A welding rod is a melting electrode used for arc welding of covered electrodes. It consists of two parts: the coating and the core. The metal core covered by the coating is called the welding core. The core is usually a steel wire with a certain length and diameter. The welding core has two functions. First, conduction of welding current generates arc to transform electric energy into heat energy. Two. The welding core itself melts as a filler metal and melts the liquid base metal to form a weld. When the electrode is welded, the core metal takes up part of the whole weld metal. Therefore, the chemical composition of the core directly affects the quality of the weld. Therefore, the steel wire used as the welding rod of the welding rod separately stipulates its brand and composition. If the welding method is used for filler metal such as submerged arc welding, electroslag welding, gas shielded arc welding and gas welding, it is called welding wire. The electrode coating refers to the coating layer applied on the surface of the welding core. The skin is decomposed and melted in welding process to form gas and slag. It plays the role of mechanical protection, metallurgical treatment and improvement of process performance. The composition of welding coating : mineral (such as marble, fluorite, etc.), iron alloy and metal powder (such as ferromanganese, ferro titanium, etc.), organic compounds (such as wood flour, starch, etc.), chemical products (such as titanium dioxide, water glass, etc.). The electrode coating flux is an important factor determining the quality of weld.