Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. Th... more Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. This chapter presents a general algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging parts. Example of using this algorithm also is illustrated. The results obtained applying the proposed algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging conclude that it is a suitable method, which enables to get several alternatives for shape and number of intermediate stages and to select the most appropriate case for specific part. In addition, the algorithm is flexible and addition can be done, especially in connection with the criterions for necessity of intermediate steps.
It is well known that PV thin films can be deposited by an extensive range of more or less expens... more It is well known that PV thin films can be deposited by an extensive range of more or less expensive and complicated techniques (such as sputtering, chemical vapor deposition (CVD), physical vapor deposition (PVD), pulsed laser deposition, atomic layer deposition (ALD)). The present paper focuses on TCO layers applied by chosen techniques, including mainly the ALD and CVD methods. Thin layers of transparent conductive oxides constitute a well-known group of materials with unique properties. Oxides such as ZnO, SnO 2 , and In 2 O 3 are the most significant materials of this type; some of them are discussed in the paper. From the application point of view in the photovoltaic industry, the goal is to apply a method that will provide the highest value of electric charge conductivity while maintaining the minimum value of absorption in the layer and a reduced value of the reflection coefficient. The implementation of significant achievements in the coming decade is for developing guidelines for metallization processes and TCO layers deposited by the ALD method. The work contains chosen engineering processes, including the fabrication of transparent conductive oxides (TCO) thin films applied to silicon substrates by ALD and CVD for application as emitter conductive coatings in photovoltaic structures and the fabrication front metallization of solar cell using different techniques, including among others laser techniques. Moreover, the work also contains predictions about solar cells, which will be among the most prevalent solar cells in mass production using thin-and thick-film technology.
Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. Th... more Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. This chapter presents a general algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging parts. Example of using this algorithm also is illustrated. The results obtained applying the proposed algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging conclude that it is a suitable method, which enables to get several alternatives for shape and number of intermediate stages and to select the most appropriate case for specific part. In addition, the algorithm is flexible and addition can be done, especially in connection with the criterions for necessity of intermediate steps.
НАУЧНИ ТРУДОВЕ НА РУСЕНСКИЯ УНИВЕРСИТЕТ - 2010, том 49, серия 2 - 60 - Симулиране на процеси на о... more НАУЧНИ ТРУДОВЕ НА РУСЕНСКИЯ УНИВЕРСИТЕТ - 2010, том 49, серия 2 - 60 - Симулиране на процеси на обемно деформиране по метода на крайните елементиВалентин Гагов, Росен Радев, Борис Томов ... [18] Гагов В., Р. Радев, Е. Янков, Д. Господинов. ...
It is well known that PV thin films can be deposited by an extensive range of more or less expens... more It is well known that PV thin films can be deposited by an extensive range of more or less expensive and complicated techniques (such as sputtering, chemical vapor deposition (CVD), physical vapor deposition (PVD), pulsed laser deposition, atomic layer deposition (ALD)). The present paper focuses on TCO layers applied by chosen techniques, including mainly the ALD and CVD methods. Thin layers of transparent conductive oxides constitute a well-known group of materials with unique properties. Oxides such as ZnO, SnO2, and In2O3 are the most significant materials of this type; some of them are discussed in the paper. From the application point of view in the photovoltaic industry, the goal is to apply a method that will provide the highest value of electric charge conductivity while maintaining the minimum value of absorption in the layer and a reduced value of the reflection coefficient. The implementation of significant achievements in the coming decade is for developing guidelines f...
Stirring material during the process of friction stir welding, as well as the temperature at whic... more Stirring material during the process of friction stir welding, as well as the temperature at which the joining process is carried out are the main factors that determine the possibility to produce weldments with defined mechanical properties. While the shape and the dimensions of the instrument are primarily related to the blending manner, the temperature is mostly dependent on the welding modes. It is known that there is a temperature range for every alloy, at c b e d ce a f a e. T a e e e a e de e a a e e ding zone is exceptionally important. There are different direct and indirect approaches to temperature determination, and the present report looks at the possibility for indirect temperature determination using examination of the changes in mechanical properties of an aluminium alloy EN AW-1050A H24 (EN AW-Al 99.5). For this purpose, the mechanical properties of the alloy after recrystallization annealing at different temperatures were determined and compared to the mechanical properties of the alloy after friction stir welding using different welding modes.
The parts obtained by forging are better than those manufactured by any other metalworking proces... more The parts obtained by forging are better than those manufactured by any other metalworking process in many aspects. This determines their widespread use where human safety and reliability are critically important. Industries such as aerospace, defence, automotive and agriculture, construction, mining are some of the largest customers using forged parts. The design of hot closed-die processes very often requires engineers to deal with two important challenges-the necessity of preform (intermediate) steps and the shape of these intermediate steps. A general design approach for determination of necessity of preforms and their shape at hot closed-die forging is presented in this article.
As the tendency to lower the mass of welded constructions emerges in the last years, the use of h... more As the tendency to lower the mass of welded constructions emerges in the last years, the use of high strength steels finds a wide range of applications in industry, namely, in reliable highly loaded welded constructions. Following the commonly accepted rules, these steels are suitable for welding. The most used welding methods for welding of high strength steels are submerged arc welding and MAG welding. The mechanical properties of weldment of high strength steels will depend on several different welding details, such as cooling time in the range from 800 to 500 °C-t8/5, the used filler materials, welding protection, etc. Nevertheless, data on the influence of joint preparation, and specifically of the weld gap, are limited or absent. Joint preparation of high strength steels is typically performed according to EN ISO 9692-1:2013 and EN ISO 9692-2:2001. When the welding gap differs significantly from the standards recommendations, it is of great importance to research and to determine the influence of the weld gap on weldment properties and structure. This study introduces the findings on the influence of joint preparation on some mechanical properties of high strength steel S700MC weldments produced by submerged arc welding.
Currently, heat treatment is the most common and effective method for changing the properties of ... more Currently, heat treatment is the most common and effective method for changing the properties of metals and their alloys. Ferrous alloys most often are heat treated and the most commonly used process of heat treatment is the quenching. At quenching the final structure and material's properties are formed during the fast cooling process. Therefore, the correct choice of cooling conditions is critical for quality of quenched parts. The simulation of quenching is one of the modern approaches for researching the cooling processes. In order to obtain reliable results, the correct input data for simulation are crucial. It is commonly accepted that the heat transfer coefficient (HTC) plays most significant influence on the simulation results. Meanwhile in the specialized literature there are quite different values of HTC even at equal cooling conditions and a few data regarding its influence on the simulation results. The aim of this paper is to determine to what extent the results obtained after simulation of quenching processes are influenced by HTC. Samples of different dimensions and ratios between length and diameter (L/D), made of medium carbon steel (C45 EN 10083), were studied. Results for the influence of HTC together with geometry of the quenched parts, especially samples with different ratio length/diameter (L/D), are presented in the article.
Titanium alloys are known for their good mechanical properties, low density, excellent corrosion ... more Titanium alloys are known for their good mechanical properties, low density, excellent corrosion resistance and low thermal conductivity. These properties define titanium and its alloys as highly suitable for medicine, automotive and aerospace industries. Unfortunately, the thermal cycle during welding of alpha-beta alloys (Ti-6Al-4V) can significantly change their strength, toughness and plasticity. The scope of present work is to investigate the possibility for producing Ti-6Al-4V welds by arc discharge in vacuum and to establish the influence of the welding parameters on dimensions and mechanical properties of the welds. The experiments presented here were carried out in an installation for hollow cathode arc treatment in vacuum. Cylindrical and elliptical tantalum cathodes were used. The welding was carried out without filler material and groove. Tensile test and hardness test of specific welds zones were used for mechanical properties determination. The results, presented in this work, describe the dimensions of the fusion zone and heat affected zone of welds, produced by hollow cathode arc welding using different welding parameters. The mechanical properties of the welds were determined.
The structure of Ti-6Al-4V alloy and Ti-6Al-4V weldments was examined. The welds were produced by... more The structure of Ti-6Al-4V alloy and Ti-6Al-4V weldments was examined. The welds were produced by hollow cathode arc discharge in vacuum using tantalum cathodes and different welding parameters. The corrosion behaviour of Ti-6Al-4V alloy and Ti-6Al-4V welds in solution containing Brwas evaluated quantitatively using potentiodynamic polarization tests. The corrosion behaviour of the base metal and welds was compared. Open circuit potential, pitting potential, corrosion current densities and corrosion rates were determined. The influence of the structure and its change during welding on corrosion behaviour is discussed in the present paper.
Archives of materials science and engineering, Nov 1, 2021
Purpose: The presented research aims to determine the microstructural changes in weldments of com... more Purpose: The presented research aims to determine the microstructural changes in weldments of commercially pure titanium Grade 1 after welding by hollow cathode arc discharge in vacuum and related changes in the corrosion behaviour of the weldments. Design/methodology/approach: Macro and microstructure of weldments were studied using optical microscopy. Corrosion behaviour of untreated Grade 1 and heat-affected zone of weldments of Grade 1 was investigated using electrochemical testing, including open circuit potential measurements and potentiodynamic polarisation. As an aggressive environment, 1 M KBr water solution was used. Findings: Welding by hollow cathode arc discharge in vacuum leads to the formation of a coarse Widmanstätten structure in the heat-affected zone. This imperfect structure results in a passive layer with worsened protective properties, thus increasing the corrosion rate of weldments by up to two orders of magnitude compared to Grade 1 in as-received condition. The passive layer on the welded surfaces did not allow Grade 1 to acquire a stable corrosion potential during potenitodynamic polarization. Research limitations/implications: Titanium and its alloys are passivating metallic materials, and their corrosion resistance depends on the properties of a thin protective surface layer. Changes in the underlying metal microstructure can affect the passivation behaviour of titanium and the properties of this layer. Welding by hollow cathode arc discharge in vacuum alters the microstructure of heat-affected zone, thereby causing Widmanstätten microstructure to form. As the passive layer over that microstructure has worsened protective properties, we suggest additional heat treatment after welding to be applied. Future experimental research on this topic is needed. Originality/value: Welding by hollow cathode arc discharge in vacuum is a welding method allowing weldments to be done in a clean environment and even in space. In the specialised literature, information on the structure and corrosion resistance of weldments of commercially pure titanium Grade 1 welded by hollow cathode arc discharge in vacuum is missing. The present research fills in a tiny part of this gap in our knowledge.
Journal of Materials Processing Technology, Nov 1, 2004
... Object of attention in this paper are some representative examples of forgings from group 1 b... more ... Object of attention in this paper are some representative examples of forgings from group 1 by reason of their large spread in the metalworking industry. 3. Intermediate steps of forging. In the case of closed-die forging process design, the required number of stages which ...
Nowadays, the use of high strength (HS) and ultra-high strength steels (UHS) increases, notably i... more Nowadays, the use of high strength (HS) and ultra-high strength steels (UHS) increases, notably in welded constructions. These steels are mainly exploited in heavy loaded welded constructions such as bridges, cranes and excavators, in pressure vessels, vehicles, ships, drilling rigs etc. working at room or lower temperatures. As the welded constructions have specific requirements, the development of high strength and ultra-high strength steels imposes the need for research on the factors influencing their weldability. Among the possible negative implications are: cold cracks formation, softening of the heat affected zone, brittleness in the coarse grained zone. When complying with the generally accepted rules for welding, HS and UHS are readily welded by all conventional welding methods. Recommendations for welding of steels after normalization, thermo-mechanical treatment and quenching and tempering are given in the standard EN 1011 -1, 2. The use of thermo-mechanically treated (hot-rolled) steels with low carbon equivalent, such as S700MC, allows reduction in time required for welding as the preheating temperature is lowered or even preheating is not necessary. A more pronounced negative effect on the weld quality has the presence of different defects. S700MC can be welded by all conventional methods, and a reduction in the softened zone can be achieved by using appropriate welding parameters. Joint preparation for welding of HS and UHS steels is described in the standards EN ISO 9692-1:2013 and EN ISO 9692-2:2001. Nevertheless, the root gap is often the closing part in constructions and does not comply with the standard recommendations. That is why the effect of the root gap on welds has to be researched. The present work introduces results of a research studying the effect of the root gap on the structure and some mechanical and technological properties of S700MS welds, welded by submerged arc welding.
The structure and the mechanical properties of the high-strength structural martensitic steels us... more The structure and the mechanical properties of the high-strength structural martensitic steels used in manufacturing the mechanism parts subjected to significant cyclic dynamical loads are considered. All the steels have a similar martensitic-bainite structure and a high stability of their mechanical properties. At the same time, their structures are found to contain secondary phases, which can degrade their functional properties. 03Kh11N10M2T maraging steel exhibits fairly high impact toughness for this class of steels despite a brittle character of fracture during bending impact tests.
Friction stir welding is one of the most original methods for welding devised in recent years. As... more Friction stir welding is one of the most original methods for welding devised in recent years. As this welding method possesses advantages compared to conventional fusing welding methods, scientific research on its features and improvement is increasing. The advances in the knowledge of the process of friction stir welding allow its increasing application in different areas, such as aircraft and automotive industries, railway transport, nuclear industries etc. During friction stir welding the joined parts are in a solid state. This welding method is mainly used for joining aluminium and its alloys.The stirring and mixing of the material and the temperature during friction stir welding are the main factors that determine the possibility of obtaining weldments with precise mechanical properties.The present study aims to research the influence of the pin`s configuration on different quality aspects of the weldments at chosen parameters of the welding mode. To achieve this, pins with di...
In the present work, a finite element model of the first stage, plunge, of friction stir welding ... more In the present work, a finite element model of the first stage, plunge, of friction stir welding is considered. The welded parts are flat aluminum 1050 plates. The arbitrary Lagrangian-Eulerian formulation implemented in ABAQUS/Explicit is used. The material model of the welded parts is the Johnson-Cook law, and Coulomb’s law describes the friction between the tool and the weldment. Temperature field during the process is obtained, and the influence of the parameters concerning the algorithmic implementation of the finite element method is established. The simulation results are compared with experimental results obtained for this purpose.
This article examines expanded polytetrafluoroethylene (PTFE) flat gaskets used in the industry t... more This article examines expanded polytetrafluoroethylene (PTFE) flat gaskets used in the industry to seal flange connections that prevent mixing of working fluids and leakage of fluids into the environment. Expanded PTFE gaskets and existing solutions to improve tightness are reviewed. Using test equipment for measuring the mass of gas passed through the gasket per unit time, which is one of the main operating characteristics of the gasket, a comparison of the required contact stress applied to the gasket during installation to achieve the same leakage rates was made. An annular expanded PTFE gasket with locally increased density is presented. Comparative tests were conducted to determine the mass of helium gas passed through the gaskets when changing the density in the sealed area to the inner diameter of the gasket. The results of the tests carried out show an improvement in the sealing ability and indicate a reduction in the mass of passed gas with the application of a lower contac...
Archives of Materials Science and Engineering, 2021
Purpose: The presented research aims to determine the microstructural changes in weldments of com... more Purpose: The presented research aims to determine the microstructural changes in weldments of commercially pure titanium Grade 1 after welding by hollow cathode arc discharge in vacuum and related changes in the corrosion behaviour of the weldments. Design/methodology/approach: Macro and microstructure of weldments were studied using optical microscopy. Corrosion behaviour of untreated Grade 1 and heat-affected zone of weldments of Grade 1 was investigated using electrochemical testing, including open circuit potential measurements and potentiodynamic polarisation. As an aggressive environment, 1 M KBr water solution was used. Findings: Welding by hollow cathode arc discharge in vacuum leads to the formation of a coarse Widmanstätten structure in the heat-affected zone. This imperfect structure results in a passive layer with worsened protective properties, thus increasing the corrosion rate of weldments by up to two orders of magnitude compared to Grade 1 in as-received condition. ...
Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. Th... more Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. This chapter presents a general algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging parts. Example of using this algorithm also is illustrated. The results obtained applying the proposed algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging conclude that it is a suitable method, which enables to get several alternatives for shape and number of intermediate stages and to select the most appropriate case for specific part. In addition, the algorithm is flexible and addition can be done, especially in connection with the criterions for necessity of intermediate steps.
It is well known that PV thin films can be deposited by an extensive range of more or less expens... more It is well known that PV thin films can be deposited by an extensive range of more or less expensive and complicated techniques (such as sputtering, chemical vapor deposition (CVD), physical vapor deposition (PVD), pulsed laser deposition, atomic layer deposition (ALD)). The present paper focuses on TCO layers applied by chosen techniques, including mainly the ALD and CVD methods. Thin layers of transparent conductive oxides constitute a well-known group of materials with unique properties. Oxides such as ZnO, SnO 2 , and In 2 O 3 are the most significant materials of this type; some of them are discussed in the paper. From the application point of view in the photovoltaic industry, the goal is to apply a method that will provide the highest value of electric charge conductivity while maintaining the minimum value of absorption in the layer and a reduced value of the reflection coefficient. The implementation of significant achievements in the coming decade is for developing guidelines for metallization processes and TCO layers deposited by the ALD method. The work contains chosen engineering processes, including the fabrication of transparent conductive oxides (TCO) thin films applied to silicon substrates by ALD and CVD for application as emitter conductive coatings in photovoltaic structures and the fabrication front metallization of solar cell using different techniques, including among others laser techniques. Moreover, the work also contains predictions about solar cells, which will be among the most prevalent solar cells in mass production using thin-and thick-film technology.
Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. Th... more Publisher Summary Hot close-die forging processes are broadly used in manufacturing currently. This chapter presents a general algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging parts. Example of using this algorithm also is illustrated. The results obtained applying the proposed algorithm for process planning support for intermediate steps designs of axisymmetric hot close-die forging conclude that it is a suitable method, which enables to get several alternatives for shape and number of intermediate stages and to select the most appropriate case for specific part. In addition, the algorithm is flexible and addition can be done, especially in connection with the criterions for necessity of intermediate steps.
НАУЧНИ ТРУДОВЕ НА РУСЕНСКИЯ УНИВЕРСИТЕТ - 2010, том 49, серия 2 - 60 - Симулиране на процеси на о... more НАУЧНИ ТРУДОВЕ НА РУСЕНСКИЯ УНИВЕРСИТЕТ - 2010, том 49, серия 2 - 60 - Симулиране на процеси на обемно деформиране по метода на крайните елементиВалентин Гагов, Росен Радев, Борис Томов ... [18] Гагов В., Р. Радев, Е. Янков, Д. Господинов. ...
It is well known that PV thin films can be deposited by an extensive range of more or less expens... more It is well known that PV thin films can be deposited by an extensive range of more or less expensive and complicated techniques (such as sputtering, chemical vapor deposition (CVD), physical vapor deposition (PVD), pulsed laser deposition, atomic layer deposition (ALD)). The present paper focuses on TCO layers applied by chosen techniques, including mainly the ALD and CVD methods. Thin layers of transparent conductive oxides constitute a well-known group of materials with unique properties. Oxides such as ZnO, SnO2, and In2O3 are the most significant materials of this type; some of them are discussed in the paper. From the application point of view in the photovoltaic industry, the goal is to apply a method that will provide the highest value of electric charge conductivity while maintaining the minimum value of absorption in the layer and a reduced value of the reflection coefficient. The implementation of significant achievements in the coming decade is for developing guidelines f...
Stirring material during the process of friction stir welding, as well as the temperature at whic... more Stirring material during the process of friction stir welding, as well as the temperature at which the joining process is carried out are the main factors that determine the possibility to produce weldments with defined mechanical properties. While the shape and the dimensions of the instrument are primarily related to the blending manner, the temperature is mostly dependent on the welding modes. It is known that there is a temperature range for every alloy, at c b e d ce a f a e. T a e e e a e de e a a e e ding zone is exceptionally important. There are different direct and indirect approaches to temperature determination, and the present report looks at the possibility for indirect temperature determination using examination of the changes in mechanical properties of an aluminium alloy EN AW-1050A H24 (EN AW-Al 99.5). For this purpose, the mechanical properties of the alloy after recrystallization annealing at different temperatures were determined and compared to the mechanical properties of the alloy after friction stir welding using different welding modes.
The parts obtained by forging are better than those manufactured by any other metalworking proces... more The parts obtained by forging are better than those manufactured by any other metalworking process in many aspects. This determines their widespread use where human safety and reliability are critically important. Industries such as aerospace, defence, automotive and agriculture, construction, mining are some of the largest customers using forged parts. The design of hot closed-die processes very often requires engineers to deal with two important challenges-the necessity of preform (intermediate) steps and the shape of these intermediate steps. A general design approach for determination of necessity of preforms and their shape at hot closed-die forging is presented in this article.
As the tendency to lower the mass of welded constructions emerges in the last years, the use of h... more As the tendency to lower the mass of welded constructions emerges in the last years, the use of high strength steels finds a wide range of applications in industry, namely, in reliable highly loaded welded constructions. Following the commonly accepted rules, these steels are suitable for welding. The most used welding methods for welding of high strength steels are submerged arc welding and MAG welding. The mechanical properties of weldment of high strength steels will depend on several different welding details, such as cooling time in the range from 800 to 500 °C-t8/5, the used filler materials, welding protection, etc. Nevertheless, data on the influence of joint preparation, and specifically of the weld gap, are limited or absent. Joint preparation of high strength steels is typically performed according to EN ISO 9692-1:2013 and EN ISO 9692-2:2001. When the welding gap differs significantly from the standards recommendations, it is of great importance to research and to determine the influence of the weld gap on weldment properties and structure. This study introduces the findings on the influence of joint preparation on some mechanical properties of high strength steel S700MC weldments produced by submerged arc welding.
Currently, heat treatment is the most common and effective method for changing the properties of ... more Currently, heat treatment is the most common and effective method for changing the properties of metals and their alloys. Ferrous alloys most often are heat treated and the most commonly used process of heat treatment is the quenching. At quenching the final structure and material's properties are formed during the fast cooling process. Therefore, the correct choice of cooling conditions is critical for quality of quenched parts. The simulation of quenching is one of the modern approaches for researching the cooling processes. In order to obtain reliable results, the correct input data for simulation are crucial. It is commonly accepted that the heat transfer coefficient (HTC) plays most significant influence on the simulation results. Meanwhile in the specialized literature there are quite different values of HTC even at equal cooling conditions and a few data regarding its influence on the simulation results. The aim of this paper is to determine to what extent the results obtained after simulation of quenching processes are influenced by HTC. Samples of different dimensions and ratios between length and diameter (L/D), made of medium carbon steel (C45 EN 10083), were studied. Results for the influence of HTC together with geometry of the quenched parts, especially samples with different ratio length/diameter (L/D), are presented in the article.
Titanium alloys are known for their good mechanical properties, low density, excellent corrosion ... more Titanium alloys are known for their good mechanical properties, low density, excellent corrosion resistance and low thermal conductivity. These properties define titanium and its alloys as highly suitable for medicine, automotive and aerospace industries. Unfortunately, the thermal cycle during welding of alpha-beta alloys (Ti-6Al-4V) can significantly change their strength, toughness and plasticity. The scope of present work is to investigate the possibility for producing Ti-6Al-4V welds by arc discharge in vacuum and to establish the influence of the welding parameters on dimensions and mechanical properties of the welds. The experiments presented here were carried out in an installation for hollow cathode arc treatment in vacuum. Cylindrical and elliptical tantalum cathodes were used. The welding was carried out without filler material and groove. Tensile test and hardness test of specific welds zones were used for mechanical properties determination. The results, presented in this work, describe the dimensions of the fusion zone and heat affected zone of welds, produced by hollow cathode arc welding using different welding parameters. The mechanical properties of the welds were determined.
The structure of Ti-6Al-4V alloy and Ti-6Al-4V weldments was examined. The welds were produced by... more The structure of Ti-6Al-4V alloy and Ti-6Al-4V weldments was examined. The welds were produced by hollow cathode arc discharge in vacuum using tantalum cathodes and different welding parameters. The corrosion behaviour of Ti-6Al-4V alloy and Ti-6Al-4V welds in solution containing Brwas evaluated quantitatively using potentiodynamic polarization tests. The corrosion behaviour of the base metal and welds was compared. Open circuit potential, pitting potential, corrosion current densities and corrosion rates were determined. The influence of the structure and its change during welding on corrosion behaviour is discussed in the present paper.
Archives of materials science and engineering, Nov 1, 2021
Purpose: The presented research aims to determine the microstructural changes in weldments of com... more Purpose: The presented research aims to determine the microstructural changes in weldments of commercially pure titanium Grade 1 after welding by hollow cathode arc discharge in vacuum and related changes in the corrosion behaviour of the weldments. Design/methodology/approach: Macro and microstructure of weldments were studied using optical microscopy. Corrosion behaviour of untreated Grade 1 and heat-affected zone of weldments of Grade 1 was investigated using electrochemical testing, including open circuit potential measurements and potentiodynamic polarisation. As an aggressive environment, 1 M KBr water solution was used. Findings: Welding by hollow cathode arc discharge in vacuum leads to the formation of a coarse Widmanstätten structure in the heat-affected zone. This imperfect structure results in a passive layer with worsened protective properties, thus increasing the corrosion rate of weldments by up to two orders of magnitude compared to Grade 1 in as-received condition. The passive layer on the welded surfaces did not allow Grade 1 to acquire a stable corrosion potential during potenitodynamic polarization. Research limitations/implications: Titanium and its alloys are passivating metallic materials, and their corrosion resistance depends on the properties of a thin protective surface layer. Changes in the underlying metal microstructure can affect the passivation behaviour of titanium and the properties of this layer. Welding by hollow cathode arc discharge in vacuum alters the microstructure of heat-affected zone, thereby causing Widmanstätten microstructure to form. As the passive layer over that microstructure has worsened protective properties, we suggest additional heat treatment after welding to be applied. Future experimental research on this topic is needed. Originality/value: Welding by hollow cathode arc discharge in vacuum is a welding method allowing weldments to be done in a clean environment and even in space. In the specialised literature, information on the structure and corrosion resistance of weldments of commercially pure titanium Grade 1 welded by hollow cathode arc discharge in vacuum is missing. The present research fills in a tiny part of this gap in our knowledge.
Journal of Materials Processing Technology, Nov 1, 2004
... Object of attention in this paper are some representative examples of forgings from group 1 b... more ... Object of attention in this paper are some representative examples of forgings from group 1 by reason of their large spread in the metalworking industry. 3. Intermediate steps of forging. In the case of closed-die forging process design, the required number of stages which ...
Nowadays, the use of high strength (HS) and ultra-high strength steels (UHS) increases, notably i... more Nowadays, the use of high strength (HS) and ultra-high strength steels (UHS) increases, notably in welded constructions. These steels are mainly exploited in heavy loaded welded constructions such as bridges, cranes and excavators, in pressure vessels, vehicles, ships, drilling rigs etc. working at room or lower temperatures. As the welded constructions have specific requirements, the development of high strength and ultra-high strength steels imposes the need for research on the factors influencing their weldability. Among the possible negative implications are: cold cracks formation, softening of the heat affected zone, brittleness in the coarse grained zone. When complying with the generally accepted rules for welding, HS and UHS are readily welded by all conventional welding methods. Recommendations for welding of steels after normalization, thermo-mechanical treatment and quenching and tempering are given in the standard EN 1011 -1, 2. The use of thermo-mechanically treated (hot-rolled) steels with low carbon equivalent, such as S700MC, allows reduction in time required for welding as the preheating temperature is lowered or even preheating is not necessary. A more pronounced negative effect on the weld quality has the presence of different defects. S700MC can be welded by all conventional methods, and a reduction in the softened zone can be achieved by using appropriate welding parameters. Joint preparation for welding of HS and UHS steels is described in the standards EN ISO 9692-1:2013 and EN ISO 9692-2:2001. Nevertheless, the root gap is often the closing part in constructions and does not comply with the standard recommendations. That is why the effect of the root gap on welds has to be researched. The present work introduces results of a research studying the effect of the root gap on the structure and some mechanical and technological properties of S700MS welds, welded by submerged arc welding.
The structure and the mechanical properties of the high-strength structural martensitic steels us... more The structure and the mechanical properties of the high-strength structural martensitic steels used in manufacturing the mechanism parts subjected to significant cyclic dynamical loads are considered. All the steels have a similar martensitic-bainite structure and a high stability of their mechanical properties. At the same time, their structures are found to contain secondary phases, which can degrade their functional properties. 03Kh11N10M2T maraging steel exhibits fairly high impact toughness for this class of steels despite a brittle character of fracture during bending impact tests.
Friction stir welding is one of the most original methods for welding devised in recent years. As... more Friction stir welding is one of the most original methods for welding devised in recent years. As this welding method possesses advantages compared to conventional fusing welding methods, scientific research on its features and improvement is increasing. The advances in the knowledge of the process of friction stir welding allow its increasing application in different areas, such as aircraft and automotive industries, railway transport, nuclear industries etc. During friction stir welding the joined parts are in a solid state. This welding method is mainly used for joining aluminium and its alloys.The stirring and mixing of the material and the temperature during friction stir welding are the main factors that determine the possibility of obtaining weldments with precise mechanical properties.The present study aims to research the influence of the pin`s configuration on different quality aspects of the weldments at chosen parameters of the welding mode. To achieve this, pins with di...
In the present work, a finite element model of the first stage, plunge, of friction stir welding ... more In the present work, a finite element model of the first stage, plunge, of friction stir welding is considered. The welded parts are flat aluminum 1050 plates. The arbitrary Lagrangian-Eulerian formulation implemented in ABAQUS/Explicit is used. The material model of the welded parts is the Johnson-Cook law, and Coulomb’s law describes the friction between the tool and the weldment. Temperature field during the process is obtained, and the influence of the parameters concerning the algorithmic implementation of the finite element method is established. The simulation results are compared with experimental results obtained for this purpose.
This article examines expanded polytetrafluoroethylene (PTFE) flat gaskets used in the industry t... more This article examines expanded polytetrafluoroethylene (PTFE) flat gaskets used in the industry to seal flange connections that prevent mixing of working fluids and leakage of fluids into the environment. Expanded PTFE gaskets and existing solutions to improve tightness are reviewed. Using test equipment for measuring the mass of gas passed through the gasket per unit time, which is one of the main operating characteristics of the gasket, a comparison of the required contact stress applied to the gasket during installation to achieve the same leakage rates was made. An annular expanded PTFE gasket with locally increased density is presented. Comparative tests were conducted to determine the mass of helium gas passed through the gaskets when changing the density in the sealed area to the inner diameter of the gasket. The results of the tests carried out show an improvement in the sealing ability and indicate a reduction in the mass of passed gas with the application of a lower contac...
Archives of Materials Science and Engineering, 2021
Purpose: The presented research aims to determine the microstructural changes in weldments of com... more Purpose: The presented research aims to determine the microstructural changes in weldments of commercially pure titanium Grade 1 after welding by hollow cathode arc discharge in vacuum and related changes in the corrosion behaviour of the weldments. Design/methodology/approach: Macro and microstructure of weldments were studied using optical microscopy. Corrosion behaviour of untreated Grade 1 and heat-affected zone of weldments of Grade 1 was investigated using electrochemical testing, including open circuit potential measurements and potentiodynamic polarisation. As an aggressive environment, 1 M KBr water solution was used. Findings: Welding by hollow cathode arc discharge in vacuum leads to the formation of a coarse Widmanstätten structure in the heat-affected zone. This imperfect structure results in a passive layer with worsened protective properties, thus increasing the corrosion rate of weldments by up to two orders of magnitude compared to Grade 1 in as-received condition. ...
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Papers by Rossen Radev