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

Effect of Structure and Texture on Failure of Pipe Steel Sheets produced by TMCP

The method of orientation microscopy (EBSD) is used to study the structure and texture of low-carbon, low-alloy pipe steel sheets processed by controlled thermomechanical processing (TMCP). The temperatures of isothermal hot rolling varied. Samples cut from sheets showed a different fracture tendency during mechanical testing. The formation of cleavages (secondary cracks) during failure of steel is related to the presence of ferrite grains with orientation {001} <110> extended in the hot rolling direction. The formation of grains is a consequence of the isothermal hot rolling below the temperature

Evolution of the texture of low-carbon microalloyed pipe steel in the seamless pipe manufacturing process

A method of orientation microscopy (with the application of the EBSD technique) is used in investigation of the microstructure and texture in steel 0.08 % C-Cr-Mo-V formed at different stages of the seamless pipe manufacturing process, namely, after hot finishing and after full quenching with subsequent high-temperature tempering. It is shown that, at the final stage of hot finishing followed by heat treatment, the texture is represented by four scattered orientations. The found texture inheritance in the investigated material is presumably related to reproduction of special circa Σ3 boundaries between crystal grains at each phase transition. © 2016 Author(s)

Evolution of microstructure in stainless martensitic steel for seamless tubing

Scanning electron microscopy with orientation analysis by the electron backscatter diffraction (EBSD) method is used to study microstructures and textures formed in the 0.08C-13Cr-3Ni-Mo-V-Nb steel through seamless tube production route: after hot deformation by extrusion; after quenching from various temperatures and subsequent high tempering. It is shown that the martensitic microstructure formed both after hot deformation and after quenching is characterized by the presence of deformation crystallographic texture, which is predetermined by the texture of austenite. The effect of heat treatment on texture, packet refinement, lath width, precipitation of carbides and Charpy impact energy is analyzed. © 2017 Author(s).The work was done using the equipment of the laboratory of Structural Methods of Analysis and Properties of materials and nanomaterials of the Collective Use Center affiliated to Ural Federal University. The study was supported by the program of increasing the competitiveness of the leading Russian universities, RF Government resolution No. 211, contract No. 02.А03.21.0006. We are grateful to the TMK company for their support and assistance in organizing the study

Texture and structure formation of low-carbon low-alloy pipe steel after TMCP and heat treatment

The structure and texture of low-carbon low-alloy pipe steel after Thermo-Mechanical Controlled Processing (TMCP) and subsequent isothermal quenching were studied by the method of Electron Backscatter Diffraction (EBSD) analysis. The texture, obtained after TMCP, was formed mainly by two strong scattered orientations from {112} and two weaker scattered orientations from {110} and one weak orientation (001)[110]. Complex multicomponent textures were observed after heat treatment. The regions with "ferrite" and martensitic structures were identified and analyzed using Oxford Instruments HKL software. Orientations, constituting textures for both selected areas types, are associated with the basic orientations of the initial deformed austenite grains, formed during the hot deformation by orientation relationships (OR), transitory between Kurdjumov-Sachs OR and Nishiyami-Wasserman OR. © 2019 IOP Publishing Ltd. All rights reserved

Features of shear transformation texture in seamless pipes

Microstructure and texture in seamless 0.08C-Cr-Mo-V, 0.25C-Cr-Mo-V-Nb, 0.08-13Cr-3Ni-Mo-V-Nb, and 18Cr-9Ni steel pipes are studied in the as-rolled and heat-treated states using orientation EBSD microscopy. It has been found that all types of microstructure (ferrite, martensite, and bainite) in products, both after hot rolling and after heat treatment, have well-defined axial crystallographic texture, where the direction is predominately perpendicular to the pipe surface. It is demonstrated that texture formation in heat-treated states is inherited due to the following factors important for the rules of orientation selection during the γ→α phase transformation: 1) occurrence of stable orientation of austenite grains resulted from straining; 2) special misorientation (boundaries) of austenite grains where transformation starts; 3) orientation relationships known for phase transformation; 4) thermal stresses in a product, formed during cooling. The latter can be considered as factor determining special texture in seamless steel pipes. © 2018 Author(s)

Features of microstructure, phase composition and strengthening capability of stainless steels with 13 – 17 % Cr

The paper considers the study of the features of structure and phase transformations in high-strength, resistant to carbon dioxide corrosion, complex alloyed steels of martensitic, austenitic-martensitic and martensitic-ferritic classes with 13 – 17 % Cr. Influence of the alloying on crystallization and solid state phase transformations was revealed in the temperature range of hot deformation and heat treatment using thermodynamic modeling and experimental study. The effect of quenching temperature on the phase composition and microstructure was analyzed as a result of X-ray diffraction phase analysis, optical and transmission electron microscopy. It was found that increase of nickel content leads to growth of retained austenite fraction resulting in significant decrease of yield strength along with high tensile strength and elongation. To obtain predominantly martensitic microstructure in martensitic-austenitic steel, the multistage heat treatment is proposed including quenching, intermediate annealing for precipitation of dispersed carbides and tempering forming final mechanical properties. The composition of precipitated carbides was evaluated by X-ray microanalysis. The results of the tensile test for steels with martensitic and martensitic-ferritic microstructure showed that required strength grade (σ0.65 ≥ 862 MPa; σв ≥ 931 MPa) was reached after heat treatment including quenching and tempering. Multistage heat treatment including quenching, intermediate annealing and final tempering was resulted in required strength properties of high-nickel martensitic-austenitic steel with 15 % Cr. © 2022 National University of Science and Technology MISIS. All rights reserved.Ural Federal University, UrFUThe authors express their gratitude to Khatkevich V.M. and Arsenkin A.M. for assistance in electron microscopy analysis (LLC “TMK STC”), as well as Mikhailov S.B. for assistance in conducting a dilatometric study (UrFU)

ADDITIONAL ALLOYING AND HEAT TREATMENT INFLUENCE ON THE PHASE COMPOSITION AND PROPERTIES OF CORROSION-RESISTANT STEEL TYPE 15-17Cr

Исследовано влияние легирующих элементов и режимов термической обработки на фазовый состав и твердость коррозионностойкой стали типа 15-17Cr. Для опытной стали проведено моделирование фазовых равновесий с помощью программного обеспечения Thermo-Calc с целью определения температурных интервалов существования фаз при равновесной кристаллизации. Измерение твердости проводили на образцах после нагрева под закалку до температур 900 – 1050 ℃ и отпуска при температурах 440 – 680 ℃. Выявлена сопоставимость результатов моделирования результатам измерения твердости исследуемой стали.The work shows the study results of the alloying elements and heat treatment modes influence on the phase composition and hardness of corrosion-resistant steel type 15-17Cr. Hardness measurements were carried out on samples that were in a hardened state after heating for quenching to temperatures of 900 - 1050 ℃ and in a state after tempering at temperatures of 440 - 680 ℃. For experimental steel, phase equilibria were simulated using Thermo-Calc software in order to determine the temperature ranges for the phases during equilibrium crystallization existence. The modeling results with the measuring the hardness results of the steel under study comparability was revealed