1) Reduce the carbon content in the steel, so that the carbon binding amount in the steel is lower than the saturated solubility of austenite in the equilibrium state, which fundamentally solves the problem of carbon steel. Chromium carbide (Cr23C6) is precipitated on the grain boundary. Typically, the carbon content in steel can be reduced to less than 0.03% to meet the requirements for intergranular corrosion resistance. Intergranular corrosion resistance: 304L > 304 > 316.
2) The
seamless tube can prevent the intergranular corrosion of
austenitic stainless steel tubes by adding Ti, Nb and other elements that can form stable carbides (TiC or NbC) to avoid the precipitation of Cr23C6 on the grain boundaries. Therefore, the resistance to grain boundary corrosion of 321 is better than that of 304.
3) By adjusting the ratio of austenite-forming elements to ferrite-forming elements in the steel, the seamless steel pipe has a dual-phase structure of austenite + ferrite, in which ferrite accounts for 5% to 12%. This two-phase structure is not prone to intergranular corrosion. This is why 2205 has better resistance to intergranular corrosion than ordinary austenitic stainless steel tubes.
4) The
seamless steel tube adopts appropriate heat treatment process to prevent intergranular corrosion and obtain the best corrosion resistance.
