1. The surface of inferior seamless pipes is prone to scarring.
Mainly due to two reasons:
(1) Inferior seamless pipes have more impurities and uneven materials.
(2) The guide equipment of inferior pipe manufacturers is simple and easy to stick to steel. Pipes containing impurities are prone to scarring after biting into the rollers.
2. Inferior seamless pipes are prone to pipe folding.
The so-called folds are various fold lines formed on the surface of seamless pipes. This defect often runs throughout the longitudinal direction of the entire product. The reason for folding is that in order to increase production and pursue high efficiency, the manufacturer presses too much during the production process, causing ears, which will easily cause folding during the next rolling process. The folded product is prone to cracking after bending, resulting in a significant reduction in the strength of the pipe.
3. Inferior seamless pipes are prone to scratches. The reason is that due to poor production equipment of inferior steel pipe manufacturers, the products are prone to burrs and scratches on the steel surface. Deep scratches will reduce the strength of the steel.
4. The surface of inferior seamless pipes is often pitted.
Pockmarking is an irregular uneven defect on the steel surface caused by severe wear of the rolling groove. As inferior steel pipe manufacturers pursue profits, groove rolling often exceeds the standard.
5. The surface of inferior pipes is prone to cracks. One of the reasons is that its raw material is adobe, which has many pores. During the cooling process, cracks occur due to thermal stress, and cracks appear after rolling.
6. Inferior seamless pipes have no metallic luster and are light red or similar in color to pig iron. There are two reasons:
(1) Its blank is adobe.
(2) The rolling temperature of inferior materials is not standard. Their steel temperature is measured visually, so rolling cannot be carried out according to the specified austenite area, and the performance of the steel will naturally not meet the standards.
7. The transverse ribs of inferior seamless pipes are thin and low, and they often appear to be underfilled. The reason is that in order to achieve a large negative tolerance, the manufacturer's reduction in the first few passes of the finished product is too large, the iron shape is too small, and the hole pattern is not fully filled.
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 neat. However, due to poor material quality, the end face of the cutting head often appears uneven and has no metallic luster.
9. The cross-section of inferior seamless pipes is irregular and the ovality error is large. The reason is that in order to increase the output, the manufacturer uses a large reduction amount in the first two passes of the finished roller. The strength of this seamless steel pipe is greatly reduced, and it does not meet the standards for the appearance and size of seamless pipes.
10. Inferior seamless steel pipe material contains many impurities, the density of the steel is small, and the size is seriously 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 fixed length is 9M, its theoretical weight of a single rod is 120 kg. Its minimum weight should be: 120 X (l-5%) = 114 kg , the actual weight of a single piece is smaller than 114 kilograms, which means it is inferior steel because its negative tolerance exceeds 5%. Generally speaking, the effect of phase-integrated weighing will be better, mainly considering the issues of cumulative error and probability theory.
11. The inner diameter of inferior seamless pipes fluctuates greatly because;
(1) There are yin and yang sides to the unstable steel temperature.
(2) The composition of steel is uneven.
(3) Due to the crude equipment and low foundation strength, the rolling mill has a large bounce. There will be large changes within the same week, and such seamless pipes will be prone to fracture due to uneven stress.
12. The trademarks and printing of high-quality seamless pipes are relatively standardized.
13. Inferior seamless steel pipe manufacturers have no driving, so the packaging is relatively loose and the sides are oval.
Mainly due to two reasons:
(1) Inferior seamless pipes have more impurities and uneven materials.
(2) The guide equipment of inferior pipe manufacturers is simple and easy to stick to steel. Pipes containing impurities are prone to scarring after biting into the rollers.
2. Inferior seamless pipes are prone to pipe folding.
The so-called folds are various fold lines formed on the surface of seamless pipes. This defect often runs throughout the longitudinal direction of the entire product. The reason for folding is that in order to increase production and pursue high efficiency, the manufacturer presses too much during the production process, causing ears, which will easily cause folding during the next rolling process. The folded product is prone to cracking after bending, resulting in a significant reduction in the strength of the pipe.
3. Inferior seamless pipes are prone to scratches. The reason is that due to poor production equipment of inferior steel pipe manufacturers, the products are prone to burrs and scratches on the steel surface. Deep scratches will reduce the strength of the steel.
4. The surface of inferior seamless pipes is often pitted.
Pockmarking is an irregular uneven defect on the steel surface caused by severe wear of the rolling groove. As inferior steel pipe manufacturers pursue profits, groove rolling often exceeds the standard.
5. The surface of inferior pipes is prone to cracks. One of the reasons is that its raw material is adobe, which has many pores. During the cooling process, cracks occur due to thermal stress, and cracks appear after rolling.
6. Inferior seamless pipes have no metallic luster and are light red or similar in color to pig iron. There are two reasons:
(1) Its blank is adobe.
(2) The rolling temperature of inferior materials is not standard. Their steel temperature is measured visually, so rolling cannot be carried out according to the specified austenite area, and the performance of the steel will naturally not meet the standards.
7. The transverse ribs of inferior seamless pipes are thin and low, and they often appear to be underfilled. The reason is that in order to achieve a large negative tolerance, the manufacturer's reduction in the first few passes of the finished product is too large, the iron shape is too small, and the hole pattern is not fully filled.
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 neat. However, due to poor material quality, the end face of the cutting head often appears uneven and has no metallic luster.
9. The cross-section of inferior seamless pipes is irregular and the ovality error is large. The reason is that in order to increase the output, the manufacturer uses a large reduction amount in the first two passes of the finished roller. The strength of this seamless steel pipe is greatly reduced, and it does not meet the standards for the appearance and size of seamless pipes.
10. Inferior seamless steel pipe material contains many impurities, the density of the steel is small, and the size is seriously 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 fixed length is 9M, its theoretical weight of a single rod is 120 kg. Its minimum weight should be: 120 X (l-5%) = 114 kg , the actual weight of a single piece is smaller than 114 kilograms, which means it is inferior steel because its negative tolerance exceeds 5%. Generally speaking, the effect of phase-integrated weighing will be better, mainly considering the issues of cumulative error and probability theory.
11. The inner diameter of inferior seamless pipes fluctuates greatly because;
(1) There are yin and yang sides to the unstable steel temperature.
(2) The composition of steel is uneven.
(3) Due to the crude equipment and low foundation strength, the rolling mill has a large bounce. There will be large changes within the same week, and such seamless pipes will be prone to fracture due to uneven stress.
12. The trademarks and printing of high-quality seamless pipes are relatively standardized.
13. Inferior seamless steel pipe manufacturers have no driving, so the packaging is relatively loose and the sides are oval.
