In the manufacture of large-diameter welded pipes used for the construction of pipelines operating at high pressure, it is extremely important to provide the required mechanical and service characteristics. One of the main tasks of improving the quality of each batch of sheet metal, while maintaining or reducing the cost of production of pipes, is to provide a set of mechanical properties. The problems of obtaining proper mechanical characteristics of sheet products of the widely used 10G2FB steel during its production have been raised for several years. This is explained by the facts that this steel is still used in the construction of trunk pipelines and the technological process for the production of rolled products is a multi-factor system, the accomplishment of each stage of which directly affects the quality. In this paper, we consider issues related to the study of the texture state of samples cut from 6 pipes (from different batches, different manufacturers) made of 10G2FB lowcarbon steel in order to construct direct and inverse pole figures and determine the role of texture formation in the properties of the base metal. A comparative analysis of the obtained results of mechanical tests is carried out. A comparison of the test results for impact toughness and crack resistance with the results of texture analysis showed that pipe samples, in the structure of which after rolling the textures were formed, which were determined as maximum when controlling reflections from a series of planes (110), showed the best viscous properties in low temperature impact bending tests and in the entire range of studies in tests for crack resistance.

Hydrogen can be used in the same energy processes as natural gas and become a tool for implementing the transition to a sustainable low-carbon economy. The level of contamination resulting from controlled combustion of hydrogen or methane-hydrogen mixture is relatively low, which will significantly reduce CO2 emissions. However, the use of hydrogen can involve considerable difficulties associated with the hydrogen compatibility of materials. With the increase in the production, storage and transportation of hydrogen gas, including through gas pipelines, hydrogen-resistant materials are needed. The main problem with hydrogen is its embrittling effect. Under the influence of hydrogen, pipelines materials can probably have the following: hydrogen charging of the surface layer under pressure, loss of plasticity at tensile loads, formation of cracks and blisters (by decogesia mechanism), diffusion to the stress concentrator according to adsorption theory, accumulation of hydrogen at the top of the crack (which can lead to cracking) and so on. To assess the possibility of using a pipeline system for transportation of hydrogen gas in large volumes, it is necessary to know hydrogen compatibility of pipe steel. Physical modeling of steel resistance to hydrogen embrittlement can be carried out using electrochemical and gas charging methods.

To assess resistance to hydrogen embrittlement caused by the presence of hydrogen in the transported product, and, accordingly, suitability of pipes for hydrogen transport, the base metal of large-diameter pipes of X52 strength class manufactured by JSC “ChelPipe” (part of the PJSC “TMK” group of companies) was studied. The work included the study of pure gaseous hydrogen effect under pressure up to 10 MPa on change in mechanical characteristics of the base metal of large-diameter pipes (LDP) during preliminary hydrogen charging for various time periods in a stationary autoclave under pressure, and during simultaneous loading with a slow strain rate (SSRT) under expected operating conditions. Results of the X52 LDP metal study show that there is no significant impact on the effect of gaseous hydrogen under pressure for up to 144 hours on mechanical characteristics of the base metal determined by static uniaxial tension (decrease in ductile characteristics does not exceed 9 %). During SSRT at a rate of not more than 1·10–6 s–1 in pure gaseous hydrogen environment under a pressure of 10 MPa, the change in strength and ductile characteristics does not exceed 13 % in comparison with reference tests in nitrogen environment under the same pressure. The results obtained allow us to consider that the base metal of low-alloy pipe steel with ferrite-perlite microstructure of X52 strength class is sufficiently resistant to hydrogen embrittlement. Final confirmation of the possibility to use LDP made from steel under study will be the results of further qualification tests, including the study of the weld metal and heat-affected zone properties.

Currently, a new generation of pressurized water reactor for nuclear power plants with an extended service life (up to 60 years) and a guarantee of their complete safety are being designed in Russia. Analysis of the reactor internal elements performance showed, that designed service life cannot be guaranteed if the reactor’s internal parts would be made from currently used stainless steel (18-10 alloy type). Instead of the used steel, to ensure operability, new austenitic stainless steel (16-25 alloy type), with increased resistance to radiation swelling, is being developed for production of forged ring blanks for core baffle. The use of new steel requires revision of the existing metallurgical production technology stages. Therefore in this paper diffusion experiment was carried out to determine the required duration of homogenization. The results are presented in terms of different duration of the high-temperature exposure effect on the liquation heterogeneity equalization. The relation between duration of homogenization and microhardness is also shown.