4.1. Specifications: The outer diameter of the hot-rolled tube is 32-630mm. Wall thickness 2.5 ~ 75mm. Cold-rolled (cold-drawn) tube outer diameter 5 ~ 200mm. Wall thickness 2.5 ~ 12mm.

4.2. Appearance quality: There must be no cracks, folds, rolling folds, delamination, hairlines and scarring defects on the inner and outer surfaces of steel pipes. These defects should be completely removed, and the wall thickness and outer diameter must not exceed the negative deviation after removal.

4.3. Both ends of the steel pipe should be cut at right angles, and the burrs should be removed. Steel pipes with a wall thickness greater than 20mm are allowed to be cut by gas cutting and hot sawing. It is not necessary to cut the head after the agreement between the supply and demand parties.

4.4. Refer to GB3639-83 for "Surface Quality" of cold-drawn or cold-rolled precision seamless steel pipes.