Effect of small tool pin profiles on microstructures and mechanical properties of 6061 aluminum alloy by friction stir welding

The effect of small tool pin profiles on the microstructures and mechanical properties of 6061 aluminum alloy joints using friction stir welding （FSW） technique was investigated. Three different tool pin profiles： threaded tapered cylindrical （T1）, triangular （T2） and square （T3） were used to produce the joints. The results indicate that the weld joints are notably affected by joining with different tool pin profiles. The triangular tool pin profile produces thebest metallurgicaland mechanical weld properties compared with other tool pin profiles. Besides, the lowest tensile strength and microhardness are obtained for the joint friction stir welded with square tool pin profile. It is observed that the smaller tool pin profile and shoulder diameter lead to narrow region of heat affected zone （HAZ） and a desired level of softening. The fracture surface examination shows that the joints are also affected when welding with different types of tool pin profiles. The fracture surface shows that the triangular specimen fails with a ductile fracture mode during the tensile test, while the brittle fracture modes are observed in the joints fabricated with other tool pin profiles （T1 and T3）.

Numerical modeling of friction stir welding using the tools with polygonal pins

Friction stir welding using the tools with polygonal pins is often found to improve the mechanical strength of weld joint in comparison to the tools with circular pins. However, the impacts of pin profile on the peak temperature, tool torque and traverse force, and the resultant mechanical stresses experienced by the tool have been rarely reported in a systematic manner. An estimation of the rate of heat generation for the tools with polygonal pins is challenging due to their non-axisymmetric cross-section about the tool axis. A novel methodology is presented to analytically estimate the rate of heat generation for the tools with polygonal pins. A three-dimensional heat transfer analysis of friction stir welding is carried out using finite element method. The computed temperature field from the heat transfer model is used to estimate the torque, traverse force and the mechanical stresses experienced by regular triangular, square, pentagon and hexagon pins following the principles of solid mechanics. The computed results show that the peak temperature experienced by the tool pin increases with the number of pin sides. However, the resultant maximum shear stress experienced by the pin reduces from the triangular to hexagonal pins.

Effect of tool pin profile on microstructure and tensile properties of friction stir welded dissimilar AA 6061e AA 5086 aluminium alloy joints

Joints between two different grades of aluminium alloys are need of the hour in many light weight military structures.In this investigation,an attempt has been made to join the heat treatable(AA 6061) and non-heat treatable(AA 5086) aluminium alloys by friction stir welding(FSW)process using three different tool pin profiles like straight cylindrical,taper cylindrical and threaded cylindrical.The microstructures of various regions were observed and analyzed by means of optical and scanning electron microscope.The tensile properties and microhardness were evaluated for the welded joint.From this investigation it is founded that the use of threaded pin profile of tool contributes to better flow of materials between two alloys and the generation of defect free stir zone.It also resulted in higher hardness values of 83 HV in the stir zone and higher tensile strength of 169 MPa compared to other two profiles.The increase in hardness is attributed to the formation of fine grains and intermetallics in the stir zone,and in addition,the reduced size of weaker regions,such as TMAZ and HAZ regions,results in higher tensile properties.

Formability analysis of dissimilar tailor welded blanks welded with different tool pin profiles

An attempt has been made to study the tailor welded blanks （TWBs） made by friction stir welding （FSW） with five different tool pin profiles. The formability of welded blanks was evaluated at constant FSW process parameters. It has been found that the welded blanks with square pin profile tool produced better formability properties as compared to other tool pin profiles. It was found that the pulsating action of the square pin profile is said to be the reason for this improvement. A microstructural evaluation performed on the blanks revealed that the stir zone created by taper cylindrical and stepped cylindrical tools was less homogeneous than that of the square tool, resulting in less formability. The limiting dome height （LDH） of square pin profile tool was found to be 14 mm while those of taper cylindrical and stepped cylindrical tools are 12.5 mm and 12.4 mm, respectively.

Influence of tool pin profile and rotational speed on the formation of friction stir welding zone in AZ31 magnesium alloy

In this investigation,the effect of friction stir welding(FSW)parameters such as tool pin profiles,rotational speed and welding speed on the mechanical properties of tensile strength,hardness and impact energy of magnesium alloy AZ31 was studied.The experiments were carried out as per Taguchi parametric design concepts and an L9 orthogonal array was used to study the influence of various combinations of process parameters.Statistical optimization technique,ANOVA,was used to determine the optimum levels and to find the significance of each process parameter.The results indicate that rotational speed(RS)and transverse speed(TS)are the most significant factors,followed by tool pin profile(PF),in deciding the mechanical properties of friction stir welded magnesium alloy.In addition,mathematical models were developed to establish relationship between different process variables and mechanical properties.

Test and Evaluation of Stiffness of a Pin Turning Device for Large Marine Engine Crankshafts

In order to prevent unwanted excited vibrations and to secure better machining precision in large size heavy duty machine tools dynamic stiffness is one of the most desirable and critical properties. In the past decades, many researches on machine tool stiffness test and evaluation methodology have been made. However any methodology for a Pin Turning Device (PTD), which is a special kind of turning lathe for machining big size crankshaft pins, is rarely found among them. This study proposes a test and evaluation process of stiffness of a PTD by measuring frequency response function at the tool center point (TCP). For conformance proving for the proposed methodology, stiffness of a PTD obtained by the proposed method with impact hammer test (IHT) has been compared with that determined by FEM.

焊接参数对异种铝合金搅拌摩擦焊公差容限的影响

为了研究焊接参数对异种铝合金搅拌摩擦焊公差容限的影响,采用显微硬度测试、拉伸力学性能测试、扫描电子显微镜(SEM)等分析测试手段研究了不同焊接工艺参数下的A356与AA6061异种铝合金搅拌摩擦焊焊接头的力学性能及组织。结果表明,工件间隙从0 mm增至1 mm,焊接头抗拉强度显著下降,并产生肉眼可见的焊接缺陷;搅拌头规格保持不变,将焊接速度从120 mm/min降至80 mm/min,可促进材料流动从而提高对工件间隙的容限;搅拌针直径从4 mm增至6 mm,可提高焊接的公差容限,且材料融合程度明显提高,不再出现分层现象。

一种新型线路带电可视化补加开口销工具套装的研发与应用

介绍了一种新型线路带电可视化补加开口销工具套装的研发过程和实际应用情况。该工具套装是由一支专业的研发团队经过深入的研究和不断的试验,最终研发出来的。通过优化设计和改进工艺流程,成功地提高了开口销的可视化效果和工作效率,使工作人员在操作过程中能够更加清晰地看到开口销的位置和状态,从而避免了可能出现的错误操作,提高了电力线路的运维工作的效率和准确性。

拉西瓦水电站水轮机剪断销剪断原因分析及专用拆卸工具设计

剪断销作为水轮机导水机构的安全保护装置,在水轮机的安全、稳定运行中起着关键的作用。文章针对拉西瓦水电站近年来剪断销频繁剪断原因进行归纳分析,并通过Solidworks建模设计出专用剪断销拆卸的工具,解决剪断销拆卸困难的问题。该设计在实际应用中获得良好的效果,对水电站今后类似问题的处理具有一定的参考意义。

搅拌头受力模型及应用

针对搅拌摩擦焊实际过程,建立了搅拌针扎入阶段和稳定焊接阶段搅拌头的受力模型,通过与实测数据对比分析对模型进行了验证.由受力模型可知无论扎入阶段或稳定焊接阶段搅拌头的薄弱部位均为搅拌针根部,若设计不当易从搅拌针根部破坏.在此基础上,针对Ti-6Al-4V的搅拌摩擦焊,将模型用于指导搅拌头设计.结果表明,合理的搅拌头设计是实现钛合金搅拌摩擦焊的关键,在合适的焊接工艺参数下可以获得成形良好的焊缝.

自持式搅拌摩擦焊研究

文中综述了自持式搅拌摩擦焊的研究现状和存在的不足,主要涉及自持式搅拌摩擦焊原理、搅拌头结构、微观组织、温度场以及力学性能等几方面内容。指出了自持式搅拌摩擦焊接头的焊缝成形、温度场分布以及力学性能等特征。在此基础上提出了进一步的研究方向。

搅拌摩擦焊数值模拟过程中不同转速与热输入功率之间关系研究

建立了搅拌摩擦焊接过程的三维瞬态传热模型,用移动热源模拟搅拌头的移动。模拟和研究不同搅拌头转速下对应的温度场,通过反问题分析方法给出了搅拌摩擦焊接热源移动模型中热输入功率与转速间的函数关系,通过这一函数表达式,计算出转速为400 r/min的热输入功率,并与试验结果进行对比,误差小于5%,从而验证文中提出的热输入功率与转速间的函数关系的正确性和有效性。

高熔点材料搅拌摩擦焊用焊具的研究

钢、钛等高熔点材料的搅拌摩擦焊是目前搅拌摩擦焊技术的研究热点,但由于焊具的限制使高熔点材料搅拌摩擦焊存在较大难度。从材料选择、结构设计、磨损及破坏等方面出发,阐述了高熔点材料搅拌摩擦焊用焊具的研究进展,给出其基本设计原则和思想,指出选择合理的焊具材料和结构设计是成功实现高熔点材料搅拌摩擦焊的关键。

搅拌针几何形态对无倾角搅拌摩擦焊焊缝成形的影响及其机制分析

无倾角搅拌摩擦焊工艺是保障平面二维及空间三维复杂焊缝焊接质量的关键技术。分别采用含有光面搅拌针、光面带切台搅拌针和螺纹带切台搅拌针的焊具进行无倾角焊接试验,对比研究焊缝形貌、缺陷分布和接头性能,以期阐明搅拌针几何形态对无倾角搅拌摩擦焊焊缝的影响及其机制,从而为无倾角搅拌摩擦焊工艺的高质量应用奠定技术基础。试验结果表明,在无倾角焊接条件下,光面搅拌针容易导致焊缝根部出现孔洞缺陷,难以形成优质接头;带切台搅拌针增强了焊缝中上部材料的塑性流动,由此间接促进了焊缝根部匙孔的填充,在较低焊速下可以获得无缺陷接头;搅拌针螺纹结构直接增强了焊缝根部材料的塑性流动,因而能在更宽的参数范围内形成无缺陷接头。与光面搅拌针相比,搅拌针切台结构增大了接头软化区宽度,提高了焊缝上部的软化程度,所得无缺陷接头的抗拉强度最高可达母材的86%。对比而言,在带切台搅拌针上进一步加工螺纹能够降低焊接热软化效应,减小软化区宽度并提高焊核区硬度,接头最高强度系数由此增大到了90%。

高速列车用7N01铝合金搅拌头选择及接头性能研究

采用四种不同形式搅拌针的搅拌头对7N01铝合金进行了搅拌摩擦焊试验。结果表明:三平面搅拌针和左旋槽搅拌针可以保证焊缝在材料厚度方向上的尺寸变化均匀,有利于保证焊接接头力学性能的均匀与连续。焊缝两侧塑化金属流动状态不同,前进侧母材晶粒表现为向上运动的拉长变形,而后退侧母材晶粒在水平方向上与焊核晶粒过渡并连接。拉伸试验结果表明,接头具有较好的拉伸性能。

搅拌头形状对2024铝合金接头组织及性能的影响

采用不同形状搅拌头对4 mm厚的2024铝合金进行搅拌摩擦焊接,对不同接头的宏观形貌、金相组织、力学性能及断口形貌进行了分析.结果表明,所有搅拌头均能形成良好接头,其中三棱锥搅拌头形成接头横截面呈完整的"洋葱瓣",焊核区的晶粒尺寸最小为5~11μm;XRD分析表明,三棱锥搅拌头形成接头焊核区微晶尺寸最小;硬度在热力影响区与热影响区的交界处最小,但三棱锥搅拌头形成的焊缝在此处的硬度值比其它搅拌头的高;所有接头的抗拉强度都达到母材的80%以上,但三棱锥搅拌头形成接头的抗拉强度最高,达到了394.74 MPa,为母材的87.72%,断后伸长率为15.38%.拉伸断口形貌分析表明,所有接头断裂方式均为塑性断裂.

不同形状搅拌头异种铝合金搅拌摩擦焊接头的性能

利用圆柱螺纹和三棱柱螺纹搅拌头对2024-T3与7075-T6铝合金进行了搅拌摩擦对接焊,并对焊缝的宏观形貌、硬度以及接头的拉伸性能、断口形貌进行了分析。结果表明:搅拌头转速为1 100r·min-1和焊接速度为80mm·min-1时的焊缝中无隧道类缺陷,且三棱柱螺纹搅拌头使得两种材料融合得较好,搭配方式为AS(2024)-RS(7075)的接头抗拉强度达到了260MPa,断裂位置为2024-T3铝合金的TMAZ区;搅拌头转速为1 100r·min-1和焊接速度为120mm·min-1且搭配方式为AS(2024)-RS(7075)时,圆柱螺纹搅拌头对应焊缝的硬度最小,仅为107HV,且拉伸断口上的韧窝数量最少、深度最浅,抗拉强度也最低,为78MPa。

基于有限元搅拌头磨损机理研究

搅拌头的磨损是影响搅拌摩擦焊接(FSW)生产成本的重要内容。本文从FSW工艺设计出发,应用数值模拟技术,基于改进的Archard理论建立搅拌头磨损模型,研究了FSW过程中搅拌头的摩擦磨损规律及使用寿命。这对研究搅拌头摩擦磨损和使用寿命,降低生产成本以及推广FSW技术具有现实的研究意义和实用价值。

输电线路带电补销工具的研制

介绍了一套输电线路带电补加销子工具,通过在绝缘操作杆一侧安装补加销子专用工具,来解决输电线路销子缺失故障。经过模拟实验和实际线路作业验证,该工具可以避免停电作业,同时大大缩短了作业时间,提高了工作效率,降低了安全风险,可以在带电补加销子作业中推广应用。

搅拌摩擦焊搅拌头研究进展

搅拌摩擦焊是一种先进的绿色低成本固相连接技术,可获得较传统熔焊技术更高质量且基本无缺陷的焊接效果,因而被广泛应用于航空航天、船舶和新能源汽车等领域。搅拌头作为实现搅拌摩擦焊接的关键工具,在焊接过程中承受高温高应力作用,易发生严重磨损、断裂破坏等现象,对搅拌头寿命和焊接质量均有不利影响。鉴于搅拌头在焊接中存在的磨损和破坏等问题,本文主要关注搅拌头的两个关键部分-搅拌针和轴肩,探讨影响搅拌头寿命和焊接接头质量的因素,从搅拌头材料选择、搅拌针几何形状以及轴肩几何形状等方面进行综述,并从新型材料选择、冷却辅助装置和表面涂层等方面提出提高搅拌头寿命以实现高质量搅拌摩擦焊接的一些方法。