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Precision Cold-drawn Steel Pipe Surface Quality Defects
Jun 06, 2018

1 Outer fold: The spiral sheet-like folds appear on the outer surface of the cold-drawn steel tube. Its spiral direction is opposite to the direction of rotation of the steel when piercing, and the pitch is large. This kind of defect is called outer fold.

2. Cracks: The inner and outer surfaces of the cold-drawn steel tube appear continuous or discontinuous small hair-like, and some are y-shaped. The rotation direction is opposite to the rotation direction of the steel when piercing and the pitch is relatively large. This kind of defect is called a crack. .

3. Separation layer: In the inner surface of a cold-drawn steel tube, a spiral shape or a blocky metal layer is stratified or broken or a tantalum defect. This defect is called separation.

4. Inward folding: In the inner surface of a cold-drawn steel tube, spiral, semi-spiral, and irregularly distributed saw-tooth-like folds appear. This defect is called inner folding.

5. Scarring (including scales, cracks, and chaffs): On the inner surface of cold-drawn steel tubes, there are angular scars, which are called scars.

6. Scratching (bracing): The internal and external surfaces of the steel tube are cold-drawn and a linear groove pattern is regularly distributed. This defect is called scratching (bracing).

7. Folding: The wrinkles in the outer recesses are partially or continuously formed along the longitudinal direction of the pipe wall, and the outer surface is strip-shaped. This kind of defect is called rolling.

8. Plunge (profiling): On the surface of the cold-drawn steel tube, a spiral sag is present. This defect is known as a correction (straightening), also known as threading (straightening).

9. Glitch: A full or partial residual zigzag lamella in the circumferential direction of the cold drawn steel tube ends. This defect is called a burr.

10. Uneven wall thickness: There is a phenomenon that the cross-section and longitudinal thickness of the cold-drawn steel pipe are not equal. This kind of defect is called uneven wall thickness.

11. Dynamia (also known as ripple, bamboo-shaped, ring-shaped): On the inner and outer surfaces of cold-drawn steel tubes, there are continuous and intermittent ring marks that are uneven along the transverse direction. Only on the surface, this kind of defect is called dithering (also known as ripple, bamboo, ring).

12. Pits (including indentations): Localized pits of varying sizes appear on the surface of cold-drawn steel tubes, some of which are periodic and some are irregular. The surface of the defect has a dent as a pit, and the surface has no dents as an indentation.

13. Pockmark (also known as pockmark): A small, punctiform dent in the surface of a cold-drawn steel tube. This defect is referred to as pitting.

14. Straight: A linear scratch with a certain width and depth is present on the inner and outer surfaces of a cold-drawn steel tube, distributed over the entire length or part of the cold drawn steel tube. This defect is called a straight path.

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