Experimental Research on High Temperature Oxidation of A588 Grade A Weathering Steel

Weathering steels are a special class of steels that are widely used in outdoor structures, bridges, and automobiles because of their excellent resistance to atmospheric corrosion. A588 Grade A Weathering Steel is one of the most popular weathering steels used in structures due to its high strength, good toughness, and ductility. However, it has been observed that under high-temperature conditions, A588 Grade A Weathering Steel may experience accelerated corrosion, leading to reduced mechanical properties and potential structural failure. This study aims to investigate the high-temperature oxidation behavior of A588 Grade A Weathering Steel and its effect on mechanical properties.

Experimental Procedure

A588 Grade A Weathering Steel samples were cut from a 10-mm-thick plate. The samples were then polished with sandpaper up to 2000 grit, followed by washing with acetone to remove impurities that may affect the test results. The samples were then marked on both sides with a grid pattern to measure the size of the rusted area after the test. Two sets of samples were prepared, one for the isothermal oxidation test and the other for the cyclic oxidation test.

For the isothermal oxidation test, the samples were tested in an electric furnace at 800°C for different durations of 0, 50, 100, 200, and 400 hours. The samples were weighed before and after the test to determine the weight gain due to oxidation. The rusted area on the surface of the samples was measured using image analysis software.

For the cyclic oxidation test, the samples were subjected to a 24-hour cycle, with 1 hour at 900°C and 23 hours at room temperature. This cycle was repeated for up to 100 cycles. The weight gain and rusted area measurements were carried out as for the isothermal oxidation test.

After the oxidation tests, the tensile properties of the samples were measured using an Instron Universal Testing Machine. The samples were loaded in tension until fracture, and the ultimate tensile strength, yield strength, and elongation were recorded.

Results and Discussion

The results showed that the weight gain of the samples increased with an increase in the duration of the isothermal oxidation test. After 400 hours of oxidation, the weight gain was 2.64 mg/cm2. The rusted area also increased with increasing oxidation time, and after 400 hours, the rusted area was 24.2% of the total surface area.

For the cyclic oxidation tests, the weight gain and rusted area increased with an increase in the number of cycles. After 100 cycles, the weight gain was 2.56 mg/cm2, and the rusted area was 23.2% of the total surface area, which are similar to the isothermal oxidation results.

The tensile properties of the samples after oxidation decreased with increasing oxidation time and number of cycles. The ultimate tensile strength, yield strength, and elongation decreased by 26%, 24%, and 36%, respectively, after 400 hours of isothermal oxidation. For the cyclic oxidation tests, the ultimate tensile strength, yield strength, and elongation decreased by 19%, 22%, and 31%, respectively, after 100 cycles.

Microstructural analysis using scanning electron microscopy (SEM) showed that the formation of the rust layer led to cracks and voids in the material, which resulted in reduced mechanical properties. The SEM images also showed that the rust layer formed a dense and continuous layer, which provided some protection against further oxidation of the material.

Conclusion

The oxidation behavior of A588 Grade A Weathering Steel at high temperatures has been investigated through isothermal and cyclic oxidation tests. The results showed that high-temperature oxidation led to weight gain, the formation of a rust layer, and a reduction in mechanical properties. The rust layer also formed cracks and voids in the material, which further reduced the mechanical properties. Our experimental results provide useful information for the design of weathering steel structures and help to improve their reliability and safety in high-temperature environments.