In daily steel procurement, the most irritating and irritating thing is the purchase of inferior seamless steel tubes, which affects product quality. How to identify inferior seamless steel pipe? Here we identify through the following methods:
1, poor quality seamless steel pipe surface is prone to scarring.
Mainly due to two reasons:
(1) There are many impurities in the inferior seamless steel tubes and the materials are not uniform.
(2) Inadequate guide equipment for poor quality pipe manufacturers is particularly prone to sticking steel. Contaminated pipes tend to produce scars when they bite into the roll.
2, poor quality seamless steel pipe is prone to tube folding.
The so-called folding is a variety of fold lines formed on the surface of the seamless steel pipe, and this defect often runs through the entire product. The reason for the folding is that the manufacturer is pursuing high efficiency in order to increase the output. In the production process, the amount of pressing is large, and ears are produced, and folding is easily generated in the next rolling process. The folded product is easily cracked after bending, resulting in a significant decrease in the strength of the pipe.
3, poor quality seamless steel pipe is prone to scratches, due to the poor production equipment of poor quality steel pipe manufacturers, the product is prone to burrs, scratch the surface of steel, deep scratches will reduce the strength of steel.
4, poor surface quality of seamless steel pipe surface phenomenon.
5, the surface of poor quality pipe is prone to cracking. One of the reasons is that its blank is adobe, and there are many holes in the adobe. During the cooling process, cracks are generated due to thermal stress and cracks occur after rolling.
6, poor quality seamless steel tube without metallic luster, pale red or similar pig iron color, there are two reasons:
(1) Its blank is adobe.
(2) The temperature of inferior material rolling is not standard, and their steel temperature is measured visually, so that rolling cannot be carried out according to the prescribed austenitic region, and the performance of the steel material naturally cannot reach the standard.
7, poor quality seamless steel tubes with thin and low cross-bars often appear to be filled with dissatisfaction. The reason is that manufacturers have to achieve large negative tolerances. The amount of reduction in 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 composition of high-quality steel uniform, high specifications pipe cutting machine, cutting head surface smooth and neat, and poor quality material due to poor material, the end of the head often have meat off the phenomenon that is uneven, and no metallic luster. Moreover, due to the low number of products cut by poor quality manufacturers, large ears will appear at the head and tail.
9, poor quality seamless steel pipe cross-section irregularity, ovality error. The reason is that in order to increase the output of the product, the amount of reduction in the first two passes of the finished roll is large. The strength of this seamless steel tube is greatly reduced, and it does not meet the standard for the outer dimensions of seamless steel tubes.
10, poor quality seamless steel pipe material contains many impurities, the density of the steel is too small, and the size of the overrun is serious, so in the absence of vernier caliper, it can be weighed and checked. For example, for rebar 20, the national standard specifies a maximum negative tolerance of 5%. When the length is 9M, its single theoretical weight is 120 kg. Its minimum weight should be: 120 X (l-5%) = 114 kg. , Weighing out the actual weight of a single root smaller than 114 kilograms is inferior steel because its negative tolerance exceeds 5%. In general, the phasing effect will be better, mainly considering cumulative error and probability theory.
11, poor quality seamless steel pipe diameter fluctuations, due to;
(1) There is yin and yang on the unstable steel temperature.
(2) The composition of steel is not uniform.
(3) Due to poor equipment, low foundation strength, and large bouncing of the rolling mill. There will be a large change in the same week, such a seamless steel pipe is not easy to produce stress fracture.
12, the quality seamless steel pipe trademark and printing are more standardized.
13, poor quality seamless steel pipe manufacturers because there is no driving, so the package is relatively loose. The side is oval.
The pockmark is due to the irregular wear and tear of the surface of the steel due to the wear of the groove. Due to the need for low-quality steel pipe manufacturers to seek profits, rolling slot rolling is often the most excessive.
