The excellent properties of 347 stainless steel tubes are attributed to their precisely designed chemical composition. This material effectively addresses the problem of intergranular corrosion by adding niobium stabilizing elements to 304 stainless steel, making it stable under high-temperature and welding conditions.
According to the ASTM A312 standard, the main chemical composition range of 347 stainless steel tubes is as follows: carbon (C) ≤ 0.08%, chromium (Cr) is 17.0% - 19.0%, nickel (Ni) is 9.0% - 13.0%, niobium (Nb) is 10×C% - 1.10%, manganese (Mn) ≤ 2.00%, silicon (Si) ≤ 1.00%, phosphorus (P) ≤ 0.045%, and sulfur (S) ≤ 0.030%. Among them, chromium, nickel, and niobium are the three elements that play a decisive role in the material's performance.
The chromium (Cr) content is controlled within the range of 17.0% - 19.0%, which is a key element for forming a protective film and enhancing the material's anti-oxidation and corrosion resistance. The higher the chromium content, the more stable the protective film will be, but excessive chromium content will affect the processing performance. This range ensures a good balance between corrosion resistance and formability.
The nickel (Ni) content ranges from 9.0% to 13.0%. Its main function is to stabilize the austenite structure, enhancing the toughness and processing performance of the material. Nickel also improves the stability of the passivation film, enhances the corrosion resistance of the material in reducing media, and simultaneously reduces the tendency of cold work hardening.
Niobium (Nb) is the characteristic element of 347 stainless steel tubes. The required content is more than 10 times that of carbon content and does not exceed 1.10%. Niobium combines with carbon preferentially to form carbides of niobium, effectively inhibiting the precipitation of chromium carbides at grain boundaries, thereby endowing the material with excellent intergranular corrosion resistance. This characteristic enables 347 stainless steel tubes to maintain good corrosion resistance even after welding or during service at sensitization temperatures ranging from 450°C to 850°C.
Jiangsu Cunrui Metal Products Co., Ltd. The 347 stainless steel pipes supplied all come with the original factory warranty certificate. Their chemical composition and mechanical properties can be traced, ensuring that the products meet the requirements of ASTM, ASME and GB standards.
If you need any assistance, please feel free to contact our company at any time. We will provide you with professional products and services.