1. Chemical Constituents
In order to improve the homogeneity of chemical composition and purity of steel, reduce non-metallic inclusions in steel tubes and improve their distribution, steel refining is often used in steelmaking equipment, and even electroslag furnace is used for remelting refining tubes.


2. Dimensional accuracy and shape
Geometric dimensions of seamless steel pipe include outer diameter, wall thickness, ellipticity, length, curvature, cutting angle of pipe end, relative lateral angle of blunt end and groove and cross section.


3. Surface quality
This standard stipulates the requirement of "smooth surface" of seamless steel pipe. Common defects are: cracks, lines, inner folds, side folds, rolling, internal lines, external lines, exfoliation, scars, pits, convex bags, pits (horses), scratches (scratches), internal spirals, external spirals, green lines, concave, rolling, etc. From this layer, scars, pits, convex hulls and other dangerous defects are broken, broken, broken, rolled; steel wire, green line, wear, slightly straight inside and outside, slightly hollow inside and outside threads, generally defective rolls.


4. Physical and chemical properties
Mechanical properties at a certain temperature and mechanical properties at a certain temperature (thermal and low temperature properties) and corrosion resistance under general conditions (such as oxidation, acidity, acidity and other properties) depend on the chemical composition of the steel, the microstructure and purity of the steel, and the heat treatment of the steel. In some cases, the rolling temperature and deformation of steel pipe also affect the properties of the pipe.