银基钎料杂质元素影响研究及其洁净度表征

发布时间：2018-04-20 18:52

本文选题：银基钎料 + 杂质元素　；参考：《机械科学研究总院》2015年博士论文

【摘要】：近年来,随着钎焊材料应用领域不断扩展和性能研究不断深入,对钎料品质的要求随之不断增加。然而,在钎料生产及后期服役过程中的共性问题“微量杂质元素”研究的系统性不够。目前微量杂质元素的研究工作已引起国内外学者的重视,逐渐开展相关的研究工作,但针对杂质元素钙、碳、硫、氧对银基钎料影响及钎料洁净度的表征方法等仍未见系统研究和报道。课题依托国家973项目“洁净钢工艺仿真与连接界面结构及性能表征研究”开展,采用光学显微镜、扫描电子显微镜、XPS和XRD等多种分析手段研究钙、碳、硫、氧在银基钎料中的存在形式及其对钎焊工艺性和钎焊性能影响作用机理,初步提出不同杂质元素对钎料及钎焊性能影响规律,界定洁净钎料,并用熵值表征了钎料洁净度。研究表明：钙元素使BAg45CuZn钎料三元共晶点E向Ag方向靠近,随其含量的增加,钎料组织中铜基及银基固溶体晶粒异常长大,而银基固溶体含量减少,层片状共晶组织增多且其片间距减小。钙主要存在于银基固溶体和铜基固溶体的相界面处,易与铜生成高硬脆性、斜方晶格的α-CaCu金属间化合物,且其较为活泼的化学性质,在氧作用下,使固溶在钎料中的钙形成CaO阻流剂阻碍钎料流动,降低其与母材的润湿性能,最终导致钎焊性能下降。硫是破坏力极强的元素,在钎料表层形成Cu2S, ZnS, Ag2S等高熔点硫化物,钎料心部显微组织形态虽未发生明显变化,但硫原子向钎料心部进行了扩散,其在银固溶体中的含量略低于铜固溶体。随着硫含量的增加,钎料断裂方式由韧性断裂演变为脆性断裂,断口处存在大量割裂基体连续性的粒状硫化物。在钎焊温度下,未熔融的硫化物增加钎料粘度,造成与母材界面张力增加,易形成未钎透缺欠,恶化钎焊性能。带有轧制油的钎料会在其表面形成一层含碳层,根据轧制道次的不同,厚度将从0.5μm变化到7gm左右。碳在钎料表面主要以游离的碳分子和ZnC8、C2CdO4形式存在。在焊接的过程中,钎料内游离碳分子和含碳化合物中部分未能及时上浮到表面而被包裹在钎料内部；部分碳分子及含碳化合物随着钎料的熔化开始上浮,最后这些颗粒物被液态钎料推到了铺展最前沿,在液态钎料周围形成一个包围圈,阻碍钎料的铺展；还有极少一部分游离的碳易与钢中的Cr、Ni、Mn、Fe等形成了一些碳化物,但结合界面处的组织比较疏松,存在孔洞,致使接头的抗拉强度降低。氧在钎料中主要以氧化物的形式存在,固溶和吸附的含量较低。随着粉状钎料氧含量的增加,粉末颗粒之间出现了一定的粘连,部分颗粒表面还出现了裂痕。利用高氏-洛仑兹方法分析发现钎料表层结构由外向内依次为自由水吸附层、碳氢有机化合物污染层、氧化物层。同时,钎料合金的固相线温度及表观活化能不断升高,而润湿性和接头强度不断下降。钎焊接头组织中的氧化夹杂物缺陷,在疲劳试验过程中易在此处形成裂纹源,致使接头强度降低。针对银基钎料,提出了“洁净”钎料的概念及钎料流动速率评价方法,在将钎焊工艺性评价规范由传统的质量-面积评价扩展为质量-面积-时间评价方面迈出了实质性一步：用工艺熵值和性能熵值两个参数定量表达钎料洁净度,揭示了同成分同组织钎料性能迥异的内在原因,初步建立了“洁净”钎料表征体系,丰富了该领域的相关内容。
[Abstract]:In recent years, with the continuous expansion of the application field of brazing materials and the deepening of the performance research, the requirements for the quality of the solder have been increasing. However, the systematicness of the study of "trace impurity elements" in the common problem in the process of the production and service of the brazing material is not enough. There is no systematic study and report on the influence of calcium, carbon, sulfur and oxygen on the influence of silver based filler metals and the cleanliness of the solder. The subject relies on the national 973 project, "the study of the process simulation of clean steel and the characterization of the connection interface structure and properties", and the use of optical microscopy and scanning electricity. The existence form of calcium, carbon, sulfur and oxygen in silver based solder and its influence mechanism on brazing process and brazing properties are studied by various analytical means such as SUBMICROSCOPE, XPS and XRD. The influence rules of different impurity elements on brazing properties and brazing properties are preliminarily proposed, clean solder is defined and the cleanliness of the filler metal is characterized by entropy value. With the increase of the content of the three element eutectic point E of the BAg45CuZn filler metal, the content of copper based and silver based solid solution in the solder is abnormal, but the content of the silver based solid solution decreases, the layer like eutectic structure increases and the interval between the pieces decreases. The calcium is mainly located at the interface of the silver based solid solution and the copper based solid solution, and is easily formed with copper. High hard brittleness, a -CaCu intermetallic compound of the inclined square lattice, and its more active chemical properties. Under the action of oxygen, the calcium forming CaO inhibitor in the solders prevents the flow of the solder, reduces its wettability with the parent material, and eventually leads to the decrease of brazing properties. Sulfur is a very strong breaking force, and forms Cu2S, ZnS, Ag2 on the surface of the solder. Although the microstructure morphology of the core of S and other high melting points is not obviously changed, the sulfur atom diffuses into the core of the brazing material, and its content in the silver solid solution is slightly lower than that of the copper solid solution. With the increase of the sulfur content, the fracture mode of the brazing material evolves from ductile fracture to brittle fracture, and there is a large number of fractured matrix continuity at the fracture surface. At the brazing temperature, the non fused sulfide increases the viscosity of the solder, resulting in an increase in the interfacial tension with the parent material, and the formation of a layer of carbon containing a layer on its surface. The thickness of the solder with rolling oil will form a layer of carbon in the surface of the rolling oil from 0.5 to 7gm. The carbon is on the surface of the solder. The free carbon molecules and ZnC8, C2CdO4 form exist mainly. During the welding process, the free carbon molecules and the parts of the carbon containing compounds in the solder are not floating to the surface in time and are wrapped in the filler metal; some carbon molecules and carbon containing compounds begin to float up with the melting of the solder, and finally these particles are pushed to the bed by liquid solder. At the forefront of the exhibition, a ring around the liquid filler metal is formed around the liquid solder, which hinders the spreading of the solder; and a few free carbon is easy to form some carbides with Cr, Ni, Mn, and Fe in the steel, but the microstructure at the interface is loose and has holes, causing the tensile strength of the joint to be reduced. Oxygen is mainly in the form of oxide in the solder. The content of solid solution and adsorption is low. With the increase of oxygen content of the powder filler metal, there are certain adhesions between the powder particles and some cracks on the surface of the particles. Using the method of the Kao's Lorentz method, it is found that the surface structure of the filler metal is from the outside to the inside of the free water adsorption layer, the hydrocarbon organic compound pollution layer and the oxide layer. At the time, the solid phase temperature and apparent activation energy of the brazing alloy are increasing, and the wettability and strength of the joint are decreasing. The defect of the oxide inclusions in the brazed joints is easy to form a crack source here in the fatigue test, which causes the joint strength to be reduced. The concept of "clean" solder and the flow of the brazing filler metal are proposed for the silver base solder. The method of rate evaluation has taken a substantial step in the evaluation of brazing technical specification from the traditional quality area evaluation to the quality area time evaluation. It quantificationally expresses the cleanliness of the solder by two parameters of entropy value and entropy value of the process, and reveals the inherent reasons for the very different performance of the same composition and the same organization. The "clean" solder characterization system enriches the relevant contents in this field.

【学位授予单位】：机械科学研究总院
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG425

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