Steel pipe appearance quality inspection

A steel pipe is a steel material with a hollow section whose length is much greater than its diameter or circumference. According to the cross-sectional shape, it is divided into round, square, rectangular and special-shaped steel pipes. According to the material, it is divided into carbon structural steel pipes, low alloy structural steel pipes, alloy steel pipes and composite steel pipes. According to the purpose, it is divided into steel pipes for pipelines, engineering structures, thermal equipment, petrochemical industry (octg pipe), machinery manufacturing, geological drilling, and high-pressure equipment. According to the production process, it is divided into seamless pipe and welded steel pipe.

When inspecting the appearance quality of steel pipes before storage, the following items must be paid attention to

1) When observing the surface of hot-rolled steel with naked eyes, there must be no cracks, folds, scars, delamination and inclusions. Indentations and local protrusions, depressions, and pockmarks are allowed, but their height or depth shall not be greater than the relevant technical standards. Local defects are allowed to be removed, but lateral removal is not allowed, and the removal depth shall not exceed the allowable negative deviation value of steel of this size calculated from the actual size

2) When observing the surface of cold-drawn steel with naked eyes, the surface should be clean, smooth, bright or matte, without cracks, scars, inclusions, hairlines, folds and scales. Individual small scratches, cracks, dark spots, concave surfaces, pitting, etc., whose depth is not greater than the nominal size deviation calculated from the actual size, are allowed

3) The appearance of section steel should be smooth and tidy, and its roundness, side width, height, thickness, length, twist, slope, curvature, wave curvature and unevenness must not exceed the deviation specified in the relevant standards

4) The section steel should be straightened, the steel plate should be leveled, and the edges must be cut at right angles. In addition to meeting the above requirements, the rail end and the surface of the bolt hole must not have shrinkage cavity, delamination and cracks, and the two ends should be milled flat

5) The wall thickness, surface roughness, roundness and unevenness of steel pipes should meet the technical standards. The threads of threaded steel pipes, galvanized steel pipes and geological pipe joints should be oiled and have protective rings.

6) The galvanized layer of galvanized steel sheets and galvanized steel pipes must not have defects such as cracks, layers, and missing plating.

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