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Identification Methods of Seamless Pipes and Welded Pipes
Jun 29, 2022
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There are two types of common steel pipes. They are mainly the welded steel pipe and the seamless steel pipe. In the process of engineering construction, it will be combined with the specific construction situation to choose the appropriate steel pipe, and the cost will be the primary factor. Therefore, this article is going to discuss the performance, technology and identification methods of the seamless pipe and the welded pipe distinguish them. We hope to provide reference for the selection of steel pipes in the process of engineering construction.
With the continuous progress of science and technology, the production process of steel pipes in China has also improved significantly. At present, the common steel pipes mainly have two types, which are welded steel pipes and seamless steel pipes. Because the cost of welded steel pipes is significantly lower than that of seamless steel pipes, some businesses' process of welded steel pipes pretend to be that of seamless steel pipes in order to seek more economic benefits, and then they will be sold into the market, causing confusion in the market. From the appearance of the processing of welded steel pipes, it can not be effectively identified. Once in the process of engineering construction, we should use seamless steel pipes instead of welded steel pipes. It will lead to gas or liquid leakage. Seriously, it is easy to cause an explosion. Therefore, it is necessary to identify welded steel pipes and seamless steel pipes so as to ensure the quality of the project.
A welded steel pipe is generally a steel strip or steel plate under the action of external force, making it into a round or square pipe, and then welding the surface joints. Therefore, a welded steel pipe is produced. The commonly used processes are arc welding, high or low frequency, cold rolling and so on. However, the use of these processes for welding will lead to welded steel pipes. At present, according to the shape of welding seam, it can be divided into straight seam and spiral welded steel pipes, but they use different technology. The spiral steel pipe is welded by submerged arc welding, which has the advantages of high welding efficiency and less dust. For high frequency or low frequency welding, it is mainly based on the principle of electromagnetic induction. Due to the AC charge in the conductor, it will occur adjacent and turbine heat effect, which can achieve the welding edge of steel to melt state, and the final welding is completed.
The seamless steel pipe is mainly a solid pipe billet or steel ingot for perforation. It is made of wool pipes, and through hot rolling, cold rolling, cold drawing and other processing, it is formed into a seamless steel pipe. Since seamless steel pipes contain a members section, this hollow section can be used as a conduit for transporting fluids.
There are three main ways to identify welded steel pipes and seamless steel pipes.
1. The metallography method
The metallography method is one of the main methods to distinguish welded steel pipes from seamless steel pipes. There is no welding material added to the high frequency resistance welded steel pipe, so the welded steel pipe is very narrow, and the weld cannot be clearly seen if the method of rough grinding and re-corrosion is adopted. Once the high frequency resistance welded steel pipe is welded without heat treatment, the weld microstructure will be substantially different from the steel pipe base material. In this case, the metalwork method can be used to distinguish welded steel pipes from seamless steel pipes. On the steel pipe in the process of identifying, it needs to take the length and width of the welds, which are 40 mm. When it carries on the coarse grinding, fine grinding and polishing processing, and then it is put in metallographic microscope. When observed ferrite and westergren, mother material and weld area organization, we can accurately identify the welded steel pipe and the seamless steel pipe.
2. The corrosion method
In using corrosion method to identify in the process of the welded steel pipe and the seamless steel pipe, it should be in the processing of welds of welded steel pipes in grinding processing. After completion of polishing of the steel pipe, we should be able to see the trace of grinding, and then in the weld with the end face of sand paper burnish. If there is an obvious weld, it is proved that this steel pipe is the welded steel pipe. However, the end face of seamless steel pipes has no obvious difference after corrosion.
The performance of a welded steel pipe
The welded steel pipe is processed by high frequency welding and cold rolling, so it has the following properties. First, the insulation function is good. The heat loss degree of welded steel pipe is relatively small, only 25%, which is not only conducive to transportation, but also reduces the cost. Second, it has water resistance and corrosion resistance. In the process of engineering construction, there is no need to set up a separate pipe trench. Just the steel pipe directly buried underground or underwater, so as to reduce the construction difficulty of the project. Third, it has impact resistance. The steel pipe is not damaged even at low temperature, so its performance has certain advantages.
The performance of a seamless steel pipe
Due to the large tensile strength of the metal material of seamless steel pipes, its damage resistance is stronger, and it has a hollow channel, so it can effectively transport fluid. It is its strong conveying capacity, so the corrosion resistance of seamless steel pipes is higher than that of welded steel pipes, and its stiffness is relatively large. Therefore, the more load of seamless steel pipes, the wider applications used in high construction requirements of the project.
3. Identify welded steel pipes and seamless steel pipes according to the process
In the process of identifying welded steel pipes and seamless steel pipes, welded steel pipes are welded according to cold rolling, extrusion and other processes. In addition, spiral pipes welding and straight seam pipes welding will be formed when welding steel pipes using high frequency and low frequency arc welding pipe and resistance welding pipe technology. There will be round, square, oval, triangular, hexagonal, diamond, octagonal and even more complex steel pipes. In conclusion, different processes will form different shapes of steel pipes, so that welded steel pipes and seamless steel pipes can be clearly distinguished. However, according to the process of the identification of seamless steel pipes, there are two types of seamless steel pipe mainly. Respectively, it is hot rolled seamless steel pipes and cold rolled seamless steel pipes. The hot rolled seamless steel pipe is formed by the perforation, rolling and other processes. The large diameter and thickness of seamless steel pipes are welded by this process. The cold-drawn pipe is formed by a cold-drawn pipe billet, the strength of the material is lower, but its appearance and internal control surface are smooth.
4. Identify welded steel pipes and seamless steel pipes according to their applications
The welded steel pipe has higher bending and torsional strength and more bearing capacity, so it is widely used in the manufacture of mechanical parts. For example, oil drill pipes, car drive shafts, bicycle frames and steel scaffolding used in construction are all made of welded steel pipes. However, the seamless steel pipe can be used as a pipeline for conveying fluid because of its hollow section and the absence of long steel joints around it. For example, it can be used as a pipeline to transport oil, natural gas, gas, water and so on. In addition, the flexural strength of seamless steel pipes is relatively small, so it is widely used in low and medium pressure boiler superheated steam pipes, boiling water pipes and locomotive boiler superheated steam pipes. In conclusion, through the classification of applications, welded steel pipes and seamless steel pipes can be clearly distinguished.
In order to ensure higher quality of engineering construction in our country, it is necessary to distinguish welded steel pipes from seamless steel pipes, and then use appropriate steel pipes for construction. In the process of identifying welded steel pipes and seamless steel pipes. You can use the metallographic method and corrosion method, by observing the structure and weld, so as to test the weld, and finally to accurately identify it. At the same time, the two kinds of steel pipes can be distinguished according to their performance, applications and so on. You could choose a reasonable steel pipe for construction.
With the continuous progress of science and technology, the production process of steel pipes in China has also improved significantly. At present, the common steel pipes mainly have two types, which are welded steel pipes and seamless steel pipes. Because the cost of welded steel pipes is significantly lower than that of seamless steel pipes, some businesses' process of welded steel pipes pretend to be that of seamless steel pipes in order to seek more economic benefits, and then they will be sold into the market, causing confusion in the market. From the appearance of the processing of welded steel pipes, it can not be effectively identified. Once in the process of engineering construction, we should use seamless steel pipes instead of welded steel pipes. It will lead to gas or liquid leakage. Seriously, it is easy to cause an explosion. Therefore, it is necessary to identify welded steel pipes and seamless steel pipes so as to ensure the quality of the project.
A welded steel pipe is generally a steel strip or steel plate under the action of external force, making it into a round or square pipe, and then welding the surface joints. Therefore, a welded steel pipe is produced. The commonly used processes are arc welding, high or low frequency, cold rolling and so on. However, the use of these processes for welding will lead to welded steel pipes. At present, according to the shape of welding seam, it can be divided into straight seam and spiral welded steel pipes, but they use different technology. The spiral steel pipe is welded by submerged arc welding, which has the advantages of high welding efficiency and less dust. For high frequency or low frequency welding, it is mainly based on the principle of electromagnetic induction. Due to the AC charge in the conductor, it will occur adjacent and turbine heat effect, which can achieve the welding edge of steel to melt state, and the final welding is completed.
The seamless steel pipe is mainly a solid pipe billet or steel ingot for perforation. It is made of wool pipes, and through hot rolling, cold rolling, cold drawing and other processing, it is formed into a seamless steel pipe. Since seamless steel pipes contain a members section, this hollow section can be used as a conduit for transporting fluids.
There are three main ways to identify welded steel pipes and seamless steel pipes.
1. The metallography method
The metallography method is one of the main methods to distinguish welded steel pipes from seamless steel pipes. There is no welding material added to the high frequency resistance welded steel pipe, so the welded steel pipe is very narrow, and the weld cannot be clearly seen if the method of rough grinding and re-corrosion is adopted. Once the high frequency resistance welded steel pipe is welded without heat treatment, the weld microstructure will be substantially different from the steel pipe base material. In this case, the metalwork method can be used to distinguish welded steel pipes from seamless steel pipes. On the steel pipe in the process of identifying, it needs to take the length and width of the welds, which are 40 mm. When it carries on the coarse grinding, fine grinding and polishing processing, and then it is put in metallographic microscope. When observed ferrite and westergren, mother material and weld area organization, we can accurately identify the welded steel pipe and the seamless steel pipe.
2. The corrosion method
In using corrosion method to identify in the process of the welded steel pipe and the seamless steel pipe, it should be in the processing of welds of welded steel pipes in grinding processing. After completion of polishing of the steel pipe, we should be able to see the trace of grinding, and then in the weld with the end face of sand paper burnish. If there is an obvious weld, it is proved that this steel pipe is the welded steel pipe. However, the end face of seamless steel pipes has no obvious difference after corrosion.
The performance of a welded steel pipe
The welded steel pipe is processed by high frequency welding and cold rolling, so it has the following properties. First, the insulation function is good. The heat loss degree of welded steel pipe is relatively small, only 25%, which is not only conducive to transportation, but also reduces the cost. Second, it has water resistance and corrosion resistance. In the process of engineering construction, there is no need to set up a separate pipe trench. Just the steel pipe directly buried underground or underwater, so as to reduce the construction difficulty of the project. Third, it has impact resistance. The steel pipe is not damaged even at low temperature, so its performance has certain advantages.
The performance of a seamless steel pipe
Due to the large tensile strength of the metal material of seamless steel pipes, its damage resistance is stronger, and it has a hollow channel, so it can effectively transport fluid. It is its strong conveying capacity, so the corrosion resistance of seamless steel pipes is higher than that of welded steel pipes, and its stiffness is relatively large. Therefore, the more load of seamless steel pipes, the wider applications used in high construction requirements of the project.
3. Identify welded steel pipes and seamless steel pipes according to the process
In the process of identifying welded steel pipes and seamless steel pipes, welded steel pipes are welded according to cold rolling, extrusion and other processes. In addition, spiral pipes welding and straight seam pipes welding will be formed when welding steel pipes using high frequency and low frequency arc welding pipe and resistance welding pipe technology. There will be round, square, oval, triangular, hexagonal, diamond, octagonal and even more complex steel pipes. In conclusion, different processes will form different shapes of steel pipes, so that welded steel pipes and seamless steel pipes can be clearly distinguished. However, according to the process of the identification of seamless steel pipes, there are two types of seamless steel pipe mainly. Respectively, it is hot rolled seamless steel pipes and cold rolled seamless steel pipes. The hot rolled seamless steel pipe is formed by the perforation, rolling and other processes. The large diameter and thickness of seamless steel pipes are welded by this process. The cold-drawn pipe is formed by a cold-drawn pipe billet, the strength of the material is lower, but its appearance and internal control surface are smooth.
4. Identify welded steel pipes and seamless steel pipes according to their applications
The welded steel pipe has higher bending and torsional strength and more bearing capacity, so it is widely used in the manufacture of mechanical parts. For example, oil drill pipes, car drive shafts, bicycle frames and steel scaffolding used in construction are all made of welded steel pipes. However, the seamless steel pipe can be used as a pipeline for conveying fluid because of its hollow section and the absence of long steel joints around it. For example, it can be used as a pipeline to transport oil, natural gas, gas, water and so on. In addition, the flexural strength of seamless steel pipes is relatively small, so it is widely used in low and medium pressure boiler superheated steam pipes, boiling water pipes and locomotive boiler superheated steam pipes. In conclusion, through the classification of applications, welded steel pipes and seamless steel pipes can be clearly distinguished.
In order to ensure higher quality of engineering construction in our country, it is necessary to distinguish welded steel pipes from seamless steel pipes, and then use appropriate steel pipes for construction. In the process of identifying welded steel pipes and seamless steel pipes. You can use the metallographic method and corrosion method, by observing the structure and weld, so as to test the weld, and finally to accurately identify it. At the same time, the two kinds of steel pipes can be distinguished according to their performance, applications and so on. You could choose a reasonable steel pipe for construction.
