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This post was last edited by Black gold on 11/8/2011 at 11:26. 1. Composition and function of welding electrodes: Welding electrodes used for shielded metal arc welding, which are coated with flux, consist of two parts: the core and the flux coating. The welding core is a metal wire with a certain diameter and length. The role of the welding core during welding ； First, it acts as an electrode to generate an arc ； Second, after melting, it serves as a filler metal, forming a weld together with the melted base material. The chemical composition of the welding core directly affects the quality of the weld, which is why it is specially produced by steel mills. The core grades of the welding electrodes made of carbon structural steel that are commonly used in our country are H08 and H08A, with an average carbon content of 0.08% (the letter A indicates high quality). The diameter of the welding rod is indicated by the diameter of its core; common diameters range from 3.2 to 6 mm, while the length is between 350 and 450 mm. The flux applied to the outside of the welding core is made by mixing various minerals (such as marble, fluorite, etc.), ferroalloys, and binders in specific proportions. The main function of the flux is to facilitate the initiation of the arc and stabilize its combustion ； A large amount of gas and slag is generated to protect the molten metal in the pool from oxidation ； Harmful impurities (such as oxygen, hydrogen, sulfur, phosphorus, etc.) are removed through metallurgical reactions in the molten pool, and alloying elements are added to improve the mechanical properties of the weld. 2. Types and grades of welding electrodes Welding electrodes can be classified into structural steel welding electrodes, heat-resistant steel welding electrodes, stainless steel welding electrodes, cast iron welding electrodes, copper and copper alloy welding electrodes, aluminum and aluminum alloy welding electrodes, etc., depending on their intended use. Based on the chemical properties of the slag, welding electrodes can be divided into two main categories: acidizing welding electrodes and basicizing welding electrodes. Welds produced with alkaline electrodes contain low levels of hydrogen, sulfur, and phosphorus. The weld has good mechanical properties, but it is sensitive to oil, water, and rust, and is prone to porosity. When welding with acidic electrodes, the arc is stable, spatter is minimal, and slag removal is effective. Therefore, alkaline electrodes are used for important welded structural components, while acidic electrodes are used for ordinary structural components. The designation method for structural steel welding electrodes is as follows: it consists of the initial letters of the pinyin of the Chinese characters followed by three digits. For example, the grade of the structural steel welding electrode used in our practice is J422 (or Knot 422 ).