1, chemical composition
In order to improve the uniformity of chemical composition and purity of steel, reduce non-metallic inclusions in the pipe and improve its distribution, steel refining is often used by furnace steelmaking equipment, and even the electric slag furnace is used for remelting refining tubes.
2, dimensional accuracy and shape
The geometric dimensions of the seamless steel pipe include the outer diameter of the steel pipe, the thickness of the wall, the ellipticity, the length, the curvature, the angle of the pipe end cutting, the blunt side and the opposite side of the groove angle and the cross section.
3, surface quality
The standard specifies the "smooth surface" requirements for seamless steel tubes. Common defects are: cracks, lines, folds inside, lateral folds, rolling, internal lines, external lines, abscission layers, scars, pits, convex bags, horse pits (horses), scratches (scratches), internal spiral, external spiral, green line, concave, rolling and so on. Which is broken, broken, broken, rolling, from this layer, scars, pits, convex hull and other dangerous defects; the steel wire, the green line, the wear, the inside and outside slightly straight, the inside and outside thread slightly hollow, generally the defective roll.
4, physical and chemical properties
The mechanical properties at a certain temperature and mechanical properties at a certain temperature (heat and low temperature performance) and corrosion resistance in general conditions (such as oxidation, acid resistance, acid resistance and other properties) depend on the chemical composition of steel, the microstructure and purity of the steel, and the heat treatment of steel. In some cases, the rolling temperature and deformation of the steel pipe will also affect the performance of the pipe.
