How to eliminate residual stress in carbon steel heat exchangers?

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Residual stresses in carbon steel heat exchangers can be eliminated through post-weld heat treatment (such as stress-relief annealing). By heating the workpiece to 500–650°C, holding it at that temperature, and then cooling it slowly, this method effectively releases the internal stresses generated during welding, thereby improving the sealing performance and structural stability of the flange. The specific process parameters are as follows: Heating temperature: For carbon steel, it is usually 500–650°C; it is recommended to maintain this temperature between 600–650°C for better results. Heat retention time: Calculated based on the wall thickness of the workpiece; generally, 1 hour is required for every 25 mm of thickness, with a minimum of 30 minutes. Cooling method: It must be cooled slowly along with the furnace, with the cooling rate controlled at ≤200°C/h to avoid the generation of new thermal stresses. Applicable scenarios: Suitable for tube boxes with split diaphragms, floating head covers, or carbon steel tube boxes with lateral openings exceeding 1/3 of the cylinder’s inner diameter. Additionally, vibration aging can be used as an auxiliary method, especially suitable for large components or those that cannot be placed entirely in a furnace, as it can reduce the peak residual stress by about 50%.