Stress corrosion cracking of the pre-immersed tin brass heat exchanger tube in an ammoniacal solution

摘要

The stress corrosion cracking (SCC) of the pre-immersed tin brass heat exchanger tube was investigated using slow strain rate testing (SSRT) in an environment containing ammonia. Tubular specimens were exposed at room temperature to this environment for different time prior to straining. The brass tube operated for longer time exhibited more severe SSC cracking and larger dezincified area than that of the tube operated for shorter time. Intergranular SSC was observed in the fracture surface of the specimen pre-immersed for short time, whereas both intergranular and transgranular SCC were observed at the fracture surface of the specimen pre-immersed for longer time. Furthermore, many pits were observed in the fracture surface of the material. A dezincification had occurred after SSRT and the severity of a dezincified area through the tube is depended on the pre-immersion conditions applied to tube. Stress-strain diagrams showed a decrease in tensile properties of the tin brass tube due to the formation of SCC. Remarkable decrease of the ultimate tensile strength (UTS) and fracture strain of tin brass specimens was found due to SCC.