高温合金电磁软接触近净成形定向凝固研究

传统高温合金叶片类铸件制备过程中,熔体长时间受到陶瓷模壳材料的污染,性能难以提高,借助于电磁软接触成形技术中的电磁压力使高温合金熔体呈半悬浮状态,减少了熔体与磁模结晶器的接触面积和时间,提高了合金熔炼和成形的纯净度,同时将该技术和定向凝固技术相结合开发了一种实现高温合金复杂形状电磁软接触成形定向凝固的工艺,并探讨了该工艺下3种结晶器材料（陶瓷、磁模和石墨）中磁感应强度的分布规律,结果表明,石墨套高度对磁模结晶器磁感应强度的大小和分布以及熔体温度场有很大影响。通过调整上下线圈功率和抽拉速度等工艺参数成功地制备了大小两种近叶片形状的高温合金电磁软接触成形的定向凝固样件。．     

电磁连续铸造Sn-Pb空心管坯质量控制

为获得高质量的空心管坯，提出了在连续铸造过程中施加电磁场的空心管坯电磁连铸方法，并采用低熔点Sn—4．5％Pb(质量分数)合金模拟高熔点金属，研究了浇注系统及电磁场对空心管坯表面质量和宏观组织的影响．结果表明：在连续铸造过程中施加电磁场，可获得内外质量良好的空心管坯；当施加0．1kw的小功率电磁场时，可获得与强迫对流方向相反的V字型柱状晶组织；当功率增大到0．3kw时．内外相向生长的柱状晶变细变短，并在中部得到细小的等轴晶组织；采用小直径多浇口的雨淋式浇注系统和施加交变电磁场，有利于消除管坯内脏热节瘤，并得到周向均匀性较高的宏观凝固组织．     

电磁搅拌对BFe10-1-1白铜管坯的影响

采用试验的方法研究了在水平连铸过程中施加工频旋转电磁场对BFe10-1-1白铜管坯表面质量、凝固组织和力学性能的影响,并考察了电磁搅拌对管坯室温拉伸性能的影响.结果表明,采用水平电磁连铸短流程工艺能够制备出高质量的白铜管坯,电磁搅拌能够避免管坯表面热节瘤等缺陷的形成,同时促使粗大柱状晶发生细化,并使溶质元素宏观偏析得到了抑制;电磁搅拌能够提高管坯的抗拉强度和塑性,当线圈电流为100A时管坯抗拉强度较普通连铸坯提高了9%,而延伸率则提高了55%.     

0Cr17Mn14Mo2N空心管坯的电磁离心铸造

研究了稳衡电磁场的强度和作用时间对离心铸造０Ｃｒ１７Ｍｎ１４Ｍｏ２Ｎ空心管坯的组织和性能的影响。结果表明，适当的电磁搅拌可以细化组织，提高铸造坯的室温塑性。理论分析表明电磁搅拌引起熔体速度场和压力场的变化是铸坯组织与性能发生改变的主要原因。     

连铸空心管坯内置磁场搅拌器的优化设计

为了提高搅拌器的搅拌效率和使用寿命,以管坯内置磁场搅拌器为研究对象,用Sn-3.5%Pb合金代替钢液进行实验和数值模拟,借助Fluent和ANSYS软件研究了搅拌器的结构参数和电磁参数对金属液所受电磁力和流动状况的影响规律.结果表明:相比两相绕组,采用三相绕组的电磁搅拌器能效更高;磁轭结构对搅拌器的作用效果影响显著,为提高金属液所受电磁力应使磁轭的齿部尺寸尽量小些,但若尺寸太小会使磁轭饱和,影响磁轭的使用寿命;电流强度越大则金属液内的流速越大,电流强度与金属液流速呈线性变化,而电流频率与金属液流速呈非线性变化,电流强度对金属液流动的影响要大于电流频率.     

双金属复合材料双结晶器连铸工艺研究

本文总结双金属连铸技术的研究现状,提出双金属复合材料双结晶器连铸工艺.以Pb和Pb-Sn共晶合金作为试验材料,在自行设计和制造的双金属复合材料双结晶器连铸工艺试验样机进行研究.通过试验,得出以下结论,提出的双金属复合材料双结晶器连铸工艺是一种可行的新工艺,在自行设计和制造的双金属复合材料双结晶器连铸工艺试验样机适合于连铸低熔点双金属复合材料;获得了内坯Pb与包覆金属Pb-Sn合金之间为冶金结合的连铸复合坯;影响连铸复合坯质量的主要因素是两种金属的浇注温度和拉坯速度.     

国内外电磁搅拌技术的发展与展望

总结了电磁搅拌技术的发展、作用及其在国内外的应用，分析了组合式电磁搅／多模式电磁搅拌、电磁制动技术及连铸的软接触技术的特点，提出了关于优化鞍钢主要连铸生产线的几点建议。     

热顶电磁成型系统磁场的实验与数值模拟

根据电磁场理论,建立了热顶-电磁连铸成型系统的物理和数学模型,用小线圈法实测了不同电源功率时系统内的磁场强度,用有限元软件数值模拟了感应线圈高度、结晶器高度、热顶结构等对成型系统内磁感应强度和分布的影响,结果表明:1)降低结晶器高度使系统内磁感应强度增强,但不十分明显;2)感应线圈的高度对系统内磁场影响显著,采用20mm线圈较40mm线圈的磁感应强度提高约85%;3)有载时的模拟结果显示,系统内的磁场呈现更明显的趋肤效应;热顶结构对磁场的强度和分布规律无明显的影响.研究结果表明热顶电磁连铸法将有利于提高电源效率和稳定液柱高度,改善铸坯的内外部质量.     

电磁连铸颗粒增强铝基复合材料圆坯及其摩擦性能

Al-Zr(CO3)2体系原位反应合成法制备(Al2O3 Al3Zr)p/Al颗粒增强铝基复合材料圆坯,在合成及半连铸过程中施加低频电磁搅拌来改善增强相颗粒在铝基体内的分布状态,同时在结晶器初始凝固区域施加高频电磁场实现软接触连铸,以改善铸坯的表面质量.扫描电镜(SEM)分析显示:施加电磁搅拌后复合材料的凝固组织致密,颗粒增强相的体积分数增加,且颗粒细化、分布更趋于均匀.干滑动摩擦磨损实验表明:施加电磁搅拌后,复合材料的耐磨性能提高. 磨损表面的SEM分析显示粘着磨损比不施加电磁搅拌时明显减少,摩擦磨损机制以磨粒磨损为主.施加的高频磁场使得单纯使用低频电磁搅拌产生的表面粗糙现象消失,铸坯表面质量显著提高.     

中小尺寸高温合金件的无接触电磁成形

介绍了一种新型金属熔体无接触电磁成形技术及其原理,该技术将电磁铸造技术与高梯度定向凝固技术融为一体,对于熔化和成形活泼金属、高温合金难熔金属和高纯金属等中小尺寸构件具有重要的研究与应用价值。另外,从电磁场和凝固过程角度讨论了中小尺寸高温合金样件的电磁成形过程,探讨了工艺参数对成形过程的影响规律,并获得了表面质量较好的高温合金样法。     

A new method of continuous casting of copper billets by a combination of AC current and magnetic fields

A new method (AC + EMCC) was developed by directly applying alternative current (50 Hz) to the melt in the mold through the launder during electromagnetic continuous casting (EMCC) of copper billets. Effects of inputting AC current intensity on the solidification structure, tensile strength and surface quality of the billets were systematically investigated and discussed. An obvious improvement of surface quality and physical properties can be obtained with the combination of the AC current under optimized conditions of 360 A. The solidification structures are refined and homogeneously distributed due to the enhancement of electromagnetic forces. The mechanisms of grain refinement and interaction of AC current with the melt were analyzed.     

A new method of semi-continuous casting of AZ80 Mg alloy billets by a combination of electromagnetic and ultrasonic fields

The influence of low frequency electromagnetic field and power ultrasonic field on the microstructure of AZ80 Mg alloy billets was studied. The magnetic flux density and time average electromagnetic volume force density were obtained by numerical simulation. The acoustic pressure distribution was also numerically calculated in order to characterize the ultrasonic field propagation. After comparison of the different effects of grain refinement by low frequency electromagnetic casting (LFEC) and ultrasonic casting (UC), a new method (LFEC + UC) was developed by simultaneously applying ultrasonic vibration to the melt during low frequency electromagnetic semi-continuous casting of AZ80 Mg alloy billets. With the application of the compound field under the optimum conditions, the as-cast macrostructure and microstructure were refined and homogeneously distributed. An obvious improvement of mechanical properties was finally obtained. The mechanisms of grain refinement and interaction of low frequency electromagnetic field and power ultrasonic field with the melt were discussed.     

7075铝合金CREM铸锭的微观组织

实验研究了低频交变电磁场作用下，7075合金凝固壳高度以及微观组织的变化规律。结果表明，随磁场强度增大，凝固壳高度以及熔体与结晶 的接触高度减小，铸锭表面质量提高；相应地铸坯中近球形组织增加，蔷薇形组织减少，整体组织变得细小和均匀。     

Simulation study on horizontal continuous casting process of copper hollow billet under rotating electromagnetic stirring Part 2—effects of electromagnetic and casting parameters on solidification process

The comprehensive three-dimensional mathematical model proposed in Part 1 is used to investigate the effect of rotating electromagnetic stirring on the solidification process of copper hollow billet during horizontal continuous casting. In this part, the model is used to investigate the effects of electromagnetic parameters and casting speed on the electromagnetic field, temperature field, fluid flow and solidification during the horizontal continuous casting with rotating electromagnetic stirring. The results show that electromagnetic frequency, current intensity and casting speed have significant influence on the tangential velocity, temperature gradient, liquid fraction and sump depth.     

电磁场对铅黄铜水平连铸坯组织及偏析的影响

研究了铅黄铜在无磁场、低频交变电磁场下水平连铸得到的铸坯横截面宏观组织、微观组织形貌及合金元素Pb的分布,并对其机理进行了分析。试验结果表明,在铅黄铜水平连铸的过程中施加低频交变电磁场能有效地细化晶粒及影响合金元素在横截面上的分布,并且电磁场有效地抑制了在常规水平连铸过程中出现的铸坯横截面上中下部位组织分布不均匀的现象。表现在铸坯横截面的凝固组织由上方主要为细小柱状晶、下方为粗大柱状晶变为均为细小的等轴晶,铸锭上部凝固滞后的现象消除;合金元素Pb的宏观偏析得到抑制,并且电流为30Hz、100A的组织优于30Hz、80A的组织。     

Temperature control of TiAl melt during induction skull melting

Abstract

The properties of intermetallic compounds are sensitive to alloy composition and interstitial element content determined by the melting process. Induction skull melting is one of the best methods for melting reactive alloys. For induction heating under vacuum, melt temperature control is problematic. A numerical model for simulating temperature field during induction skull melting has been developed using the direct finite difference method. Factors such as water cooling boundaries, electromagnetic stirring meniscus, and power distribution in the charge were analysed. The chargecrucible interface was taken as a radiation boundary before melting and as a combined radiation and conduction boundary after melting. The free surface was taken as a radiation boundary. The relationship between the height of electromagnetic stirring meniscus and charge weight and melting power was reduced based on the conservation of mass. Based on the conservation of energy, the distribution density of induction current was ascertained. With the program, the relationship between melting power, charge weight, and melt temperature was established. During induction skull melting of gamma-TiAl based alloys, the melt temperature was measured carefully. The theoretical and experimental results were found to be in agreement.     

Study on Multiple Electromagnetic Continuous Casting of Aluminum Alloy

To obtain semi-solid Al alloy billet with high quality, an investigation was carried out by imposing a multiple magnetic field from the outside of a copper mold in the continuous casting. AISi6Mg2 alloy designed for semi-solid metal （SSM） processing was continuously cast through a submerged entry nozzle under various conditions. Effects of multiple magnetic field on meniscus motion, temperature distribution and billet quality were examined. The experimental results showed that meniscus disturbance caused by electromagnetic stirring could be controlled effectively and the surface quality of semi-solid AI alloy billet was improved greatly, and an uniformly fine, globular microstructure across the transverse section of the billet was achieved by optimizing the distribution of multiple magnetic field.