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October 23, 2015

How to choose a steel pipe : identification of steel tube

1. Shoddy Steel Pipe prone to fold.
Fold is formed on the surface of a variety of steel fold, this defect often throughout the product's longitudinal direction. The reason is due to shoddy factory folded pursuit of high efficiency, reduction is too large, resulting in the ears, it creates a rolling fold down when the product will crack when folded bending, the strength of steel big drop.
2. Ma often shoddy steel pipe outer surface phenomenon.
Pock is due to the groove worn steel surface irregularities caused serious irregularities defects. Because of shoddy steel pipe manufacturers to pursue profits, often the most excessive rolling groove.
3. Shoddy steel surface is easy to produce scarring.
There are two reasons: (1). Shoddy steel material uneven impurities. (2). Shoddy material manufacturers guides poorly equipped, easy to stick steel, easy to produce scarring after these impurities roll bite.
4. Too shoddy material surface is easy to crack, because it's blank adobe, adobe many pores, adobe in cooling
Process due to thermal stress, cracks, crack after rolling there.
5. Shoddy steel easily scratched because of shoddy steel pipe manufacturers poorly equipped, prone to glitches, scratches steel surface. Deep scratches reduce the strength of steel.
6. No shoddy steel metallic luster, pale red color of pig iron or similar reasons two two, its stock is adobe. 2, inferior-rolling temperature is not standard, they are visually steel temperature, so the region can not be prescribed by austenite rolling, properties of steel naturally not compliance.
7. Shoddy steel cross ribs thin and low, often sufficient dissatisfaction with the phenomenon, because manufacturers to achieve large negative tolerance, finished in front of a few larger reduction, iron type is too small, pass fully satisfied.
8. Shoddy steel pipe oval cross-section, because the manufacturers in order to save material, the first two tracks finished roll reduction is too large, the strength of this steel is greatly decreased, and does not conform to the standard dimensions of rebar.
9. High-quality steel components of uniform, high tonnage cold shear, cut the head end surface smooth and tidy, but shoddy material due to the material is poor, there are often cut off the meat first end face of the phenomenon, namely uneven, and no metallic luster. And because wood product manufacturers cut shoddy little head, head and tail will be a big ears.
10. Shoddy steel material containing impurities, the density of steel is small, and size tolerance serious, so in the absence of vernier calipers case, you can check it for weighing. For example, for steel 20, the national standards set forth in the maximum negative tolerance of 5%, while its length 9M single theoretical weight of 120 kg, its minimal weight should be: 120 X (l-5%) = 114 The actual weight of the weighing out single smaller than 114 kg, it is shoddy steel, because it is a minus tolerance of 5%. Generally the whole amount commensurate would be better, mainly taking into account the accumulated error and probability theory this problem.
11. Shoddy steel pipe inner diameter fluctuations due; l, steel surface temperature instability of yin and yang. 2, the composition of the steel uneven. 3, due to poor equipment, low-intensity ground, rolling big bounce. There will be big changes in the same week, so easy to produce steel discontinuity break.
12. Trademarks and printing high-quality tube are relatively standardized.
13. Three pipe diameter of more than 16 large thread pitch between the two trademarks are over IM.
14. Inferior longitudinal reinforcement steel rebar often wavy.

15. Shoddy steel pipe manufacturers because there is no traffic, so the package is relatively loose. Side of the oval.


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