1. The fake and inferior cold-drawn seamless steel pipe is easy to fold. Folding is a kind of folding line formed on the surface of cold-drawn seamless steel tube. This defect often runs through the longitudinal direction of the whole product. The reason for folding is that fake and inferior manufacturers pursue high efficiency, large reduction, and produce ears. Folding occurs in the next rolling process. Folded products will crack after bending, and the strength of cold-drawn seamless steel tube will decrease greatly. 2.伪劣冷拔无缝钢管外表经常有麻面现象。麻面是由于轧槽磨损严重引起冷拔无缝钢管表面不规则的凹凸不平的缺陷。由于伪劣冷拔无缝钢管厂家要追求利润，经常出现轧槽轧制最超标。
2. The appearance of fake and inferior cold-drawn seamless steel tubes often has hemp surface. The flake surface of cold-drawn seamless steel pipe is irregular and uneven because of serious groove wear. As the fake and inferior cold-drawn seamless steel pipe manufacturers want to pursue profits, groove rolling often appears to exceed the standard.
3. Scar is easily formed on the surface of cold-drawn seamless steel tubes. There are two reasons: 1. The quality of fake and inferior cold-drawn seamless steel tube is not uniform and there are many impurities. 2. The guide equipment of fake and inferior material manufacturers is simple and easy to stick to steel. These impurities bite the roll and cause scarring easily.
4. Cracks are easy to occur on the surface of fake and inferior materials. The reason is that the billet is adobe and there are many air holes in the adobe. During the cooling process, the adobe is subjected to thermal stress, resulting in cracks, and there are cracks after rolling.
5. The fake and inferior cold-drawn seamless steel pipe is easy to scratch, because the fake and inferior material manufacturer's equipment is simple, easy to produce burrs, scratch the surface of cold-drawn seamless steel pipe. Deep scratch reduces the strength of cold-drawn seamless steel tubes.
6. The fake and inferior cold-drawn seamless steel pipe has no metallic luster and is light red or similar to pig iron. There are two reasons. Its blank is adobe. 2. The rolling temperature of fake and inferior steel is not standard. Their steel temperature is measured by visual method, so it can't be rolled according to the prescribed austenite area, so the performance of cold-drawn seamless steel tube can't reach the standard naturally.
7. The transverse bars of fake and inferior cold-drawn seamless steel tubes are thin and low, and the phenomenon of filling is often unsatisfactory. The reason is that in order to achieve a large negative tolerance, the manufacturer has a large reduction in the first several passes of the finished products, a small iron shape and a unsatisfactory filling of the passes.
8. The cross-section of the fake and inferior cold-drawn seamless steel pipe is elliptical. The reason is that in order to save material, the reduction of the front two passes of the finished roll is too large. The strength of this kind of thread steel decreases greatly, and it does not conform to the standard of the shape and size of the thread steel.
9. High-quality cold-drawn seamless steel pipe has uniform composition, high tonnage of cold shearing machine, smooth and neat end face of cutting head, while fake and inferior materials, due to poor material quality, often have the phenomenon of meat loss at the end face of cutting head, that is, uneven, and no metallic luster. And because the products of fake and inferior material manufacturers cut little, big ears will appear at the end.
10.伪劣冷拔无缝钢管材质含杂质多，钢的密度偏小，而且尺寸超差严重，所以在没有游标卡尺的情况下，可以对它进行称量核对。比如对于螺纹钢 20，国家标准中规定最大负公差为 5%，定尺9M时它的单根理论重量为 120公斤，它的最小的重量应该是：120 X(l-5%)=114公斤，称量出来单根的实际重量比114公斤小，则是伪劣冷拔无缝钢管，原因是它负公差超过了5%。一般来说整相称量效果会更好，主要考虑到累积误差和概率论这个问题。
10. The fake and inferior cold-drawn seamless steel pipe material contains many impurities, the density of the steel is small, and the dimension is excessive, so it can be weighed and checked without vernier calipers. For example, for screw steel 20, the national standard stipulates that the maximum negative tolerance is 5%, and the theoretical weight of a single pipe is 120 kg at a fixed length of 9M. Its minimum weight should be 120 X (l-5%) = 114 kg. The actual weight of a single pipe weighed out is smaller than 114 kg. It is a pseudo-inferior cold-drawn seamless steel pipe, because its negative tolerance exceeds 5%. Generally speaking, the effect of integer phase weighing is better, mainly considering the problem of cumulative error and probability theory.
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