海洋用高强钢的延迟断裂及环境氢侵入行为研究

High strength steel is susceptible to delayed fracture and the susceptibility is enhanced with increasing its strength level. For tailoring further advanced high strength steels and for safe usage of them in marine atmospheric environment, establishment of evaluation technique for the delayed fracture property of high strength steels is required strongly. In the study, critical hydrogen content of fracture and marine atmospherically environmental hydrogen entry are regarded as the factors for evaluation of delayed fracture susceptibility of high strength steels.. The critical hydrogen content of fracture will be examined by using slow strain rate test and conventional strain rate test of tensile specimens pre-charged with hydrogen in conjunction with hydrogen content measurement by means of thermal desorption analysis. To compare with critical hydrogen content, hydrogen entry under marine atmospheric environment will be investigated by means of electrochemical hydrogen permeation test to understand the effect of the rust layer and humidity on the hydrogen entry of high strength steel. Hydrogen content in the steel estimated by using electrochemical hydrogen permeation test will be compared with that obtained by means of thermal desorption analysis. In the present study more effective technique to evaluate the delayed fracture of marine high strength steel will be investigated, which will make a great contribution to the development of high strength steel and safety usage of structural materials.

针对高强钢在海洋大气环境中存在严重的氢致延迟断裂问题，本项目以海洋用高强钢的安全应用为目标，将发生延迟断裂的临界氢浓度和环境中侵入的氢相结合，对高强钢的延迟断裂敏感性进行研究。通过慢应变速率拉伸试验和常规应变速率拉伸试验结合氢热分析技术，探索高强钢的最大局部应力与临界氢浓度关系，建立简单高效的临界氢含量研究方法；并通过电化学氢渗透实验和氢热分析技术，研究环境因素如温度、湿度、污染物和腐蚀层等对钢的氢侵入行为影响。该研究为高强钢的强度开发和材料的安全使用奠定坚实基础，对海洋用高强钢强度开发及深海化应用具有重要意义。

随着海洋开发的深海化，海洋用高强度结构钢的研究已引起高度重视。但是，钢的强度越高，它对氢的敏感性也越高（延迟断裂）。针对高强钢在海洋大气环境中存在严重的氢致延迟断裂问题，本项目以海洋用高强钢的安全应用为目标，将发生延迟断裂的临界氢浓度和环境中侵入的氢相结合，对高强钢的延迟断裂敏感性进行了研究。主要取得了以下研究进展：（1）通过常规应变速率和慢应变拉伸试验获得断裂应力，结合氢热分析技术获得了断裂应力随可扩散氢浓度的变化关系；（2）通过计算两种实验的最大局部应力与局部氢浓度，揭示两种拉伸实验之间的本征关系；（3）定量研究了腐蚀环境中进入钢的氢浓度随时间变化规律，对比临界氢浓度研究评价其延迟断裂性能；（4）研究了激活能和扩散系数，结合断裂应力与氢浓度关系，深入研究了高强钢发生延迟断裂的机制。本项目的开展对海洋用高强钢强度开发及深海化应用具有重要意义，为高强钢的开发和材料的安全使用做出重要理论和实际指导。