2. Fake thick-walled seamless steel pipes often have pitting on the surface. The pitted surface is a defect that the surface of thick-walled seamless steel pipe is irregular and uneven due to severe wear of the rolling groove. As manufacturers of counterfeit and inferior thick-walled seamless steel pipes are pursuing profits, the groove rolling often exceeds the standard.
3. The surface of fake thick-walled seamless steel pipe is prone to scarring. There are two reasons: a. Fake thick-walled seamless steel pipes have uneven materials and many impurities. b. The guide and guard equipment of the fake and inferior material manufacturers is simple and easy to stick to the steel. These impurities will easily cause scars after biting the roll.
4. The surface of fake and inferior materials is prone to cracks, because its billet is adobe, which has many pores. The adobe is subjected to thermal stress during the cooling process, resulting in cracks, and there will be cracks after rolling.
5. Fake and inferior thick-walled seamless steel pipes are easy to scratch. The reason is that the equipment of manufacturers of fake and inferior materials is simple and 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. Fake thick-walled seamless steel pipes have no metallic luster, and are pale red or pig-iron-like colors. There are two reasons for this. Its blank is adobe. 2. The rolling temperature of fake and inferior materials is not standard, and their steel temperature is visually inspected, so that it cannot be rolled in the specified austenite area, and the performance of thick-walled seamless steel pipes will naturally not reach the standard.
7. The cross ribs of fake thick-walled seamless steel pipes are thin and low, and the phenomenon of dissatisfaction often occurs. The reason is that in order 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 cross-section of the fake thick-walled seamless steel pipe is elliptical. The reason is that in order to save materials, the reduction of the first two passes of the finished roll is too large. The strength of this kind of rebar is greatly reduced, and it does not conform to the shape of the rebar. Standards.
9. The composition of high-quality thick-walled seamless steel pipes is uniform, the tonnage of the cold shear is high, and the end face of the cutting head is smooth and tidy. However, due to the poor material of the fake material, the end face of the cutting head often has the phenomenon of meat loss, that is, uneven, and no metallic luster . Moreover, because the products of the counterfeit and inferior material manufacturers have fewer cuts, big ears will appear at the ends.
10. The fake thick-walled seamless steel pipe material contains many impurities, the density of the 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: 120X (l-5%) = 114 kg, The actual weight of a single piece weighed out is less than 114 kg, it is a fake thick-walled seamless steel pipe, 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 the fake thick-walled seamless steel pipe fluctuates greatly, the reason is: l, the steel temperature is unstable and there are positive and negative 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 of the same week, and the uneven force of such steel bars is prone to fracture.
12. The trademarks and printing of high-quality materials are relatively standardized.
13. For thick-walled seamless steel pipes with large threads with a diameter of 16 or more, the distance between the two trademarks is more than 1m.
14. The longitudinal ribs of fake thick-walled seamless steel pipe rebar are often wavy.