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

7CrMoVTiB10-10(T24)钢在一定的使用条件下(在120~250℃温度范围内的机械载荷和腐蚀载荷的共同作用下)，在焊缝区域观察到不希望的应力腐蚀开裂(SCC)。在本项目的框架内，深入研究了这一裂纹萌生和扩展过程的机制以及使用预处理(焊接、热处理、预氧化)和加载条件(单调变形时的应变速率、叠加循环加载参数、温度、O2含量和水介质的pH值)对其影响的可能性。该项目的目的是确定显著影响焊缝区材料应力腐蚀敏感性的微观结构、环境和载荷因素和标准。在评估结果后，建议者将确定适当的措施，以提高材料的抗应力腐蚀能力。这些研究将使用各种商业测量和分析方法(扫描电子显微镜、扫描电子显微镜-能谱分析、纳米压痕、无限聚焦显微镜的光学轮廓分析、使用X射线和中子测量残余应力)。此外，建议者开发的试验方法将适应本项目的要求，并用于研究(高温水中的慢应变速率试验，水化学受控，以及表面应变场和体积发出的声信号的同时分析)。对现有的T24钢焊缝应力腐蚀开裂现象的认识和理解，对其他铁素体和贝氏体钢、低合金钢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.