硬质合金圆环与钢基体钎焊过程的数值模拟

针对硬质合金存钎焊冷却过程产生很大的热应力而导致钎焊裂纹这一问题,采用有限元分析方法对硬质合金圆环与钢基体钎焊时冷却过程中的残余应力的分布情况进行模拟,研究接头形状、钎缝厚度对焊后残余应力的大小及分布规律的影响。结果表明,钢体上开工艺槽导致焊岳残余应力增加,对接头强度不利;钎缝厚度存在一最佳值一经试验验证,计算结果与试验基本一致。     

真空钎焊金刚石界面碳化物的形貌

采用Ni-Cr、Ag-Cu-Ti和Ti-Zr-Ni-Cu等钎料分别对单晶金刚石与基体进行真空钎焊。SEM、EDS和XRD等分析结果表明,在一定的钎焊温度、时间及真空度下,金刚石与所有钎料均形成化学冶金结合,在不同钎料界面形成的碳化物的种类、数量和形貌分布却显著不同;Ni-Cr合金钎料在界面处形成片状的Cr3C2和针状Cr7C3;Ag-Cu-Ti钎料则生成不连续分布块状TiC,Ti-Zr-Ni-Cu生成的是呈鹅卵石状连续分布的TiC。     

钎料钎剂复合型绿色钎料研究进展

钎焊是制造业的关键基础技术之一,复合钎料是践行钎焊绿色化、自动化的重要手段,与传统钎料相比,复合钎料可实现钎剂定位—定温—定时—定量精准反应.综述了国内外钎料钎剂复合型钎料的分类和特点,分析了药芯钎料、药皮钎料、粉末合成钎料等的制备技术、成分设计和典型应用,指出了目前研究的不足,并对复合钎料未来的发展方向提出了建议:借...     

钎焊过程原位合成高强度银钎料

AgCuZnSn合金具备高强度、成分无害化的优势,在绿色制造中应用前景广阔,但Sn元素的加入导致的成形性能下降,限制了其使用. 为克服该不足,设计了一种使用AgCuZn/ZnCuAgSn/AgCuZn复合焊片在钎焊过程中原位合成AgCuZnSn高强钎料的方法,采用的复合钎焊片外层为AgCuZn低熔合金,内层为ZnCuAgSn合金,二者熔点接近且内层合金低于合成后钎料熔点,复合钎料的加工性优于同成分的AgCuZnSn钎料. 使用复合钎焊片进行了感应钎焊不锈钢试验. 结果表明,钎焊过程中两种合金几乎同时熔化,经瞬间保温后可充分熔合,获得高强度钎缝,采用该工艺获得的接头强度高于常规钎焊连接强度.     

玻璃与金属真空钎焊接头残余应力影响参数分析

玻璃和金属焊接接头由于设计不合理,将致使接头存在较大的焊接残余应力,会严重削弱接头强度.应用顺次耦合有限元热应力计算方法,对平板玻璃和金属在真空条件下的钎焊过程进行了数值模拟,分析了玻璃、金属、钎料厚度、钎焊压力和钎焊温度等因素对应力集中区域残余应力的影响,并观察了焊接接头拉伸断裂后的形貌特征.结果表明,金属厚度增加会增大残余应力,并且其对残余应力影响最显著;钎焊压力和钎焊温度的增加可以降低残余应力;玻璃和钎料厚度对残余应力的影响不大;焊接接头的拉伸断裂区域位于玻璃和金属焊接接头界面贴近玻璃一侧.     

钎焊中高温氧化对硬质合金的影响

研究了YG-11C硬质合金在900、950、1000℃下加热的氧化行为,并测试了在钎焊过程中受氧化的硬质合金刀头性能。结果表明,硬质合金在900℃以上加热10 min发生氧化,硬质相WC和粘结相Co被氧化成WO3和Co WO4;氧化后的硬质合金发生变形及增重,随温度升高,氧化现象更严重,变形增重更明显;高温钎焊后的硬质合金刀头表面氧化后,微观组织变得疏松多孔,硬度及耐磨性明显降低。     

高强韧CuZnNiMn纽扣钎料钎焊截齿接头组织与性能

三明治复合钎料是实现硬质合金与钢可靠钎焊连接的重要技术,复合层间及其与基体间的界面层组织形态对力学性能有着重要影响. 系统分析了不同钎焊温度、时间条件下梯度三明治复合钎料钎缝组织演变规律,分析了影响力学性能的关键因素. 试验结果表明,梯度三明治复合钎料与钢和硬质合金基体界面形成分为4个阶段：界面组织形成、长大、溶合、重排. 梯度钎料中间CuMn2层随着保温时间的延长,由初始连续状逐渐变为孤立的小岛,周围被低Mn铜固溶体包围;继续延长保温时间,CuMn2层消失,整个钎缝由铜固溶体、银固溶体和银铜共晶组成.钎缝抗剪强度在780 ℃、保温2.5 min时达到最高285 MPa,Co,Ni元素此时发生长程扩散,聚集在中间层CuMn2附近,提高了CuMn2中间层强韧性,在断口韧窝的根部分布着Co基颗粒强化相;进一步延长保温时间,Co,Ni等钎缝强韧化元素开始分散,钎缝组织粗化,强度降低.     

陶瓷/金属钎焊接头强度研究现状

陶瓷与金属钎焊是当前工程领域研究的热点,由于陶瓷与金属的热膨胀系数与弹性模量等性能不匹配,造成接头存在较大的残余应力,这已成为影响钎焊接头强度的主要因素.因此,降低接头残余应力,提高接头强度是陶瓷与金属钎焊的主要研究内容之一.分别对氧化物陶瓷、氮化物陶瓷、碳化物陶瓷、碳氮化物陶瓷与金属钎焊接头强度的研究现状进行了综述.     

钎焊金刚石膜的试验研究及机理分析

针对金刚石膜钎焊问题,采用粉末冶金法制备的Ag72-Cu28-Ti(1-5)钎料片,对金刚石膜与硬质合金进行了真空钎焊试验。在真空度<5×1012-2Pa,850℃×10min工艺条件下,实现了金刚石膜与硬质合金的钎焊连接。用扫描电镜、电子探针及X射线衍射区研究了金刚石膜与活性钎料界面,揭示了钎焊界面的形成机理。在钎焊温度下,液态Ag-Cu-Ti钎料合金中的活性成分β-Ti与金刚石膜表面的C具有较强的亲和力,通过吸附、扩散和化学反应,在金刚石膜表面出现了类金属TiC层,在以Ag-Cu共晶合金为基的钎料作用下,实现了金刚石膜与支撑体硬质合金钎焊连接。金刚石膜钎焊接头的四点弯曲强度测试表明,在文中的钎焊工艺参数下,钎料中Ti含量1％-3％时,其钎焊接头平均强度>300MPa。     

Temperature control in laser brazing of a steel/aluminium assembly using thermographic measurements

One way of making car bodies lighter is to introduce some aluminium parts in place of steel. Steel and aluminium can be joined by laser braze welding. As in other types of thermal joining, inter-metallic phases may weaken the joint. In laser braze welding, these appear as a thin layer of brittle compounds at the steel/seam interface. Their formation is related to temperature. It has been shown that, if the layer is less than 10 μm thick, the joint is not compromised [Kreimeyer M., Sepold G. Laser steel joined aluminium-Hybrid structures, Proceedings of ICALEO'02, Jacksonville, USA; 2002]. Not only can temperature gradient be calculated by numerical simulation, but it is also possible to measure the surface temperature by thermography. We show here how thermography may be used to control temperature during laser braze welding.     

硬质合金/钢钎缝中的夹杂物及其对接头力学性能的影响

以YG8硬质合金与45钢的钎焊接头为研究对象,选用BCu54ZnMnNiSn钎料钎焊。借助金相显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、MTS万能力学试验机等手段分析了钎焊接头夹杂物与力学性能的关系。结果表明钎焊接头的夹杂物有氧化物、硫化物、磷化物、硅酸盐、硼化物等。剪切断口观察到大范围的层状撕裂和局部的小韧窝,说明断裂为韧-脆混合型断裂。在裂纹发源处很容易观察到Fe-Co-O,MnO,FeS-MnS,FeP,2MnO·SiO_2等非金属夹杂物。由于非金属夹杂物的熔点、沸点较高,与钎料基体的热膨胀系数差别较大,容易成为裂纹萌发并扩展的区域,宏观表现为剪切强度降低。     

Ni元素扩散行为对硬质合金/钢钎焊接头力学性能及微观组织的影响

本文采用不同含量的Ni元素的钎料对YG15硬质合金与35CrMo钢进行了钎焊,分别研究了Ni元素含量,钎焊温度以及有无超声作用等因素对接头力学性能与微观组织的影响,研究表明钎焊温度为800°C时随钎料中含Ni元素的增加,界面处可获得连续的α-Cu固溶体层,当钎料中Ni元素含量为4.7%时,其接头剪切强度最高,为295MPa。发现钎焊温度将影响Ni元素的扩散行为,从而影响界面处贫Co区的宽度,在温度为730℃时贫Co区宽度最小,其接头剪切强度值也最高,为350MPa。施加超声可以使增加贫Co区宽度,降低共晶组织含量,并使得WC颗粒迁移进入钎缝金属。当超声时间为30s时,贫Co区宽度为17.5μm,接头剪切强度为378MPa,比无超声时接头强度提高6%。     

几种Ag基钎料钎焊NiTiNb形状记忆合金的接头组织及性能

采用AgCuInTi、AgCuTi和AgCuPd三种钎料对NiTiNb形状记忆合金进行真空钎焊,对应的钎焊温度分别为780℃、880℃和980℃,获得了冶金质量良好的接头。微观分析结果表明,三种接头的中心区域均生成了Ag基固溶体,在该固溶体区与NiTiNb母材之间生成了灰黑色扩散反应层,其中AgCuInTi和AgCuTi钎料对应接头的反应层中生成了(Cu,Ni)Ti化合物相,而AgCuPd钎料对应接头的反应层中生成了(Cu,Pd,Ni)-Ti相。测试三种钎料对应接头的室温抗拉强度,强度最高的是AgCuPd钎料对应接头,平均值达到593 MPa;其次为AgCuInTi钎料对应接头,抗拉强度为528 MPa;强度最低的是NiTiNb/AgCuTi/NiTiNb接头,平均值为459 MPa。保温时间对NiTiNb/AgCuInTi/NiTiNb接头微观组织及强度影响较小。分析接头断口发现,断裂主要发生在性能薄弱的(Cu,Ni)Ti相区或(Cu,Pd,Ni)-Ti相区。     

The effect of different crystal conditions of filler metal on vacuum brazing of TiAl alloy and 42CrMo

Ti-based filler metals made by transient solidification and normal crystallization were selected for the vacuum brazing of the TiAl alloy and 42CrMo under different processing parameters. The results show that the tensile strength of the joint of transient solidified filler metal is higher than that of normal crystallized filler metal under the same processing parameters. By the analysis of scanning electron microscope（SEM） and X-ray diffracting （XRD） , it is found that the higher strength maybe caused by the generating of TiAl , TiNi and TiCu at the interface of joint made by transient solidified filler metal.     

银基钎料铸锭微区成分及组织的变化规律

钎料铸锭成分均匀性及组织形态是钎料成形的初始条件,对钎料塑性加工性能及加工后组织有重大的影响. 通过OM,SEM和EDS等分析测试手段,研究了BAg30CuZnSn钎料铸锭的微区成分变化规律. 结果表明,BAg30CuZnSn钎料铸锭中,沿径向由外向内方向,Ag元素含量逐渐降低,Cu,Zn元素含量逐渐升高. 冒口处,由下到上,Ag元素含量逐渐降低,Cu,Zn元素含量逐渐升高. 成分的变化导致铸锭组织发生变化,从铸锭外部到中心部位,晶粒尺寸逐渐粗大,呈现出由最初的随机分布转向成簇分布. 铸锭中心位置出现Ag元素含量较高的枝晶,为银的富集相.     

钛合金与钢异种材料钎焊研究现状

钛合金与钢复合构件在航空航天领域具有广阔的应用前景,实现钛/钢复合构件工程化应用的关键是获得性能优良的钛/钢连接接头。综述了钛/钢钎焊的研究现状,系统阐述了银基钎料、钛基钎料、瞬时液相扩散焊及复合中间层工艺连接钛/钢的研究成果,并进行了总结与展望。     

Development of Ag-Cu-Zn-Sn brazing filler metals with a 10 weight-% reduction of silver and same liquidus temperature

With BrazeTec BlueBraze the manufacturers in HVACR industry have an alternative filler metal with 10 weight-% less silver but same brazing temperatures. The performance of these new alloys has been evaluated in several tests. The evaluation included wetting investigations, metallographic examinations, joint strength at different temperatures and pulsation and corrosion resistance. The results of these tests will be presented in this paper.     

Processing and mechanical properties of porous silica-bonded silicon carbide ceramics

A simple processing route for manufacturing highly porous, silica-bonded SiC ceramics with spherical pores has been developed. The strategy adopted for making porous silica-bonded SiC ceramics entails the following steps: (i) fabricating a formed body through a combination of SiC and polymer microbeads (employed as sacrificial templates) and (ii) sintering the formed body in air. SiC particles are bonded to each other by oxidation-derived SiO₂ glass. By controlling the microbead content and the sintering temperature, it was possible to adjust the porosity such that it ranged from 19 to 77%. The flexural and compressive strengths of the porous silica-bonded SiC ceramics with ≈40% porosity were ≈65 MPa and ≈200 MPa, respectively. The superior strengths were attributed to the homogeneous distribution of small (≤30 μm), spherical pores with dense struts in the porous silica-bonded SiC ceramics.     

Laser brazing of a dissimilar joint of austenitic stainless steel and pure copper

In many industries, there are applications that require the joining of stainless steel and copper components; therefore, the welding of dissimilar stainless steel/copper joints is a common process. For this investigation, the optimal brazing conditions and suitable filler metals for laser brazing of stainless steel/copper lap joints were studied. Tensile shear force increases with increases in the laser spot diameter or in the laser irradiation angle, which is associated with increased bonding width; however, as bonding width approaches 2 mm, tensile shear force reaches a saturated value due to fracturing at the HAZ of the Cu base plate. In order to obtain joints with high tensile shear strength, laser brazing was optimized by using Cu–Si-based filler metal under the following conditions: laser power, 4 kW; spot diameter, 3 mm; laser irradiation angle, 80°; irradiation position shift, 0.6 mm; brazing speed, 0.30 m/min; and filler metal feed speed, 0.30 min. Concerning filler metals, it was found that the Ni–Cu type showed relatively large tensile shear force even at high welding speeds in comparison with those of the Cu–Si, Cu, Cu–Ni, Ni–Cu and Ni types, respectively.     

铜基钎料钎焊SiC/Nb的接头组织及强度

为了连接SiC陶瓷与铌合金．用铜基钎料对SiC陶瓷与金属铌进行了钎焊,并对接头的微观组织、形成机理和高温强度进行了研究。结果表明,使用铜基钎料可以实现SiC陶瓷和铌合金的连接且在试验温度范围内。接头强度随钎焊温度升高呈上升趋势。通过扫描电子显微镜现察,钎料与SiC陶瓷钎焊接头明显分层,存在一层较厚的过渡层,性质介于金属与陶瓷之间。获得这种层状结构对缓和焊接残余应力十分有利,500℃下,三点弯曲强度试验测试达290MPa。