搅拌摩擦焊在中国的发展

作为新世纪连接技术的新星,搅拌摩擦焊的发明、发展和工业化对世界工业制造领域产生了巨大的推动力.介绍了搅拌摩擦焊技术及其在中国的发展状况.     

Friction stir welding of AZ31 magnesium alloy

Friction stir welding (FSW) is an new solid-phase joining technology which has more advantages over fusion welding methods in welding of aluminum and other non-ferrous metals. The effects of welding parameters on mechanical properties and microstructure during friction stir welding of AZ31 magnesium alloy were studied in this paper. Microstructures and mechanical properties of the joints were investigated by means of optical microscopy, scanning electric microscopy ( SEM ) , micro-hardness analysis, and tensile test. Experimental results show that the magnesium alloy can be successfully welded by FSW method, and the ultimate tensile strength (UTS) of FSW joint reaches up to 90 percent of base metal. The microstructures of welded joints exhibit the variation from dynamically recrystallized fine grains to greatly deformed grains. Hardness in nugget zone was found lower than the base metal but not too obvious.     

搅拌头机械载荷在搅拌摩擦焊接中的作用的数值分析

利用数值模拟技术分析搅拌头机械载荷在焊接过程中的作用,通过对比只考虑热载荷,考虑热载荷和搅拌头的下压力,综合考虑热载荷、搅拌头下压力和工作扭矩三种条件下的应力,应变和变形,结果发现,搅拌头下压力使焊后残余应力值大幅下降;搅拌头的工作扭矩是焊后残余应力、应变不对称分布的重要影响因素;并且搅拌头机械载荷使得薄板焊后残余变形的模式发生了完全相反的变化,由不考虑搅拌头载荷时的马鞍状变成了反马鞍状.     

钛合金的搅拌摩擦焊探索

通过对钛合金热物理性能分析，比较了钛合金的搅拌摩擦焊特性；针对钛合金的特点特别设计和使用了可以满足钛合金搅拌摩擦焊的搅拌头、垫板、冷却和保护装置等；并且对Ti-6Al-4V钛合金的搅拌摩擦焊焊缝和接头进行了观察分析，还对接头力学性能进行了测试，初步试验结果表明搅拌摩擦焊可以实现钛合金焊接，接头强度可以达到母材强度90％以上，但是搅拌摩擦焊工艺、参数、搅拌头还需要进一步优化，性能指标还可以进一步提高。     

Seam-Tracking for Friction Stir Welded Lap Joints

This article presents a method for automatic seam-tracking in friction stir welding (FSW) of lap joints. In this method, tracking is accomplished by weaving the FSW tool back-and-forth perpendicular to the direction of travel during welding and monitoring force and torque signals. Research demonstrates the ability of this method to automatically track weld seam positions. Additionally, tensile and S-bend test result comparisons demonstrate that weaving most likely does not reduce weld quality. Finally, benefits of this weave-based method to FSW of lap joints are discussed and methods for incorporating it into existing friction stir welding control algorithms (such as axial load control) are examined.     

一种新型零减薄搅拌摩擦焊工艺

文中成功开发了一种基于焊具轴肩零压入量的新型零减薄搅拌摩擦焊工艺,能够从根本上彻底消除常规搅拌摩擦焊中出现的焊缝减薄现象.采用这一新型工艺实施焊接,无需对被焊母材进行任何焊前焊后的增材或减材处理,即可低成本、高效率、高质量的实现铝合金的零减薄搅拌摩擦焊接.结果表明,所得零减薄接头的抗拉强度可以达到母材的97%,断后伸长率可以达到母材的100%.由于焊接中轴肩作用被显著削弱,这种焊接方法还能有效改善工件厚度方向上的焊缝微观组织和力学性能的分布均匀度.     

Establishing empirical relationships to predict grain size and tensile strength of friction stir welded AA 6061-T6 aluminium alloy joints

AA 6061-T6 aluminium alloy(Al-Mg-Si alloy) has gathered wide acceptance in the fabrication of light weight structures requiring a high specific strength and good corrosion resistance.Compared with the fusion welding processes that are routinely used for joining structural aluminium alloys,friction stir welding(FSW) process is an emerging solid state joining process in which the material welded does not melt and recast.Joint strength is influenced by the grain size and tensile strength of the weld nugget region.Hence,an attempt was made to develop empirical relationships to predict grain size and tensile strength of friction stir welded AA 6061-T6 aluminium alloy joints.The empirical relationships are developed by response surface methodology(RSM) incorporating FSW tool and process parameters.A linear regression relationship was also established between grain size and tensile strength of the weld nugget of FSW joints.     

氧化物弥散强化材料的搅拌摩擦焊分析

为了探索搅拌摩擦焊技术应用于氧化物弥散强化材料的可焊接性及其基本特点,文中对厚度为4 mm的氧化物弥散强化铜合金进行了焊接试验,并对焊接接头的宏观形貌、微观组织、显微维氏硬度进行了分析. 发现焊接接头横截面由搅拌区、热力影响区、热影响区和母材区4部分组成. 前进侧热影响区与热力影响区形成明显的分界线,后退侧则相对模糊. 搅拌区的组织为细小的等轴晶粒,出现了洋葱环和L线,热力影响区晶粒沿一定方向发生形变,热影响区组织粗化. 沿焊缝横截面的显微维氏硬度呈V形分布,其中搅拌区硬度值最低.     

搅拌摩擦焊接过程的有限元模拟

对摩擦搅拌焊接工艺进行数值仿真，建立了搅拌摩擦焊接的二维数值计算模型，通过数值手段进行焊接参数研究。并研究了焊接工艺过程中焊件材料的流动情况以及在焊接过程中材料的应力和应变情况，且与已有结果进行比较。证实了所建立模型的正确性与可靠性。     

Enhancing the weldability of CP titanium friction stir welds with elemental foils

ABSTRACT

Friction stir welding (FSW) has proven to be a viable technique for joining a wide variety of alloys. However, thick section welding of alpha and near-alpha Ti alloys has proven particularly challenging. Previous research at the Naval Research Laboratory using Ni markers in CP Ti friction stir welds indicated that elemental additions of Ni to the joint line can provide substantial benefits for improved weldability of these alloys. The current study surveys the effects of Ni and other elemental additions to CP Ti friction stir welds to determine their influence on the resultant weld microstructure, weld surface finish, and welding machine forces. These results reveal that Ni provides the most benefits for the concentrations examined, but other elements may also provide benefits at lower concentrations. The addition of these elements may improve the weldability and weld quality for FSW of CP Ti, enabling thick section welding of this and similar alloys.     

Using permanent magnets for preventing magnetic arc blow in repair of transmission gas pipelines

The activities of The Welding Institute (TWI) in Cambridge (UK) are aimed at manufacturing industry with particular attention to joining technologies and the study of surface treatments, fields of strategic research with potentially high added value. Since the first ‘cross-flow’ LASERS for processing fine materials to more recently developed welding processes, TWI has produced innovations which have found important industrial applications, in some cases creating entirely new market sectors.

One of the best known technologies patented by TWI in recent years is ‘friction stir’ welding (FSW). This technology has particularly revolutionized the welding of aluminium and has had a great influence in industrial sectors such as aerospace and automobiles. This paper describes the most recent development in the FSW process, LASER and electron beam welding technologies, the experimental results obtained and various industrial applications.     

Investigation of dissimilar metal joints with nanoparticle fillers

There is high demand for lightweight but strong materials, which has brought about hybrid structures that are made from dissimilar light materials such as aluminium alloys. Friction stir welding (FSW) can be used not only for the joining of dissimilar materials but to produce structures with enhanced properties by incorporating reinforcing fillers (e.g., SiC) into the weld. The quality of welds produced using FSW can be affected by imperfect welding process parameters or uncontrollable variables. The objective of this work was the application and verification of a high-frequency ultrasonic technique for the investigation of dissimilar metal joint quality. Four welds with different numbers of friction stir processing passes were investigated using macroscopic study, acoustic microscopy (AM), and X-ray computed tomography (CT) techniques. Image fusion of the AM and CT results are presented, and these confirm the images obtained with the acoustic microscope correlate well with the X-ray CT. Investigations demonstrate that scanning acoustic microscopy can show even the smallest voids, their position, and their size in the weld. It was shown that number and the direction of passes influence the quality of the weld considerably. The presented results prove that the macrostructural study is not sufficient to evaluate the quality of the friction stir weld.     

紫铜的搅拌摩擦焊接头性能测试与组织分析

对T2紫铜的搅拌摩擦焊技术进行了实验研究,对其基本工艺、接头组织和性能等进行了初步分析.实验结果表明,用搅拌摩擦焊方法焊接6mm厚的T2紫铜板,当焊接规范合适时,可得到成形美观、内部无缺陷、几乎不变形的平板对接接头;搅拌摩擦焊接头的抗拉强度可达母材的90%;搅拌摩擦焊接头的电阻率与母材基本相同.     

Finite element modeling of friction stir welding—thermal and thermomechanical analysis

Friction stir welding (FSW) is a relatively new welding process that may have significant advantages compared to the fusion processes as follow: joining of conventionally non-fusion weldable alloys, reduced distortion and improved mechanical properties of weldable alloys joints due to the pure solid-state joining of metals. In this paper, a three-dimensional model based on finite element analysis is used to study the thermal history and thermomechanical process in the butt-welding of aluminum alloy 6061-T6. The model incorporates the mechanical reaction of the tool and thermomechanical process of the welded material. The heat source incorporated in the model involves the friction between the material and the probe and the shoulder. In order to provide a quantitative framework for understanding the dynamics of the FSW thermomechanical process, the thermal history and the evolution of longitudinal, lateral, and through-thickness stress in the friction stirred weld are simulated numerically. The X-ray diffraction (XRD) technique is used to measure the residual stress of the welded plate, and the measured results are used to validate the efficiency of the proposed model. The relationship between the calculated residual stresses of the weld and the process parameters such as tool traverse speed is presented. It is anticipated that the model can be extended to optimize the FSW process in order to minimize the residual stress of the weld.     

高熔点材料的搅拌摩擦焊接技术

通过焊具设计、接头微观组织与性能、焊接温度场和残余应力、热源辅助的搅拌摩擦焊(FSW)几个方面,全面介绍了高熔点材料搅拌摩擦焊技术的研究现状.结果表明,合适的搅拌头材料为钨铼(W-Re)合金和多晶立方氮化硼(PCBN);采用合适的焊具设计和工艺参数,可以得到具有良好微观组织、高强度的FSW接头;在模拟搅拌摩擦焊温度场和接头残余应力时,应依据焊接过程实际进一步完善物理模型;引入辅助热源有利于高熔点材料焊缝成形并提高焊具使用寿命.     

铝合金超声搅拌复合焊接

铝合金的搅拌摩擦焊（FSW）通常在焊接区形成上高下低”浅漏斗状”的温度场,使焊缝厚度方向的组织性能差异较大．为了得到更好的焊接效果,文中提出超声搅拌复合焊思想,将超声波通过搅拌头导入焊缝纵深处,以改善焊缝组织性能．试验采用2．5mm厚的2219铝合金分别用上述两种方法进行焊接,并对焊缝的微观组织和力学性能进行了分析比较...     

高速列车铝合金车身双热源搅拌摩擦焊仿真

高速列车采用超长铝合金型材作为车身新材料。搅拌摩擦焊以固相连接原理成为高铁车身制造新工艺。针对单热源模型不足,考虑搅拌轴肩转动摩擦生热和搅拌头塑变剪切生热,建立搅拌摩擦焊双热源有限元模型。基于传统熔焊方式,实现满足搅拌焊特征的双面挤压型材接头变形设计。通过ANSYS二次开发,完成该工艺移动瞬态热交换数值仿真,获得焊接全程三维温度场分布,仿真结果与试验数据吻合良好。结果表明,该仿真模型可行．仿真结果合理,为高铁车身国产化制造工艺吸收和工艺优化提供参考。     

Friction stir welding industrialisation and research status

This paper intends to provide a perspective on the current development of the friction stir welding (FSW) technology. The industrialisation of the technology and related research were assessed by analysing patent and scientific publications databases. The literature reviews on FSW and related technologies were also collected and analysed. The work performed enabled to understand the main areas of industry/research where the FSW technology is being applied/explored and the geographical distribution of the main players in its implementation/research. The main FSW process variants, the materials already welded/processed using it, as well as the applications envisaged, were also analysed. The data collected shows that the FSW technology, originally developed for the joining of light alloys, became a research tool with interest in several fields of engineering and material science.     

Local property characterization of friction stir welded Ti-5111: Transverse orientation measurements

Friction stir welding (FSW) provides many advantages over traditional joining techniques, the most significant of which is lower cost of fabrication. Titanium alloys provide a high specific strength and increased corrosion resistance, which makes them an attractive material for use in extreme environments, such as those experienced by the next generation vehicle systems – marine, air, land or space. This research is focused on understanding the local mechanical properties and microstructure of a friction stir weld of a 12.7 mm thick plate of Ti-5111 in the direction transverse to the weld. The weld showed significant increases in strength and ductility in the stir zone. The retreating side of the weld showed reduced strength and ductility below the base property. This result, however, was found to be limited to the microscale. The understanding gained from this research should lead to future process optimizations of FSW.     

Review of research progress on aluminium–magnesium dissimilar friction stir welding

The paper critically assesses the research progress towards aluminium–magnesium dissimilar friction stir welding (FSW). First, the theoretical requirements are explored through the understanding of joining mechanism and heat generation in aluminium–magnesium FSW. Next, the observed trends in microstructural characterisation and mechanical properties are analysed. Finally, the effects of welding parameters and how it influences process variables and materials responses are discussed in detail, and several suggestions are made based on these discussions.