Development of an Improved HPS-100W Steel for Bridge Applications

摘要

After extensive laboratory studies, a Cu-Ni alloy steel with significantly improved properties for 690 MPa (100 ksi) yield-strength weathering steel infrastructure applications, such as bridges, was recommended. To confirm these results, a 150 MT (165-ton) full-scale heat of the recommended composition was produced. Plate and tubular products were evaluated for 690 MPa (100 ksi) applications by quenching and temper-aging. The investigation indicated that the products replicated quite faithfully the excellent strength, toughness, and weldability observed in plates from laboratory heats. Additional refinement of the chemistry took place with another laboratory heat with higher manganese content. The results indicated that the hardenability and the yield and tensile strength after aging were increased sufficiently to ensure meeting a minimum yield strength of 690 MPa (100 ksi) through 64 mm (2-1/2-inch) plates. Based on the Alternative ASTM Standard G 101 (Predictive Method Using the Data of Townsend), the steel shows an excellent calculated atmospheric weathering corrosion index of 7.5. On the basis of these studies, the following composition is proposed for an HPS-100W Cu-Ni age-hardening ASTM A709 Grade in weight percent: 0.06 C, 1.25 Mn, 1.00 Cu, 0.75 Ni, 0.50 Mo, 0.50 Cr, 0.02 Cb and 0.06 V. Additional large-scale programs are currently underway to document improved mechanical properties and weldability and to test prototype HPS-100W girders for strength, ductility, fatigue, and fracture performance.