Quality requirements for seamless steel pipes

Quality requirements for smls:

1. Chemical composition

In order to improve the uniformity of the chemical composition in the steel and the purity of the steel, reduce the non-metallic inclusions of the tube blank and improve its distribution state, the molten steel is often refined by the refining equipment outside the furnace, and even the tube blank is reprocessed by the electroslag furnace. Melt refining.

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 carbon steel pipe. 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 folding, external folding, rolling, separation, scarring, pits, convex hulls, etc.; the pitted surface of the steel pipe and the heat treatment method of the 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.

4. Process performance

Including flaring, flattening, crimping, bending, ring pulling and welding properties of steel pipes.

5. Metallographic organization

Including the low magnification and high magnification of the steel pipe.