Overview of Quality Inspection Methods for Steel Pipe:
1. Chemical composition analysis:
Chemical analysis, instrumental analysis (infrared C-S instrument, direct reading spectrometer, zcP, etc.).
① infrared C-S instrument: analysis of ferroalloy, steelmaking raw materials, steel in the C, S elements.
② Direct reading spectrometer: C, Si, Mn, P, S, Cr, Mo, Ni, Cn, A1, W, V, Ti, B, Nb, As, Sn, Sb, Pb, Bi
③ N-0 instrument: gas content analysis N, O
2. Steel pipe geometry and shape inspection:
① steel wall thickness inspection: micrometer, ultrasonic thickness gauge, both ends of not less than 8 points and recorded.
② steel pipe diameter, oval check: card regulations, vernier caliper, ring gauge, measured the largest point, the smallest point.
③ steel pipe length inspection: steel tape, manual, automatic length measurement.
④ steel pipe bending check: ruler, level (1m), feeler, thin line per meter curvature, full length of bending.
⑤ steel pipe end groove angle and blunt edge check: angle feet, card board.
3. Steel pipe surface quality inspection: 100%
① artificial eye inspection: lighting conditions, standards, experience, logo, steel tube rotation.
② non-destructive testing inspection:
a. Ultrasonic testing UT:
For a variety of materials on the surface of the material and internal cracks are more sensitive.
Standard: GB / T 5777-1996 Level: C5 level
b. eddy current testing ET: (electromagnetic induction)
Mainly sensitive to point-like (hole-shaped) defects. Standard: GB / T 7735-2004
Level: Level B
c. magnetic powder MT and magnetic flux leakage detection:
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 testing:
Do not need coupling medium, can be applied to high temperature and high speed, rough steel pipe surface inspection.
e. penetration testing:
Fluorescence, coloring, detection of steel pipe surface defects.
4. Steel pipe management performance test:
① tensile test: stress and deformation, determine the strength of the material (YS, TS) and plastic index (A, Z)
Longitudinal, transverse specimen pipe section, arc type, round specimen (¢ 10, ¢ 12.5)
Small diameter, thin-walled large diameter, thick-wall fixed pitch.
Note: The elongation at break after the specimen is related to the size of the specimen
② impact test: CVN, notch C type, V type, power 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 and so on
④ hydraulic test: test pressure, regulation time, p = 2Sδ / D
5. Steel pipe technology performance test:
① Flattening test: C-shaped sample (S / D> 0.15) H = (1 + 2) S / (α + S / D)
L = 40 ~ 100mm unit length deformation coefficient = 0.07 ~ 0.08
② ring test: L = 15mm without cracks for qualified
③ flaring and curling test: vertex taper of 30 °, 40 °, 60 °
④ bending test: can replace the flattening test (for large diameter pipe)
6. Metallographic analysis of steel pipe:
① high test (micro 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 - Spherical Oxidation DS Class
② low magnification test (macro analysis): the naked eye, magnifying glass 10x the following
b. Sulfur inspection (billet inspection, showing low tissue and defects, such as loose, segregation, subcutaneous bubbles, skin, white spots, inclusions and so on.
c. Tower hair pattern test method: test the amount of hair, length and distribution.