Quality requirements of seamless steel tubes
Quality requirements of seamless steel tubes
1. Chemical composition of seamless steel pipe
The requirements for the contents of harmful chemical elements As Sn Sb Bi Pb and gas NHO are put forward. In order to improve the uniformity of the chemical composition in the steel and the purity of the steel, reduce the non-metallic inclusions in the tube blank and improve its distribution, the furnace is often used The external refining equipment refines the molten steel, and even uses an electroslag furnace to remelt the tube blank.
2. Dimensional accuracy and shape of seamless steel tubes
The geometric dimensions of the seamless steel pipe mainly include the outer diameter, wall thickness, ellipse, length, bending, pipe end face cut slope, groove angle and obtuse edge of the steel pipe, and the cross-sectional size of the heterogeneous steel pipe.
3. Surface quality of seamless steel tubes
The standard stipulates the requirements for "smooth surface" of seamless steel pipes. Common defects are: cracks, hair lines, inner folds, outer folds, crushed, inner straight, outer straight, delamination, scars, pits, convex hulls, pits (pitting), scratches (scratch) , Inner spiral path, outer spiral path, blue line, concave correction, roller printing, etc. Among them are cracks, inner folds, outer folds, crushing, delamination, scars, pits, convex hulls and other dangerous defects; pitted surface, green line, scratches, slight internal and external straight lines, slight internal and external spirals, correction Concave and roller printing are general defects.
4. Physical and chemical properties of seamless steel tubes
Including the mechanical properties at room temperature and the mechanical properties (heat strength performance and low temperature performance) and corrosion resistance (such as oxidation resistance, water corrosion resistance, acid and alkali resistance, etc.) under normal conditions generally depend on the chemical composition and structure of steel Performance and purity of steel and heat treatment of steel. In some cases, the rolling temperature and the degree of deformation of the steel pipe will also affect the performance of the steel pipe.
5. Process performance of seamless steel pipe
Including the flaring, flattening, crimping, bending, ring drawing and welding performance of steel pipes.
6. Metallographic structure of seamless steel pipe
Including low and high magnification of steel tubes.
7. Special requirements for seamless steel tubes
Requirements beyond the standards proposed by users when using steel pipes.