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Considering the physical properties, mechanical properties, and chemical composition of the weld material: (1) For welding structural steel, the principle of equal strength is generally applied, with welding materials selected to meet the mechanical property requirements of the joint. (2) For welded joints between dissimilar steels such as low-carbon steel and low-alloy steel, welding materials corresponding to the steel with the lower strength grade are generally selected. (3) For the welding of heat-resistant steels and stainless steels, in addition to considering strength, it is also necessary to ensure that the main chemical composition of the weld metal is similar to that of the base material. (4) When the chemical composition of the base material contains high levels of harmful impurities such as carbon, sulfur, or phosphorus, welding materials with stronger crack resistance should be selected. Such as low-hydrogen welding materials, etc. Considering the operating conditions and performance of the welded parts: (1) When subjected to dynamic and impact loads, in addition to requirements for tensile strength and yield strength, high demands are placed on impact toughness and plasticity as well. Low-hydrogen welding materials should be used at this time. (2) When welded parts operate in corrosive media, it is necessary to identify the type of medium, its concentration, operating temperature, and the type of corrosion (general corrosion, intergranular corrosion, stress corrosion, etc.), in order to select the appropriate stainless steel welding material. (3) When the welded parts are in operation under wear conditions, it is necessary to determine whether it is normal wear or impact wear, intermetallic wear or abrasive wear, and whether the wear occurs at normal temperature or at high temperature. It is also necessary to consider whether operation in a corrosive medium is involved, in order to select the appropriate surfacing welding material. (4) For weldments operating at low or high temperatures, welding materials that can ensure mechanical properties under such conditions should be selected. Considering factors such as the complexity and structural characteristics of the welded parts, as well as the type of weld joint: (1) Welded parts with complex shapes or large thicknesses are prone to cracking due to the high internal stresses generated when the weld metal contracts upon cooling. Therefore, welding materials with good crack resistance must be used, such as low-hydrogen electrodes and high-toughness electrodes. (2) For certain joints with small grooves, or those where strict control over root penetration is required, welding materials with greater penetration capacity should be used. (3) When certain welding areas are difficult to clean thoroughly due to various constraints, it is advisable to use welding materials that are not sensitive to rust, scale, and oil stains, such as acidic electrodes, in order to avoid defects like pores. Considering the spatial location of the weld, some welding materials are suitable only for welding at certain locations and perform poorly when used in other locations, while other materials can be used for welding in various locations. When selecting such materials, it is necessary to take into account the characteristics of the welding location. Considering the welding conditions and operating environment: (1) In cases where there is no DC welder, welding materials suitable for both AC and DC should be selected. (2) For certain steels (such as pearlitic heat-resistant steels), post-weld stress relief heat treatment is required. However, when this cannot be carried out due to equipment limitations or structural constraints of the material itself, welding materials with a different chemical composition from that of the base metal should be selected (such as austenitic stainless steel welding materials); this eliminates the need for post-weld heat treatment. (3) Welding materials should be selected appropriately based on the conditions at the construction site, such as outdoor operations and the welding environment. (4) Where both acidic and alkaline electrodes can be used, acidic electrodes should be preferred as much as possible, given that alkaline electrodes require higher levels of operational skill and preparation. Consider the economics of welding: (1) While ensuring satisfactory performance, choose welding materials with the best cost-performance ratio. (2) For primary and secondary welds with different performance requirements, different welding materials can be used; there is no need to solely pursue comprehensive performance characteristics in the welding materials. Considering welding efficiency, for structures that require a large amount of welding work, high-efficiency welding materials should be used whenever possible, such as welding wires, ferroalloy electrodes, and efficient stainless steel electrodes.