Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-768-774
K. Solomonov, L. Tishchuk, S. M. Gorbatyuk, S. Snitko, O. N. Chicheneva
Parts made of the billets with a thin web and stiffeners are manufactured at metallurgical enterprises in special workshops equipped with powerful hydraulic presses. Often their production is accompanied by the defects that worsen the product macrostructure. In this regard, new techniques are relevant that allow modeling the processes of forming of forgings with stiffeners. The processes of metal processing by pressure are difficult to create a mathematical model describing the stress-strain state of plastic forming of metal. One of the ways to solve the problem of modeling the pattern of metal flow and the spatial diagram of contact pressures is the “theory of thin layer flow”, based on assumptions that simplify the initial system of differential equations. Then the problem is reduced to a purely geometric one and can be solved within the framework of the “sandy analogy” using the proposed methodology. The paper presents the results of computer and physical modeling of the forming of stamped forgings with contour stiffeners. The experiment was carried out in industrial conditions on the precipitation of flat billets made of AK6 alloy on a hydraulic press with a deformation force of 150 MN. It is shown that the proposed software package can have a different functional purpose: express analysis of the pattern of metal flow and calculation of the shape of the billet at the stages of its deformation. This allows, by sorting through values of the geometric parameters of the stamp engraving, to obtain different patterns of metal flow and profiles of stiffeners and choose from them those that guarantee the most uniform filling of the stamp cavities with metal under the stiffeners, which ensures defect-free production of the product.
{"title":"Modeling the pattern of metal flow during forming of forgings from a flat billet","authors":"K. Solomonov, L. Tishchuk, S. M. Gorbatyuk, S. Snitko, O. N. Chicheneva","doi":"10.17073/0368-0797-2023-6-768-774","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-768-774","url":null,"abstract":"Parts made of the billets with a thin web and stiffeners are manufactured at metallurgical enterprises in special workshops equipped with powerful hydraulic presses. Often their production is accompanied by the defects that worsen the product macrostructure. In this regard, new techniques are relevant that allow modeling the processes of forming of forgings with stiffeners. The processes of metal processing by pressure are difficult to create a mathematical model describing the stress-strain state of plastic forming of metal. One of the ways to solve the problem of modeling the pattern of metal flow and the spatial diagram of contact pressures is the “theory of thin layer flow”, based on assumptions that simplify the initial system of differential equations. Then the problem is reduced to a purely geometric one and can be solved within the framework of the “sandy analogy” using the proposed methodology. The paper presents the results of computer and physical modeling of the forming of stamped forgings with contour stiffeners. The experiment was carried out in industrial conditions on the precipitation of flat billets made of AK6 alloy on a hydraulic press with a deformation force of 150 MN. It is shown that the proposed software package can have a different functional purpose: express analysis of the pattern of metal flow and calculation of the shape of the billet at the stages of its deformation. This allows, by sorting through values of the geometric parameters of the stamp engraving, to obtain different patterns of metal flow and profiles of stiffeners and choose from them those that guarantee the most uniform filling of the stamp cavities with metal under the stiffeners, which ensures defect-free production of the product.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":" 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139142600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-688-695
S. I. Yares’ko, G. Guseva, V. I. Shcherbakov, P. V. Kazakevich
The paper presents the results of studies of macro- and microstructure of alloyed chromium-vanadium cast iron after laser treatment (LT) in air using a continuous laser source with a variation in its power from 60 to 100 W and scanning speed of the laser beam varying from 5 to 17 mm/s. Metallography and durometry methods were used to determine composition and structure of the laser exposure zones (LEZ). It is shown that LT with a slight melting of the surface leads to a significant increase in microhardness in LEZ. In this case, martensite is the main structure in the near-surface layer of LEZ in the melting zone, and ledeburite structure prevails in the quenching zone. For the studied LT modes, LEZ depth is 220 – 310 μm. At the same time, microhardness is more than 2.5 – 4.2 times higher than microhardness of the base metal and reaches 820 HV0.1, that is a significant factor in increasing the wear resistance of the material. On the contrary, no significant structural changes were found in the case of LT without melting the surface. In order to identify the role of LT in wear of cast iron, sliding friction tests were carried out according to the “disk – finger” scheme at a pressure in the contact zone of 12.5 MPa and indenter rotation speed of 580 rpm. According to the test data, a significant decrease in linear wear and the wear intensity after the surface melting was found. The wear intensity is reduced by more than 100 times, and linear wear – by more than 50 times. The characteristics of LEZ surface cause a decrease in the friction coefficient by 30 % relative to the untreated surface.
{"title":"Structure and wear characteristics of cast iron after laser surface modification","authors":"S. I. Yares’ko, G. Guseva, V. I. Shcherbakov, P. V. Kazakevich","doi":"10.17073/0368-0797-2023-6-688-695","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-688-695","url":null,"abstract":"The paper presents the results of studies of macro- and microstructure of alloyed chromium-vanadium cast iron after laser treatment (LT) in air using a continuous laser source with a variation in its power from 60 to 100 W and scanning speed of the laser beam varying from 5 to 17 mm/s. Metallography and durometry methods were used to determine composition and structure of the laser exposure zones (LEZ). It is shown that LT with a slight melting of the surface leads to a significant increase in microhardness in LEZ. In this case, martensite is the main structure in the near-surface layer of LEZ in the melting zone, and ledeburite structure prevails in the quenching zone. For the studied LT modes, LEZ depth is 220 – 310 μm. At the same time, microhardness is more than 2.5 – 4.2 times higher than microhardness of the base metal and reaches 820 HV0.1, that is a significant factor in increasing the wear resistance of the material. On the contrary, no significant structural changes were found in the case of LT without melting the surface. In order to identify the role of LT in wear of cast iron, sliding friction tests were carried out according to the “disk – finger” scheme at a pressure in the contact zone of 12.5 MPa and indenter rotation speed of 580 rpm. According to the test data, a significant decrease in linear wear and the wear intensity after the surface melting was found. The wear intensity is reduced by more than 100 times, and linear wear – by more than 50 times. The characteristics of LEZ surface cause a decrease in the friction coefficient by 30 % relative to the untreated surface.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":" 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139143555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-653-658
A. Vusikhis, L. I. Leont’ev, Yu. A. Chesnokov
The Bakal siderites belong to poor, hard-to-enrich carbonate iron ores. The low content of phosphorus and non-ferrous metals makes siderites a valuable raw material for obtaining highly metallized concentrate suitable for use in steelmaking processes. Reduction of siderites in a rotating furnace at 1300 – 1350 °C followed by magnetic separation of waste rock allows to obtain a concentrate with metallization degree over 90 % and a content of waste rock of about 5 % suitable for steelmaking as raw materials. The purpose of this work is to evaluate the efficiency of the process aimed at obtaining metal from siderite ore including obtaining of highly metallized siderite concentrate in a recovery furnace, as well as its hot loading into ore-thermal furnace and melting process itself. To do this, the electric melting was calculated in the electric ore melting furnace providing for determination of a large number of parameters including the electricity consumption required for melting. As raw materials we used a highly metallized siderite concentrate (φmet = 92.3 %) containing 35 % of waste rock and, for comparison, a briquetted metallized siderite concentrate obtained from a lump concentrate in which a significant amount of waste rock was removed by wet magnetic separation. The results analysis shows that increase in concentrate temperatures from 25 to 1000 °C decreases specific energy consumption and at the same time increases the furnace productivity to values comparable to the parameters of melting briquetted concentrate. This confirms the efficiency of the developed process. To reduce the melting point of high-magnesium slag, it is proposed to use colemanite as flux.
巴卡尔菱铁矿属于贫、难富集的碳酸盐铁矿石。由于磷和有色金属含量低，菱铁矿成为一种宝贵的原材料，可用于获得适合炼钢工艺的高金属化精矿。在 1300 - 1350 °C 的旋转炉中还原菱铁矿，然后对废石进行磁选，可获得金属化程度超过 90% 的精矿，废石含量约为 5%，适合作为炼钢原料。这项工作的目的是评估从菱铁矿中获取金属的工艺的效率，包括在回收炉中获得高度金属化的菱铁矿精矿，以及将其热装入矿热炉和熔炼工艺本身。为此，我们计算了矿石电熔炉中的电熔过程，从而确定了大量参数，包括熔炼所需的耗电量。作为原材料，我们使用了含有 35% 废石的高金属化菱铁矿精矿（φmet = 92.3%），以及从块状精矿中获得的压块金属化菱铁矿精矿（其中大量废石已通过湿式磁选去除）。结果分析表明，精矿温度从 25 °C 提高到 1000 °C，降低了比能耗，同时提高了熔炉生产率，其数值与熔炼压块精矿的参数相当。这证实了所开发工艺的效率。为了降低高镁渣的熔点，建议使用钴锰酸盐作为助熔剂。
{"title":"Evaluating the efficiency of metallized siderite concentrate electric melting","authors":"A. Vusikhis, L. I. Leont’ev, Yu. A. Chesnokov","doi":"10.17073/0368-0797-2023-6-653-658","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-653-658","url":null,"abstract":"The Bakal siderites belong to poor, hard-to-enrich carbonate iron ores. The low content of phosphorus and non-ferrous metals makes siderites a valuable raw material for obtaining highly metallized concentrate suitable for use in steelmaking processes. Reduction of siderites in a rotating furnace at 1300 – 1350 °C followed by magnetic separation of waste rock allows to obtain a concentrate with metallization degree over 90 % and a content of waste rock of about 5 % suitable for steelmaking as raw materials. The purpose of this work is to evaluate the efficiency of the process aimed at obtaining metal from siderite ore including obtaining of highly metallized siderite concentrate in a recovery furnace, as well as its hot loading into ore-thermal furnace and melting process itself. To do this, the electric melting was calculated in the electric ore melting furnace providing for determination of a large number of parameters including the electricity consumption required for melting. As raw materials we used a highly metallized siderite concentrate (φmet = 92.3 %) containing 35 % of waste rock and, for comparison, a briquetted metallized siderite concentrate obtained from a lump concentrate in which a significant amount of waste rock was removed by wet magnetic separation. The results analysis shows that increase in concentrate temperatures from 25 to 1000 °C decreases specific energy consumption and at the same time increases the furnace productivity to values comparable to the parameters of melting briquetted concentrate. This confirms the efficiency of the developed process. To reduce the melting point of high-magnesium slag, it is proposed to use colemanite as flux.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":" 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139144568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-733-742
V. I. Odinokov, A. I. Evstigneev, E. Dmitriev, V. A. Karpenko
The article proposes a new technology of filling the CCM mold with liquid metal and mixing it. The original patented device consists of a closed bottom nozzle and a rotating jacket. Experimental studies of liquid metal flow in a mold are long, complex and time-consuming, therefore, in the work was used mathematical modeling by numerical method. The objects of research are the hydrodynamic and thermal flows of liquid metal during the new process of steel casting into a CCM mold of rectangular cross-section, and the result is a spatial mathematical model that describes the flows and temperatures of liquid metal in the mold. To simulate the processes occurring during the metal flow in the mold, the authors used a specially created software package. The theoretical calculations are based on the fundamental equations of hydrodynamics, the equations of mathematical physics (equation of thermal conductivity taking into account mass transfer) and a proven numerical method. The area under study is divided into elements of finite dimensions, for each element a formulated system of equations is written in a difference form. The result is the velocity and temperature fields of the metal flow in the mold volume. According to the developed numerical schemes and algorithms, a calculation program was compiled. The paper considers an example of calculating the steel casting into a mold of rectangular cross-section and flow diagrams of liquid metal over various mold sections. Vector flows of liquid metal in various mold sections are clearly presented for different rotary speed of the rotating jacket. The authors identified the areas of intense turbulence and presented the results of the problem numerical solution in graphical form by diagrams of the velocity fields of liquid metal flows and their temperature over various mold sections.
{"title":"Simulation of a new process of mixing liquid metal in CCM mold with rotating cooling jacket with vertical ribs","authors":"V. I. Odinokov, A. I. Evstigneev, E. Dmitriev, V. A. Karpenko","doi":"10.17073/0368-0797-2023-6-733-742","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-733-742","url":null,"abstract":"The article proposes a new technology of filling the CCM mold with liquid metal and mixing it. The original patented device consists of a closed bottom nozzle and a rotating jacket. Experimental studies of liquid metal flow in a mold are long, complex and time-consuming, therefore, in the work was used mathematical modeling by numerical method. The objects of research are the hydrodynamic and thermal flows of liquid metal during the new process of steel casting into a CCM mold of rectangular cross-section, and the result is a spatial mathematical model that describes the flows and temperatures of liquid metal in the mold. To simulate the processes occurring during the metal flow in the mold, the authors used a specially created software package. The theoretical calculations are based on the fundamental equations of hydrodynamics, the equations of mathematical physics (equation of thermal conductivity taking into account mass transfer) and a proven numerical method. The area under study is divided into elements of finite dimensions, for each element a formulated system of equations is written in a difference form. The result is the velocity and temperature fields of the metal flow in the mold volume. According to the developed numerical schemes and algorithms, a calculation program was compiled. The paper considers an example of calculating the steel casting into a mold of rectangular cross-section and flow diagrams of liquid metal over various mold sections. Vector flows of liquid metal in various mold sections are clearly presented for different rotary speed of the rotating jacket. The authors identified the areas of intense turbulence and presented the results of the problem numerical solution in graphical form by diagrams of the velocity fields of liquid metal flows and their temperature over various mold sections.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":"94 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139147297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-718-724
D. S. Kryzhevich, A. Korchuganov, K. P. Zol’nikov
Molecular dynamic modelling of seed cracks evolution in iron bicrystals with inclined grain boundaries under uniaxial expansion was carried out. The process of seed crack evolution can be divided into four stages. At the first stage, in the interval of elastic deformations, the seed crack is stationary, and the stresses increase linearly, reaching a maximum value of ~7.0 GPa. At the same time, the atomic volume and stresses at the crack tip before its opening grow significantly faster than the average for the sample. At the second stage, the crack begins to spread into the grain volume. The process of crack propagation leads to an abrupt stress release due to relaxation processes in the areas adjacent to the crack banks and the emission of defects from the crack tip. After reaching the grain boundary, the crack stops and blunts. At the third stage, the crack remains in the grain boundary, and the sample stresses experience significant oscillations, which is caused by the emission of various defects both from the grain boundary and from other interfaces. The emission of defects from the crack tip can cause local migration of the grain boundary, which is formation of a bend on the initially flat surface of the grain boundary. When defects cease to be emitted from the crack tip, the voltage and atomic volume in this region increase rapidly. At the fourth stage, the crack begins to spread into the second grain. It was found that a boundary with a large grain misorientation angle is a more effective barrier restraining crack propagation. Initiation of the seed crack propagation in material is always preceded by an abrupt increase in atomic volume and stresses at the crack tip.
{"title":"Interaction of cracks with grain boundaries in iron bicrystals","authors":"D. S. Kryzhevich, A. Korchuganov, K. P. Zol’nikov","doi":"10.17073/0368-0797-2023-6-718-724","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-718-724","url":null,"abstract":"Molecular dynamic modelling of seed cracks evolution in iron bicrystals with inclined grain boundaries under uniaxial expansion was carried out. The process of seed crack evolution can be divided into four stages. At the first stage, in the interval of elastic deformations, the seed crack is stationary, and the stresses increase linearly, reaching a maximum value of ~7.0 GPa. At the same time, the atomic volume and stresses at the crack tip before its opening grow significantly faster than the average for the sample. At the second stage, the crack begins to spread into the grain volume. The process of crack propagation leads to an abrupt stress release due to relaxation processes in the areas adjacent to the crack banks and the emission of defects from the crack tip. After reaching the grain boundary, the crack stops and blunts. At the third stage, the crack remains in the grain boundary, and the sample stresses experience significant oscillations, which is caused by the emission of various defects both from the grain boundary and from other interfaces. The emission of defects from the crack tip can cause local migration of the grain boundary, which is formation of a bend on the initially flat surface of the grain boundary. When defects cease to be emitted from the crack tip, the voltage and atomic volume in this region increase rapidly. At the fourth stage, the crack begins to spread into the second grain. It was found that a boundary with a large grain misorientation angle is a more effective barrier restraining crack propagation. Initiation of the seed crack propagation in material is always preceded by an abrupt increase in atomic volume and stresses at the crack tip.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":"11 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139147827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-638-644
M. K. Shakirov, E. Protopopov, A. V. Zimin, E. B. Turchaninov
Prediction and control of the carbon content after the end of oxygen blow in BOF converter are key points of steel production efficiency. One of the most accurate methods is the dynamic predicting method based on the use of intermediate sublance measurement (TSC probe) when about 85 – 90 % of total oxygen is consumed and on the final period model. Models of the final period are traditionally based on exponential or cubic functions, currently there are developments based on neural network technologies. We investigated the possibility of using a neural network to predict the final carbon content using the results of intermediate sublance measurement (TSO probe) when about 95 % of total oxygen is consumed. As a model of the final period, a two-layer neural network with one hidden layer and an activation function of the Softplus type for all neurons was implemented in software. The input vectors contain initial carbon content and oxygen consumption for the second blow values. The output vector contains the predicted final carbon content, the output training vector - actual final carbon content values. The network was trained on 700 heats data of the training set. The model trained in this way was tested on 232 heats data of the testing set. The prediction errors distribution and values of the mean absolute error and root mean square error for the training and testing sets are correspondingly close. They are also comparable with similar indicators of the heats, the final period of which was carried out without oxygen blow (only flux additions and/or nitrogen blow), and this indicates a high accuracy of the prediction.
{"title":"Prediction of carbon content in the metal of final blow period in BOF using neural network","authors":"M. K. Shakirov, E. Protopopov, A. V. Zimin, E. B. Turchaninov","doi":"10.17073/0368-0797-2023-6-638-644","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-638-644","url":null,"abstract":"Prediction and control of the carbon content after the end of oxygen blow in BOF converter are key points of steel production efficiency. One of the most accurate methods is the dynamic predicting method based on the use of intermediate sublance measurement (TSC probe) when about 85 – 90 % of total oxygen is consumed and on the final period model. Models of the final period are traditionally based on exponential or cubic functions, currently there are developments based on neural network technologies. We investigated the possibility of using a neural network to predict the final carbon content using the results of intermediate sublance measurement (TSO probe) when about 95 % of total oxygen is consumed. As a model of the final period, a two-layer neural network with one hidden layer and an activation function of the Softplus type for all neurons was implemented in software. The input vectors contain initial carbon content and oxygen consumption for the second blow values. The output vector contains the predicted final carbon content, the output training vector - actual final carbon content values. The network was trained on 700 heats data of the training set. The model trained in this way was tested on 232 heats data of the testing set. The prediction errors distribution and values of the mean absolute error and root mean square error for the training and testing sets are correspondingly close. They are also comparable with similar indicators of the heats, the final period of which was carried out without oxygen blow (only flux additions and/or nitrogen blow), and this indicates a high accuracy of the prediction.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":"210 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139145423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-696-704
A. N. Dmitriev, V. G. Smirnova, E. Vyaznikova, G. Y. Vit’kina, A. S. Smirnov
Burnt pellets must retain their strength from the moment they are taken out of an induration machine until they are loaded into a blast furnace. One of the indicators of the burnt pellets’ strength is the compressive strength, i.e. the ultimate force. In experiments to determine compressive strength, the main type of fracture is occurrence and development of cracks that pass through the core center of pellets (where the maximum radial tensile stresses present) or near it. The paper presents the requirements for static compression strength imposed by blast furnace production to iron ore pellets. Using an optical and scanning electron microscope equipped with an energy-dispersive microanalyzer, we analyzed the relationship of structural components and pores in the core of burnt unfluxed iron ore titanomagnetite pellets with the ultimate force under static compression. By scanning electron microscopy and X-ray spectral microanalysis, it was established that the core of pellets is a multiphase material, and its main phases are titanomagnetite, magnetite, titanohematite, hematite and aluminosilicate binder. Optical microscopy made it possible to establish the microstructure of the pellet core, which has three types of microstructures: non-oxidized core (magnetite or titanomagnetite), partially oxidized core – around (magnetite or titanomagnetite) hematite grains (titanohematite) and oxidized core (hematite and titanohematite). The main factors for obtaining pellets with an ultimate force of more than 2.5 kN/pellet according to the requirements of blast furnace production are: the number of closed macropores and the number of large grains in the core. It is shown that with an increase in the number of closed macropores and the number of large grains in the core, the ultimate force is reduced from 3.5 kN to 0.87kN/pellet.
烧结球团从压实机中取出到装入高炉的整个过程中都必须保持强度。衡量烧成球团强度的指标之一是抗压强度，即极限力。在确定抗压强度的实验中，断裂的主要类型是穿过球团核心中心（存在最大径向拉伸应力的地方）或其附近的裂缝的出现和发展。本文介绍了高炉生产对铁矿球团静态抗压强度的要求。我们使用配有能量色散显微分析仪的光学显微镜和扫描电子显微镜，分析了未熔铁矿钛磁铁矿球团芯部的结构成分和孔隙与静态压缩极限力之间的关系。通过扫描电子显微镜和 X 射线光谱显微分析，确定了球团的核心是一种多相材料，其主要相为钛磁铁矿、磁铁矿、钛铁矿、赤铁矿和铝硅酸盐粘结剂。通过光学显微镜可以确定球团芯部的微观结构，它有三种微观结构：非氧化芯部（磁铁矿或钛磁铁矿）、部分氧化芯部--围绕（磁铁矿或钛磁铁矿）赤铁矿颗粒（钛铁矿）和氧化芯部（赤铁矿和钛铁矿）。根据高炉生产的要求，获得极限力大于 2.5 千牛/粒的球团的主要因素是：封闭大孔的数量和核心中大颗粒的数量。结果表明，随着闭合大孔数量和芯中大颗粒数量的增加，极限力从 3.5 千牛/粒降低到 0.87 千牛/粒。
{"title":"Effect of structure of unfluxed burnt titanomagnetite pellets on strength under static compression","authors":"A. N. Dmitriev, V. G. Smirnova, E. Vyaznikova, G. Y. Vit’kina, A. S. Smirnov","doi":"10.17073/0368-0797-2023-6-696-704","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-696-704","url":null,"abstract":"Burnt pellets must retain their strength from the moment they are taken out of an induration machine until they are loaded into a blast furnace. One of the indicators of the burnt pellets’ strength is the compressive strength, i.e. the ultimate force. In experiments to determine compressive strength, the main type of fracture is occurrence and development of cracks that pass through the core center of pellets (where the maximum radial tensile stresses present) or near it. The paper presents the requirements for static compression strength imposed by blast furnace production to iron ore pellets. Using an optical and scanning electron microscope equipped with an energy-dispersive microanalyzer, we analyzed the relationship of structural components and pores in the core of burnt unfluxed iron ore titanomagnetite pellets with the ultimate force under static compression. By scanning electron microscopy and X-ray spectral microanalysis, it was established that the core of pellets is a multiphase material, and its main phases are titanomagnetite, magnetite, titanohematite, hematite and aluminosilicate binder. Optical microscopy made it possible to establish the microstructure of the pellet core, which has three types of microstructures: non-oxidized core (magnetite or titanomagnetite), partially oxidized core – around (magnetite or titanomagnetite) hematite grains (titanohematite) and oxidized core (hematite and titanohematite). The main factors for obtaining pellets with an ultimate force of more than 2.5 kN/pellet according to the requirements of blast furnace production are: the number of closed macropores and the number of large grains in the core. It is shown that with an increase in the number of closed macropores and the number of large grains in the core, the ultimate force is reduced from 3.5 kN to 0.87kN/pellet.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":"77 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139146495","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-705-708
L. P. Bashchenko, V. Pochetukha, T. A. Mikhailichenko
The technology of plasma surfacing in a protective-alloying nitrogen medium with an additive powder wire is characterized by high productivity and the possibility of alloying the deposited metal. Durability of metal products depends on microstructure, chemical composition, production technology, modes of thermal and surface treatments. The article presents the results of a study of structure and microhardness of the high speed alloy R18Yu deposited in nitrogen medium on medium-carbon steel 30KhGSA. There were no differences in structure of the surfacing layer up to 4 mm in depth, but after four times high-temperature tempering at 580 °C, structural and phase changes were revealed. The values of microhardness after surfacing and tempering are consistent with the literature data.
在氮保护合金介质中使用添加剂粉末线进行等离子表面处理的技术具有生产率高和可对沉积金属进行合金化处理的特点。金属产品的耐久性取决于微观结构、化学成分、生产技术、热处理和表面处理方式。文章介绍了在氮介质中沉积在中碳钢 30KhGSA 上的高速合金 R18Yu 的结构和显微硬度的研究结果。深度达 4 毫米的堆焊层结构没有差异，但在 580 °C 高温回火四次后，结构和相变显现出来。堆焊和回火后的显微硬度值与文献数据一致。
{"title":"Influence of tempering on structure of deposited high speed steel coatings","authors":"L. P. Bashchenko, V. Pochetukha, T. A. Mikhailichenko","doi":"10.17073/0368-0797-2023-6-705-708","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-705-708","url":null,"abstract":"The technology of plasma surfacing in a protective-alloying nitrogen medium with an additive powder wire is characterized by high productivity and the possibility of alloying the deposited metal. Durability of metal products depends on microstructure, chemical composition, production technology, modes of thermal and surface treatments. The article presents the results of a study of structure and microhardness of the high speed alloy R18Yu deposited in nitrogen medium on medium-carbon steel 30KhGSA. There were no differences in structure of the surfacing layer up to 4 mm in depth, but after four times high-temperature tempering at 580 °C, structural and phase changes were revealed. The values of microhardness after surfacing and tempering are consistent with the literature data.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":"7 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139148089","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-673-680
V. Danilov, D. V. Orlova, V. Gorbatenko, L. Danilova
The authors studied the nature of mobile fronts of localized deformation that generate and propagate during deformation of metastable austenitic-martensitic TRIP steel VNS9-Sh along the entire length of the loading curve from the yield point to fracture. A joint research of the nature of the deformation fronts movement and kinetics of the magnetic phase accumulation made it possible to establish that the fronts under consideration are the fronts of the thermoelastic phase transformation of metastable austenite into martensite. This transformation is realized firstly by formation of the Chernov–Lüders bands and then the Portevin–Le Chatelier bands. Both processes are consistent with staging of the deformation curve, which contains a pseudo-plateau, a section with an increasing hardening coefficient, and a section with a decreasing hardening coefficient. It is shown that the deformation-induced phase transformation corresponds to the fronts propagating on the pseudo-plateau and on the section of loading curve with an increasing hardening coefficient. The Portevin–Le Chatelier bands, which are formed in the section of the loading diagram with a decreasing hardening coefficient, are not associated with “austenite-martensite” transformation and have a twin nature. The kinetics of thermoelastic transformation fronts, as well as deformation fronts in materials with a shear mechanism of shaping, can be described in terms of the autowave concept. On the yield plateaus, the phase transformation occurs through generation and propagation of localized plasticity switching autowaves. In the section with an increasing hardening coefficient, it continues through generation and movement of excitation autowaves. The propagation regions of excitation autowaves are limited in the sample space. They are set by the zones of origin and annihilation of primary switching autowaves which were formed on the yield plateau.
{"title":"Lüders and Portevin–Le Chatelier processes in austenitic-martensitic TRIP steel","authors":"V. Danilov, D. V. Orlova, V. Gorbatenko, L. Danilova","doi":"10.17073/0368-0797-2023-6-673-680","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-673-680","url":null,"abstract":"The authors studied the nature of mobile fronts of localized deformation that generate and propagate during deformation of metastable austenitic-martensitic TRIP steel VNS9-Sh along the entire length of the loading curve from the yield point to fracture. A joint research of the nature of the deformation fronts movement and kinetics of the magnetic phase accumulation made it possible to establish that the fronts under consideration are the fronts of the thermoelastic phase transformation of metastable austenite into martensite. This transformation is realized firstly by formation of the Chernov–Lüders bands and then the Portevin–Le Chatelier bands. Both processes are consistent with staging of the deformation curve, which contains a pseudo-plateau, a section with an increasing hardening coefficient, and a section with a decreasing hardening coefficient. It is shown that the deformation-induced phase transformation corresponds to the fronts propagating on the pseudo-plateau and on the section of loading curve with an increasing hardening coefficient. The Portevin–Le Chatelier bands, which are formed in the section of the loading diagram with a decreasing hardening coefficient, are not associated with “austenite-martensite” transformation and have a twin nature. The kinetics of thermoelastic transformation fronts, as well as deformation fronts in materials with a shear mechanism of shaping, can be described in terms of the autowave concept. On the yield plateaus, the phase transformation occurs through generation and propagation of localized plasticity switching autowaves. In the section with an increasing hardening coefficient, it continues through generation and movement of excitation autowaves. The propagation regions of excitation autowaves are limited in the sample space. They are set by the zones of origin and annihilation of primary switching autowaves which were formed on the yield plateau.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":" 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139144088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-29DOI: 10.17073/0368-0797-2023-6-645-652
A. Umanskii, V. V. Baidin, A. Simachev, L. Dumova, S. O. Safonov
Studies of the formation of microstructure of grinding balls from the rejects of rail steel were carried out during their quenching in various polymer media. At the first stage, based on studies of the cooling capacity of solutions of polymers PCM and Thermovit with varying concentrations and temperatures, the authors constructed the cooling curves of grinding balls made of K76F rail steel. It was found that at concentration of these polymers in an aqueous solution of 2 and 4 %, cooling rate of grinding balls made of K76F steel is almost identical at solution temperatures of 20 and 30 °C and significantly decreases when the temperature of the polymer solution increases to 40 °C. At the same time, the most noticeable decrease in the cooling rate is characteristic of PCM polymer with its concentration at the level of 2 %. At the second stage, the authors carried out metallographic studies of the microstructure of grinding balls made of K76F rail steel, which were quenched in laboratory conditions using polymers PCM and Thermovit with concentrations of 2 – 4 % and temperature of 20 – 40 °C. As a result, it was determined that the use of the PCM solution for quenching balls provides a significantly higher quality of microstructure and hardness of heat-treated balls compared to the use of the Thermovit polymer. At the same time, varying the concentration and temperature of the PCM polymer quenching medium allows one to obtain grinding balls with different performance characteristics that determine the potential areas of their application. Thus, quenching of balls in a solution of the specified polymer with concentration of 2 % and temperature of 20 – 30 °C ensures the production of balls with high hardness (corresponding to the IV hardness group according to the state standard GOST 7524 – 2015), and the use of a solution of the same polymer with concentration of 4 % and temperature of 20 – 30 °С for quenching creates the possibility of producing balls with lower hardness, but potentially high impact resistance.
{"title":"Formation of microstructure in rail steel grinding balls depending on quenching medium parameters","authors":"A. Umanskii, V. V. Baidin, A. Simachev, L. Dumova, S. O. Safonov","doi":"10.17073/0368-0797-2023-6-645-652","DOIUrl":"https://doi.org/10.17073/0368-0797-2023-6-645-652","url":null,"abstract":"Studies of the formation of microstructure of grinding balls from the rejects of rail steel were carried out during their quenching in various polymer media. At the first stage, based on studies of the cooling capacity of solutions of polymers PCM and Thermovit with varying concentrations and temperatures, the authors constructed the cooling curves of grinding balls made of K76F rail steel. It was found that at concentration of these polymers in an aqueous solution of 2 and 4 %, cooling rate of grinding balls made of K76F steel is almost identical at solution temperatures of 20 and 30 °C and significantly decreases when the temperature of the polymer solution increases to 40 °C. At the same time, the most noticeable decrease in the cooling rate is characteristic of PCM polymer with its concentration at the level of 2 %. At the second stage, the authors carried out metallographic studies of the microstructure of grinding balls made of K76F rail steel, which were quenched in laboratory conditions using polymers PCM and Thermovit with concentrations of 2 – 4 % and temperature of 20 – 40 °C. As a result, it was determined that the use of the PCM solution for quenching balls provides a significantly higher quality of microstructure and hardness of heat-treated balls compared to the use of the Thermovit polymer. At the same time, varying the concentration and temperature of the PCM polymer quenching medium allows one to obtain grinding balls with different performance characteristics that determine the potential areas of their application. Thus, quenching of balls in a solution of the specified polymer with concentration of 2 % and temperature of 20 – 30 °C ensures the production of balls with high hardness (corresponding to the IV hardness group according to the state standard GOST 7524 – 2015), and the use of a solution of the same polymer with concentration of 4 % and temperature of 20 – 30 °С for quenching creates the possibility of producing balls with lower hardness, but potentially high impact resistance.","PeriodicalId":14630,"journal":{"name":"Izvestiya. Ferrous Metallurgy","volume":" 4","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139144733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：