Welding rod consists of two parts: welding core and coating. Welding rod is to apply the coating (coating) evenly and concentrically on the welding core outside the metal welding core. Different types of welding rods have different welding cores. Welding core is the metal core of welding rod. In order to ensure the quality and performance of welding seam, the content of each metal element in welding core has strict regulations, especially for harmful impurities (such as sulfur, phosphorus, etc.) the content of, should be strictly limited, better than the base metal. The metal core covered by drug skin in the welding rod is called welding core. The welding core is generally a steel wire with a certain length and diameter. When welding, the welding core has two functions: one is conducting welding current, generating electric arc to convert electric energy into heat energy, and the other is that the welding core itself melts as the filling metal and the liquid base metal to form a weld.