In modern equipment manufacturing, due to the comprehensive considerations of cost, performance or structural design, it often involves the connection between different grades of stainless steel, and even the connection of dissimilar materials such as stainless steel and carbon steel.This kind of welding task puts forward higher requirements for the selection of welding wires than “welding of the same material”.The value of stainless steel welding wire in this field lies in its role as a “transition zone” with adjustable composition, which can coordinate the huge differences in physical and chemical properties of two different base materials through exquisite alloy design to achieve a firm and reliable connection.

When welding dissimilar stainless steel, the main challenge lies in the differences in the coefficient of thermal expansion, thermal conductivity and corrosion resistance of the two.Welding wires with alloy content between the two or inclined to the higher performance side are usually used as a compromise.For example, when connecting austenitic stainless steel and ferritic stainless steel, high-chromium-nickel austenitic welding wire is usually used to form a weld with good plastic toughness and relieve the stress concentration caused by differences in thermal expansion.The key is to enable the macroscopic properties of the weld metal to accommodate the characteristics of the base material on both sides, and to ensure its own metallurgical stability.

When welding stainless steel and carbon steel, the problem is more complicated.The core difficulty lies in how to suppress the migration of carbon from carbon steel to stainless steel welds, and how to deal with the huge metallurgical incompatible nature of the two.For this reason, high-chromium-nickel type 309 or welding wires containing stronger alloying elements are often used.The weld metal of this type of welding wire has a high degree of alloying and austenitic tissue, which can effectively “dilute” the migrated carbon and act as a buffer layer to prevent the formation of hard and brittle martensitic tissue on the carbon steel side, thereby obtaining a welded joint with acceptable strength and toughness, which plays a key role in the manufacture of composite structures.