SMA490BW耐候钢不同焊接区域裂纹扩展门槛值研究

Study on crack extension threshold value in different welding areas of SMA490BW weathering steel

对SMA490BW耐候钢MAG熔化焊接头的焊核区和热影响区在不同应力比下的裂纹扩展门槛值进行研究,比较两种焊接区域在不同应力比下的抗裂纹扩展能力,用光学显微镜观察两种焊接区域的显微组织,分析应力比和显微组织对裂纹扩展门槛值的影响。结果表明:在同一应力比下,焊核区的裂纹扩展门槛值和抗裂纹扩展能力高于热影响区;对于同种焊接区域,应力比为-1时的裂纹扩展门槛值和抗裂纹扩展能力比应力比为0时的高;焊核区组织的晶粒比热影响区粗大,导致焊核区的裂纹扩展门槛值大于热影响区。

The crack propagation thresholds in the weld core zone and affected zone of MAG fusion welded joints of SMA490BWweathering steel under different stress ratios were studied,and the crack propagation resistance of the two welding areas underdifferent stress ratios was compared. The microstructure of the two welding areas was observed by optical microscope,and theeffects of stress ratios and microstructures on the crack propagation thresholds were analyzed. The results show that at the samestress ratio,the threshold value and anti-crack growth ability of weld core zone are higher than those of heat affected zone. Forthe same welding area,the threshold value of crack propagation and the ability to resist crack propagation when the stress ratio is-1 are higher than those when the stress ratio is 0. The grain size in the weld nugget zone is coarser than that in the heat affectedzone,which leads to the larger crack propagation threshold in the weld nugget zone than that in the heat affected zone.