The present work aims to investigate the effect of heating temperature(400,600 and 800°C)and inoculating elements(Ca,Ca-Ba,Ca-RE)on oxidation behavior of ductile irons containing 5.25%Si and 4.8%Si-2.3%Mo in dry ...The present work aims to investigate the effect of heating temperature(400,600 and 800°C)and inoculating elements(Ca,Ca-Ba,Ca-RE)on oxidation behavior of ductile irons containing 5.25%Si and 4.8%Si-2.3%Mo in dry air and combustion gas containing water vapour(natural gas burning).The oxidation is influenced by the gas atmosphere type,the iron alloying system,and the inoculating elements depending on the heating temperature.The weight gain increases from 0.001%-0.1%(400°C)to 0.05%-0.70%(600°C)and up to 0.10%-2.15%(800°C).No particular effects of the considered influencing factors are found when heating at 400°C,while at 600°C,mainly the oxidation gas atmosphere type shows a visible influence.At the highest heating temperature of 800°C,a limited increase of the weight gain is found for dry air atmosphere(up to 0.25%),but it drastically increases for combustion atmospheres(0.65%-2.15%).The water vapour presence in the combustion atmosphere is an important oxidising factor at 600-800°C.The alloying system appears to influence the oxidation behavior mainly at a heating temperature of 800°C in the combustion atmosphere,as evidenced by the lower weight gain in 5.25%silicon cast iron.Positive effects of inoculating elements increase with the heating temperature,with Ca and Ba-FeSi inoculation generally showing better performance.Irons inoculated with CaRE-FeSi exhibit a higher degree of oxidation.These results are in good relationship with the previous reported data:Ca-Ba-inoculation system appears to be better than simple Ca for improving the graphite parameters,while RE-bearing inoculant negatively affects the compactness degree of graphite particles in high-Si ductile irons.As the lower compactness degree is typical for graphite nodules in high-Si ductile irons,which negatively affects the oxidation resistance,it is necessary to employ specific metallurgical treatments to improve nodule quality.Inoculation,in particular,is a potential method to achieve this improvement.展开更多
The first part of the paper summarizes the performance of two mould devices,illustrating by representative shrinkage tendency results in ductile cast iron as affected by mould rigidity(green and furan resin sand mould...The first part of the paper summarizes the performance of two mould devices,illustrating by representative shrinkage tendency results in ductile cast iron as affected by mould rigidity(green and furan resin sand moulds)and inoculant type(FeSi-based alloys).Less rigid green sand moulds encourage the formation of contraction defects,not only because of the high initial expansion values(ε(di))(max),but also because of the increased solidification undercooling.A high inoculation efficiency means not only lowering the carbides formation sensitivity and increasing the nodule count,but also a prolonged graphitization through to the end of the eutectic freezing,as observed by the high population of small late forming nodules,which leads to minimizing the tendency for shrinkage.The second part of the paper illustrates an application of this equipment to commercial foundry use.It conducts thermal analysis and volume change measurements in a single ceramic cup with cast iron quality as a variable.La-bearing FeSi inoculant appears to be more effective than RE(Rare Earth)-FeSi alloy in FeSiMgCa treated irons(no RE),in terms of reducing eutectic undercooling and(ε(di))(max),favourable for lower sensitivity to shrinkage formation.Experiments also compared solidification patterns for white[WI],grey[GI]and ductile[DI]irons,to correlate the most important events between the cooling curves and contraction curves,to evaluate the sensitivity to shrinkage formation.All of the irons have similar values for initial expansion up to the start of eutectic freezing,but,after that,the graphite formation promotes expansion(more than 5 times for nodular graphite),resulting in a difference in maximum expansion(2 times higher for DI).The graphitic expansion has two contrary effects.Increased graphitic expansion(force)leads to a higher shrinkage sensitivity during the first part of the eutectic reaction,but also to a decrease of shrinkage at the end of solidification,due to forcing the last liquid iron to occupy the previous formed cavities.Consequently,strong graphitization process promotion at the end of solidification favours the castings'soundness.展开更多
The effect of addition of 0.05wt.% to 0.25 wt.% Ca,Zr,Al-FeSi alloy on in-ladle and in-mould inoculation of grey cast irons was investigated.In the present paper,the conclusions drawn are based on thermal analysis.For...The effect of addition of 0.05wt.% to 0.25 wt.% Ca,Zr,Al-FeSi alloy on in-ladle and in-mould inoculation of grey cast irons was investigated.In the present paper,the conclusions drawn are based on thermal analysis.For the solidification pattern,some specific cooling curves characteristics,such as the degree of undercooling at the beginning of eutectic solidif ication and at the end of solidifi cation,as well as the recalescence level,are identif ied to be more influenced by the inoculation technique.The degree of eutectic undercooling of the electrically melted base iron having 0.025% S,0.003% Al and 3.5% Ce is excessively high(39-40℃),generating a relatively high need for inoculation.Under these conditions,the in-mould inoculation has a more signif icant effect compared to ladle inoculation,especially at lower inoculant usage(less than 0.20 wt.%).Generally,the eff iciency of 0.05wt.% -0.15wt.% of alloy for in-mould inoculation is comparable to,or better than,that of 0.15wt.% -0.25wt.% addition in ladle inoculation procedures.In order to secure stable and controlled processes,representative thermal analysis parameters could be used,especially in thin wall grey iron castings production.展开更多
基金supported by a grant from National Program for Research of the National Association of Technical Universities-GNAC ARUT 2023.
文摘The present work aims to investigate the effect of heating temperature(400,600 and 800°C)and inoculating elements(Ca,Ca-Ba,Ca-RE)on oxidation behavior of ductile irons containing 5.25%Si and 4.8%Si-2.3%Mo in dry air and combustion gas containing water vapour(natural gas burning).The oxidation is influenced by the gas atmosphere type,the iron alloying system,and the inoculating elements depending on the heating temperature.The weight gain increases from 0.001%-0.1%(400°C)to 0.05%-0.70%(600°C)and up to 0.10%-2.15%(800°C).No particular effects of the considered influencing factors are found when heating at 400°C,while at 600°C,mainly the oxidation gas atmosphere type shows a visible influence.At the highest heating temperature of 800°C,a limited increase of the weight gain is found for dry air atmosphere(up to 0.25%),but it drastically increases for combustion atmospheres(0.65%-2.15%).The water vapour presence in the combustion atmosphere is an important oxidising factor at 600-800°C.The alloying system appears to influence the oxidation behavior mainly at a heating temperature of 800°C in the combustion atmosphere,as evidenced by the lower weight gain in 5.25%silicon cast iron.Positive effects of inoculating elements increase with the heating temperature,with Ca and Ba-FeSi inoculation generally showing better performance.Irons inoculated with CaRE-FeSi exhibit a higher degree of oxidation.These results are in good relationship with the previous reported data:Ca-Ba-inoculation system appears to be better than simple Ca for improving the graphite parameters,while RE-bearing inoculant negatively affects the compactness degree of graphite particles in high-Si ductile irons.As the lower compactness degree is typical for graphite nodules in high-Si ductile irons,which negatively affects the oxidation resistance,it is necessary to employ specific metallurgical treatments to improve nodule quality.Inoculation,in particular,is a potential method to achieve this improvement.
文摘The first part of the paper summarizes the performance of two mould devices,illustrating by representative shrinkage tendency results in ductile cast iron as affected by mould rigidity(green and furan resin sand moulds)and inoculant type(FeSi-based alloys).Less rigid green sand moulds encourage the formation of contraction defects,not only because of the high initial expansion values(ε(di))(max),but also because of the increased solidification undercooling.A high inoculation efficiency means not only lowering the carbides formation sensitivity and increasing the nodule count,but also a prolonged graphitization through to the end of the eutectic freezing,as observed by the high population of small late forming nodules,which leads to minimizing the tendency for shrinkage.The second part of the paper illustrates an application of this equipment to commercial foundry use.It conducts thermal analysis and volume change measurements in a single ceramic cup with cast iron quality as a variable.La-bearing FeSi inoculant appears to be more effective than RE(Rare Earth)-FeSi alloy in FeSiMgCa treated irons(no RE),in terms of reducing eutectic undercooling and(ε(di))(max),favourable for lower sensitivity to shrinkage formation.Experiments also compared solidification patterns for white[WI],grey[GI]and ductile[DI]irons,to correlate the most important events between the cooling curves and contraction curves,to evaluate the sensitivity to shrinkage formation.All of the irons have similar values for initial expansion up to the start of eutectic freezing,but,after that,the graphite formation promotes expansion(more than 5 times for nodular graphite),resulting in a difference in maximum expansion(2 times higher for DI).The graphitic expansion has two contrary effects.Increased graphitic expansion(force)leads to a higher shrinkage sensitivity during the first part of the eutectic reaction,but also to a decrease of shrinkage at the end of solidification,due to forcing the last liquid iron to occupy the previous formed cavities.Consequently,strong graphitization process promotion at the end of solidification favours the castings'soundness.
文摘The effect of addition of 0.05wt.% to 0.25 wt.% Ca,Zr,Al-FeSi alloy on in-ladle and in-mould inoculation of grey cast irons was investigated.In the present paper,the conclusions drawn are based on thermal analysis.For the solidification pattern,some specific cooling curves characteristics,such as the degree of undercooling at the beginning of eutectic solidif ication and at the end of solidifi cation,as well as the recalescence level,are identif ied to be more influenced by the inoculation technique.The degree of eutectic undercooling of the electrically melted base iron having 0.025% S,0.003% Al and 3.5% Ce is excessively high(39-40℃),generating a relatively high need for inoculation.Under these conditions,the in-mould inoculation has a more signif icant effect compared to ladle inoculation,especially at lower inoculant usage(less than 0.20 wt.%).Generally,the eff iciency of 0.05wt.% -0.15wt.% of alloy for in-mould inoculation is comparable to,or better than,that of 0.15wt.% -0.25wt.% addition in ladle inoculation procedures.In order to secure stable and controlled processes,representative thermal analysis parameters could be used,especially in thin wall grey iron castings production.