金属蜂窝钎焊结构焊缝质量的超声C扫描定量评价工艺

针对金属蜂窝钎焊结构超声C扫描检测工艺不规范,难以有效定量评价焊缝质量的问题,开展了超声C扫描定量评价工艺研究.建立了蜂窝钎焊结构表征模型,指出有效声束尺寸是影响检测的主要工艺参数.进行了多组工艺试验.结果表明,声束直径在蜂窝尺寸的0.7倍以下能够获得满足定量评价要求的C扫描图像,频率和扫描间距对图像质量也有一定影响.编制了定量评价软件实现了金属蜂窝钎焊结构焊缝质量的超声C扫描自动定量评价.     

TC4钛合金/304不锈钢异种材料蜂窝结构钎焊工艺

采用Ti-37.5Zr-15Cu-10Ni和Ag-28Cu两种钎料分别对TC4钛合金面板/304不锈钢蜂窝芯异种材料蜂窝结构进行了钎焊,对钎焊界面组织和蜂窝结构的力学性能进行了对比分析. 结果表明,Ti基钎料与304不锈钢蜂窝芯箔材界面润湿反应性能较差且Ti基钎料钎缝显微硬度较高,导致钎焊界面强度低,蜂窝拉伸力学性能差. Ag基钎料与304不锈钢蜂窝芯箔材和TC4面板均发生显著的界面反应,钎焊温度830 ℃,保温时间10 min时,蜂窝抗拉强度为10.35 MPa,呈蜂窝芯破坏特征. Ag基钎料蜂窝抗拉强度明显优于Ti基钎料结果,适用于TC4钛合金面板/304不锈钢蜂窝芯异种材料蜂窝钎焊.     

Rapid ultrasonic C-scan test for spot welding based on image interpolation

In this paper, ultrasonic C-scan test of spot welds for stainless steel has been studied. It is concluded that large scanning step length contributes to high testing efficiency, however, the low-resolution C-scan image generated cannot be used to assess spot welding quality reliably. Based on bicubic image interpolation, the C-scan image in low resolution with the large step length 1 000 ~xm is subdivided and reconstructed. By this means, the C-scan image resolution is greatly enhanced and testing results obtained are satisfactory, realizing rapid assessment of spot welds. The results of rapid ultrasonic C-scan test fit the actual metallographic measured value well. Mean value of normal distribution of error statistics is O. 006 67, and the standard deviation is O. 087 11. Rapid ultrasonic C-scan test based on image interpolation is of high accuracy and excellent stability.     

Effects of electromagnetic stirring on surfacing layers during submerged arc cladding

A longitudinal magnetic field was introduced to submerged arc cladding （SAC）. Electromagnetic stirring was caused by the interaction between arc plasma and external magnetic field. The grain size was refined and the average hardness was improved. On the base of a group of optimized parameters calculated by orthogonal optimization, some tests were made to study the effects of electromagnetic stirring on hardness and grain size of surfacing layers. It was confirmed that the solidification made of liquid metal could be improved by electromagnetic stirring and hardness and grain size of surfacing layers could be improved.     

Brazing of A5056 aluminium alloy with the aid of ultrasonic vibration using Ag filler metal

In order to produce a high strength brazed joint of A5056 aluminium alloy containing magnesium of about 5 mass%, the authors applied a flux-free brazing method with the aid of ultrasonic vibration to the aluminium alloy by selecting pure Ag foil as brazing filler metal and examined the effect of brazing conditions on the joint properties. The main results obtained in this study are as follows.

At a brazing temperature of 570°C, just above the eutectic point of Al–Ag binary system, application of ultrasonic vibration for 4.0 s provided the brazed joint with the maximum tensile strength and the strength decreased with the application time. When the brazing temperature was varied from 550 to 580°C and the application time of ultrasonic vibration was kept constant at 4.0 s, the joint brazed at 560°C attained the maximum tensile strength and fractured in the base metal. It was found that using a pure Ag foil as brazing filler metal successfully brazed A5056 aluminium alloy and the joint strength was equivalent to that of the base metal. Fracture of the joint was prone to occur along the (Al₃Mg₂ + Al solid solution) phase with high hardness formed at the grain boundary of the base metal. The amount of the hard (Al₃Mg₂ + Al solid solution) phase increased with the ultrasonic application time and the brazing temperature. It seemed that the increase of the hard (Al₃Mg₂ + Al solid solution) phase mainly caused the brazed joint strength to decrease.     

Weld seam recognition algorithm based on HSI space or pipeline ultrasonic flaw inspection

In order to realize automatic weld seam tracking for pipeline ultrasonic flaw inspection, an image processing algorithm based on HSI color space was presented. Since the color tones of weld seam were different from the parent metal, weld seam images were transformed to HSI color space. In the HSl colar space, the weld seam and base metal area can be apparently distinguished. By using this image processing algorithm, the edges and centerline of pipeline weld seam can be correctly extracted. An industrial application system was developed based on the image processing algorithm, and the image processing time is less than 70 ms and the accuracy of weld seam recognition is better than 2mm.     

基于超声C扫描的电触头钎焊质量评价

钎着率是判断电触头钎焊质量的重要指标.提出了一种基于超声C扫描图象的钎着率计算方法,从而实现了电触头钎焊质量的自动评价.首先使用基于相依矩阵的平均对比度度量自动选取阈值,并用其对电触头钎焊界面超声C扫描图象实施阈值分割,然后计算针着率,并按照缺陷的回波高度特征对缺陷进行分类,最后,给出了实验结果.     

Comparison of 2A12 aluminium alloy joint by ultrasonic assisted friction stir welding and friction stir welding

Ultrasonic assisted friction stir welding （UAFSW） is a recent modification of conventional friction stir welding, which adds ultrasonic energy directly into the friction stir welding area by the pin. In this study, 2A12 aluminum alloy was welded by this process and conventional, respectively. The tensile tests, microstructure and fracture surface of FSW joint and UAFSW joint were analyzed. The research results show that the surface forming texture of ultrasonic assisted friction stir welding joint, compared with conventional, is finer and more uniform, showing metallic matte color. The grains are much finer in weld nugget zone, thermo-mechanically affected zone and heat-affected zone; S-phase particles size is much smaller and distribution is more homogeneous in the matrix. The tensile strength of UAFSW joint is 94. 13% of base metal, and the elongation is 11.77%. The tensile strength of FSW joint is 83.15% of base metal, and the elongation is 8.81%. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints.     

Mechanical properties of 2024-T4 aluminium alloy joints in ultrasonic vibration enhanced friction stir welding

Ultrasonic vibration enhanced friction stir welding （UVeFSW） is a recent modification of conventional friction stir welding （FSW）, which transmits ultrasonic vibration directly into the localized area of the workpiece near and ahead of the rotating tool. In this study, a high strength aluminium alloy （2024-T4） was welded by this process and conventional FSW, respectively. Then tensile tests, microhardness tests and fracture surface analysis were performed successively on the welding samples. The tests results reveal that ultrasonic vibration can improve the tensile strength and the elongation of welded joints. The microhardness of the stir zone also increases.     

Effect of ultrasonic vibration on the friction stir weld quality of aluminium alloy

A novel variant of friction stir welding process, referred as ultrasonic vibration enhanced friction stir welding, is developed to transmit ultrasonic vibration energy directly into the localized area of the workpiece near and ahead of the rotating tool. Experiments are conducted on 6061-T4 aluminium alloy plates by this new process and the conventional friction stir welding process, respectively. The morphology and macrograph of the welds under both conditions are observed and contrasted. The experimental results show that ultrasonic vibration enhanced friction stir welding can improve the weld formation quality and increase the welding efficiency. And it just needs a smaller axial downward force. Because that the added action of ultrasonic vibration energy may enhance the localized softening extent and the plastic flow around the tool. In addition, it also improves the mechanical properties of the welded joints.     

SP700/TC4钛合金蜂窝夹层结构钎焊工艺分析

采用非晶态Ti-Zr-Cu-Ni箔带钎料对SP700/TC4钛合金蜂窝结构进行钎焊工艺研究,分析了钎焊温度和保温时间对钎焊接头组织和力学性能的影响. 结果表明,当钎焊温度在875～890 ℃之间变化时,随温度升高,钎焊接头中元素扩散更为充分,接头拉脱强度持续增长;在890 ℃下保温2～4 h不同时长进行钎焊,接头的拉脱强度先逐渐增加,在保温时间为3.5 h时达到最大值,随后逐渐降低. 获得SP700/TC4钛合金蜂窝结构的较优钎焊工艺为890 ℃/3.5 h,该工艺下钎焊接头的室温拉脱强度、三点弯曲强度、平面压缩强度、L及W方向抗剪强度分别达到14.64,224.05,11.21,4.43及3.76 MPa,破坏部位均为TC4蜂窝芯.     

铝基复合材料超声波辅助钎焊质量评价

根据铝基复合材料钎焊接头的结构特点,分析了界面的声学信号特征,并采用先进的超声成像法对接头质量进行了检测,同时获得了界面的A扫描信号、B扫描和C扫描图像.研究结果表明,结合A扫描信号、B扫描和C扫描图像的特征,能够判断缺陷类型及其位置,并通过断面金相分析进行了验证.超声成像技术能反映出铝基复合材料钎焊界面的接合状态,可检测出气孔、氧化膜夹杂和未钎透缺陷,为铝基复合材料钎焊的研究提供了有效的检测手段.     

SiCp/A356复合材料超声波辅助钎焊

利用超声波辅助钎焊的方法实现了Zn-Al合金与体积分数55%SiCp/A356复合材料的连接,并得到了由SiC陶瓷颗粒增强的复合焊缝.通过扫描电镜、能谱等方法对焊缝的微观结构进行了描述,研究了超声波作用时间对焊接接头微观组织结构及连接强度的影响规律,建立了超声波作用下复合焊缝形成过程的物理模型.当焊接温度为475℃,超声波作用时间为20 s时钎焊焊缝的平均抗剪强度值为231 MPa.由SiC陶瓷增强的复合焊缝其室温抗剪强度与无增强相颗粒的纯合金焊缝强度相比提高了50%.结果表明,焊缝中铝含量的增加及陶瓷颗粒的增强作用是导致焊缝强度提高的两个重要因素.     

清洗工艺对GH4099蜂窝夹层结构钎焊性能的影响

目的 研究激光清洗和离子轰击对GH4099蜂窝夹层结构钎焊性能的影响,优化GH4099蜂窝夹层结构焊前清洗工艺。方法 分别用400#砂纸、不同激光功率(60~200 W)、不同离子轰击时间(1~2 h)对GH4099带材表面进行了砂纸打磨、激光清洗和离子轰击试验,分析了激光清洗和离子轰击对GH4099表面形貌、O元素含量、BNi2钎料润湿性的影响,测试了不同清洗工艺下蜂窝夹层结构钎焊接头的拉伸性能。结果 随激光功率从60 W增加到100 W,GH4099表面O含量逐渐降低,表面粗糙度逐渐增大,钎料润湿面积百分比增加到83.5%,润湿性增加。当激光功率大于100 W时,表面残留网状分布的氧化物,导致钎料润湿性降低。当激光功率进一步增加到200 W时,氧化物网状分布现象减轻,润湿性随之增加,粗糙度也有所降低;随离子轰击时间从1 h增加到2 h时,带材表面氧化皮逐渐去除干净,钎料润湿性随之增加,钎料对离子轰击2 h的表面的润湿面积百分比达到91.2%,与400#砂纸打磨的相当。经离子轰击2 h、1 020 ℃-15 min钎焊获得的夹层结构等效抗拉强度为11.9 MPa。结论 与激光清洗相比,离子轰击可以同时去除蜂窝型面及附近侧壁部分的氧化皮,能更有效地改善钎料对蜂窝基体的润湿性。     

TC4钛合金蜂窝板钎焊接头组织性能分析

研究了TC4钛合金蜂窝板的钎焊工艺,试验采用Ti-Zr-Ni-Cu钎料,真空度不低于2×10-3 Pa,钎焊温度为930℃,保温时间为30 min.对焊后试件的钎焊界面组织进行超声无损检测,检测结果表明面板与蜂窝芯钎焊效果极好,未发现有脱焊、虚焊等现象.采用扫描电镜（SEM）和能谱分析（EDS）法进行了试验分析.结果表明,母材和钎料发生相互扩散渗透反应,并出现有新的析出相.该工艺下蜂窝板的界面平均拉脱强度为12.8 MPa,抗剪强度为9.01 MPa,钎焊接头属于脆性断裂.     

TiAl与Ni基合金接触反应钎焊接头界面组织及性能

以Ti为中间层实现了TiAl与Ni基合金的接触反应钎焊。采用扫描电镜和电子探针等手段对钎焊接头的界面结构及生成相进行分析,并对接头剪切强度进行测试。结果表明:当钎焊温度为960℃时,钎缝主要由Tiss和Ti2Ni组成;当钎焊温度从960℃升高到1000℃时,钎缝中生成Ti-Al及Al-Ni-Ti化合物,典型界面结构为:GH99/(Ni,Cr)ss/Ti2Ni+AlNi2Ti+TiNi/Ti3Al+Al3NiTi2/Ti3Al+Al3NiTi2/TiAl;钎焊温度继续升高,Ti3Al和Al3NiTi2变得粗大,导致接头性能下降。当钎焊温度为1000℃,保温10min时,接头剪切强度达到最大值233MPa。随钎焊温度的升高,钎缝厚度先增加后减小。     

BNi2+TiH2复合钎料钎焊C/C复合材料与GH99镍基高温合金

采用BNi2+TiH₂复合粉末钎料成功实现C/C复合材料与GH99镍基高温合金的钎焊,对焊后接头界面组织及力学性能进行了分析.结果表明,焊后接头典型界面结构为C/C复合材料/Cr₃C₂+MC+Ni(s,s)/MC+Ni(s,s)/Ni₃Si+Ni(s,s)/Cr₃C₂+MC+Ni(s,s)/GH99高温合金.钎料中加入TiH₂,可促进C/C复合材料母材的溶解,并在钎缝中部形成MC碳化物颗粒.随着TiH₂含量的增加,钎缝中部MC形态由细小弥散向大片状转变.当TiH₂含量为3%时,接头室温及800,1000℃高温抗剪强度最高,分别可达40,19及10 MPa,接头强度高于BNi2钎料钎焊接头强度,并可有效保证接头高温使用性能.     

Ag-Cu-Sn-Ti活性钎焊Gr/2024Al复合材料与TC4钛合金

采用自制的AgCuSnTi钎料对发汗材料Gr/2024Al复合材料和TC4钛合金进行钎焊,对焊后接头界面组织及力学性能进行了分析.结果表明,接头典型界面组织为Gr/2024Al/Ti₃AlC₂/Ag₂Al+Ag₃Sn+Al₂Cu+Al₅CuTi₂/Al₅CuTi₂+Ag₃Sn/TC4.钎焊时,活性元素Ti与Gr/2024Al复合材料的石墨基体发生活性反应,实现了TC4与Gr/2024Al复合材料的低温连接,保证了复合材料的力学性能及发汗功能.随钎焊温度升高及保温时间延长,钎缝组织中弥散分布的Al₅CuTi₂化合物聚集长大成块状,使接头性能下降.当钎焊温度为680℃,保温时间为10min时接头抗剪强度达到最大值17MPa,其为Gr/2024Al复合材料母材强度的70%.     

Microstructure and strength of brazed joints of TiB2 cermet to TiAl-based alloys

In this study, TiB2 cermet and TiAl-based alloy are vacuum brazed successfully by using Ag-Cu-Ti filler metal.The microstructural analyses indicate that two reaction products, Ti ( Cu, Al ) 2 and Ag bused solid solution ( Ag ( s. s ) ) , are present in the brazing seam, and the iuterface structure of the brazed joint is TiB2/TiB2 Ag ( s. s ) /Ag ( s. s ) Ti ( Cu,Al)2/Ti( Cu, Al)2/TiAl. The experimental results show that the shear strength of the brazed TiB2/TiAl joints decreases us thebrazing time increases at a definite brazing temperature. When the joint is brazed at 1 223 K for 5 min, a joint strength up to 173 MPa is achieved.     

DD3高温合金与Ti3AlC2陶瓷的真空钎焊

通过对比试验优选出了合适钎料,并进行了后续钎焊试验.在钎焊温度800~900℃,保温时间为10 min的条件下,采用Ag-Cu-Ti钎料实现了DD3镍基高温合金与Ti₃AlC₂陶瓷的真空钎焊连接.利用扫描电镜、能谱仪、XRD等对接头的界面结构进行了分析.结果表明,接头的典型界面结构为DD3/AlNi/Al₃(Ni,Cu)₅+Al(Ni,Cu)+Ag_ss/(Al,Ti)₃(Ni,Cu)₅/Al₄Cu₉+AlNi₂Ti+Ag_ss/TiAg/Ti₃AlC₂.接头的力学性能测试表明,在钎焊温度为850℃,保温时间为10 min的条件下,接头的最高抗剪强度可达135.9 MPa,断裂发生在靠近钎缝的Ti₃AlC₂陶瓷侧.降低和提高钎焊温度对接头界面组织影响不大,但接头强度有一定程度下降.