Al-Mg铝合金双脉冲电弧增材制造技术及工艺研究

发布时间：2018-04-16 08:25

本文选题：双脉冲 + 电弧增材制造　；参考：《南京理工大学》2017年硕士论文

【摘要】：双脉冲电弧增材制造以双脉冲电弧为热源、丝材为增添材料,快速直接成型致密性、力学性能较好的金属材料复杂几何构件,可极大提高材料的利用率、缩短产品的生产周期、降低生产成本,大幅提高生产效率和制造技术的核心竞争力。本课题基于机器人双脉冲电弧增材制造工艺技术,以增材制造过程及工艺为研究对象,对Al-Mg高强铝合金成型制造构件的外观形貌、关键尺寸、气孔、显微组织、机械性能开展分析研究。首先就多层单道构件进行工艺试验研究,探究低频频率和电弧特性参数对多层单道直壁体组织及性能的影响及其规律。当仅改变低频频率时,发现双脉冲电弧消除气孔效果较直流脉冲电弧好,除根部气孔外直壁体上端气孔率低。多层单道截面组织主体由等轴晶组成,基体为α-Al,晶界处密集分布中间相Alo.56Mg0.44,分布形态呈网状结构。随着低频频率从1Hz提高到9Hz,晶粒尺寸和延伸率先减小后增大,显微硬度和抗拉强度先增大后减小,3Hz时取极值。水平拉伸试样比垂直试样的抗拉强度平均高了 8.4MPa,同时,延伸率高了约5%。随电弧特性参数的增大,电流电压波形从矩形转变为梯形再转变为三角形,且脉冲电流变化速率di/dt逐渐降低。随着脉冲电流变化速率di/dt从高到低变化,多层单道直壁体侧表面粗糙度降低,同时上表面的鱼鳞纹越来越浅。平均晶粒尺寸和实际热输入趋势呈W型变化趋势,平均显微硬度和抗拉强度呈现的M型变化趋势,而垂直拉伸件的延伸率呈持续递增趋势。进一步建立简易多层多道构件算法模型,优化改进最优焊道间距的算法,并对其进行实体成型检验,实验结果和理论结果吻合度较高。同时对不同焊道间距的堆敷构件内部气孔作分析比较,发现气孔分布位置主要位于道间和层间的交界,以及焊道底部的中央位置,且当焊道间距为最优距离时,气孔相对最少。最后采用双脉冲电弧增材制造的方法,建立三维几何模型,并进行路径规划和优化轨迹,在线设计编写机器人程序并采用相对最佳的堆敷工艺参数自动堆敷实体构件,最后检测成型尺寸,发现外壁的倾斜角度与理论值相比误差率仅为1.7%,外倒锥体壁厚的离散系数为2.288%,内十字筋壁厚的离散程度为1.898%,两者壁厚均比较均匀,故用此系统通过参数优化和路径规划可堆敷得到预期设计的高强铝合金构件。
[Abstract]:Using double pulse arc as heat source, wire as material, rapid and direct forming densification and good mechanical properties of complex geometric components of metal materials, the utilization rate of materials can be greatly improved and the production cycle of products can be shortened.Reduce production costs, significantly improve production efficiency and core competitiveness of manufacturing technology.In this paper, based on the technology of robot double pulse arc material augmentation, the appearance, key size, porosity and microstructure of Al-Mg high strength aluminum alloy forming components are studied.Mechanical properties are analyzed and studied.In this paper, the influence of low-frequency frequency and arc characteristic parameters on the structure and properties of multi-layer single-channel wall is studied.When the frequency of low frequency is changed only, it is found that the effect of double pulse arc is better than that of DC pulse arc, and the porosity at the upper end of straight wall is lower than that of DC pulse arc.The structure of the multilayer single channel section is composed of equiaxed crystals, the matrix is 伪 -Al.The mesophase Alo.56Mg0.44 is densely distributed at the grain boundary.With the increase of low frequency frequency from 1Hz to 9Hz, the grain size and elongation decrease first and then increase, and the microhardness and tensile strength increase first and then decrease to 3Hz.The tensile strength of the horizontal tensile specimen is 8.4 MPA higher than that of the vertical specimen, and the elongation of the horizontal tensile specimen is about 5% higher than that of the vertical specimen.With the increase of arc characteristic parameters, the waveform of current and voltage changes from rectangle to trapezoid and then to triangle, and the rate of variation of pulse current di/dt decreases gradually.With the change of pulse current rate (di/dt) from high to low, the surface roughness of multi-layer single straight wall decreases, and the scale grain of the upper surface becomes more and more shallow.The average grain size and the actual heat input trend are W-shaped, the average microhardness and tensile strength are M-shaped, while the elongation of vertical tensile parts is increasing continuously.A simple multi-layer multi-pass component algorithm model is further established to optimize and improve the optimal solder path spacing algorithm, and its solid forming test is carried out. The experimental results are in good agreement with the theoretical results.At the same time, it is found that the pore distribution is mainly located at the junction between the interpass and the interlayer, and the central position of the bottom of the welding pipe, and the porosity is the least when the distance is the best.Finally, using the method of double pulse arc material increasing manufacture, the 3D geometry model is set up, and the path planning and optimizing trajectory are carried out. The robot program is designed and written online, and the relative optimum stacking process parameters are adopted to automatically pile up the solid components.Finally, the shape size was detected. The error rate of the inclination angle of the outer wall was only 1.7 compared with the theoretical value, the dispersion coefficient of the wall thickness of the outer inverted cone was 2.288, the dispersion degree of the wall thickness of the inner cross reinforcement was 1.8988.The wall thickness of both sides was relatively uniform.Therefore, the expected design of high strength aluminum alloy members can be obtained by using this system through parameter optimization and path planning.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG661

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