Seamless steel pipe acceptance standard and quality inspection method

　　Inspection of steel pipe geometry and appearance: ① steel pipe wall thickness inspection: micrometer, ultrasonic thickness gauge, at least 8 points at both ends and record. ② inspection for outer diameter and ovality of steel pipe: caliper, vernier caliper and ring gauge, measure the maximum and minimum points. ③ steel pipe length inspection: steel tape, manual and automatic length measurement. ④ steel pipe bending inspection: straightedge, level ruler (1m), feeler gauge and fine line measure the bending degree per meter and the bending degree of the whole length. ⑤ steel pipe end bevel angle and blunt edge inspection: angle ruler and clamp plate. 3. Steel pipe surface quality inspection: 100% ① manual visual inspection: lighting conditions, standards, experience, identification, steel pipe rotation. ② nondestructive testing: A. ultrasonic testing ut: it is sensitive to the surface and internal crack defects of various materials. Standard: GB / T 5777-1996 level: C5 level B. eddy current testing et: (electromagnetic induction) is mainly sensitive to point (hole) defects. Standard: GB / T 7735-2004 grade: B grade C. magnetic particle MT and magnetic leakage testing: magnetic testing, applicable to the detection of surface and near surface defects of ferromagnetic materials. Standard: GB / T 12606-1999 level: C4 level D. electromagnetic ultrasonic testing: it does not need coupling medium, and can be applied to high temperature, high speed, rough and dry steel pipe surface testing. E. penetrant inspection: fluorescence, coloring and detection of steel pipe surface defects. 4. Steel management performance inspection: ① tensile test: measure the stress and deformation, determine the strength (YS, TS) and plasticity index (a, z) of the material longitudinally, and determine the small diameter, thin-walled large diameter and thick wall calibration distance of the transverse sample pipe section, arc type and circular sample (￠ 10, ￠ 12.5). Note: the elongation of specimen after fracture is related to specimen size GB / T 1760 ② impact test: CVN, notch C, V, J / cm2 standard specimen 10 × 10 × 55 (mm) non-standard specimen 5 × 10 × 55 (mm) ③ hardness test: Brinell hardness Hb, Rockwell hardness HRC, Vickers hardness HV, etc. ④ hydraulic test: test pressure, holding time, P = 2S δ / D 5. SAE1020 Mild Steel Seamless Structural Pipe process performance test: 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 crack is qualified ③ expanding and curling test: top center taper is 30 °, 40 °, 60 ° ④ bending test: it can replace flattening test (for large diameter pipe) 6. Metallographic analysis of SAE1020 Mild Steel Seamless Structural Pipe: ① high power inspection（ Micro analysis) non metallic inclusion 100x GB / T 10561 grain size: grade, differential structure: m, B, s, t, P, F, A-S decarburization layer: internal and external a-method rating: a-sulfide b-oxide c-silicate d-spherical oxidation DS type ② low power test (macro analysis): naked eye, magnifier less than 10x A. acid etching test, B. sulfur printing test (tube blank) The results showed that low culture tissue and defects, such as porosity, segregation, subcutaneous bubbles, flaking, white spots, inclusions, etc. C. tower hairline inspection method: inspect the number, length and distribution of hairlines. More relevant articles read: the "supply chain" of steel trade industry may just be a dream - Wuxi seamless steel pipe plant provides small-diameter seamless steel pipe manufacturers. Chemical composition analysis: chemical analysis, instrumental analysis (infrared C-S instrument, direct reading spectrometer, ZCP, etc.). ① infrared C-S instrument: analyze ferroalloy, steel-making raw materials, C and S elements in steel. 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 in block sample: gas content analysis