Cor-ten
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Cor-ten, generically known as A242, A588, and A606, are steel alloys which were developed to obviate the need for painting, and form a stable rust-like appearance if exposed to the weather for several years. The United States Steel company (USS) held a Registered trademark on the name COR-TEN, though this passed to International Steel Group when that company purchased USS' heavy steel plate business. [1]
In some geographies it may be known without the hyphen as "Corten steel".
The original Cor-ten received the standard designation A242 ("Cor-ten A") from the ASTM International standards group. Newer grades are A588 ("Cor-ten B") and A606 for thin sheet. All alloys are in common production and use.
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[edit] Properties
The mechanical properties of Cor-ten steels depend on which alloy and how thick the material is. [2] [3] [4]
[edit] A588
A588 Cor-ten has a tensile strength yield strength of at least 50 KSI (50,000 PSI, 345 MPa), and ultimate tensile strength of 70 KSI (480 MPa) for all rolled shapes and plate thicknesses up to 4.0 inches thick. Plates from 4.0 to 5.0 inches have yield strength at least 46 KSI (320 MPa) and ultimate tensile strength at least 67 KSI (460 MPa), and plates from 5.0 to 8.0 inches thick have yield strength at least 42 KSI (290 MPa) and ultimate tensile strength at least 63 KSI (435 MPa).
[edit] A242
The older A242 alloy has a tensile to yield strength of 50 KSI (345 MPa) and ultimate tensile strength of 70 KSI (480 MPa) for light-medium rolled shapes and plates up to 0.75 inch thickness. It has yield strength of 46 KSI (320 MPa) and ultimate strength of 67 KSI (460 MPa) for medium weight rolled shapes and plates from 0.75 to 1.50 inch thick. The thickest rolled sections and plates from 1.50 to 4.0 inches thick have yield strength of 42 KSI (290 MPa) and ultimate strength of 63 KSI (435 MPa).
[edit] Usage
Cor-ten steel is popularly used in outdoor sculptures and as exterior facades for its rustic antique appearance.
It has also been used in bridge and other large structural applications such as the New River Gorge Bridge and the newer span of the Newburgh-Beacon Bridge.
It is very widely used in marine transportation, in the construction of shipping containers.
[edit] Usage Challenges
The use of Cor-ten in construction presents several challenges:
[edit] Weld-area corrosion
Ensuring that weld-points weather at the same rate as the other materials may require special welding techniques or material.
[edit] Trapped water corrosion
It is not a rustproof material. If water is allowed to accumulate in pockets, those areas will experience higher corrosion rates, so provision for drainage must be made.
[edit] Inspection
It requires periodic inspection, so provision for inspection must be made
[edit] Discoloration
Cor-ten's normal surface weathering can lead to rust stains on nearby surfaces.
The U.S. Steel Tower in Pittsburgh, Pennsylvania was constructed by U.S. Steel in part to showcase Cor-ten steel. The initial weathering of the material resulted in a discoloration of the surrounding city sidewalks, as well as other nearby buildings. A cleanup effort was orchestrated by the corporation once weathering was complete to undo this damage, but the sidewalks still have a decidedly rusty tinge. This problem has been reduced in newer formulations of Cor-ten steel.
[edit] References
- ^ http://www.uss.com/corp/products/plate.htm, Accessed Sept 21, 2006
- ^ http://www.chapelsteel.com/A588.html, accessed Sept 21, 2006
- ^ http://www.intlsteel.com/PDFs/platespec11.pdf, Accessed Sept 21, 2006
- ^ Manual of Steel Construction, 8th Edition, Second Revised Printing, American Institute of Steel Construction, Chicago, 1987; chapter 1 page 1-5
[edit] External links
- Corten FAQ from the American Institute of Steel Construction
- Example projects from ArchINFORM site.
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