Steel pipe and human life, production activities are inseparable, steel pipe production in the steel industry occupies an irreplaceable position. From people’s daily utensils, furniture, water supply and drainage, gas supply, ventilation and heating facilities to the manufacture of various agricultural appliances, the development of underground resources, national defense and aerospace guns, bullets, missiles, rockets, etc. are inseparable from the steel pipe.
So how to identify the advantages and disadvantages of steel pipe?
1. Substandard steel tubes are prone to folding. Folding is a variety of folding lines formed on the surface of the steel pipe, this defect is often throughout the longitudinal direction of the product. The reason for folding is due to the pursuit of high efficiency of shoddy manufacturers, the amount of press down is large, resulting in ears, the next rolling on the folding, folding products will crack after bending, the strength of steel will decline.
2. The appearance of shoddy steel pipes often have a pockmarked surface. The pockmarked surface is caused by serious wear and tear of the rolling groove steel surface irregularity of the unevenness of the defect. As a result of shoddy steel pipe manufacturers to pursue profits, there are often the most over-rolled groove rolling.
3. The surface of shoddy steel pipe is prone to scarring. There are two reasons: (1). Shoddy steel pipe material is not uniform, more impurities. (2). Shoddy material manufacturers guide the rudimentary equipment, easy to stick steel, these impurities bite the rollers easy to produce scars.
4 shoddy material surface is prone to cracking, the reason is that its billet is adobe, adobe porosity, adobe in the process of cooling due to thermal stress, resulting in cracks, after rolling on cracks.
5, shoddy steel pipe is easy to scratch, the reason is that shoddy steel pipe manufacturers rudimentary equipment, easy to produce burrs, scratching the surface of the steel. Deep scratches reduce the strength of steel.
6 shoddy steel pipe without metallic luster, light red or similar to the color of pig iron, for two reasons. 2, shoddy material rolling temperature is not standard, their steel temperature is measured visually, so that the austenite area can not be rolled according to the provisions of the natural performance of steel can not meet the standard.
7, shoddy steel pipe crossbar thin and low, often filled with the phenomenon of dissatisfaction, the reason is that manufacturers to achieve large negative tolerances, the finished product before the first few passes of the pressed volume is large, iron type is small, the hole is not filled.
8. The cross-section of the shoddy steel pipe is oval because the manufacturer, in order to save materials, presses down the first two passes of the finished rolls with a large amount of pressure, which greatly reduces the strength of the rebar and does not meet the standard of the rebar shape size.
9. The composition of high-quality steel is uniform, the tonnage of the cold shear is high, and the end face of the cutting head is smooth and neat, while the material is poor, and the end face of the cutting head often has the phenomenon of falling meat, i.e. unevenness, and no metallic luster. And because of the shoddy material manufacturers products cut head less, the head and tail will appear large ears.
10, shoddy steel pipe material containing impurities, steel density is small, and the size of the super poor serious, so in the absence of vernier calipers, it can be weighed to check. For example, for the rebar 20, the national standard provides that the maximum negative tolerance of 5%, fixed 9M, its single theoretical weight of 120 kg, its minimum weight should be: 120 X (l-5%) = 114 kg, weighing out the actual weight of a single than 114 kg is small, it is shoddy steel, because it is negative tolerance of more than 5%. Generally speaking, the whole phase weighing effect will be better, mainly taking into account the cumulative error and probability theory of this issue.
11, the internal diameter of the shoddy steel pipe size fluctuations, the reason is; l, steel temperature instability has Yin and Yang. 2, the composition of the steel is not uniform. 3, due to rudimentary equipment, low strength of the foundation, the mill’s bounce is large. There will be a large change within the same week, so that the steel is unevenly stressed prone to fracture.
12. The trademark and printing of high-quality tubes are more standardized.
13．Three steel pipes with a diameter of 16 or more large threads, the spacing between the two trademarks are above IM.
14 The longitudinal bars of shoddy steel rebar are often wavy.
15. The shoddy steel pipe manufacturers pack more loosely because there is no line drive. The sides are oval-shaped.