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Plasticity Origin of Heterophase Inclusions at Steel Forming
... плавлення нижче, ніж у тугоплавких фаз включень, а пластичність вище [1,2,4]. ...
The nature and level of plasticity of microcomposite heterophase inclusions in steels under pressure treatment condition was investigated. Plastic phases in heterophase inclusions of various types under the conditions of hot and cold deformation of steels were investigated. It is shown that each type of inclusions, which are microcomposite formations in steels, is characterized by its own laws of the development of deformation processes, which are determined by their chemical and phase composition, structure, deformation capacity of inclusion phases. The generalized of the plastic behavior of heterophase inclusions of various types with a complex structure have been established and inhibitory effect of non-deformable inclusion phases on the behavior of plastic phases in a wide range of deformation temperatures of steels has been established. The peculiarities of the nature of plasticity of heterophase inclusions with different compositions and structures are discussed. The use of the obtained results will make it possible to develop technologies for obtaining steels with a regulated content and types of heterophase non-metallic inclusions, which will significantly increase their technological plasticity, as well as prevent the formation of various types of defects during pressure treatment of steels.
... The remaining free oxygen in the steel is mostly com-bined with alloying elements to form oxide inclusions, which exist in the form of bound oxygen [21]. However, due to the different deformation capabilities of various oxide inclusions in steel and their significant differences, cracks are prone to occur during the rolling process, leading to reduced plasticity and impact toughness of the steel [22][23][24][25]. Large-sized oxide inclusions also have a negative impact on the fatigue life of the steel [26][27][28]. ...
In the long traditional process of steelmaking, excess oxygen is blown into the converter, and alloying elements are used for deoxidation. This inevitably results in excessive deoxidation of products remaining within the steel liquid, affecting the cleanliness of the steel. With the increasing requirements for steel performance, reducing the oxygen content in the steel liquid and ensuring its high cleanliness is necessary. After more than a hundred years of development, the total oxygen content in steel has been reduced from approximately 100 × 10−6 to approximately 10 × 10−6, and it can be controlled below 5 × 10−6 in some steel grades. A relatively stable and mature deoxidation technology has been formed, but further reducing the oxygen content in steel is no longer significant for improving steel quality. Our research team developed a deoxidation technology for bearing steel by optimizing the entire conventional process. The technology combines silicon–manganese predeoxidation, ladle furnace diffusion deoxidation, and vacuum final deoxidation. We successfully conducted industrial experiments and produced interstitial-free steel with natural decarbonization predeoxidation. Non-aluminum deoxidation was found to control the oxygen content in bearing steel to between 4 × 10−6 and 8 × 10−6, altering the type of inclusions, eliminating large particle Ds-type inclusions, improving the flowability of the steel liquid, and deriving a higher fatigue life. The natural decarbonization predeoxidation of interstitial-free steel reduced aluminum consumption and production costs and significantly improved the quality of cast billets.
Purpose. The goal of the work was to study the peculiarities of crack nucleation in heterophase inclusions of the “eutectic inclusion − matrix” type during steel deformation. Methods. The research was carried out after deformation of samples from steels 08Yu, 12GS, 08kp, 09G2S, NB-57, 08GSYUTF in the temperature range of 20…1 200 °C with the speed of movement of grips 1 680 mm/min. The research methods were used − petrography, micro-X-ray spectral analysis (Cameca MS-4, Nanolab-7), optical microscopy (Neophot-21). Results. It is established that the variety of phases that make up heterophase inclusions of the type “eutectic of inclusion − matrix” leads to their different behavior under conditions of plastic deformation. It is shown that the nucleation of brittle or viscous microcracks occurs along the internal interfacial boundaries between the metal matrix and the second phase of the eutectic. It is determined that the nature of cracks is determined by the level of plasticity of the inclusion phases and the deformation temperature. It is shown that the critical degrees of deformation of the samples, at the achievement of which there were noticeable microcracks along the internal interfacial boundaries, depend on the temperature and nature of the phases of inclusions “eutectic of inclusion − matrix”. It is established that the values of critical degrees of deformation determine the level of cohesive strength of the internal interfacial boundaries in heterophase inclusions “inclusion − matrix eutectic”. Scientific novelty. Peculiarities of microcracking nucleation in heterophase inclusions of the “inclusion − matrix eutectic” type have been established. It is shown that the nature of microcracks formed along the interfacial boundaries depends on the temperature, level of plasticity and conditions of combination of brittle and plastic phases in inclusions of the “eutectic of inclusion − matrix” type, as well as on the deformation temperature. It is shown that the critical degrees of deformation of steels, when microcracks occurred along the inner interfacial boundaries, determine the cohesive strength of these boundaries and depend on the temperature and nature of the phases of inclusions such as “inclusion − matrix eutectic”. Practical significance. The use of the results obtained will make it possible to develop technologies for producing steels with regulated types of heterophase nonmetallic inclusions, which will significantly increase their technological and operational characteristics, as well as prevent the formation of various kinds of defects during the processing of steels by pressure and the operation of products.
Peculiarities of the shape change and redistribution of non-metallic inclusions of various types during working by pressure of steels (rolling, forging, drawing) were investigated. The concept of plastic deformation of inclusions is considered from the standpoint of physical mesomechanics of heterophase alloys. It is shown that non-metallic inclusions contribute to the localization of plastic deformation, which is accompanied by the interaction of non-metallic inclusions and the steel matrix, which determines their common plastic change in shape and redistribution of inclusions in the steel matrix. The peculiarities of these processes under different types and temperature regimes of working by pressure, which determines the nature of stresses near the inclusions and the plastic flow of the steel matrix, have been established. It is shown that the temperature regime of pressure treatment determines the possibility of relaxation processes in the steel matrix near the inclusions and the level of plasticity of the inclusions themselves and the inclusion-matrix interphase boundaries. The influence of the temperature regime of hot deformation of sheet steels and wire rod on the nature of shape change and the deformability of plastic inclusions and their destruction (brittle or ductile), as well as the plasticity of the steel matrix, frictional forces at the inclusion-matrix boundaries, and the plasticity of the latter during hot rolling were established. It is shown that when considering the plastic behavior of non-metallic inclusions in a plastic steel matrix, the behavior of the inclusion-matrix interphase boundaries under different deformation conditions is of great importance. Peculiarities of the dynamic character of the joint deformation of the inclusion-matrix system, which is associated with the development of competing processes at the interphase boundaries of the inclusion-matrix: interphase friction and slipping, have been studied. The features of hot and cold slipping occurring at different deformation temperatures are discussed. It is shown that the mechanisms of each of the mentioned processes depend on the temperature regime of the deformation, the level of plasticity of the inclusions and the steel matrix. The influence of the method of cold deformation (rolling and drawing) on the shape change of plastic inclusions and the redistribution of non-deformable inclusions in the steel matrix was established. The processes that determine the level of plasticity of non-metallic inclusions and inclusion-matrix boundaries and significantly affect the nature of the shape change of inclusions and their redistribution in the steel matrix in the process of the working by pressure of steels, which affect their technological plasticity at different temperatures and methods of deformation, are considered.
The purpose of the article − to study of crack nucleation features in heterophase inclusions of the “eutectic of inclusion-matrix” type during steel deformation. Methods. The research was conducted after deformation for a number of different grades steel samples in the temperature range of 20...1 200 °С on Instron-1195 and IMASH-5C with special grippers, with a gripper movement speed of 1 680 mm/min. Research methods were used: petrography, micro-X-ray spectral analysis (Cameca MS-4, Nanolab-7), optical microscopy (Neophot-21). Results. It is found that the variety of phases composing the heterophase inclusions of the "eutectic of inclusion-matrix" type leads to their different behaviour under conditions of plastic deformation. It is shown that the nucleation of brittle or viscous microcracks occurs along the internal interfacial boundaries between the metal matrix and the second phase of the eutectic. It is defined that the cracks’ nature is determined by the plasticity level of the inclusion phases and the deformation temperature. It is shown that the critical degrees of samples’ deformation, at which appreciable microcracks along the internal interphase boundaries appeared, depend on the temperature and the nature of the inclusion phase “eutectic of inclusion – matrix”. It is found that the values of deformation critical degrees determine the level of cohesive strength for internal interphase boundaries in heterophase inclusions “eutectic of inclusion – matrix”. Scientific novelty. The features of microcracks nucleation in heterophase inclusions of the “eutectic of inclusion − matrix” type are determined. It is shown that the nature of the microcracks formed along the interphase boundaries depends on the temperature, plasticity level and combination conditions of brittle and plastic phases in inclusions of the “eutectic of inclusion − matrix” type as well as on the deformation temperature. It is shown that the critical degrees of steels deformation, when microcracks appeared along the internal interphase boundaries, determine the cohesive strength of these boundaries and depend on the temperature and the nature of the inclusion phase “eutectic of inclusion − matrix” type. Practical value. The use of the obtained results will make it possible to develop technologies for producing steels with regulated types of non-metallic heterophase inclusions that will allow to increase considerably their technological and operational characteristics, and also to prevent the formation of various defects during steel pressure treatment and product operation.
Purpose of research. Investigation into crack initiation features in heterophase inclusions of the “phase side by side” type during steel deformation. Methods. Destruction of various types heterophase inclusions is investigated during the deformation of samples from steels 08Ti, 08Al, 12MnSi, 08unk, 09Mn2Si, 08GSiAlTiV in the temperature range 20...1 200 °С. Samples of 08Ti and 08Al steels are subjected to tension, compression and bending, steel HB-57 − to tension and compression, steel 08unk, 08Cr, ATs45X ,ATs18XGT − to tension in vacuum at temperatures of 20...1 200 °С on experimental settings with special grips, which motion speed was 20 mm/min. Methods of investigation – petrography, X-ray microanalysis and optical microscopy were used. Results. It has been found that the diversity of phases composing the heterophase inclusions of the “phase side by side” type leads to their different behaviour under plastic deformation. The microcracks nitiation occurs along the internal interphase boundaries. Depending on the plasticity level of the phases composing the inclusion, these cracks can be brittle or ductile, which is also related to the effects of the deformation temperature. The features of microcracks initiation for different combinations of heterophase inclusions plastic and non-deformed phases of the “phase side by side” type are analysed. The interaction between heterophase inclusions of the “phase side by side” type and the steel matrix during deformation is discussed. Scientific novelty. The features of microcrack initiation related to heterophase inclusions of “phase side by side” type with different combination of brittle and plastic phases during steels deformation in a wide temperature range is determined. It was found that the microcracks initiation and spreading within inclusions “phase side by side” type occurs both in phases and along internal interphase boundaries. It is shown that the critical degrees of samples deformation, at which significant microcracks along the internal interphase boundaries occur, depend on the temperature and the inclusion phase. The critical degrees of samples deformation, upon reaching which significant microcracks occurred along the internal interphase boundaries, depended on the temperature and the nature of the “phase side by side” inclusions. The values of the critical degrees of deformation determine the level of cohesive strength of the internal interphase boundaries of the heterophase inclusions “phase side by side”. Practical significance. The use of obtained results will make it possible to develop technologies for producing steels with regulated types of heterophase non-metallic inclusions. This will substantially improve their technological and performance characteristics and prevent the various defects formation in the steel pressure treatment and the products operation.
The purpose of the article − to study of crack nucleation features in heterophase inclusions of the “dispersed phases in a non-metallic matrix” type under the conditions of steels’ plastic deformation. Methods. The research was conducted after deformation for a number of different grades steel samples in the temperature range of 20...1 200 °С on Instron-1195 and IMASH-5C with special grippers, with a gripper movement speed of 1 680 mm/min. Research methods were used: petrography, micro-X-ray spectral analysis (Cameca MS-4, Nanolab-7), optical microscopy (Neophot-21). Results. It is shown that the variety of phases composing the heterophase inclusions "dispersed phases in non-metallic matrix" leads to their different behaviour under plastic deformation conditions. At the same time, the nucleation of brittle or viscous microcracks occurs along the internal interphase boundaries between the "non-metallic" matrix and the dispersed particles of the second phase. The cracks’ character near the inclusions determined by the plasticity level of “matri” and dispersed phases of inclusions and the deformation temperature are revealed. The determined critical degrees of samples’ deformation, upon reaching which appreciable microcracks along the internal interphase boundaries occurred, were depend on temperature and the nature of the “dispersed phases in a non-metallic matrix” inclusions. Scientific novelty. The features of microcracks nucleation associated with heterophase inclusions of the “dispersed phases in non-metallic matrix” type with different combination of brittle and plastic phases during steels’ deformation are determined. The types of microcracks occurring in inclusions of the “dispersed phases in the non-metallic matrix” type and the locations of their formation have been determined. It is shown that the values of the deformation critical degrees determine the level of cohesive strength for internal interphase boundaries in heterophase inclusions “dispersed phases in a non-metallic matrix” at different deformation temperatures. Practical value. The use of the obtained results will make it possible to develop technologies for producing steels with regulated types of non-metallic heterophase inclusions that will allow to increase significantly their technological and operational characteristics, and also to prevent the formation of various defects in the steels' treatment by pressure and the operation of products.
Purpose of the work – to study of the processes that determine the interaction of non-metallic inclusions and the steel matrix during steel rolling. Methods. The behavior of inclusions was studied during hot rolling of steels 08Yu, 08T, 08kp, NB-57, 08GSYUTF in the temperature range of 1 200...900 °C and cold rolling with degrees of deformation of 35...75 %. The study of hot slipping along the boundaries of the inclusion − matrix was observed during high-temperature (900...1 200 °C) deformation by stretching in a vacuum on the IMASH-5S installation with a gripper movement speed of 1 680 mm/min. According to the study of slipping, steel samples were stretched in a vacuum at temperatures of 25...900 °С on the IMASH-5S installation with a gripper movement speed of 2 000 mm/min. On the surface of the samples, using the PMT-3 device, reference points were applied near the 0° and 90° inclusion poles on both sides of the inclusion − matrix boundary. Research methods are given in works [10; 11]. Identification of inclusions was carried out by metallographic (Neophot-31), petrographic and micro-X-ray spectral (MS-46 Cameca) methods. Results. It is shown that during plastic deformation, there is an interaction between non-metallic inclusions and the steel matrix, which determines their joint plastic shape change and is associated with the development of competing processes at the inclusion − matrix interphase boundaries: interphase friction and slipping (hot or cold depending on the deformation temperature). The mechanisms of these processes are determined depending on the deformation conditions and the level of plasticity of non-metallic inclusions and the steel matrix. Scientific novelty. The peculiarities of interphase friction and hot and cold slipping along the inclusion − matrix interphase boundaries of steel under different conditions of plastic deformation have been established. It is shown that the mechanisms of each of these processes depend on the temperature regime of deformation, the level of plasticity of the inclusions and the steel matrix, as well as on the structure of the inclusion − matrix boundaries, which determines the possibilities of movement and interaction of interfacial defects. It is shown that the specified processes determine the level of plasticity of the inclusion − matrix boundaries and significantly affect the nature of the change in shape of the inclusions and their redistribution in the steel matrix during steel rolling, which inevitably affects the technological plasticity of steels. Practical significance. The use of the results obtained will make it possible to develop technologies for producing steels with regulated types of nonmetallic inclusions, which will significantly increase their technological characteristics, as well as prevent the formation of various kinds of defects during the processing of steels by pressure of products.
Purpose. To study features of slippage at the interphase boundaries, heterophase inclusion “refractory phase surrounded by a low-melting shell” − steel matrix in the temperature range of hot deformation. Methods. Samples of steels were subjected to stretching at temperatures of 20...1 200 °C in a vacuum on the IMASh-5S device with special grippers, the speed of which was 20 mm/min. Research methods were used: petrography, micro-X-ray spectral analysis (“Cameca MS-46, Nanolab-7”, optical microscopy (Neophot-21). Results. It was found that the diversity of phases composing the heterophase inclusions of the “high-melting phase surrounded by a low-melting shell” type leads to their different behavior under plastic deformation. It was shown that during the high-temperature deformation the inclusion − matrix interphase boundaries, which are the boundaries between the inclusion-shell phase and the steel matrix, exhibit plasticity as a result of slipping. It was found that depending on the plasticity level of the phases composing the inclusion, the slipping occurs with different intensity. The features of the slipping process for heterophase inclusions of the “high-melting phase surrounded by a light-melting shell” type were analyzedScientific novelty. It is discussed the slipping mechanism for inclusions of the “high-melting phase surrounded by a low-melting shell” type containing phases with different plasticity levels, which is associated with the movement of interface dislocations at the inclusion − matrix boundaries (intrinsic slipping) or inserted dislocations as well as with contact friction and internal friction occurring at the boundaries due to the dislocation movement. It is shown that the activation of the slipping can occur due to the rearrangements of defects located at the interphase boundaries of the inclusion − matrix of steel. It was established that the difference in the nature of the phases-shells, as well as the influence of the second phase of inclusions “high-melting phase surrounded by a low-melting shell” contribute to difference in plasticity of inclusion-matrix boundaries of steel under high-temperature deformation. Practical value. The use of the obtained results will make it possible to develop technologies for producing steels with regulated types of heterophase non-metallic inclusions, which will significantly increase their technological and operational characteristics, as well as prevent the formation of various defects during the processing of steels by pressure and the operation of products.
The influence of MnS inclusions on steel properties is highly noticeable. For instance, higher severity levels of inclusions are associated with lower mechanical properties and a higher risk of failure in service. Manual inclusions classification methods are the most used in laboratories and metallurgical sector industries because of their low cost, while automatic methods have high operating costs, which makes their use more restrict. Neural network models, on the other hand, are extremely advantageous for several applications. The present study is motivated by the use of a neural network model for classifying inclusions in steels. The aim is to achieve the highest possible accuracy in classifying the MnS inclusions severities (0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5) using optical images captured from steel specimens. The results have showed that the classification of MnS severities was very sensitive to the database number of images. A 98% training accuracy was obtained by increasing the number of images from 3,156 to 4,136, mostly adding images for some severity levels. However, validation and test results were not satisfactory. As such, a severity re-categorization of the database was able to enhance the true positive values, with an error of 8%. In general, the neural network represented speed in decision making, proving to be a potential tool for classifying steel inclusions.
It is well known that formation of defects of many types during railway wheels service somehow or other is connected to nonmetallic inclusions in wheel steel. Microbreakes connected with nonmetallic inclusions have different origin. The first one is “deformational”, the second is “thermal” and the third is “hydrogenous”. The objective of this work is the study of nature of microbreaking in wheel steel relative to nonmetallics. Mechanisms of microbreaking of all types near different nonmetallics had been investigated and their influence on safety threshold of railway wheels had been analyzed herein.
S. I. Gubenko, “Team dislocation effects or phase transformations in ‘nonmetallic inclusion — matrix’ boundaries in steel,” Fiz. Met. Metalloved., No. 6, 184–188 (1990).
Processes of fracture of steels near non-metallic inclusions were
analysed all-rounly. Peculiarities of inclusions structure as interstitial
phases and their influence on the thermal and deformational stresses
are discussed. It was shown the influence of inclusions nature on the
mechanism of microcracks formation in steels under different
conditions of deformation and also in reactive mediums. Special
attention for development of fracture along interphase inclusionmatrix boundaries was given. Possibilities of rise of steels with nonmetallic inclusions cracking resistance by thermal and deformational
actions are discussed.
Gubenko, S.I., Nemetallicheskie vklyacheniya i prochnost’ stalei/ Fizicheskie osnovy prochnosti stalei (Nonmetallic Inclusions and Strength of Steels. Physical Basis of Steel Strength), Саарбрюкен (Saarbrücken): LAP LAMBERT. Palmarium academic publishing, 2015, 476 р.
On the basis of thermodynamical studies and of the analysis of discrepancy between crystal lattices of matrix and nonmetallic inclusion possible structure of interfaces is under consideration. Analysis of calculated data on lattice discrepancy for a great quantity of oxide and nitride inclusions in austenitic and ferritic matrices permits an assumption about compensation processes proceeding in interphase boundaries. Being an active structural constituent of steels an interphase boundary may be considered as a surface phase.
In high-temperature deformation of steel slippage is observed along the inclusion-matrix interphase boundaries for different types of nonmetallic inclusions. Slippage along inclusion-matrix boundaries causes an increase in crack resistance of the steel at high temperatures.
Influence of slippage along the boundaries of a nonmetallic inclusion-matrix on the distribution of local microinhomogeneous deformation in armcoiron and steel
- S I Gubenko
Microheterogeneous deformation of steel containing non-metallic inclusions
- G I Chenko
- S I Gubenko
Deformation of nonmetallic inclusions during steel rolling
- G I Chenko
- S I Gubenko
Non-Metallic Inclusions in Steel, London: Iron Steel Inst
- R Kiessling
- N Lange
Geterofaznye mikrokompozitnye vklyu-cheniya v stalyakh (Heterophase Microcomposite Inclusions in Steels)
- S I Gubenko
Mezhfaznye granitsy vklyuchenie-matritsa v stalyakh: Mezhfaznye granitsy nemetallicheskoe vklyuchenie-matritsa i svoistva stalei (Interphase Boundaries Inclusion-Matrix in Steels: Interphase Boundaries Nonmetallic Inclusion-Matrix and Properties of Steels)
- S I Gubenko
Types and structure of heterophase inclusions in steels
- S I Gubenko
- V N Ko