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


2. Dimensional accuracy and shape
Geometric dimensions of seamless steel pipe mainly include outer diameter, wall thickness, ellipticity, length, curvature, pipe end tangent angle, groove angle and cross section. Blunt edges and opposite.


3. Surface quality
This standard stipulates the requirement of "smooth surface" of seamless steel pipe. Common defects are: cracks, thin lines, inner folds, outer folds, inner straight lines, outer straight lines, layers, scars, pits, bumps, craters (pits), pits (pits), scratches (scratches), internal spirals, outer spirals, green lines, concave surfaces, rolling, etc. From layer, scar, pit, convex shell and other dangerous defects, break, break, break, roll; Plum blossom, green line, wear, slightly straight inside and outside, inside and outside spiral, concave surface, roll edge is a general defect.


4. Physical and chemical properties
Normally, mechanical properties at room temperature and at certain temperatures (heat and low temperature) and corrosion resistance (such as oxidation, acid and acid resistance) depend on the chemical composition, structure and properties, purity of steel and heat treatment of steel. In some cases, the rolling temperature and deformation of steel pipe will also affect the properties of the pipe.