High strength steel sheets are increasingly being used due to the growing need to improve fuel efficiency by reducing vehicle weight. Steel sheets are usually used as automotive parts formed by pressing, etc., and complicated strain is generated in the steel sheet after forming. This strain is thought to affect the occurrence of hydrogen embrittlement. In this study, a new hydrogen embrittlement evaluation method using a forming limit diagram was devised. A forming limit diagram of a steel sheet with a strength level adjusted to 1470 MPa was prepared for uniaxial, plane strain and biaxial modes, and stress and hydrogen were applied to the specimens formed with respective strain modes to evaluate the occurrence of fracture. In order to examine the relationship between the hydrogen content and the cracking, evaluation of the hydrogen content by Thermal Desorption Analysis, visualization of hydrogen by Secondary Ion Mass Spectrometry and microstructure analysis by Electron BackScatter Diffraction were carried out. It was found that cracks are generated in the strain mode in which hydrogen accumulates locally in the steel even when the apparent hydrogen content is small, and it was clarified experimentally that evaluation of local hydrogen concentration is important for the evaluation of hydrogen embrittlement.

由于越来越需要通过减轻车辆重量来提高燃料效率，因此越来越多地使用高强度钢板。钢板通常用作通过冲压等形成的汽车零件。，成形后在钢板上产生复杂的应变。该应变被认为影响氢脆的发生。在这项研究中，设计了一种新的利用成形极限图的氢脆评估方法。制备了将强度水平调整为1470 MPa的钢板的单轴，平面应变和双轴模式的成形极限图，并将应力和氢施加到以各个应变模式形成的试样上，以评估断裂的发生。为了检查氢含量与开裂之间的关系，通过热脱附分析评估氢含量，通过二次离子质谱法观察氢，并通过电子背散射衍射进行微观结构分析。