In the 14MnNbq
steel welding on the beams of Wuhu Yangtze River bridge, multiple layer welding is used for thick plates, thus each HAZ (heat affected zone) may be subject to
heating several times. When weld wire of high capacity is used for the welding, the HAZ may become crisp due to the repeated heating. In order to facilitate the research, the paper introduces the use of Gleeble 1500 heating simulation tester to simulate the heating cycles of each HAZ affected by 14MnNbq steel welding. Thus we have a single uniform enlarged zone for the test. And then we can further locate the crispest zone and determine its toughness. As for the issue of being crisp due to welding overheating, we made a comparison between the 14MnNbq steel and foreign SM490C bridge steel. Under the same heating and cooling conditions, we analyzed the structure and
toughness of the simulated HAZ′s at various peaks values and compared the sensitivity of these two kinds of steel to
overheat crispness. The test results show that the crispest HAZ occurs in the process of welding of the 14MnNbq steel on the first
heat circulation submerged welding overheat zone and the second heat circulation submerged welding overheat zone plus the not entirely re crystallized zone. The 14MnNbq steel has a tendency of being crisper due to overheat than the SM490C steel is. In order to ensure the toughness of the welding HAZ′s, the welding wire capacity should be properly controlled during welding.
More abstracts about the Study of Toughness of Heat Affected Zone of 14MnNbq Steel Welding