Pub Date : 1984-01-01DOI: 10.1179/030716984803275025
J. A. Pardoe
AbstractThe introduction includes a brief resume of the development of the CONFORM process, from its invention at the UKAEA Springfields Laboratories in 1971 to the present, at which time it has established itself as having many industrial applications in the extrusion of solid and hollow sections from many non-ferrous metals, in rod or particulate form, together with the potential for extruding direct from molten metal. Consideration is given to energy-saving aspects, especially when extruding from particulated metals, not only as an alternative to conventional press extrusion from billets, but also as an extension to powder metallurgical technology. Of particular relevance is the application of CONFORM to the reclamation both of prime metal waste from manufacturing operations and of used scrap. Irretrievable disposal and remelting to ingot and billet for subsequent fabrication are taken as the bases for assessing the energy savings attainable by integrating CONFORM with various pretreatments.
{"title":"CONFORM continuous extrusion process – its contribution to energy conservation","authors":"J. A. Pardoe","doi":"10.1179/030716984803275025","DOIUrl":"https://doi.org/10.1179/030716984803275025","url":null,"abstract":"AbstractThe introduction includes a brief resume of the development of the CONFORM process, from its invention at the UKAEA Springfields Laboratories in 1971 to the present, at which time it has established itself as having many industrial applications in the extrusion of solid and hollow sections from many non-ferrous metals, in rod or particulate form, together with the potential for extruding direct from molten metal. Consideration is given to energy-saving aspects, especially when extruding from particulated metals, not only as an alternative to conventional press extrusion from billets, but also as an extension to powder metallurgical technology. Of particular relevance is the application of CONFORM to the reclamation both of prime metal waste from manufacturing operations and of used scrap. Irretrievable disposal and remelting to ingot and billet for subsequent fabrication are taken as the bases for assessing the energy savings attainable by integrating CONFORM with various pretreatments.","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"215 1","pages":"358-365"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78265650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274350
J. Wilcox, R. Honeycombe
AbstractC–Mn–Al, C–Mn–Nb, and C–Mn–Nb–Al steels are known to exhibit troughs in their hot ductility behaviour. This paper attempts to explain the high-temperature brittleness of these steels by examining their hot deformation behaviour. Slow strain-rate, hot tensile testing of laboratory-melted and commercial C–Mn steels containing niobium and/or soluble aluminium following solution treatment at 1300°C for 1·5 h has been performed. The occurrence (or otherwise) of dynamic recrystallization, hot strength, and elongation to fracture were noted as a function of deformation temperature, and the austenite-ferrite equilibrium transformation temperature determined by slow-heating dilatometry. The addition of niobium and/or soluble aluminium to C–Mn–N steel produced a hot ductility trough, failure being intergranular when ductility was poor and by dimpled rupture and tensile necking when ductility was good. Poor ductility was associated with a fully austenitic microstructure. Small amounts of ferrite did not appe...
{"title":"Hot ductility of Nb and Al microalloyed steels follovving high-temperature solution treatment","authors":"J. Wilcox, R. Honeycombe","doi":"10.1179/030716984803274350","DOIUrl":"https://doi.org/10.1179/030716984803274350","url":null,"abstract":"AbstractC–Mn–Al, C–Mn–Nb, and C–Mn–Nb–Al steels are known to exhibit troughs in their hot ductility behaviour. This paper attempts to explain the high-temperature brittleness of these steels by examining their hot deformation behaviour. Slow strain-rate, hot tensile testing of laboratory-melted and commercial C–Mn steels containing niobium and/or soluble aluminium following solution treatment at 1300°C for 1·5 h has been performed. The occurrence (or otherwise) of dynamic recrystallization, hot strength, and elongation to fracture were noted as a function of deformation temperature, and the austenite-ferrite equilibrium transformation temperature determined by slow-heating dilatometry. The addition of niobium and/or soluble aluminium to C–Mn–N steel produced a hot ductility trough, failure being intergranular when ductility was poor and by dimpled rupture and tensile necking when ductility was good. Poor ductility was associated with a fully austenitic microstructure. Small amounts of ferrite did not appe...","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"34 1","pages":"217-225"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80069413","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274882
A. Walker, D. West, W. Steen
AbstractAn investigation is reported of the introduction of carbon into a pure iron and into a 1C-1·4Cr steel (S 135) by means of laser surface alloying. The procedure involved precoating the specimen surfaces with Dag graphite; successive laser surface-melting treatments (up to 12) were given, re-applying the graphite coatings between each treatment. Alloying was carried out both with shallow melt zones and with ‘keyhole’ zones. Substantial degrees of carbon alloying were achieved, ranging from hypo- to hypereutectic levels; the maximum obtained was ∼6%C. In the hypereutectic zones substantial cracking and porosity were encountered. The white iron structures obtained were observed by optical, scanning electron, and transmission electron microscopy.
{"title":"Laser surface alloying of iron and 1C–1–4Cr steel with carbon","authors":"A. Walker, D. West, W. Steen","doi":"10.1179/030716984803274882","DOIUrl":"https://doi.org/10.1179/030716984803274882","url":null,"abstract":"AbstractAn investigation is reported of the introduction of carbon into a pure iron and into a 1C-1·4Cr steel (S 135) by means of laser surface alloying. The procedure involved precoating the specimen surfaces with Dag graphite; successive laser surface-melting treatments (up to 12) were given, re-applying the graphite coatings between each treatment. Alloying was carried out both with shallow melt zones and with ‘keyhole’ zones. Substantial degrees of carbon alloying were achieved, ranging from hypo- to hypereutectic levels; the maximum obtained was ∼6%C. In the hypereutectic zones substantial cracking and porosity were encountered. The white iron structures obtained were observed by optical, scanning electron, and transmission electron microscopy.","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"17 1","pages":"399-404"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88714943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274422
Z. Palmai
AbstractThe phenomenon of the formation of a protective layer on conventional or coatedcarbide tools when machining specially deoxidized high-machinability steels has been known to exist for many years. The layer is a result of the smearing of silicate inclusions from the workpiece over the surface of the tool. Tests using TiN-coated M2 high-speed steel tools to turn conventional and high-machinability variants of the structural steel C45, combined with optical metallography and electron-microprobe studies, have shown that this phenomenon can also be observed on these tools and that the formation of a protective layer significantly increases the service life of the tip edge.
{"title":"Formation of non-metallic protective layers on high-speed steel tools","authors":"Z. Palmai","doi":"10.1179/030716984803274422","DOIUrl":"https://doi.org/10.1179/030716984803274422","url":null,"abstract":"AbstractThe phenomenon of the formation of a protective layer on conventional or coatedcarbide tools when machining specially deoxidized high-machinability steels has been known to exist for many years. The layer is a result of the smearing of silicate inclusions from the workpiece over the surface of the tool. Tests using TiN-coated M2 high-speed steel tools to turn conventional and high-machinability variants of the structural steel C45, combined with optical metallography and electron-microprobe studies, have shown that this phenomenon can also be observed on these tools and that the formation of a protective layer significantly increases the service life of the tip edge.","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"1969 1","pages":"34-37"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91379505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274954
D. Weckman, P. Niessen
AbstractThe existence and severity ql swlace defects such as cold shuts on direct-chill continuously cast products depend to a large extent on the heat-transfer conditions in the mould. An examination of the heat-transfer conditions at the mould/insert junction of a hot-top continuous-casting mould was performed as part of a study of the cold-shut formation mechanism on horizontal continuously cast 20 mm diameter lead, tin, and zinc alloy rods. It was found that there are two stages in the formation of a cold shut: intellace-controlled solidification, followed by diffusion-controlled solidification. The effective heat-transfer coefficient at the mould/insert junction lras found to be comparable to the very large values found during splat cooling. Using a steady-state numerical model of the solidification process, the concept of a critical casting speed for cold-shut formation was developed. If the actual casting speed is greater than this critical speed, cold shuts will not be produced. Alternatively, the...
{"title":"Heat-transfer conditions in hot-top mould and cold-shut formation mechanism on DC continuously cast non-ferrous alloy rods","authors":"D. Weckman, P. Niessen","doi":"10.1179/030716984803274954","DOIUrl":"https://doi.org/10.1179/030716984803274954","url":null,"abstract":"AbstractThe existence and severity ql swlace defects such as cold shuts on direct-chill continuously cast products depend to a large extent on the heat-transfer conditions in the mould. An examination of the heat-transfer conditions at the mould/insert junction of a hot-top continuous-casting mould was performed as part of a study of the cold-shut formation mechanism on horizontal continuously cast 20 mm diameter lead, tin, and zinc alloy rods. It was found that there are two stages in the formation of a cold shut: intellace-controlled solidification, followed by diffusion-controlled solidification. The effective heat-transfer coefficient at the mould/insert junction lras found to be comparable to the very large values found during splat cooling. Using a steady-state numerical model of the solidification process, the concept of a critical casting speed for cold-shut formation was developed. If the actual casting speed is greater than this critical speed, cold shuts will not be produced. Alternatively, the...","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"34 1","pages":"497-503"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86504357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274710
R. Horton
AbstractHeat recovery, insulation, and instrumentation for process control are examples of the technologies that can be applied to existing processes to make them more energy efficient. Many companies are already finding that techniques such as these can lead to large energy and cost savings. Having seen the benefits of implementing the more straightforward measures, an increasing number of industrialists are looking for new and more ambitious ways of saving energy. This is reflected in the growing numbers of equipment suppliers and consultants specializing in improving energy efficiency.
{"title":"Using energy more productively by modifying existing processes: an overview of how the mineral and metal industries can benefit","authors":"R. Horton","doi":"10.1179/030716984803274710","DOIUrl":"https://doi.org/10.1179/030716984803274710","url":null,"abstract":"AbstractHeat recovery, insulation, and instrumentation for process control are examples of the technologies that can be applied to existing processes to make them more energy efficient. Many companies are already finding that techniques such as these can lead to large energy and cost savings. Having seen the benefits of implementing the more straightforward measures, an increasing number of industrialists are looking for new and more ambitious ways of saving energy. This is reflected in the growing numbers of equipment suppliers and consultants specializing in improving energy efficiency.","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"3 1","pages":"405-410"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78699946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274585
M. Taha, M. Suéry
AbstractThe extrusion behaviour of semisolid Pb–19Sn alloys has been studied on materials with conventionally solidified dendritic structures and with non-dendritic structures obtained through mechanical stirring during solidification. This stirring performed at a constant temperature above the solidus produces a semisolid slurry with approximately spherical primary particles. The volume fraction, particle size, and interparticle spacing of the primary phase decrease as the stirring temperature increases. Whereas the alloy with the non-dendritic structure (rheocast) can be extruded in the semisolid state under low extrusion forces giving a perfectly continuous rod, the alloy with the dendritic structure requires larger forces and produces a fragmented product. These experiments suggest that extrusion can be performed advantageously in the semisolid state with alloys obtained by mechanical stirring during solidification.
{"title":"Structural characteristics and extrusion behaviour of Pb–Sn alloys in semisolid state","authors":"M. Taha, M. Suéry","doi":"10.1179/030716984803274585","DOIUrl":"https://doi.org/10.1179/030716984803274585","url":null,"abstract":"AbstractThe extrusion behaviour of semisolid Pb–19Sn alloys has been studied on materials with conventionally solidified dendritic structures and with non-dendritic structures obtained through mechanical stirring during solidification. This stirring performed at a constant temperature above the solidus produces a semisolid slurry with approximately spherical primary particles. The volume fraction, particle size, and interparticle spacing of the primary phase decrease as the stirring temperature increases. Whereas the alloy with the non-dendritic structure (rheocast) can be extruded in the semisolid state under low extrusion forces giving a perfectly continuous rod, the alloy with the dendritic structure requires larger forces and produces a fragmented product. These experiments suggest that extrusion can be performed advantageously in the semisolid state with alloys obtained by mechanical stirring during solidification.","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"25 1","pages":"226-230"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85018874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274693
B. Mintz
AbstractA review of the literature has shown that the k y value (Hall-Petch slope) for ferrite-pearlite steels is sensitive to small changes in composition and heat treatment, and can vary over a wide range from 14 to 24 MN m−2 mm1/2. Generally, however, the lower yield strength is only marginally influenced by this variation in k y value because of a strong inter-relationship between the k y value and σ0 (intercept in the Hall-Petch equation), such that high ky values are accompanied by low (σ0 values and vice versa. The variability in k y value value is believed to be caused by differences in the amount of interstitials (mainly carbon) present at the grain boundaries influencing the ease of nucleating dislocations from the boundary regions. Explanations to account for the differing degrees of interstitial segregation to the boundaries and the inter-relationship between k y value and σ0 value are presented and discussed.
对文献的回顾表明，铁素体-珠光体钢的k值(Hall-Petch斜率)对成分和热处理的微小变化很敏感，可以在14到24 MN m−2 mm /2的范围内变化。然而，一般来说，较低的屈服强度只受到ky值变化的轻微影响，因为ky值与σ0 (Hall-Petch方程中的截距)之间存在很强的相互关系，因此高的ky值伴随着低的σ0值，反之亦然。k y值的变化被认为是由于晶界上存在的间隙量(主要是碳)的差异引起的，这影响了晶界区域的形核位错的容易程度。给出并讨论了对边界间隙偏析程度不同的解释，以及k y值与σ0值之间的相互关系。
{"title":"Importance of k y (Hall-Petch slope) in determining strength of steels","authors":"B. Mintz","doi":"10.1179/030716984803274693","DOIUrl":"https://doi.org/10.1179/030716984803274693","url":null,"abstract":"AbstractA review of the literature has shown that the k y value (Hall-Petch slope) for ferrite-pearlite steels is sensitive to small changes in composition and heat treatment, and can vary over a wide range from 14 to 24 MN m−2 mm1/2. Generally, however, the lower yield strength is only marginally influenced by this variation in k y value because of a strong inter-relationship between the k y value and σ0 (intercept in the Hall-Petch equation), such that high ky values are accompanied by low (σ0 values and vice versa. The variability in k y value value is believed to be caused by differences in the amount of interstitials (mainly carbon) present at the grain boundaries influencing the ease of nucleating dislocations from the boundary regions. Explanations to account for the differing degrees of interstitial segregation to the boundaries and the inter-relationship between k y value and σ0 value are presented and discussed.","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"123 1","pages":"265-272"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83510552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274530
D. Allen, C. Earl
AbstractWhile the effects of welding parameters on the shapes of single weld beads have been extensively studied, less is known about how bead shape and penetration alter in multipass welding. In this paper are described studies on the shapes of overlapping beads in manual metal arc cladding of ferritic steel by austenitic stainless steel. Different deposition techniques were used to vary bead positioning and the degree of overlap, and the effects on bead height, width, penetration, and dilution were determined. It is shown that various changes in these parameters occur when weld beads are overlapped. The most important effect is a reduction in penetration and dilution, which is especially marked when the position of arc impingement is on the previous weld bead rather than the base plate. The implications for ultrasonic inspection of clad components, and for weld modelling, are discussed.
{"title":"Effects of overlap and deposition technique on weld-bead shape","authors":"D. Allen, C. Earl","doi":"10.1179/030716984803274530","DOIUrl":"https://doi.org/10.1179/030716984803274530","url":null,"abstract":"AbstractWhile the effects of welding parameters on the shapes of single weld beads have been extensively studied, less is known about how bead shape and penetration alter in multipass welding. In this paper are described studies on the shapes of overlapping beads in manual metal arc cladding of ferritic steel by austenitic stainless steel. Different deposition techniques were used to vary bead positioning and the degree of overlap, and the effects on bead height, width, penetration, and dilution were determined. It is shown that various changes in these parameters occur when weld beads are overlapped. The most important effect is a reduction in penetration and dilution, which is especially marked when the position of arc impingement is on the previous weld bead rather than the base plate. The implications for ultrasonic inspection of clad components, and for weld modelling, are discussed.","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"24 1","pages":"242-248"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79273328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1984-01-01DOI: 10.1179/030716984803274765
B. Mintz
AbstractThe influence of cooling rate from the normalizing temperature and tempering in the temperature range 450–600°C on the lower yield strength (LYS) and ultimate tensile strength (UTS) of two ferrite–pearlite structural steels has been examined. Falls in both LYS and UTS were obtained as a result of slow cooling or tempering; these falls were not related to grain-size changes. The processes controlling the falls in LYS and UTS were found to have activation energies of ∼170 kJ mol−1 and ∼290 kJ mol–1, respectively, and the kinetics of the processes obeyed t2/3 and t1/3 relationships, respectively (t being the time). The activation energy and kinetics for the process controlling the fall in UTS correspond to those associated with the spheroidization of pearlite, the rate-controlling factor being the self-diffusion of iron in the matrix, while the activation energy for the fall in LYS corresponds to that for diffusion of iron at the grain boundaries. An interesting relationship was also obtained between...
{"title":"Influence of cooling rate from normalizing temperature and tempering on strength of ferrite–pearlite steels","authors":"B. Mintz","doi":"10.1179/030716984803274765","DOIUrl":"https://doi.org/10.1179/030716984803274765","url":null,"abstract":"AbstractThe influence of cooling rate from the normalizing temperature and tempering in the temperature range 450–600°C on the lower yield strength (LYS) and ultimate tensile strength (UTS) of two ferrite–pearlite structural steels has been examined. Falls in both LYS and UTS were obtained as a result of slow cooling or tempering; these falls were not related to grain-size changes. The processes controlling the falls in LYS and UTS were found to have activation energies of ∼170 kJ mol−1 and ∼290 kJ mol–1, respectively, and the kinetics of the processes obeyed t2/3 and t1/3 relationships, respectively (t being the time). The activation energy and kinetics for the process controlling the fall in UTS correspond to those associated with the spheroidization of pearlite, the rate-controlling factor being the self-diffusion of iron in the matrix, while the activation energy for the fall in LYS corresponds to that for diffusion of iron at the grain boundaries. An interesting relationship was also obtained between...","PeriodicalId":18409,"journal":{"name":"Metals technology","volume":"31 1","pages":"52-60"},"PeriodicalIF":0.0,"publicationDate":"1984-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80951721","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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