S. Artomova, O. Budarin, V. Bondarenko, O. Bezvesilna, O. Ponomarenko, A. Marchenko, O. Akimov, V. P. Mykhailiukov
The mode of heat treatment of massive castings of the blades of the impeller of the hydroturbine "Dniester HPSP" from steel of the martensitic class CA-6NM has been worked out. Based on the determination of mechanical properties, measurements of stiffness over the entire surface of the blades and metallographic studies, the expediency of the proposed heat treatment mode using intensive cooling and high tempering after high-temperature austenitizing heating is shown. It is shown that this mode provides the necessary level of mechanical properties of blade castings, eliminates the negative effect of internal stresses arising during crystallization and rapid cooling during subsequent heat treatment. Determination of the chemical composition of castings and its compliance with the requirements of ASTM A743 / A743M-98a ensures that the required level of product properties is obtained. Metallographically established the absence of unwanted segregation and the uniformity of the structure, the uniformity of mechanical properties over the body of the blade, which leads to an increase in resistance to destruction due to cavitation. As a result of the research, the expediency of using the following heat treatment mode for massive complex-profile castings of blades made of corrosion-resistant steel of martensitic class CA-6NM, consisting of heating to a temperature of 1030-1040°C and tempering at 580-590°C using rapid cooling, was confirmed. Keywords: hydraulic turbine blades, heat treatment, structure, mechanical properties.
{"title":"Heat treatment and properties of a cast complex profile blade of a hydroturbine","authors":"S. Artomova, O. Budarin, V. Bondarenko, O. Bezvesilna, O. Ponomarenko, A. Marchenko, O. Akimov, V. P. Mykhailiukov","doi":"10.15407/mom2022.02.058","DOIUrl":"https://doi.org/10.15407/mom2022.02.058","url":null,"abstract":"The mode of heat treatment of massive castings of the blades of the impeller of the hydroturbine \"Dniester HPSP\" from steel of the martensitic class CA-6NM has been worked out. Based on the determination of mechanical properties, measurements of stiffness over the entire surface of the blades and metallographic studies, the expediency of the proposed heat treatment mode using intensive cooling and high tempering after high-temperature austenitizing heating is shown. It is shown that this mode provides the necessary level of mechanical properties of blade castings, eliminates the negative effect of internal stresses arising during crystallization and rapid cooling during subsequent heat treatment. Determination of the chemical composition of castings and its compliance with the requirements of ASTM A743 / A743M-98a ensures that the required level of product properties is obtained. Metallographically established the absence of unwanted segregation and the uniformity of the structure, the uniformity of mechanical properties over the body of the blade, which leads to an increase in resistance to destruction due to cavitation. As a result of the research, the expediency of using the following heat treatment mode for massive complex-profile castings of blades made of corrosion-resistant steel of martensitic class CA-6NM, consisting of heating to a temperature of 1030-1040°C and tempering at 580-590°C using rapid cooling, was confirmed. Keywords: hydraulic turbine blades, heat treatment, structure, mechanical properties.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44527552","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}
Modern construction metallic materials often work under conditions, where it is necessary to show properties uninherent to continuous materials. High–porous materials have a cellular structure and are characterized with low dencity, high specific stiffness that provides specific advantages above dense materials. The paper reviews such materials with the oriented porous structure – gasars. The theoretical and technological bases of their manufacturing were first developed in Ukraine. Their difference from foamed metals by powder or liquid methods, which are formed under the action of gas–forming reagents, is noted. The formation of gas pores in gasars occurs as a result of a gas–eutectic reaction with the formation of bubbles at the crystallization front in gas–metal systems due to changes in the solubility of gases. The morphology of the pore channels depends on many factors, including the intensity and direction of heat removal. Techniques and equipment are considered, which provides control the macrostructure of the material with the formation of various morphologies – from large cavities, spherical pores to evenly distributed elongated channels of the same or variable cross–section and gradient monolithic porous structures. It is determined that most technologies use hydrogen as a pore formed gas, although there are examples of successful use of hydrocarbons (CH4), water vapor, nitrogen, ammonia and the like. Over the years of research, scientists from different countries have developed methods for obtaining gasars not only on the basis of iron–carbon alloys but also aluminum, copper, nickel, titanium alloys. An analysis of the existing and future opportunities for gasars application noted that it depends on more complete study of gas–eutectic transformations and related processes in the crystallization of melts for their control and development of cost–effective technologies for such materials. Keywords: gasars, oriented porous structure, gas–eutectic reaction, mechanical properties.
{"title":"Novel constructional materials with an oriented porous structure – gazars","authors":"S. Gnyloskurenko, S. Kondratyuk","doi":"10.15407/mom2022.02.022","DOIUrl":"https://doi.org/10.15407/mom2022.02.022","url":null,"abstract":"Modern construction metallic materials often work under conditions, where it is necessary to show properties uninherent to continuous materials. High–porous materials have a cellular structure and are characterized with low dencity, high specific stiffness that provides specific advantages above dense materials. The paper reviews such materials with the oriented porous structure – gasars. The theoretical and technological bases of their manufacturing were first developed in Ukraine. Their difference from foamed metals by powder or liquid methods, which are formed under the action of gas–forming reagents, is noted. The formation of gas pores in gasars occurs as a result of a gas–eutectic reaction with the formation of bubbles at the crystallization front in gas–metal systems due to changes in the solubility of gases. The morphology of the pore channels depends on many factors, including the intensity and direction of heat removal. Techniques and equipment are considered, which provides control the macrostructure of the material with the formation of various morphologies – from large cavities, spherical pores to evenly distributed elongated channels of the same or variable cross–section and gradient monolithic porous structures. It is determined that most technologies use hydrogen as a pore formed gas, although there are examples of successful use of hydrocarbons (CH4), water vapor, nitrogen, ammonia and the like. Over the years of research, scientists from different countries have developed methods for obtaining gasars not only on the basis of iron–carbon alloys but also aluminum, copper, nickel, titanium alloys. An analysis of the existing and future opportunities for gasars application noted that it depends on more complete study of gas–eutectic transformations and related processes in the crystallization of melts for their control and development of cost–effective technologies for such materials. Keywords: gasars, oriented porous structure, gas–eutectic reaction, mechanical properties.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41382016","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}
In order to solve the problems of improving the reliability and efficiency of aircraft engines, the paper considers as an alternative to traditional methods of obtaining aviation parts using additive production. According to the three-dimensional digital model (CAD/CAM/CAE-systems), additive technologies allow creating complex structures with high mechanical and operational characteristics. They must be complied with the standard ASTM F2792.1549323-1. The process of additive production is characterized by a sequence of operations: construction of a digital 3D–model → the choice of additive technology and its implementation → obtaining the finished part. In the work it is proposed to consider the possibility of growing the aircraft part «Swirler» from heat-resistant nickel alloy Inconel 718 by selective laser sintering technology in a 3D–printer type EOS M400 under the conditions of JSC «Motor Sich». Spherical nickel-based powders from Sino-Euro Materials Technologies of Xi'an Co., Ltd. were used as starting powder materials. (Sino Euro, China) and LPW Technology, Ltd (LPW, UK). The dependence of the mechanical and heat-resistant properties of the Inconel 718 alloy on the direction of growth of the part (in particular, the horizontal direction XY and the vertical direction Z) was established experimentally. Metallographic studies of Inconel 718 alloy samples before and after the heat treatment process were performed. With the help of Unigraphics NX 7.5, the modeling of an aircraft part was performed, which begins with the construction of a sketch, design of a digital 3D–model of the part and its editing. It is shown that the cultivation of the aviation part «Swirler» by the technology of selective laser sintering is characterized by: a smaller number of technological operations for the manufacture of «complex» in the geometric configuration of the part; reducing up to 6 times the lack of finished parts; reduction of material costs for equipment and additional machining; reduction to 12–17 % of the weight of the part in comparison with its metal analogue obtained by machining. Keywords: additive technologies, selective laser sintering, Inconel 718, 3D–model, aviation part.
{"title":"Creating of aviation part «Swirler» from Inconel 718 heat-resistant alloy by the technology of selective laser sintering","authors":"O. Vodennikova, M. O. Koval, S. Vodennikov","doi":"10.15407/mom2022.02.012","DOIUrl":"https://doi.org/10.15407/mom2022.02.012","url":null,"abstract":"In order to solve the problems of improving the reliability and efficiency of aircraft engines, the paper considers as an alternative to traditional methods of obtaining aviation parts using additive production. According to the three-dimensional digital model (CAD/CAM/CAE-systems), additive technologies allow creating complex structures with high mechanical and operational characteristics. They must be complied with the standard ASTM F2792.1549323-1. The process of additive production is characterized by a sequence of operations: construction of a digital 3D–model → the choice of additive technology and its implementation → obtaining the finished part. In the work it is proposed to consider the possibility of growing the aircraft part «Swirler» from heat-resistant nickel alloy Inconel 718 by selective laser sintering technology in a 3D–printer type EOS M400 under the conditions of JSC «Motor Sich». Spherical nickel-based powders from Sino-Euro Materials Technologies of Xi'an Co., Ltd. were used as starting powder materials. (Sino Euro, China) and LPW Technology, Ltd (LPW, UK). The dependence of the mechanical and heat-resistant properties of the Inconel 718 alloy on the direction of growth of the part (in particular, the horizontal direction XY and the vertical direction Z) was established experimentally. Metallographic studies of Inconel 718 alloy samples before and after the heat treatment process were performed. With the help of Unigraphics NX 7.5, the modeling of an aircraft part was performed, which begins with the construction of a sketch, design of a digital 3D–model of the part and its editing. It is shown that the cultivation of the aviation part «Swirler» by the technology of selective laser sintering is characterized by: a smaller number of technological operations for the manufacture of «complex» in the geometric configuration of the part; reducing up to 6 times the lack of finished parts; reduction of material costs for equipment and additional machining; reduction to 12–17 % of the weight of the part in comparison with its metal analogue obtained by machining. Keywords: additive technologies, selective laser sintering, Inconel 718, 3D–model, aviation part.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45139203","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}
The paper presents the results of the study of the influence of structure on the mechanical properties of microalloyed and modified austenitic stainless steels. It is shown that the mechanical properties of cast austenitic stainless steels with a probability of 95 % and an error of 0.46 to 13.2 % are determined by such structural parameters as austenite grain size, carbide phase and ferrite content in austenite after quenching, quantity, size and distance between oxide, titanium sulfides and carbonitrides particles. Mathematical models of the structure influence on the yield strength, reduction of area and toughness of stainless steels are built. The structure parameter effectiveness is shown and it is shown that to increase the efficiency of strength, reduction of area and toughness of stainless steels at normal temperature structural factors affect in the following sequence: austenite grain size, volume fraction, size and distribution of titanium carbonitrides and sulfides, the total quantity of non-metallic inclusions, carbides and ferrite in austenite after hardening of stainless steel, as well as the volume fraction, size and distribution of oxide inclusions. Keywords: steel, structure, mechanical properties, strength, ductility, toughness.
{"title":"The effect of heat treatment on the mechanical properties of modified stainless steels","authors":"Y. Aftandiliants","doi":"10.15407/mom2022.02.045","DOIUrl":"https://doi.org/10.15407/mom2022.02.045","url":null,"abstract":"The paper presents the results of the study of the influence of structure on the mechanical properties of microalloyed and modified austenitic stainless steels. It is shown that the mechanical properties of cast austenitic stainless steels with a probability of 95 % and an error of 0.46 to 13.2 % are determined by such structural parameters as austenite grain size, carbide phase and ferrite content in austenite after quenching, quantity, size and distance between oxide, titanium sulfides and carbonitrides particles. Mathematical models of the structure influence on the yield strength, reduction of area and toughness of stainless steels are built. The structure parameter effectiveness is shown and it is shown that to increase the efficiency of strength, reduction of area and toughness of stainless steels at normal temperature structural factors affect in the following sequence: austenite grain size, volume fraction, size and distribution of titanium carbonitrides and sulfides, the total quantity of non-metallic inclusions, carbides and ferrite in austenite after hardening of stainless steel, as well as the volume fraction, size and distribution of oxide inclusions. Keywords: steel, structure, mechanical properties, strength, ductility, toughness.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46307894","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}
N. Filonenko, O. Babachenko, G. Kononenko, O. Safronova
In the paper, the comparative analysis of the process of forming a cast structure of carbon steel after termination of its crystallization in continuous cast steel billet with diameter of 450 mm and overheating of steel to 50° C and 150° C above the liquidus line, and further pouring into wedge-shaped molds, is performed. The microstructure of the skin zone after continuous casting of steel with maximum cooling rate of 106 °С/min consists of dendrites, which have branches of the first and second order, indicating their formation from the melt. When etching the surface of the specimens with solution of nitric acid, the microstructure of the skin zone was represented by ferrite, perlite with separate areas of martensite. The formation of ferrite, perlite and bainite areas was observed at a distance of 0.5 ingot radius and in the central part of the samples, and separate areas of bainite and perlite were observed in the central part of the ingot. Upon further cooling of steels below the temperature of Ar3, the formation of excess ferrite along the boundaries of austenitic grains occurs. Overheating of steels to 50° C and 150° C above the liquidus line gives rise to the formation of a more homogeneous structure. Non-metallic inclusions formed in steel do not exceed 1 point according to DSTU 4967:2015and are not the centres of crystallization – they are observed in perlite grains. There is the formation of separate inclusions of phases located in the perlite grain, which contributes to the finely dispersed hardening of steel. Increasing the overheating temperature leads to the formation of more finely divided inclusions and to the formation of a more homogeneous structure. After overheating to 50° C in the middle part of the wedge (cooling rate of 102-103 ° C/min) no ferrite formation is observed. At all overheating temperatures, perlite has a fine differentiation, but increasing in the overheating temperature above the liquidus line enhances the dispersion of both individual inclusions and perlite. Keywords: carbon steel, continuous cast steel billet, hardening, cooling rate, overheating of steels above the liquidus line.
{"title":"Rate effect of cooling and overheating above the liquidus line on the formation of structural constituents","authors":"N. Filonenko, O. Babachenko, G. Kononenko, O. Safronova","doi":"10.15407/mom2022.02.003","DOIUrl":"https://doi.org/10.15407/mom2022.02.003","url":null,"abstract":"In the paper, the comparative analysis of the process of forming a cast structure of carbon steel after termination of its crystallization in continuous cast steel billet with diameter of 450 mm and overheating of steel to 50° C and 150° C above the liquidus line, and further pouring into wedge-shaped molds, is performed. The microstructure of the skin zone after continuous casting of steel with maximum cooling rate of 106 °С/min consists of dendrites, which have branches of the first and second order, indicating their formation from the melt. When etching the surface of the specimens with solution of nitric acid, the microstructure of the skin zone was represented by ferrite, perlite with separate areas of martensite. The formation of ferrite, perlite and bainite areas was observed at a distance of 0.5 ingot radius and in the central part of the samples, and separate areas of bainite and perlite were observed in the central part of the ingot. Upon further cooling of steels below the temperature of Ar3, the formation of excess ferrite along the boundaries of austenitic grains occurs. Overheating of steels to 50° C and 150° C above the liquidus line gives rise to the formation of a more homogeneous structure. Non-metallic inclusions formed in steel do not exceed 1 point according to DSTU 4967:2015and are not the centres of crystallization – they are observed in perlite grains. There is the formation of separate inclusions of phases located in the perlite grain, which contributes to the finely dispersed hardening of steel. Increasing the overheating temperature leads to the formation of more finely divided inclusions and to the formation of a more homogeneous structure. After overheating to 50° C in the middle part of the wedge (cooling rate of 102-103 ° C/min) no ferrite formation is observed. At all overheating temperatures, perlite has a fine differentiation, but increasing in the overheating temperature above the liquidus line enhances the dispersion of both individual inclusions and perlite. Keywords: carbon steel, continuous cast steel billet, hardening, cooling rate, overheating of steels above the liquidus line.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47264433","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}
T. Loskutova, I. Pogrebova, Ya.А. Kononenko, S. Kotlyar
The influence of the amount of halogen-containing activator on the structure, composition and properties of diffusion layers, which are formed during the complex saturation of the titanium alloy VT6 with chromium and aluminum, is investigated. The coating was applied by powder method in chlorine under reduced pressure, at a temperature of 850 ° C for 4 hours in a saturating mixture consisting of powders of saturating metals (chromium, aluminum), inert backfill Al2O3 and activator. As the activator used NH4Cl, the amount of which varied in the range from 3 to 9 % of the mass. The optimal amount of activator in the saturating mixture is determined. The microstructure, chemical composition, thickness and microhardness of the obtained diffusion coatings were studied. It was found that when using 3% NH4Cl, the obtained coatings consist of three layers, dark gray, which are completely located on the surface and correspond to the phases based on TiAl, intermetallic with (Ti, V, Cr, Al) and Ti3Al. A transition zone based on α-Ti is formed directly under the coating. The microhardness of the obtained layers is quite high and is 5.1-9.6 GPa, the total thickness is 46.0-48.0 μm. Reducing the amount of activator leads to the formation of discontinuous surface layers of the coating, which will lead to differences in the properties of its surface layers. Increase - to the destruction of the surface layers of the coating and equipment directly during the chemical-thermal treatment. Keywords: chromium, aluminum, titanium alloy, activator, diffusion coatings.
{"title":"Influence of activator on the structure and properties of chromium-alloyed titanium alloy VT6","authors":"T. Loskutova, I. Pogrebova, Ya.А. Kononenko, S. Kotlyar","doi":"10.15407/mom2022.02.052","DOIUrl":"https://doi.org/10.15407/mom2022.02.052","url":null,"abstract":"The influence of the amount of halogen-containing activator on the structure, composition and properties of diffusion layers, which are formed during the complex saturation of the titanium alloy VT6 with chromium and aluminum, is investigated. The coating was applied by powder method in chlorine under reduced pressure, at a temperature of 850 ° C for 4 hours in a saturating mixture consisting of powders of saturating metals (chromium, aluminum), inert backfill Al2O3 and activator. As the activator used NH4Cl, the amount of which varied in the range from 3 to 9 % of the mass. The optimal amount of activator in the saturating mixture is determined. The microstructure, chemical composition, thickness and microhardness of the obtained diffusion coatings were studied. It was found that when using 3% NH4Cl, the obtained coatings consist of three layers, dark gray, which are completely located on the surface and correspond to the phases based on TiAl, intermetallic with (Ti, V, Cr, Al) and Ti3Al. A transition zone based on α-Ti is formed directly under the coating. The microhardness of the obtained layers is quite high and is 5.1-9.6 GPa, the total thickness is 46.0-48.0 μm. Reducing the amount of activator leads to the formation of discontinuous surface layers of the coating, which will lead to differences in the properties of its surface layers. Increase - to the destruction of the surface layers of the coating and equipment directly during the chemical-thermal treatment. Keywords: chromium, aluminum, titanium alloy, activator, diffusion coatings.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41624049","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}
This paper deals with structure formation in weld joints of quenching steels 15Cr5Мo and 12Cr1МoV as made by “short cycle” argon-shielded welding as well as with the possibility of control of transformation and quality for weld joints by the thermodynamic cycle of welding. It is demonstrated that where the developed technology is applied, the weld metal is sound, defect-free, of martensitic-ferritic structure. In the weld-affected zone of steels at high heating rates and with short time of metal exposure to temperatures exceeding critical transformation temperatures in heating, non-uniform austenite of low homogeneity is formed, in which the carbide phase containing alloy elements undergoes partial dissolution. As a result, the austenite breakdown in cooling (in spite of high rates) takes place in the bainitic range as well as in the martensitic range. In the weld-affected zone of steel 12Cr1МoV, the bainitic structure predominates while the weld-affected zone of steel 15Cr5Мo shows the bainitic-martensitic structure mainly. During weld joint inspection by shock loading testing, the metal having the above structure experiences bending or ductile fracture. The process parameters were determined, with which structures of high brittle fracture resistance are formed. The technology developed was implemented in tube studding for manufacture and repairs of cooling panels; it is recommended for common use in industrial applications. Keywords: welding, quenching, thermodynamic cycle, argon, bainite, quality, application.
{"title":"Structure formation at high rates of heating during welding of steels","authors":"S. Artyomova","doi":"10.15407/mom2022.01.037","DOIUrl":"https://doi.org/10.15407/mom2022.01.037","url":null,"abstract":"This paper deals with structure formation in weld joints of quenching steels 15Cr5Мo and 12Cr1МoV as made by “short cycle” argon-shielded welding as well as with the possibility of control of transformation and quality for weld joints by the thermodynamic cycle of welding. It is demonstrated that where the developed technology is applied, the weld metal is sound, defect-free, of martensitic-ferritic structure. In the weld-affected zone of steels at high heating rates and with short time of metal exposure to temperatures exceeding critical transformation temperatures in heating, non-uniform austenite of low homogeneity is formed, in which the carbide phase containing alloy elements undergoes partial dissolution. As a result, the austenite breakdown in cooling (in spite of high rates) takes place in the bainitic range as well as in the martensitic range. In the weld-affected zone of steel 12Cr1МoV, the bainitic structure predominates while the weld-affected zone of steel 15Cr5Мo shows the bainitic-martensitic structure mainly. During weld joint inspection by shock loading testing, the metal having the above structure experiences bending or ductile fracture. The process parameters were determined, with which structures of high brittle fracture resistance are formed. The technology developed was implemented in tube studding for manufacture and repairs of cooling panels; it is recommended for common use in industrial applications. Keywords: welding, quenching, thermodynamic cycle, argon, bainite, quality, application.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45184938","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}
It has been established that the downtime of ball mills due to the low durability of cast parts is 70...80 % of the total number of downtime, while material damage is estimated in hundreds of thousands of hryvnia. One of the weakest units of these mills are the discharge grids and scoops of the cochlear feeder, the durability of which reaches 5.5...6 months and 1.0...1.5 months, respectively, with the resource of operation of other parts of the mill 9...12 months. As a result of the analysis of the operating conditions of the gratings and scoops of the MSHR, it was found that the duration of operation and the mechanical properties of these parts depend mainly on the material from which they are made. Steel with a high level of plasticity and toughness (35GFL, 35HNL, 34HNML, etc.) had insufficient wear resistance due to low strength, hardness. Materials with a high level of hardness and strength (60Kh2SML) had a low impact toughness, which was the reason for emergency shutdowns of the mills as a result of breakdowns of parts. The analysis of the mechanical properties of ladles and gratings has established the required level of properties of these parts; σВ ≥ 850 MPa; НВ ≥ 2600 МPa; δ ≥ 8 %; Ψ ≥ 20 %, KCU ≥ 0,20 MJ/m2. The effect of changing the silicon concentration on the mechanical properties and wear resistance of steel containing 1.5% chromium and 0.40% manganese with different carbon contents has been studied. With an increase in the silicon content, the strength and hardness indicators increase. The effect of silicon on the plastic properties of steel, impact strength and wear resistance is nonlinear, with 0.9% manganese in this case, a monotonic decrease is observed not only in plastic properties and toughness, but also in wear resistance. This is explained by the fact that with an increase in the manganese content in steel, the segregation heterogeneity and stability of supercooled austenite increase, leading, after normalization, to the formation of a martensite-like structure. It is shown that in the production of castings operating under conditions of abrasive wear in combination with shock loads, it is advisable to observe the ratio of silicon to carbon 2.0...2.5. Mathematical planning of the experiment made it possible to obtain models that adequately describe the effect of the composition of steel on the level of its mechanical and operational properties. Based on the processing of the data obtained from the «STATISTICA» software package, a wear-resistant economically alloyed steel of the following composition was proposed: 0.45...0.50 % carbon; 1.7...2.0 % chromium; 0.5...0.7 % manganese; 1.2...1.5 % silicon. The use of such a composition of steel for the manufacture of unloading gratings and scoops of snail feeder allowed to increase their service life by 1.5 times by improving performance, and, consequently, reduce the maintenance cycle of ball mills, which increased economic efficiency. Keywords: ball grinding mill, alloy steel,
{"title":"Economically alloyed steel for the needs of the mining industry","authors":"V. Shalomeev, O. Liutova","doi":"10.15407/mom2022.01.044","DOIUrl":"https://doi.org/10.15407/mom2022.01.044","url":null,"abstract":"It has been established that the downtime of ball mills due to the low durability of cast parts is 70...80 % of the total number of downtime, while material damage is estimated in hundreds of thousands of hryvnia. One of the weakest units of these mills are the discharge grids and scoops of the cochlear feeder, the durability of which reaches 5.5...6 months and 1.0...1.5 months, respectively, with the resource of operation of other parts of the mill 9...12 months. As a result of the analysis of the operating conditions of the gratings and scoops of the MSHR, it was found that the duration of operation and the mechanical properties of these parts depend mainly on the material from which they are made. Steel with a high level of plasticity and toughness (35GFL, 35HNL, 34HNML, etc.) had insufficient wear resistance due to low strength, hardness. Materials with a high level of hardness and strength (60Kh2SML) had a low impact toughness, which was the reason for emergency shutdowns of the mills as a result of breakdowns of parts. The analysis of the mechanical properties of ladles and gratings has established the required level of properties of these parts; σВ ≥ 850 MPa; НВ ≥ 2600 МPa; δ ≥ 8 %; Ψ ≥ 20 %, KCU ≥ 0,20 MJ/m2. The effect of changing the silicon concentration on the mechanical properties and wear resistance of steel containing 1.5% chromium and 0.40% manganese with different carbon contents has been studied. With an increase in the silicon content, the strength and hardness indicators increase. The effect of silicon on the plastic properties of steel, impact strength and wear resistance is nonlinear, with 0.9% manganese in this case, a monotonic decrease is observed not only in plastic properties and toughness, but also in wear resistance. This is explained by the fact that with an increase in the manganese content in steel, the segregation heterogeneity and stability of supercooled austenite increase, leading, after normalization, to the formation of a martensite-like structure. It is shown that in the production of castings operating under conditions of abrasive wear in combination with shock loads, it is advisable to observe the ratio of silicon to carbon 2.0...2.5. Mathematical planning of the experiment made it possible to obtain models that adequately describe the effect of the composition of steel on the level of its mechanical and operational properties. Based on the processing of the data obtained from the «STATISTICA» software package, a wear-resistant economically alloyed steel of the following composition was proposed: 0.45...0.50 % carbon; 1.7...2.0 % chromium; 0.5...0.7 % manganese; 1.2...1.5 % silicon. The use of such a composition of steel for the manufacture of unloading gratings and scoops of snail feeder allowed to increase their service life by 1.5 times by improving performance, and, consequently, reduce the maintenance cycle of ball mills, which increased economic efficiency. Keywords: ball grinding mill, alloy steel, ","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48865763","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}
А. Prіgunova, Y. Zhydkov, V. D. Babiuk, А. G. Borisov, L. Shenevidko
High-strength cast aluminum alloy AM4.5Kd (VAL10) belongs to the Al-Cu system and due to the combination of a high level of physical, mechanical and operational properties, is widely used in high-tech industries and technology: aviation, space, shipbuilding, transport. Products from the alloy AM4.5Kd (VAL10) are obtained by all known methods of casting (in sand molds, in a chill mold, under pressure), differing in cooling rates. This has a significant effect on the structure and properties of the alloy, not only in the as-cast, but also in the heat-treated state, which determines the relevance of scientific work in this direction. The article presents the results of a study of the microstructure of the AM4.5Kd (VAL10) alloy with a change in its cooling rate during the curing process (Vcool.) from 0.4 °C/s to ≥ 105 °C/s. The alloy was melted, refined and, at a temperature of 750°C, poured into molds with different heat sinks. It is shown that an increase in the cooling rate during the hardening process leads to a decrease in the size of structural components, in particular, aluminum (Alα) solid solution crystals and to an increase in their microhardness. At a cooling rate of 0.4 °C/s, corresponding to solidification in a sandy form, primary Alα crystals are formed in the form of coarsened dendrites with an average size slightly larger than 800 μm, along the boundaries of which a fine network of particles of Al3Ti, Al12Mn2Cu phases and Alα+СuАl2 eutectics is formed. With an increase in the cooling rate, the branching of the dendrites and the volume fraction of the finely differentiated eutectic increase, the cooperative growth of phases in which is maintained throughout the entire range of cooling rates studied. The value of the dendritic parameter of the solid solution of aluminum regularly decreases with a practically unchanged shape factor of its crystals, which is almost up to Vcool. ≈ 105 °C/s is from 1.45 to 3.15. A similar dependence of the change in the macrograin size on the cooling rate was not found. Its anomalous growth was recorded at a cooling rate of ≥ 120 °C/s, at which the macrograin size is commensurate with the alloy cooled at a rate of 0.4 °C/s. In the work, such a discrepancy is explained from the standpoint of the theory of the nucleus and growth of crystals. Keywords: cooling rate, microstructure, AM4.5Kd (VAL10), structure formation, macrograin size.
{"title":"Influence of the cooling rate on the structure formation of the AM4.5kd (VAL10) alloy","authors":"А. Prіgunova, Y. Zhydkov, V. D. Babiuk, А. G. Borisov, L. Shenevidko","doi":"10.15407/mom2022.01.029","DOIUrl":"https://doi.org/10.15407/mom2022.01.029","url":null,"abstract":"High-strength cast aluminum alloy AM4.5Kd (VAL10) belongs to the Al-Cu system and due to the combination of a high level of physical, mechanical and operational properties, is widely used in high-tech industries and technology: aviation, space, shipbuilding, transport. Products from the alloy AM4.5Kd (VAL10) are obtained by all known methods of casting (in sand molds, in a chill mold, under pressure), differing in cooling rates. This has a significant effect on the structure and properties of the alloy, not only in the as-cast, but also in the heat-treated state, which determines the relevance of scientific work in this direction. The article presents the results of a study of the microstructure of the AM4.5Kd (VAL10) alloy with a change in its cooling rate during the curing process (Vcool.) from 0.4 °C/s to ≥ 105 °C/s. The alloy was melted, refined and, at a temperature of 750°C, poured into molds with different heat sinks. It is shown that an increase in the cooling rate during the hardening process leads to a decrease in the size of structural components, in particular, aluminum (Alα) solid solution crystals and to an increase in their microhardness. At a cooling rate of 0.4 °C/s, corresponding to solidification in a sandy form, primary Alα crystals are formed in the form of coarsened dendrites with an average size slightly larger than 800 μm, along the boundaries of which a fine network of particles of Al3Ti, Al12Mn2Cu phases and Alα+СuАl2 eutectics is formed. With an increase in the cooling rate, the branching of the dendrites and the volume fraction of the finely differentiated eutectic increase, the cooperative growth of phases in which is maintained throughout the entire range of cooling rates studied. The value of the dendritic parameter of the solid solution of aluminum regularly decreases with a practically unchanged shape factor of its crystals, which is almost up to Vcool. ≈ 105 °C/s is from 1.45 to 3.15. A similar dependence of the change in the macrograin size on the cooling rate was not found. Its anomalous growth was recorded at a cooling rate of ≥ 120 °C/s, at which the macrograin size is commensurate with the alloy cooled at a rate of 0.4 °C/s. In the work, such a discrepancy is explained from the standpoint of the theory of the nucleus and growth of crystals. Keywords: cooling rate, microstructure, AM4.5Kd (VAL10), structure formation, macrograin size.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43720117","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}
Obtaining a homogeneous structure and uniform-phase distribution is critical to a high set of mechanical and operational properties of rolled metal. However, in practice it is not always possible to create metal products with the specified characteristics. In order to determine the morphological features of the structure of rolled carbon steel, a comparative study of carbon steel samples with a carbon content of 0.49 % C and 0.2 % C selected from hot-rolled billets was carried out. The billets of each group were produced under the conditions of the same enterprise, with close temperature-time modes of deformation processing. The main difference was in manufacturing processes of the output continuous cast steel billets. This research shows that with identical normalized chemical composition of steel and the same thermomechanical treatment, the formation of the morphological structure features of hot-rolled steel occurs in a different way. Therefore, we can assume that the liquation, the diffusive mobility of elements is particularly influenced by the content of impurity elements and gases in steel, which leads to a different type of structures in the finished rolled metal. At the same time, these differences are observed in carbon steels with different carbon content. A sample of non-vacuumed OC grade axle steel (0.49 % C) from converter steelmaking has a more homogeneous structure without local areas of pearlite or ferrite accumulation. It was shown that the formation of ferrite rim in the microsegregation areas occurs not only in manganous sulfides, but also arises on the background of the smallest oxide inclusions. There is significant structural heterogeneity in the samples of electric steel, despite the lower sulfur content and gassiness of steel; at the same time, a dense perlite layer is formed around the sulfides. There is also a difference in steel grade 20 (0.2 % C) of different manufacturing processes. The structure is more homogeneous in qualitatively deoxidized vacuum degassed steel; no local areas with different dimensional characteristics were detected. The size of the structural elements is much larger and the structure has mostly large sections of the Widmanstatten ferrite. Since a large number of non-metallic inclusions and gassiness of steel is not a positive factor for providing a high set of properties of metal products, the modes of thermomechanical treatment used today require adjustments depending on the characteristics of steel melting. Keywords: microstructural heterogeneity, ferritic-pearlitic banding, mechanical properties, manganous sulfides.
{"title":"Peculiarities of the formation of heterogeneous structures in carbon steels","authors":"T. Balakhanova, G. Levchenko","doi":"10.15407/mom2022.01.053","DOIUrl":"https://doi.org/10.15407/mom2022.01.053","url":null,"abstract":"Obtaining a homogeneous structure and uniform-phase distribution is critical to a high set of mechanical and operational properties of rolled metal. However, in practice it is not always possible to create metal products with the specified characteristics. In order to determine the morphological features of the structure of rolled carbon steel, a comparative study of carbon steel samples with a carbon content of 0.49 % C and 0.2 % C selected from hot-rolled billets was carried out. The billets of each group were produced under the conditions of the same enterprise, with close temperature-time modes of deformation processing. The main difference was in manufacturing processes of the output continuous cast steel billets. This research shows that with identical normalized chemical composition of steel and the same thermomechanical treatment, the formation of the morphological structure features of hot-rolled steel occurs in a different way. Therefore, we can assume that the liquation, the diffusive mobility of elements is particularly influenced by the content of impurity elements and gases in steel, which leads to a different type of structures in the finished rolled metal. At the same time, these differences are observed in carbon steels with different carbon content. A sample of non-vacuumed OC grade axle steel (0.49 % C) from converter steelmaking has a more homogeneous structure without local areas of pearlite or ferrite accumulation. It was shown that the formation of ferrite rim in the microsegregation areas occurs not only in manganous sulfides, but also arises on the background of the smallest oxide inclusions. There is significant structural heterogeneity in the samples of electric steel, despite the lower sulfur content and gassiness of steel; at the same time, a dense perlite layer is formed around the sulfides. There is also a difference in steel grade 20 (0.2 % C) of different manufacturing processes. The structure is more homogeneous in qualitatively deoxidized vacuum degassed steel; no local areas with different dimensional characteristics were detected. The size of the structural elements is much larger and the structure has mostly large sections of the Widmanstatten ferrite. Since a large number of non-metallic inclusions and gassiness of steel is not a positive factor for providing a high set of properties of metal products, the modes of thermomechanical treatment used today require adjustments depending on the characteristics of steel melting. Keywords: microstructural heterogeneity, ferritic-pearlitic banding, mechanical properties, manganous sulfides.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48640301","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}
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