Use the naked eye to distinguish high-quality seamless steel tubes from inferior seamless steel tubes

1. Inferior quality seamless steel pipes are prone to scars.
Mainly due to two reasons:
(1) Inferior seamless steel pipes have many impurities and uneven materials.
(2) Inferior pipe manufacturers have a simple guide and guard equipment, which is especially easy to stick to steel, and the pipe containing impurities is easy to cause scars after biting into the roll.

2. Inferior quality seamless steel pipes are prone to pipe folding.

The so-called folding refers to the various fold lines formed on the surface of seamless steel pipes. Such defects often run through the longitudinal direction of the entire product. The reason for the folding is that the manufacturer pursues high efficiency to increase the output. During the production process, the amount of pressing is too large, resulting in ears, and folding is easy to occur in the next rolling process. The folded product is easy to crack after bending, which causes the strength of the pipe to be greatly reduced.

3. Inferior quality seamless steel pipes are prone to scratches. The reason is that the production equipment of inferior steel pipe manufacturers is simple and the products are prone to burrs and scratch the surface of the steel. Deep scratches will reduce the strength of the steel.

4. Inferior quality seamless steel pipes often have to pit on the surface.

The pitted surface is the irregularity of the surface of the steel due to the serious wear of the rolling groove. Because inferior steel pipe manufacturers are pursuing profits, groove rolling often exceeds the standard.

5. Inferior pipes are prone to cracks on the surface. One of the reasons is that the blanks are adobes with many pores. In the process of cooling, due to the effect of thermal stress, cracks are generated, and there are cracks after rolling.

6. Inferior seamless steel pipes have no metallic luster and are light red or similar to pig iron. There are two reasons:
(1) Its blank is adobe.
(2) The rolling temperature of inferior materials is not standard, and their steel temperature is visually inspected. In this way, rolling cannot be carried out in the specified austenite area, and the performance of the steel will naturally not meet the standard.

7. Inferior quality seamless steel pipes have thin and low transverse ribs, and often appear dissatisfied. The reason is that to achieve a large negative tolerance, the reduction of the first few passes of the finished product is too large, the iron-type is too small, and the hole type is not full.

8. The composition of high-quality steel is uniform, the specifications of the pipe cutting machine are high, and the end face of the cutting head is smooth and tidy. However, due to the poor material, the end face of the cutting head often has meat loss, that is, it is uneven and has no metallic luster. Moreover, because the products of inferior material manufacturers have fewer cuts, big ears will appear at the head and tail.

9. Inferior seamless steel pipes have irregular cross-sections and large ovality errors. The reason is that to increase the output of the manufacturer, the reduction 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 seamless steel pipe dimensions.

10. The material of inferior seamless steel pipe contains many impurities, the density of steel is too small, and the size is severely out of tolerance, so it can be weighed and checked 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, its single theoretical weight is 120 kg. Its minimum weight should be: 120 X (l-5%) = 114 kg, The actual weight of a single piece weighed out is less than 114 kg, which is poor quality steel because its negative tolerance exceeds 5%. Generally speaking, the whole phase weighing effect will be better, mainly considering the problem of cumulative error and probability theory.

11. The inner diameter size of inferior seamless steel pipe fluctuates greatly because of:
(1) The steel temperature is unstable and has a negative and positive side.
(2) The composition of steel is not uniform.
(3) Due to the simple equipment, the foundation strength is low, and the rolling mill bounces greatly. There will be large changes in the same week, and such seamless steel pipes are prone to fracture due to uneven stress.

12. The trademarks and printing of high-quality seamless steel pipes are relatively standardized.

13. Inferior seamless steel pipe manufacturers have loose packaging due to no driving. The side is oval.