At metal welding sites, the welding electrode is like a magical "metal match" that can fuse two pieces of steel with a light touch. This seemingly simple metal rod is a sophisticated combination of a core wire and a coating, which work together to complete the welding task.
The core wire is the "metal skeleton" of the welding electrode, usually a specially made metal wire with a diameter of 2-6 millimeters. Its primary task is to serve as a filler material. When melted under the high temperature of the electric arc, it fuses with the metal being welded to form a strong weld. At the same time, it is also the "conductor" of electric current. When current passes through the core wire, a high-temperature electric arc is generated, providing energy for welding. The material of the core wire determines the properties of the weld: the core wire of low-carbon steel electrodes has a carbon content of no more than 0.2% to avoid weld embrittlement; the core wire of stainless steel electrodes, on the other hand, contains elements such as chromium and nickel to ensure the weld is corrosion-resistant.
The coating wrapped around the core wire is a "protective coat" made of a mixture of minerals, ferroalloys, and organic substances. Its functions are comparable to those of an "all-round housekeeper": the gas generated during combustion acts like a "protective shield" to isolate the air, preventing oxygen and nitrogen from invading the high-temperature molten pool and causing pores in the weld; the slag formed after melting is like a "thermal blanket" covering the surface of the weld, slowing down the cooling rate and preventing secondary pollution.
Components such as ferromanganese and ferrosilicon in the coating are "purifiers" that can remove harmful elements such as oxygen and sulfur from the molten pool, while alloying elements such as chromium and molybdenum are "strengtheners" that impart special properties to the weld. In addition, elements such as potassium and sodium in the coating can stabilize the electric arc, making the welding process more stable, and can be called the "sedative" of the welding electrode.
The tacit cooperation of those two parts allows cold metals to be perfectly joined, making them indispensable contributors in the manufacturing industry.