无孕育蠕墨铸铁的热分析及凝固特性研究
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摘要
采用低镧镁硅铁合金对普通铁液进行无孕育蠕化处理,借助热分析方法研究了蠕铁铁液过冷度与凝固特性之间的相关性。结果表明,在宽泛的化学成分范围内,工业蠕铁的共晶转变平衡温度约为1 160℃,硅含量增多使铁液过冷度减小,而蠕化元素含量增加会加大铁液过冷倾向,蠕铁铁液的过冷度是硅含量和蠕化元素含量共同作用的结果。在非平衡条件下,蠕铁铁液在凝固时会析出大量树枝晶组织,凝固组织由奥氏体枝晶、形态不规则的蠕墨/奥氏体共晶团和少量球墨/奥氏体共晶团组成。随着蠕化剂加入量的增大,尽管铁液过冷度先增后降,但蠕化率单调下降,凝固组织显著细化。
In this syudy, molten iron was treated by using low lanthanum content magnesium ferrosilicon alloy without inoculation, and the correlations between undercoolings of the molten iron and solidification characteristics were researched with the help of thermal analysis technology. The results indicate that the eutectic equilibrium temperature of industrial vermicular graphite cast iron is approximately 1 160 ℃ in a wide range of molten iron chemical composition. The increase of silicon content causes the undercooling of the molten iron to decrease, while the increase of the vermicular elements content increases the supercooling tendency.Therefore, for vermicular graphite cast iron, the undercooling is affected by both the silicon content and the content of the vermicular elements. Under the condition of the non-equilibrium solidification, a large number of dendritic structures would form. In addition, the solidification microstructure consists of austenite dendrites,irregular vermicular graphite/austenite eutectic cells and a small amount of nodular graphite/austenite eutectic cells. With the increase of the addition amount of vermicularizing alloy, although the undercooling of the molten iron increases first and then decreases, the vermicularity would decrease monotonically, and the microstructures of the alloy are significantly refined.
In this syudy, molten iron was treated by using low lanthanum content magnesium ferrosilicon alloy without inoculation, and the correlations between undercoolings of the molten iron and solidification characteristics were researched with the help of thermal analysis technology. The results indicate that the eutectic equilibrium temperature of industrial vermicular graphite cast iron is approximately 1 160 ℃ in a wide range of molten iron chemical composition. The increase of silicon content causes the undercooling of the molten iron to decrease, while the increase of the vermicular elements content increases the supercooling tendency.Therefore, for vermicular graphite cast iron, the undercooling is affected by both the silicon content and the content of the vermicular elements. Under the condition of the non-equilibrium solidification, a large number of dendritic structures would form. In addition, the solidification microstructure consists of austenite dendrites,irregular vermicular graphite/austenite eutectic cells and a small amount of nodular graphite/austenite eutectic cells. With the increase of the addition amount of vermicularizing alloy, although the undercooling of the molten iron increases first and then decreases, the vermicularity would decrease monotonically, and the microstructures of the alloy are significantly refined.
引文
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[11]徐锦锋,梁敬凡,邱汉泉,等.低镧镁硅铁蠕化剂的蠕化处理特性研究[J].铸造,2018(9):772-777.
[12]徐锦锋,翟秋亚,袁森,等.过共晶球铁凝固过程中奥氏体的生长方式与形貌特征[J].金属学报,2003,39(2):136-139.
[13]LABRECQUE C,GAGNüM,Interpretation of cooling curves of cast irons:a literature review[J].AFS Transaction,1998,106:83-90.
[2]SHAO S,DAWSON S,LAMPIC M.The mechanical and physical properties of compacted graphite iron[J].Materialwissenschaft Und Werkstofftechnik,1998,29(8):397-411.
[3]STEFANESCU D M,JR C R L,VOIGT R C,et al.Cooling curve-structure analysis of compacted/vermicular graphite cast iron produced by different melt treatments[M].Transactions American Foundrymen's Society,1982,90:333-348.
[4]HOOSHYAR H H.Thermal analysis of compacted graphite iron[J].Advanced Materials Research,2011,60:1-47.
[5]LI Y X.Pattern recognition of thermal analysis cooling curves and quality evaluation of melt cast alloys[J].材料科学技术(英文版),2001,17(1):73-74.
[6]BARTOüOVüM,PRIBULOVA A,EPERJEüIütefan,et al.Analysis of cooling curves of nodular cast iron[J].Journal of Casting&Materials Engineering,2018,2(1):1-4.
[7]LIU J H,LI G L,ZHAO X B,et al.Effect of magnesium on characteristics of thermal analysis curve of compacted graphite iron[J].Advanced Materials Research,2011,284-286(3):1021-1024.
[8]SUN X J,LI Y X,CHEN X.Identification and evaluation of modification level for compacted graphite cast iron[J].Journal of Materials Processing Technology,2008,200(1-3):471-480.
[9]LIU J,YI L,LI G,et al.Influence of fading on characteristics of thermal analysis curve of compacted graphite iron[J].中国铸造,2011,8(3):295-299.
[10]溝渕纪夫,关欣.关于蠕墨铸铁的冷却曲线[J].铸造,1986(4):34-36.
[11]徐锦锋,梁敬凡,邱汉泉,等.低镧镁硅铁蠕化剂的蠕化处理特性研究[J].铸造,2018(9):772-777.
[12]徐锦锋,翟秋亚,袁森,等.过共晶球铁凝固过程中奥氏体的生长方式与形貌特征[J].金属学报,2003,39(2):136-139.
[13]LABRECQUE C,GAGNüM,Interpretation of cooling curves of cast irons:a literature review[J].AFS Transaction,1998,106:83-90.