Electrode (covered electrode) 1. Requirements of the welding rod (1) easy arc starting, stable arc, little spatter welding process. (2) drug skin melting rate should slow the melting rate of the core wire to cause the trumpet-shaped sets of Jane (sleeve length should be less than the diameter of the core wire), favor the droplet transfer and protection due to the atmosphere; (3) the proportion of slag should be less than the proportion of molten metal solidification temperature should be slightly lower than the metal solidification temperature, and the slag shell should be easy to take off; (4) having a blended gold and metallurgical processing role; (5) to adapt to a variety of position welding. 2. Electrode composition Electrodes constitute two parts by welding core drug skin. The electrode is a metal core welding the uniform coatings (drug leather), pressure to carefully coated welding core. Different types of electrodes, the core wire is also different. Core welding electrode metal core, in order to ensure the quality and performance of the weld, butt core content of metal elements, there are stringent regulations, especially the content of harmful impurities (such as sulfur, phosphorus, etc.), should be strictly limit, is superior to the base material. Welding core components directly affect the composition and properties of the weld metal, so the harmful elements in the core welding to be as little as possible. The C content should be less than 0.10%. H08A, with S less than or equal to O. 03%, P less than or equal to 0.03%, and C is less than or equal to 0.1%. Welding of carbon steel and low alloy steel welding core, generally as a low carbon steel core wire, and fill plus manganese, silicon, chromium, nickel, and other ingredients (see the wire the national standard GB1300-77). Because on the one hand use low-carbon low carbon steel wire good plasticity, wire drawing is relatively easy, the other hand, can reduce the CO content of the reducing gas to reduce the splashing or stomata, and the elevated temperature at the time of solidification of the weld metal, overhead welding favorable. Other alloying elements in order to ensure the comprehensive mechanical properties of the weld, welding performance and remove impurities, also have a role. High alloy steel, aluminum, copper, cast iron and other metal materials, welding core components in addition to the requirements of the weld metal similar, the same should control the content of impurities, and press process requirements often by adding certain alloying elements. 3. Electrode model with grades (1) electrode grades Structural steel, for example: grades, the preparation method. Knot XXX, became structural steel welding rod, 3 figures, on behalf of the drug skin type, welding current requirements, 1 and 2: representative of the tensile strength of the weld metal. (2) Electrode Model The model of the electrode is determined according to the national standards with international standards. EXXX, structural steel, for example, model preparation for the letter "E" said electrode, the first two deposited metal and a minimum tensile strength of the third digit indicates the welding rod welding position, third, the four-digit types of welding current and medicated skin type. 4. Electrode classification Welding electrodes under different circumstances, there are three classifications: at electrode purpose classification, the main chemical ingredient of the drug skin classification drug skin melted slag characteristics. In accordance with the use of welding rod, welding electrode can be divided into: structural steel welding rod, heat-resistant steel electrode, stainless steel electrode, welding electrodes, low temperature steel electrodes, cast iron welding rod, nickel and nickel alloy rod, copper and copper alloys, aluminum and aluminum alloy rods and special-purpose welding rod. Classified according to the chemical composition of the electrode coating, welding electrodes can be divided into: titania type electrode, titanium calcium type electrode the ilmenite type electrode, iron oxide-type electrode, cellulose-type electrode, low hydrogen type electrode graphite electrode and the base electrode. If classified in accordance with the melting of the electrode covering the characteristics of the slag, welding electrodes can be divided into acid electrode and alkaline electrode. Acid electrode drug skin main ingredients of the acidic oxides such as silica, titanium dioxide, sesquioxide, iron, etc.. Alkaline electrode covering the main component of the alkaline oxides, such as marble, fluorite.