Seamless steel pipe quality requirements in production

In the production of steel pipes, ensuring the quality and performance of the products is crucial. Here are the quality requirements and control methods for steel pipes in several key aspects.

Chemical Composition

To improve the uniformity of chemical composition and the purity of steel, reduce the non-metallic inclusions in the tube, and improve their distribution, furnace refining equipment is often used for refining molten steel. In some cases, electroslag remelting is employed to further refine the tube.

Dimensional Accuracy and Shape

The geometric dimensions of seamless steel pipes mainly include the outer diameter, wall thickness, ovality, length, curvature, cut angle of the pipe end, groove angle, and the cross-section of the blunt edge.

Surface Quality

Standards specify the "smooth surface" requirements for seamless steel tubes. Common defects include cracks, hairlines, internal and external folds, rolling marks, internal and external straightness issues, delamination, scarring, pits, convex hulls, rough surfaces, scratches, internal and external spirals, green lines, concave areas, and rolling defects. Among these, cracks, breaks, rolling defects, delamination, scarring, pits, and convex hulls are considered dangerous defects. Minor defects include slight internal and external straightness issues, slight internal and external spirals, concave areas, rolling defects, rough surfaces, and abrasions.

Physical and Chemical Properties

These include mechanical properties at room temperature, mechanical properties at specific temperatures (thermal and low-temperature performance), and corrosion resistance (such as oxidation and acid resistance). These properties generally depend on the steel's chemical composition, microstructure, purity, and heat treatment. In some cases, the rolling temperature and deformation of the steel pipe can also impact its performance.