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The economic efficiency and rationality of material selection for pressure vessels: Under normal circumstances, selecting materials in accordance with the following guidelines is economical and reasonable: 1. When the required thickness of the steel plate is less than 8 mm, carbon steel plates should be used instead of low-alloy steel plates, except in the case of multi-layer containers; 2. In situations where stiffness or structural design is of primary importance, carbon steel should be chosen. In applications where strength is the primary design consideration, steel plates such as Q235B, Q235C, Q245R, and Q345R should be selected accordingly, taking into account usage constraints related to pressure, temperature, and the medium involved. 3. When the required thickness of the stainless steel plate exceeds 16 mm, structural approaches such as lining, compounding, or surfacing should be employed. 4. Stainless steel should not be used when the design temperature is 500°C or lower. 5. Pearlite heat-resistant steel should also not be used when the design temperature is 350°C or lower. 6. The variety and specifications of steel materials should be reduced and combined as much as possible. Principles for selecting steel materials: The principles for choosing different types of steel serve as guidelines for material selection in design. 1. Carbon steel can be used in atmospheric and low-pressure vessels where the corrosivity of the medium is not high, in medium-pressure vessels with thin walls, in forgings, pressure-bearing steel pipes, non-pressure components, and in other situations where the wall thickness is determined by rigidity or structural factors. 2. Low-alloy steel can be used in pressure vessels where the medium is not highly corrosive and the wall thickness is large (≥8mm). 3. Pearlite heat-resistant steel can be used as a heat-resistant steel for resisting high-temperature hydrogen and high-temperature hydrogen + hydrogen sulfide corrosion, or for pressure vessels with design temperatures ranging from 350°C to 575°C. 4. Austenitic stainless steel can be used in environments with high corrosivity of the medium, to prevent iron ion contamination, and in heat-resistant or cryogenic containers with a design temperature above 500°C or below -100°C. For austenitic stainless steel containers in intergranular corrosion environments, the following design temperature limits should be considered: 1) Low-carbon unsaturated austenitic stainless steel: ≤300°C; 2) Ultra-low carbon austenitic stainless steel with a molybdenum content of not more than 3%: ≤350°C; 3) Ultra-low carbon austenitic stainless steel with a molybdenum content greater than 3%: ≤400°C; 4) Low-carbon stabilized austenitic stainless steel: ≤400°C. 5. Austenitic stainless steels that do not contain stabilizing elements such as titanium or niobium and have a carbon content of more than 0.03%, and which are subjected to hot working processes such as hot forming or welding at temperatures above 300°C, should not be used in environments where intergranular corrosion of the stainless steel may occur. (Basis for this text: HG/T20581-2020)