Welded steel pipes are generally formed by deforming steel strips or steel plates into round or square shapes under the action of external force, and then welding the seams on the surface to form welded steel pipes.
The seamless pipe is mainly to perforate the solid tube billet or steel ingot to make a capillary pipe, and then process it through hot rolling, cold rolling, cold drawing, etc., and then form a seamless steel pipe. Since the seamless steel pipe contains a hollow section, this hollow section can be used as a pipe for conveying fluid.
There are three main ways to identify welded steel pipes and seamless steel pipes:
1. Metallographic method
Metallographic method is one of the main methods to distinguish welded steel pipes and seamless steel pipes. High-frequency electric resistance welded steel pipe (ERW pipe) does not add welding materials, so the weld seam in the welded steel pipe is very narrow, and the weld seam cannot be clearly seen if the method of rough grinding and corrosion is used. Once the high-frequency resistance welded steel pipe is welded without heat treatment, the weld structure will be essentially different from the steel pipe parent material. At this time, the metallographic method can be used to distinguish the welded steel pipe from the seamless steel pipe. In the process of identifying the two steel pipes, it is necessary to cut a small sample with a length and a width of 40 mm at the welding point, and perform rough grinding, fine grinding and polishing on it. Then put it under a metallographic microscope to observe the structure. When ferrite and widmanstrite, the base metal and the structure of the weld zone are observed, the welded steel pipe and the seamless steel pipe can be accurately distinguished.
2. Corrosion method
In the process of using the corrosion method to identify welded steel pipes and seamless steel pipes, grinding treatment should be carried out at the weld seam of the processed welded steel pipes. After the grinding is completed, you should be able to see the traces of grinding, and then use sandpaper to polish the end face at the weld, and treat the end face with 5% nitric acid alcohol solution. If there is an obvious weld, it can prove that the steel pipe is a welded steel pipe. However, the end face of the seamless steel pipe has no obvious difference after being corroded.
3. Distinguish welded steel pipes and seamless steel pipes according to the process
When the steel pipe is welded by high-frequency, low-frequency arc welded pipe and electric resistance welded pipe process, spiral pipe welding and straight seam pipe welding will be formed. In short, different processes will form steel pipes of different shapes, so that welded steel pipes and seamless steel pipes can be clearly distinguished.
In order to ensure a higher quality of engineering construction, it is necessary to distinguish welded steel pipes and seamless steel pipes, and then use suitable steel pipes for construction. In the process of distinguishing welded steel pipes and seamless steel pipes, metallographic and corrosion methods can be used to inspect the welds by observing the structure and welds, and finally accurately identify them. At the same time, the two types of steel pipes can also be distinguished according to their properties and uses, and then a reasonable steel pipe can be selected for construction.
The seamless pipe is mainly to perforate the solid tube billet or steel ingot to make a capillary pipe, and then process it through hot rolling, cold rolling, cold drawing, etc., and then form a seamless steel pipe. Since the seamless steel pipe contains a hollow section, this hollow section can be used as a pipe for conveying fluid.
There are three main ways to identify welded steel pipes and seamless steel pipes:
1. Metallographic method
Metallographic method is one of the main methods to distinguish welded steel pipes and seamless steel pipes. High-frequency electric resistance welded steel pipe (ERW pipe) does not add welding materials, so the weld seam in the welded steel pipe is very narrow, and the weld seam cannot be clearly seen if the method of rough grinding and corrosion is used. Once the high-frequency resistance welded steel pipe is welded without heat treatment, the weld structure will be essentially different from the steel pipe parent material. At this time, the metallographic method can be used to distinguish the welded steel pipe from the seamless steel pipe. In the process of identifying the two steel pipes, it is necessary to cut a small sample with a length and a width of 40 mm at the welding point, and perform rough grinding, fine grinding and polishing on it. Then put it under a metallographic microscope to observe the structure. When ferrite and widmanstrite, the base metal and the structure of the weld zone are observed, the welded steel pipe and the seamless steel pipe can be accurately distinguished.
2. Corrosion method
In the process of using the corrosion method to identify welded steel pipes and seamless steel pipes, grinding treatment should be carried out at the weld seam of the processed welded steel pipes. After the grinding is completed, you should be able to see the traces of grinding, and then use sandpaper to polish the end face at the weld, and treat the end face with 5% nitric acid alcohol solution. If there is an obvious weld, it can prove that the steel pipe is a welded steel pipe. However, the end face of the seamless steel pipe has no obvious difference after being corroded.
3. Distinguish welded steel pipes and seamless steel pipes according to the process
When the steel pipe is welded by high-frequency, low-frequency arc welded pipe and electric resistance welded pipe process, spiral pipe welding and straight seam pipe welding will be formed. In short, different processes will form steel pipes of different shapes, so that welded steel pipes and seamless steel pipes can be clearly distinguished.
In order to ensure a higher quality of engineering construction, it is necessary to distinguish welded steel pipes and seamless steel pipes, and then use suitable steel pipes for construction. In the process of distinguishing welded steel pipes and seamless steel pipes, metallographic and corrosion methods can be used to inspect the welds by observing the structure and welds, and finally accurately identify them. At the same time, the two types of steel pipes can also be distinguished according to their properties and uses, and then a reasonable steel pipe can be selected for construction.
