What are the common inner surface defects of seamless steel pipes? How to detect?
Common defects: internal cracks, internal folds (folds), pits, scratches, etc.
Detection methods:
Ultrasonic testing (UT): can detect internal cracks and inclusions.
Eddy current testing (ET): suitable for surface and near-surface defect detection.
Endoscopic inspection: directly observe the inner wall of the steel pipe, suitable for large-diameter pipes.
Why does the wall thickness of seamless steel pipes appear uneven? How to control it?
Reason:
Uneven heating of the billet or improper perforation process.
Roller adjustment deviation during rolling.
Control method:
Optimize the perforation process (such as adjusting the position of the head and the spacing between the rollers).
Online thickness gauge monitors and feedbacks adjustments in real time.
Cold rolling/cold drawing process improves dimensional accuracy.
How to prevent outer surface defects of seamless steel pipes (such as cracks and warping)?
Main preventive measures:
Strictly control the heating temperature to avoid overburning or uneven temperature.
Regularly maintain the rollers to prevent scratches caused by surface wear.
Pickling/polishing to remove scale and burrs
Detection methods: visual inspection, magnetic particle testing (MT) or penetration testing (PT).
What may be the reason why the mechanical properties of seamless steel pipes do not meet the standards? How to improve?
Possible reasons:
Unqualified material composition (such as deviation in carbon and alloy element content).
Improper heat treatment process (wrong quenching/tempering temperature or time).
Improvement methods:
Strict chemical composition analysis (spectrometer detection).
Optimize heat treatment process (such as temperature control accuracy, cooling rate).
Mechanical property tests (tensile and impact tests) to ensure compliance with standards.
How to ensure the corrosion resistance of seamless steel pipes?
Key measures:
Select corrosion-resistant materials (such as stainless steel, alloy steel).
Surface treatment (galvanizing, plastic spraying, passivation treatment).
Regular quality inspection (salt spray test, intergranular corrosion test).
Application scenario adaptation: For example, 316L stainless steel is used in marine environment, and duplex steel is used in acidic medium.
