Control of weld composition when welding high strength aluminium alloy using the tandem process

Abstract

A new cost effective process for generating different weld element compositions has been examined. Utilising tandem welding technology, different series aluminium filler wires were mixed in a single weld pool with the result that the composition of the principal alloy elements, copper and magnesium were accurately controlled. Thermodynamic modelling was then used to predict an optimum weld bead composition for eliminating solidification cracking when welding Al2024. In order to validate the predicted target composition, the tandem process was used to control the composition of the weld bead. The presented results show that using this system to deposit a controlled ternary composition weld, solidification cracking was eliminated when welding highly constrained test pieces. In contrast, cracking was evident when using commercially available binary filler wires under the same conditions.     

CMT工艺对Al-Cu合金电弧增材制造气孔的影响

分析不同纯氩保护气体流量和冷金属过渡(CMT)工艺方法对Al-Cu合金电弧填丝增材制造(WAAM)气孔的影响规律。结果表明:纯氩保护气体流量和CMT工艺方法对Al-Cu合金WAAM制造过程的气孔特征均具有重要影响。提高纯氩保护气体流量有助于减少气孔;CMT-PADV工艺因其热输入低及电弧对Al-Cu合金填充丝端部表面氧化膜的高效清理而有利于减少甚至消除气孔,提高纯氩保护气体流量至25 L/min时可消除气孔。     

7N01铝合金脉冲MIG焊与直流CMT焊多次补焊试验

高速列车用7N01铝合金有较大热裂纹倾向,而补焊时该问题更突出.分别采用脉冲MIG焊和低热输入直流CMT焊对4 mm厚7N01铝合金对接接头进行1次、2次、3次补焊,分析了补焊焊接接头的宏观成形、微观组织和硬度.结果表明,脉冲MIG补焊时下塌量和熔宽均大于直流CMT补焊,脉冲MIG补焊焊道与先焊焊缝微观组织界面明显,先焊焊缝晶粒粗大且晶界发生重熔,熔合区变宽,而直流CMT补焊焊道界面不明显,焊缝微观组织晶粒细小,熔合区无明显变化;脉冲MIG焊3次补焊后软化现象较直流CMT补焊严重.采用直流CMT焊进行7N01铝合金补焊,可有效降低热裂纹倾向并缓解接头性能下降.     

复合孕育剂Ti、Zr对2519铝铜合金焊缝组织及性能的影响

采用3种焊丝对2519铝铜合金进行MIG焊,研究了孕育剂Ti、Zr对焊缝组织和性能的影响。结果表明:Ti和Zr的细化作用是相容的,当焊丝中单独添加孕育剂Ti或Zr时,焊缝几乎由粗大的柱状晶组成;焊丝中复合添加少量的孕育剂Ti和Zr时,Ti和Zr在熔池中分别形成Al3Ti和Al3Zr,促进了α(Al)非均质形核;随着焊丝中Ti和Zr含量的增加,焊缝组织逐步细化,当焊丝中Ti和Zr含量较高时,Ti和Zr还在熔池中形成大量的Al3(Ti,Zr)质点,促进α(Al)非均质形核;焊缝组织由细小均匀的等轴晶组成,显著提高了接头强度和塑性。     

Self-adjusting dynamic characteristics of pulsed MIG welding for aluminum alloys

Pulsed MIG welding is suitable for aluminum alloys welding, because spray transfer and excellent profile can be arrived during whole welding current range, and the energy of droplet can be controlled to overcome losing of alloy elements with lower melting and steam point by controlling pulse current and pulse time. Because of the special physic properties of aluminum alloys, there are different requirements for pulsed MIG welding between starting arc short circuit and drop transfer short circuit, pulse period and base period. In order to satisfy the need of aluminum alloys MIG welding, self-adjusting dynamic characteristics are designed to output different dynamic characteristics in different welding startes. The self-adjusting dynamic characteristics of pulsed MIG welding are achieved through a short circuit controller and a dynamic electronic inductor. The welding machine(AL-MIG 350) with self-adjusting dynamic characteristics has a high rate of successfully starting arc up to 96%, and the short circuit time during transfer is less than 1ms, in the mean time, the arc is stiffness, spatter is low and weld appearance is good.     

Research on CMT welding of nickel-based alloy with stainless steel

Cold Metal Transfer （CMT） welding technique is a new welding technique introduced by Fronins company. CMT welding of nickel-based alloy with stainless steel was carried out using CuSi3 filler wire in this paper. Effects of welding parameters, including welding current, welding speed, etc, on weld surface appearance were tested. Microstructure and mechanical properties of CMT weld were studied. The results shaw that the thickness of interface reaction layer of the nickel- based alloy is 14. 3 μm, which is only 4. 33% of base material. The weld is made up of two phases, α-copper and iron-based solid solution. Rupture occurs initially at the welded seam near the edge of stainless steel in shear test. The maximum shear strength of the CuSi3 welded joint is 184. 9 MPa.     

Al-Si-Mn Alloy Coating on Aluminum Substrate Using Cold Metal Transfer (CMT) Welding Technique

The cold metal transfer (CMT) process was explored as a weld overlay technique for synthesizing Al-Si-Mn alloy coating on a commercially pure Al plate. The effect of welding speed on the bead geometry, deposition rate, and the dilution were studied and the best parameter was used to synthesize the coatings. The CMT process can be used to produce thick coatings (>2.5 mm) without porosity and with low dilution levels. The Vickers hardness number of the Al substrate increased from 28 in the bulk to 57 in the coating. It is suggested that the CMT process can be an effective and energy-efficient technique for depositing thick coatings and is useful in weld repair of aluminum alloy components.     

Improving fatigue performances of structures welded using the Stressonic® (ultrasound peening) compared with the tig refusion process

A new coaxial plasma MIG welding system is developed for the purposes of improvement of weld bead, reduction of spatter and fume generation. Welding power sources of MIG and plasma, wire feeding equipment and a coaxial plasma MIG welding torch are described in detail. The metal transfer of plasma MIG welding in aluminium is observed and compared with that of pulsed MIG welding. Although one droplet per pulse is obtained by both processes, plasma MIG welding shows more smooth metal transfer than pulsed MIG welding. The result shows that spatter and fume generation are drastically reduced, and clean and good weld bead appearance is obtained by the new system.     

冷金属过渡搭接焊镁铝异种金属接头组织及性能

采用冷金属过渡（CMT）焊接工艺,以HS201铜焊丝作为焊缝填充金属对AZ3l镁合金和6061铝合金进行搭接焊接．测试了接头的抗剪强度和显微硬度,并利用光学显微镜（OM）、扫描电镜（SEM）、能谱（EDS）对接头的组织成分及断口形貌进行了分析．结果表明,当焊接电流为109A,电弧电压10．9V,送丝速度4．9mm／s,...     

Dissimilar metal joining of aluminum alloy to galvanized steel with Al-Si, Al-Cu, Al-Si-Cu and Zn-Al filler wires

Aluminum alloy sheets were lap joined to galvanized steel sheets by gas tungsten arc welding (GTAW) with Al-5% Si, Al-12% Si, Al-6% Cu, Al-10% Si-4% Cu and Zn-15% Al filler wires. Different amounts of Si, Cu and Zn were introduced into the weld through different filler wires. The effects of alloying elements on the microstructure in the weld and tensile strength of the resultant joint were investigated. It was found that the thickness of the intermetallic compound (IMC) layer decreased and the tensile strength of the joint increased with the increase of Si content in the weld. The thickness of the IMC layer could be controlled as thin as about 2 μm and the tensile strength of the dissimilar metal joint reached 136 MPa with Al-12% Si filler wire. Al-Si-Cu filler wire could result in thinner interfacial layer than Al-Cu filler wire, and fracture during tensile testing occurred in the weld for the former filler wire but through the intermetallic compound layer for the latter one. A Zn-rich phase formed in the weld made with Zn-15% Al filler wire. Moreover, the Zn-Al filler wire also generated thick interfacial layer containing a great amount of intermetallic compounds and coarse dendrites in the weld, which led to a weak joint.     

2060铝锂合金扫描填丝焊接工艺

针对铝锂合金焊后易产生气孔、抗拉强度低的缺点,提出“∞”形激光扫描填丝焊接工艺方法,以2 mm厚2060铝锂合金为研究对象开展对接焊接试验研究,探究激光扫描填丝焊接方法对铝锂合金焊接缺陷抑制作用. 借助高速相机摄像系统,探究了激光扫描填丝焊接工艺下熔池的动态演变过程,同时探究了扫描参数对焊缝气孔的影响规律及扫描填丝工艺对气孔的抑制机理. 采用曲面响应统计方法探究工艺参数对抗拉强度的影响,并给出工艺参数组合与抗拉强度的定量关系及最优参数组合,焊接接头最大抗拉强度可达382 MPa,为母材的76.4%. 结果表明,“∞”形激光扫描填丝焊接工艺下熔池流动平稳,小孔喷发强度较弱且呈现出周期性;“∞”形激光扫描填丝焊接工艺可以有效抑制焊缝气孔,提高铝锂合金焊接质量.     

基于单片机控制的Q890D钢/6061铝合金MIG焊接头组织与性能

选取TI公司开发的MSP430F149单片机为控制核心的MIG焊过程控制系统,研究焊接电流、焊接速度、焊接方向&焊枪角度和钢侧坡口角度等对Q890D钢/6061铝合金焊缝成形的影响,并在优化焊接工艺下分析焊接电流和焊接速度对Q890D钢/6061铝合金MIG焊接头界面区组织和接头力学性能的影响。结果表明:Q890D钢/6061铝合金适宜焊接方向为右焊法,适宜的焊枪角度为10°,适宜的钢侧坡口角度为45°,焊丝位置宜处于钢侧坡口中部,适宜的焊接电流和焊接速度分别为105 A和50 cm/min;不同焊接电流和焊接速度的Q890D钢/6061铝合金MIG焊接头的断裂位置都处于界面区,而MIG焊过程中界面区形成的靠近钢侧的(Fe,Cu)2Al5和靠近铝侧的(Fe,Cu)4Al13相的双层金属间化合物层结构有助于改善焊接质量。     

铝合金厚板CMT补焊工艺试验

厚板铝合金产品在焊接生产制造中易出现局部气孔和焊接热裂纹等微小缺陷. 对于重要产品需要进行修补,并且需要严格控制修补质量,降低焊接修复次数. 针对铝合金厚板焊接结构修复质量提升的需求,利用低热输入、高质量的CMT焊接技术,进行7系高强铝合金CMT补焊工艺试验,与脉冲MIG焊接工艺的焊接接头组织进行了对比. 结果表明,相对脉冲MIG焊接工艺,使用CMT工艺进行补焊的焊接温度场低,多次补焊焊接接头软化明显减弱,焊接接头组织恶化程度减弱. 结果表明,铝合金厚板采用CMT焊接工艺进行补焊接头质量更为优良.     

高速列车用厚板铝合金CMT焊接工艺

针对低热输入、高质量焊接技术的需求,研究厚板铝合金多层多道冷金属过渡技术(cold matal transter,CMT)焊接工艺和脉冲MIG焊接工艺的区别,对CMT焊接和脉冲MIG焊接进行热循环曲线测量,焊接接头拉伸、弯曲、硬度等常规力学性能试验和接头微观组织分析.结果表明,铝合金厚板焊接时相对脉冲MIG焊接方法,CMT方法焊接温度场低,焊接接头软化明显减弱,冲击韧性得到提高,厚板多层多道焊接接头组织明显改善,晶粒明显细化.试验表明CMT焊接方法可获得相对脉冲焊接更加优良的铝合金焊接接头.     

Dendritic Boundary Corrosion of AA2198 Weld Using Fiber Laser Welding with Al–Cu Filler Wire

The microstructures and corrosion behaviors of AA2198–T851 alloy and weld were analyzed under corrosive conditions.Weld was formed using an innovative fiber laser welding process with AA2319 Al–Cu filler wire. The metallurgic morphology and distribution of the chemical compositions were determined using imaging techniques such as optical micrograph, scanning electron micrograph, high-resolution transmission electron microscopy, energy-dispersive X-ray spectrometry and X-ray diffraction. Corrosion was evaluated using an immersion test and electrochemical impedance spectroscopy in 3.5% NaCl solution at room temperature. Results indicate that the parent alloy suffered from pitting corrosion during the initial 4-h immersion which was caused by the inhomogeneous distribution of its chemical components and the different intermetallics formed during the rolling process. The weld experienced dendritic boundary corrosion under the same conditions due to the addition of the Al–Cu filler and rapid solidification during laser welding, which led to the precipitates Cu enrichment along the grain boundary. When a welding joint was immersed in the solution for 5 days, a big crack was observed across the center of the weld. In comparison, there was good corrosion resistance in the heataffected zone with a compact protective film.     

焊丝成分对SiCp/6061 Al复合材料MIG焊焊缝组织及性能的影响

采用Al-Mg及Al-Si两种焊丝分别对SiCp/6061Al复合材料进行了MIG焊及脉冲MIG焊,利用光学显微镜、电子显微镜及MTS-810试验机对焊缝的组织及性能进行了分析.结果表明,采用Al-Mg焊丝焊接时,无论是MIG焊还是脉冲MIG焊,熔池中Al-SiC间的界面反应程度均较大,生成了较多的针状Al4C3,且Al4C3的尺寸较大.采用Al-Si焊丝时,MIG焊熔池中的界面反应程度显著降低,仅生成了少量尺寸较小的针状Al4C3;而采用Al-Si焊丝的脉冲MIG焊焊缝中没有发现针状Al4C3.同时,利用Al-Si焊丝可有效地防止焊缝熄弧处的宏观结晶裂纹.力学性能试验表明,采用同样焊丝时,脉冲MIG焊接头的强度及伸长率比MIG焊接头的高,而用Al-Si焊丝焊接的接头强度比用Al-Mg焊丝焊接的接头强度高.     

7A52铝合金-钢异种结构CMT熔钎焊接头组织及镀镍层的行为与影响

以ER4043铝硅焊丝为填充金属,研究了Q235钢螺柱与7A52铝合金板CMT焊接工艺,在焊接电流115~135 A,电弧电压14.5~16.5 V,焊接速度0.3 m/min条件下,焊接过程稳定,焊缝成形连续美观.结果表明,7A52铝合金侧熔合区界面为熔焊特征,铝母材发生熔合,熔合良好;钢螺柱侧熔合区为钎焊特征,界面存在反应层,由靠近钢螺柱的Fe₂Al₅层和靠近焊缝侧的FeAl₃层组成,整体反应层厚度由根趾向焊趾方向逐渐减小.焊趾部位出现富镍区,主要由Al₃Ni的共晶组织及少量Al₃Ni₂组成.与无镀镍层焊缝比较表明,镀镍层在焊接过程的行为降低了界面反应层厚度,且通过形成富镍区,降低了接头的脆性,使接头抗剪切强度提高了15%~19%,最高达到146.9 MPa,满足了高强铝合金螺柱焊接的质量要求.     

Control of weld composition when arc welding high strength aluminium alloys using multiple filler wires

Abstract

An experimental method of controlling weld composition when welding Al2024 has been explored. Utilising the tandem process and a cold wire feed unit, two and three commercially available filler wires were mixed in a single weld pool to control composition. Thermodynamic modelling was used to provide optimum weld compositions for the eradication of solidification cracking. Validation showed that by controlling the principal elements, not only was cracking eliminated, the mechanical properties of the weld could be varied. In particular, a composition was identified, which offered adequate joint strength and ductility. Exceeding this composition resulted in a corresponding increase in weld hardness at the expense of joint ductility.     

双脉冲MIG焊对2219Al-Cu合金焊缝组织及性能的影响

研究了双脉冲MIG焊工艺对2219高强铝铜合金焊缝组织及性能的影响,通过正交试验确定了适合于2219铝铜合金焊接的最佳脉冲MIG焊工艺参数。实验结果表明,采用上述工艺参数焊接,焊缝金属中得到了大量细小的等轴晶组织,柱状晶的数量明显减少,提高了焊缝金属的力学性能。     

薄板2524铝合金激光填丝焊接工艺及组织性能

2524铝合金是具有优异损伤容限的新型航空高强Al-Cu-Mg合金.采用高功率光纤激光器焊接1.6 mm厚2524铝合金,研究了填充5087焊丝情况下,激光功率、焊接速度和填丝速度对焊缝成形、热裂纹倾向和焊缝显微组织的影响,优化焊接工艺参数,考察接头静态拉伸性能.结果表明,采用填充材料后,焊缝柱状枝晶生长方向性明显减小、晶粒细化、晶界共晶增多、热裂纹倾向降低.当激光功率为2.5 kW,焊接速度为2 m/min,填丝速度为2 m/min时,可获得成形良好、无缺陷的焊缝,接头抗拉强度达到313~324 MPa,拉伸断裂于接头熔合线附近,断口处有大量韧窝,呈韧性断裂特征.