电磁约束成形的技术特点及其发展前景

回顾了电磁约束成形技术的发展过程,通过分析圆形、椭圆形等不同横截面形状的纯铝、不锈钢以及高温合金等金属试样的电磁约束成形过程,从感应器结构、屏蔽罩插入深度、材料性状及抽拉速率等方面出发,详细论述了电磁约束成形定向凝固过程的技术特点,并阐述了电磁约束成形定向凝固技术的优缺点,指明了其今后的发展方向。     

高温合金真空电磁铸造补缩数学模型的建立与应用

为了提高高温合金母合金锭的内在质量,本文提出了高温合金的真空电磁铸造技术,并建立了表示高温合金真空电磁铸造凝固过程中液态金属补缩能力的数学模型。利用该模型比较了K417高温合金真空电磁铸造和真空熔铸两种铸造方法凝固过程中液态金属补缩能力的强弱,并通过试验验证了数学模型计算结果的准确性。试验结果表明:在高温合金凝固过程中施加60 A5、0 Hz的电磁搅拌,可以大幅提高液态金属的补缩能力,使高温合金母合金锭中心缩松和缩孔的比率从54%降低到33%,因而大幅提高了高温合金母合金锭的利用率。     

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。．     

合金电磁约束成形及凝固组织控制研究

介绍了铁、镍基合金等的无接触电磁约束成形定向凝固技术。在系统研究电磁场与温度场及其耦合作用的基础上，成功地实现了对多种截面形状的铝、不锈钢及高温合金的无容器电磁约束成形。     

金属熔体的电磁成形与凝固

材料的电磁加工是当今材料加工技术领域研究和发展的一个重点。本文简述作为材料电磁加工技术理论基础的电磁流体力学的基本内容，给出电磁场各种的基本原理，着重阐述电磁力和焦耳热在金属熔体电磁成形与凝固过程中的应用。     

K417高温合金母合金锭真空电磁净化技术研究

为了提高高温合金母合金锭的纯净度,本文提出了在高温合金真空熔铸的凝固过程施加旋转磁场的真空电磁净化技术。使用扫描电子显微镜和图像分析仪研究了K417高温合金母合金锭真空电磁净化技术的非金属夹杂物去除机理,结果表明:在K417高温合金母合金锭真空熔铸的凝固过程中施加旋转磁场能够促使非金属夹杂物向母合金锭中心部位快速聚集、变大并上浮到冒口处,最终在切除冒口的同时也将夹杂物从合金中除去。     

线性电磁搅拌对K417高温合金母合金锭质量的影响

为了提高高温合金母合金锭的质量,本文提出了在高温合金真空熔铸过程中,施加线性电磁搅拌的真空电磁铸造新技术。使用电子探针和光学显微镜,研究了在真空熔铸的凝固过程,施加工频线性电磁搅拌对K417高温合金母合金锭质量的影响。实验结果表明:在K417高温合金真空熔铸的凝固过程中施加140A的工频线性电磁搅拌,能够细化高温合金母合金锭的等轴晶组织、增加高温合金母合金锭的断面等轴晶比例、大幅减轻枝晶偏析的程度并能将高温合金母合金锭的中心缩松缩孔比率从54%降低到35%,从而使高温合金母合金锭的质量得到明显改善。     

金属熔体双频电磁成形的理论和试验研究

从固态金属感应加热熔化和液态金属电磁成形两个角度出发，讨论了金属熔体双频电磁成形中的频率选择，物理量的分布以及两种双频电磁成形的试验过程，结果表明：小尺寸复杂形状金属熔体电磁成形的最佳频率约在超音频的范围（f=10～100kHz），双频电磁力等物理量的分布是相应单频电磁力等物理量和与频率相关的三角函数的组合，在一定条件下，可简化为两个单频物理量的叠加。试验中成功地实现了双高频和高频一超音频两种双频电磁成形过程，高频一超音频双频电磁成形的工艺要优于双高频电磁成形的工艺，最后利用优化的双频电磁成形方案成功地实现了扁椭圆、弯月截面等复杂形状金属熔体双频电磁成形过程，获得了无模壳双频电磁成形的复杂截面形状样性。     

喷射成形高温合金的研究与应用

喷射成形是一种近终形快速凝固技术,综述了喷射成形高温合金的研究和应用.研究表明,喷射成形高温合金成分均匀、无宏观偏析、晶粒细小、气体夹杂含量低,力学性能与粉末合金相当,高于变形合金,冷热加工性能明显改善,且成本较低.喷射成形高温合金技术通过20多年的发展取得了较大的进步,包括纯洁金属喷射成形(CMSF)和纯洁金属成核铸造(CMNC).喷射成形高温合金的应用主要是管件、环形件和盘件.最后对喷射成形涡轮盘材料FGH96组织作了初步的研究.     

电磁搅拌作用下CoCrMo合金熔模铸件凝固细晶研究

目的 研究电磁搅拌对CoCrMo合金熔模铸件晶粒尺寸的影响,解决熔模铸造CoCrMo合金铸件晶粒粗大的问题。方法 将CoCrMo合金熔化后,在其凝固过程中分别施加不同工艺参数的电磁搅拌,并对其凝固后的组织进行表征分析。同时,采用有限元法对电磁搅拌在金属熔体中的电磁场和流场进行数值模拟。结果 在不同的电磁搅拌参数下,CoCrMo合金铸件凝固组织出现了不同程度的细晶效果,浇道处的细晶效果优于铸件试棒处的。铸件试棒处的晶粒尺寸最小能控制在1 mm以下,等轴晶率最高能提升至31%。数值模拟结果表明,在电磁搅拌过程中,铸件试棒的磁场、电流和洛伦兹力都呈周期性变化,铸件试棒内部的流速随搅拌时间的延长而增大,最后趋于稳定。结论 电磁搅拌对CoCrMo合金的凝固组织产生了明显的细化效果,促进了柱状晶向等轴晶转变。电磁搅拌的时间越长,铸件凝固组织的细化效果越好,铸件厚大部位的细晶效果越显著。结合实验结果和数值模拟结果发现,在电磁搅拌过程中,熔体流动引发枝晶断裂是晶粒细化的主要原因,而电磁场促进异质形核为次要原因。     

Research on vacuum-electromagnetic casting of IN100 superalloy ingots

In order to improve the inner quality of superalloy master alloy ingots, the new technology of superalloy vacuum-electromagnetic casting, i.e. applying electromagnetic stirring (EMS) to the solidification process of superalloy vacuum casting was developed. The effect of EMS on the inner quality of IN100 superalloy ingots was studied with EPMA and optical microscope. The results show that while an EMS with 50 Hz frequency and 60 A current is imposed, the equiax crystals of IN100 superalloy ingots can be effectively refined and increased, and the central shrinkage porosity and the dendritic segregation of IN100 superalloy ingots are greatly reduced, so the inner quality of IN100 superalloy ingots is obviously improved.     

金属熔体电磁成形过程研究

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 .     

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.     

Grain Size Control of Semisolid A356 Alloy Manufactured by Electromagnetic Stirring

To investigate the possibility of substituting the mechanical stirring system with electromagnetic stirring (EMS) system for aluminum rheo die-casting, the EMS under the different stirring cooling conditions was carried out. It was found that in the early period of solidification, the dendrite breakages led to a fine primary phase. When dendrites grew coarsely, the effect of ripening on grain size overwhelmed that of dendrite breakage. It was also found that the high cooling rate favored large nucleation rate, and led to a fine primary phase. But high cooling rate also made the growth rate of the dendrite arm, which prevented the dendrite arm from being sheared off. Therefore there were a suitable stirring time and suitable cooling rate to obtain the best rheo die-casting structure. Qualified semisolid A356 aluminum alloy was successfully manufactured with short time EMS.     

Experimental investigation of the hot cracking mechanism in welds on the microscopic scale

The results of the accurate experimental observations on binary Al-Si alloys are presented, which clearly demonstrate that the solidification cracking is a result of the accumulation of macroscopic tensile displacement in aβmicroscopic intergranular liquid film of segregates at the final stage of the weld metal solidification. The reconstructed mechanism of crack initiation provides a clear phenomenological interrelation between the cracking susceptibility, parameters of the welding process and properties of the base and filler material. The correspondent numerical model takes into account the effects of displacement accumulation as well as the influence of thermo-dynamical and thermo-mechanical properties of the welded material. It is successfully applied for development of technological means for elimination of the solidification cracking during welding of aluminium alloys AA6056, such as a multi-beam welding.     

组合电磁场在材料凝固过程中的应用和发展

组合电磁场是指通过2个或者2个以上励磁线圈,产生2个或2个以上交互作用的电磁场,并将交互作用的电磁场作用于材料制备过程.组合电磁场在金属凝固过程中的应用可为开发新材料、优化材料制备工艺、提高金属材料制品的综合质量和解决金属材料在制备过程中的技术难题提供新的手段和方法.组合磁场在材料凝固过程中的应用必将成为材料研究领域的新方向.     

Direct Generation of Internse Compression Waves in Molten Metals by Using a High Static Magnetic Field and Their Application

Compression waves propagating through molten metals are contributed to degassing accelerating reaction rate,removing exclusions from molten metals and refining solidifcation structures during metallurgical processing of materials,In the present study ,two electromagnetic methods are proposed to generate intense compression waves directly in liquid metals.One is the simultaneous imposition of a high frequency electrical current filed and a static magnetic field ;the other is that of a high frequency magnetic field and a static magnetic field ,A mathematical model based on compressible fluid dynamics and electromagnetic fileds theory has been developed to derive pressure distri-butions of the generated waves in a metal.It shows that the intensity of compression waves is proportional to that of the high frequency electromagnetic force,And the frequency is the same as that of the imposed electromagnetic force,On the basis of theoretical analyses ,pressure change in liquid gallium was examined by a pressure transducer under various conditions.The observed results approximately agreed with the predictions derived from the theoretical analyses and calculations.Moreover,the effect of the generated waves on improvement of solidification structures was also examined .It shows that the generated compression waves can refine solidification structures when they were applied to solidification process of Sn-Pb alloy ,This study indicates a new method to generate compression waves by imposing high frequency electromagnetic force locally on molten metals and this kind of compression waves can probably overcome the difficulties when waves are excited by mechanical vibration in high temperature environments.