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玻璃和金属钎焊接头参数优化及其封接工艺研究.doc

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    • Study of Glass--to-·metal Brazed Joints Parameters Optimization and Its Sealing TechnologySupported by National Natural S cience Foundation of China (Grant No.1 0672072) & H?椤簦澹悖?Research Program Foundation of Jiangsu (Grant No.BG2006040) A Dissertation Submitted to Nanjing University of Technology in partial fulfillment of the requirements for the Academic Degree of Master of Engineering By Zhengi nulRen./GNOHZ Supervisor:Prof.Xiang LING June 2011 硕士学位论文 摘要 玻璃和金属封接技术主要应用于制造各种光电器件近年来,随着人类对新能源的开发,该技术又应用到太阳能真空集热管中。

      太阳能真空集热管是槽式太阳能热发电系统的关键部件之一,它在运行过程中,不仅要承受较大的交变载荷,而且需要保持较高的真空度,因此,对玻璃和金属的封接提出了更高要求 本文主要通过数值分析和试验对玻璃和金属钎焊接头的力学性能与封接工艺进行了研究,主要研究内容及成果如下: (1)采用有限元的方法,分析了不同孔隙率对玻璃和金属钎焊接头残余应力的影响分析结果表明,接头最大拉应力集中在钎料层,其值约为172MPa;玻璃侧切应力的最大拉应力值约为60MPa,会对接头强度产生重要影响;接头端部附近的应力梯度变化很大,会导致钎料层和基体母材的分离失效;各向最大拉应力和压应力都集中在孔隙层中的孔洞附近;各向应力的压应力和拉应力峰值随孔隙率增加而增大,但当孔隙率达到l%以后,其增加速度变得很小 (2)基于正交分析和数值模拟的方法研究了玻璃管扩口锥度,搭接长度,可伐合金环厚度和施加的压力等因素对玻璃管和可伐合金钎焊封接接头处玻璃侧残余应力的影响计算结果表明,施加的压力和可伐合金环的厚度影响最大,玻璃管扩口锥度和搭接长度的影响较小,并以此为基础优化了钎焊接头的参数:玻璃管扩口锥度为9搭接长度为lOmm;可伐合金厚度为1.2ram;施加的压力为3MPa。

      利用优化的参数设计的接头能够减小接头处玻璃和可伐合金侧的最大拉应力,有利于提高接头的抗拉强度 (3)对玻璃表面进行粗化,实现对玻璃和可伐合金表面的化学镀镍和化学镀铜,然后进行真空钎焊封接钎焊试验结果表明,玻璃表面的金属化和可伐合金表面的化学镀处理有利于提高封接的成功率;玻璃和可伐合金能够实现较为紧密的连接,但由于镀层和玻璃表面的结合力较小,使一些试件的镀层脱离玻璃基体,发生断裂 (4)利用扫描电子显微镜、X射线衍射仪等对玻璃和可伐合金钎焊接头界面的微观组织进行了分析结果发现,玻璃和钎料层的连接表现出结合力较强的咬合结构,玻璃和可伐合金基体与钎料层在钎焊过程中发生了相互溶解和扩散这些扩散反应最终使玻璃.钎料.可伐合金连接在一起,形成了玻璃和金属的钎焊接头初步探索了玻璃和金属钎焊封接的机理,为以后的研究提供一定的理论依据关键词:玻璃和金属封接:孔隙率;真空钎焊;数值模拟;残余应力;微观组织 I ABSq、RACT=皇宣==:=皇‘;==昌宣鲁===盏;===昌鲁;;;;;;盆;;;昔;===;;==;;;二;;;;二==;=;==盏警;晶==;昌;=乇;昌:;.=;;=苫;昌;;;;皇;;;;;=;;=菡;;;;=;;;盆;=;;; ABSTRACT Glass to metal sealing technology has been widely used in manufacturing a variety of optoelectronic devices.In recent years,with the development of new energy sources due to the human demand,the technology has been also applied to the solar collector vacuum tube.The solar vacuum tube is the key component of the trough solar thermal power system,it has to bear a great alternating load and maintain a high vacuum when nmning,as a result,a 11igh·quality glass-to—metal bonding joint is necessary. In this thesis,numerical analysis and experiments have been performed to study the mechanical properties and sealing process of the glass--to--metal brazed joint,the main contents and results have been summarized,as following: The finite element method has been used to analyze the effect of different porosity levels on the glass-to—metal brazed residual stress.The results indicate that the maximum tensile stress OCCurS in the filler layer and the value is about 1 72MPa;the maximum tensile shear stress value in the glass plate is about 60MPa and has a significant influence on the joint strength;but the stress gradient is very large in the joint ends,which has a great effect on interface strength and would cause the plates and filler,especially the glass plate and the filler de—bond;the maximum compressive and tensile stress components concentrate near the pores wall;the maximum stress components increase sharply in the case of the porosity level below 1%,and then gradually change relatively small. The orthogonal analysis and numerical simulation methods have been used to analyze the effect factors which include the parameter of flared glass tube taper,the length of lap joint,the thickness of the Kovar alloy and the pressure applied on the residual stresses in the glass tube of the glass—to—Kovar alloy ring brazed joint.The results indicate that the influence of the pressure and the thickness of the Kovar alloy is great,other factors impact is small,and the parameters are optimized based on these results.The parameters optimized have been used for the brazed joint:flared glass tube taper is 9。

      the length of lap joint is 10mm,the thickness of the Kovar alloy is 1.2mm and the pressure is 3MPa,and the residual stresses within the joint have been also investigated.The results show that the maximum tensile stresses in the glass and Kovar alloy were decreased,which is benefit for the increase ofjoints strength. The glass with surfaces roughened and Kovar alloy have been electroless plated、析m nickel and copper,and then the vacuum brazing process has been operated.Brazing experimental results show that the glass surface metallization and electroless plating treatment of Kovar alloy Can enhance the success rate of sealing;the glass and Kovar alloy were closely II 硕士学位论文connected,but it is easy that the electroless deposit detaches from the glass because of thesmall cohesion strength between the deposit and glass.As a result,the fracture crack Occurs insome specimen,leading to the joint separation failure. Scanning electron microscopy(SEM)and X-ray diffraction(XRD)have been applied toanalyze the microstructure of brazed joints interface.It is found that the connection of glassand filler layer shows stronger bite force structure,and the mutual dissolution and diffusionOCCur among the glass,the Kovar alloy and the filler during the brazing process.The diffusionreaction ultimately。

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