Choose principles of welding rod Considerations as the weldment physical, chemical properties and chemical composition of selection principles: 1 according strength viewpoint, to meet the mechanical properties of the base material of the electrode, or a combination of mechanical properties of the base material of the electrode, or the strong bonded mother material weldable to switch to non strength and good weldability electrode, but considering the weld stiffness of the strength of the structure type, in order to meet requirements 2. They meet or close to the base metal alloy components 3. Parent material containing carbon, sulfur, phosphorus and harmful impurities should choose crack resistance resistance to stomatal better performance of the electrode. Suggested the use of titanium dioxide calcium type, ilmenite-type electrode. Still can not solve, you can selection of low-hydrogen electrodes Second, the principle of weldments working conditions and the use of performance considerations: 1. Withstand dynamic load and impact load case, in addition to ensuring the strength, impact toughness, elongation uniform have higher requirements, should be followed by selection of low-hydrogen calcium, titanium and iron oxide electrode Contact with corrosive media, must be based on the kind of medium, concentration, temperature as well as the distinction between general corrosion or intergranular corrosion, choose the stainless steel electrode Work wear conditions, a distinction should be made between general or by the impact wear, at room temperature or high temperature of 100 wear 4 very temperature conditions, guarantee low or high temperature mechanical properties of the electrodes should select the appropriate Third, consider factors: complexity of the weldment geometric beginning principles stiffness size, Preparation of the welding groove and the welding position is selected when: A complex shape or thickness weldments, weld metal cooling shrinkage stress, prone to cracks, crack resistance electrodes must be chosen, such as low-hydrogen electrodes high toughness welding rod or iron oxide electrode Weldments subject to conditions that can not be overturned, the selection can all position welding electrode Weldments. Welding parts difficult to clean up, the choice of oxidizing strong a sensitive acid electrode on the the oxidized skin and grease, to avoid holes and other defects Considerations for facilities welder ground equipment selection principle: DC welder, should not use the electrodes of the restriction of the use of DC power, and should be used to pay the electrode of the DC power supply. Certain steel products (such as pearlitic heat resistant steel) to eliminate heat treatment after welding needed, but by equipment limitations (or structural constraints) can not be subjected to a heat treatment, should be replaced by a non-parent metal material rod (such as austenitic stainless steel welding rod), need not be post-weld heat treatment Considerations to improve the welding process and to protect the health of workers choose principle: Maximize the use of acid electrode in place to meet the requirements of the acid electrode and alkaline electrode, Considerations: labor productivity and economic rationality principle: In the case of the use of the same performance, you should try to choose a price lower acid electrode, instead of the basic electrode, acid electrode turned titanium type titanium calcium type your should be vigorously promoted, according to the situation of China's mineral resources,