145 Weldability and Weathering Characteristics 1451 Weldability

One advantage of HPS over conventional high-strength steels is its enhanced weldability due to the lower carbon content in HPS. Because HPS can be welded under less stringent conditions when compared to conventional high-strength steels, the recommended procedures for welding high-strength steels outlined in Americal Welding Society (AWS) D1.5 Bridge Welding Code (AWS 2002) is also applicable to welding HPS. In addition, an addendum is available (AASHTO 2000a) to provide guidance to bridge engineers interested in using HPS in bridge design and construction.

One of the most common problems for bridge welds is hydrogen induced (cold) cracking in the heat affected and fusion zones of the welds. Because hydrogen can come from many sources such as atmosphere, water/moisture, grease, oxides, and contaminants, it is not an easy task to eliminate all hydrogen sources during the welding process. To reduce the likelihood of hydrogen induced cracking, one needs to select the material carefully, exercise proper handling techniques for the consumables, and follow established guidelines for welding procedures (AWS 2002). Specifying minimum preheat and interpass temperature for welding also helps to minimize diffusible hydrogen during production welding of HPS. High preheat temperature allows more time for hydrogen to diffuse from the welds and it reduces the chance for the formation of brittle microstructures where cracks can initiate. Table 14.4 shows the minimum preheat and interpass temperature for HPS70W using the two recommended welding processes for HPS — submerged arc welding (SAW) and shield metal arc

TABLE 14.4 Minimum Preheat and Interpass Temperature for HPS70W (HPS485W)
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