不清根手工双面焊材料及工艺研究

本文分析了中厚板传统手工双面焊存在的诸如打底焊焊缝质量无法保证，需用碳弧气刨清根；工人劳动强度大；生产效率低；焊接质量不稳定等主要问题。为提高打底焊焊道质量，不用清根使背面得到良好的凹成形，研制了适合Ｘ形坡口的梯形体陶瓷衬垫。探讨了焊缝背面成形的主要影响因素及控制方法。     

Welding and Joining of NiTi Shape Memory Alloys: A Review

NiTi is an increasingly applied material in industrial applications. However, the difficulties faced when welding and joining is required, limits its broader use in the production of complex shaped components. The main weldability problems associated with NiTi are: strength reduction, formation of intermetallic compounds, modification of phase transformation and transformation temperatures, as well as, changes in both superelastic and shape memory effects. Additionally, NiTi is envisaged to be joined to other materials, in dissimilar joints with more complex problems depending on the other base material. Thus, intensive research in welding and its effects on the joints performance has been conducted since the early stages of NiTi. This paper presents a detailed review of welding and joining processes applied to NiTi, in similar and dissimilar combinations considering both fusion and solid-state processes. Since laser is the most studied and applied welding process, a special section is devoted to this technique.     

Microstructural and Mechanical Observations of Galvanized TRIP Steel after Friction Stir Spot Welding

Friction stir spot welding was done in transformation-induced plasticity steel sheets coated with zinc. The influence of tool rotational speed and dwell time on the microstructure and mechanical properties of lap-joints were investigated. After processing, different zones were formed in the joints. Microstructures in each zone depended on the welding conditions employed. Higher dwell time coupled with higher rotational speed promoted the deposition of a large amount of allotriomorphic ferrite beside the keyhole left by the pin. Coalesced bainite formation was stimulated by the deformation. Mechanical and chemical stabilization of the austenite occurred in different welding zones. Some zinc from the coating remained in the joint, in the stirring zone, representing a partial bonding between the steel sheets. The strength of the welds depended on a complex interaction between geometrical features, such as bonding ligament length and distance between the zinc and the keyhole left by the pin and the resultant microstructure in the stirring zone. The highest joint strength was observed for the “lowest tool rotational speed–highest dwell time” combination of welding parameters.     

TP304H与12Cr1MoV锅炉管异种钢的焊接

利用舍夫勒组织图对韶关发电厂SA2 13TP30 4H与 12Cr1MoV异种钢接头可能出现的焊接组织进行了分析 ,制订出了合理的焊接工艺 ,并对锅炉上的SA2 13TP30 4H与 12Cr1MoV钢焊口进行了施焊 ,经 17个月的运行 ,10 4个焊口未出现爆漏现象     

Materials Behavior in Laser Welding of Hardmetals to Steel

Tool manufacturing industry faces the problem of permanently joining hardmetals to steel holders with high shear strength. The mostly used welding process still is brazing. However, brazed joints have poor lifetimes, mostly when high temperatures are achieved and often break in operation. In a previous study about the ability of CO₂ and Nd:YAG lasers to weld hardmetals to steels, it was found that Nd:YAG lasers, working in continuous wave mode, could be used especially for welding hardmetals with Co content around 12%. This article discusses the materials behavior under laser radiation and analyzes the microstructural features observed.     

光点与会聚测试系统的设备需求与配置

光点测试和会聚测试是验证CPT电子枪偏转线圈性能的重要手段之一。本文提出基于合理的测试方法、有效适当的测试设备 ,建立最佳的测试系统。针对光点测试和会聚测试系统中的各种设备 ,介绍它们的应用原理及应用效果 ,从而了解在测试CPT光点质量和会聚误差过程中测试系统的设计原理及设备配置原理     

Microstructure and mechanical properties of dissimilar friction stir welding of 6061-to-7050 aluminum alloys

In this work, the microstructure and mechanical properties of friction stir welded dissimilar butt joints of 6061-to-7050 aluminum alloys were evaluated. Microstructure analysis of the cross-section of the joints revealed distinct lamellar bands and various degrees of intermixing that were correlated with tool rotational speed. Due to the distinct mechanical properties of the two alloys, microhardness measurements showed a consistent asymmetric hardness distribution profile across the weld nugget, regardless of tool rotational speed. Under monotonic tensile loading, an increase in the joint strength was observed with the increase in the tool rotational speed. Regarding fracture, the joints consistently failed on the 6061 aluminum alloy side. Furthermore, two modes of failure were observed, one through the stir zone and the other through the heat-affected zone. Inspection of the fracture surfaces suggested that inadequate material intermixing produced at low tool rotational speeds was the cause for the low mechanical strength and failure through the stir zone. On the other hand, the failure observed through the heat-affected zone at high rotational speeds was produced due to the material softening as confirmed by the microhardness measurements.     

AlN陶瓷的薄膜金属化及其与金属的焊接研究

针对AlN陶瓷在微波管中的应用特点 ,采用磁控溅射镀膜方法对AlN陶瓷进行表面金属化 ,并与无氧铜焊接 ,测试焊接体的抗拉强度并对陶瓷 金属接合界面进行了微观分析。     

Experimental Investigation of the A-TIG Welding Process of Incoloy 800H

This work attempts to investigate the influence of different flux powders in the activated-TIG welding process of the Incoloy 800H super alloy. Three different fluxes (SiO₂, ZnO, and 50% ZnO +50% SiO₂) were used and welded under the same conditions and process parameters. The oxide fluxes used were in the form of nanoparticle powders. The metallurgical characteristics and mechanical properties were analyzed, and it was found that the SiO₂ flux could increase the depth of penetration whereas a ZnO flux was detrimental to this effect. Although a SiO₂ flux increased the depth of penetration, it led to a sensitization issue in the grain boundary. The combination of the fluxes 50% ZnO +50% SiO₂ produced a moderate increase in the depth of penetration compared to ZnO flux-coated weldments, but revealed a dendritic structure in the weld region.     

Research and Progress in Laser Welding of Wrought Aluminum Alloys. I. Laser Welding Processes

With the wide application of Al alloys in automotive, aerospace and other industries, laser welding has become a critical joining technique for aluminum alloys. In this review, the research and progress in laser welding of wrought Al alloys have been critically discussed from different perspectives. The primary objective of this review is to understand the influence of welding processes on joint quality and to build up the science base of laser welding for the reliable production of Al alloy joints. Two main types of industrial lasers, carbon dioxide (CO₂) and neodymium-doped yttrium aluminum garnet (Nd:YAG), are currently applied but special attention is paid to Nd:YAG laser welding of 5000 and 6000 series alloys in the keyhole (deep penetration) mode. In this part of the review, the main laser welding processing parameters including the laser-, process-, and material-related variables and their effects on weld quality are examined. In part II of this article in this journal, the metallurgical microstructures and main defects encountered in laser welding of Al alloys such as porosity, cracking, oxide inclusions, and loss of alloying elements are discussed from the point of view of mechanism of their formation, main influencing factors, and remedy measures. In part II, the main mechanical properties such as hardness, tensile, and fatigue strength and formability are also discussed.     

不锈钢激光点焊接头组织和力学性能研究

目的 改善SUS301L–HT不锈钢激光点焊焊接性能。方法 以2 mm SUS301L–HT不锈钢为母材进行激光点焊试验,并分析焊接接头的金相组织、硬度、拉伸性能以及断口形貌等。结果 焊点表面无损坏、压痕均匀、无较大焊接变形,表面无飞溅、母材颜色无明显变化。焊核区的微观组织主要是柱状晶,柱状晶依附于未熔化母材晶粒向焊核中心生长。母材硬度最高,约为309HV;焊核中心附近区域硬度适中,约为255HV,热影响区硬度最小,不到220HV。点焊接头断裂形式多为纽扣式断裂且发生在热影响区。结论 不锈钢激光点焊整体质量较好,可用于轨道列车车体加工。     

Friction Spot Joining of aluminum AA2024/carbon-fiber reinforced poly(phenylene sulfide) composite single lap joints: Microstructure and mechanical performance

Friction Spot Joining is a promising alternative joining technology for polymer–metal hybrid structures. In this work, the feasibility of Friction Spot Joining of aluminum AA2024-T3 (bare and alclad)/carbon-fiber reinforced poly(phenylene sulfide) is reported. The process temperature and the microstructure of the joints were investigated. Lap shear tensile strength as high as 27 MPa was achieved by using aluminum bare specimens. Sand blasting was also performed as an effective mechanical surface pre-treatment on aluminum surfaces, which resulted in higher surface roughness and accordingly improved mechanical performance for the selected conditions. In addition, the alclad specimens exhibited promising mechanical performance (lap shear strength of up to 43 MPa) that justifies further investigations. Finally, the bonding and failure mechanisms of the joints are briefly discussed.     

Direct Writing of Spot and Line Bonds for Microsystem Packaging Using Transmission Laser Bonding Technique

The transmission laser bonding (TLB) technique has been developed for making both spot and line bonds for microsystem packaging applications. The formation of spot bonds is first presented, while the line bond is generated by overlapping a series of spot bonds. Spot overlapping is achieved through varying the laser scanning speed as it moves across the wafers, resulting in a wide range of laser energy density or fluence. An analytical model has been developed to understand the TLB process, especially the relationship between the energy intensity distribution and the processing parameters, including the laser scanning speed and pulse rate. Also, guided by this model, experiments have been conducted to bond Pyrex-to-Si wafers at various bonding conditions with or without overlapping. To demonstrate the reliability of the TLB technique, the strength of the resulting spot and line bonds have been evaluated by microtensile tester while the surface characteristics of the bonding pair is quantified by atomic force microscopy. The strength of bonded spots can reach a stable value of 10.5 MPa, while the bonded lines can have strength at 9.2 MPa. A bonding strength higher than 9.2 MPa should be considered to be comparable to those obtained by other major bonding processes. Finally, recommendations for future study are presented.     

T91与G102异种钢焊接接头运行前后硬度试验分析

对新焊的及运行了78000h的T91与G102（12Cr2MowVTiB）异种钢焊接接头进行了硬度试验分析。结果表明,T91／G102异种钢焊接接头（低匹配）运行前后硬度分布趋势基本一致;经长时运行后,T91管子母材区域显微硬度变化很小,而G102管子母材区显微硬度明显降低;长时运行后,T19侧的热影响区以及焊缝区的显微硬度均明显降低;长时运行后,G102热影响区出现了显微硬度的反常升高现象,具体原因还需要进行进一步研究分析。     

一种激光扫描跟踪实验装置的设计

该扫描跟踪实验装置以TMS320F240为核心,辅以外围电路,控制俯仰和方位电机,使之 协调工作,以开环和闭环相控制结合的方式完成对目标的初始引导、扫描、捕获、跟踪,获取运动目标的位置信息并完成信息的传输。实验表明,此方案的行扫描频率达到25Hz、目标捕获时间小于3s,跟踪速度达3.0°/s,且具有功耗低、体积小的特点。     

Optimization of Removal Rate and Weibull Modulus in Polishing of Ceramic Blocks Using the Fuzzy-Based Taguchi Method

This paper not only analyzed the Weibull modulus through reliability engineering but also obtained the optimal parameters with multiple performance characteristics using the fuzzy-based Taguchi method for polishing ceramic blocks. Optimization with the multiple performance characteristics is found to be the highest speed and greatest load, and diamond particle of 3 μm and 30% concentration. The analysis of variance shows that the most significant polishing parameters are load (57.75%) and speed (24.43%), followed by concentration (12.52%) and diamond particle size (5.30%). Experimental results have shown that the multiple performance characteristics can be improved effectively through this approach.     

Numerical and Experimental Analysis of Welding Deformation in Thin Plates

The use of welding to permanently join plates is common in industry due to its high efficiency. But welding creates thermal stresses, which can lead to residual stresses and physical distortion. This phenomenon directly influences the buckling stiffness of the welded structure. The welding distortion not only makes difficult the erection of the project, but also influences the final quality and cost of production. In this research, the thermo-elastic-plastic conditions were simulated by a three-dimensional (3D) finite element model (FE). Mechanical and thermal properties of the material were applied to the model, leading to eigenvalue analysis of the thermal and longitudinal stress distribution, buckling during welding and global. The research was performed on thin plates welded by butt joints and T-joints. A birth and death method depending on time was also used to model the molten pool. Since welding is a thermo-mechanical process, a coupling method was used to obtain results for nonlinear transient thermal analysis and introduce them in the structure analysis in order to investigate the buckling phenomenon. A comparison of our numerical results with those obtained from our experiments showed that the models can help predict when and where local buckling can occur. This method can also help predict the heat distribution and deformation during and after welding.     

Microstructures and Toughness of Weld Metai of Ultrafine Grained Ferritic Steel by Laser Welding

3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120-480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is lower bainite plates or polygonal ferrite containing quantities of dispersed cementite particles, mixed with a few of low carbon martensite laths or ferrite, depending on the heat input. The hardness and the tensile strength of the weld metal are higher than those of the base metal, and monotonously increase as the heat input decreases. No softened zone exists in heat affected zone (HAZ). Compared with the base metal, although the grains of laser weld are much larger, the toughness of the weld metal is higher within a large range of heat input. Furthermore, as the heat input increases, the toughness of the weld metal rises to a maximum value, at which point the percentage of lower bainite is the highest, and then drops.     

Microstructures and Toughness of Weld Metal of Ultrafine Grained Ferritic Steel by Laser Welding

3 mm thick 400 MPa grade ultrafine grained ferritic steel plates were bead-on-plate welded by CO2 laser with heat input of 120～480 J/mm. The microstructures of the weld metal mainly consist of bainite, which form is lower bainite plates or polygonal ferrite containing quantities of dispersed cementite particles, mixed with a few of low carbon martensite laths or ferrite, depending on the heat input. The hardness and the tensile strength of the weld metal are higher than those of the base metal, and monotonously increase as the heat input decreases. No softened zone exists inheat affected zone (HAZ). Compared with the base metal, although the grains of laser weld are much larger, the toughness of the weld metal is higher within a large range of heat input. Furthermore, as the heat input increases, the toughness of the weld metal rises to a maximum value, at which point the percentage of lower bainite is the highest, and then drops.