wall thickness differ greatly.
2. Causes:
1) The tube blank is heated unevenly.
2) The rolling line of the piercer is not adjusted, and the centering mixer is unstable.
3) The plug is worn or the back hole of the plug is eccentric.
4) Correction of the centering hole of the tube blank.
5) The bending degree and cutting slope of the tube blank are too large.
3. Inspection: Measure one by one, and the end with uneven wall thickness should be removed.
The wall thickness of the seamless pipe is out of tolerance
1. Features: The wall thickness of the seamless pipe is one-way out of tolerance, and those with super positive deviation are called super thick wall thickness; those with super negative deviation are called ultra thin wall thickness.
2. Causes:
1) The tube blank is heated unevenly.
2) Improper adjustment of the punching machine.
Inspection and Judgment: Measure one by one, the end of tolerance should be cut off, the whole length of tolerance should be changed or rejected.
The outer diameter of the seamless pipe is out of tolerance
1. Features: The outer diameter of the seamless pipe exceeds the standard. Those who exceed the positive difference are called large outer diameters, and those who exceed the negative difference are called small outer diameters.
2. Causes:
1) The wear of the pass of the sizing machine is too large, or the design of the new pass is unreasonable.
2) The final rolling temperature is unstable.
3. Judgment: measure one by one, if it exceeds the standard, the judgment should be changed or rejected.
seamless pipe bending
1. Features: The seamless pipe is not straight along the length direction or the bend in the shape of a goose head at the end of the steel pipe is called "goose head bend".
2. Causes:
1) It is caused by local water cooling during manual thermal inspection.
2) Improper adjustment during straightening, light straightening and serious wear.
3) Improper processing, assembly and adjustment of the sizing machine.
4) Bending during hoisting and transportation.
3. Judgment: When the curvature exceeds the standard, it can be straightened again, otherwise it will be judged invalid. The "goose-bend" that cannot be straightened should be excised.
