Factors that need to be paid attention to in the online bright solution treatment processing of stainless steel pipes

When stainless steel pipes are processed by bright solution treatment, in addition to paying attention to the influence of factors such as protective atmosphere, processing temperature, and cooling rate, it is also necessary to do a good job in the process of bright solution treatment.
The first is the online bright solution treatment process. During the production process, stainless steel pipes are affected by high temperatures during rolling, stretching and welding, which will cause considerable changes in the structure and mechanical properties of the pipes. In severe cases, it will also affect When it comes to the quality of stainless steel pipes, the main change that may occur is the cold work hardening phenomenon, which refers to the regular staggered arrangement of one or several columns of atoms in the metallographic structure crystal, causing distortion of the crystal lattice and becoming a stress concentration. area, this phenomenon is also called dislocation. This is because high temperature and uneven cooling will generate welding stress and form ferrite in the original single austenite structure, resulting in uneven structures such as carbides. In order to increase processing efficiency, ensure that the surface brightness of the stainless steel pipe reaches the standard, and remove residual stress To obtain a single austenitic structure and high-quality stainless steel pipes, online bright solution treatment must be adopted.
Secondly, in terms of protective atmosphere, online bright solid solution treatment usually uses liquid ammonia decomposition gas as the protective atmosphere. Liquid ammonia will decompose into hydrogen and nitrogen above 400°C. Hydrogen is a reducing gas and can reduce certain metals and nitrogen under corresponding conditions. It is a neutral gas. Using liquid ammonia decomposition atmosphere as a protective gas can make the surface of stainless steel pipes smooth and white, so it is also a cost-effective and effective protective gas.
In addition, you need to pay attention to the solid solution treatment temperature, because it is one of the key parameters in the solid-liquid treatment process. If the temperature is too high or too low, it will directly affect the quality of the stainless steel pipe product. If the temperature is too high, the metallographic structure of the stainless steel pipe will be changed. Coarse and reduce performance. If the temperature is too low, the solid solution will be incomplete and the stress cannot be completely eliminated. Therefore, a suitable temperature and proper insulation are required to fully dissolve the carbides.
Also pay attention to the influence of cooling rate in the later stages of solution treatment. Because austenitic stainless steel will produce σ phase embrittlement in the range of 650℃-850℃, which is usually formed in the form of needle-like flakes within the austenite grain or on the grain boundary, which will greatly reduce the plasticity and toughness of the material. With strength, the range of 450℃-850℃ is also the sensitive area for intergranular corrosion of Austrian low-body stainless steel. In this temperature range, the supersaturated solid solution carbon atoms in the metal grains gradually diffuse toward the grain edges, and the edge layer Chromium atoms generate carbides and precipitate along the grain boundaries, causing the grain edges to lose corrosion resistance due to chromium deficiency. When austenitic stainless steel is heated to 1080°C ± 10°C, the carbides in the stainless steel can also be kept warm. Fully dissolved and then quickly cooled to prevent the stainless steel from staying in the 450℃-850℃ range. This not only avoids the occurrence of σ phase and intergranular corrosion, but also prevents carbides from precipitating along the austenite grain boundaries, directly obtaining the required The uniform saturated single austenite metallographic structure enables online bright solution treatment of stainless steel pipes.