MODEL OF LASER-TIG HYBRID WELDING HEAT SOURCE

The welding mechanism of laser-TIG hybrid welding process is analyzed. Withthe variation of arc current, the welding process is divided into two patterns: deep-penetrationwelding and heat conductive welding. The heat flow model of hybrid welding is presented. As todeep-penetration welding, the heat source includes a surface heat flux and a volume heat flux. Theheat source of heat conductive welding is composed of two Gaussian distribute surface heat sources.With this heat source model, a temperature field is calculated. The finite element code MARC isemployed for this purpose. The calculation results show a good agreement with the experimental data.

Welding characteristics in different laser-TIG hybrid manners

An experiment for determining the laser-TIG hybrid welding characteristics was carried out in three kinds of hybrid methods: CO_2 laser-TIG coaxial hybrid, CO_2 laser-TIG paraxial hybrid and Nd: YAG laser-TIG paraxial hybrid. The experimental results indicate that hybrid welding has two welding mechanisms in CO_2 laser-TIG hybrid welding: deep penetration welding and heat conduction welding. As the effect of the laser-induced keyhole, the arc root is condensed, the current density and penetration depth increase significantly, the welding characteristic is apt to deep penetration welding. When current increases to some degree, the keyhole induced by laser disappears, which produces a shallow penetration and wide bead. The weld exhibits heat conduction welding characteristics. Furthermore, the arc images and weld bead cross-sections of three kinds of hybrid manners were also compared and analyzed at different welding currents, which established the foundation for understanding the welding characteristics of laser-TIG hybrid welding comprehensively.

Novel hybrid method: pulse CO_2 laser-TIG hybrid welding by coordinated control

In continuous wave CO2 laser-TlG hybrid welding process, the laser energy is not fully utilized because of the absorption and defocusing by plasma in the arc space. Therefore, the optimal welding result can only be achieved in a limited energy range. In order to improve the welding performance further, a novel hybrid welding method--pulse CO2 laser-TIG arc hybrid welding by coordinated control is proposed and investigated. The experimental results indicate that, compared with continuous wave CO2 laser-TIG hybrid welding, the absorption and defocusing of laser energy by plasma are decreased further, and at the same time, the availability ratio of laser and arc energy can be increased when a coordinated frequency is controlled. As a result, the weld appearance is also improved as well as the weld depth is deepened. Furthermore, the effect of frequency and phase of pulse laser and TIG arc on the arc images and welding characteristics is also studied. However, the novel hybrid method has great potentials in the application of industrials from views of techniques and economy.

Research on weldability of ZL101/TiB2 MMCs by laser-TIG hybrid welding

The weldability of in situ TiB2 reinforced ZL101 metal matrix composites （ MMCs） was examined using laser-TIG hybrid welding technology. High speed camera was employed to observe the coupled results between laser plume and electric arc. Optical microscope （OM） , scanning electron microscope （SEM） , tensile machine and wearing equipment were used to evaluate the quality of welding joint. The effective hybrid welding was realized and defect-free seam was obtained when the laser power （8 kW）, TIG current （ 100 A） and welding speed （3 nv/min ） were combined. TiB2 distribution became much more homogeneous than the pre-welded, and microstructure of seam was .finer obviously. Tensile and wear resistance test showed that the weld seam presented higher strength and better wear-reslstance properties than the base metal. The results indicated that TiB2 reinforced aluminum matrix composites were successfully welded using the laser-T1G hybrid welding method.

Microstructure and mechanical properties of wrought magnesium alloy AZ31B welded by laser-TIG hybrid

The laser-TIG hybrid welding was mainly used to weld the wrought magnesium alloy AZ31B. The technical characteristics of laser-TIG hybrid welding process was investigated and the interactional mechanism between laser and arc was discussed, at the same time the microstructure and mechanical properties of the wrought magnesium alloy AZ31B using laser-TIG hybrid welding were analyzed by optical microscope, EPMA, SEM, tensile machine, hardness machine. The experimental results show that the presence of laser beam boosts up the stability of the arc during high speed welding and augments the penetration of weld; the crystal grains of magnesium alloy weld are fine without porosity and cracks in the best welding criterion and the microstructure of HAZ does not become coarse obviously. The elements profile analysis reveals that Mg content in the weld is lower than that of the base metal, but Al content is higher slightly. Under this experimental condition, the wrought magnesium alloy AZ31B joint can be achieved using laser-TIG hybrid process and the tensile strength of the joint is equivalent to that of the base metal.

TC4钛合金激光-TIG复合焊焊缝成形与组织研究

通过对TC4钛合金进行激光-TIG(钨极氩弧焊)复合焊接,研究了不同TIG电流大小对接头表面形貌、焊缝成形、显微组织的影响。结果表明,TC4钛合金在激光-TIG复合焊接下可以形成连续完整的焊接接头。且随着电流增加,焊缝横截面由“钉子”形状逐渐转变为“漏斗”形状,平均气孔面积则先减少后增加,并在电流I=50 A时达到最小值。在激光-TIG的复合作用下,随着电流增加,熔池流动更加剧烈,焊缝的晶粒先减小然后增大。焊缝的显微组织主要是由针状α’马氏体和β相带相互交织而成的网篮组织、α_(gb)相和魏氏组织组成。当电流I=50 A时,焊缝α’马氏体束之间的β相带宽度更宽,平均宽度为0.91μm。

工艺参数对304不锈钢脉冲Nd:YAG激光/TIG电弧复合焊焊缝成形的影响

研究了304不锈钢脉冲Nd:YAG激光/TIG电弧复合热源焊接工艺参数对焊缝成形的影响.结果表明,脉冲Nd:YAG激光/TIG电弧复合焊焊缝横截面面积大于单一激光焊焊缝横截面面积与单一TIG焊焊缝横截面面积之和,具有协同效应;激光功率增大时,复合焊焊缝熔深和熔宽均增大,复合焊焊缝横截面面积增大,复合热源热效率也增大;离焦量从-3 mm增大到5 mm的过程中,复合焊焊缝熔深、熔宽、焊缝横截面面积和复合热源热效率均先增大,在离焦量为-1 mm时达到最大值,然后随离焦量的进一步增大而减小;焊接速度减小时,复合焊焊缝熔深、熔宽和焊缝横截面面积均增大,但复合热源热效率减小.

高速TIG-MIG复合焊焊缝驼峰及咬边消除机理

搭建了TIG-MIG复合焊试验平台及电参数—高速图像同步采集系统,进行了一系列低碳钢高速TIG-MIG复合焊工艺试验,研究了高速TIG-MIG复合焊的电弧形态、熔滴过渡及熔池行为对焊缝成形的影响,并确定了合适的匹配参数.结果表明,MIG焊电流在240~300 A,且TIG焊电流与MIG焊电流相当时,TIG-MIG复合焊焊接过程稳定,即使在焊接速度高达2.5 m/min时,焊缝仍无驼峰、咬边等缺陷,与传统MIG焊相比,熔深增加,熔宽减小.TIG-MIG复合焊由于电弧间的相互作用,两电弧指向发生偏转,电弧压力减小,焊接过程不产生弧坑,且熔宽变窄,这是避免驼峰和咬边缺陷的主要原因.

钛合金激光-TIG复合焊接保护状态对焊缝成形及性能影响

用激光-TIG复合热源对2.5 mm厚TA15钛合金进行对接焊试验.利用万能力学拉伸机、红外热成像仪、电子探针(EPMA)、扫描电镜(SEM)等分析手段对焊接接头进行测试分析,并与单TIG焊进行对比.分析焊接工艺参数和接头保护时间对焊接接头形貌和性能的影响.结果表明,实现2.5 mm厚钛合金全熔透焊接时,激光-TIG复合焊比单TIG焊速度更快、热输入更低,焊缝和热影响区更窄,晶粒更细;相同保护条件下,激光-TIG复合焊接头比单TIG焊接头具有更高的强度、塑性和更好的疲劳性能;激光-TIG复合焊缝冷却速率高于单TIG焊,获得良好的保护状态时所需保护时间更短.

硬质合金激光-TIG复合焊焊缝成形及缺陷分析

针对硬质合金焊接过程中容易出现的未熔透、气孔以及裂纹等缺陷,以硬质合金与因瓦合金的焊接为研究对象,分析了在其激光-TIG复合焊过程中焊缝成形、气孔和裂纹的形成原因及其影响因素,初步讨论了硬质合金激光-TIG焊接过程的缺陷及其分布位置特征。

镁合金激光-TIG焊接温度场的红外测量与数值模拟

以变形镁合金AZ31B为研究对象,采用红外热像仪拍摄镁合金激光-TIG复合热源焊接过程中的焊接温度场,提出一种基于红外辐射测温原理。并针对红外热像仪的焊接温度场校正方法,采用热电偶验证该校正方法的准确性。利用数值模拟方法模拟整体温度场。试验结果表明,实温校正可准确校正试件表面状态一致区域的温度场,而表面校正可消除试件表面状态改变而引起的对温度场分布的影响,结合实温与表面校正方法能准确地校正镁合金激光-TIG复合热源焊接过程中电弧覆盖范围外的温度场,焊接温度场数值模拟可以比较准确预测并反映整体焊接温度场实际分布。

铝合金/碳钢激光-TIG复合热源熔钎焊工艺与接头显微结构分析

文中提出了一种激光-TIG复合热源熔钎焊新方法，实现了铝合金与碳钢的对接熔钎焊，并研究了焊接工艺对接头特性的影响.采用扫描电镜（SEM）、能谱分析（EDS）和电子材料试验机对接头显微结构与力学性能进行研究.结果表明，接头最大抗拉强度为83.6 MPa，断裂发生在钢/焊缝界面，断裂形式为脆性断裂.钢/焊缝界面不同位置处界面层厚度不同，在3-12 μm之间.界面层由两部分组成，即靠近钢一侧为η-Fe2Al5，靠近焊缝一侧为τ5-Al7.2Fe2Si；远离界面层的焊缝区主要由α-Al基体和Al-Si共晶相组成.

添加过渡层的镁合金/钢激光-TIG电弧复合熔化焊接机制

激光-电弧复合热源技术较单一热源焊接技术相比,具有热源能量密度梯度及热力耦合模式可优化设计等特点,成为实现关键零部件精确成形成性焊接制造的重要方法.文中以镁合金/钢为代表的难固溶不反应异质材料为研究对象,提出多组元液相共存的镁合金/钢激光-TIG电弧复合焊接新思路,利用激光-TIG电弧复合焊接热源所具有的能量密度梯度分布特征,通过添加Cu-Zn过渡层,实现镁合金/钢异种金属高质量熔化焊接,并对铝元素的作用进行了探讨.

铝合金双光束/单光束激光-TIG复合焊

针对4mm厚5A06铝合金,分析了双光束光纤激光-TIG复合焊的焊缝成形特点、气孔率、匙孔动态特征及接头力学性能,并与单光束光纤激光-TIG复合焊对比。结果表明,在获得相同焊缝背面熔宽条件下,与单光束激光-TIG复合焊相比,双光束激光-TIG复合焊的焊缝背面成型连续性、均匀性更优且熔宽波动较小,焊缝气孔率降低50%以上,激光匙孔开口面积平均值更大,波动变异系数更小;双光束激光-TIG复合焊接头抗拉强度、断后伸长率、显微硬度、组织与单光束激光-TIG复合焊结果差别不大。

低碳钢等离子-TIG耦合电弧高效复合焊接工艺性能分析

针对低碳钢材料焊接效率低的问题,提出了等离子-TIG耦合电弧焊接方法,通过设计集约化枪体结构促使等离子和TIG电弧在电磁力作用下实现稳定耦合,优化复合焊接热源特征,并研究了电弧形态、焊缝成形和力学性能.结果表明,等离子-TIG耦合电弧具有优异的深熔焊接特性,相对于等离子和TIG焊接方法具有更加合理的深宽比,且对熔滴、熔池有震荡搅拌效果,促使晶粒细化,并降低熔合区联生结晶倾向.使用5mm厚Q235B钢板进行对接试验,实现了稳定的单面焊接双面成形,焊缝美观无缺陷且抗拉强度优于母材.

低功率YAG激光-TIG电弧复合焊接镁合金薄板工艺

以2 mm厚AZ31B变形镁合金薄板为研究对象开展低功率脉冲YAG激光-TIG电弧复合热源焊工艺研究,分析了激光与电弧的能量匹配对焊缝成形的影响规律.结果表明,镁合金薄板低功率YAG激光-TIG电弧复合热源焊接过程中,激光能量与电弧能量之间的相互匹配将直接影响焊缝的表面成形,获得理想焊接接头的工艺参数区间相对较狭小.为使焊缝成形均匀连续,焊接过程中需要对焊缝背面采用氩气进行保护,当保护气体流量为5～10 L/min时获得了具有最佳性能的焊接接头,其拉伸载荷达到镁合金母材的95%以上.

TIG焊电弧辅助MIG焊引弧过程分析与机理探讨

在TIG-MIG复合焊中,先引燃的TIG焊电弧能够辅助MIG焊实现非接触引弧,且在整个非接触引弧过程中不产生焊接飞溅.利用电信号与高速摄像同步采集系统获取MIG焊引弧过程的电弧电压、焊接电流和电弧图像,研究了先引燃的TIG焊电弧及其参数变化对MIG焊引弧过程及引弧方式的影响.结果表明,细长放电通道形成于MIG焊丝末端与TIG焊电弧之间是TIG焊电弧辅助MIG焊实现非接触引弧的关键;TIG焊电弧辅助MIG焊实现非接触引弧对TIG焊接参数的变化具有良好的适应性.此外,基于气体间隙击穿的流注理论,探讨了细长放电通道的形成过程,揭示了TIG焊电弧辅助MIG焊实现非接触引弧的机理.

TA15钛合金薄板激光-TIG复合焊接头疲劳性能研究

针对复合热源焊接在钛合金航空结构件的应用,开展了2.5 mm厚TA15钛合金薄板激光-TIG电弧复合热源对接结构焊接试验。并对TIG焊接头、复合热源焊接接头和母材进行了疲劳测试分析,分别计算各自在不同应力水平下的中值疲劳寿命,采用扫描电镜(SEM)对复合热源焊接接头疲劳试样断口进行观察以了解断裂路径。结果表明:复合热源焊接接头疲劳断裂发生在热影响区,复合热源焊接接头疲劳寿命大于TIG焊接头,在560、672、784、896 MPa应力水平下时复合热源接头疲劳寿命分别为母材的91.5%、90.6%、82.7%、84%。。断口由疲劳源区、裂纹稳定扩展区和瞬断区组成,起裂源位于试件表面。

7A52铝合金TIG-拉弧螺柱焊工艺

以高强铝合金7A52为主要研究对象,研究TIG-拉弧复合热源焊接高强铝合金螺柱的工艺特点,利用正交试验分析焊接规范对焊缝成形的影响。试验结果表明:TIG热源的加入大大增加了高强铝合金螺柱焊接时电弧的稳定性。在最佳的工艺条件下高强铝合金螺柱接头焊缝成形良好,无烧损、裂纹等缺陷,焊接接头抗剪强度可达母材强度70%以上,表明TIG-拉弧复合热源螺柱焊是一种理想的高强铝合金焊接工艺。

激光-TIG复合焊接工艺参数对430不锈钢接头性能的影响

针对400系不锈钢焊接过程中焊缝附近晶粒极易长大而产生脆化,使焊接接头性能较差,很大程度上限制了其在工业领域的广泛应用,采用激光-TIG复合热源焊接冷轧430不锈钢,对焊接接头的力学性能进行了研究。结果表明,激光功率与焊接速度对焊接接头的抗拉强度和抗折能力影响最为明显,优化工艺的焊缝抗拉强度最高可达母材的89.65%、抗折强度达母材的83.53%。