Comparative study of A588 Grade B weathering steel and A709 Grade 50 common steel

Weathering steel, also known as COR-TEN steel, is a type of steel that has enhanced atmospheric corrosion resistance. Compared to common steel, weathering steel forms an adherent protective oxide layer on its surface, which slows down the corrosion process. A588 Grade B and A709 Grade 50 are two grades of weathering steel that are commonly used in a range of applications, including bridges, buildings, and outdoor sculptures.

A588 Grade B Weathering Steel

A588 Grade B is a high-strength low-alloy steel (HSLA) that has enhanced atmospheric corrosion resistance. This grade of weathering steel is also known as Corten B. It is equivalent to ASTM A242 and A709-50W steels, and it has a tensile strength of 70-100 ksi and a yield strength of 50 ksi.

The main alloying elements in A588 Grade B are copper, chromium, and nickel, which provide the steel with improved corrosion resistance. The addition of copper gives the steel a reddish-brown patina when exposed to the weather, which is highly desirable for architectural and aesthetic purposes.

A709 Grade 50 Common Steel

A709 Grade 50 is a high-strength low-alloy steel (HSLA) that is commonly used in structural applications such as bridges and buildings. This grade of steel has a yield strength of 50 ksi and a tensile strength of 65 ksi.

The main alloying elements in A709 Grade 50 are carbon and manganese, with traces of other elements such as phosphorus, sulfur, and silicon. This steel has good weldability and formability, and it is often used for the construction of large structures.

Comparative Study

The following are some of the key differences and similarities between A588 Grade B weathering steel and A709 Grade 50 common steel:

1. Corrosion Resistance

A588 Grade B weathering steel has superior atmospheric corrosion resistance compared to A709 Grade 50 common steel. This is due to the protective layer that forms on the surface of the steel when exposed to the weather.

On the other hand, A709 Grade 50 common steel does not contain copper, chromium or nickel, which are the key alloying elements in weathering steel that enhance corrosion resistance. Therefore, it is more susceptible to rust and corrosion over time.

2. Aesthetic Appearance

A588 Grade B weathering steel has a distinctive reddish-brown patina that develops over time when exposed to the weather. This patina is highly desirable for architectural and aesthetic purposes, and it gives the steel a unique appearance that blends well with natural surroundings.

In contrast, A709 Grade 50 common steel does not develop a patina over time. It remains the same dull gray color, which may not be as visually appealing as weathering steel.

3. Cost

A709 Grade 50 common steel is generally less expensive than A588 Grade B weathering steel. This is due to the fact that A709 Grade 50 is commonly used in structural applications, while A588 Grade B is used for aesthetic purposes such as outdoor sculptures and architectural features.

4. Weldability

A709 Grade 50 common steel has good weldability and can be easily welded using common welding methods. This makes it a popular choice for the construction of large structures that require welding.

In contrast, A588 Grade B weathering steel can be more difficult to weld due to its high copper content. Special precautions must be taken when welding weathering steel to ensure that the welds are strong and durable.

5. Strength and Durability

Both A588 Grade B weathering steel and A709 Grade 50 common steel have high strength and durability. They are both capable of withstanding extreme weather conditions and are resistant to rust and corrosion.

However, A588 Grade B weathering steel has slightly higher strength and durability due to the presence of copper, chromium, and nickel. These alloying elements enhance the steel's ability to resist corrosion and provide it with greater durability over time.

In summary, A588 Grade B weathering steel and A709 Grade 50 common steel are two grades of steel with different properties and applications. A588 Grade B weathering steel has superior atmospheric corrosion resistance and a distinctive aesthetic appearance, making it a popular choice for architectural and aesthetic features. A709 Grade 50 common steel, on the other hand, is preferred for structural applications due to its lower cost and good weldability. Ultimately, the choice of steel depends on the specific application and the desired properties required for that application.