Introduction to the detection method of thermal expansion seamless steel pipe
Five kinds of common detection methods after the production of thermal expansion seamless steel tubes
First: inspection of steel pipe geometry and shape:
1 Steel pipe wall thickness inspection: micrometer, ultrasonic thickness gauge, no less than 8 points on both ends and recorded.
2 Steel pipe outer diameter, ovality inspection: caliper, vernier caliper, ring gauge, measuring the maximum point, the minimum point.
3 steel pipe length inspection: steel tape measure, manual, automatic length measurement.
4 steel pipe bending inspection: ruler, level (1m), feeler gauge, thin line measurement per meter bending, full-length bending.
5 steel pipe end groove angle and blunt edge inspection: square ruler, card board.
Second: steel pipe surface quality inspection: 100%
1 artificial visual inspection: lighting conditions, standards, experience, signs, steel tube rotation. 2 Non-destructive testing: a. Ultrasonic testing UT:
It is sensitive to the uniform surface of materials and internal crack defects. Standard: GB/T 5777-1996 Level: C5 level b. Eddy current testing ET: (electromagnetic induction)
Mainly sensitive to point (cavity) defects. Standard: GB/T 7735-2004 Level: Class B
c. Magnetic powder MT and magnetic flux leakage inspection:
Magnetic flaw detection for the detection of surface and near surface defects of ferromagnetic materials. Standard: GB/T 12606-1999 Level: C4 level d. Electromagnetic ultrasonic flaw detection:
No coupling medium is needed, it can be applied to the surface inspection of high temperature and high speed and rough steel pipes. e. Penetration testing:
Fluorescence, coloring, and inspection of surface defects of steel pipes.
Third: steel management performance test:
1 Tensile test: measure stress and deformation, determine material strength (YS, TS) and plasticity index (A, Z) longitudinal, transverse sample pipe section, arc type, round sample (¢10, ¢12.5) small diameter , thin wall large diameter, thick wall fixed gauge distance.
Note: The elongation of the sample after breaking is related to the sample size. GB/T 1760
2 Impact test: CVN, notch C type, V type, work J value J/cm2
Standard sample 10×10×55 (mm) non-standard sample 5×10×55 (mm)
3 hardness test: Brinell hardness HB, Rockwell hardness HRC, Vickers hardness HV, etc.
4 hydraulic test: test pressure, voltage regulation time, p = 2S δ / D
Fourth: inspection of steel pipe process performance:
1 flattening test: round sample C-shaped sample (S/D>0.15) H=(1+2)S/(∝+S/D) L=40～100mm Deformation coefficient per unit length=0.07～0.08
2 ring pull test: L = 15mm without crack is qualified
3 Flaring and crimping test: top cone taper is 30°, 40°, 60°
4 bending test: can replace the flattening test (for large diameter pipes)
Fifth, metallographic analysis of seamless steel tubes:
1 high-spectrum test (microscopic analysis) non-metallic inclusions 100x GB/T 10561 grain size: grade, grade difference Organization: M, B, S, T, P, F, A-S Decarburization layer: inside and outside
A method rating: Class A - Sulfide Class B - Oxide Class C - Silicate D-Spheroidal Oxidation DS class 2 Low power test (macroscopic analysis): naked eye, magnifying glass 10x or less
a. Acid etching test, b. Sulphur printing test (tube blank inspection, showing low culture tissue and defects, such as loose, segregation, subcutaneous air bubbles, skinning, white spots, inclusions, etc.).
