The quality inspection methods of Seamless 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.
Direct Reading Spectrometer: C, Si, Mn, P, S, Cr, Mo, Ni, Cn, Al, W, V, Ti, B, Nb, As, Sn, Sb, Pb,
③ N-0 instrument: gas content analysis N, O.
2. Pipe geometry and shape inspection:
① pipe wall thickness check: micrometer, ultrasonic thickness gauge, both ends of not less than 8 points and record.
② pipe diameter, ovality check: calipers, vernier caliper, ring gauge, measured the largest point, the smallest point.
③ steel length check: steel tape, artificial, automatic measuring length.
④ steel bending test: ruler, level (1m), feeler, thin wire measured per meter bending, full-length curvature.
⑤ pipe end bevel angle and blunt edge inspection: square, card board.
3. Tube surface quality inspection: 100%
① artificial visual inspection: lighting conditions, standards, experience, logo, pipe rotation.
② NDT examination:
a. Ultrasonic testing UT:
For a variety of materials uniform surface cracks and internal defects more sensitive.
Standard: GB / T 5777-1996 level: C5 level
b eddy current testing ET: (electromagnetic induction)
Mainly punctate (hole-shaped) defects sensitive. Standard: GB / T 7735-2004
Level: B level
c. Magnetic Particle MT and MFL:
Magnetic inspection, suitable for the detection of surface and near-surface defects in ferromagnetic materials.
Standard: GB / T 12606-1999 level: C4 level
d. Electromagnetic ultrasonic flaw detection:
No coupling medium, can be used in high temperature, rough surface inspection of steel.
e. penetration testing:
Fluorescence, coloring, testing of steel surface defects.
4. Steel management performance test:
① Tensile test: measure the stress and deformation, determine the material strength (YS, TS) and plasticity index (A, Z)
Longitudinal and transverse sample pipe sections, arc type, round sample (¢ 10, ¢ 12.5)
Small diameter, thin-walled large diameter, thick-walled calibration distance.
Remark: Elongation of specimen after breakage depends on specimen size
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 and so on
④ hydraulic test: test pressure, voltage regulator time, p = 2Sδ / D
5. Steel process performance testing process:
① Flattening test: Round sample C shape 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 pull test: L = 15mm no crack as qualified
③ flaring and curling test: top center taper of 30 °, 40 °, 60 °
④ bending test: can replace the flattening test (for large-diameter tube)
6. Steel metallographic analysis:
① high magnification test (microscopic analysis): non-metallic inclusions 100x GB / T 10561 grain size: level, differential
Organization: M, B, S, T, P, F, A-S
Decarburization: inside and outside.
Method A Rating: Category A - Sulfide Category B - Oxides Category C - Silicates D-Spherical Oxidized DS Category.
② low magnification test (macro analysis): the naked eye, magnifying glass 10x the following.
a. Acid etching test.
b. Sulfur-based test (tube test, showing low tissue culture and defects, such as loose, segregation, subcutaneous bubbles, flap, white spots, inclusions and so on.
c tower pyramid test method: test hairline number, length and distribution.