Manufacturing process of stainless steel U-shaped tube

Stainless steel U-shaped tube is a tubular component that bends straight tube into a "U" shape. The "U"-shaped design can reduce connection points, prevent gas or liquid leakage, and absorb deformation of thermal expansion and contraction. This kind of pipe is widely used in heat exchangers, refrigeration systems, pipeline connections, instruments and other fields. The manufacturing process needs to be adjusted according to material characteristics, size specifications and performance requirements.

In the process of manufacturing stainless steel U-shaped tubes, the characteristics of the material must be fully considered and precise process technology must be used. The core steps of the entire production process include raw material processing, bending molding, post-treatment and quality inspection. These steps are all to ensure that the final product can operate stably under extreme environments such as high pressure, high temperature and strong corrosion. The following is a detailed summary of these core links.

First, in the raw material processing step, it is necessary to select suitable straight pipes according to actual working conditions. These straight pipes can be welded pipes or seamless pipes. After selection, use laser or plasma cutting technology to cut the pipe in a fixed length. After the cutting is completed, use a special cleaning agent to remove the oil stain on the surface of the pipe, and then use nitric acid-hydrofluoric acid solution for pickling to remove the oxide scale and ensure the cleanliness of the surface of the pipe.

Bending molding is the most critical step in the entire manufacturing process. For pipes with wall thickness not exceeding 8 mm and pipe diameter not exceeding 150 mm, cold bending process is usually used. The cold bending process relies on a CNC pipe bending machine and corresponding molds, and reduces friction by using extreme pressure grease, while strictly controlling the bending radius to at least 1.5 times the diameter of the pipe, and a rebound compensation of 2°-3° is preset. For pipes with larger wall thickness or larger pipe diameter, the thermal bending process is used. The thermal bending process requires local induction heating of the pipe, the heating temperature is usually between 900-1050°C (avoiding the sensitization zone), and argon is introduced during the heating process to prevent oxidation. The bending speed should be controlled at no more than 3 degrees per second, and the bending should be cooled after completion. In the manufacturing process, there are two key details that need to be noted: First, the thinner the wall thickness of the pipe, the easier it is to deflate when bending; second, heating the pipe during bending (such as using fire roasting) can effectively reduce the risk of cracking.

The post-processing process mainly focuses on improving accuracy and performance. The chamfering treatment of pipe mouth can remove burrs and improve the safety of pipe use. For pipes that have been cold-bending, solid solution treatment at 1050-1100°C is required, and intergranular corrosion is prevented by water quenching and quick cooling. Thermal bending pipes require stress annealing treatment of 800-850℃. Finally, a layer of Cr₂O₃ film was formed on the surface of the pipe by pickling passivation treatment, and its qualification was verified through blue dot test. As needed, electrolytic polishing can also be performed to make the surface roughness of the pipe reach Ra≤0.4μm.

The quality inspection link covers comprehensive inspection of size, performance and corrosion resistance. The hydraulic pressure test ensures that the pipe has no leakage at 1.5 times the working pressure, and the potential defects are checked using fluorescence penetration and ultrasonic flaw detection technology. Throughout the production process, all data will be recorded in detail to ensure product traceability. Ultimately, through these rigorous testing and processing steps, it can be ensured that the stainless steel U-shaped pipe meets the needs of use in harsh environments such as high pressure, high temperature, and strong corrosion.

To sum up, through strict control and fine operation of the above steps, stainless steel U-shaped pipes that can adapt to extreme environments such as high pressure, high temperature, and strong corrosion can be manufactured to ensure their reliability and stability in actual applications.