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金属熔体电磁成形过程研究 总被引:1,自引:0,他引:1
以制备无污染的航空发动机叶片为背景 ,分析了金属熔体电磁成形定向凝固技术的原理 ,并以铝合金及 1Cr1 8Ni9Ti为研究材料 ,探讨了交流电磁场作用下金属熔体的感应加热熔化及约束成形过程 ,结果表明 :感应器结构决定其内部的磁场及电磁压力分布 ,感应器输入功率、熔体高度、上下液固界面位置、抽拉速度及冷却条件等参数综合影响金属加热熔化特性、熔体形状及其稳定性 ;通过控制合理的工艺参数 ,获得了截面为圆形及近似弯月面形、表面质量和内部定向组织良好的样件 . 相似文献
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TiAl基合金冷坩埚定向凝固研究现状与发展趋势 总被引:1,自引:0,他引:1
冷坩埚定向凝固技术基于材料电磁加工原理,将合金连续熔化、电磁约束成形和连续凝固过程统一,避免模壳法定向凝固造成的合金熔体污染,是TiAl等高活性合金高纯净定向凝固的重要方法之一。报告了TiAl基合金冷坩埚定向凝固技术的研究结果,建立了电磁场、温度场与电磁冷坩埚系统主要参数之间的规律性关系。通过改变冷坩埚的横截面形状,初步制备出具有定向凝固组织的TiAl基合金圆、方和扁锭,研究结果表明该方法不但适合于Ti-Al二元合金,而且施与多元多相TiAl基合金也是可行的。通过对成分和组织的控制,所研究的TiAl基合金定向凝固试样的室温拉伸塑性最高达到1.5%左右。最后指出将该方法应用于耐高温的轻质高Nb含量的γ-TiAlNb合金的定向凝固是未来的发展趋势。 相似文献
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定向凝固和单晶高温合金及涡轮叶片的发展 总被引:6,自引:0,他引:6
北京航空材料研究所对定向凝固及单晶高温合金及工艺进行了多年卓有成效的研究,建立了先进的定向凝固设备,发展了定向凝固工艺,研制了一系列高性能定向和单晶高温合金;对合金设计、热处理、合金元素的作用进行了分析研究,为确定合适的化学成分及选定最佳工艺参数提供了可靠的基础;进行了精密铸造工艺的研究,发展了无余量铸造技术和用于定向及单晶的陶瓷型壳和型芯,并用此发展了多种航空定向和单晶叶片,特别是研制和批生产了用于先进航空发动机的DZ22无余量具有复杂内冷通道的空心涡轮叶片。现在,其主要目标是研制无余量的单晶空心叶片及其他单晶课题。 相似文献
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主要论述水冷铜坩埚内的Czochralski定向凝固、电子束定向凝固、光悬浮定向凝固、整体定向凝固和电磁冷坩埚定向凝固5种定向凝固的基本原理,优缺点以及研究定向凝固Nb-Si基超高温合金所取得的进展。现阶段,基本不用Czochralski定向凝固和电子束定向凝固研究Nb-Si基超高温合金了;到目前为止,光悬浮定向凝固是制备研究Nb-Si基超高温合金的主要手段;整体定向凝固制备的Nb-Si基超高温合金的断裂韧性已达20MPa·m1/2左右;电磁冷坩埚定向凝固制备的Nb-Si基超高温合金的高温拉伸强度已达200MPa(1250℃)。 相似文献
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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. 相似文献
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Possible occupational health or public health risks due to video display terminals (VDTs) are addressed. The authors note the errors of current jargon and correctly define the terms needed to describe the fringing magnetic flux density near any magnetically deflected, raster scan, cathode ray tube display. Theory and preliminary measurements have shown that the ELF AC electric field related to VDT display electronics is small, and the electromagnetic field strength at any frequency is truly negligible as an occupational health risk near any cathode ray tube display. Application of Maxwell's equations shows that the commonly used pickup coil responds to the derivative of magnetic flux density. The transducer needs an integrator to respond properly to the sawtooth waveforms of deflection fields. Correct measurements of VDT fringing magnetic fields are presented. A Swedish test method is briefly discussed. The conclusion from this work is strong. Theory and these measurements show there is not a verifiable occupational health risk from the fringing ELF electric or magnetic fields or any frequency electromagnetic fields near VDTs 相似文献
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Distribution of magnetic field and electromagnetic force in twin-roll casting of steels was studied by the metod of numerical simulation in this paper,Two-dimension finite element model ,which includes the regions of melt ,stainless collar ,coil and magnetic core ,has been constructed,By solving magnetic vector potential formulations of quasi-static electromagnetic field,distribution of magnetic flux density and magnetic force at different molten heigh is determined,Calculated results showed that intensity of the distribution of magnetic flux density increased linearly with the increased coil current ;and the magnetic force in the melt increased as a quadratic cure with creased coil current ,More attention was given to the distribution of eddy current and magnetic force in the melt ,the confine effect at different molten height was also discussed. 相似文献
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目的研究不同石墨铸型材料对钛合金内环铸件冶金质量的影响。方法试验选取颗粒直径分别2,0.8,0.04 mm的3种典型石墨材料,制备内环石墨铸型,采用离心浇注,然后对3种不同石墨材质研制的ZTC4钛合金铸件进行表面目视检验、荧光和X光检测。结果 2,0.8,0.04 mm这3种颗粒直径的石墨铸型材质研制的铸件表面外观和荧光质量依次提高,其中荧光缺陷平均数量依次为21.4,13.9,2.2个/件;铸件内部缺陷数量均小于1.5个/件,夹杂均小于0.7个/件。结论不同颗粒度直径的石墨铸型对铸件的外观和荧光质量会产生显著的影响,而对铸件内部冶金质量影响较小。 相似文献
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Use of vacuum for counter-gravity casting of metals 总被引:2,自引:0,他引:2
G. Dixon Chandley 《Materials Research Innovations》1999,3(1):14-23
The use of vacuum to fill molds to form investment castings in a countergravity casting fashion was started in the early
1970s. This paper describes how the processes work and the reasons for their advantages in cost, quality, and process control.
Countergravity casting is being done in sand, permanent, and investment (lost wax) ceramic molds and alloys are cast in air
and inert atmospheres. The process started with common steels, was extended to heat resistant superalloys, and recently even
titanium alloys are being cast routinely using ceramic crucibles. The use of a unique mold design enables a great reduction
in metal cast to yield a given part, thereby greatly reducing the energy use in making such castings. Computerized control
of the rate of vacuum application enables complete control of filling rates, permitting casting of very high quality castings
in very viscuous metals, such as metal matrix composites of aluminum. These processes are used to produce more than $200 million
worth of castings annually and this will greatly increase in the next few years due to the production of automotive exhaust
manifolds in stainless steel.
Received: 21 July 1998 / Accepted: 10 September 1998 相似文献
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A coupled boundary element (BE)-impedance boundary condition (IBC) formulation is used to develop an electromagnetic mold design model, taking into consideration the problem of predicting the shape of the free boundary. The computational model of the electromagnetic mold consists of a right cylindrical conductor, representing the molten metal, coaxial with an induction coil, generally having a single turn, and a field shaping short circuited turn. The IBC is applied to the high-resistivity molten metal region, and the full BE formulation is used for the field shaping turn. An iterative procedure is developed to predict the shape of the molten metal free surface by satisfying the balance between the electromagnetic and gravitational pressures. Results showing the effects of the single turn confinement coil and shielding turn placement on the electromagnetic pressure distributions and on the shape of the free surface are presented 相似文献
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Jing YU Qingyan XU Kai CUI Baicheng LIU Akihiko KIMATSUKA 《材料科学技术学报》2007,23(1):47-54
Bridgman directional solidification of investment castings is a key technology for the production of reliable and highly efficient gas turbine blades. In this paper, a mathematical model for three-dimensional (3D) simulation of solidification process of single crystal investment castings was developed based on basic heat transfer equations. Complex heat radiation among the multiple blade castings and the furnace wall was considered in the model. Temperature distribution and temperature gradient in superalloy investment castings of single blade and multiple ones were investigated, respectively. The calculated cooling curves were compared with the experimental results and agreed well with the latter. It is indicated that the unsymmetrical temperature distribution and curved liquid-solid interface caused by the circle distribution of multiple turbine blades are probably main reasons why the stray grain and other casting defects occur in the turbine blade. 相似文献
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The regional flux density in laminations of soft magnetic materials is usually determined by means of a single-winding coil inserted through drilled holes. An alternative method is to use needle contacts arranged at lamination surface points through the surface coating. This method is simple and nondestructive. However, concern exists whether the results of measurements are fully equivalent with results from the coil method. We show here that full equivalence can be expected in most cases. The test results prove to be fully equivalent if the investigated region exhibits quasi-homogeneous induction or linear induction variations. If the region encloses a local induction extremum, a systematic error arises, but it can be neglected in practice. On the other hand, strong errors may arise if the in-plane flux is combined with asymmetric off-plane flux. This is because the method takes advantage of the surface eddy-current configuration, which reflects both components of flux. 相似文献
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The relationship between melt shape, electromagnetic pressure and magnetic field is studied for electromagnetic confinement and shaping of plate-form part. The results of experimental observation and theoretical inference can be summarized as follows. As the melt thickness a is large enough, causing the ratio of plate thickness to current theoretic skin depth a/delta larger than 2.2, the electromagnetic pressure acting on melt can be simply expressed as P-m = B-2/2 mu, and the melt shape would be known only by measuring the distribution of magnetic flux density As a is small and makes the ratio a/delta less than 2.2, the melt shape and electromagnetic pressure for confining and shaping are determined not only by magnetic flux density B but also by melt thickness a, electromagnetic parameter mu gamma and current frequency f. In this paper, an equation used to calculate electromagnetic pressure acting on "thin plate-form melt" is brought forward. The equation gives a precise relationship between electromagnetic pressure factor p and melt thickness a, electromagnetic parameter mu gamma and current frequency f. 相似文献