Effect of Different Brazing Atmospheres in Furnace on Corrosion Resistance of Stainless Steels
Considering the safety and economy of enterprise production,the protective atmosphere in the brazing process of copper heat exchanger for domestic gas instantaneous water heater is changed from ammonia decomposition gas atmosphere to natural gas atmosphere.It is prone to oxidation corrosion for 304 stainless steel spoiler spring in water channel of a heat exchanger.Taking 430 and 304 stainless steel spoiler springs as the object,the springs were brazed at 800-830℃in a mesh belt high temperature brazing furnace with ammonia decomposition gas and natural gas atmosphere,then the atmospheric oxidation test for 24,48 h and neutral salt spray test for 72 h were carried out.The influence of ammonia dissociation gas and natural gas atmosphere at high temperature on the corrosion resistance of the stainless steels was studied.The results show that the 304 stainless steel spoiler spring brazed by ammonia decomposition gas and natural gas atmosphere produces obvious corrosion after 24 and 48 h atmospheric oxidation test,and the natural gas protection atmosphere aggravates its corrosion degree.The brazing temperature in the furnace of 800-830℃reaches the sensitization temperature range of 304 stainless steel,resulting in intercrystal corrosion,and it has an obvious impact on its oxidation resistance,but has no obvious impact on 430 stainless steel material.The corrosion resistance of 430 stainless steel is better than that of 304 stainless steel under the same conditions.It is recommended to choose 430 stainless steel spring in heat exchanger channel pipeline.
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