【作者】 张兴国；

【导师】 金俊泽；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2001， 博士

【摘要】 电磁铸造是建立在电磁流体力学基础上，并与冶金工程相结合的先进材料加工方法，具有产品表面光亮、机械性能好和生产效率高等突出的优点。本文以实现铝合金电磁铸造技术工程化为着眼点，系统地研究了电磁铸造的基本理论和工艺过程，主要包括以下方面： 1．根据电磁场理论，提出电磁成型系统等效电路模型；计算出铝合金扁锭的感应器电流、电源频率、功率和能耗等电参数；建立了具有工业规模的电磁铸造成套装置。 2．液柱的稳定成型是电磁铸造技术的关键。本文在Russia和Kaiser型感应器的基础上，以实验和数值模拟相结合的方法，分析多种感应器结构的磁场分布特性，以电磁压力与静压力平衡为基准点，设计出独特的直边圆弧电磁感应器，其形成的液柱侧面垂直，表面稳定，为实现铝合金的电磁铸造奠定了基础。 3．独特地采用分层隔离法，通过测量模拟铸锭内的温度分布，依据焦耳-楞次定律，计算了扁锭电磁铸造中感应电流密度分布、感应加热功率和速率；用有限差分法对电磁铸造中的温度场进行数值模拟，研究了浇注温度、冷却强度、冷却位置等对铸造速度、液柱高度、液穴形状的影响，为铸造工艺参数的选择提供了依据；计算结果与实测结果相吻合。 4．采用互感耦合模型，进行了电磁铸造中电磁场的数值模拟计算，研究了感应器结构、感应器电流、屏蔽罩位置、电源频率等对磁场强度分布的影响，计算了有载条件下的半悬浮液柱形状；计算结果与实验结果基本吻合。 5．探讨了铝合金电磁铸造工艺。依据液柱形状评价参数S_A，确定了感应器电流、屏蔽罩位置和液柱高度等关键参数；通过理论分析和温度场实测及拉坯试验，根据表面温度均一的准则，设计出合理的冷却水强度分布；确定了浇注温度、液柱高度、冷却水量、铸造速度等关键工艺参数间的匹配关系；将浮漂液位控制器应用于电磁铸造，制造出工业规模的纯铝和3004铝合金扁锭(520×130×900mm)及2024、5182、6063铝合金圆锭(φ174×1000mm)。 6．在国内首次探讨了一机双锭电磁铸造的基本技术问题，采用感应器串联的方法，一机同时铸造出两支尺寸为φ260mm的纯铝圆锭，为实现一机多锭电磁铸造提供了依据。 7．分析了电磁铸造铸锭的表面和内部质量，并与连续铸造铸锭进行 大连理工大学博士学位论文了对比。结果表明，电磁铸造铸锭的表面粗糙度仅为h．65 u m（7 7－78）；宏观组织为细小、均匀的等轴晶；其抗拉强度比连铸坯提高25－27％，延伸率提高20－200％。8．首次提出铝薄板热顶一电磁铸造方法。其原理是将液柱分成两个不同的控制区域：l）液柱顶部用结构独特的屏蔽罩和耐火材料制成的热顶约束成型，解决了液流均匀分配难题和流量微小变化引起液柱高度大幅波动的问题；2）液柱下部由电磁力约束成型，凝固前仍然保持半悬浮状态，凝固后仍具有表面光亮、内部组织均匀、致密的电磁铸造的优点。设计出独特的热顶－电磁成型系统；根据成型控制条件确定了液柱高度和感应器电流；通过温度场的数值模拟对工艺参数进行数值优化；成功制造出国内第一支尺寸为 480 X 20 X 850nun铝薄板。热顶一电磁铸造法用于其它尺寸和合金的电磁铸造将进一步简化工艺、改善表面质量。9．依据电磁场理论，提出复合电磁感应器设计思想，即用普通电磁线圈产生原发磁场，用复合线圈减小系统磁阻，并产生附加磁场；计算出复合线圈的尺寸；研究了复合线圈厚度、结构、位置。间隙、感应器电流、匝数和组合方式等对磁场强度分布的影响；首次制作出复合电磁成型系统，使磁场强度提高到原成型系统的2．7倍；使与钢物性相近的金属锡呈半悬浮状态，揭示了低能耗钢电磁铸造的可能性。 最后，本文分析了铝合金电磁铸造存在的问题和应用前景，并对，钢电磁铸造需解决的关键技术问题和可行性进行了展望。更多还原

【Abstract】 Electromagnetic casting (EMC) is a new material processing method, a comprehensive subject based on magnetohydrodynamics and combined with metallurgical engineering. The outstanding merits of EMC lie in its high smooth surface, good mechanical properties and high production efficiency.In this paper, the engineering application of EMC technology in our country has been respected and its theory and technology process has been systematically researched. The main results are as follows:1. A physical model of equivalent circuit has been built based on the electromagnetic field theory. The electric parameters such as inductor current, power frequency and energy consumption etc. have been preliminarily estimated. As a result, a pilot plant of EMC is established.2. The stability and molding of semi-levitated liquid column is a key to the success of EMC. Based on the Kaiser and Russia types usually used abroad, by the method of detail experimental combined the simulation of magnetic intensity distribution and liquid column shape analysis, a special arc inductor has been designed to ensure the formation of the semi-levitated liquid column, whose side is vertical and surface is stable. All these results provided the foundation for the EMC of Aluminum alloy.3. A specific layered isolating method has been used to measure the temperature and its gradient distribution of simulated ingot. Based on the results above, the induced current intensity distribution and the induced heating rate within the EMC slab has been calculated according to the Joul-Lenzs laws. Moreover, the temperature field within EMC ingot has been numerically simulated . To provide the choice basis for the technology parameters, the pouring temperature, cooling intensity and position has been studied to investigate their influence on the casting speed, liquid column height and shape. The calculated results coincide well with the measured ones.4. In the first time, a coupled model of mutual inductance has been used to simulate the electromagnetic field of EMC slab. The influence of inductor shape, inductor current intensity, screening positions and power supply frequency et al on the magnetic intensity distribution has been researched. The calculated results of the semi-levitated liquid column shape under loading coincide well with the experimental results.5. To get the matching relation between casting speed and key technology parameters such as pouring temperature, column height and cooling water flow, adetail technology process has been investigated during EMC aluminum alloy. A rational cooling intensity distribution has been used based on the theory analysis, temperature field measurement as well as casting experiments. A good floating controller has been designed to solve the difficult problems of pouring and liquid level control during EMC. Pure aluminum and 3004 aluminum alloy slabs (520 X 130x900mm) as well as 2024, 5182, 6063 aluminum alloy billets ( 174X 1000mm) have been cast successfully in our domestic pilot plant.6. The technology investigation of electromagnetic casting for a double-ingot have been carried out, based on analysis of the key parameters, the double-ingot with size of 260mm was cast simultaneously.7. The surface and inner qualities of EMC slab have been investigated and compared with those of the direct casting (DC) one. The results show that the surface roughness of EMC slab reaches up to Ra 0.65 m ( 7- 8). It is also found that the macrostructure of EMC slab is composed of fine, uniform, equiaxed grains so that its tensile intensity increases by 25-27% and toughness increases by up to 20-200% than the DC slab.8. A hot top EMC subject of aluminum thin strip has been put forward in the first time according to its characteristics. Its principle lies in the control of the liquid column, which has been controlled separately. 1) On the top zone of liquid column, a hot top made of special screen and refractory material is used to confine the liquid column, solving the problems of pouri更多还原