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1.The folding is easy to happen with inferior steel tube. Folding is formed on the surface of the pipe line, this kind of defect often throughout the entire product longitudinal. The reason for causing of fold is due to the pursuit of high efficiency, large reduction of the inferior manufacturer, when go on the next rolling, the folding happens, and the folding products will be cracking after bending, and the strength of steel will decreased
2. The inferior steel tube has pitted surface. Pits is due to the defects of the irregular uneven steel surface caused by the worn groove. Because of the pursuit of profit, the inferior steel pipe manufacturer often appear the overweight groove rolling.
3. The inferior steel tube surface are prone to scarring.
(1) the inferior steel pipe material uneven with impurities.
(2)The inferior material manufacturer with simple equipment which is easy to stick steel, these impurities after the roll bite are prone to scarring.
4. The surface of the inferior material is easy to have crack for the reason that it’s blank is adobe, and in the process of cooling due to the effect of thermal stress, cracks, after rolling, there is crack.
5. The inferior steel pipe is easy to scratch for the reason that the inferior steel pipe factory has simple equipment which is easy to produce burr and scratch steel surfaces. The deep scratches will reduce the strength of the steel.
6. The inferior steel tube has no metallic luster, it is reddish or similar to the color of the pig iron for its original material is adobe. And the characteristics of steel pipe cannot reach the required standard.
7. The transverse bar of the inferior steel pipe is thin and low, and often appear phenomenon of discontent, because the manufacturers want to achieve big minus tolerance, finished product quality is not in accordance with the standard.