Metallurgical hydrogen as an indicator and cause of damage of rolled steel

Fatigue tests and measurements of the volumetric distribution of metallurgical hydrogen in specimens cut from rolled I-beam 60Sh3 made of steel 10KhSND were carried out. Fatigue tests show a 20% reduction in fatigue limits compared to similar sheet material. On the fractures of the samples, there are flock-like defects in the areas of interface of the flanges of the I-beam or in the so-called zones of difficult deformation. The concentration of metallurgical hydrogen is unevenly distributed and varies from 0.17 ppm to 1.8 ppm. Large concentrations of hydrogen are observed in the zones of difficult deformation, which indicates the hydrogen nature of the metal defects observed at the fracture. The result of mechanical tests and hydrogen diagnostics is a manufacturing defect of rolled products that cannot be corrected. Hydrogen diagnostics using metallurgical hydrogen (without hydrogen charging samples) requires essentially less time than mechanical tests and yields the adequate result

Determining the bound energies of dissolved hydrogen on the basis of a multichannel diffusion model in a solid

A hypothesis of the multichannel character of hydrogen diffusion in solids has been substantiated in the paper. Based on this hypothesis, a mathematical model of hydrogen diffusion in the crystalline lattice was constructed. The model allowed determining the dissolved hydrogen binding energies using an extraction curve. The curve is measured by an industrial vacuum-extraction procedure with mass-spectrometric detection of hydrogen streams. The paper presents various experimental data that supports the validity of the multichannel model and discusses the advantages and disadvantages of the proposed approach in comparison with the well-known method of thermal desorption spectra (TDS) that is recognized as the classical way of experimentally determining dissolved hydrogen binding energy in solids

Modeling of the plasticity of microstructured and nanostructured materials

A new approach to modeling of the plasticity of materials with nanostructure and ultrafine one has been proposed. Its main advantage is the minimum number of physical parameters in use. In the context of the proposed model, we calculated the volumetric density of the energy of surface tension of the material grains. This energy is a significant part of the internal energy during deformation. The size dependence of the melting temperature of nanoparticles was compared with experimental data. We obtained size dependence of the yield point on its basis. Yield point was interpreted as the result of changes of grains surface energy during the deformation. The obtained yield point dependence on the grain size was related to the Hall–Petch law, and this resulted in confirmation of the hypothesis on the crucial role of surface tension forces in the initial stage of plastic deformation of ultrafine materials

Surface vs diffusion in TDS of hydrogen

The paper addresses the numerical simulation of conditions in which the measurement of thermal desorption spectra of hydrogen (TDS) is carried out. Plane steel samples of 10 mm thickness were used as the specimens for simulation. The skin effect which is observed with standard hydrogen charging of samples was accounted for the initial conditions. The standard diffusion of hydrogen was simulated according to Fick’s law. Solution of the Fick’s equation is obtained by finite element methods using the developed code. The resulting solutions show that standard hydrogen charging can lead to the appearance of an additional TDS peak, even without taking into account the traps. New interpretation of the TDS method for hydrogen dissolved in a solid was suggested

The description of deformation and destruction of materials containing hydrogen by means of rheological model

The two-continuum rheological model taking account of a change in the hydrogen-binding energy has been proposed in this paper. As in the case of conventional approach our model makes it possible to describe the hydrogen transfer and its accumulation in the metals and to explain changes in the mechanical properties of metals that are caused by that accumulation. The proposed rheological model describes the hydrogen transition from a mobile state to the bound one, depending on the stress–strain state. Concurrent with this achievement our model describes the changes in the material matrix taking place as a result of the hydrogen addition to the matrix atoms. These processes lead to weakening and destruction of the material