激光+双丝脉冲MAG复合焊的焊接稳定性

研究激光和Ar+He混合气体中He气体体积分数对激光+双丝脉冲MAG复合焊焊接稳定性的影响。搭建激光+双丝脉冲熔化极活性气体保护(Metal active-gas, MAG)复合焊焊接系统,利用LabVIEW信号采集系统采集焊接电流和电弧电压波形,借助高速摄像系统同步拍摄电弧形态和熔滴过渡过程,实时监测焊接过程。观察后丝短路和前丝断弧情况并对前丝电弧电压进行单因素方差分析,研究Ar+He混合气体中He气体体积分数对焊接稳定性影响;比较焊接过程中激光的有无对熔滴过渡的影响,分析激光对焊接稳定性影响。结果发现随着He气体体积分数增大,后丝对应短路次数增多,当He气体体积分数为50%时,前丝出现断弧现象,大于50%,断弧时间随之增加,焊接稳定性变差;激光+双丝脉冲MAG复合焊和双丝脉冲MAG复合焊相比,加入激光可稳定电弧,为熔滴提供一附加力,该力促进熔滴过渡,使熔滴过渡尺寸减小,加大过渡频率,改善熔滴过渡,提高焊接稳定性。     

活性激光电弧复合焊接法研究

为了进一步提高激光电弧复合焊接的熔深,提出活性激光电弧复合焊接法。在氧气的保护下,用小功率光纤激光在待焊焊件表面进行预熔处理,使表面熔化生成一层氧化层,然后用激光电弧复合焊接覆盖氧化层,达到增加熔深的目的。结果表明,激光预熔后进行激光电弧复合焊接,电弧明显收缩,熔深增加1.5倍左右,表面成形良好。激光预熔后,焊缝含氧量增加,熔池表面张力温度系数由负变正,使得复合焊接熔深增加。研究工艺参数对焊缝熔深和熔宽的影响,随着激光预熔功率的增加,熔深增加熔宽减小;随着电流的增加,熔深熔宽都增加,但激光预熔后的焊道增加更快。随着复合焊接速度的增加,熔深和熔宽都减小。随着复合焊接中激光功率的增加,熔深增加,对熔宽的影响较小。利用活性激光电弧复合焊接法,可以得到较为细小的焊缝组织,提高焊接接头的抗拉强度,能达到母材抗拉强度的95%,且面弯和背弯180°后未出现裂纹,表明接头具有良好的韧性。     

激光-电弧复合焊后的高强钢微观组织分析

介绍了使用激光-电弧复合焊方法焊接高强钢的机理,进行了高强钢的激光-电弧复合焊试验,并对焊接后的高强钢焊接接头进行维氏硬度测试和微观组织分析研究。     

高功率CO2激光＋电弧复合焊技术在船舶制造业中的应用

激光复合焊技术作为一种快速高效的焊接方法,具有焊缝深宽比大、焊接变形小等优点,在船舶制造业中有着广阔的应用前景。本文分析了高功率CO2激光＋电弧复合焊技术的特点,采用高速摄像法对光致等离子体与电弧的交互过程进行了观察分析,开展了16mm和12mm厚国产船用低合金高强钢激光复合焊对接和T形接头的工艺研究。     

不同波长激光对激光—MAG电弧复合焊接熔滴行为的影响

通过计算分析了金属对Nd：YAG激光和CO2激光的吸收率;以8.0mm厚高强钢板为试验材料,采用高速摄像系统观测熔滴过渡模式和等离子体形态的变化.建立脉冲MAG焊接熔滴力学模型,从熔滴受力角度分析了不同波长两种激光YAG激光和C02激光在激光—MAG焊接中对熔滴过渡形式和熔滴过渡频率的影响.结果表明,Nd：YAG激光和CO2激光输出特性存在差异,金属表面对YAG激光的吸收率约为CO2激光的3倍多;在焊接电流180A、焊接电压26V、光丝间距3mm的相同条件下,YAG激光—MAG电弧复合焊接熔滴过渡频率高于CO2激光—MAG电弧复合焊接的熔滴过渡频率,且熔滴过渡频率均随着激光功率的增加而降低,但是增加等量的激光功率,YAG激光—MAG电弧复合焊接熔滴过渡频率下降幅度更大;CO2激光—MAG电弧复合焊接过程中,熔滴的过渡形式由射滴过渡转变为颗粒过渡,在YAG激光—MAG电弧复合焊接过程中,熔滴过渡形式主要为射滴过渡.     

激光-MAG复合焊接技术在超高强钢上的应用分析

激光-电弧复合焊接技术具备焊接效率高、焊接变形小、焊接接头强度高、焊接工况适应性好、单面焊双面成形与柔性自动焊接等优点,已在高强钢、铝合金等结构件的焊接制造领域广泛应用。对激光-MAG复合焊接技术在超高强钢上的应用进行了分析,重点研究了其焊接工艺性、焊缝组织结构及焊接接头性能,解决了超高强钢与特种车辆车体构件的激光-MAG复合焊接工程化应用技术问题,达到了提高焊接接头性能、焊接质量及其稳定性,提高焊接效率,降低焊接变形的目的。     

面能量对激光—电弧复合焊接焊缝及熔滴过渡的影响

引入面能量的定义,从激光功率、电弧参数和焊接速度等方面来研究面能量的变化对焊缝熔深、熔宽、焊缝成形系数和熔滴过渡的影响,试图建立激光能量与电弧能量之间的最佳配比关系以及面能量与熔深的定量关系。采用高速摄像系统观测熔滴过渡模式和等离子体形态的变化,并采集焊接过程中的电弧和熔滴图像;利用激光共聚焦显微镜观察焊缝形貌,并测量焊缝熔宽、熔深等数据。试验研究发现:激光与电弧两热源之间存在最优匹配范围;电弧电压与焊接电流之间存在U(15 1)0.05I的关系式;焊接速度的降低与焊缝熔深的增加并非线性关系,可选择的焊接速度是一个区间,该区间内存在一个最佳的焊接速度,并对应一个最佳的面能量。因此,在具体的激光—电弧复合焊接中,需要根据板厚、接头形式等确定激光与电弧的能量参数,选择合适的面能量。     

激光功率对CO2激光-MAG电弧复合焊电弧与熔滴行为的影响

采用高速摄像系统观测熔滴过渡模式和等离子体形态的变化,并采集焊接过程中的电弧和熔滴图像,利用电弧分析仪记录电弧信号,通过试验深入研究激光功率对CO2激光-熔化极活性气体保护焊(Metal active gas,MAG)电弧复合焊接的电弧形态、焊接稳定性、熔滴过渡频率的影响。研究表明,焊接电流的增加减小了实际热源间距,并且实际热源间距在2 mm附近效果最佳;带电粒子在主辅导电通道内的运动产生扰动或漂移、焊接模式的跳变和过渡模式的改变是电流、电压波形出现紊乱和尖角波形的主要原因;激光的加入降低了熔滴过渡频率和过渡稳定性;焊接电流为160A、180 A时,激光-电弧复合焊接的熔滴过渡频率均随着激光功率的增加而先减小后增大,但其过渡频率介于160 A和180 A电弧焊接时熔滴过渡频率之间。     

激光-电弧复合焊过程的熔滴过渡特征与受力分析

利用高速相机对高氮钢激光-电弧复合焊接过程的熔滴过渡、熔滴形态、等离子体形态进行采集与分析。采用图像处理与数学计算相结合的方法给出熔滴在电弧空间飞行时的受力大小和加速度。初步计算激光产生的金属蒸气对熔滴的反冲力的大小和分布。结果表明:熔滴呈现颗粒过渡的临界焊接电流为180 A附近;熔滴呈现射滴过渡的临界焊接电流200 A附近。激光的加入对电弧具有明显的压缩作用,在熔池表面这种压缩作用更为剧烈。通过观测和计算给出电弧焊和激光-电弧复合焊时熔滴刚脱离焊丝的加速度分别达到70 m/s~2和50 m/s~2。在实际复合焊接过程中,当熔滴落入熔池位置与激光匙孔间距为3 mm时,从激光匙孔喷发的金属蒸气对熔滴的反冲力非常小。激光的加入主要改变了电弧形态,近而改变熔滴上下表面的压力差,使得熔滴在接近熔池表面发生合并和过渡频率减慢。     

中厚板高强钢Q460C高效气保焊工艺实验研究

采用高效气保焊工艺,可以提高中厚板高强钢Q460C的焊接性能.因此,通过实验对该工艺过程进行研究.研究结果表明:通过采用双丝双弧气保焊大熔深工艺来增加熔深,解决了根部熔合质量问题,同时在不开坡口的形式下获得了更高的焊接速度;焊后焊接接头的抗拉强度达到825 MPa,断裂位置发生在母材上,焊接接头的硬度及冲击功力学性能指标均满足标准要求.     

Investigation on droplet momentum in VPPA-GMAW hybrid welding of aluminum alloys

Variable polarity plasma arc-gas metal arc welding (VPPA-GMAW) is a superior technology for welding thick plates of high-strength aluminum alloys. It integrates the advantages of energy focusing and high penetration depth in VPPA welding, and those of high welding efficiency and wide range of technological parameters in GMAW process. In this work, we investigated the droplet momentum in paraxial VPPA-GMAW hybrid welding of 7A52 aluminum alloys, and the technological parameters of welding process was also optimized. The images of droplet transfer were captured by high-speed camera, while the droplet speeds and sizes were statistically analyzed by t tests of independent samples. The results showed that the speeds of droplet arriving at the weld pool were significantly between GMAW and VPPA-GMAW processes, and the droplet speed increases with increasing plasma currents within a certain range. Meanwhile, the droplet momentum in VPPA-GMAW process is larger than that in conventional GMAW process. We also found that as the droplet momentum increased, the depression of weld pool grew more obvious and greatly facilitated the deep-penetration welding. In VPPA-GMAW process, it became more and more easier for the droplet to fall off the wire when the electromagnetic force gradually increased during pulse period. Droplet movement through the arc zone was further accelerated since the central pressure of arc column increased during base period. This research can provide some theoretical support for thick plate welding of high-strength aluminum alloys and help for deeper understanding of the hybrid arc coupling mechanism.     

排布方式对铝合金激光-MIG复合横向焊接特性的影响

采用常规激光-熔化极惰性气体保护电弧(Metal inert gas,MIG)复合横向焊接铝合金过程中,焊缝表面极易出现咬边和下塌等缺陷,由此开展排布方式对激光-MIG电弧复合横向焊接铝合金焊接特性的影响研究。分析二者的排布方式对熔池特征、熔滴过渡形式以及焊缝成形规律的影响。试验结果表明,异面引导复合焊接方式对焊缝成形有明显改善作用,焊缝表面熔宽减少、中心线偏移和咬边缺陷得到有效抑制。采用同面引导复合方式时,熔滴过渡到匙孔后方,熔池下侧熔融金属大量堆积并产生周期性的波动,导致焊缝结晶组织出现了分层现象;而采用异面引导复合方式时,熔滴过渡到匙孔下方,并且熔滴在熔池中的落点位置与同面引导方式相比要偏上,熔滴过渡频率稍低,此时熔池中熔融金属分布较为均匀,熔池下部堆积金属较少,有效抑制了焊缝的下塌和咬边缺陷。     

CHARACTERISTICS OF DROPLET TRANSFER IN CO2 LASER-MIG HYBRID WELDING WITH SHORT-CIRCUITING MODE

LF6 aluminum alloy plates with 4.5 mm thickness are welded in this experiment.Welding is carried out by using the CO2 laser-MIG paraxial hybrid welding in flat position. The experimental results indicate that the inherent droplet transfer cycle time of conventional MIG arc is changed due to the interaction between CO2 laser beam and MIG arc in the short-circuiting mode of laser-MIG hybrid welding. Because of the preheating action of CO2 laser to electrode and base material, the droplet transfer frequency of MIG arc is increased in the hybrid welding process. When laser power is increased to a certain degree, the droplet transfer frequency is decreased due to the effect of laser-induced keyhole. Furthermore, through analyzing the MIG welding current and arc voltage waveforms and the characteristics of droplet transfer in the hybrid welding process, the effect of laser energy and the action point between laser beam and arc on the frequency of droplet transfer and weld appearance is investigated in details.     

深窄间隙焊接技术在大厚度构件材料焊接中的应用研究

窄间隙焊接技术作为一种高效焊接方法以其大大降低熔敷量和节约制造时间的优点,使其在大厚度构件制造中具有广阔的应用前景,但是焊接过程的稳定性及侧壁熔合等缺陷的存在,成为影响构件高品质制造的关键问题。利用深窄间隙埋弧焊接方法成功制造了外径尺寸为2 500 mm,厚度达150 mm的转子模拟件,采用多层双道焊接方法,实现了良好的侧壁熔合效果,且未发现夹杂等缺陷,表面该焊接接头具有较高的成形质量。基于该焊接接头开展冲击韧度、拉伸等力学性能试验,表明该接头的力学性能完全满足使用需求。从而验证了深窄间隙焊接技术在大厚度核电转子焊接中应用的可靠性。     

FeAl合金氩弧焊工艺和接头性能研究

试验研究了ＦｅＡｌ合金的钨极氩弧焊焊接工艺和焊接接头的组织与性能。结果表明，以条状母材和１Ｃｒ１８Ｎｉ９Ｔｉ焊丝为填充材料，选择合适的焊接工艺参数，都可获得达到母材强度８０％的焊接接头；焊缝边缘处易获得树枝晶，焊缝中心处易获得等轴晶；焊接热影响区为回复和再结晶组织     

Study on arc characteristics and their influences on weld bead geometry in narrow gap GMAW of 5083 Al-alloy

As an efficient process, narrow gap gas metal arc welding (NG-GMAW) was employed to join thick plates of 5083 Al-alloy. In this paper, arc characteristics in NG-GMAW of 5083 Al-alloy and their influence on the weld bead geometry were studied with synchronous acquisition system for various groove types, welding modes, welding current levels, and swing frequencies. The arc profiles were measured and appear to be entirely different compared with that in bead-on-plate GMAW process, meanwhile the arc size changes with varied welding mode, welding current, and arc swing frequency. Arc characteristics highly affect the weld bead geometrical parameters such as bead width, welding penetration, sidewall penetration, and weld surface concavity. Linear regressions were made between the arc characteristics and the weld bead geometrical parameters both in swing and non-swing arc process. It showed that a negative linear correlation exists between welding penetration and arc length, sidewall penetration, and arc warpage, while a positive linear correlation exists between weld surface concavity and arc warpage in non-swing arc process. In contrast, a non-linear correlation exists among them and the variation tendency remains the same in swing arc process.     

Evaluation on microstructure and mechanical properties of high-strength low-alloy steel joints with oscillating arc narrow gap GMA welding

Abstract with the purpose of improving weld joint quality and productivity, the oscillating arc narrow gap gas metal arc (GMA) welding was employed in welding quenched and tempered high-strength low-alloy thick steel. The microstructure and mechanical properties of weld joints were evaluated, namely micro-hardness, tensile strength, and low-temperature impact toughness. The test results indicated that mechanical properties of weld joints with oscillating arc narrow gap GMA welding were excellent and found to meet stipulated requirements. Oscillating arc narrow gap GMA welding is a promising process for welding quenched and tempered HSLA thick steels due to the low energy input and narrow square-butt groove.     

The effect of DSAW on preheating temperature in welding thick plate of high-strength low-alloy steel

Double-sided double arc welding (DSAW), a high efficiency method requiring no back chipping for welding thick plate of high-strength low-alloy steel was used in this study. Gas metal arc welding is employed for backing run and filler passes. The effect of DSAW on preheating temperature is investigated. Meanwhile, numerical simulation has been performed to predict transient temperatures, which are in good agreement with the experimental results. The critical stress in DSAW without preheating is 528.31 MPa, while in conventional welding with 100 °C preheating temperature, it is 393.44 MPa. The higher critical stress implies that the samples in DSAW without preheating have better cold crack resistance than those in conventional welding with 100 °C preheating temperature. Y-slit type cracking test indicates that the samples welded by double-sided double arc demonstrate better cold crack resistance than conventional welding at the same preheating temperature. Therefore, DSAW can realize welding thick plate of high-strength low-alloy steel with lower preheating temperature or even without preheating.