20# seamless steel pipe acceptance criteria and inspection methods

Pipe geometry and appearance tests: 
① check pipe wall thickness: micrometer, ultrasonic thickness gauge, the two ends of not less than 8:00 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 feet, card board.




3. Steel pipe surface quality inspection: 100% 
1 artificial visual inspection: lighting conditions, standards, experience, marking, steel pipe rotation. 
2 Non-destructive inspection: 
a. Ultrasonic inspection 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) is 
mainly sensitive to point (cavity) defects. Standard: GB/T 7735-2004 
grade: Class B 
c. Magnetic powder MT and magnetic flux leakage inspection: 
Magnetic flaw detection, suitable for the detection of surface and near surface defects of ferromagnetic materials. 
Standard: GB/T 12606-1999 Grade: C4 grade 
d. Electromagnetic ultrasonic flaw detection: 
no coupling medium is required, it can be applied to the surface inspection of high temperature and high speed and rough steel pipe. 
e. Penetration testing: 
Fluorescence, coloring, and inspection of surface defects of steel pipes.




4. 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 after fracture of the sample is related to the sample size. GB/T 1760 
2 Impact test: CVN, notched C type, V type, work J value J/cm2 
standard sample 10×10×55 (mm) non-standard test 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




5. Steel pipe process performance test: 
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 No crack is qualified 
3 flaring and crimping test: top taper is 30°, 40°, 60° 
4 Bending test: can replace flattening test (for large diameter pipe In terms of)




6. Metallographic analysis seamless steel pipe: 
① high power examination (micro analysis) http://www.tjdwfgz.com metallic inclusions 100x GB / T 10561 grain size: level differential 
Organization: M, B, S, T , P , F, AS 
decarburization layer: internal and external 
A method rating: class A - sulfide class B - oxide class C - silicate D - globular oxidation DS class 
2 low magnification test (macro analysis): naked eye, magnifying glass 10x The following 
a. Acid etching test, b. Sulphur printing test (tube blank test, showing low culture and defects, such as loose, segregation, subcutaneous bubbles, skinning, white spots, inclusions, etc.) 
c. Test method: check the number, length and distribution of hairline.