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The basic approach is that meeting the performance requirements of the product is the main criterion for selecting welding materials, with these performance requirements including strength, temperature, corrosion resistance, and the nature of the loads. These data are clearly reflected in the data sheets of the pressure vessel design drawings. Carefully reading the product’s data sheet and understanding its usage requirements is the first essential step in selecting welding materials. First, consult the applicable standards for the base material to understand its properties (mechanical properties, high-temperature properties, low-temperature properties, etc.) and chemical composition; if necessary, its carbon equivalent can be calculated to provide data for formulating the welding process later on. Select a welding material that is suitable based on the chemical composition, strength (tensile strength Rm, yield strength Rel), and toughness (impact test temperature, impact absorption energy) of the materials to be welded. The welding material chosen in this way will meet the usage requirements of the product, without the need to consider other requirements. It should be noted that there is a difference between the concepts of \"matching,\" \"similar,\" and \"identical.\" \"Matching\" refers to the specialized welding material for the material to be welded; when welded in accordance with the requirements of the welding process, it results in properties that are almost identical to those of the base material. This is the simplest and most practical method; it is possible to easily find the welding material corresponding to a given base metal by referring to welding procedures and samples provided by welding material manufacturers ； “\"Similar\" means that the chemical composition and mechanical properties of the deposited metal are similar, but the degree of variation in these properties is difficult to control; as a result, the same base material can be welded using various welding materials ； It is rare for welding materials to be completely \"identical\" to the base material; this is only occasionally used in tungsten inert gas welding, due to the specific requirements of that welding process. Specificities: The specifics of small manufacturing enterprises are mainly reflected in small production batches, a variety of metal materials, and low consumption of welding materials. If welding materials are selected based on the principle of matching each base material, there are also many corresponding welding materials. For enterprises that do not produce in bulk, there are many problems, mainly manifested as: ① increased difficulty in procurement. The amount of welding material required for single-piece production is relatively small, but to ensure sufficient production efficiency and meet process requirements, there are many different types and specifications available. ②Inspection costs have increased. Every time a batch of materials arrives, it needs to be inspected; for some special types of equipment such as boilers and category III pressure vessels, re-inspection is required, which incurs significant costs. ③Management becomes more difficult. To ensure control over welding quality, each batch of material must be stored separately. It also makes it more difficult to prepare procurement plans; purchase quantities are strictly controlled, and even the lack of a single welding rod requires re-purchasing it ； Purchasing in large quantities increases the capacity of the welding materials warehouse, which in turn raises the amount of working capital required. Some of these materials even remain in the warehouse forever, thereby increasing the cost of the products. To avoid the aforementioned problems, welding technicians need to have a comprehensive understanding of the properties of the materials to be welded as well as the products being welded.