How to distinguish between welded steel pipe and seamless carbon steel pipe?

There are three main ways to distinguish welded steel pipes and Seamless carbon steel pipe:

Identification method one: 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 pipes do not add welding materials, so the welds in the welded steel pipes are very narrow. If the method of rough grinding and re-corrosion is used, the welds will be indistinguishable. Once the high-frequency electric resistance welded steel pipe is welded without heat treatment, its weld structure will be essentially different from the base material of the steel pipe. At this time, the metallographic method can be used to distinguish welded steel pipes and seamless steel pipes. In the process of distinguishing the two types of steel pipes, it is necessary to cut a sample with a length and width of 40mm at the welding location, rough grinding, fine grinding, and polishing, and then observe the structure under a metallurgical microscope. When observing the structure of ferrite and Wimanstat, it is possible to accurately distinguish the base metal and weld zone, welded steel pipe and seamless steel pipe.

Identification method 2: Corrosion method

In the process of distinguishing welded steel pipes and seamless steel pipes by the corrosion method, the welds of the welded steel pipes should be polished. After polishing, you should be able to see the traces of polishing, and then polish the weld end surface with sandpaper. The end face is treated with 0.05 nitric acid alcohol solution. If there is an obvious weld, it can be proved that the steel pipe is a welded steel pipe. There is no obvious difference in the end face of the seamless steel pipe after corrosion.

Identification method 3: Identify welded steel pipes and seamless steel pipes according to the process

In the process of distinguishing welded steel pipes and seamless steel pipes by process, welded steel pipes are welded according to processes such as cold rolling and extrusion. In addition, when steel pipes are welded by high-frequency and low-frequency arc welded pipes and electric resistance welded pipes, the formation of spiral pipe welding and longitudinal pipe welding will form round steel pipes, square steel pipes, oval steel pipes, triangular steel pipes, hexagonal steel pipes, diamond steel pipes, and octagonal steel pipes. , And even more complex steel pipes. In short, the use of different processes will form steel pipes of different shapes, so that welded steel pipes and seamless steel pipes can be clearly distinguished. However, in the process of identifying seamless steel pipes according to the process, hot-rolled and cold-rolled processing methods are mainly distinguished. Seamless steel pipes also have two main forms, namely, hot-rolled seamless steel pipes and hot-rolled seamless steel pipes. Cold rolled seamless steel tube. Stitch the steel pipe. Hot-rolled seamless steel pipes are formed by punching, rolling and other processes, especially large-diameter, thick-walled seamless steel pipes are welded by this process; cold-drawn pipes are formed by cold-drawn pipe blanks, with low material strength, but their appearance And the inner control surface is smooth.