Quality requirements for carbon steel pipes

Quality requirements for carbon steel pipes:

1. Chemical composition

Requirements are put forward for the content of harmful chemical elements As, Sn, Sb, Bi, Pb and gas N, H, O, etc. In order to improve the uniformity of the chemical composition in the steel and the purity of the steel, reduce the non-metallic inclusions in the tube billet and improve its distribution state, the molten steel is often refined by refining equipment outside the furnace, and even the tube billet is remelted and refined by an electroslag furnace.

2. Dimensional accuracy and shape

The geometric ruler method of carbon steel pipes should include the diameter of the steel pipe: wall thickness, ellipticity, length, curvature, inclination of the end face of the pipe, bevel angle and blunt edge, cross-sectional size of the opposite sex steel pipe, etc.

3. Surface quality
The standard specifies the requirements for “surface finish” of carbon steel seamless pipes. Common defects include: cracks, hairlines, inner folds, outer folds, crushing, inner straights, outer straights, separation layers, scars, pits, convex hulls, hemp pits (pimples), scratches (scratches), internal spirals, external spirals, green lines, concave correction, roller printing, etc. Among them, cracks, inner folds, outer folds, crushing, delamination, scarring, pits, convex hulls, etc. are dangerous defects, and pitted surfaces, blue lines, scratches, slight internal and external straight lines, slight internal and external spirals, concave corrections, and roll marks of steel pipes are general defects.

4. Physical and chemical properties
Including mechanical properties at room temperature and at a certain temperature (thermal strength and low temperature properties) and corrosion resistance (such as oxidation resistance,
Water corrosion resistance, acid and alkali resistance, etc.) generally depend on the chemical composition, microstructure and purity of the steel, as well as the heat treatment method of the steel. In some cases, the rolling temperature and degree of deformation of the steel pipe will also affect the performance of the steel pipe.

5. Process performance
Including flaring, flattening, hemming, bending, ring drawing and welding properties of steel pipes.

6. Metallographic structure
Including the low-magnification structure and high-magnification structure of steel pipes.

7. Special requirements
Requirements beyond the standards raised by users when using steel pipes.