In mechanical engineering, the main parameters that determine the use of materials are their operational characteristics, which are determined by mechanical properties. The material must meet the specified parameters of strength, hardness, elasticity and viscosity. Only the method of determining the hardness of the material, in addition to physical methods, allows conducting research without making special samples without destroying the part. At the same time, the factor that the rest of the properties are indirectly related to the hardness parameter is taken into account. The classic definition of the hardness of materials as a mechanical property is the ability of a solid body to resist the penetration of another harder body into it. Based on this, the hardness is characterized by the value, that is, the volume by which a harder body penetrates the material under study. Currently, there are extremely many methods for determining hardness, but all of them are side effects. Even the most standardized methods take into account the area of interaction between the indenter and the test material, which is highly dependent on the geometry of the indenter and the load. The volumetric characteristic of hardness, which is proposed in this work, takes into account both the load and the geometry of the indenter. In modern metallurgy, it is customary to compare the units of all hardness measurement methods for their practical comparison, depending on the scale factor, by converting their values to such generally accepted methods as Brinell, Rockwell, or Vickers. For research, the authors used the developed methodology, which involves the use of a single characteristic - volume hardness of materials. This characteristic does not require the use of transitional tables of hardness units obtained by different methods. Volumetric hardness, unlike other methods, really corresponds to the physical content of the hardness characteristic, as the ability of a material to resist the incorporation of another, harder material into it. It is characterized by the displaced specific volume. Mathematically, it is characterized by the effort required to displace one cubic millimeter of a substance. The purpose of this work was a visual demonstration of the possibility of applying the concept of volume hardness as a characteristic that corresponds to the physical meaning of this property of materials. Show that the proposed technique makes it possible to compare the hardness of materials with a wide range of properties. To ensure a wide range of research, materials with different internal structures were selected, depending on the chemical composition of the alloys, as well as the mode of chemical and thermal treatment. Comparisons of the results obtained by different methods of hardness research were made and it was shown that the bulk hardness can clearly characterize and generalize these results. Keywords: volumetric hardness, mechanical properties, complex alloying, steel
{"title":"Structure and volumetric hardness of materials","authors":"Semenovskyi О. E., Mykhnian O. V.","doi":"10.15407/mom2022.04.048","DOIUrl":"https://doi.org/10.15407/mom2022.04.048","url":null,"abstract":"In mechanical engineering, the main parameters that determine the use of materials are their operational characteristics, which are determined by mechanical properties. The material must meet the specified parameters of strength, hardness, elasticity and viscosity. Only the method of determining the hardness of the material, in addition to physical methods, allows conducting research without making special samples without destroying the part. At the same time, the factor that the rest of the properties are indirectly related to the hardness parameter is taken into account. The classic definition of the hardness of materials as a mechanical property is the ability of a solid body to resist the penetration of another harder body into it. Based on this, the hardness is characterized by the value, that is, the volume by which a harder body penetrates the material under study. Currently, there are extremely many methods for determining hardness, but all of them are side effects. Even the most standardized methods take into account the area of interaction between the indenter and the test material, which is highly dependent on the geometry of the indenter and the load. The volumetric characteristic of hardness, which is proposed in this work, takes into account both the load and the geometry of the indenter. In modern metallurgy, it is customary to compare the units of all hardness measurement methods for their practical comparison, depending on the scale factor, by converting their values to such generally accepted methods as Brinell, Rockwell, or Vickers. For research, the authors used the developed methodology, which involves the use of a single characteristic - volume hardness of materials. This characteristic does not require the use of transitional tables of hardness units obtained by different methods. Volumetric hardness, unlike other methods, really corresponds to the physical content of the hardness characteristic, as the ability of a material to resist the incorporation of another, harder material into it. It is characterized by the displaced specific volume. Mathematically, it is characterized by the effort required to displace one cubic millimeter of a substance. The purpose of this work was a visual demonstration of the possibility of applying the concept of volume hardness as a characteristic that corresponds to the physical meaning of this property of materials. Show that the proposed technique makes it possible to compare the hardness of materials with a wide range of properties. To ensure a wide range of research, materials with different internal structures were selected, depending on the chemical composition of the alloys, as well as the mode of chemical and thermal treatment. Comparisons of the results obtained by different methods of hardness research were made and it was shown that the bulk hardness can clearly characterize and generalize these results. Keywords: volumetric hardness, mechanical properties, complex alloying, steel","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44524463","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 mechanical properties and susceptibility to intergranular corrosion (IGC) of Al-Mg-Si(Cu) aircraft alloys containing 1.4-1.5%Si were studied. A different Mg/Si ratio and a different phase content of Mg2Si and Si, as a consequence, were realized for them by varying the chemical composition. It is shown, that the strength of the alloys increases and the resistance to MGC decreases as the chemical composition of the alloy moves away from the quasi-binary cross-section and the amount of residual silicon Si+ above the limit required for Mg2Si formation is enhanced. Marked No. 2 the strongest alloy and the least corrosion-resistant, at the same time, which has UTS ≥350 MPa and MGC penetration depth of more than 100 μm was determined. It contains 0.7 % Si+ and, among the other experimental alloys, this one is the closest to the upper solubility limit of 1.85 % Mg2Si in aluminum. The negative effect of Cu and Fe on MGC, as well as the temporary delay, if any between quenching and strengthening heat treatment (artificial aging), was demonstrated. A series of isothermal curves, which characterize the strengthening of alloy No. 2 during artificial aging, was obtained, and it is shown, there is no isothermal processing within the temperature range of 145-200 °С, which would increase its resistance to MGC. Analyzing the generally accepted sequence of phase transformations, which takes place during the decomposition of a supersaturated solid solution after quenching, two-stage treatment modes of 145 °С, 4 h + 220 °С, 0.5 h and 145 °С, 2 h + 165 °С, 4 h were found and tested. They provided decreasing the maximum depth of MGC penetration by approximately 1.5-2.5 without significant worsening of the mechanical properties for alloy No. 2. Keywords: aircraft alloys, strength, intergranular corrosion, residual silicon, artificial aging, multi-stage processing.
{"title":"Reducing the sensitivity of high-silicon Al-Mg-Si(Cu) alloys to intergranular corrosion","authors":"Sinchuk А. V., Merkkulov O. E.","doi":"10.15407/mom2022.04.011","DOIUrl":"https://doi.org/10.15407/mom2022.04.011","url":null,"abstract":"The mechanical properties and susceptibility to intergranular corrosion (IGC) of Al-Mg-Si(Cu) aircraft alloys containing 1.4-1.5%Si were studied. A different Mg/Si ratio and a different phase content of Mg2Si and Si, as a consequence, were realized for them by varying the chemical composition. It is shown, that the strength of the alloys increases and the resistance to MGC decreases as the chemical composition of the alloy moves away from the quasi-binary cross-section and the amount of residual silicon Si+ above the limit required for Mg2Si formation is enhanced. Marked No. 2 the strongest alloy and the least corrosion-resistant, at the same time, which has UTS ≥350 MPa and MGC penetration depth of more than 100 μm was determined. It contains 0.7 % Si+ and, among the other experimental alloys, this one is the closest to the upper solubility limit of 1.85 % Mg2Si in aluminum. The negative effect of Cu and Fe on MGC, as well as the temporary delay, if any between quenching and strengthening heat treatment (artificial aging), was demonstrated. A series of isothermal curves, which characterize the strengthening of alloy No. 2 during artificial aging, was obtained, and it is shown, there is no isothermal processing within the temperature range of 145-200 °С, which would increase its resistance to MGC. Analyzing the generally accepted sequence of phase transformations, which takes place during the decomposition of a supersaturated solid solution after quenching, two-stage treatment modes of 145 °С, 4 h + 220 °С, 0.5 h and 145 °С, 2 h + 165 °С, 4 h were found and tested. They provided decreasing the maximum depth of MGC penetration by approximately 1.5-2.5 without significant worsening of the mechanical properties for alloy No. 2. Keywords: aircraft alloys, strength, intergranular corrosion, residual silicon, artificial aging, multi-stage processing.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41677816","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}
Shalevska I. A., Kvasnytska Iu. H., Kvasnytska K. H.
The article presents the results of research conducted to check the effect of alloying with manganese and molybdenum and modification of high-chromium cast iron with niobium on the formation of its structure during heat treatment. The effect of heat treatment in the temperature range of 450...900°C and normalization at a temperature of 1000...1200°C on structural transformations, hardness and wear resistance of complex alloyed high chromium cast irons was studied. The research material was samples of cast iron (1.8...2.3% C and 12...20% Cr), doped with manganese, molybdenum (2...4% Mn, 0.6...1.2% Mo) and modified with niobium, it was checked microstructures of samples in the cast state and when heated to temperatures of 650 °C and 780 °C with the following content of elements: С – 2.07 %, Cr – 19.7 %, Mn – 3.55 %, Mo – 1.02 %, Nb – 0.3%, Si – 0.6%. Experiments were carried out in the temperature ranges: 450...500 °C; 500...550 °C; 600...650 °C; 700...900°C; 1000...1200 °C with varying holding time from four to twenty hours. The hardness of cast iron is 40-42 HRC. The microhardness of austenite is 340-420 Nμ. The influence of the degree of alloying and the number of individual alloying elements in the alloy on the beginning of the austenite transformation was established. When heated to 500...550 °C with an increase in the chromium content in the alloys, the time to the beginning of the transformation increases. In alloys with a chromium content of 17.7%, the beginning of transformation was observed after 4 hours, while in alloys with a chromium content of about 22%, the beginning of transformation was detected after 9...10 hours of exposure. During normalization (1050...1100°C), the Me7C3 → Me23C6 transition process occurs faster in chromium cast irons with molybdenum than in alloys with tungsten. With a molybdenum content of more than 0.6%, Me7C3 carbide is completely transformed into Me23C6, which in the range of 0.6...1.2% is the only carbide phase. It was found that the amount of martensite depends on both the heating temperature and the cooling rate. When cooling at a rate of 30 °C/h, less martensite is formed in the cast iron structure than when cooling at a faster rate of 70 °C/h. It was found that in the cast state, the structure of high-chromium cast irons consists of austenite and austenite-chromium carbide eutectic, which contains trigonal carbide (Cr,Fe)7С3. As a result of heating cast iron in the temperature range of 450...900°C and normalization at a temperature of 1000...1200°C, austenite has a different ability to disintegrate, and this affects the phase composition of cast irons, their structure and properties. The transformation into austenite begins with the release of a dispersed carbide phase (Cr,Fe)23С6 at a temperature of 650°C. It was determined that the experimental complex-alloyed high-chromium cast irons in the cast state had a hardness of 40...47 HRC, and after normalization at a temperature of 1050...1100°C with a hol
{"title":"Technological solutions for producing quality castings from high chromium iron","authors":"Shalevska I. A., Kvasnytska Iu. H., Kvasnytska K. H.","doi":"10.15407/mom2022.04.022","DOIUrl":"https://doi.org/10.15407/mom2022.04.022","url":null,"abstract":"The article presents the results of research conducted to check the effect of alloying with manganese and molybdenum and modification of high-chromium cast iron with niobium on the formation of its structure during heat treatment. The effect of heat treatment in the temperature range of 450...900°C and normalization at a temperature of 1000...1200°C on structural transformations, hardness and wear resistance of complex alloyed high chromium cast irons was studied. The research material was samples of cast iron (1.8...2.3% C and 12...20% Cr), doped with manganese, molybdenum (2...4% Mn, 0.6...1.2% Mo) and modified with niobium, it was checked microstructures of samples in the cast state and when heated to temperatures of 650 °C and 780 °C with the following content of elements: С – 2.07 %, Cr – 19.7 %, Mn – 3.55 %, Mo – 1.02 %, Nb – 0.3%, Si – 0.6%. Experiments were carried out in the temperature ranges: 450...500 °C; 500...550 °C; 600...650 °C; 700...900°C; 1000...1200 °C with varying holding time from four to twenty hours. The hardness of cast iron is 40-42 HRC. The microhardness of austenite is 340-420 Nμ. The influence of the degree of alloying and the number of individual alloying elements in the alloy on the beginning of the austenite transformation was established. When heated to 500...550 °C with an increase in the chromium content in the alloys, the time to the beginning of the transformation increases. In alloys with a chromium content of 17.7%, the beginning of transformation was observed after 4 hours, while in alloys with a chromium content of about 22%, the beginning of transformation was detected after 9...10 hours of exposure. During normalization (1050...1100°C), the Me7C3 → Me23C6 transition process occurs faster in chromium cast irons with molybdenum than in alloys with tungsten. With a molybdenum content of more than 0.6%, Me7C3 carbide is completely transformed into Me23C6, which in the range of 0.6...1.2% is the only carbide phase. It was found that the amount of martensite depends on both the heating temperature and the cooling rate. When cooling at a rate of 30 °C/h, less martensite is formed in the cast iron structure than when cooling at a faster rate of 70 °C/h. It was found that in the cast state, the structure of high-chromium cast irons consists of austenite and austenite-chromium carbide eutectic, which contains trigonal carbide (Cr,Fe)7С3. As a result of heating cast iron in the temperature range of 450...900°C and normalization at a temperature of 1000...1200°C, austenite has a different ability to disintegrate, and this affects the phase composition of cast irons, their structure and properties. The transformation into austenite begins with the release of a dispersed carbide phase (Cr,Fe)23С6 at a temperature of 650°C. It was determined that the experimental complex-alloyed high-chromium cast irons in the cast state had a hardness of 40...47 HRC, and after normalization at a temperature of 1050...1100°C with a hol","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48644587","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}
Stolbovoy V. O., Srеbryansky G. O., Krivchik L. S., Khokhlova T.S., Pinchuk V. L.
The work is devoted to a topical technical problem - to increase the wear resistance of pipe tools for cold roller rolling of corrosion-resistant pipes, due to its significant cost and difficult working conditions. It is proposed to improve the technology of heat treatment of rolled tools for the production of corrosion-resistant pipes (mandrels, rollers, support strips) from steels 4Х5МФ1С and 60С2ХФА. Instead of the usual technology - tempering with tempering, tempering with tempering and subsequent ionic nitriding in plasma of two-stage vacuum-arc discharge in a modified installation "Bulat-6" in the laboratory of plasma technology. The microstructure of special samples of these steels on a scanning electron microscope (SEM) at different magnifications was studied. Their microhardness was determined using a microhardness tester PMT-3. A comparison of the microhardness of the samples after traditional treatment and the proposed. The wear resistance of the actual tool (mandrels made of 60С2ХФA steel) for cold roller rolling of particularly thin-walled corrosion-resistant pipes was studied directly during industrial tests in the factory. Studies of the microstructure on the REM of the nitrided layer after ion-plasma nitriding revealed a finely dispersed very strong ε-phase. Due to its presence in the surface layer, the surface hardness of nitrided parts increases due to the formation of stable in the process of heating carbides, nitrides, carbonitrides. Steel acquires high hardness on the surface, high wear resistance, high endurance, corrosion resistance. Tests of mandrels in the factory, which were additionally subjected to ionic nitriding, showed an increase in their stability by 25-30%. Also reduced the cost of processing the manufacture of pipes and improved the quality of the inner surface of the pipes (absence of films, cuts and other defects of corrosion-resistant pipes). Replacement of steel 60С2ХФA with secondary hardening steel 4Х5MФ1С for the manufacture of rollers and support bars in addition to improving the quality of the inner surface of the pipes increased the stability of the tool by 2.7-3 times. Keywords: rollers, support laths, mandrels, cold rolling, heat treatment, ionic nitriding.
{"title":"Strengthening of the tool for cold roller rolling of corrosion-resistant pipes","authors":"Stolbovoy V. O., Srеbryansky G. O., Krivchik L. S., Khokhlova T.S., Pinchuk V. L.","doi":"10.15407/mom2022.04.040","DOIUrl":"https://doi.org/10.15407/mom2022.04.040","url":null,"abstract":"The work is devoted to a topical technical problem - to increase the wear resistance of pipe tools for cold roller rolling of corrosion-resistant pipes, due to its significant cost and difficult working conditions. It is proposed to improve the technology of heat treatment of rolled tools for the production of corrosion-resistant pipes (mandrels, rollers, support strips) from steels 4Х5МФ1С and 60С2ХФА. Instead of the usual technology - tempering with tempering, tempering with tempering and subsequent ionic nitriding in plasma of two-stage vacuum-arc discharge in a modified installation \"Bulat-6\" in the laboratory of plasma technology. The microstructure of special samples of these steels on a scanning electron microscope (SEM) at different magnifications was studied. Their microhardness was determined using a microhardness tester PMT-3. A comparison of the microhardness of the samples after traditional treatment and the proposed. The wear resistance of the actual tool (mandrels made of 60С2ХФA steel) for cold roller rolling of particularly thin-walled corrosion-resistant pipes was studied directly during industrial tests in the factory. Studies of the microstructure on the REM of the nitrided layer after ion-plasma nitriding revealed a finely dispersed very strong ε-phase. Due to its presence in the surface layer, the surface hardness of nitrided parts increases due to the formation of stable in the process of heating carbides, nitrides, carbonitrides. Steel acquires high hardness on the surface, high wear resistance, high endurance, corrosion resistance. Tests of mandrels in the factory, which were additionally subjected to ionic nitriding, showed an increase in their stability by 25-30%. Also reduced the cost of processing the manufacture of pipes and improved the quality of the inner surface of the pipes (absence of films, cuts and other defects of corrosion-resistant pipes). Replacement of steel 60С2ХФA with secondary hardening steel 4Х5MФ1С for the manufacture of rollers and support bars in addition to improving the quality of the inner surface of the pipes increased the stability of the tool by 2.7-3 times. Keywords: rollers, support laths, mandrels, cold rolling, heat treatment, ionic nitriding.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49094974","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, L. Shenevidko, T. G. Tsir
To management the structure, mechanical and operational properties of the high-strength cast aluminum alloy АМ4.5Кд (ВАЛ10), the work uses a modification method based on the principle of structural inheritance, using rapidly cooled (Vcool. ≥ 10^5 °С/s) fine-crystal ligatures AlTi5 and AlZr10, and as well as ligatures of the chemical composition of the base alloy with nanoscale size of intermetallics and Alα crystals. Studies have shown that the introduction of fine-crystalline additives into the melt leads to a transition from a dendritic to a non-dendritic structure, a significant decrease in the size of the crystals of the Alα solid solution, and an increase in its degree of supersaturation. The microstructure becomes more uniform - the difference between the maximum and minimum size of the grains decreases. The most effective reduction of the grain size and the transition from dendritic to non-dendritic structure of the aluminum solid solution at increased cooling rates occurs when alloying with fine-crystal AlTi5 ligature introduced into the melt in terms of pure titanium 0.05-0.15 wt. %. We must think that the main factor of modification by rapidly cooled ligatures is the introduction of a large number of additional crystallization centers into the melt. After T6 heat treatment, the highest strength of AM4.5Kd alloy (VAL10) is achieved when modified with AlZr10 ligature, in particular, with a mass fraction of zirconium of 0.25%. Probably, this is mainly due to the expansion of the region of the solid solution of copper and zirconium in aluminum during high-speed cooling and its subsequent disintegration during heat treatment with the release of strengthening nano-sized CuAl2 and Al3Zr phases. Tribological studies of AM4.5Kd alloy (VAL10) were carried out. The alloy modified with fine crystal ligature of the base alloy composition in the amount of 12 wt.% has the highest wear resistance. Keywords: fine crystal ligatures, AM4.5Kd (VAL10), modification, microstructure, strength, wear resistance.
{"title":"Management the structure and properties of cast aluminum alloy AM4.5Kd (VAL10) by modification with fine crystalline ligatures","authors":"А. Prіgunova, Y. Zhydkov, V. D. Babiuk, L. Shenevidko, T. G. Tsir","doi":"10.15407/mom2022.03.003","DOIUrl":"https://doi.org/10.15407/mom2022.03.003","url":null,"abstract":"To management the structure, mechanical and operational properties of the high-strength cast aluminum alloy АМ4.5Кд (ВАЛ10), the work uses a modification method based on the principle of structural inheritance, using rapidly cooled (Vcool. ≥ 10^5 °С/s) fine-crystal ligatures AlTi5 and AlZr10, and as well as ligatures of the chemical composition of the base alloy with nanoscale size of intermetallics and Alα crystals. Studies have shown that the introduction of fine-crystalline additives into the melt leads to a transition from a dendritic to a non-dendritic structure, a significant decrease in the size of the crystals of the Alα solid solution, and an increase in its degree of supersaturation. The microstructure becomes more uniform - the difference between the maximum and minimum size of the grains decreases. The most effective reduction of the grain size and the transition from dendritic to non-dendritic structure of the aluminum solid solution at increased cooling rates occurs when alloying with fine-crystal AlTi5 ligature introduced into the melt in terms of pure titanium 0.05-0.15 wt. %. We must think that the main factor of modification by rapidly cooled ligatures is the introduction of a large number of additional crystallization centers into the melt. After T6 heat treatment, the highest strength of AM4.5Kd alloy (VAL10) is achieved when modified with AlZr10 ligature, in particular, with a mass fraction of zirconium of 0.25%. Probably, this is mainly due to the expansion of the region of the solid solution of copper and zirconium in aluminum during high-speed cooling and its subsequent disintegration during heat treatment with the release of strengthening nano-sized CuAl2 and Al3Zr phases. Tribological studies of AM4.5Kd alloy (VAL10) were carried out. The alloy modified with fine crystal ligature of the base alloy composition in the amount of 12 wt.% has the highest wear resistance. Keywords: fine crystal ligatures, AM4.5Kd (VAL10), modification, microstructure, strength, wear resistance.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41844116","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 the paper, the results of the investigation of the connection between the content of non-metallic inclusions in the metal structure and the fractal dimension on the example of welds of high-strength, low-alloy steels. The work expediency is justified by the fact that, although the quality of the metal is determined by its structure, currently the relationship between such parameters of the microstructure as the grain composition, the microstructure of the interphase boundaries (for welded joints) and the performance of the structure/object under load conditions during exploitation seems too complex and ambiguous for theoretical and phenomenological description. There is no comprehensive understanding of the mechanisms and factors that control the formation of microstructures during phase transformations, especially in the conditions of electric arc welding, which are far from equilibrium characteristicsat the present time. Traditional concepts based on the principles of equilibrium thermodynamics and it doesn’t allow, in particular, to answer questions about the reasons for the appearance of one or another morphology of the isolated phases, as well as to adequately assess the determining role of kinetic factors in the problem of the formation of the structural state.The most difficult part of the problem isthe dependence on the cooling trajectory, which even in simpler cases, closer to equilibrium conditions compared to welding processes. Management of the structure formation of welds and determination of the location of failure in existing structures are connected with the need for a correct description of the structure. The complexity of the structure of real metals or welds is the main obstacle to the synthesis of adequate models for computer-aided design of the structure and prediction of their properties. Fractal formalism, in particular, fractal and multifractal parameterization of structures, can in principle become the basis for choosing adequate numerical models of structures of real welds, necessary for computer design of structures and prediction of their properties. The influence of non-metallic inclusions can have a negative character and even pose a serious danger, since the stress concentration can exceed the limit values for the material and the inclusion, therefore, can become a focus of destruction. Keywords: fractal, inclusion, microstructure, inoculants, dimensionality, synergy.
{"title":"Fractal dimension and multifractal analysis of the welds of metal structure","authors":"V. V. Holovko, O. Shtofel","doi":"10.15407/mom2022.03.051","DOIUrl":"https://doi.org/10.15407/mom2022.03.051","url":null,"abstract":"In the paper, the results of the investigation of the connection between the content of non-metallic inclusions in the metal structure and the fractal dimension on the example of welds of high-strength, low-alloy steels. The work expediency is justified by the fact that, although the quality of the metal is determined by its structure, currently the relationship between such parameters of the microstructure as the grain composition, the microstructure of the interphase boundaries (for welded joints) and the performance of the structure/object under load conditions during exploitation seems too complex and ambiguous for theoretical and phenomenological description. There is no comprehensive understanding of the mechanisms and factors that control the formation of microstructures during phase transformations, especially in the conditions of electric arc welding, which are far from equilibrium characteristicsat the present time. Traditional concepts based on the principles of equilibrium thermodynamics and it doesn’t allow, in particular, to answer questions about the reasons for the appearance of one or another morphology of the isolated phases, as well as to adequately assess the determining role of kinetic factors in the problem of the formation of the structural state.The most difficult part of the problem isthe dependence on the cooling trajectory, which even in simpler cases, closer to equilibrium conditions compared to welding processes. Management of the structure formation of welds and determination of the location of failure in existing structures are connected with the need for a correct description of the structure. The complexity of the structure of real metals or welds is the main obstacle to the synthesis of adequate models for computer-aided design of the structure and prediction of their properties. Fractal formalism, in particular, fractal and multifractal parameterization of structures, can in principle become the basis for choosing adequate numerical models of structures of real welds, necessary for computer design of structures and prediction of their properties. The influence of non-metallic inclusions can have a negative character and even pose a serious danger, since the stress concentration can exceed the limit values for the material and the inclusion, therefore, can become a focus of destruction. Keywords: fractal, inclusion, microstructure, inoculants, dimensionality, synergy.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41994013","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 article presents results of studies of contamination of metal of undeformed continuously cast billets (CCB) for boiler tubes from carbon steel supplied by various manufacturers with non-metallic inclusions. Contamination was investigated by metallographic means using methods of observation under a microscope in light and dark fields of vision in polarized light. Application of these methods has made it possible to determine the inclusion types (silicates, oxides, sulfides) with high probability based on optical properties (color, transparency, etc.). Shape, size and type of inclusions and the nature of their location along the billet cross-section were determined for the data set of actual level of contamination of the CCB metal with non-metallic inclusions. In addition, the methods Sh and L according to DSTU 8966 were used. To determine the number, dimensions and types of inclusions, an automated control method using the VIDEOTEST-METAL 1.0 software was also used for the Axiovert 200MAT microscope. Composition of some non-metallic inclusions was studied by means of X-ray spectral microanalysis using the MS-46 microprobe of the Cameca Co. (France). It was established that irregular and rounded silicates of both homogeneous and heterogeneous composition (including individual large ones up to 150 μm in size) are main types of inclusions in metal of continuously cast billets. In most cases, these inclusions are located in axial and peripheral zones along the CCB section. Intermittent film precipitation of non-metallic inclusions of varying degrees of dispersion (mainly of small size) which can have a negative effect on service characteristics of tubes made from such CCB was also detected. The study results have important scientific and practical significance in conditions of wide use of such CCB in the production of tubes of responsible purpose. The obtained study results will make it possible to further develop an advanced methodology of assessing the contamination of non-deformed continuously cast billets (with scale) with non-metallic inclusions in their metal and introduce them in regulatory documents on the CCB. The results of studies of metal contamination with non-metallic inclusions will also be useful for improving the CCB production technology with the aim of producing boiler tubes of high operational reliability. Keywords: undeformed continuous cast tube billet, non-metallic inclusions, silicates, film precipitation of non-metallic inclusions.
{"title":"Non-metallic inclusions in metal of continuously cast billets for boiler tubes","authors":"L. Opryshko, T. Golovnyak","doi":"10.15407/mom2022.03.041","DOIUrl":"https://doi.org/10.15407/mom2022.03.041","url":null,"abstract":"The article presents results of studies of contamination of metal of undeformed continuously cast billets (CCB) for boiler tubes from carbon steel supplied by various manufacturers with non-metallic inclusions. Contamination was investigated by metallographic means using methods of observation under a microscope in light and dark fields of vision in polarized light. Application of these methods has made it possible to determine the inclusion types (silicates, oxides, sulfides) with high probability based on optical properties (color, transparency, etc.). Shape, size and type of inclusions and the nature of their location along the billet cross-section were determined for the data set of actual level of contamination of the CCB metal with non-metallic inclusions. In addition, the methods Sh and L according to DSTU 8966 were used. To determine the number, dimensions and types of inclusions, an automated control method using the VIDEOTEST-METAL 1.0 software was also used for the Axiovert 200MAT microscope. Composition of some non-metallic inclusions was studied by means of X-ray spectral microanalysis using the MS-46 microprobe of the Cameca Co. (France). It was established that irregular and rounded silicates of both homogeneous and heterogeneous composition (including individual large ones up to 150 μm in size) are main types of inclusions in metal of continuously cast billets. In most cases, these inclusions are located in axial and peripheral zones along the CCB section. Intermittent film precipitation of non-metallic inclusions of varying degrees of dispersion (mainly of small size) which can have a negative effect on service characteristics of tubes made from such CCB was also detected. The study results have important scientific and practical significance in conditions of wide use of such CCB in the production of tubes of responsible purpose. The obtained study results will make it possible to further develop an advanced methodology of assessing the contamination of non-deformed continuously cast billets (with scale) with non-metallic inclusions in their metal and introduce them in regulatory documents on the CCB. The results of studies of metal contamination with non-metallic inclusions will also be useful for improving the CCB production technology with the aim of producing boiler tubes of high operational reliability. Keywords: undeformed continuous cast tube billet, non-metallic inclusions, silicates, film precipitation of non-metallic inclusions.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45539139","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 highlights modern ideas about the features of the processes of crystallization and structure formation in the volume of steel castings, depending on the temperature and time conditions for cooling the melt and cooling the castings, as well as the technological prehistory of charge materials. The analysis of the influence of modification and thermokinetic conditions of crystallization and cooling of steel castings is carried out, taking into account the chemical composition of steels at each stage of the technological cycle for producing cast products. At the stage of selecting charge materials, the conditions for preserving certain metallogenetic features of the initial charge in the structure of steel castings are considered, the existence of an equilibrium temperature (Te), when overheated above which heredity is lost, is considered. Due to this, the possibility of using secondary metal to improve the casting properties without changing their chemical composition is shown. The influence of temperature and time parameters in the pre-crystallization period, namely, the melt overheating temperature, the duration of isothermal treatment and the rate of its subsequent cooling, on the structure formation and properties of steel castings, including taking into account the metallogenetic features of the initial charge, is analyzed. Regularities of the influence of the temperature-time conditions of crystallization in the temperature range of the solid-liquid state on the nature of nucleation and structure formation during the crystallization of steel castings are shown. The features of structure formation and the formation of properties in steel castings under conditions of temperature-kinetic influence after their hardening are determined. And also considered the prospects for obtaining castings with a gradient structure to improve the special properties of cast products. The considered approaches to improve the quality and properties of steel castings open up the prospect of creating new technological solutions and automating technological processes for producing cast products with a predictable set of properties at or above the level of properties of similar rolled products. Keywords: castings, charge, heredity, equilibrium temperature, modification, crystallization, cooling rate, thermal treatment.
{"title":"Structure formation of steel castings depending on the temperature-time parameters of melting and crystallization","authors":"S. Kondratyuk, V. I. Veis, Z. Parkhomchuk","doi":"10.15407/mom2022.03.018","DOIUrl":"https://doi.org/10.15407/mom2022.03.018","url":null,"abstract":"The paper highlights modern ideas about the features of the processes of crystallization and structure formation in the volume of steel castings, depending on the temperature and time conditions for cooling the melt and cooling the castings, as well as the technological prehistory of charge materials. The analysis of the influence of modification and thermokinetic conditions of crystallization and cooling of steel castings is carried out, taking into account the chemical composition of steels at each stage of the technological cycle for producing cast products. At the stage of selecting charge materials, the conditions for preserving certain metallogenetic features of the initial charge in the structure of steel castings are considered, the existence of an equilibrium temperature (Te), when overheated above which heredity is lost, is considered. Due to this, the possibility of using secondary metal to improve the casting properties without changing their chemical composition is shown. The influence of temperature and time parameters in the pre-crystallization period, namely, the melt overheating temperature, the duration of isothermal treatment and the rate of its subsequent cooling, on the structure formation and properties of steel castings, including taking into account the metallogenetic features of the initial charge, is analyzed. Regularities of the influence of the temperature-time conditions of crystallization in the temperature range of the solid-liquid state on the nature of nucleation and structure formation during the crystallization of steel castings are shown. The features of structure formation and the formation of properties in steel castings under conditions of temperature-kinetic influence after their hardening are determined. And also considered the prospects for obtaining castings with a gradient structure to improve the special properties of cast products. The considered approaches to improve the quality and properties of steel castings open up the prospect of creating new technological solutions and automating technological processes for producing cast products with a predictable set of properties at or above the level of properties of similar rolled products. Keywords: castings, charge, heredity, equilibrium temperature, modification, crystallization, cooling rate, thermal treatment.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45682205","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 studying the cold resistance of cast stainless steels of austenitic grade and developed mathematical models showing the effect of cerium, boron, vanadium and copper on cold resistance, which is associated with austenite grain size, carbide phase and ferrite content in austenite after quenching, particle volumes, size and distance between particles of oxides, sulfides, titanium carbonitrides and the total content of non-metallic inclusions in cast stainless steel. It was established that with complex microalloying and modification of Ce, B, V and Cu, the impact toughness of stainless steels increases by 2.7-3.1 times, as a result of the increase of nucleation and crack propagation work. It showed that the crack nucleation and their development is associated with non-metallic inclusions, while in the original steels around non-metallic inclusions significant zones of brittle failure are observed, and in the fracture of complex microalloyed and modified steels there are practically no areas of brittle failure around non-metallic inclusions. It was established that the impact toughness and crack initiation and propagation of the investigated stainless steels are determined by the patterns of changes in such structural factors as the size of the austenite grain, the content of the carbide phase and ferrite in the austenite after quenching, the volume fraction, the size and distance between oxide particles, titanium sulfides and carbonitrides, as well as the total content of non-metallic inclusions. Mathematical models of the influence of structural factors have been developed, which show the predominant influence of non-metallic inclusions on the process of destruction of stainless steels under dynamic loads, in comparison with other structure characteristics, in conditions of negative temperatures is shown. It is established that the mechanism of influence of Ce, B, V and Cu on this process is connected, mainly, with dispersion of oxides and their more homogeneous distribution. Keywords: steel, toughness, fracture work, crack formation, crack propagation, modification.
{"title":"The influence of modification on the fracture of austenitic stainless steels under dynamic loads","authors":"Y. Aftandiliants","doi":"10.15407/mom2022.03.034","DOIUrl":"https://doi.org/10.15407/mom2022.03.034","url":null,"abstract":"The paper presents the results of studying the cold resistance of cast stainless steels of austenitic grade and developed mathematical models showing the effect of cerium, boron, vanadium and copper on cold resistance, which is associated with austenite grain size, carbide phase and ferrite content in austenite after quenching, particle volumes, size and distance between particles of oxides, sulfides, titanium carbonitrides and the total content of non-metallic inclusions in cast stainless steel. It was established that with complex microalloying and modification of Ce, B, V and Cu, the impact toughness of stainless steels increases by 2.7-3.1 times, as a result of the increase of nucleation and crack propagation work. It showed that the crack nucleation and their development is associated with non-metallic inclusions, while in the original steels around non-metallic inclusions significant zones of brittle failure are observed, and in the fracture of complex microalloyed and modified steels there are practically no areas of brittle failure around non-metallic inclusions. It was established that the impact toughness and crack initiation and propagation of the investigated stainless steels are determined by the patterns of changes in such structural factors as the size of the austenite grain, the content of the carbide phase and ferrite in the austenite after quenching, the volume fraction, the size and distance between oxide particles, titanium sulfides and carbonitrides, as well as the total content of non-metallic inclusions. Mathematical models of the influence of structural factors have been developed, which show the predominant influence of non-metallic inclusions on the process of destruction of stainless steels under dynamic loads, in comparison with other structure characteristics, in conditions of negative temperatures is shown. It is established that the mechanism of influence of Ce, B, V and Cu on this process is connected, mainly, with dispersion of oxides and their more homogeneous distribution. Keywords: steel, toughness, fracture work, crack formation, crack propagation, modification.","PeriodicalId":33600,"journal":{"name":"Metaloznavstvo ta obrobka metaliv","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47032202","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}
Experimental studies of the method of thixocasting of AK7ч hypoeutectic silumin using cylindrical billets with different initial prepared structure (dendritic and non-dendritic – rosette-like and globular) of the primary solid phase were carried out. It is shown that after casting using billets with the initial dendritic structure of aluminum solid solution, the structure in shaped castings remains dendritic. At the same time, a certain number of destroyed dendrites are observed in the structure, predominantly melted. The thixocasting of the hypoeutectic silumin AK7ч using billets with the initial rosette-like structure of primary aluminum crystals ensures the production of shaped castings with a globular structure of the primary phase with a globular size of 80–100 μm. At the same time resulting the globular structure of the primary solid phase in castings is homogeneous and evenly distributed over the entire cross section. Thixocasting of silumin AK7ч using billets with the initial globular structure of the primary solid phase does not lead to a change of the structure of the casting. This slightly increases the size of the globules in the casting. Eutectic colonies in shaped castings obtained by thixocasting are characterized by a higher degree of differentiation compared to the initial structures of billets. Determination of mechanical properties showed an increased plasticity of the investigated hypoeutectic silumin in castings obtained after thixocasting without additional hardening heat treatment. Keywords: thixocasting, hypoeutectic silumin, non-dendritic structure, globular structure, rosette-like structure, solid-liquid billet, shaped casting.
{"title":"Obtaining castings from hypoeutectic silumins by the method of thixocasting","authors":"A. Neduzhyi","doi":"10.15407/mom2022.02.038","DOIUrl":"https://doi.org/10.15407/mom2022.02.038","url":null,"abstract":"Experimental studies of the method of thixocasting of AK7ч hypoeutectic silumin using cylindrical billets with different initial prepared structure (dendritic and non-dendritic – rosette-like and globular) of the primary solid phase were carried out. It is shown that after casting using billets with the initial dendritic structure of aluminum solid solution, the structure in shaped castings remains dendritic. At the same time, a certain number of destroyed dendrites are observed in the structure, predominantly melted. The thixocasting of the hypoeutectic silumin AK7ч using billets with the initial rosette-like structure of primary aluminum crystals ensures the production of shaped castings with a globular structure of the primary phase with a globular size of 80–100 μm. At the same time resulting the globular structure of the primary solid phase in castings is homogeneous and evenly distributed over the entire cross section. Thixocasting of silumin AK7ч using billets with the initial globular structure of the primary solid phase does not lead to a change of the structure of the casting. This slightly increases the size of the globules in the casting. Eutectic colonies in shaped castings obtained by thixocasting are characterized by a higher degree of differentiation compared to the initial structures of billets. Determination of mechanical properties showed an increased plasticity of the investigated hypoeutectic silumin in castings obtained after thixocasting without additional hardening heat treatment. Keywords: thixocasting, hypoeutectic silumin, non-dendritic structure, globular structure, rosette-like structure, solid-liquid billet, shaped casting.","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":"49207211","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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