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1. Scope: This standard applies to the design of welded chemical storage vessels made of low-alloy high-strength steels, pearlitic heat-resistant steels, stainless steels, and stainless steel composite sheets, for applications where the pressure is not greater than 35.0 MAp and the design temperature is above -20 degrees Celsius. The types of materials include rolled products, forgings, as well as welded materials. The container body refers to the shell and the head. Takeover. Flange. Tube sheets, etc.) and their accessories. The selection of welding materials, technical requirements, scope of application, etc., shall meet the requirements of the standards. When higher or special requirements are imposed on the materials due to design considerations, these shall be specified in the drawings or corresponding documents. 2. Criteria for material selection: (1) When selecting steel for chemical processing vessels, factors such as the operating conditions of the equipment (e.g., design pressure, design temperature, properties of the medium), the weldability of the material, its cost-performance ratio in cold and hot conditions, heat treatment requirements, and the structure of the vessel must be taken into consideration. (2) When selecting steel materials for chemical process vessels, economic rationality should be considered on the premise of meeting the requirements specified in (1) of this standard. Under normal circumstances, the following guidelines are economically reasonable: a. When the required thickness of the steel plate is less than 8 mm, carbon steel plates are preferable over low-alloy high-strength steel plates, except for materials used in multi-layer containers. b. In applications where stiffness and structural design are of primary importance, ordinary carbon steel should be chosen. In applications where strength design is the primary consideration, steel plates such as Q235A, Q253B, Q235C, Q245R, and Q345R should be selected for non-compressed elements based on constraints related to pressure, temperature, and the medium in use; whereas steel plates such as Q235B, Q235C, Q245R, and Q345R are used for compressed elements. c. When the required thickness of the stainless steel plate is greater than 12 mm, it is advisable to use lining, cladding, or other similar structural methods. d. Stainless steel should be avoided as a heat-resistant steel for design temperatures of 500 degrees Celsius or less. e. Pearlite heat-resistant steels should preferably not be used as heat-resistant steels for applications with a design temperature of 350 degrees Celsius or less. When pearlitic heat-resistant steel should be used for heat-resistant or hydrogen-resistant applications, the variety and specifications of the steel materials should be minimized and combined as much as possible. (3) The selection principles for the various types of steel materials listed in these conditions serve as guidelines for material selection in design; under normal circumstances, they should be followed when making such selections. a. Carbon steel is used for atmospheric and low-pressure vessels with weak corrosive media, medium-pressure vessels with relatively thin walls, forgings, pressure-bearing steel pipes, non-pressure components, and other applications where the wall thickness is determined by rigid structural factors. b. Low-alloy high-strength steel is used for pressurized vessels in environments with mild medium corrosion, where the wall thickness is large (greater than 8 mm). c. Pearlite heat-resistant steel is used to resist corrosion by high-temperature hydrogen or hydrogen sulfide, or as a heat-resistant steel for pressure vessels with design temperatures of 350–575 degrees Celsius. d. Stainless steel is used in environments with high medium corrosivity, as well as in heat-resistant steels or low-temperature steels that can resist iron ion contamination, or in applications where the design temperature is above 500 degrees Celsius or below -70 degrees Celsius. e. Austenitic stainless steels that are free of titanium and niobium, are chemically stable, and have a carbon content of more than 0.03% should not be used in environments that may cause intergranular corrosion of the stainless steel when welded or subjected to heat treatment at temperatures above 400 degrees Celsius. (4) In addition to meeting the requirements of relevant steel standards, the steel shall also comply with the technical requirements for steel, as well as the provisions regarding usage restrictions and scope set out in this standard. (5) The steel used as standard components in chemical processing equipment such as equipment flanges, pipe flanges, pipe fittings, manholes, and level gauges should comply with the **standards applicable to such components, as well as the technical requirements specified by industry standards. The above information was prepared by the Technical Department of Jiangsu Xinbaifa Stainless Steel Co., Ltd. for reference only. More to follow; we will discuss the technical requirements for steel shortly. Please stay tuned.