Identification method of forged and shoddy thick - wall seamless steel pipes
Source:无缝钢管网
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Author:kanglong
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Publish time:2019-08-29
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The inferior seamless steel pipes are liable to fold. Folding is a kind of broken line line formed on the surface of thick wall seamless steel pipe, which often runs through the longitudinal direction of the product.
1. The inferior seamless steel pipes are liable to fold. Folding is a kind of broken line line formed on the surface of thick wall seamless steel pipe, which often runs through the longitudinal direction of the product. The folding is due to the counterfeiting and inferior manufacturer's pursuit of high efficiency, the amount of the pressure is too large, produce ear son, when the next rolling, will creat the folding, folding product will crack after bending, the strength of the thick wall seamless steel tube drops.
2.The appearance of the fake and inferior thick - wall seamless steel pipe often has the surface pitting phenomenon. The rough surface is due to the wear of the rolling groove caused the surface irregular defects of the thick wall seamless steel pipe. Because of poor quality and thick wall seamless steel pipe manufacturers to pursue profits, often appear rolling groove rolling excessive.
3. The surface of the fake and inferior thick - wall seamless steel pipe is liable to scab. There are two reasons: （1）. the quality of the low-quality and thick wall seamless steel pipe is not uniform, and the impurities are much. (2). The guide equipment of fake and inferior materials is simple and easy to stick steel, these impurities can easily scar after the roll.
4. The surface of fake and inferior materials is easy to crack, because its billet is the adobe, the adobe porosity is much, the adobe is in the process of cooling due to the role of thermal stress, resulting in cracks, after rolling, there is cracks.
5. The inferior seamless steel pipe is easy to scratch, the reason is that the poor equipment of the shoddy material factory, easy to produce burrs, and scratch the surface of thick wall seamless steel pipe. The strength of thick - wall seamless steel pipe is reduced by deep scratch.
6. The fake and inferior thick-walled seamless steel pipes have no metallic luster and are reddish or similar to the color of pig iron, for two reasons,its material is the adobe. 2. the temperature of the rolling of fake and inferior materials is not standard, their steel temperature is through visual, so that can not be rolled according to the required austenite region, the performance of thick wall seamless steel pipe can not reach the standard.
7. The transverse reinforcement of the inferior thick-walled seamless steel pipe is fine and low, and there is often a phenomenon of filling . the reason is that the manufacturer is to achieve a large negative tolerance, the amount of the pressure in the front of the finished product is too large, the iron type is small, and pass filling is insufficient.
8. The cross section of inferior seamless steel pipe is oval in shape, the reason is that, in order to save the material, the pressure of the second layer of the finished roller is too large, the strength of this kind of steel bar is greatly reduced, and it is not in accordance with the standard of the shape dimension of the screw steel.
9. The composition of high quality thick wall seamless steel pipe is even, the tonnage of cold shearing machine is high, the end face is smooth and neat, and because of poor material quality, the cutting head end face often has the phenomenon of Diao, that is, uneven, and no metallic luster. Moreover, because of the shoddy products, the products have little cutting head, and the head and tail will appear big ears.
10. The material of the low-quality and thick wall seamless steel pipe contains many impurities, the density of the steel is small, and the size is very poor, so it can be weighed and checked without a vernier caliper. For example, for the rebar 20, the maximum negative tolerance specified in the national standard is 5 %, the single theoretical weight of the length of 9m is 120 kg, its minimum weight should be: 120 x ( l - 5 % ) = 114 kg, and the actual weight of the single root is less than 114 kg, which is a low-quality and thick-walled seamless steel pipe because it has a tolerance of more than 5 %. In general, the effect of the overall proportionality will be better, taking into account the problem of cumulative error and probability theory.
