A new method for welding aluminum alloy LY12CZ sheet with high strength

0　ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｉｎｐｌａｔｅ ｓｈｅｌｌｓｔｒｕｃｔｕｒｅｓｏｆａｌｕｍｉｎｕｍａｌｌｏｙｗｉｔｈｈｉｇｈｓｔｒｅｎｇｔｈａｒｅｕｓｅｄｉｎｔｈｅｆｉｅｌｄｓｏｆａｅｒｏｎａｕｔｉｃｓａｎｄａｅｒｏｓｐａｃｅｍｏｒｅａｎｄｍｏｒｅｗｉｄｅｌｙ .Ｄｕｅｔｏｓｅｒｉｏｕｓｗｅｌｄｉｎｇｒｅｓｉｄｕａｌｓｔｒｅｓｓａｎｄｄｉｓｔｏｒｔｉｏｎ ,ｈｉｇｈｓｕｓｃｅｐｔｉｂｉｌｉｔｙｔｏｈｏｔｃｒａｃｋｉｎｇ ,ｌｏｗｓｔｒｅｎｇｔｈａｎｄｄｕｃｔｉｌｉｔｙｏｆｗｅｌｄｅｄｊｏｉｎｔ,ｔｈｅｆ…     

NUMERICAL SIMULATION OF CONTROLLING IN TITANIUM ALLOY SHEETS WELDING RESIDUAL STRESS BY TRAILING PEENING

It is a promising and new technology to apply welding with trailing peening to control welding stress and distortion of titanium alloy. Numerical simulation of conventional welding and welding with trailing peening of the titanium alloy sheet is carried out, using nonlinear finite element theory and the engineering analysis software MARC. The result shows that welding with trailing peening technology reduces longitudinal residual stress in welding joint effectively, and it is more effective to reduce residual stress to peen the weld than to peen the weld toe. It is a effective result that other technolooy and method used in welding can never achieved.     

Moiré method analysis for tensile strain field of 2024 aluminum alloy welded joint

0　IntroductionAluminumalloyswithhighstrengthhavehighratiostrengthandratiorigidity ,andhavethewideapplicationprospectsinthefieldofaviationandaerospace .Butsuchalloyshavehighsusceptibilitytohotcrack ,widesoft enedzoneandpoorqualityinweldedjoint,thusloweringthejointstrengthgreatlyandrestrainingthefurtherap plicationoftheseweldedstructures .So ,manymethodswereputforwardtostrengthenaluminumalloyweldedjointwithhighstrength .Fromtheviewpointofmetal lurgy,theexperimentalmethodsforweldingthermalsimula…     

随焊锤击对高强铝合金焊接接头应变分布的影响

采用云纹分析的试验力学方法，研究了不同情况下LYl2CZ高强铝合金焊接接头应变场的分布特点。研究结果表明，断裂前夕，常规焊接头的云纹条纹稀疏且不均匀，拉伸过程中应力集中在薄弱环节焊趾部位，焊接接头的力学性能指标较差；采用随焊锤击工艺，由于在焊接过程中同步锤击强化了焊趾部位，断裂前夕焊接接头的云纹条纹分布比较密集均匀，断裂部位由焊趾转移到焊缝，焊接接头的力学性能指标较常规焊有了较大提高，这充分说明随焊锤击技术对于实现高强铝合金焊接接头的强化是行之有效的。     

LF5铝合金焊接接头拉伸应变场的云纹法分析

采用云纹分析的实验力学方法,研究了不同条件下LF5铝合金焊接接头应变场的分布特点。实验结果表明,LF5铝合金有较好的塑性和焊接性,常规焊试样的云纹条纹分布比较均匀,仅在焊趾部位存在微量的应变集中。断裂时焊接接头的应变值较高。如果采用随焊锤击工艺,由于锤击强化的作用,对应锤击区的云纹条纹较稀,应变更多的流向了焊缝及其近缝区的母材部位,从而在一定程度上提高了焊接接头的整体延伸率。焊接接头的力学性能实验结果表明：随焊锤击是一种行之有效的强化方法。     

随焊冲击碾压减小应力变形防止热裂纹应变场分析

随焊冲击碾压法(weld with Trailing Impact Rolling，WTIR)是一种降低应力、减小变形防止热裂纹的新方法。文中分析了在前后冲击碾压轮作用下，焊缝金属塑性流动和应变场的变化规律，揭示了这种方法的机理。前轮周面内凹，迫使焊缝金属由焊趾处向焊缝中心流动，对处于脆性温度区间的焊缝金属施加一个横向挤压塑性应变，减小甚至抵消致裂的拉伸应变，防止了焊接热裂纹的产生。后轮缘稍向外凸，将焊缝金属冷却产生的压缩塑性变形充分碾开，减小了工件的应力和变形。试验结果表明，随焊冲击碾压能有效地防止焊接热裂纹的产生，将试件的纵向挠曲变形与横向收缩变形量控制到常规焊接状态的1／10和1／5左右，同时能将薄壁构件焊接残余应力控制到非常低的水平，甚至由拉应力状态转变为压应力状态，验证了应变场分析的正确性。     

随焊激冷减小铝合金薄板的焊接变形

研究了随焊激冷减小铝合金薄板焊接变形的效果及夹具的散热条件对该效果的影响,研究表明,随焊激冷能够减小铝合金薄板的焊接变形,其效果受夹具自身冷却作用影响很大。随着夹具散热条件的降低,随焊激冷所起的作用增强,但降低焊接变表的效果仍不够明显,适当预热夹具本身可以减小焊接变形,但更重要的是预热使激冷造成了温差拉伸,因此获得了最小的焊接变形。     

A new method of welding with trailing peening for controlling welding stress and distortion

In order to control welding stress and distortion, a new welding with trailing peening method based on the electromagnetic hammer was developed. This method uses the idea of constant frequency pulse width modulation for designing the control circuit of peening force and peening frequency. The peening force can be adjusted between 0 and 1 000 N and the peening frequency ranges from 0 to 25 Hz. Peening force is applied to the weld metal and the weld toe during the welding by peening head. The experiments show that the method is portable and flexible, and it can adjust the distribution state of welding residual stress, making grain refinement. When the peening force is changed to 700 N and the peening frequency to 3 Hz, both the transverse and longitudinal residual stresses will drop obviously.     

Prospects for using laser radiation to improve cracking resistance in welding cryogenic steels

It is shown that in welding large structures with stable austenitic welding materials made of nitrogen-containing cryogenic chromium–nickel–manganese austenitic steels, cracks can form in the welded joint both during crystallization and in the solid-state at subsolidus temperatures. In laser welding, the structure of the cast weld metal can be greatly refined in comparison with arc welding and this should increase the solidification cracking resistance. In addition, laser welding can be used to produce the welded joint in a single pass thus preventing reheat cracking.     

随焊旋转挤压对铝合金焊接接头组织和性能的影响

随焊旋转挤压是一种能够控制薄壁结构焊接应力和变形的新方法,这种方法同时能改善焊接接头的微观组织和力学性能.对2A12T4铝合金焊接接头的金相观察表明,随焊旋转挤压焊缝区晶粒明显细化,组织更加致密,气孔等缺陷大大减少.拉伸和三点弯曲试验结果表明,随焊旋转挤压之后焊接接头的抗拉强度、抗弯强度等力学性能得到不同程度的提高.由于薄弱的焊趾部位得到强化,部分试件的裂纹萌生部位由焊趾转移到焊缝.     

Study of the Laser-MIG Hybrid Welded Al-Mg Alloy

The technology of laser-MIG hybrid welding is hotspot in welding researched field at present.It can improve the velocity of the welding,reduce the distortion of the welding,optimize the structure of the welding joint and etc..The 5052 aluminum alloy of the 10mm thick was welded by the laser-MIG hybrid welding.The structure,the alloy elements profile and the mechanical property of the welded joint are researched by the optical microscope,SEM,sclerometer and etc..The results showed:The medium thick Al alloy was welded in high speed by the laser-MIG hybrid welding.The appearance of the welding joint is well.The weld joint and the weld interface are fine.The intenerate region in the welding joint is small.The tensile strength in welding joint has achieved 94.4% of that in base metal.     

采用固有应变法预测超薄板的焊接变形

文中以汽车制造中常用的1 mm厚的薄板为分析对象,采用热-弹-塑性有限元分析了焊缝长度对固有变形分布特征的影响,通过比较热-弹-塑性有限元法及固有应变法预测的变形结果,定量分析了焊缝长度对固有应变法预测超薄板焊接变形时计算精度的影响.结果表明,当焊缝长度达到一定临界长度时,固有应变法可适用于板厚为1 mm左右超薄板焊接接头的焊接变形预测.     

温差拉伸和随焊激冷配合使用控制焊接变形

对温差拉伸和随焊激冷配合使用控制铝合金薄板焊接变形的联合工艺进行了数值模拟和试验研究。数值分析表明 ,随焊激冷更倾向于在焊缝中心造成显著的纵向塑性拉伸 ,而温差拉伸则倾向于在近缝区造成显著的塑性拉伸。将二者配合使用 ,不仅可以靠温差拉伸将焊缝和近缝区在加热阶段形成的纵向塑性压应变控制在较低的水平 ,还可以靠随焊激冷增加冷却阶段的纵向塑性拉伸进一步抵消焊缝区已经形成的压应变。因而充分发挥二者的作用 ,有效地控制焊件的残余变形。试验研究与数值模拟得到的结论基本一致 ,随焊激冷和温差拉伸联合使用 ,可使 5 4 0mm× 3 0 0mm× 2mm的LY1 2CZ薄板焊后纵向挠曲由单独使用温差拉伸时的 2 .87mm和单独使用随焊激冷时的 4 .88mm降低到 0 .80mm的水平     

随焊超声施加方法对铝合金TIG焊缝成形影响

在铝合金TIG焊接的过程中,超声能量处理熔池可以改善焊缝成形、组织与接头力学性能.文中研究了随焊超声施加方法对铝合金TIG焊缝成形的影响,结果表明,连续施加超声会导致熔池熔体飞溅,焊缝成形不佳;间断施加超声可以有效避免熔体飞溅,焊缝成形良好.随焊超声冲击及随焊滚动超声技术均可实现间断施加超声,结果表明,尽管随焊超声冲击使熔宽变小,但是低频冲击作用对TIG焊缝成形具有副作用,会减小熔深.而采用随焊滚动超声技术,可以有效避免低频机械冲击的不利影响,焊缝熔宽变小的同时熔深也增大.     

High speed tandem TIG welding of ferritic stainless steel plate

Weld humping and undercut are the most common appearance defects in high speed welding. A high speed tandem TIG welding process was developed to suppress the formation of these appearance defects and to improve the productivity of TIG welding. In this paper, the mechanical properties and microstructure of joints obtained from tandem and single TIG welding were tested and compared. The results show that the sound weld appearance can be obtained by tandem TIG welding at the welding speed of 3 m/min for 1.5 mm thick 409L stainless steel plate. The mechanical properties of the tandem TIG welded joint are in the similar level with single TIG welded joint. The analysis of the tandem TIG welding process indicates that the assistant arc with a push angle can prevent the liquid metal flowing backward to the trailing region of weld pool and the premature solidification of thin liquid layer in the gouging region.     

高速三丝熔化极气保护焊接工艺

针对造船企业平面分段生产流水线纵骨双丝角焊接最大焊接速度小于1.0m/min的问题,研究开发了高速三丝熔化极气保护焊接新工艺,即三根焊丝分别为引导焊丝、中间焊丝和跟随焊丝纵向排列。每根焊丝各接一套送丝系统、焊接电源和保护气,构成独立的电弧-电源系统,其焊接工艺参数分别可调,以满足各种焊接要求。结果表明,当采取引导焊丝(DCEP)/中间焊丝(DCEN)/跟随焊丝(DCEP)或引导焊丝(DCEN)/中间焊丝(DCEP)/跟随焊丝(DCEN)的极性组合时,焊接过程稳定,焊缝外观表面光洁、左右对称、起渣容易、飞溅小、无气孔,满足船舶焊接的要求。通过选用合适的焊接电流、电压组合,可以使焊接速度达到1.8m/min,焊脚长度达5～8mm。此焊接新工艺可广泛用于角焊缝的高速焊接应用场合。     

铍的焊接缺陷及其控制技术研究

加填充材料焊接铍是防止铍焊缝开裂的技术措施之一,但加填充材料对铍进行高能束焊接可使焊缝形成钎接焊.介绍了铍焊接时生成的缺陷,主要有焊接裂纹、气孔、夹杂、未焊透和热影响区的晶粒长大等,全面系统地总结了铍焊接形成的各类缺陷,减轻和消除焊接缺陷的各种试验技术.在焊接参数试验的过程中,避开对焊接裂纹敏感的脉冲焊和深熔焊接工艺参数,可使铍的焊接缺陷（特别是焊接裂纹）明显地减少.     

1420铝锂合金动态低应力无变形焊接技术

针对1420铝锂合金平板对接和T形穿透焊接结构,开展了动态低应力无变形(DC-LSND,dynamically controlled low stress non-deformation)焊接技术的可行性研究;通过与常规TIG焊进行焊接应力和变形、接头组织以及拉伸性能的对比,分析了该技术实现应力和变形控制的原因.结果表明,采用动态低应力无变形焊接1420铝锂合金平板对接结构,能够有效地减小焊接应力和变形,并且对接头的拉伸性能没有影响,同时采用该技术可实现铝锂合金T形接头穿透焊的应力和变形的控制.     

AM60变形镁合金薄板激光焊接接头的组织与性能

以AM60变形镁合金薄板为研究对象，分析C02激光焊后接头的组织和性能，探讨镁合金激光焊接的工艺特点。结果表明：在合适的工艺参数下，能获得表面成型良好、变形小的焊接接头。金相观察分析发现接头中热影响区不明显，焊缝区组织致密，晶粒细小，晶界上均匀分布着脆性相（Mg17A112），但内部易产生气孔、裂纹等微观缺陷。硬度测试结果显示，焊缝硬度略高，母材和热影响区硬度相当。在本实验条件下采用C02激光焊能实现AM60镁合金的焊接，抗拉强度可达母材的94％，断口表现为混合断裂。     

New technique of in situ rolling friction stir welding

Abstract

A new technique of in situ rolling friction stir welding (IRFSW) has been developed to reduce the residual stress and distortion. It can eliminate the weld flashes and improve corrosion resistance of the FSW seam. A new kind of FSW tool consisting of rolling balls was designed to achieve IRFSW. The residual stresses across the weld were measured by ultrasonic stress measurement experimental installation. The 3·5%NaCl solution was used to corrode the surface of welded joint, and corrosion current and potential were determined by an electrochemical analyser. The results shown that the residual tensile stress was reduced, the weld flashes were eliminated, and the corrosion resistance was improved. By applying IRFSW, the reduction of distortion was ～34·4% compared with that of conventional FSW joint for aluminium plant with 3 mm in thickness and 300 mm in length.