1 and shoddy steel prone to collapse. Fold is formed on the surface of steel pipe line, this defect is often the product throughout the vertical. Have folded due to shoddy manufacturers for high efficiency, the amount of pressure is too large, resulting in the ears, when produced under a rolling folding, folding of the product will be cracking after bending, the strength of steel dropped. 2. Ma often shoddy steel exterior surface phenomenon. Pock is due to severe wear and tear caused by the steel rolling groove irregular uneven surface defects. As shoddy steel manufacturers to the pursuit of profit, often the most excessive rolling groove rolling. 3. Inferior steel surface is easy to produce scarring. There are two reasons: (1). Inferior steel material is uneven, impurities. (2). Inferior materials manufacturers guide and guard equipment simple, easy to stick steel, these impurities after the roll bite is easy to produce scarring. 4. Inferior material surface easy to crack, because it is blank adobe, adobe pores more, adobe in the cooling process due to thermal stresses, crack, after rolling through the cracks there. 
 5. Inferior steel is easy to scratch, because the poorly equipped and inferior steel pipe manufacturers, easy to produce glitch, scratch the steel surface. Deep scratches reduce the strength of steel. 
 6. Inferior tube without metallic luster, pale red color of pig iron or the like, for two reasons Second, it is blank adobe. 2, the temperature of rolling is not inferior material standards, their steel temperature is visual, so the region can not be required to be rolled austenitic steel can not be natural performance standards. 
 7. Inferior steel cross bars thin and low, a phenomenon often fully satisfied, because the manufacturers to achieve the large negative tolerances, the finished product before a few relatively large amount of pressure, iron-based small-hole fully satisfied. 
 8. Inferior steel oval cross section appear before, because the manufacturers in order to save materials, finished products before the two rollers of rolling reduction is too large, which greatly decreased the strength of steel, and steel does not conform to standard dimensions. http://www.hbthgg.com Spiral Pipe Spiral Pipe Plant http://www.thgangguan.com 
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