Weathering steel, also known as corrosion-resistant steel, is a type of steel that is specifically designed to resist corrosion and oxidation in atmospheric conditions. The most common grade of weathering steel is A588, which is widely used in bridges, buildings, and other outdoor structures.
Fractography is the study of the fracture surface of a material. It is a valuable tool for understanding the failure mechanisms of a material and can provide insight into the causes of failure.
In this study, we investigated the fractography of A588 grade weathering steel plates under corrosive conditions. The aim was to understand the effects of corrosion on the fracture properties of the material and to identify the failure mechanisms.
Experimental Procedure
The experimental procedure involved exposing the A588 grade weathering steel plates to a corrosive environment for a period of 30 days. The corrosion environment was created by immersing the plates in a 3.5% NaCl solution. The plates were then removed from the corrosive environment, cleaned, and allowed to dry.
Once the plates were dry, tensile tests were performed in accordance with ASTM E8M. The tensile tests were conducted using a universal testing machine at a strain rate of 0.05 mm/min. The fractured surfaces of the test specimens were then examined using a scanning electron microscope (SEM) to analyze the fracture morphology.
Results and Discussion
The tensile tests showed a significant reduction in the mechanical properties of the A588 grade weathering steel plates after exposure to the corrosive environment. The ultimate tensile strength decreased from 574 MPa to 455 MPa, and the yield strength decreased from 483 MPa to 355 MPa. The elongation at failure also decreased from 21% to 16%.
The SEM images of the fracture surfaces showed that the failure mechanism of the A588 grade weathering steel plates changed from ductile to brittle after exposure to the corrosive environment. The fracture surfaces of the specimens that were not exposed to the corrosive environment exhibited a typical ductile fracture morphology, characterized by smooth and uniform dimples on the surface.
On the other hand, the fracture surfaces of the specimens that were exposed to the corrosive environment exhibited a mixed fracture morphology, consisting of both ductile and brittle features. The ductile features were characterized by dimples, while the brittle features were characterized by flat, featureless areas.
The SEM images also revealed the presence of corrosion products on the fracture surfaces of the specimens that were exposed to the corrosive environment. The corrosion products appeared as rough, irregular areas on the surface, and were concentrated around the brittle features of the fracture surfaces.
The presence of corrosion products on the fracture surfaces indicates that the corrosion of the material played a significant role in the fracture process. The corrosion weakened the material, making it more susceptible to brittle fracture.
Conclusion
In conclusion, the fractography of A588 grade weathering steel plates under corrosive conditions revealed that the corrosion of the material significantly affects its fracture properties. The mechanical properties of the material were significantly reduced after exposure to the corrosive environment, and the failure mechanism changed from ductile to brittle.
The presence of corrosion products on the fracture surfaces indicates that the corrosion of the material played a significant role in the fracture process. It weakened the material, making it more susceptible to brittle fracture.
These findings highlight the importance of considering the effects of corrosion when designing structures made from A588 grade weathering steel. It may be necessary to use protective coatings or other corrosion-resistant materials in order to maintain the mechanical properties of the material and prevent failure.
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