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
采用光学显微镜、扫描和透射电子显微镜研究了含Ca、Si镁合金的显微组织特征。铸态下,仅含Ca的镁合金主要由镁基体和晶界离异共晶组织(Mg+Mg2Ca)组成;加入约0.5%(质量分数)Si后,晶界离异共晶组织消失,在晶界附近及晶内形成弥散分布的细...采用光学显微镜、扫描和透射电子显微镜研究了含Ca、Si镁合金的显微组织特征。铸态下,仅含Ca的镁合金主要由镁基体和晶界离异共晶组织(Mg+Mg2Ca)组成;加入约0.5%(质量分数)Si后,晶界离异共晶组织消失,在晶界附近及晶内形成弥散分布的细小点状(球状)、针状和粗块状CaMgSi相;当含Si量较高(约1.0%)时,出现中国字形(针状)的Mg2Si相。固溶时效后,只含Ca的镁合金中晶界处离异共晶组织消失,代之以长大了的颗粒状Mg2Ca相;而Mg Ca Si合金的固溶时效组织较铸态无明显变化。对合金常温和高温短时拉伸性能也作了初步探讨。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.
文摘采用光学显微镜、扫描和透射电子显微镜研究了含Ca、Si镁合金的显微组织特征。铸态下,仅含Ca的镁合金主要由镁基体和晶界离异共晶组织(Mg+Mg2Ca)组成;加入约0.5%(质量分数)Si后,晶界离异共晶组织消失,在晶界附近及晶内形成弥散分布的细小点状(球状)、针状和粗块状CaMgSi相;当含Si量较高(约1.0%)时,出现中国字形(针状)的Mg2Si相。固溶时效后,只含Ca的镁合金中晶界处离异共晶组织消失,代之以长大了的颗粒状Mg2Ca相;而Mg Ca Si合金的固溶时效组织较铸态无明显变化。对合金常温和高温短时拉伸性能也作了初步探讨。
