电脉冲对铸态高韧性球墨铸铁凝固组织及性能的影响
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摘要
对铸态高韧性球墨铸铁QT400-18的凝固过程进行电脉冲处理,电脉冲参数为电压2 600 V,频率0.88 Hz,电容200μF,处理时间15min。通过对比试验可知:电脉冲处理可使铸铁的过冷度相比未处理的升高12K,改善了石墨形核和生长的动力学条件,从而使球状石墨的粒径减小,石墨球数量增加。铸铁经过电脉冲处理,球化率由未处理的平均80%提高到平均91%,石墨球数由平均172/mm~2提高到209/mm~2,石墨不易变态生长,圆整度得到改善。同时,球墨铸铁的凝固组织得到了改善,铁素体数量增加,达到83%,相比未电脉冲处理的试样提高了26.6%,铁素体晶粒小于未处理试样,基体中分布的珠光体数量和片层间距减少,在抗拉强度符合要求的条件下,伸长率提高了4.89%,-233K的冲击功Akv提高了3.56J。
Cast high toughness ductile iron QT400-18 was treated by the electrical pulse.The electric pulse parameters were voltage 2 600 V,frequency 0.88 Hz,capacitance 200μF and the processing time 15 min.The results showed that the undercooling degrees of cast iron specimen treated by the electrical pulse increased 12 K comparing with the untreated one,for improving the graphite nucleation and the dynamic conditions of growth.Then the size of spherical graphite decreased and the number of nodular graphite increased.After the electric pulse treatment,the nodularity was increased from an average of 80% to 91% and the spherical graphite number was increased from 172/mm~2 to 209/mm~2.The graphite was not easy to abnormal growth and the roundness was improved.At the same time,the solidification structure of nodular cast iron has been changed,with the ferrite number increased,83%,compared to untreated specimen increasing 26.6%.The grain size of ferrite was less than that of untreated and the number and interlayer spacing of pearlite in the matrix decreased.The tensile strain increased by 4.89% and the impact work Akvat-233 K increased by 3.56 J.
Cast high toughness ductile iron QT400-18 was treated by the electrical pulse.The electric pulse parameters were voltage 2 600 V,frequency 0.88 Hz,capacitance 200μF and the processing time 15 min.The results showed that the undercooling degrees of cast iron specimen treated by the electrical pulse increased 12 K comparing with the untreated one,for improving the graphite nucleation and the dynamic conditions of growth.Then the size of spherical graphite decreased and the number of nodular graphite increased.After the electric pulse treatment,the nodularity was increased from an average of 80% to 91% and the spherical graphite number was increased from 172/mm~2 to 209/mm~2.The graphite was not easy to abnormal growth and the roundness was improved.At the same time,the solidification structure of nodular cast iron has been changed,with the ferrite number increased,83%,compared to untreated specimen increasing 26.6%.The grain size of ferrite was less than that of untreated and the number and interlayer spacing of pearlite in the matrix decreased.The tensile strain increased by 4.89% and the impact work Akvat-233 K increased by 3.56 J.
引文
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14 Margerie J C.The notion of heredity in cast iron[J].Metall Cast Iron,1974,15:546.
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16 Mueller B,Perepezko J.The undercooling of aluminum[J].Metall Mater Trans A,1991,22(1):1143.
17 Yan Hongchun,He Guanhu,Zhou Benlian,et al.The influence of pulse electric discharging on solidified structure of Sn-10%Pb alloy[J].Acta Metall Sin,1997,33(4):352(in Chinese).鄢红春,何冠虎,周本濂,等.脉冲电流对Sn-Pb合金凝固组织的影响[J].金属学报,1997,33(4):352.
2 Mesra A K.A novel solidification technique of metals and alloys under the influence of applied orienta[J].Metall Trans A,1985,16(7):1354.
3 Barnak J P,Sprecher A F,Conrad H.Colony(grain)size reduction in eutectic pb-sn castings by electroplusing[J].Scripts Metallurgicaet Mater,1995,32(6):879.
4 Masayuki Nakada,Yuh Shiohara,Merton C Flemings.Modification of solidification structures by pulse electric discharging[J].ISIJ Int,1990,30(1):27.
5 Gao M,He G H,Yang F,et al.Effect of electric current pulse on tensile strength and elongation of casting ZA27alloy[J].Mater Sci Eng A,2002,337(1-2):110.
6 Liao Xiliang,Zhai Qijie,Luo Jun,et al.Refining mechanism of the electric current pulse on the solidification structure of pure aluminum[J].Acta Mater,2007,55(9):3103.
7 Wang Jianzhong,Qi Jingang,Zhao Zuofu,et al.Effects of electric pulse modification on liquid structure of Al-5%Cu alloy[J].Trans Nonferrous Met Soc China,2013,23(9):2792.
8 Zhang Xifeng,Yuan Shouqian,Wei Yingjuan,et al.Influence of pulse current treatment method on solidified structure of a 45steel[J].Special Steel,2009,30(1):10(in Chinese).张西锋,袁守谦,魏颖娟,等.脉冲电流的不同处理方式对45钢凝固组织的影响[J].特殊钢,2009,30(1):10.
9 Tang Yong,Wang Jianzhong,Cang Daqiang,et al.Improvement of T8steel solidification structure by electropulse treatment[J].J University of Science and Technology Beijing,2000,22(4):307(in Chinese).唐勇,王建中,苍大强,等.电脉冲作用下T8钢凝固组织的改变[J].北京科技大学学报,2000,22(4):307.
10 Li Lingzhen,Zong Yanbing,Cui Heng,et al.Electropulse effect on macro solidification structure of hrb335steel[J].J University of Science and Technology Beijing,2004,26(5):478(in Chinese).李玲珍,宗燕兵,崔衡,等.电脉冲改善HRB335钢宏观凝固组织的作用[J].北京科技大学学报,2004,26(5):478.
11 Fan Jinhui,Li Renxing,Huo Xu,et al.Effects of pulse electric current with various parameters on solidification structure of Cr18Ni9Ti stainless steel[J].Foundry Technology,2003,24(6):534.范金辉,李仁兴,侯旭.不同参数脉冲电流对不锈钢Cr18Ni9Ti凝固组织的影响[J].铸造技术,2003,24(6):534.
12 Li Jianming,Li Shengli,Li Jin,et al.Modification of solidification structure by pulse electric discharging[J].Scripta Metallurgica et Materialia,1994,31(12):1691.
13 Conrad H.Influence of an electric or magnetic field on the liquid-solid transformation in materials and on the microstructure of the solid[J].Mater Sci Eng A,2000,287(2):205.
14 Margerie J C.The notion of heredity in cast iron[J].Metall Cast Iron,1974,15:546.
15 Kang H S,Yoon W Y,Kim K H,et al.Microstructure selections in the undercooled hypereutectic Al-Si alloys[J].Mater Sci Eng A,2005,404(1-2):117.
16 Mueller B,Perepezko J.The undercooling of aluminum[J].Metall Mater Trans A,1991,22(1):1143.
17 Yan Hongchun,He Guanhu,Zhou Benlian,et al.The influence of pulse electric discharging on solidified structure of Sn-10%Pb alloy[J].Acta Metall Sin,1997,33(4):352(in Chinese).鄢红春,何冠虎,周本濂,等.脉冲电流对Sn-Pb合金凝固组织的影响[J].金属学报,1997,33(4):352.