Usually manufacturers produce the following quality requirements for seamless steel tubes
1. Chemical composition. Requirements for the contents of harmful chemical elements As, Sn, Sb, Bi, Pb and gases 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 of the tube blank and To improve its distribution status, the refining equipment outside the furnace is usually used to refine the molten steel, and even the electroslag furnace is used to remelt the tube billet.
2. Dimensional accuracy and shape. The geometric dimensions of the seamless steel pipe mainly include the outer diameter, wall thickness, ellipse, length, bending, pipe end face cut slope, bevel angle and blunt edge of the steel pipe, and the cross-sectional size of the heterogeneous steel pipe.
3. Surface quality. The standard stipulates the requirements for the smooth surface of seamless steel tubes. Common defects include cracks, hair lines, inner folds, outer folds, crushing, inner straights, outer straights, delaminations, scars, pits, bulges, hemp Pit (pitted surface), scratch (scratch), inner spiral path, outer spiral path, blue line, concave correction, roller printing, etc. Among them, cracks, inner folds, outer folds, crushing, delamination, scars, pits, convex hulls, etc. are dangerous defects; pitted surface, green line, scratches, slight inner and outer straight lines, slight inner and outer spirals, correction Concave and roller printing are general defects.
4. Physical and chemical properties. Including the mechanical properties at room temperature and the mechanical properties and corrosion resistance at a certain temperature, generally depends on the chemical composition of the steel, organizational properties and purity of the steel, as well as the heat treatment method of the steel. In some cases, the rolling temperature and the degree of deformation of the steel pipe will also affect the performance of the steel pipe.
5. Process performance. Including the flaring, flattening, curling, bending, ring pulling and welding performance of steel pipes.
6. Metallographic organization. Including the low-power structure and high-power structure of steel pipes.
7. Special requirements. Requirements beyond the standards proposed when using steel pipes.