电磁制动下复层连铸铝坯混流控制及其界面协调变形机制

Liquid level movement in mold and mixed flow of two different liquid metals are controlled by DC magnetic field and water-cooled plate, so that aluminum clad billet with different material outside and inside and with gradient layer intermediate is continuously casted. The problems of interface bonding in the composite layer are solved mainly by the inhibition of mixed flow with electromagnetic brake and optimization design of water-cooled plate under electromagnetic continuous casting. By means of the analysis of interface organization combined with the analysis of mechanical properties and residual stress of 7050/6009 clad ingot，ascertaining: 1) the influence of technological parameters under electromagnetic continuous casting on macroscopic and microscopic organization evolvement rule and organization characteristics of the interface of two alloys is identified ; 2) interfacial strength and plastic deformation characteristics of cladding materials under press working are explicated ,which provides new method to nearly final forming processing. By means of actual measurement, theoretical analysis, continuous improvement of electromagnetic crystallizer structure, optimization of continuous casting parameters and plastic deformation conditions, industrial application of clad ingot under electromagnetic continuous casting is finally put forward, which provides necessary theoretical foundation for developing aluminum clad billet continuous casting technology with independent intellectual property rights of our country, solves the bottleneck problems of bad quality and high cost of process in clad ingot aspect; the result of our study will broaden the theory of electromagnetic metallurgy and the theory of plastic deformation.

借助于直流电磁场和水冷挡板抑制铸型内液面运动和两种不同金属液的混流，连铸生产内外层材质不同、中间有梯度层的铝合金复合板坯。重点从电磁连铸过程中的电磁制动抑制混流和水冷挡板优化设计两方面着手，解决复合层的界面结合问题。通过7050/6009合金复合铸坯的界面组织性能分析，并结合轧制前后界面力学性能和残余应力分析，探明1）复层铸坯电磁连铸过程工艺参数对铸坯宏观、微观组织演变规律以及两种金属界面的组织特征；2）明确复层材料界面强度以及在压力加工过程包敷率与成型参数间关系，为该复层材料的近终形加工提供新方法。通过不断的实测、理论解析，不断改进电磁结晶器结构，优化连铸工艺参数和塑性变形条件，最终提出复层铸坯电磁连铸的工业应用，为开发出具有我国自主知识产权的铝合金复层板坯连铸技术提供必要的理论支撑，解决我国在复层铸坯方面存在质量不过关、工艺费用高的瓶颈问题；其研究结果将拓宽电磁冶金理论和塑性变形理论。

在国家自然科学基金面上基金(5137050)的资助下，借助于直流电磁场和水冷挡板抑制铸型内两种不同金属液的混流，连铸生产内外层材质不同、中间有梯度层的铝合金复合板坯。本项目涉及两项技术，分别为直流电磁场制动和水冷挡板抑制铸型内两种不同金属液的混流。.借助于电磁制动抑制混流和水冷挡板优化设计抑制铸坯液穴内两种合金液的混流，解决了3003/4004铝合金复合层的界面结合问题。成功制备出界面清晰、平直、没有氧化，Si、Mg和Mn元素在扩散层中呈梯度分布，无夹杂和孔洞等缺陷的复层铸坯；力学性能测试结果表明复层铸坯的两种合金之间形成了牢固的冶金结合。.将厚度为30mm的3003/4004复层铸坯热轧至厚度为5mm，轧制温度为510℃，再进一步将其冷轧至厚度为1mm，微观组织观察和成分分析表明复层铸坯具有良好的可轧制性，轧板界面处保持了良好的冶金结合。经热轧后复合板在不经过后续热处理的情况下90°折弯不出现裂纹，具备优良的弯曲性能。.开发了6009/7050铝合金复层铸坯直接冷却连续铸造技术。发现6009合金液在水冷挡板的冷却作用下首先形成半固态凝壳，7050合金以液态的形式与6009合金的半固态凝壳接触，并以6009合金半固态凝壳为异质形核基质形核生长形成一层初生α-Al过渡层。.将所铸6009/7050复层样品均质化处理后再经轧制至复层板，可以看出结合面区域显微硬度值仍然保持了铸态时的梯度分布，且随着样品变形量的增加6009合金和7050合金的显微硬度均增加，当样品从15mm轧制至1 mm，6009合金的平均硬度值由45 HV左右增加至约为60 HV，7050合金的平均硬度值由110 HV 左右增加至约为130HV。分析其原因，主要是轧制过程中α-Al发生局部加工硬化和弥散强化，使显微硬度增加。