Will intergranular corrosion occur over time in the heat exchange tubes of stainless steel heat exchangers that are joined by expansion welding?

Intergranular corrosion refers primarily to the phenomenon in which stainless steel undergoes corrosion preferentially at the grain boundaries under certain specific conditions. This situation often occurs in environments containing certain corrosive agents, and is particularly common under high-temperature conditions. In the case of combining expansion welding and welding, tube-to-plate connection is typically achieved by combining mechanical methods (expansion joining) with welding methods (welding). This method can effectively improve the sealing performance and strength of the joint. In actual use, if the welding process is not properly controlled—for instance, if inappropriate welding materials or parameters are selected—the welded area may suffer from intergranular corrosion due to heat effects. For example, in environments with high temperatures, high pressures, or corrosive chemicals, certain components of stainless steel may experience segregation, accelerating the occurrence of intergranular corrosion. Expansion bonding is a purely mechanical connection method that involves no thermal effects; therefore, it theoretically does not cause intergranular corrosion. However, the sealing performance and long-term stability of expansion jointing may be inferior to that of welding, especially in applications subjected to frequent thermal cycles and pressure changes. Therefore, selecting the appropriate connection method requires taking into account the specific conditions of the surrounding environment (such as temperature, pressure, medium, etc.), as well as making a reasonable judgment based on the material of the stainless steel and its intended service life. In harsh environments, more advanced anti-corrosion treatments may be necessary, or materials with greater corrosion resistance should be chosen. At the same time, ensuring the accurate execution of the welding process by selecting appropriate welding materials and shielding gases can effectively reduce the risk of intergranular corrosion. .