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激光直接成形金属零件的工艺研究
Alternative TitleResearch on Processing Characteristics during Laser Metal Deposition Shaping Technology
张凯1,2
Department先进制造技术研究室
Thesis Advisor王天然 ; 刘伟军
ClassificationTG665
Keyword激光金属沉积成形 组织性能分析 工艺实验研究 直接分层制造
Call NumberTG665/Z32/2007
Pages133页
Degree Discipline机械电子工程
Degree Name博士
2007-02-04
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract激光多层(或称三维/立体)熔覆直接快速成形技术是在80年代末期出现的快速原型技术的基础上结合同步送料激光熔覆技术所发展起来的一项先进制造技术,它利用高能激光束局部熔化金属表面形成熔池,同时将金属原材料同步送入熔池而形成与基体金属冶金结合且稀释率很低的新金属层,加工过程中采用数控系统控制工作台根据CAD模型给定的路径往复扫描,便可在沉积基板上逐线、逐层地熔覆堆积出任意形状的功能性三维金属实体零件或仅需少量精加工的近形件,其实质是计算机控制下的三维激光熔覆。它的出现给装备制造业带来了全新的技术理念。该技术融合了CAD、激光加工、材料科学、数控加工等相关领域的关键技术,以“离散+堆积”为成形理念,能够在无工模具的情况下由计算机驱动直接沉积成形金属零件,因此,在很大程度上节省了制造周期和开销。应该说,激光熔覆直接快速制造技术是快速成形技术的进一步发展,它将现有的快速成形技术推进到直接成形全密度高强度功能性金属零件的新高度,是快速成形基本原理和激光加工技术精华的集成。本文的主要工作就是研究如何利用激光直接成形技术成形高质量的金属零件,具体的研究内容如下: 1. 介绍激光熔覆直接快速成形技术的原理和特点,综合阐述国内外相关技术的研究进展,并分析和总结归纳该技术存在的问题,最后结合该技术的应用前景和研究背景,给出本学位论文的选题意义和主要研究内容。 2. 针对金属零件直接快速成形的特点,自主设计、开发了金属零件激光直接成形系统。成形系统结构完整、功能完善、可靠性高,可以加工成形全密度金属功能近形零件。系统阐述金属零件激光成形系统的各个组成模块,各组成模块系统在工控计算机的统一指令下完成协同运动,实现自动化程度较高的金属零件激光熔覆直接成形全部过程,从而制造出全密度金属功能近形零件。 3. 研究各工艺参数对成形件形状、质量和精度的影响规律,如激光功率、扫描速度、送粉速率、光斑尺寸等对单层熔覆厚度、单道熔覆宽度等成形特征的影响,以及搭接率对成形表面平整度的影响等。通过分析影响零件精度的因素和比较实验结果,确定合理的工艺参数,并由此加工成形具有一定复杂形状的金属零件。在全面的成形工艺研究的基础上,进一步研究工艺参数的变化对成形件内部凝固组织和总体机械性能的影响关系,如各工艺参数对凝固组织的生长方式、特征尺度、重熔深度以及硬度、强度、塑性等机械性能的影响,并结合快速凝固理论对这一过程中出现的现象进行解释和验证。具体的实验操作包括:利用扫描电镜分析成形试件熔覆层的显微组织特征;使用X-射线衍射仪测定熔覆层的物相分布;利用能谱仪分析熔覆层合金元素的化学成分偏析情况;使用硬度计对熔覆层的硬度分布进行测试和分析;并制备拉伸试样测试力学性能,采用扫描电镜分析断口形貌。 4. 搭建温度场测量系统,对激光直接快速成形过程的温度场变化采用热电偶进行测量,为该过程温度场的数值计算提供较为准确的边界条件;此外,还可以通过实测温度场来检验和校正数值模型的正确性与可靠性;通过监测成形过程温度场来实时反馈调整激光功率等工艺参数。
Other AbstractRapid prototyping and manufacturing bring us the novel idea of manufacturing that combines computer-aided design with laser processing technique. As one of the rapid prototyping techniques, laser metal deposition shaping becomes attractive in manufacture industry because metal parts can be manufactured directly by this method without intermediate procedures and equipment; therefore saving much time and expenses. This work addresses the problems of fabricating metal parts with desired mechanical properties by using a laser deposition technique. Such problems are considered as the less information about microstructure and mechanical properties of the deposited parts and how the laser parameters and processing conditions affect the quality of the parts. The following studies are the necessary steps required to investigate the relationship from laser parameters and processing condition to microstructure evolution and then mechanical properties. 1. The principle and characteristic of laser metal deposition shaping technology were introduced, and then the research development with the relative technologyies all around the world was expounded. After analyzing and concluding the relative problems exsiting in this technology, the significance and research content of this dissertation were put forward in the case that the application prospect and research background of this technology were combined. 2. According to the feature of laser metal depositon shaping process, the corresponding system was developed independently. This system holds integrated structure, perfect function and high reliability, and can fabricate fully-dense near-net metal parts. The components of laser metal deposition shaping system were introduced in detail, and cooperate with each other under the uniform computer command. In this way, the whole forming process can be finished with high automatization, thus fabricating the fully-dense near-net metal parts. 3. Through orthogonal experiment method, the influences of processing parameters on geometry, quality and precision of as-formed parts were investigated. For example, both the effects of laser power, scanning speed, powder feeding rate, spot diameter on clad geometry and the influences of overlapping degree on surface smoothness were addressed definitely. Through alalyzing the influence factor for precision and comparing the experimental results, the properiate processing parameters were confirmed, so the parts with specific shape were fabricated with flying colors. Based on the comprehensive processing experiments, the influences of variations in processing parameters on solidification microstructure and mechanical properties were further investigated. For instance, the effects of processing parameters on growth manner, microstructure feature, remelting depth of solidification microsopic structure and hardness, strength, plasticity of material properties were the main research goals. Combining with the rapid solidification theory, the phenomena emerging in this process were explained and verified. By virtue of alalysis equipment, detailed experimental operations were conducted. The microstructure characteristics of the as-deposited parts were analyzed by SEM; the phase distribution of clad surface was tested by X-Ray; the microsegregation of chemical composition of clad was measured by EDS; the hardness distribution of clad was detected by sclerometer; the mechanical property of as-fabricated parts was examined by tensile testing machine and the fracture feature was analyzed by SEM. 4. Through constructing the temperature testing system, the temperature distribution regularity during laser deposition process was measured by thermocouple, which provides the more accurate boundary condition for numerical simulaiton of temperature field. Moreover, the validity and reliability of numerical model can be verified and calibrated by the actual measured temperature distribution, and the processing parameters can be real-time regulated by monitoring the temperature variations.
Language中文
Contribution Rank1
Document Type学位论文
Identifierhttp://ir.sia.cn/handle/173321/110
Collection工业信息学研究室_先进制造技术研究室
Affiliation1.中国科学院沈阳自动化研究所
2.中国科学院研究生院
Recommended Citation
GB/T 7714
张凯. 激光直接成形金属零件的工艺研究[D]. 沈阳. 中国科学院沈阳自动化研究所,2007.
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