Study ot the stress corrosion cracking in the weld seam of low alloyed steels with particular regard to the steel T24

7CrMoVTiB10-10 （T24）钢在一定的操作条件下（温度范围为120 ~ 250℃的机械和腐蚀载荷组合），在焊缝区域观察到不必要的应力腐蚀开裂（SCC）。在本项目框架内，深入研究了该裂纹萌生和扩展过程的机理，以及预处理（焊接、热处理、预氧化）和加载条件（单调变形应变速率、叠加循环加载参数、温度、水介质O2含量和pH值）对裂纹萌生和扩展过程的影响可能性。该项目的目的是确定影响焊缝区域材料对SCC敏感性的微观结构、环境和载荷因素和标准。在对结果进行评估后，建议者将确定适当的措施来提高材料的抗SCC能力。各种商业测量和分析方法将用于这些研究（SEM， SEM- edx分析，纳米压痕，无限聚焦显微镜的光学轮廓分析，使用x射线和中子的残余应力测量）。此外，由提案人开发的测试方法将适应本项目的要求，并用于研究（在控制水化学的高温水中进行慢应变速率测试，同时分析表面应变场和从体积发出的声信号）。对T24钢焊缝SCC现象的现有认识和理解的预期贡献对其他铁素体、贝氏体、低合金和耐热钢也具有重要意义。

Under certain operational conditions (combination of mechanical and corrosive loading at temperatures in the range from 120 to 250°C), an unwanted stress corrosion cracking (SCC) in the region of the weld seams is observed in the steel 7CrMoVTiB10-10 (T24). Within the frame of this project, the mechanisms of this crack initiation and crack propagation process and the possibility to influence using pretreatments [welding, thermal treatment, preoxidation) and the loading conditions (strain rate at monotonic deformation, parameters of superimposed cyclic loading, temperature, O2 content and pH value of the aqueous medium) are studied thoroughly. The aim of the project is the identification of microstructural, environmental and loading factors and criteria that effect the susceptibility to SCC of the material in the region of the weld seam, significantly. After the evaluation of the results, the proposers will determine suitable measures to improve the resistance of the material to SCC. Various commercial measuring as well as analytical procedures will be used for these studies (SEM, SEM-EDX analysis, nanoindentation, optical profile analysis with an infinite focus microscope, residual stress measurements using X-rays and neutrons). Additionally, test methods developed by the proposers will be adapted to the requirements of this project and employd for the studies (slow strain rate tests in high temperature water with controlled water chemistry and a simultaneous analysis of surface strain fields and acoustic signals emitted form the volume). The expected contributions to the existing knowledge and understanding of the SCC phenomena in the weld seam of the steel T24 are also of significance for other ferritic and bainitic, low alloyed and heat-resistant steels.