The electrode is composed of two parts, the welding core and the medicine skin. The electrode is in the metal welding core outside the coating (medicine skin) evenly, to the heart pressure on the solder core. Different types of electrodes, welding cores are also different. Welding core is the metal core of the electrode, in order to ensure the quality and performance of the weld, the content of the metal elements in the welding core has strict provisions, especially on harmful impurities (such as sulphur, phosphorus, etc.) content, should be strictly limited, superior to the base material. Welding core components directly affect the composition and properties of weld metal, so the harmful elements in the welding core should be as few as possible.