Seamless Steel Pipe Quality Inspection Methods

1. Chemical composition analysis: chemical analysis method, instrumental analysis method (infrared C-S instrument, direct reading spectrometer, zcP, etc.).

① Infrared C-S meter: Analyze ferroalloys, steelmaking raw materials, and C and S elements in steel.

②Direct reading spectrometer: C, Si, Mn, P, S, Cr, Mo, Ni, Cn, A1, W, V, Ti, B, Nb, As, Sn, Sb, Pb, Bi in bulk samples

③N-0 meter: gas content analysis N, O

2. Steel pipe geometric dimensions and appearance inspection:

① Steel pipe wall thickness inspection: micrometer, ultrasonic thickness gauge, no less than 8 points at both ends and recorded.

② Steel pipe outer diameter and ovality inspection: caliper, vernier caliper, ring gauge, measure the maximum point and minimum point.

③Steel pipe length inspection: steel tape measure, manual and automatic length measurement.

④ Steel pipe curvature inspection: Use a ruler, level (1m), feeler gauge, and thin wire to measure the curvature per meter and the curvature of the entire length.

⑤ Inspection of steel pipe end bevel angle and blunt edge: square ruler and clamping plate.

3． Steel pipe surface quality inspection: 100%

① Manual visual inspection: lighting conditions, standards, experience, markings, steel pipe rotation.

②Non-destructive testing inspection:

a. Ultrasonic flaw detection UT: It is sensitive to surface and internal crack defects of uniform materials of various materials. Standard: GB/T 5777-1996. Level: C5 level

b. Eddy current flaw detection ET: (electromagnetic induction) is mainly sensitive to point-shaped (hole-shaped) defects. Standard: GB/T 7735-2004. Level: B Level

c. Magnetic particle MT and magnetic flux leakage inspection: Magnetic inspection is suitable for detecting 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 required, and it can be applied to high-temperature, high-speed, rough steel pipe surface flaw detection.

e. Penetrant testing: fluorescence, coloring, detecting surface defects of steel pipes.

4. Steel management performance inspection:

① Tensile test: measure stress and deformation, and determine the strength (YS, TS) and plasticity index (A, Z) of the material. Longitudinal and transverse specimens, pipe sections, arc-shaped and circular specimens (￠10, ￠12.5). Small diameter thin wall steel pipe, large diameter thick wall steel pipe, fixed gauge length. Note: The elongation of the sample after breaking is related to the size of the sample GB/T 1760

②Impact test: CVN, notched C-type, V-type, work J value J/cm2. Standard sample 10×10×55 (mm) Non-standard sample 5×10×55 (mm).

③Hardness test: Brinell hardness HB, Rockwell hardness HRC, Vickers hardness HV, etc.

④Hydraulic test: test pressure, pressure stabilization time, p=2Sδ/D

5. Steel pipe process performance inspection process:

① Flattening test: round specimen C-shaped specimen (S/D>0.15) H= (1+2) S/(∝+S/D) L=40~100mm Unit length deformation coefficient=0.07~0.08

② Ring pull test: L=15mm, no cracks, it is qualified

③Expansion and curling test: top-center taper is 30°, 40°, 60°

④Bending test: can replace the flattening test (for large diameter pipes)

6. Metallurgical analysis of steel pipe:

①High-power inspection (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: inner and outer. Method A rating: Class A - sulfide, Class B - oxide, Class C - silicate, D - spherical oxidation, Class DS.

②Low magnification test (macroscopic analysis): naked eye, magnifying glass 10x or less.

a. Acid etching test method.

b. Sulfur print inspection method (tube blank inspection, showing low culture structure and defects, such as looseness, segregation, subcutaneous bubbles, skinning, white spots, inclusions, etc.

c. Tower-shaped hairline inspection method: Check the number, length, and distribution of hairlines.