Method for identifying counterfeit and inferior thick-walled seamless steel pipes

With the increase in the use frequency of thick-walled seamless steel pipes in industry and life, the purchase of thick-walled seamless steel pipes has gradually increased, and manufacturers of thick-walled seamless steel pipes on the market have also emerged. Seam steel pipes are also mixed, so how can we select the thick-walled seamless steel pipes with good quality and service life from among the many thick-walled seamless steel pipes? The following are the identification methods of some thick-walled seamless steel pipes.

1. Fake and inferior thick-walled seamless steel pipes are prone to folding. Folds are various fold lines formed on the surface of the thick-walled seamless steel pipe, and this defect often runs through the longitudinal direction of the entire product. The reason for the folding is that the counterfeit and inferior manufacturers pursue high efficiency, the reduction amount is too large, and the ears are formed. Folding occurs during the next rolling, and the folded product will crack after being bent, and the strength of the thick-walled seamless steel pipe is greatly reduced.

2. The appearance of fake and inferior thick-walled seamless steel pipes often has a pockmarked surface. The pockmarked surface is the irregular uneven surface of the thick-walled seamless steel pipe due to serious wear of the rolling groove. Due to the pursuit of profit by manufacturers of fake and inferior thick-walled seamless steel pipes, groove rolling often exceeds the standard.

3. The surface of the fake and inferior thick-walled seamless steel pipe is prone to scarring. There are two reasons: 1. Fake and inferior thick-walled seamless steel pipes have uneven material and 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 material is prone to cracks. The reason is that its blank is adobe, and the adobe has many pores. During the cooling process, the adobe is subjected to thermal stress, resulting in cracks. After rolling, there are cracks.

5. Fake and inferior thick-walled seamless steel pipes are easy to be scratched because the fake and inferior material manufacturers have simple equipment, which is easy to produce burrs and scratch the surface of thick-walled seamless steel pipes. Deep scratches reduce the strength of thick-walled seamless steel pipes.

6. The fake and inferior thick-walled seamless steel pipe has no metallic luster and is light red or similar to pig iron. There are two reasons for it. Its blank is adobe. 2. The rolling temperature of fake and inferior materials is not standard, and their steel temperature is measured visually so that it cannot be rolled according to the specified austenite area, and the performance of thick-walled seamless steel pipes will naturally fail to meet the standard.

7. The transverse bars of the fake and inferior thick-walled seamless steel pipes are thin and low, and the phenomenon of full filling often occurs. 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 whole shape is filled. dissatisfied.

8. The cross-section of the fake and inferior thick-walled 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. Dimensions are standard.

9. The composition of high-quality thick-walled 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, while the end face of the cutting head often has the phenomenon of falling meat due to the poor material of the fake and inferior material, that is, unevenness and no surface. Metallic luster. And because the products of the fake and inferior material manufacturers have fewer cutting heads, there will be big ears at the head and tail.

10. The material of the fake and inferior thick-walled 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. For example, for rebar 20, the national standard stipulates that the negative tolerance is 5%. When the fixed length is 9M, its single theoretical weight is 120 kg, and its minimum weight should be: 120 X (l-5%) = 114 kg, If the actual weight of a single piece is less than 114 kg, it is a fake and inferior thick-walled seamless steel pipe because its negative tolerance exceeds 5%. Generally speaking, the effect of whole phase weighing will be better, mainly considering the problem of cumulative error and probability theory.

11. The inner diameter of the fake and inferior thick-walled seamless steel pipe fluctuates greatly, the reason is l. The

el temperature is unstable and there are yin and yang sides. 2. The composition of steel is not uniform. 3. Due to the simple equipment and low foundation strength, the rolling mill bounces greatly. 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.

12. The trademark and printing of high-quality materials are relatively standardized.

13. For the large thread of the three-thick-wall seamless steel pipe with a diameter of 16 or more, the spacing between the two trademarks is above IM.

14. The longitudinal bars of the fake and inferior thick-walled seamless steel pipe rebar is often wavy.

After understanding the above identification methods, I believe that in the future purchase and selection of thick-walled seamless steel pipes, the selection of thick-walled seamless steel pipes will be clear and clear.