Dissimilar Metal Welds Between ASTM A709 Grade 50CR and Other Bridge Steels

Steel bridges can be susceptible to corrosion if adequate corrosion protection design and detailing is not provided. Specific portions of bridges can be especially vulnerable to corrosion, such as near bridge joints where moisture is common due to leaks and on spans over water or high volume roads with heavy de-icing salt application, such as overpasses over interstates in metropolitan areas. In recent years, Virginia Department of Transportation (VDOT) has begun using ASTM A709 Grade 50CR (50CR) in corrosive environments where uncoated ASTM A709 Grade 50W (50W) (i.e., weathering steel) is not recommended, such as bridges with low water clearance, near industrial areas, and in marine environments. Although 50CR steel has shown outstanding corrosion resistance, its initial cost is greater than traditional steel bridge corrosion protection systems such as uncoated 50W. A proposed solution for corrosion on steel bridges and to minimize the cost of 50CR is to use dissimilar metal welded connections. These types of connections would allow 50CR to be used in targeted corrosive portions of a steel bridge, while traditional corrosion protection systems could be used elsewhere. For example, a corroded beam end on existing bridge made with ASTM A36 (A36) steel could be repaired by cutting out the corroded portion and welding a new 50CR beam end to the existing A36 steel beam to provide additional corrosion resistance under the joint. A similar concept could also be used in new designs in which 50CR is used on a water or overpass span over an interstate, and uncoated 50W steel is used throughout the remainder of the structure. This research will investigate the weldability, nondestructive evaluation, weld metallurgical structure, mechanical properties, and corrosion implications of 50CR dissimilar metal welds. This research will also evaluate the cost-effectiveness of 50CR dissimilar metal welds in both repair and new construction applications.