Analysis Of Neutron Diffraction Stress Of Hydrogen-resistant Steel And Its Components

Hydrogen-resistant austenitic stainless steel HR-2 is one kind of special metal using for making special accessories and structure for hydrogen storage vessel, this kind of products had been widely used in industry\spaceflight\military\energy sources. As structure for hydrogen storage vessel, in the service period it will endure high pressure hydrogen gas for long time. The material used for the hydrogen storage vessel is always being some kind of special hydrogen-resistant austenitic stainless steel. Although the performance of the hydrogen damage is better than that of ferrite and martensite steel, but the performance is still unlike the early recognition of that completely unaffected by hydrogen. The hydrogen still had strong influence on the material properties, micro defects and stress distribution. Especially under the process of stress and high pressure hydrogen loading, the influence will become more and more complicate. The structural safety of the hydrogen storage vessel has always been a key problem in its service life. Using the neutron diffraction technology to carry out hydrogen-resistant austenitic stainless steel HR-2 and its structure parts’mechanics performance research, help to understand the evolution of hydrogen resistant steel microstructures and mechanical properties more clearly, the work will give great contribution to the pressure hydrogen container structure design/improvement/safety evaluation in the future.Within the last two decades neutron diffraction had been developed as an alterbative and complementary technique to the X-ray method. Until the early 1980s, an experimental setup for the measurement of residual strain was first built up; neutron diffraction technoplogy had been first used for the stress investigation in the industry field. Neutron diffraction, as an important nondestructive testing method, has the important characteristics of deep penetration and sensitive to hydrogen. By neutron diffraction stress/strain measurement technology, the macro-stress, micro-stress and intergranular stress distribution of the object can be accurately obtained in the depth range. Making the research between the exit and change of the stress and the influence to the micro-structure becomes possible, analyzing on the distribution and change of the stress and strain, crystal twin and dislocation can be determined.As the only nondestructive technical method of three-dimensional stress investigation, the neutron diffraction stress measurement technique has been paid attention to in the world. The United States/Europe/Asia, including Los Alamos, Oak Ridge, the National Institute of standards and Technology (NIST), Rutherford-Appleton lab. (ISIS), ILL (Grenoble), a lot of national laboratories or research centers consider neutron diffraction stress measurement technology as the most important tool on solving the engineering material or structure problem. In the future, developing the in-situ neutron scattering techniques to establish the application in micro (meso) mechanical model, serving in the advanced material design field.In this paper, based on the hydrogen-resistant austenitic stainless steel HR-2 sample with different hydrogen charging amount and combined with the several stages of deformation characters in the macro stress-strain curve, the in-situ neutron diffraction experiment had been developed in the residual stress neutron diffractometer in CMRR, Mianyang, China. To explore the influence of hydrogen concentration contributed on the mechanical properties, and to study the essence reason and the microscopic mechanism compared with the change of the macroscopic mechanical properties.The three-dimensional stress distribution of the welding steel (HR-2) cylinder formed by the electron beam welding is investigated in this paper. This kind of welding cylinder always used for the hydrogen storage vessel, the requirement for stress distribution and local strain gradient is strict. Measuring and mapping the accurate stress distribution to evaluate the material preparation and welding molding process of safety and reliability become very improtant.