For the finished
seamless steel pipe, some inspections must be done before leaving the factory, such as the chemical composition of the steel pipe product, the dimensional accuracy of the steel pipe product, and the water pressure test, spectral flaw detection and other aspects. Similarly, when purchasing seamless steel pipes, the user of seamless pipe products should also do some simple acceptance of seamless pipe products, check the production standards of steel pipe grades, check the specifications of seamless pipes, measure the dimensional accuracy of seamless steel pipes and the number of steel pipes. check acceptance.
1. Chemical composition
Requirements are put forward for the content of harmful chemical elements As, Sn, Sb, Bi, Pb and gases N, H, O, etc., in order to improve the uniformity of chemical composition in steel and the purity of steel.
To reduce the non-metallic inclusions in the tube blank and improve its distribution, the molten steel is often refined by out-of-furnace refining equipment, and even the tube blank is remelted and refined by an electroslag furnace.
2. Dimensional accuracy and shape
The geometric dimensions of the seamless steel pipe mainly include the outer diameter, wall thickness, ovality, length, curvature, cut slope, groove angle and blunt edge of the steel pipe, and the cross-sectional size of the heterosexual steel pipe.
3. Surface quality
The standard specifies the requirements for the "smooth surface" of seamless steel pipes. Common defects are: cracks, hair lines, inner folds, outer folds, rolling, inner straights, outer straights, delaminations, scars, pits, convex hulls, pits (pockets), scratches (scuffs) , Inner spiral, outer spiral, blue line, concave correction, roll printing, etc. Among them, there are dangerous defects such as cracks, internal folds, external folds, rolling, separation, scarring, pits, and convex hulls; Concave and roll printing are general defects.
4. Physical and chemical properties
Including mechanical properties at room temperature and mechanical properties at a certain temperature (thermal strength properties and low temperature properties) and corrosion resistance properties (such as oxidation resistance, water corrosion resistance, acid and alkali resistance, etc.) Generally, it depends on the chemical composition and structure of the steel. Properties and purity of steel and heat treatment of steel, etc. In some cases, the rolling temperature and degree of deformation of the steel pipe will also affect the performance of the steel pipe.
5. Process performance
Including flaring, flattening, crimping, bending, ring pulling and welding properties of steel pipes.
6. Metallographic organization
Including the low magnification and high magnification of the steel pipe.
7. Special requirements
Requirements other than the standard put forward when the user uses the steel pipe.
