1. Fake and inferior thick-walled
steel pipes are prone to folding. Folding is a variety of fold lines formed on the surface of thick-walled steel pipes, and this defect often runs through the longitudinal direction of the entire product. The folding is because the fake and inferior manufacturers pursue high efficiency, the reduction is too large, and ears are formed. Folding will occur in the next rolling process. The folded product will crack after bending, and the strength of the steel will drop greatly.
2. The appearance of fake and inferior thick-walled steel pipes often has pockmarks. A pockmarked surface is a defect of irregular unevenness on the surface of the steel due to severe wear of the rolling groove. Because manufacturers of fake and inferior thick-walled steel pipes want to pursue profits, groove rolling often exceeds the standard.
3. The surface of fake and inferior thick-walled steel pipes is prone to scarring. There are two reasons: (1). The material of fake and inferior steel pipes is uneven and has many impurities. (2). The guides and guards of fake and inferior material manufacturers are poorly equipped and easy to stick to steel. These impurities are prone to scarring after biting the roll.
4. The surface of fake and inferior materials is prone to cracks. The reason is that its billet is adobe, and the adobe has many pores. During the cooling process, the adobe is subjected to thermal stress, causing cracks, and there are cracks after rolling.
5. Fake and inferior thick-walled steel pipes are easy to scratch. The reason is that the manufacturers of fake and low thick-walled steel pipes have poor equipment, which is easy to produce burrs and scratch the surface of the steel. Deep scratches reduce the strength of the steel.
6. False and inferior thick-walled steel pipes have no metallic luster and are light red or similar in color to pig iron. There are two reasons for this. Second, its blank is adobe. 2. The rolling temperature of fake and inferior materials is not standard. Their steel temperature is measured visually, so it cannot be rolled according to the specified austenite area, and the performance of the steel will naturally fail to meet the standard.
7. The horizontal ribs of fake and inferior thick-walled steel pipes are thin and low, and often appear to be full and dissatisfied. The reason is that to achieve a large negative tolerance, the reduction in the first few passes of the finished product is too large, the iron shape is too small, and the pass is not full.
8. The cross-section of fake and inferior thick-walled steel pipes is elliptical. The reason is that to save materials, the reduction in the first two passes of the finished roll is too large. standard.
9. The composition of the steel is uniform, the tonnage of the cold shear is high, and the end face of the cutting head is smooth and neat. However, due to the poor quality of the fake and inferior materials, the end face of the cutting head often has the phenomenon of meat loss, that is, unevenness and no metallic luster. Moreover, because the products of fake and inferior material manufacturers have fewer heads, oversized ears will appear at the head and tail.
10. The material of fake and inferior thick-walled steel pipes contains many impurities, the density of the steel is relatively 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 standard stipulates that the maximum negative tolerance is 5%, and its single theoretical weight is 120 kg when the length is 9M, and its minimum weight should be: 120X (l-5%) = 114 kg, which is called If the actual weight of a single piece measured is less than 114 kg, it is a fake and inferior steel 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 fake and inferior thick-walled steel pipes fluctuates greatly because of:
①. The steel temperature is unstable and has negative and positive sides. ②, the composition of steel is not uniform. ③. Due to poor equipment and low foundation strength, the rolling mill has a large bounce. There will be a large change in the inner diameter within the same week, and such steel bars are prone to fracture due to uneven stress.
12. The trademark and printing of the steel pipe are more standardized.
13. For large threads with a steel pipe diameter of 16 or more, the distance between the two trademarks is above IM.
14. The longitudinal bars of false and inferior steel rebar is often wavy.
15. Manufacturers of fake and inferior thick-walled steel pipes are loosely packaged because they do not have driving vehicles. The sides are oval.
