How to choose seamless pipes
1. Choose a seamless tube with a generally uniform color, smooth and flat inner and outer walls, and no bubbles, depressions, impurities and other defects that affect the surface performance.
2. It depends on whether the logo on the product is complete. The seamless steel pipe must have the manufacturer's name or trademark, production date, product name, seamless pipe sizes, implementation standard number, etc.There should be product name, nominal outer diameter, pipe series, etc. on the seamless steel pipe, the handwriting should be clear, and check whether the mark is consistent with the actual situation.
3. You should buy pipes and fittings of the same brand. Since the raw materials of products of different brands may be different, there will be unfavorable factors for the welding of pipes and fittings, and long-term use will cause leakage at the weld.
4. Good seamless steel pipes have high strength rather than being broken, so the quality of steel pipes cannot be judged by whether they can be broken. Since the impact resistance of seamless steel pipes is better than that of real steel pipes, seamless steel pipes are easier to smash, and those that cannot be smashed are often seamless steel pipes.
In addition, it is also very important to distinguish the advantages and disadvantages of seamless pipes
1. Fake and inferior seamless steel pipes are prone to folding. Folds are various fold lines formed on the surface of seamless steel pipes, and this defect often runs through the longitudinal direction of the entire product.
2. The appearance of fake and inferior seamless steel pipes often has the phenomenon of pockmarking. The pitted surface is the irregular unevenness on the surface of the steel due to the serious wear of the rolling groove.
3. The surface of the fake and inferior seamless steel pipe is prone to scarring. There are two reasons: (1). The material of the fake and inferior seamless steel pipe is uneven and there are many impurities. (2). The guide and guard equipment of the fake and inferior material manufacturers are simple and easy to stick to the steel. These impurities are prone to scarring after biting the roll.
4. The surface of the fake and inferior seamless steel pipe is prone to cracks. The reason is that its blank is adobe, and the adobe has many pores. The adobe is subjected to thermal stress during the cooling process, resulting in cracks. After rolling, there are cracks.
5. Fake and inferior seamless steel pipes are easy to be scratched, because the equipment of fake and inferior seamless steel pipe manufacturers is simple, and it is easy to produce burrs and scratch the surface of steel.
6. The fake and inferior seamless steel pipe has no metallic luster and is light red or similar to pig iron. At the same time, the horizontal bars of the fake and inferior seamless steel pipes are thin and low, and there is often a phenomenon of unsatisfactory filling. The reason is that in order to achieve a large negative tolerance, the reduction amount of the first few passes of the finished product is too large, the iron shape is too small, and the hole shape is unsatisfactory.
7. The cross section of the fake and inferior seamless steel pipe is oval.The reason is that in order to save materials, the reduction amount of the first two passes of the finished roll is too large, the strength of this seamless steel pipe is greatly reduced, and it does not meet the standard of the overall size of the seamless steel pipe.
8. The composition of high-quality seamless steel pipe is uniform, the tonnage of the cold shearing machine is high, and the end face of the cutting head is smooth and neat. However, due to the poor material of the fake and inferior seamless steel pipe, the end face of the cutting head is often uneven and has no metallic luster. And because the products of fake and shoddy manufacturers have less cut heads, big ears will appear on the head and tail.
9. The material of the fake and inferior seamless steel pipe contains a lot of impurities, the density of the steel is too small, and the size is out of tolerance, so it can be weighed and checked without a vernier caliper. Generally speaking, the effect of whole phase weighing will be better, mainly considering the problem of cumulative error and probability theory.
10. The inner diameter of the fake and inferior seamless steel pipe fluctuates greatly, the reasons are: (1) The steel temperature is unstable and there are yin and yang sides. (2) The composition of steel is not uniform. (3) Due to the rudimentary equipment and low foundation strength, the bouncing of the rolling mill is large. There will be a large change in the inner diameter within the same week, and the uneven stress of such a steel bar is prone to fracture.