Perlitic Steel Research Articles

Peculiarities of nucleation of pores in welded metal connections from heat-resistant steels working in creep conditions

Problem. It is necessary to study the relationship of the structure of welded joints with the development of porosity to further obtain such structure, which is characterized by increased resistance to vapor formation. Goal. Study of the peculiarities of nulceation of pores in the metal of welded joints from heat-resistant perlite steels operating in creep conditions to reduce the intensity of pore formation. Methodology. The structure of the metal of welded joints was studied using a macrostructural, microstructural, electron-microscopic, micro-X-spectral and radiographic method. The process of formation of micropores and microcracks was carried out by using electron and light microscopy. Carbide phases were studied by analysis of precipitation using the method of photometry. Results. It was found that creep at welded joints above 270000ch are initially born at the grain limit α – phase – coagulation carbide, and that the pore size of 0.03-0.07 μm, can be considered critical, which is confirmed by an intense increase in their size when working welded joints above 270000. Originality The formation of micropores in heat-resistant pearl steels, during long-term operation in creep conditions, is due to the compatible course of diffusion and deformation processes. Such processes in welded joints are due to their much greater structural heterogeneity. Practical value. In the practical plane, the task is to slow down the processes of deformation and diffusion in both steels and welded joints — by obtaining an initial structure with improved qualitative characteristics.

The Role of Metastable Austenite for Improving Abrasion Wear Resistance of 150KhNML Perlite Steel

The Role of Metastable Austenite for Improving Abrasion Wear Resistance of 150KhNML Perlite Steel

The Effect of Austenization and Isothermal Soaking Temperatures on the Wear of Perlite Steel

The authors have studied grade R260 rail steel after austenization in the temperature range from 800 to 930°C and isothermal soaking at 500, 550, and 600°C followed by quenching in water. The steel structure and abrasive wear resistance were characterized. Recommendations concerning an increase in steel wear resistance were provided.

Optimization of perlite steels mechanical properties for car fasteners stamping

The car fasteners made of pearlitic steels by cold stamping method are to meet special requirements for their structural and mechanical characteristics.The hardware is made of hot-rolled steel, which cannot be used straight after the delivery for fasteners manufacturing due to the poor quality of the structure and surface layer. Therefore, calibrated rolled stock gets heat treatment before drawing. In addition, hardware of strength class 8.8 and higher obtained from alloy steels using cold heading machines are subjected to temper hardening, which often leads to surface decarburization, cracking and distortion of finished products, that afflicts labor and energy efficiency, and, thus, the final cost of production.The article suggests a method for 35X and 38XA pearlitic steels stock treatment excluding recrystallization annealing, rod-like items temper hardening, and including isothermal operation to prevent decarburization, risks and distortion. Passing through the die, hardening the surface due to volume strain and thread rolling impart to M8 bolts and studs the mechanical properties corresponding to strength grades 8.8 and 9.8.This study also has practical application, it allows manufacturers to determine the appropriate mode for producing automotive fasteners.

Layered patterns in nature, medicine, and materials: quantifying anisotropic structures and cyclicity.

Various natural patterns—such as terrestrial sand dune ripples, lamellae in vertebrate bones, growth increments in fish scales and corals, aortas and lamellar corpuscles in humans and animals—comprise layers of different thicknesses and lengths. Microstructures in manmade materials—such as alloys, perlite steels, polymers, ceramics, and ripples induced by laser on the surface of graphen—also exhibit layered structures. These layered patterns form a record of internal and external factors regulating pattern formation in their various systems, making it potentially possible to recognize and identify in their incremental sequences trends, periodicities, and events in the formation history of these systems. The morphology of layered systems plays a vital role in developing new materials and in biomimetic research. The structures and sizes of these two-dimensional (2D) patterns are characteristically anisotropic: That is, the number of layers and their absolute thicknesses vary significantly in different directions. The present work develops a method to quantify the morphological characteristics of 2D layered patterns that accounts for anisotropy in the object of study. To reach this goal, we use Boolean functions and an N-partite graph to formalize layer structure and thickness across a 2D plane and to construct charts of (1) “layer thickness vs. layer number” and (2) “layer area vs. layer number.” We present a parameter disorder of layer structure (DStr) to describe the deviation of a study object’s anisotropic structure from an isotropic analog and illustrate that charts and DStr could be used as local and global morphological characteristics describing various layered systems such as images of, for example, geological, atmospheric, medical, materials, forensic, plants, and animals. Suggested future experiments could lead to new insights into layered pattern formation.

Computer method of processing of deformed steel wire microstructures images for its properties analysis

Mechanical properties of board-bronzed wire depend from one side on the wire rod microstructure from which it is produced and from the other side – determines by peculiarities by the microstructure of the wire itself. At present, there are no generally accepted methods of deformed wire microstructure analysis allowing establishing relationship between characteristics of wire deformation and microstructure characteristics. A mathematical apparatus and new algorithm for processing of microstructure of pearlite steel wire after drawing elaborated based on microstructure image processing and its parameterization. As the main parameter of microstructure, the density function of statistical distribution of fiber lengths used, which allows characterizing quantitatively image of microstructure. Based on the experimental data of OJSC “BMZ – management company of “Byelorussian metallurgical company” holding” correlation demonstrated between degree of wire twisting and degree of delamination. On the basis of samples of perlite steel and their images obtained for bronzed bead wire manufactured at OJSC “BMZ – management company of “Byelorussian metallurgical company” holding” density functions of statistical distribution of perlite microstructure fiber length for the group of samples calculated. Criteria for wire microstructure analysis, based on density distribution function along length of fibers, as well as reduced distribution function proposed. Correlation between degree of delamination, number of wire twists and characteristics of its microstructure determined, calculated using the distribution function of wire fibrous structure with pronounced texture in the cross section.

Charpy impact toughness and transition temperature in ferrite–perlite steel

Las pruebas de impacto son una importante herramienta para la obtención de importantes propiedades, como la tenacidad al impacto y la temperatura de transición ductil-fragil, para la selección de un material en diseño mecánico. Se evaluó la tenacidad al impacto mediante pruebas de impacto Charpy en acero de fase doble (ferrita-perlita) de 10 mm de espesor a temperaturas que oscilan entre 90 ºC y -60 ºC. Las superficies de fractura fueron analizadas por microscopio óptico (MO). Debido a la alta dispersión, mostrada en los resultados, se emplaron numerosas pruebas en las mismas condiciones y el uso de métodos estadísticos para obtener un valor confiable. La temperatura de transición calculada (45 ºC) y la resistencia al impacto de Charpy se analizaron en función de la microestructura y el equivalente de carbono

Кавітаційно-ерозійна зносостійкість вуглецевих конструкційних сталей

In the paper, based on the analysis of literary sources and own researches of authors, the results of cavitation and erosion wear resistance of structural steels are systematized depending on their thermal processing (structure) and type of environment.The structural structure of steels is based on the analysis of wear resistance during cavitation and erosion fracture of surfaces, and the mechanisms of cavitation fracture of dodectoid, zavectotoid and perlite steels are considered.Destruction of dodectoid steels begins with ferrite, and then extends to perlite grains. The wear resistance of the pearlite grains of the plate-shaped form is higher than that of perlite of the granular form. Cavitation wear resistance of zeutectoid steels is determined mainly by the properties of perlite. The mechanical properties of which depend on the dispersion and shape of the particles of cementite.In perlite steels, reducing the size of its grain increases their erosion resistance, especially in the presence of cementite in the structure of the grid, and not ferrite grids.Using different types of thermal and thermocyclic heat treatment, it is possible to form appropriate structures and, accordingly, increase the cavitation and erosion wear resistance.

Improvement of Corrosion Resistance of Dissimilar Welded Joints in VVER Secondary Circuit

This article presents experimental program, focused on extending lifetime and operation reliability of dissimilar welded joints of austenitic and perlite steel in conditions of secondary circuit media of water–water power reactor (VVER) unit. The main purpose of this experimental program is to bring new possibilities of corrosion protection of dissimilar welded joints, which are threatened by corrosion and degradation processes. These degradation processes significantly affect their service life. Suitability and corrosion behavior of thermal-sprayed coatings were tested.

Mathematical Description of the Microstructural Modifications and Changes in the Mechanical Properties during Spheroidization of Medium‐Carbon Steel

A set of experiments is carried out to clarify the microstructure development during an intercritical spheroidization process in AISI 1045 ferritic–perlitic steel, as well as its structure‐property relationships at room temperature. Microstructures with a distinctive combination of fine spheroidized carbide particles within a ferrite matrix are created through different heat‐treatment combinations. The validation and evaluation of the accuracy of the spheroidizing kinetics and particle coarsening, as well as the prediction of tensile properties of the investigated material, are carried out based on the common empirical and empirical‐physical models. Some of the models are then adapted for the material. Quantitative analyses reveals that not all of the model‐based predictions correlate well with the experimental measurements. Such instances are associated with the peculiarities of the investigated material.

ВЛИЯНИЕ ТЕРМИЧЕСКОЙ ОБРАБОТКИ НА СТРУКТУРУ И ИЗНОСОСТОЙКОСТЬ СТАЛЕЙ ПЕРЛИТНОГО КЛАССА

From the ecological point of view, high-manganese austenitic steels of 110G13L type are undesirable in the production because of the high emission of manganese oxides to the atmosphere while melting in the electric arc furnaces, gas-oxygen cutting, and welding operations. Another disadvantage of steels of this class is their low initial hardness, which causes the revet closing capacity of the working parts of castings under the conditions of dynamic loads. Moreover, these steels are poorly machinable. The paper presents the results of the comparative study of the relationship between the structure formed in the process of heat treatment and the abrasive wear resistance of steels of two structural classes - high-manganese austenitic 110G13L steel and the 70H2GSML perlite-class steel. The wide use of 110G13L steel for the production of parts operating under the impact-abrasive wear and the repetitive contact-impact force is caused by the ability for high friction hardening of stable manganese austenite with low energy of packaging defects combined with the good impact strength. The disadvantages of 110G13L steel are the high quenching temperature, poor environmental performance and economic reasons that make it necessary in some cases to replace it with the perlite steels. The study of wear resistance of 70H2GSML perlite-class steel depending on the tempering temperature after normalization showed that this steel could be used for the casting of replaceable cast parts for crushing-milling equipment operating under the abrasive action without significant impact loads after normalization and high tempering. The wear resistance of samples made of 70H2GSML steel with the secondary sorbite structure, when testing steady abrasive, makes 55-60 % of level provided by samples of 110G13L steel, however, the lower cost, manufacturability and the environmental problems in some cases can settle the issue in favor of the application of perlite steel. The additional reserves to increase the wear resistance of 70H2GSML steel involve the quenching at high temperatures due to the formation of the structure of retained austenite that, in the process of abrasive wear, transforms into deformation martensite on the working surface increasing the steel’s friction hardening ability.

Modeling and Simulation of the Microstructure Evolution of 42CrMo4 Steel During Electrochemical Machining

Machining independently of mechanical material properties like hardness or high temperature strength is one mayor advantage of the electrochemical machining process (ECM). Additionally, high material removal rates can be achieved in combination with best surface integrities. Nevertheless, one limiting factor in the resulting surface integrity can be a significantly varying dissolution rate of material phases in a multi phase material during ECM. These differences in the dissolution rates determine the surface topography as well as the achievable surface roughness. However, this behavior cannot be forecasted up to now.For that reason, this paper presents a model for the prediction of the microstructure evolution as well as simulation results regarding the influence of the electrochemical machining process on resulting surface topography for the ferritic perlitic steel 42CrMo4 in a passivating electrolyte system. With the help of the model, the evolution of surface topography can be predicted and will be analyzed for different process parameters and various initial microstructures.

Investigation of Creep Processes and Microdamages in 10Kh9V2MFBR-Sh High-Chromium Steel

During the modernization and the new construction of power units at TPPs in Russia, high-chromium martensitic steels with higher heat-resistant properties than the traditional perlite steels are increasingly used as structural materials. High-chromium steels have a necessary regulatory support for their use in domestic power engineering. However, up to the present time, the issue of assessing the quality of these steels at the analysis of their state during long-term operation remains open. The article proposed is one of the first attempts to create a system of quality criteria for martensitic steels based on their microdamage parameters. Tests were carried out on the long-term strength and creep of samples from 10Kh9V2MFBR-Sh steel at high temperatures with the construction of creep curves in relative coordinates “deformation related to the deformation of fracture, current time related to time to failure.” For some samples, the tests were interrupted and the metal was subjected to metallographic studies consisting of the analysis of microdamage with reference to the accumulated creep strain. It has been shown experimentally that the deformation curve of high-chromium steel differs from the analogous curve of pearlitic steel by a longer and flat section of steady creep and by a sharper transition to the third accelerated creep stage, which has a very short time period (approximately 10% of the total durability). The tendency to the increase in the microdamage of the structure of steel as the accumulated creep strain increases with time was confirmed. The beginning of transition to the final creep phase is characterized by the formation of contours of future pore chains and by the appearance of individual large pores of up to 6 μm in size, the presence of which in the microstructure of the martensitic steel indicates a very significant accumulation of creep strain, and corresponds to the predestruction stage of metal. It is necessary to continue the research to obtain quantitative indicators on the accumulation of microdamage in high-chromium steel in a conjunction with the development of a metal resource under creep conditions.

Effect of heat treatment on microstructure and residual stress fields of a weld multilayer austenitic steel clad

Samples of ferritic–perlitic steel were cladded by submerged arc welding with three layers of two austenitic stainless steel filler metals. After the weld cladding, samples were submitted to stress relief heat treatment (SRHT) under different parameters. The characterization of the microstructure of the samples was made by optical and scanning electron microscopy, and the residual stresses determined by X-ray diffraction and incremental hole drilling method. The results were compared and related to the SRHT conditions. The microstructure of the third layer of the as-welded clad consists of cellular austenite and intercellular eutectic delta-ferrite particles, while the microstructure of the first layer presents a high proportion of lathy martensite in γ-Fe cells. The second layer contains a low proportion of martensite and high proportion of austenite. The SRHTs induced partial decomposition of delta-ferrite in the superficial layer, increasing the rate of decomposition with the treatment temperature, and the coarsening of precipitates in the vicinity of the interface carbon steel–stainless steel. The superficial layer of the as-welded and machined clad plate presented residual compressive stresses. The SRHT at 540°C, for 10h of holding time, enabled some residual stress relaxation, unlike the treatment at 620°C, during 1h, which increased the compressive stresses.

Deformation textures in wire drawn perlitic steel

In this study, we followed the deformation microstructure and texture evolution during the cold wire drawing of a perlitic steel wire intended for civil engineering applications. The deformation level effect on the microstructure evolution and on the texture evolution is characterized. Wire drawing induces the lengthening of the perlitic grains along the drawing axis and leads to a strong hardness increase. X-ray texture measurements were performed. The reference state (initial wire) revealed an isotropic texture. The quantitative analysis show the development of the α fibre ( //ND (ND // wire) with the deformation. Moreover, the {001} orientation (rotated Cube) is also present. The experimental techniques used in this study are the: Optical Microscopy (OM), the Electron Back Scattered Diffraction (EBSD), the X-ray diffraction, the Neutron diffraction and the Vickers microhardness.

The Multi-Scale FEM Simulation of Wire Fracture during Drawing of Perlitic Steel

The fracture development during wire drawing operation is an important phenomenon governing the productivity as well as the mechanical properties of the drawn wire. The wire drawing processes was investigated in present paper in two separate levels - using the 2-dimensional rigid-plastic finite element method (macro-level) and modelling the microstructure changes (micro-level) by the Representative Volume Elements (RVEs). To predict fracture initiation the phenomenological theory of fracture is used. The influence of initial cementite lamellas orientation on triaxity factor and localization of deformation in micro-level is investigated. Obtained results are helpful for a fundamental understanding of pearlitic deformation during development of high strength steel wires for tire cord applications.

超高強度パーライト線の引張応力下における格子面ひずみの飛行時間法中性子回折その場測定(オーガナイズドセッション,材料と組織)

Work hardening of perlitic steel is governed by the stress partitioning between ferrite(α) and cementite (θ) during deformation. However by heavily drawn processing, cementite dissolves to disappear. Hence, the strength of heavily drawn processed pearlitic steel originates in a matrix. In this paper, a pearlitic steel wire with ultra-high strength was studied by in situ time-of-flight diffraction during tensile deformation. Lattice plane strains for various (hkl) planes were measured in the tensile and the perpendicular directions simultaneously.

Sorption and Desorption of Radionuclides on the Structural Materials of a Nuclear Power System as Applied to Nuclear Power Plants with RBMK Reactors during Shutdown

The sorption and desorption of radionuclides on structural materials are studied as a function of the content of corrosion-activating ions, oxygen, hydrogen peroxide, and corrosion inhibitors in water. The strongest desorption is observed in aerated water containing chloride ions and the weakest desorption in a deaerated medium. The amount of desorbed radionuclides is correlated with the rate of corrosion of metals – it is highest on perlite steel (No. 20 steel) and lowest on zirconium alloys. Anode inhibitors prevent the corrosion of steel and transfer of radionuclides into the coolant. The sorption of radionuclides depends on the sample material. The highest sorption is observed on perlite steel and the lowest on zirconium alloy. Adding an inhibitor to the contaminating solution counteracts the effect of sorption, depending on the type of the structural material and radionuclide, and decreases it manyfold.

On the fatigue limit of ductile metals under complex multiaxial loading

The classical strength hypotheses are not applicable for the calculation of the fatigue limit under multiaxial loading with changing directions of the principal stresses. Hitherto, two groups of concepts have been proposed, the critical plane approach and the integral approach. In the present paper it is shown that with the integral approach, in particular the Shear Stress Intensity Hypothesis SIH, a good estimation can be achieved with complex periodical loads. This is verified using the results of 179 test series with ferritic and ferritic perlitic steel with a range of the tensile strength of R m=400–1600 MPa. References will be given to further hypotheses and developments.

Change of steels and alloys structure and properties during long operation at high temperature

When defining the stress-strain state (SSS) and evaluating safety factors for turbomashinery components operating at high temperatures under creep conditions, deformation and fracture characteristics obtained during tests of as-heat-treated materials are usually used. At the same time, if the change in material properties during long - term service is taken into account, then the SSS of companents and, consequently, the real safety factors can significantly differ from design values which have been calculated without accounting for these changes. In this report the changes in material structure and deformation characteristics, stress-rupture and creep-rupture properties, and thermal fatigue for a number of materials of different types (perlitic and austenitic steel, nickel-base alloys) are analyzed based on the results of long-standing studies were performed for the materials both in the original state and after long-term aging (to 10000 hour and in some cases up to 50.0000 hour and up) at high temperature (400-900 °C). The greatest changes in properties were found for 20Ch23N18 austenitic steel and EP99 nickel-base alloy (22%Cr) after long-term aging, resulting in topologically close-packed o- and μ-phases precipitations. Thus, EP99 alloy plasticity is decreased to about zero at 20 °C, number of cycles to failure is hundred times reduced thermal fatigue tests. The rate of creep for 20Ch23N18 steel 20X23H18 is 150 times increased.