347 has the same general corrosion resistance as 304. 347 in the water environment and other low temperature environment, better corrosion resistance. 347 is mainly used for high temperature applications, high temperature applications require strong resistance to the material to prevent intergranular corrosion at lower temperatures.
347 stainless steel seamless pipe corrosion resistance and resistance to intergranular corrosion is better than 304 and 321.
347 Austenitic stainless steel is sensitive to stress corrosion in halide, similar to alloy 304 stainless steel. The result will be due to their similar nickel content. The conditions that lead to stress corrosion cracking are: (1) exposure to halide ions (usually chloride), (2) residual tensile stress, (3) ambient temperature exceeding 49 ° C. The thermal cycling in the forming operation or the thermal cycle encountered in the welding operation may cause stress. The stress relief heat treatment after annealing or cold deformation may reduce the stress level. 347 is suitable for use in the elimination of stress, may be unstable stainless steel to produce intergranular corrosion of the operating environment.
347 stainless steel seamless pipe corrosion resistance
347 (0Cr18Ni11Nb) stainless steel seamless pipe is particularly useful in environments where unstable austenitic stainless steel produces polyacetic acid stress corrosion. Unstable austenitic stainless steels are exposed to the temperature at which sensitization will occur and a chromium carbide precipitate at the grain boundaries. When cooled to room temperature in a sulfur-containing environment, the sulfide (usually hydrogenated sulfur) reacts with water vapor and oxygen to form a polysulfonic acid that erodes the sensitized grain boundary. In the presence of stress, intergranular corrosion conditions, even the polysulfate stress corrosion cracking occurs in the vulcanization of the widespread oil refining environment. 347 due to the temperature rise in the operating environment with anti-sensitization and solve the problem of polysulfate stress corrosion. If the conditions of the operating environment will cause sensitization, in order to achieve the best resistance to these alloys, should be used under heat stability conditions.
Point corrosion / crevice corrosion
347 (0Cr18Ni11Nb) stainless steel seamless pipe in the presence of chloride ions in the pitting resistance and resistance to porosity and alloy 304 or 304L stainless steel almost. It is not recommended to expose it to the marine environment.
Austenitic stainless steel is considered to be the most easily welded alloy steel, can be welded with all the fusion, but also resistance welding. Production of austenitic stainless steel welding contacts to consider two factors: 1) to maintain its corrosion resistance, 2) to avoid cracking. Welding must be careful to maintain the stability of 347 elements.