Brazing caused the stainless steel to fail/a batch of 316L stainless steel purchased by the customer was used for less than one year after being made into a small heat exchanger, and the damage phenomenon of cracks occurred. Even if the circulating steam pressure and flow rate were reduced, the customer suspected it was Because of the material problem, the quality objection was raised. After careful inspection, it was found that the crack site contained a large amount of copper element, and the content of copper element was much higher than the standard. Through inspection of the production process, it was found that the heat exchanger was connected by brazing. Stainless steel cannot be brazed, because the liquid copper penetrates deep along the grain boundary during welding, causing intergranular corrosion and increasing local stress, which can cause fatigue cracks. Due to the serious cracking phenomenon, the heat exchanger is basically scrapped. Incorrect welding methods may greatly reduce the service life of stainless steel. When stainless steel is used, in addition to the correct choice of material, the correct choice of processing method is also required. Due to the serious cracking phenomenon, the heat exchanger is basically scrapped. Incorrect welding methods may greatly reduce the service life of stainless steel. When stainless steel is used, in addition to the correct choice of material, the correct choice of processing method is also required.