Large quantities of seamless pipes & tubes are used in daily building construction, seamless pipes can be applied to fluid conveying pipes, boiler plants, engineering, mechanical processing and other fields. Good seamless pipes are not only reflected in their service life, but also It will also be relatively strong during use, on the contrary, inferior seamless pipes will have various problems during use. In fact, how about its quality, we still need to see the real thing, so that it is convenient for us to measure the quality. So how to choose high-quality steel pipes? The following carbon steel pipe manufacturers will take you to understand how to identify the advantages and disadvantages of seamless pipes:
1. Pimples often appear on the surface of inferior seamless steel pipes. Pockmarked surface is due to the severe wear of the rolling groove, resulting in irregular concave and convex defects on the steel surface. Because low-quality steel pipe manufacturers want to pursue profits, rolling phenomenon often occurs.
2. Inferior seamless steel pipes are easy to scratch, because the production equipment of inferior steel pipe manufacturers is not perfect, the products are prone to burrs, scratches on the steel surface, and deep scratches will reduce the strength of the steel.
3. The surface of inferior seamless steel pipes is prone to scarring. There are two main reasons for this: First, the inferior seamless steel pipe has more impurities and uneven material. The second is that the poor-quality steel pipe factory guides and guards are poorly equipped, especially easy to stick to steel, and the pipe containing impurities is prone to scarring after biting into the roll.
4. Inferior seamless steel pipes are prone to pipe breakage. The folds we are talking about are various fold lines formed on the surface of the seamless steel pipe, and this defect usually runs through the entire product. The reason for folding is that manufacturers pursue high efficiency to increase output. If the pressure is too high during the production process, it will be easy to bend during the next rolling. The half-folded product is easy to crack after bending, resulting in a significant reduction in the strength of the pipe.
5. The surface of inferior pipes is prone to cracks. One of the reasons is that the blank is adobe, and the adobe has many pores. During cold rolling, cracks are generated due to the action of thermal stress, and cracks appear after rolling.
6. The section shape of inferior seamless steel pipe is irregular, and the error of ellipticity is large. In order to increase the output of the factory, the reduction in the first two passes of the finished roll is too large, the strength of the seamless steel pipe is greatly reduced, and it does not meet the standard for the shape and size of the seamless steel pipe.
7. The surface of inferior seamless steel pipe has no metallic luster, and it is light red or similar to pig iron. There are two reasons: the billet is adobe. The second is that the rolling temperature of inferior materials does not meet the standards. The steel temperature cannot be rolled according to the specified austenite zone through visual inspection, and the properties of the steel naturally do not meet the requirements.
8. The horizontal ribs of inferior seamless steel pipes are thin and low, and inflation often occurs. The reason is that in order to achieve a large negative tolerance, the manufacturer has a large reduction in the first few passes of the finished product and a small pass shape.
9. The composition of high-quality steel is uniform, the specification of the pipe cutting machine is high, and the end surface of the cutting head is flat, while the inferior material is often uneven and has no metallic luster when cutting the head due to poor material. And because the products of inferior material manufacturers have fewer heads, big ears will appear at the head and tail.
10. Inferior seamless steel pipe materials contain a lot of impurities, the density of steel grades is low, and the size is seriously out of tolerance. Therefore, weighing inspection can be carried out without a vernier caliper. For example, for rebar 20, the national standard stipulates that the maximum negative tolerance is 5%. When the length is 9M, the single theoretical weight is 120 kg, and the minimum weight is 120X (l-5%) = 114 kg. The actual weight of the weighed steel is less than 114 kg, which is inferior steel, because the negative tolerance exceeds 5%. In general, the overall weighing effect is better, mainly considering the cumulative error and probability theory.
11. The inner diameter of inferior seamless steel pipes fluctuates greatly because the steel temperature is unstable. The composition of the steel is not uniform. Due to the poor equipment of the mill, the foundation strength is low and the elasticity is large. There will be large changes in the same week, so the seamless steel pipe will be unevenly stressed and prone to breakage.
12. The trademark and printing of high-quality seamless steel pipes are more standardized.