Three situations regarding 304 and 316 stainless steels
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This post was last edited by qqsbig001 on 2023-5-20 at 16:37. Three situations were encountered during online searches: 1. 304 also performs well in terms of heat resistance, with a typical operating temperature limit of less than 650°C. 2. To achieve the best corrosion resistance, the welded section of 316 stainless steel requires post-weld annealing. 3. 【However, within the range of 427°C–857°C, it is not advisable to use 316 stainless steel continuously】 and 【within the range of 800–1575°C, it is also not recommended to use 316 stainless steel continuously】. Question: 1. When designing heat exchangers, is 304 not recommended for pressures above 650°C at low temperatures? By referring to the allowable stress table in GB150, it can be seen that 316 has slightly better stress resistance than 304. 2. When the medium is air, is it possible to skip the post-weld annealing process for 316? 3. Which one of the two 【】 is correct? If the former is correct, then isn’t 316 not recommended for heat exchangers at temperatures above 650°C? Heat exchanger tube side parameters: 1.0 MPa, 660°C, fluid: air. The shell side has low water temperature, and 304 is planned to be used.
1. If the operating temperature exceeds 650°C, it is not recommended to use 304 stainless steel. Although 304 stainless steel performs well in terms of heat resistance, it still faces the risk of intergranular corrosion at high temperatures. Furthermore, when used under high temperature and high pressure, 316 stainless steel exhibits better pressure resistance. 2. After welding, the welded joint of 316 stainless steel requires annealing to maximize its corrosion resistance. If the medium is air, it can be decided based on specific circumstances whether post-weld annealing is necessary; generally, it is not required. 3. Different sources may provide different answers. Under normal conditions, the operating temperature range for 316 stainless steel at high temperatures is 427°C–857°C. If this temperature range is exceeded, it will lead to a decline in the mechanical properties and corrosion resistance of 316 stainless steel. Therefore, if 316 stainless steel is to be used in the range of 800–1575 degrees, evaluation and special consideration are required. .