Optical method to study post-necking material behaviour

The article is devoted to the determination of equivalent stresses and strains in the minimum cross-section of the neck during tensile testing of cylindrical specimens. To correct the average tensile stresses, the Bridgman theory is used, based on the experimental measurement of the neck. The paper proposes an approach for calculating the radius of curvature of the neck based on the approximation equation that describes the entire profile of specimen. Its accuracy was estimated using the finite element method. A program has been developed that provides the measure of the diameter of specimen in the minimum cross-section of the neck and the calculation of the radius of its curvature from the video recording of the test process based on the proposed equation. Using this program, hardening curves for 09G2S steel were constructed at engineering, true and equivalent stresses. © 2020 Author(s).The study was made within the base part of state job in the field of VFLHQWLILF DFWLYLW\ ʋ -2020-0020 and was supported by the grant from the President of the Russian Federation for young scientists – candidates of sciences MK-1878.2020.8

Structure and mechanical properties of the welded joints of large-diameter pipes

The structure and mechanical properties of the technological welded joints of large-diameter pipes of strength class K60 produced by two companies are studied. Along with standard mechanical properties (σ0.2, σu, δ, ψ), specific work of deformation a (tensile toughness) and true rupture strength Sf are estimated from an analysis of the stress-strain diagrams constructed in true coordinates. The mechanical behavior is found to be different for samples cut from different zones of a welded joint (central weld, heat-affected zone, and base metal). The mutual correlation between parameters a, S f, and impact toughness KCV is considered. © 2013 Pleiades Publishing, Ltd

STRUCTURAL ASPECTS OF CONSRUCTIONAL STEELS PLASTISITY

The influence of strengthening mechanisms on the plasticity of low- and medium-carbon steels in different structural-phase condition is studied.В работе изучено влияние различных механизмов упрочнения на пластичность низко.и среднеуглеродистых конструкционных сталей в различном структурно.фазовом состоянии

Metastable austenitic steel structure and mechanical properties evolution in the process of cold radial forging

The article presents the influence of structure formation on the properties of 321 metastable austenitic stainless steel in the process of cold radial forging (CRF). The steel under study after austenitization was subjected to CRF at room temperature with degrees of true strain (e) 0.26, 0.56, 1.00, 1.71 and 2.14. It has been shown that structure formation of the studied steel during CRF consists of three stages: formation of the lamellar structure of austenite, formation of the trapezoidal structure, and formation of the equiaxial grain structure. The kinetics of the strain-induced α'-martensitic transformation is related to the stages of structure evolution. Hardness, ultimate tensile strength and yield strength uniformly increase in all stages of structure formation with a significant decrease of elongation to fracture during the first stage of structure formation while the value of elongation to fracture remains constant in the subsequent stages of deformation. Impact strength of fatigue cracked specimens (KCT) decreases sharply at the first stage of structure formation and smoothly increases at the second and third stages. However, the impact strength of V-notch specimens (KCV) continuously decreases when deformation degree increases in the overall investigated deformation range. © 2019 by the authors.Ministry of Science and Higher Education of the Russian FederationFunding: The work has been performed under the project No.11.8213.2017/8.9 within the framework of the basic part of the state assignment to universities in the field of scientific activity financed by the Ministry of Science and Higher Education of the Russian Federation

Parameters of Load-Displacement Curves and Their Correlation with the Fracture Surface in Medium-Carbon Steel

Impact tests are mandatory for a wide range of structural steel products to evaluate the required service life and operational safety. This test is especially relevant for products used in operation in climatic areas with a cold climate, since it allows one to determine the temperature range of the ductile-brittle transition. Depending on the structural-phase state of a metal, the type of the temperature relationship of impact toughness and its displacement on the temperature axis may differ significantly. For ductile materials, the temperature range of the ductile-brittle transition is shifted towards ultra-low negative temperatures whereas for materials in the embrittled condition it lies in the region of higher temperatures. Ductile-brittle transition behavior of medium-carbon steel with 0.32% C-1.35% Mn-0.003% B in two conditions (after normalization and after quenching and tempering) by instrumented impact testing and fracture analysis was studied. On the descending branch of the force-displacement curves the periods corresponding to different zones of propagation of the main crack are distinguished: period I is the ductile zone of pure shear, period II is the zone of brittle fracture, period III is the ductile zone of break fracture. Each period can be quantitatively described by a set of strength, plastic and gradient parameters. It is established that the displacement to the beginning of linear period II (SIIb ) and slope of the curve on it (ΔF/ΔS)II have a better correlation with shear fracture zone percentage (B) than the other distinguished parameters of force-displacement curves. © 2021, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved

Influence of crystallographic texture of TMCP pipe steel on the nature of deformation and fracture during tensile testing

The influence of crystallographic texture of low-carbon, low-alloyed pipe steel (06Mn2MoNb) after thermo-mechanical controlled processing on fracture deformation has been studied by means of tensile testing and electron backscatter diffraction (EBSD) method. The paper demonstrates that fracture in textured metallic materials is characterized by anisotropy, while its characteristics are orientation-dependent. © 2021 Elsevier B.V.. All rights reserved.This study was supported by the grant of the President of the Russian Federation, Project SP-3775.2021.1

Study of luders deformation in ultrafine low-carbon steel by the digital image correlation technique

The studied steel was a low-carbon microalloyed steel of type 08G2B, used for pipes with an outer diameter of 1420 mm for natural gas transportation with an operation pressure of 11.8 MPa with the chemical composition characterized by a low-carbon content (0.08 wt.%) with additions of Mn, Cr, Mo, Ni and microalloying elements (∑(Nb, V, Ti) ≈ 0.10 wt.%). Secondary refining and continuous casting followed by thermo-mechanical controlled processing (TMCP) with a strict temperature-reduction route and control of the post-deformation cooling rate are used to produce high-strength welded X80 and higher-grade pipes with an extremely ultrafine heterophase structure (d =1– 3 μm) and high Charpy energy of more than 250 J/cm2 at –40°С. Usually sheet metal is not subjected to heat treatment. However, pipes can be heated by applying an anti-corrosion coating at 200 – 250°C or by welding in a heat affected zone, which initiates the strain aging effect (SAE). The appearance of SAE can also occur upon prolonged exposure of pipes in the area of climatic temperatures, as well as in the course of installation and operation of pipelines, which inevitably leads to a change in the mechanical properties of the metal. Luders deformation in ultrafine low-carbon microalloyed steel X80 has been studied upon tensile testing by the digital image correlation technique. Two mechanisms of Luders deformation are shown to be observed depending on the strain ageing effect. It is determined that the mechanical behavior of the material at the stage of uniform deformation strongly correlates with the type of Luders deformation. © 2019, Institute for Metals Superplasticity Problems of Russian Academy of Sciences. All rights reserved.Government Council on Grants, Russian FederationБлагодарности/Acknowledgements. Работа выпол нена в УрФУ при финансовой поддержке постановления № 211 Правительства Российской Федерации, контракт № 02. А03.21.0006, а также в ИМАШ УрО РАН в рамках темы государственного задания №0391‑2016‑0004./The work was performed cooperatively in Ural Federal University with the support of the Government of the Russian Federation, resolution no. 211, contract no. 02. А03.21.0006 and in Institute of Engineering Science (Ural Branch of RAS) within the state theme no. 0391‑2016‑0004

Lüders deformation in specimens made of normalized 09G2S steel

The features of Lüders deformation in the normalized 09G2S steel are studied by the methods of digital image correlation, topography, and scanning electron microscopy of specimen faces. The paper studies the appearance, growth, structure, and location of deformation bands, as well as plastic strain in them. © 2021 Elsevier B.V.. All rights reserved.Ministry of Education and Science of the Russian Federation, Minobrnauka: AAAA-A18-118020190116-6The study was performed at the IMP UB RAS under a state assignment from the Ministry of Education and Science of Russia (theme Structure, No. AAAA-A18-118020190116-6) and within the research plan of the IES U

THE INFLUENCE OF ISOTHERMAL QUENCHING ON STRUCTURE AND PROPERTIES OF STEEL 37HGF

В работе исследованы микроструктура и механические свойства конструкционной стали 37ХГФ после термической обработки по различным режимам. Проведен сравнительный анализ микроструктуры и комплекса механических свойств в исходном горячекатаном состоянии, после улучшения и изотермической закалки.The microstructure and mechanical properties of constructional steel 37HGF after heat treatment on different regimes were investigated. Comparative analysis steel microstructure and mechanical properties after hot-rolling, quenching, tempering and isothermal quenching was carried out

Tensile Deformation and Fracture Behavior of API-5L X70 Line Pipe Steel

Thermo-mechanical controlled processing (TMCP) is employed to obtain the required level of mechanical properties of contemporary HSLA steel plates utilized for gas and oil pipeline production. The strength and crack resistance of pipeline steels are mainly determined by its microstructure and crystallographic texture. In this study, the influence of the structural and textural states of industrially produced API-5L X70-X80 pipeline steels on tensile mechanical properties was analyzed. TMCP routes with different hot rolling temperatures and cooling rates were employed. The texture of steel was assessed using the Taylor factor, which was calculated based on electron backscatter diffraction (EBSD). The decrease in rolling temperature resulted in the sharper texture characterized by {001} planes banding (cleavage planes in the bcc lattice) parallel to rolling direction. The tensile deformation behavior at the stage of necking was determined by the crystallographic and morphological texture of the material and demonstrated significant anisotropy. Rupture of all investigated samples was accompanied by the development of splitting on the fracture surface. The splitting was localized in the rolling plane similar to the splitting in standard Charpy tests of pipeline steels. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This research was funded by Russian Science Foundation, grant number 22-29-00411