HPb58-2 brass has good mechanical properties, processing properties and corrosion resistance. It is widely used in the manufacture of sanitary products, water supply and drainage pipes, medals, serpentine tubes, condensing tubes, cartridges and various shapes of complex products and small hardware. Wait. Brass has good corrosion resistance, but is sensitive to stress corrosion cracking, especially brass with zinc content greater than 15% (mass fraction) has high stress corrosion cracking sensitivity. Therefore, after the processing of brass, stress relief treatment is needed to reduce the tendency of stress corrosion cracking; in the case of corrosive media, brass has greater stress corrosion cracking sensitivity to sulfur-containing corrosive media, such as corrosive elements in the environment. When sulfur, oxygen, chlorine, etc. are present, the occurrence of stress corrosion cracking is accelerated.
From fracture analysis, metallographic examination and energy spectrum analysis, it can be seen that there is no obvious macroscopic deformation of the angle valve fracture. The crack source is on the inner surface, the crack is bifurcated, and the fracture microscopically is characterized by cleavage brittle fracture. Corrosive elements such as sulfur, oxygen, chlorine, etc., these characteristics indicate that angular valve cracking is a typical stress corrosion cracking. Stress corrosion cracking needs to meet two conditions, one is corrosive medium, and the other is stress, especially tensile stress. It can be inferred that there is a certain tensile stress inside these cracked angle valves. According to some sources, this tensile stress is often derived from processes such as welding, cold working, heat treatment, and assembly.
Angle valve failure is a typical stress corrosion cracking, and the excessive stress of the angle valve assembly is the main cause of stress corrosion cracking. It is recommended to control the assembly force when assembling the brass angle valve to avoid excessive internal stress in the angle valve and cause early failure of the angle valve.
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