As-cast and heat-treated 400-18 ductile iron （DI） grade was obtained in different foundry conditions, as metallic charge, Mg-treatment alloy and inoculation. It was found that the Pearlitic Influence Factor （P） an...As-cast and heat-treated 400-18 ductile iron （DI） grade was obtained in different foundry conditions, as metallic charge, Mg-treatment alloy and inoculation. It was found that the Pearlitic Influence Factor （P） and Anti- nodulizing Complex Factor （K1） have an important influence on property of DI, depending on the Mn and P level, the metallurgical quality of iron melt, rare earth （RE） and inoculation. It was also found that the influence of Mn is depended on the phosphorus and residual elements level in ductile iron. Less than 0.03%P and 0.2%Mn and P〈2.0 are the basic conditions to obtain as-cast ferritic structure. At the same lower level of Mn and P, the increasing of residual elements （P〉2.0） determines presence of pearlite in as-cast structure, while ferrite structure is obtained after a short annealing heat treatment. Lower level of phosphorus （P〈0.025%） and residual elements （Px〈2.0） allow to use relative high Mn content （0.32%-0.38%）, in condition of ferritic structure, including in as-cast state. High P （0.04%- 0.045%） and Mn （0.25%-0.35%） content stabilized peadite, especially at lower level of residual elements （P 〈2.0）. Antinodulizing action of elements was counteracted up to K1=2.0 level, by RE included in Mg-treatment alloy, which are beneficial for K1〈1.2 and compulsory for K1〉1.2. Si has a significant influence on the mechanical properties of heat treated ductile irons： an important decreasing of elongation level and a moderate increasing of yield and tensile strength and their ratio in 150-170 HB typical hardness field. A typical final chemical composition for as-cast 400-18 ductile iron could include 3.5%-3.7%C, 2.4%-2.5%Si, max.0.18%Mn, max.0.025%P, max.0.01%S, 0.04%-0.05%Mg for Px〈1.5 and K1〈1.1. High purity pig iron, RE-bearing FeSiMg and powerful inoculant are also recommended.展开更多
During the production of SG iron, the selection of raw materials and control of chemical composition are most important. From the very early days of SG iron production, the effects of trace elements on graphite form a...During the production of SG iron, the selection of raw materials and control of chemical composition are most important. From the very early days of SG iron production, the effects of trace elements on graphite form and matrix structure have been studied, and the allowable concentration limits for their detrimental influence has been decreased year by year, during the last fifty years. This paper has reviewed some of the suggested SG iron trace elements in the literature and in several Chinese foundries. It was found that for most SG iron castings, rare earth elements are still required to neutralize the harmful effects of trace elements and improve SG iron quality. It also found that the use of high purity and ultra-high purity base iron melts enabled integrated, safety-critical and complicated SG iron castings of varying thickness, and heavy-section, to be produced successfully. These SG iron castings have surprisingly good structures, and their mechanical and dynamic properties are vastly superior to those specified in current international SG iron standards. Further study is required on the effects of using high purity and ultra-high purity base melts on the structure and properties of SG iron.展开更多
文摘As-cast and heat-treated 400-18 ductile iron （DI） grade was obtained in different foundry conditions, as metallic charge, Mg-treatment alloy and inoculation. It was found that the Pearlitic Influence Factor （P） and Anti- nodulizing Complex Factor （K1） have an important influence on property of DI, depending on the Mn and P level, the metallurgical quality of iron melt, rare earth （RE） and inoculation. It was also found that the influence of Mn is depended on the phosphorus and residual elements level in ductile iron. Less than 0.03%P and 0.2%Mn and P〈2.0 are the basic conditions to obtain as-cast ferritic structure. At the same lower level of Mn and P, the increasing of residual elements （P〉2.0） determines presence of pearlite in as-cast structure, while ferrite structure is obtained after a short annealing heat treatment. Lower level of phosphorus （P〈0.025%） and residual elements （Px〈2.0） allow to use relative high Mn content （0.32%-0.38%）, in condition of ferritic structure, including in as-cast state. High P （0.04%- 0.045%） and Mn （0.25%-0.35%） content stabilized peadite, especially at lower level of residual elements （P 〈2.0）. Antinodulizing action of elements was counteracted up to K1=2.0 level, by RE included in Mg-treatment alloy, which are beneficial for K1〈1.2 and compulsory for K1〉1.2. Si has a significant influence on the mechanical properties of heat treated ductile irons： an important decreasing of elongation level and a moderate increasing of yield and tensile strength and their ratio in 150-170 HB typical hardness field. A typical final chemical composition for as-cast 400-18 ductile iron could include 3.5%-3.7%C, 2.4%-2.5%Si, max.0.18%Mn, max.0.025%P, max.0.01%S, 0.04%-0.05%Mg for Px〈1.5 and K1〈1.1. High purity pig iron, RE-bearing FeSiMg and powerful inoculant are also recommended.
文摘During the production of SG iron, the selection of raw materials and control of chemical composition are most important. From the very early days of SG iron production, the effects of trace elements on graphite form and matrix structure have been studied, and the allowable concentration limits for their detrimental influence has been decreased year by year, during the last fifty years. This paper has reviewed some of the suggested SG iron trace elements in the literature and in several Chinese foundries. It was found that for most SG iron castings, rare earth elements are still required to neutralize the harmful effects of trace elements and improve SG iron quality. It also found that the use of high purity and ultra-high purity base iron melts enabled integrated, safety-critical and complicated SG iron castings of varying thickness, and heavy-section, to be produced successfully. These SG iron castings have surprisingly good structures, and their mechanical and dynamic properties are vastly superior to those specified in current international SG iron standards. Further study is required on the effects of using high purity and ultra-high purity base melts on the structure and properties of SG iron.
