The sessile drop method combined with a capillary purification procedure was used,for thefirst time,to analyze the high-temperature behavior of molten Mg on three dissimilar substrates:1)molybdenum,2)tantalum and 3)AISI...The sessile drop method combined with a capillary purification procedure was used,for thefirst time,to analyze the high-temperature behavior of molten Mg on three dissimilar substrates:1)molybdenum,2)tantalum and 3)AISI 316L stainless steel.All tests were performed under isothermal conditions at 720℃ in a protective atmosphere(Ar+5 wt.%H2).Images of Mg/substrate couples recorded during the experiments were used to calculate the contact angles(θ)formed between the liquid Mg drop and the selected substrates.After the sessile drop tests,the Mg/Mo,Mg/Ta,and Mg/AISI 316L couples were subjected to in-depth microstructural characterization using scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).Under the employed experimental conditions,oxide-free Mg drops on all tested couples presented non-wetting behavior(θ>90°).The average values of the calculated contact angles after 40 s of liquid Mg deposition wereθMg/Mo=124°,θMg/Ta=125°,andθMg/AISI 316L=126°,respectively.The SEM/EDS analysis showed no mass transfer and no bonding between solidified drops and the substrates.This non-reactive and non-wetting behavior of investigated couples can be associated with the immiscible nature of the Mg-Mo,Mg-Ta,and Mg-Fe systems,where the solubility of liquid Mg with all tested materials is negligible,and Mg does not form any compounds with them.展开更多
Further development of the technology for making moulding and core sands will be strictly limited by tough requirements due to protection of the natural environment. These tendencies are becoming more and more tense, ...Further development of the technology for making moulding and core sands will be strictly limited by tough requirements due to protection of the natural environment. These tendencies are becoming more and more tense, so that we will reach a point when even processes, that from technological point of view fulfill high requirements of the foundry industry, must be replaced by more ecologically-friendly solutions. Hence, technologies using synthetic resins as binding materials will be limited. This paper presents some predictable development tendencies of moulding and core sands. The increasing role of inorganic substances will be noticed, including silicate binders with significantly improved properties, such as improved knock-out property or higher reclamation strength. Other interesting solutions might also be moulding sands bonded by geo-polymers and phosphate binders or salts and also binders based on degradable biopolymers. These tendencies and the usefulness of these binders are put forward in this paper.展开更多
At present, furan resin is the largest selling no-bake system of moulding sands. The most commonly used furan no-bake binders(FNB) are condensation products of furfuryl alcohol(FA) urea, formaldehyde and phenol. They ...At present, furan resin is the largest selling no-bake system of moulding sands. The most commonly used furan no-bake binders(FNB) are condensation products of furfuryl alcohol(FA) urea, formaldehyde and phenol. They are generally cured by exposure to organic sulfonic acids. FNB provide excellent mold and core strength, cure rapidly and allow the sand to be reclaimed at fairly high yields, generally 75%-80%, especially in applications where due allowance is made for the need to keep total sulfur content below 0.1%. However, due to probable carcinogenic properties of furfuryl alcohol, the EU Directive limits the content of this substance(in a monomer form in resin) to 25%. The classification of furfuryl alcohol and the resulting furan resin products has changed from "harmful" to "toxic by inhalation". The aim of this study was to determine the effect of free furfuryl alcohol content in the resin on the emission of harmful substances from the BTEX(Benzene Toluene Ethylbenzene & Xylene) and PAHs(polycyclic aromatic hydrocarbon) group exposed to high temperature and how it affects the emissions allowance of reclaimed sand in the matrix. Three resins from a leading manufacturer were examined, which contain a free furfuryl alcohol content of 71%-72%, about 50% and < 25%, respectively. The hardener for each resin was 65% aqueous solution of paratoluenesulfonic acid. Tests were carried out in semi-industrial conditions where liquid cast-iron was poured into sample sand mold at 1,350 °C. The matrix of the studied sands was reclaimed in the amount of 0, 50%, 100%, respectively.With the increase of free furfuryl alcohol content, the volume of evolved gases decreased. For all resins the main component from the BTEX group dominating in the emitted gases was benzene; however toluene also appeared in the amount of a few percentages. In contrast, ethylbenzene and xylenes occurred only in the gases emitted from resin-bonded sands with the largest furfuryl alcohol content. The increase in the share of reclaimed sands resulted in very significant increase in the volume of gas generated and participation of benzene in these gases. In terms of emission of compounds from the PAHs group virtually for all resins, the total content of these substances was comparable(within the limits of error). The main components were: fluoranthene, pyrene and benzo(a) anthracene.展开更多
Zn-Al alloys constitute an interesting group of foundry alloys. Due to a relatively low melting temperature, they allow a decrease in energy-consumption of the melting process and alloy preparation. The vibration damp...Zn-Al alloys constitute an interesting group of foundry alloys. Due to a relatively low melting temperature, they allow a decrease in energy-consumption of the melting process and alloy preparation. The vibration damping ability is one of the most interesting properties of the Zn-Al alloys. Zn-Al alloys are divided into two groups: the low-aluminium and high-aluminium alloys. The investigated Zn-10 wt.% Al(ZnAl10) alloy is representative of the high-aluminium alloys, which, on account of its tendency of forming coarse-grained structures, has rather low plastic properties, including elongation. In order to improve the plastic properties, a modification treatment is usually applied. The dependence of the damping coefficient of the ultrasound wave on the amount of the introduced inoculant was studied. Investigations were performed using the AlT i3C0.15 inoculant as the modifier of the ZnAl10 alloy. It was found that titanium additions, in a range from 25 to 100 ppm in relation to the melted charge mass, can reduce the damping coefficient value. An increase of the inoculant addition causes a rise of the damping coefficient, which is probably related to the scattering of the ultrasound wave on Al_3Ti and TiC particles introduced with the inoculant.展开更多
Reclamation of used moulding and core sands has been defined as a treatment of waste moulding refractory materials, enabling a recovery of at least one of the components having properties similar to those of the fresh...Reclamation of used moulding and core sands has been defined as a treatment of waste moulding refractory materials, enabling a recovery of at least one of the components having properties similar to those of the fresh component, and reuse for production of casting moulds and cores. However, at present, there is a lack of a reclaimed material assessment index, which could be applied to each type of moulding sand and reclaim. Modern investigation methods and equipment for the estimation of the quality of the moulding sands matrices with organic binders, in their circulation process, are presented in this paper. These methods, utilizing the special equipment combined with the author's investigation methods developed in the Faculty of Foundry Engineering, AGH - University of Science and Technology, allow the better estimation of the matrix quality both in an aspect of its application as a fresh sand substitute in the preparation of moulding sands, and also with regard to the environmental protection. The most important criteria for the technological assessment of the reclaimed materials and the quality of sands with organic binders are presented in this paper.展开更多
This paper presents results of thermoanalytical and structural research on phenolic binder used in foundry for the preparation of moulding sand. The binder has been prepared based on resole type phenolic resin with th...This paper presents results of thermoanalytical and structural research on phenolic binder used in foundry for the preparation of moulding sand. The binder has been prepared based on resole type phenolic resin with the addition of ester hardener. The aim of the study was to determine the structural changes taking place in the phenolic binder under the influence of temperature. Results show that in the investigated range of temperatures, phenolic binder exhibits three exothermic thermal effects accompanying the decomposition process. The test results using the Diffuse Reflectance Infrared Fourier Transform Spectroscopy(DRIFTS) technique show that the addition of a hardener stabilizes the binder structure within methylene bridges. The reduction in the reaction rate observed in the DTA curve at about 330 °C can be associated with the formation of gaseous products by decomposition of the binder or, as suggested by the literature data, the formation of triple bonds and CN-HCN groups.展开更多
Mechanical reclamation processes of spent moulding sands generate large amounts of postreclamation dusts mainly containing rubbed spent binding agents and quartz dusts. The amount of postreclamation dusts, depending i...Mechanical reclamation processes of spent moulding sands generate large amounts of postreclamation dusts mainly containing rubbed spent binding agents and quartz dusts. The amount of postreclamation dusts, depending in the reclamation system effi ciency and the reclaim dedusting system, can reach 5%-10% in relation to the total reclaimed spent moulding sand. The proper utilization of such material is a big problem facing foundries these days. This study presents the results of investigations of physicochemical properties of post- reclamation dusts. All tested dusts originated from various Polish cast steel plants applying the mechanical reclamation process of moulding sands with alkaline resins, obtained from different producers. Different dusts, delivered from foundries, were tested to determine their chemical composition, granular characterization, physicochemical and energetic properties. Presented results confi rmed assumptions that it is possible to utilize dusts generated during mechanical reclamation of used sands with organic resins as a source of energy.展开更多
Metal matrix composites(MMCs)have received much attention due to their promising advanced mechanical properties.The aim of this work is to create a micro-macro model of composite crystallization.The developed model is...Metal matrix composites(MMCs)have received much attention due to their promising advanced mechanical properties.The aim of this work is to create a micro-macro model of composite crystallization.The developed model is coupled with the process of heat flow in the macroscopic scale,resulting from the heat emission during the nucleation and the growth of grains.Taking into account both of these phenomena,the proposed model is distinguished by a good reflection of reality.Moreover,the presented model assumes that the function of grain density depends on the maximal supercooling and the mass volume of the reinforcement phase particles.The knowledge of the equations,describing the function of grain density depending on the degree of supercooling,is necessary in the,more and more often used,numerical modelling of the casting structure.展开更多
Bentonite is one of the most widespread used clays connected with various applications. In the case of foundry technology, bentonite is primarily used as a binder for mold manufacture. Thermal stability of bentonites ...Bentonite is one of the most widespread used clays connected with various applications. In the case of foundry technology, bentonite is primarily used as a binder for mold manufacture. Thermal stability of bentonites is a natural property of clay minerals and it depends on the genesis, source and chemical composition of the clay. This property is also closely connected to bentonite structure. According to DTA analysis if only one peak of dehydroxylation is observed(about 600 oC), the cis- isomerism of bentonite is expected, while two peaks of de-hydroxylation(about 550 and 850 oC) are expected in the trans- one. In this overview, the bentonite structure, the water – bentonite interaction and the swelling behavior of bentonite in connection with the general technological properties of bentonite molding mixture are summarized. Further, various types of methods for determination of bentonite thermostability are discussed, including instrumental analytical methods as well as methods that employ evaluation of various technological properties of bentonite binders and/or bentonite molding mixtures.展开更多
A device based on a high pressure die-casting(HPDC) machine was constructed,with a capacity to produce thixo-casts from steel.After inductive heating to the required semi-solid temperature range,the samples were trans...A device based on a high pressure die-casting(HPDC) machine was constructed,with a capacity to produce thixo-casts from steel.After inductive heating to the required semi-solid temperature range,the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die.Bearing steel 100Cr6(after forging) was used as the feedstock material.The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 μm and 8 μm.Differential scanning calorimetry(DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 ?C which was attributed to about 45% of a liquid phase.With such technological parameters after the semi-solid processing the microstructure consisted of globular grains of size from 15 μm to 40 μm.The microstructure of globules indicated predominant presence of martensite(about 76% volume fraction) with residual austenite between plates.X-ray analysis confirmed that the thixo-cast samples contain mainly martensite and residual austenite.The hardness of the initial forged sample was HRC 27 and after the thixoforming process it was HRC 60,which confirms the presence of martensite and carbides.The thixo-casts were subjected to low tempering,at temperature of 150 °C for a period of 2 h,in order to remove stresses created during the process of thixoforming and to increase plasticity.The hardness after tempering was HRC 62.3.Additionally,in order to identify phases present in the thixo-casts,transmission electron microscopy(TEM) was carried out.展开更多
Research results concerning the application of ultrasound technique for determining the averaged thermal conductivity in walls of castings produced of cast iron(solidifying in a steady system)containing carbon precipi...Research results concerning the application of ultrasound technique for determining the averaged thermal conductivity in walls of castings produced of cast iron(solidifying in a steady system)containing carbon precipitates in a graphite form,are presented in the hereby paper.Investigations concern castings of unalloyed cast iron.The influence of the form of graphite precipitates on the cast iron thermal conductivity as well as on the propagation velocity of the ultrasound wave,including the longitudinal wave velocity CL,was investigated in the study.The influence of the graphite form,described by the shape indicator(f),on the thermal conductivity(l)(determined on samples by the steady heat flow method)as well as the influence of this indicator(f)on the wave propagation velocity(CL),was investigated.A series of melts of cast iron,of the near eutectic chemical composition,were performed.Magnesium introduced in a wide range,allowed obtaining various graphite forms from flake,via mixed,vermicular to nodular.Dependences:l=f(CL),CL=f(f)were determined and at the final phase the empirical dependencel=f(CL)was also determined.The thermal conductivity and ultrasound wave velocity were tested on the same samples.The thermal conductivity coefficient of cast iron(l)was changing in a wide range from approximately 32 to 46 W/s·m,while the wave velocity CL respectively:from approximately 4,300 to 5,800 m/s.The empirical dependencel=f(CL),determined in the described variability ranges,is of a linear character and the correlation level equals:R2=0.87.The validation of the experimental results was performed on cast iron castings of slag ladles,since they are required to be of a good thermal conductivity.The possibility of assessing the thermal conductivity directly in walls of such castings by means of non-destructive ultrasound method,was confirmed.The real thermal conductivity determined in the walls of the castings is used to simulate the heating and cooling process of slag ladles,ingot molds and similar structures,which was one of the main objectives of the research.展开更多
The sessile drop method was applied to the experimental investigation of the wetting and spreading behaviors of liquid Mg drops on pure Ni substrates.For comparison,the experiments were performed in two variants:(1)us...The sessile drop method was applied to the experimental investigation of the wetting and spreading behaviors of liquid Mg drops on pure Ni substrates.For comparison,the experiments were performed in two variants:(1)using the Capillary Purification(CP)procedure,which allows the non-contact heating and squeezing of a pure oxide-free Mg drop;(2)by classical Contact Heating(CH)procedure.The high-temperature tests were performed under isothermal conditions(CP:760℃for 30 s;CH:715℃for 300 s)using Ar+5 wt%H_(2) atmosphere.During the sessile drop tests,images of the Mg/Ni couples were recorded by CCD cameras(57 fps),which were then applied to calculate the contact angles of metal/substrate couples.Scanning and transmission electron microscopy analyses,both coupled with energy-dispersive X-ray spectroscopy,were used for detailed structural characterization of the solidified couples.It was found that an oxide-free Mg drop obtained by the CP procedure showed a wetting phenomenon on the Ni substrate(an average contact angleθ<90°in<1 s),followed by fast spreading and good wetting over the Ni substrate(θ_((CP))~20°in 5 s)to form a final contact angle ofθ_(f(CP))~18°.In contrast,a different wetting behavior was observed for the CH procedure,where the unavoidable primary oxide film on the Mg surface blocked the spreading of liquid Mg showing apparently non-wetting behavior after 300 s contact at the test temperature.However,in both cases,the deep craters formed in the Ni substrates under the Mg drops and significant change in the structure of initially pure Mg drops to Mg-Ni alloys suggest a strong dissolution of Ni in liquid Mg and apparent values of the final contact angles measured for the Mg/Ni system.展开更多
Larger and larger proportions of aluminium castings,especially those produced by the die casting process,can be observed during recent years in the automotive industry,house-hold articles and others.In case of the aut...Larger and larger proportions of aluminium castings,especially those produced by the die casting process,can be observed during recent years in the automotive industry,house-hold articles and others.In case of the automotive industry,apart from the traditional elements produced by the die pressure method such as engine blocks or crank shaft bedplates,aluminium is displacing steel from structural parts of cars('body in white').The current state and development directions of the structural solutions of cold-chamber die castings are analysed in this paper.These solutions drive the prospective development of these machines and die casting technology.The focus is mainly on essential functional systems such as:hydraulic drives of closing and locking units,as well as pressing in die machines of known companies present on the European market.展开更多
This paper focuses on the possibility of using the biodegradable materials as binders(or parts of binders' compositions) for foundry moulding and core sands. Results showed that there is a great possibility of usi...This paper focuses on the possibility of using the biodegradable materials as binders(or parts of binders' compositions) for foundry moulding and core sands. Results showed that there is a great possibility of using available biodegradable materials as foundry moulding sand binders. Using biodegradable materials as partial content of new binders, or additives to moulding sands may not only decrease the toxicity and increase reclamation ability of tested moulding sands, but also accelerate the biodegradation rate of used binders, and the new biodegradable additive(PCL) did not decrease the strength and thermal properties. In addition, using polycaprolactone(PCL) as a biodegradable material may improve the flexibility of moulding sands with polymeric binder and reduce toxicity.展开更多
文摘The sessile drop method combined with a capillary purification procedure was used,for thefirst time,to analyze the high-temperature behavior of molten Mg on three dissimilar substrates:1)molybdenum,2)tantalum and 3)AISI 316L stainless steel.All tests were performed under isothermal conditions at 720℃ in a protective atmosphere(Ar+5 wt.%H2).Images of Mg/substrate couples recorded during the experiments were used to calculate the contact angles(θ)formed between the liquid Mg drop and the selected substrates.After the sessile drop tests,the Mg/Mo,Mg/Ta,and Mg/AISI 316L couples were subjected to in-depth microstructural characterization using scanning electron microscopy(SEM)and energy-dispersive X-ray spectroscopy(EDS).Under the employed experimental conditions,oxide-free Mg drops on all tested couples presented non-wetting behavior(θ>90°).The average values of the calculated contact angles after 40 s of liquid Mg deposition wereθMg/Mo=124°,θMg/Ta=125°,andθMg/AISI 316L=126°,respectively.The SEM/EDS analysis showed no mass transfer and no bonding between solidified drops and the substrates.This non-reactive and non-wetting behavior of investigated couples can be associated with the immiscible nature of the Mg-Mo,Mg-Ta,and Mg-Fe systems,where the solubility of liquid Mg with all tested materials is negligible,and Mg does not form any compounds with them.
文摘Further development of the technology for making moulding and core sands will be strictly limited by tough requirements due to protection of the natural environment. These tendencies are becoming more and more tense, so that we will reach a point when even processes, that from technological point of view fulfill high requirements of the foundry industry, must be replaced by more ecologically-friendly solutions. Hence, technologies using synthetic resins as binding materials will be limited. This paper presents some predictable development tendencies of moulding and core sands. The increasing role of inorganic substances will be noticed, including silicate binders with significantly improved properties, such as improved knock-out property or higher reclamation strength. Other interesting solutions might also be moulding sands bonded by geo-polymers and phosphate binders or salts and also binders based on degradable biopolymers. These tendencies and the usefulness of these binders are put forward in this paper.
基金supported by the National Centre for Research and Development(PolandNo PBS2/A5/30/2013)
文摘At present, furan resin is the largest selling no-bake system of moulding sands. The most commonly used furan no-bake binders(FNB) are condensation products of furfuryl alcohol(FA) urea, formaldehyde and phenol. They are generally cured by exposure to organic sulfonic acids. FNB provide excellent mold and core strength, cure rapidly and allow the sand to be reclaimed at fairly high yields, generally 75%-80%, especially in applications where due allowance is made for the need to keep total sulfur content below 0.1%. However, due to probable carcinogenic properties of furfuryl alcohol, the EU Directive limits the content of this substance(in a monomer form in resin) to 25%. The classification of furfuryl alcohol and the resulting furan resin products has changed from "harmful" to "toxic by inhalation". The aim of this study was to determine the effect of free furfuryl alcohol content in the resin on the emission of harmful substances from the BTEX(Benzene Toluene Ethylbenzene & Xylene) and PAHs(polycyclic aromatic hydrocarbon) group exposed to high temperature and how it affects the emissions allowance of reclaimed sand in the matrix. Three resins from a leading manufacturer were examined, which contain a free furfuryl alcohol content of 71%-72%, about 50% and < 25%, respectively. The hardener for each resin was 65% aqueous solution of paratoluenesulfonic acid. Tests were carried out in semi-industrial conditions where liquid cast-iron was poured into sample sand mold at 1,350 °C. The matrix of the studied sands was reclaimed in the amount of 0, 50%, 100%, respectively.With the increase of free furfuryl alcohol content, the volume of evolved gases decreased. For all resins the main component from the BTEX group dominating in the emitted gases was benzene; however toluene also appeared in the amount of a few percentages. In contrast, ethylbenzene and xylenes occurred only in the gases emitted from resin-bonded sands with the largest furfuryl alcohol content. The increase in the share of reclaimed sands resulted in very significant increase in the volume of gas generated and participation of benzene in these gases. In terms of emission of compounds from the PAHs group virtually for all resins, the total content of these substances was comparable(within the limits of error). The main components were: fluoranthene, pyrene and benzo(a) anthracene.
基金financially supported by the resources of the National Science Centre of Poland awarded on the basis of the decision No.DEC-2011/01/N/ST8/07054
文摘Zn-Al alloys constitute an interesting group of foundry alloys. Due to a relatively low melting temperature, they allow a decrease in energy-consumption of the melting process and alloy preparation. The vibration damping ability is one of the most interesting properties of the Zn-Al alloys. Zn-Al alloys are divided into two groups: the low-aluminium and high-aluminium alloys. The investigated Zn-10 wt.% Al(ZnAl10) alloy is representative of the high-aluminium alloys, which, on account of its tendency of forming coarse-grained structures, has rather low plastic properties, including elongation. In order to improve the plastic properties, a modification treatment is usually applied. The dependence of the damping coefficient of the ultrasound wave on the amount of the introduced inoculant was studied. Investigations were performed using the AlT i3C0.15 inoculant as the modifier of the ZnAl10 alloy. It was found that titanium additions, in a range from 25 to 100 ppm in relation to the melted charge mass, can reduce the damping coefficient value. An increase of the inoculant addition causes a rise of the damping coefficient, which is probably related to the scattering of the ultrasound wave on Al_3Ti and TiC particles introduced with the inoculant.
基金co-financed by the European Regional Development Fund within the framework of the Polish Innovative Optional Programme,No.WND-POIG.01.03.01-12-007/09
文摘Reclamation of used moulding and core sands has been defined as a treatment of waste moulding refractory materials, enabling a recovery of at least one of the components having properties similar to those of the fresh component, and reuse for production of casting moulds and cores. However, at present, there is a lack of a reclaimed material assessment index, which could be applied to each type of moulding sand and reclaim. Modern investigation methods and equipment for the estimation of the quality of the moulding sands matrices with organic binders, in their circulation process, are presented in this paper. These methods, utilizing the special equipment combined with the author's investigation methods developed in the Faculty of Foundry Engineering, AGH - University of Science and Technology, allow the better estimation of the matrix quality both in an aspect of its application as a fresh sand substitute in the preparation of moulding sands, and also with regard to the environmental protection. The most important criteria for the technological assessment of the reclaimed materials and the quality of sands with organic binders are presented in this paper.
文摘This paper presents results of thermoanalytical and structural research on phenolic binder used in foundry for the preparation of moulding sand. The binder has been prepared based on resole type phenolic resin with the addition of ester hardener. The aim of the study was to determine the structural changes taking place in the phenolic binder under the influence of temperature. Results show that in the investigated range of temperatures, phenolic binder exhibits three exothermic thermal effects accompanying the decomposition process. The test results using the Diffuse Reflectance Infrared Fourier Transform Spectroscopy(DRIFTS) technique show that the addition of a hardener stabilizes the binder structure within methylene bridges. The reduction in the reaction rate observed in the DTA curve at about 330 °C can be associated with the formation of gaseous products by decomposition of the binder or, as suggested by the literature data, the formation of triple bonds and CN-HCN groups.
基金financed by The Polish National Centre for Research and Development within the project INNOTECH-K1/IN1/57/156360/NCBR/12
文摘Mechanical reclamation processes of spent moulding sands generate large amounts of postreclamation dusts mainly containing rubbed spent binding agents and quartz dusts. The amount of postreclamation dusts, depending in the reclamation system effi ciency and the reclaim dedusting system, can reach 5%-10% in relation to the total reclaimed spent moulding sand. The proper utilization of such material is a big problem facing foundries these days. This study presents the results of investigations of physicochemical properties of post- reclamation dusts. All tested dusts originated from various Polish cast steel plants applying the mechanical reclamation process of moulding sands with alkaline resins, obtained from different producers. Different dusts, delivered from foundries, were tested to determine their chemical composition, granular characterization, physicochemical and energetic properties. Presented results confi rmed assumptions that it is possible to utilize dusts generated during mechanical reclamation of used sands with organic resins as a source of energy.
基金supported by the Polish Ministry of Science and Higher Education within the frames of independent studies AGH(Nos:11.11.170.318 and 15.11.170.424)
文摘Metal matrix composites(MMCs)have received much attention due to their promising advanced mechanical properties.The aim of this work is to create a micro-macro model of composite crystallization.The developed model is coupled with the process of heat flow in the macroscopic scale,resulting from the heat emission during the nucleation and the growth of grains.Taking into account both of these phenomena,the proposed model is distinguished by a good reflection of reality.Moreover,the presented model assumes that the function of grain density depends on the maximal supercooling and the mass volume of the reinforcement phase particles.The knowledge of the equations,describing the function of grain density depending on the degree of supercooling,is necessary in the,more and more often used,numerical modelling of the casting structure.
文摘Bentonite is one of the most widespread used clays connected with various applications. In the case of foundry technology, bentonite is primarily used as a binder for mold manufacture. Thermal stability of bentonites is a natural property of clay minerals and it depends on the genesis, source and chemical composition of the clay. This property is also closely connected to bentonite structure. According to DTA analysis if only one peak of dehydroxylation is observed(about 600 oC), the cis- isomerism of bentonite is expected, while two peaks of de-hydroxylation(about 550 and 850 oC) are expected in the trans- one. In this overview, the bentonite structure, the water – bentonite interaction and the swelling behavior of bentonite in connection with the general technological properties of bentonite molding mixture are summarized. Further, various types of methods for determination of bentonite thermostability are discussed, including instrumental analytical methods as well as methods that employ evaluation of various technological properties of bentonite binders and/or bentonite molding mixtures.
文摘A device based on a high pressure die-casting(HPDC) machine was constructed,with a capacity to produce thixo-casts from steel.After inductive heating to the required semi-solid temperature range,the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die.Bearing steel 100Cr6(after forging) was used as the feedstock material.The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 μm and 8 μm.Differential scanning calorimetry(DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 ?C which was attributed to about 45% of a liquid phase.With such technological parameters after the semi-solid processing the microstructure consisted of globular grains of size from 15 μm to 40 μm.The microstructure of globules indicated predominant presence of martensite(about 76% volume fraction) with residual austenite between plates.X-ray analysis confirmed that the thixo-cast samples contain mainly martensite and residual austenite.The hardness of the initial forged sample was HRC 27 and after the thixoforming process it was HRC 60,which confirms the presence of martensite and carbides.The thixo-casts were subjected to low tempering,at temperature of 150 °C for a period of 2 h,in order to remove stresses created during the process of thixoforming and to increase plasticity.The hardness after tempering was HRC 62.3.Additionally,in order to identify phases present in the thixo-casts,transmission electron microscopy(TEM) was carried out.
基金This research was performed within realization of Project:POIR.01.01.01-00-0965/17.
文摘Research results concerning the application of ultrasound technique for determining the averaged thermal conductivity in walls of castings produced of cast iron(solidifying in a steady system)containing carbon precipitates in a graphite form,are presented in the hereby paper.Investigations concern castings of unalloyed cast iron.The influence of the form of graphite precipitates on the cast iron thermal conductivity as well as on the propagation velocity of the ultrasound wave,including the longitudinal wave velocity CL,was investigated in the study.The influence of the graphite form,described by the shape indicator(f),on the thermal conductivity(l)(determined on samples by the steady heat flow method)as well as the influence of this indicator(f)on the wave propagation velocity(CL),was investigated.A series of melts of cast iron,of the near eutectic chemical composition,were performed.Magnesium introduced in a wide range,allowed obtaining various graphite forms from flake,via mixed,vermicular to nodular.Dependences:l=f(CL),CL=f(f)were determined and at the final phase the empirical dependencel=f(CL)was also determined.The thermal conductivity and ultrasound wave velocity were tested on the same samples.The thermal conductivity coefficient of cast iron(l)was changing in a wide range from approximately 32 to 46 W/s·m,while the wave velocity CL respectively:from approximately 4,300 to 5,800 m/s.The empirical dependencel=f(CL),determined in the described variability ranges,is of a linear character and the correlation level equals:R2=0.87.The validation of the experimental results was performed on cast iron castings of slag ladles,since they are required to be of a good thermal conductivity.The possibility of assessing the thermal conductivity directly in walls of such castings by means of non-destructive ultrasound method,was confirmed.The real thermal conductivity determined in the walls of the castings is used to simulate the heating and cooling process of slag ladles,ingot molds and similar structures,which was one of the main objectives of the research.
基金supported by the National Science Centre of Poland within OPUS 16 Project,no.2018/31/B/ST8/01172。
文摘The sessile drop method was applied to the experimental investigation of the wetting and spreading behaviors of liquid Mg drops on pure Ni substrates.For comparison,the experiments were performed in two variants:(1)using the Capillary Purification(CP)procedure,which allows the non-contact heating and squeezing of a pure oxide-free Mg drop;(2)by classical Contact Heating(CH)procedure.The high-temperature tests were performed under isothermal conditions(CP:760℃for 30 s;CH:715℃for 300 s)using Ar+5 wt%H_(2) atmosphere.During the sessile drop tests,images of the Mg/Ni couples were recorded by CCD cameras(57 fps),which were then applied to calculate the contact angles of metal/substrate couples.Scanning and transmission electron microscopy analyses,both coupled with energy-dispersive X-ray spectroscopy,were used for detailed structural characterization of the solidified couples.It was found that an oxide-free Mg drop obtained by the CP procedure showed a wetting phenomenon on the Ni substrate(an average contact angleθ<90°in<1 s),followed by fast spreading and good wetting over the Ni substrate(θ_((CP))~20°in 5 s)to form a final contact angle ofθ_(f(CP))~18°.In contrast,a different wetting behavior was observed for the CH procedure,where the unavoidable primary oxide film on the Mg surface blocked the spreading of liquid Mg showing apparently non-wetting behavior after 300 s contact at the test temperature.However,in both cases,the deep craters formed in the Ni substrates under the Mg drops and significant change in the structure of initially pure Mg drops to Mg-Ni alloys suggest a strong dissolution of Ni in liquid Mg and apparent values of the final contact angles measured for the Mg/Ni system.
文摘Larger and larger proportions of aluminium castings,especially those produced by the die casting process,can be observed during recent years in the automotive industry,house-hold articles and others.In case of the automotive industry,apart from the traditional elements produced by the die pressure method such as engine blocks or crank shaft bedplates,aluminium is displacing steel from structural parts of cars('body in white').The current state and development directions of the structural solutions of cold-chamber die castings are analysed in this paper.These solutions drive the prospective development of these machines and die casting technology.The focus is mainly on essential functional systems such as:hydraulic drives of closing and locking units,as well as pressing in die machines of known companies present on the European market.
基金financially supported by AGH Research Project No.11.11.170.318-3
文摘This paper focuses on the possibility of using the biodegradable materials as binders(or parts of binders' compositions) for foundry moulding and core sands. Results showed that there is a great possibility of using available biodegradable materials as foundry moulding sand binders. Using biodegradable materials as partial content of new binders, or additives to moulding sands may not only decrease the toxicity and increase reclamation ability of tested moulding sands, but also accelerate the biodegradation rate of used binders, and the new biodegradable additive(PCL) did not decrease the strength and thermal properties. In addition, using polycaprolactone(PCL) as a biodegradable material may improve the flexibility of moulding sands with polymeric binder and reduce toxicity.
