基于选区激光熔化的拼接复合成形基础工艺研究

发布时间：2018-06-18 04:52

本文选题：选区激光熔化 + 拼接成形　；参考：《浙江工业大学》2016年硕士论文

【摘要】：选区激光熔化技术(Selective Laser Melting,SLM)是增材制造领域最具发展潜力的技术之一。该技术利用高能束激光直接作用金属粉末,成形高致密度的金属零件。该方法能成形传统加工无法制造的复杂结构,在航空航天、生物医学及复杂模具等方面有广泛应用。但目前SLM成形技术在制造精度及成本控制等存在较多问题,对某些既有高制造精度、又存在个性化复杂结构的零件,仅单一传统加工或SLM成形均存在困难。为此,本文提出在机加工零件上成形个性化复杂结构,充分结合两种加工方式的优势。首先本文制定基本工艺路线并进行预实验研究,在此基础上提出实验方案。在SLM成形仓定位中,确定机加工基体、基板和CAD零件的相互空间位置关系,设计并实现了定位方式及定位误差控制。对基体SLM成形过程进行温度场仿真,研究等能量密度输入下激光功率、扫描速度对单道成形、熔池温度效应扩散的影响;提出以优化分区大小扫描的面热流方式,减少成形区面附近粘粉,研究面能量输入对面成形的温度扩散问题。在上述仿真和分析的基础上,实验研究中通过控制等线能量密度输入,解决了单道熔池不连续和有飞溅球化颗粒、面成形时球化现象严重以及面上有细小裂纹等问题。获得了激光功率和速度匹配合适时稳定的单道熔池及平整无明显裂纹的成形表面。最后在控制激光输入和扫描速度的基础上,实现了拼接实体成形。金相组织分析结果表明,成形熔池与基体有较好的冶金结合。同时提出了通过重熔实体的方法,增加结合面处熔池数量,提高结合面金属的结合能力。维式微观硬度表明,由于后加工层对前一层有热传导作用,SLM成形顶面向下硬度逐渐降低。拉伸性能实验表明,能量输入速度对结合面拉伸极限强度有着显著影响。
[Abstract]:Selective Laser melting (SLM) is one of the most promising technologies in the field of material augmentation. The technology uses high energy beam laser to directly affect metal powder to form high density metal parts. This method can form complex structures which can not be manufactured by traditional machining, and has been widely used in aerospace, biomedicine and complex mould. However, there are many problems in SLM forming technology, such as manufacturing precision and cost control. It is difficult for some parts with high manufacturing accuracy and complex structure, only single traditional machining or SLM forming. Therefore, this paper puts forward the advantages of forming individualized complex structures on machined parts and fully combining the two kinds of machining methods. First of all, the basic technological route is established and the experimental scheme is put forward on the basis of pre-experimental research. In the positioning of SLM forming warehouse, the spatial position relationship of machined matrix, substrate and CAD parts is determined, and the positioning mode and positioning error control are designed and realized. The influence of laser power and scanning speed on single pass forming and temperature diffusion of molten pool was studied by simulating the temperature field of SLM matrix forming process, and the surface heat flux mode was proposed to optimize the scanning area size. The temperature diffusion problem of the surface energy input is studied by reducing the adhesive powder near the forming area. On the basis of the above simulation and analysis, by controlling the input of equal line energy density, the problems of single channel melting pool discontinuity and spattering particles, the serious spheroidization phenomenon and the small cracks on the surface are solved in the experimental study. A stable single-pass molten pool with a suitable laser power and velocity matching is obtained and the formed surface without obvious cracks is formed. Finally, on the basis of controlling the laser input and scanning speed, the splicing solid forming is realized. The results of metallographic analysis show that the molten pool has a good metallurgical bonding with the matrix. At the same time, the method of remelting the solid is put forward to increase the number of melting pool at the bonding surface and to improve the bonding ability of the metal on the bonding surface. The results of microhardness show that the downward hardness of the top surface of SLM is gradually decreased due to the heat conduction effect of the post-machined layer on the front layer. The tensile tests show that the energy input speed has a significant effect on the ultimate tensile strength of the bonding surface.
【学位授予单位】：浙江工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG665

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