Weathering steel

China Suppliers


Properties

"Weathering" means that due to their chemical compositions, these steels exhibit increased resistance to atmospheric corrosion compared to unalloyed steels. This is because the steel forms a protective layer on its surface under the influence of the weather.

The corrosion-retarding effect of the protective layer is produced by the particular distribution and concentration of alloying elements in it. The layer protecting the surface develops and regenerates continuously when subjected to the influence of the weather. pneumatic check valve

Chemical composition of Cor-ten grades smc air regulator

Grade taper lock

 %C

 %Si

 %Mn

 %P

 %S

 %Cr

 %Cu

 %V

 %Ni

Cor-ten A

0.12

0.25-0.75

0.20-0.50

0.07-0.15

0.030

0.50-1.25

0.25-0.55

0.65

Cor-ten B

0.16

0.30-0.50

0.80-1.25

0.030

0.030

0.40-0.65

0.25-0.40

0.02-0.10

0.40

The mechanical properties of weathering steels depend on which alloy and how thick the material is.

ASTM A 242

The original A 242 alloy has a yield strength of 50,000 pounds per square inch (340,000 kPa) and ultimate tensile strength of 70,000 psi (480,000 kPa) for light-medium rolled shapes and plates up to 0.75 inches (19 mm) thick. It has yield strength of 46,000 psi (320,000 kPa) and ultimate strength of 67,000 psi (460,000 kPa) for medium weight rolled shapes and plates from 0.751 inch (1925 mm) thick. The thickest rolled sections and plates from 1.54 in (38100 mm) thick have yield strength of 42,000 psi (290,000 kPa) and ultimate strength of 63,000 psi (430,000 kPa).

ASTM A 588

A 588 has a yield strength of at least 50,000 psi (340,000 kPa), and ultimate tensile strength of 70,000 psi (480,000 kPa) for all rolled shapes and plate thicknesses up to 4 in (100 mm) thick. Plates from 45 in (100130 mm) have yield strength at least 46,000 psi (320,000 kPa) and ultimate tensile strength at least 67,000 psi (460,000 kPa), and plates from 58 in (130200 mm) thick have yield strength at least 42,000 psi (290,000 kPa) and ultimate tensile strength at least 63,000 psi (430,000 kPa).

Usage

Weathering steel is popularly used in outdoor sculptures, such as in the large Chicago Picasso sculpture, and as exterior facades, for its rustic antique appearance. Examples include The Angel of the North, Gateshead, UK and the Humanites and Arts complex at Leeds Metropolitan University - Broadcasting Place - Leeds, UK

It has also been used in bridge and other large structural applications such as the New River Gorge Bridge, the newer span of the Newburgh-Beacon Bridge, and the creation of the Australian Centre for Contemporary Art (ACCA).

It is very widely used in marine transportation, in the construction of Intermodal containers.

The first use of COR-TEN for architectural applications was the John Deere World Headquarters in Moline, Illinois. The building was designed by architect Eero Saarinen, and completed in 1964. In 1977, Robert Indiana created a Hebrew version of the Love sculpture using the four letter word ahava ( "love" in Hebrew) made from COR-TEN, for the Israel Museum Art Garden in Jerusalem, Israel.

COR-TEN was used in 1971 for an order of electric railcars built by the St. Louis Car Company for Illinois Central Railroad. The use of COR-TEN was seen as a cost-cutting move in comparison with the contemporary railcar standard of stainless steel. A subsequent order in 1979 was built to similar specs, including COR-TEN bodies, by Bombardier. The cars were painted, a standard practice for COR-TEN railcars. However, the durability of COR-TEN did not live up to expectations, with rust holes appearing in the railcars. Ironically, painting may have contributed to the problem, as painted weathering steel is no more corrosion-resistant than conventional steel, because the protective patina will not form in time to prevent corrosion over a localized area of attack such as a small paint failure. Most of these railcars still operate out of Chicago.

Usage challenges

Using weathering steel in construction presents several challenges. Ensuring that weld-points weather at the same rate as the other materials may require special welding techniques or material. Weathering steel is not rustproof in itself. If water is allowed to accumulate in pockets, those areas will experience higher corrosion rates, so provision for drainage must be made. Weathering steel is sensitive to salt-laden air environments. In such environments, it is possible that the protective patina may not stabilize but instead continue to corrode. Hawaii's Aloha Stadium, built in 1975, is one example of this. The former Omni Coliseum, built in 1972 in Atlanta, Georgia, never stopped rusting, and eventually large holes appeared in the structure. This was a major factor in the decision to demolish it just 25 years after construction. Weathering steel's normal surface weathering can also 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 weathering steel. Staining can be prevented if the structure can be detailed so that water does not drain from the steel onto concrete where stains would be visible.

References

^ http://www.uss.com/corp/trademarks.asp, accessed Oct. 31, 2007

^ Plate Products, 2003-10-31, http://web.archive.org/web/20071228143615/http://www.uss.com/corp/products/plate.htm, retrieved 2010-01-13. 

^ COR-TEN - Weather & Corrosion Resistant Steel: Technical Data, archived from the original on 2010-01-13, http://www.webcitation.org/5mkm6z6UZ, retrieved 2010-01-13. 

^ http://www.chapelsteel.com/A588.html, accessed Sept 21, 2006

^ Manual of Steel Construction, 8th Edition, Second Revised Printing, American Institute of Steel Construction, Chicago, 1987; chapter 1 page 15

^ http://news.google.co.uk/news/url?sa=t&ct2=uk%2F0_0_s_4_0_t&usg=AFQjCNECcd8YzVj4xwFhAvipLt-EIHTvYA&cid=0&ei=1Vj_StDtNKKEjAeE4Nr4Ag&rt=SEARCH&vm=STANDARD&url=http%3A%2F%2Fwww.bdonline.co.uk%2Fstory.asp%3Fsectioncode%3D426%26storycode%3D3152952%26channel%3D426%26c%3D2%26encCode%3D0000000001a704e4

^ "Shipping Container Homes Globally". http://www.containerhomes-info.com/. Retrieved 2009-05-24. 

^ For pictures see http://people.ku.edu/~dunville

External links

Wikimedia Commons has media related to: COR-TEN-Steel

Report on Performance of Weathering Steel in Highway Bridges from the American Iron and Steel Institute

Report on Weathering Steel in TxDOT Bridges from the Texas Department of Transportation (4464 KB). Contains recommended details to avoid staining. Note: wrapping of piers was later found not to be cost-effective.

H.B. No. 282: House Bill 282 regarding Aloha Stadium

Stadium rust to get $12.4M treatment an article from the Honolulu Advertiser

A Primer on Weathering Steel: a white paper from the National Steel Bridge Alliance

Corten FAQ from the American Institute of Steel Construction

Weathering steel: A technical overview of weathering steels for bridges and general construction

Categories: Steels | Sculpture materials