Quality requirements of seamless steel tube

Quality requirements of seamless steel tube:

1. Chemical composition

Requirements for harmful chemical elements such as As Sn Sb Bi Pb and gas NHO are required. In order to improve the uniformity of chemical composition in steel and the purity of steel, reduce the non-metallic inclusions of the billet and improve its distribution, furnaces are often used. The external refining equipment refines the molten steel, and even re-melts the tube blank by using an electroslag furnace.

2, Size accuracy and shape
The geometrical dimensions of the seamless steel pipe mainly include the outer diameter, wall thickness, ellipticity, length, curvature, pipe end slope, groove angle and blunt edge of the steel pipe, and the cross-sectional dimensions of the opposite-shaped steel pipe.

3, Surface quality
The requirements for "smooth finish" of seamless steel tubess are specified in the standard. Common defects are: crack, hairline, inflection, outer folding, rolling, inner straight, outer straight, separation layer, crusting, pit, convex hull, pit (pitting), scratch (scratch) , inner spiral track, outer spiral track, blue line, correction, roll printing, etc. Among them, cracks, inflection, external folding, rolling, separation, crusting, pits, convex hulls and other dangerous defects; puncture, blue line, abrasion of steel pipe, slight internal and external straight, slight internal and external spiral, correction Concave and roll printing are general defects.

4, Physical and chemical properties
Including mechanical properties at normal temperature and mechanical properties (heat strength and low temperature properties) and corrosion resistance (such as oxidation resistance, water erosion resistance, acid and alkali resistance) at a certain temperature, generally depends on the chemical composition and structure of the steel. Performance and purity of steel and heat treatment of steel. In some cases, the rolling temperature and degree of deformation of the steel tube also affect the performance of the steel tube.

5. Process performance, including flare, flattening, crimping, bending, ring drawing and welding performance of steel pipes.

6. Metallographic organization, including low-magnification and high-magnification of steel pipes.

7. Special requirements, requirements other than those proposed by the user when using steel pipes.