1. Small longitudinal fissure
The shape of the small longitudinal cracks on the surface layer of the cold drawn steel pipe is less than 200mm in length, less than 3mm in total width, and less than 0.3mm in the deep layer.
2. Peak crack
All the cracks are generated at 5-60mm from the edge of the cold drawn steel pipe, and the macroeconomic orientation and the cold rolled orientation are vertical, showing a "high mountain" shape.
3. Cracks in the border line
The key to this crack is the 20-80mm from the edge of the cold drawn steel tube, and the shape is several parallel vertical cracks of different sizes. The regularity is that the thicker and wider the size of the cold drawn steel tube, the more serious this type of disadvantage is. .
4. Miscellaneous, scab
The impurities and scabs spread periodically, and the condition after the actual operation of casting and rolling is obvious after the inspection of edge flame peeling cracks or the removal of slab scratches and flames.
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