Table of contents for New Types of Steel
- ASTM A710 Grade B
ASTM A710 Grade B the name of a high-performance structural steel A copper-precipitation-hardened, high-performance Grade 70 weathering steel and was developed at developed at Northwestern University with the support of the Federal Highway Administration, the Illinois Department of Transportation, and Northwestern University’s Infrastructure Technology Institute.
The steel is not only stronger then conventional high-performance structural steel it is also cheaper and easier to make and needs less maintenance then conventional high-performance structural steel. The steel was designed to achieve a minimum of 70 ksi yield strength on air cooling from hot rolling without quenching and tempering (Q&T), accelerated cooling or thermomechanically-controlled processing (TMCP). This allows for elimination of alloying elements needed for hardenability as well as a low carbon content, resulting in a very low carbon equivalent for welding. As a result, its processing cost is less than for Q&T or TMCP steels. For steelmakers, this means that special equipment for Q&T or TMCP is not required.
ASTM A710 Grade B steel possesses high Charpy absorbed impact fracture energies at really low temperatures. By the addition of titanium (up to 0.1%) which combines with interstitial atoms, the absorbed impact fracture energy further increases. This addition lowers the yield stress to 60 Ksi minimum but increases the Charpy Absorbed Impact Fracture Energy to more than 265 ft-lbs at -80oF
Because of its very low carbon equivalent, ASTM A710 Grade B steel typically does not require pre-heat or post-heat amid welding with matching welding consumables. Weatherability of ASTM A710 Grade B steel is more suitable than that of any other commercially available weathering steel. Paint on this steel resists degeneration much better than on other weathering steels.
This steel does not contain intended additions of chromium. This is of interest because of health and environmental hazards due to accumulation of carcinogenic Cr+6 well welding.
The combination of these properties can result in significant cost savings when this steel is used instead of other structural steels.
This form of steel has been around for a couple years now ASTM A710 Grade B steel was used in 2000 to retrofit the I-55/I-64/I-70/US-40 Poplar Street Bridge Complex over the Mississippi River, East St. Louis, Illinois. High strength steel was required for the retrofit because of weight limitations and for the high fracture energy that was required for seismic redundancy.
In 2006 this steel was used for construction of a bridge in Lake Villa, Illinois. For the north Milwaukee Avenue Bridge, 500 tons of steel plates were produced and fabricated into girders. The bridge was not painted, resulting in a significant savings in construction and maintenance costs.
ASTM A710 Grade B steel can be used in applications that require high strength, good fracture toughness at low temperatures, easy welding, good weatherability and corrosion resistance. These potential applications include:
- tank cars
- pipe lines
- oil platforms
- guard rails and sign poles
- tall buildings for wind and seismic resistance
- power and illumination towers
- construction and mining equipment
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