Effect of welding processes on tensile properties of AA6061 aluminium alloy joints

The present investigation is aimed at to study the effect of welding processes such as GTAW, GMAW and FSW on mechanical properties of AA6061 aluminium alloy. The preferred welding processes of these alloys are frequently gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) due to their comparatively easier applicability and better economy. In this alloy, the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often causes inferior weld mechanical properties and poor resistance to hot cracking. Friction stir welding (FSW) is a solid phase welding technique developed primarily for welding metals and alloys that heretofore had been difficult to weld using more traditional fusion techniques. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass butt welded joints. The filler metal used for joining the plates is AA4043 (Al-5Si (wt%)) grade aluminium alloy. In the present work, tensile properties, micro hardness, microstructure and fracture surface morphology of the GMAW, GTAW and FSW joints have been evaluated, and the results are compared. From this investigation, it is found that FSW joints of AA6061 aluminium alloy showed superior mechanical properties compared with GTAW and GMAW joints, and this is mainly due to the formation of very fine, equiaxed microstructure in the weld zone.     

高强钢低功率脉冲激光诱导熔化极活性气体保护电弧仰焊成形

针对5 mm厚E36高强钢板材，开展了低功率脉冲激光诱导熔化极活性气体保护电弧复合仰焊试验。研究结果表明：相比于熔化极活性气体保护电弧焊，激光诱导熔化极活性气体保护电弧复合焊接接头的焊接热输入可降低29%。复合焊接通过减小焊接熔池尺寸，可有效抑制内凹缺陷的产生，进而增大工艺参数区间。拉伸和弯曲试验表明，无内凹缺陷接头具有良好抗拉强度和弯曲载荷；有内凹缺陷接头抗拉强度与母材相当，但最大弯曲载荷显著降低。     

Mathematical models for control of weld bead penetration in the GMAW process

This paper presents the effects of welding process parameters on weld bead penetration for the gas metal arc welding (GMAW) process. Welding process parameters included wire diameter, gas flow rate, welding speed, arc current and welding voltage. The experimental results have shown that weld bead penetration increased as wire diameter, arc current and welding voltage increased, whereas an increase in welding speed was found to decrease the weld bead penetration. However, the weld bead penetration is not affected significantly by gas flow rate changes. Mathematical equations for study of the relationship between welding process parameters and weld bead penetration have also been computed by employing a standard statistical package program, SAS.     

高强钢厚板激光-GMAW复合双面同步横焊特性研究

针对30 mm厚船用高强钢10Ni5Cr Mo V对接接头横焊应用需求,开展激光-熔化极气体保护电弧(Gas metal arc welding,GMAW)复合双面同步横焊特性研究。研究结果表明,针对横焊位姿因重力、非对称坡口对熔滴、电弧的影响,利用激光对电弧的吸引和收缩作用,通过减小光-丝间距,有效地抑制了电弧侧壁燃弧,熔滴在电磁力和等离子流力的作用下,稳定过渡到熔池中,实现了熔滴过渡稳定性控制,解决了激光-GMAW复合横焊位姿电弧偏离和熔滴下落等过程控制难题与侧壁未熔合问题;厚板激光-GMAW复合双面同步横焊包括打底层和填充层焊接,其中打底层焊接是保证接头焊接质量的关键;采用激光-GMAW复合双面同步横焊新方法,4道焊接完成了30 mm厚船用高强钢10Ni5Cr Mo V横焊位姿的高强、高效连接。焊缝表面成形良好,无裂纹、未焊透和侧壁未熔合等缺陷。接头的抗拉强度高于母材,且其–50℃冲击吸收能量为57.3 J。     

钛合金薄板带热沉GTAW焊的应力场

采用数值模拟和试验相结合的方法，比较钛合金常规钨极氩弧焊(CTAW)及带热沉的钨极氩弧焊，即动态控制低应力无变形(DC-LSND，dynamically controlled low stress no-distortion)GTAW焊接过程中应力场的形态与发展历史。DC-LSND焊接过程中，热沉的急冷收缩对热沉作用部位与熔池之间已凝固但仍处于高温状态的金属产生很强的拉伸作用，使焊缝中拉伸塑性变形增大，近缝区压缩塑性变形相应减小，从而导致焊缝与近缝区不协调应变减小，残余应力降低。与常规焊最大残余拉应力位于焊缝中心不同，在所选用的焊接条件下，DC-LSND焊最大残余拉应力位于近缝区，残余应力分布形态发生改变。     

基于旁路耦合电弧的铝钢MIG熔钎焊研究

实现铝钢良好连接的关键是有效控制焊接热输入,尽量降低中间层铝铁金属间化合物的厚度,一般认为中间层金属间化合物厚度小于10μm时铝钢接头质量良好。提出旁路耦合电弧熔钎焊方法,通过调节旁路电弧电流的大小来控制焊接热输入。在优化控制系统和工艺参数的基础上采用脉冲旁路耦合电弧焊方法将铝镁合金ER5356堆焊到304不锈钢板上,获得结合良好的焊缝。对焊接接头进行扫描电镜(Scanning electron microscope,SEM)、能量色散光谱仪(Energy dispersive spectrometry,EDS)分析,结果表明:铝与不锈钢焊接接头中间层金属间化合物平均厚度约为8μm,小于10μm的临界厚度;脉冲旁路耦合电弧焊方法能够实现铝钢的连接,是一种新型低成本低热输入电弧焊方法。     

6061/A356异种铝合金脉冲MIG搭接焊*

利用直流脉冲MIG焊接技术,进行6061变形铝合金与A356铸造铝合金板材的搭接焊接,并分析接头的力学性能、微观组织及元素分布。拉伸试验结果表明,当A356铸造铝合金板在上,6061变形铝合金板在下,焊枪行走速度为10 mm/s时,搭接接头抗拉强度最高,为95 MPa。接头拉伸试样的断裂位置都位于焊缝区,断裂形式主要为混合型断裂。微观组织及元素分析结果表明,在A356铝合金一侧的部分熔融区内发生Fe和Mg元素偏聚,形成了片状Al-Fe-Si相和颗粒状Al-Fe-Mg-Si相,这两种富Fe相会削弱接头性能。在6061铝合金一侧的部分熔融区内产生了晶界液化,形成了Al-Mg-Si-Cu相+Al固溶体贫化区的液化组织,且该相周围有Fe元素偏聚。三角区是接头中最薄弱的位置,接头拉伸试样均起裂于此并最终断裂于焊缝。     

Welding polarity effects on weld spatters and bead geometry of hyperbaric dry GMAW

Welding polarity has influence on welding stability to some extent, but the specific relationship between welding polarity and weld quality has not been found, especially under the hyperbaric environment. Based on a hyperbaric dry welding experiment system, gas metal arc welding(GMAW) experiments with direct current electrode positive(DCEP) and direct current electrode negative(DCEN) operations are carried out under the ambient pressures of 0.1 MPa, 0.4 MPa, 0.7 MPa and 1.0 MPa to find the influence rule of different welding polarities on welding spatters and weld bead geometry. The effects of welding polarities on the weld bead geometry such as the reinforcement, the weld width and the penetration are discussed. The experimental results show that the welding spatters gradually grow in quantity and size for GMAW with DCEP, while GMAW with DCEN can produce fewer spatters comparatively with the increase of the ambient pressure. Compared with DCEP, the welding current and arc voltage waveforms for DCEN is more stable and the distribution of welding current probability density for DCEN is more concentrated under the hyperbaric environment. When the ambient pressure is increased from 0.1 MPa to 1.0 MPa, the effects of welding polarities on the reinforcement, the weld width and the penetration are as follows: an increase of 0.8 mm for the weld reinforcement is produced by GMAW with DCEN and 1.3 mm by GMAW with DCEP, a decrease of 7.2 mm for the weld width is produced by DCEN and 6.1 mm by DCEP; and an increase of 3.9 mm for the penetration is produced by DCEN and 1.9 mm by DCEP. The proposed research indicates that the desirable stability in the welding procedure can be achieved by GMAW with DCEN operation under the hyperbaric environment.     

高速旋转电弧传感器的数学模型

以气保护焊接系统的数学模型和HALMOY焊丝熔化模型为基础,对高速旋转电弧传感器进行数学建模。利用该数学模型模拟焊接电流、弧长和焊丝伸出长度随时间的变化规律。实际焊接试验显示,模拟焊接电流与实际焊接电流波形高度吻合,说明建立的数学模型是准确的。结果表明,高速旋转电弧焊接时,弧长的变化较焊丝伸出长度的变化更为显著。利用每个电弧旋转周期内左半周与右半周平均电流值的差,可以判断焊枪的偏差量及其方向,同时还可根据平均电流值的大小来检测角接终止点。所建立的模型对于高速旋转电弧传感系统的设计具有指导意义。     

A study on mechanical characteristics of the friction stir welded A6005-T5 extrusion

In this paper, A6005-T5 extruded aluminum alloy sheets which are used for floor, roof or wall panels of railroad vehicles were welded by the friction stir welding (FSW) and gas metal arc welding (GMAW) techniques. The mechanical characteristics including the tensile strength, micro-hardness and fatigue strength of the FSW joint were compared to those of the base metal and GMAW joints. In order to determine the relationship between the welding variables of FSW and the mechanical characteristics of the joint, the response function was derived using the least square method and the sensitivity analysis was performed. The rotational speed, welding speed and tilting angle of the welding tool were chosen as design variables. On the basis of the Plackett-Burman design table, eight different FSW experiments were done, and then the effects of design variables on the mechanical characteristics of the FSW joint were analyzed. The result showed that the welding speed has a most significant effect on the tensile and fatigue strength. In the case of the micro-hardness, the effect of the tilting angle was the biggest.     

Effect of post weld aging treatment on tensile properties of electron beam welded AA2219 aluminum alloy

Aluminum alloy 2219 (Al-6.5%Cu) is a favourite age hardenable alloy for aerospace applications because of its excellent welding characteristics. Though AA2219 has got an edge over its 6000 and 7000 series counterparts in terms of weldability, it also suffers from poor joint strength when welded. In this investigation an attempt has been made to improve the welded joint strength through post weld aging treatment. This paper presents the effect of post-weld aging treatment on tensile properties of electron beam welded AA2219 aluminum alloy. Square butt joints were fabricated using an electron beam welding (EBW) machine of 100 kV capacity. The joints were given post-weld artificial aging treatment. Tensile tests were carried out using 100 kN, electro-mechanical controlled universal testing machine. It is found that the post-weld aging treatment is beneficial for improving weld metal hardness and tensile properties. This is mainly due to the uniform distribution of CuAl₂ precipitates in the weld metal region in post-weld aged joints compared to as welded joints as evident from weld metal microstructure.     

Effect of shielding gas mixture on gas metal arc welding of HSLA steel using solid and flux-cored wires

In this work, gas metal arc welding of high strength-low alloy (HSLA) steel with solid- and flux-cored arc welding wires using different shielding gas compositions was performed. The composition of filler wire and shielding gas in gas metal arc welds of HSLA steel determines the inclusion characteristics, microstructure and mechanical properties. Thus, acceptable weld metal properties in HSLA steel using gas metal arc welding (GMAW) process could be achieved with the proper combination of filler wire and shielding gas composition.     

405/Q245R不锈钢复合板焊接工艺及接头组织与性能

分别采用钨极氩弧焊（TIG）、选用ER309L焊丝和焊条电弧焊（SMAW）、选用A302焊条两种不同工艺焊接405/Q245R不锈钢复合板的覆层和过渡层,并采用焊条电弧焊方法、选用E4315焊条焊接其基层。对复合板接头进行力学性能测试,结果表明,接头的抗拉强度接近于母材本身强度,拉伸试样断裂均发生于母材部位;对接头金相组织的观察显示,两种接头的过渡层焊缝组织均为奥氏体加少量铁素体,在过渡层焊缝/基层母材侧界面未发生明显的碳迁移现象;进一步对过渡层焊缝进行XRD测定,未发现接头焊缝中有害相的生成,说明获得接头的性能良好,焊接工艺可行,能够满足工程实际需要。     

A Comparison of Gas Metal Arc Welding with Flux-Cored Wires and Solid Wires Using Shielding Gas

In the present work, gas metal arc welding (GMAW) with flux-cored wires and solid wires using shielding gas has been adopted for welding stainless steel. Five different compositions of shielding gas are used with flux-cored wire and three with solid wire. Spatter rates, chemical compositions, tensile strength and elongation tests have been performed and are reported. The spatter rates of the sample made using flux-cored wires are less than that for the sample made using solid wire. The ultimate tensile strength and elongation are not influenced by the composition of the shielding gas.     

Optimizing pulsed current parameters to minimize corrosion rate in gas tungsten arc welded titanium alloy

The preferred process for welding titanium alloy is frequently gas tungsten arc (GTA) welding due to its comparatively easier applicability and better economy. Weld fusion zones of this alloy typically exhibit coarse columnar grains and lead to inferior mechanical and metallurgical properties. In the case of single pass GTA welding of a thinner section of this alloy, the pulsed current has been found to be beneficial primarily due to grain refinement of the weld fusion zone over the conventional continuous current process. Fusion zone grain refinement is controlled by pulsed current parameters such as peak current, back ground current, pulse frequency and pulse-on-time. In this investigation, a mathematical model has been developed to predict corrosion rate of gas tungsten arc welded titanium alloy by incorporating pulsed current parameters. Four factors, five level, central composite, rotatable design matrix has been used to minimize the experimental conditions. A mathematical model has been developed by response surface method (RSM). The developed model has been optimized using genetic algorithm (GA) and contour plots to attain minimum corrosion rate in the weld fusion zone.     

2219铝合金双轴肩搅拌摩擦焊工艺及接头组织性能研究

通过对8mm厚2219铝合金进行双轴肩搅拌摩擦焊试验,研究了不同焊接速度对接头成形、组织演变及其对力学性能的影响规律。工艺试验结果表明:在固定转速(200r/min)下,不同焊接速度下的接头均成形良好,未出现微裂纹、隧道以及疏松等焊缝表面缺陷。随着焊接速度的增加,接头区域晶粒尺寸减小;接头显微硬度受到晶粒尺寸与沉淀相分布的制约,硬度分布曲线呈“W”形,热影响区硬度最低。并且随着焊接速度的增加,接头最低硬度和抗拉强度逐渐提高,断裂位置发生在热影响区与热影响区交界处。在焊接速度为350mm/min时,接头抗拉强度达到最大值335MPa,约为母材的72.8%。     

固溶处理对7B04-O铝合金搅拌摩擦焊接接头微观组织与力学性能的影响

对航空用3 mm厚的带有包铝层的7B04-O铝合金板材进行搅拌摩擦焊接(Friction stir welding,FSW),研究固溶处理对搅拌摩擦焊接接头的微观组织和力学性能的影响。结果表明,当转速为800 r/min、焊接速度为200 mm/min、焊接工具轴肩直径为12 mm时,可得到表面美观、致密无缺陷的搅拌摩擦焊接接头。焊核区发生动态再结晶,形成细小的等轴晶。经固溶处理后,焊核的上部及底部晶粒都发生了异常长大,而中部区域晶粒仍然为细小的等轴晶组织。焊态接头的拉伸试样断裂在母材位置,抗拉强度达到199 MPa,与退火态母材抗拉强度相当,断后伸长率达到12%。在新淬火状态下,接头的抗拉强度为310 MPa,为相同热处理母材的91.4%,断后伸长率为11.2%,试样断裂在焊核区,呈不完全的韧性断裂。     

Adaptive volumetric heat source models for laser beam and laser + pulsed GMAW hybrid welding processes

Laser + pulsed gas metal arc welding (GMAW) hybrid welding process is an attractive joining technology in industry due to its synergy of the two processes. It is of great significance to conduct fundamental investigations involving mathematical modeling and understanding of the hybrid welding process. In this study, an adaptive heat source model is first developed for laser beam welding. Through combining the ray-tracing method with the keyhole profile determination technique based on the local energy balance, the keyhole shape and size are calculated and correlated to the distribution parameters of the volumetric heat source model. Then, thermal action characteristics in laser + pulsed GMAW hybrid welding are considered from viewpoint of macro-heat transfer, and a combined volumetric heat source model for hybrid welding is developed to take consideration of heat input from laser, pulsed gas metal arc, and overheated droplets. Numerical analysis of thermal conduction in hybrid welding is conducted. The shape and size of fusion zone and weld dimension in the quasi-steady state are calculated for various hybrid welding conditions, which have a fair agreement with the experimental results.     

电弧波形与气体保护焊熔滴过渡模式关系研究

利用焊接质量分析仪采集气体保护焊焊接过程中瞬时电流和电压波形特征，利用此波形特征能够定性指出熔滴过渡模式，从而实现在线监测和控制金属熔滴的过渡模式，实现良好的焊接工艺参数。     

Prediction of metal deposition from arc sound and weld temperature signatures in pulsed MIG welding

The weld deposition efficiency is an important economic factor like productivity and weld quality in gas metal arc welding (GMAW). There is a strong relationship between arc sound signals and arc stability (or deposition efficiency) in GMAW. In this work, the variation of weld deposition efficiency with various pulse parameters in pulsed metal inert gas welding was investigated. The arc sound signal along with current and voltage signals were acquired and analyzed in time domain as well as in frequency domain. The sound signal kurtosis and arc power were found to be highly correlated with welding process stability. The weld deposition efficiency was also related to weld surface peak temperature. Finally, an attempt was made to correlate the sound time domain as well as frequency domain features of sound signal with the deposition efficiency. The variation of pulse shape with the duty factor also influenced the deposition efficiency as evidenced by in fast Fourier transform analysis.