窄间隙埋弧焊Q690高强钢微区电化学及应力腐蚀行为与机制研究

For the 690MPa grade high strength steel for off-shore engineering and the twin-wire narrow-gap sub-merged arc welding technology, utilizing the Gleeble welding thermal simulation and the SVET micro-electrochemical testing technology, carry out the research on the relationship with the microstructure, mechanical properties and electrochemical characterization of the Q690 steel at different welding simulation condition, explore the influence of Cl- concentration on the joints at different stress in the solution, analyze the relationship between the crack tip medium condition and the crack propagation rate in different environment, to build up and optimize the crack tip electrochemical condition prediction model. The experimental contents are designed systematically from such field as the high strength steel base metal characterization, NG-SAW welding technology, electrochemical and stress corrosive mechanism. The expected results have the industry application background in the field of the off-shore engineering equipment manufacturing, has positive significance on the application of the related industrial field and the research on the welded high strength steel corrosion theory, as could provide the theoretical basis and technical support for the off-shore engineering equipment manufacturing and the ocean anticorrosive, and is beneficial to enhance the level of off-shore engineering equipment manufacturing in China, as well as accelerate the process to develop the marine resources.

针对海洋工程690MPa级高强钢及窄间隙埋双丝埋弧焊技术，利用Gleeble焊接热模拟和SVET微区电化学测试技术，研究Q690高强钢在不同Gleeble焊接模拟参数条件下的组织、力学性能与电化学行为之间的相互关系，探索不同应力条件下Cl-离子浓度对溶液中接头腐蚀行为的影响，分析不同环境中裂纹尖端介质条件和裂纹扩展速率之间的关系，建立和优化裂纹尖端电化学条件预测模型。从高强钢母材特性、窄间隙埋弧焊技术、电化学和应力腐蚀机理等方面进行了较为系统的研究内容设计。预期成果具有海洋工程装备制造领域的工业应用背景，对海工装备领域的应用及高强钢焊缝腐蚀理论研究具有积极意义，可为海工装备制造和海洋防腐提供理论依据和技术支持，有利于提升我国海工装备制造水平，加快开发海洋资源的进程。

面向海洋工程装备领域，针对海洋工程用Q690高强钢窄间隙埋弧焊，利用Gleeble焊接热模拟方法，建立了Q690高强钢在不同焊接工艺参数条件下的组织、力学性能与电化学行为之间的相互关系，热循环次数为4次时试样具有最好微区电化学均匀性和耐腐蚀性能。随着浸泡时间的延长，不同热模拟峰值温度的试样表面微区电化学行为均有所改善，峰值温度为950℃和1350℃的试样稳定后的腐蚀速度逐渐降低，整体腐蚀速度波动程度小且稳定。优化了Q690高强钢厚板焊接工艺参数，获得了最佳窄间隙埋弧焊工艺区间，实现了厚度为60mm、110mm和180mm的Q690高强钢厚板的可靠焊接，接头性能均满足国家标准（抗拉强度≥690MPa，低温冲击≥31J）。研究了焊接接头母材、热影响区和焊缝等不同区域的微区电化学行为。明确了焊接接头的电化学行为与应力腐蚀机制，在慢应变速率应力腐蚀拉伸测试速度为1×10-6/s的3.5%NaCl溶液环境中，焊接接头力学性能受应力疲劳腐蚀影响显著下降，但仍然能达到母材要求的屈服强度。项目成果可为海洋工程装备的制造提供高质高效焊接技术和科学依据。