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旁路等离子-MIG复合工艺是通过等离子焊枪的导电铜嘴与焊丝之间形成的分流弧、焊丝与母材之间的主路弧同轴耦合进行焊接的新型工艺,不但保持了MIG焊的高效性,还可以通过对旁路电流的调节实现焊接过程能量的精确控制.为了深入了解该工艺条件下复合电弧与耦合熔池的物理作用机制,通过建立流体动力学瞬态计算模型,并基于合理的试验验证,对旁路电流加载前后气液两相内部及界面处的传热传质行为进行了对比研究.结果表明,相比未加载旁路电流时,电弧的最高温度下降约1 000 K,同时电弧与耦合熔池交界处的有效热通量整体下降;熔池内部液态金属回流速度明显下降,因此导致熔深和熔宽尺寸均有所减少;复合电弧和耦合熔池的最大电磁力方向没有改变,但数值均有所降低. 相似文献
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通过建立等离子弧焊接熔池的三维数学模型,并以小孔动态演变过程与热源模型之间的相互耦合作用为基础,研究熔池内部的传热和流动过程,并由此建立出热源的动态模型。小孔形状尺寸可以通过体积流函数法得到,同时可建立小孔形状与热源模型之间的耦合关系。得到等离子弧焊接的温度场、流场和小孔的动态演化规律后,实验验证了焊接横断面熔池形状尺寸和小孔的穿孔形状尺寸的理论结果。 相似文献
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在建立TIG焊接熔池液面三维形状模型基础上,对电弧力作用于熔池液面进行了表征,采用Surface Evolver有限元分析软件进行数值模拟,研究了电弧力对TIG焊接熔池液面三维形态的影响.得到了有电弧作用时,熔池的三维形态和熔池各液面参数随电弧力大小变化的规律.结果表明,在熔池形状一定时(正面、背面熔化区域半径和板厚一定),电弧力的作用深度增加会引起熔池上、下液面和固液面的表面积均增加,其中电弧力的大小对TIG焊接熔池的上液面影响程度大于下液面.这些分析结果为探讨TIG焊接熔池的各类问题提供了基础. 相似文献
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基于FLUENT软件,建立了适用的熔化极气体保护焊(gas metal arc welding, GMAW)熔池动态行为数值分析模型,该模型考虑了气—液—固三相耦合. 将电弧热输入视为双椭球体热源模型,将电弧等离子体描述为高速流向熔池的氩气,其流速呈高斯分布,流速峰值依据焊接电流确定,电弧压力与电弧等离子体对熔池表面的切应力在计算过程中获得;将熔滴过渡视为高温液态金属从熔池上部一定区域以一定速度流入熔池过程,通过对流速施加时间脉冲函数表征熔滴过渡频率. 利用该模型对不同条件下GMAW焊熔池热场及流场进行模拟计算,并分析其流体动力学特征. 结果表明,模型能够合理地反映熔池动力学特征,同时还提高了计算效率. 相似文献
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穿孔型等离子弧焊接热-力耦合模型优化 总被引:3,自引:3,他引:0
K-PAW的焊接过程是等离子电弧对被焊工件热与力的耦合作用.文中基于FLUENT软件,依据流体动力学理论,对穿孔型等离子弧焊接过程熔池、流场和小孔进行了热-力耦合模型分析,提出了随穿孔深度增加,能量和电弧压力二次变化的计算优化模型,使维持小孔壁面稳定的力同时作用在小孔内部和物理边界上,初步实现了穿孔型等离子弧焊接从开始到穿透工件及穿孔后焊接过程的数值模拟.计算结果表明,焊接时间为0.25 s时,熔池已开始熔化并出现下凹变形,穿孔型等离子弧焊接穿孔时间为2.15 s,焊接3.00 s后小孔和熔池达到稳定状态,与试验测得的穿孔时间吻合良好,在穿孔动态过程中穿孔形态吻合良好,熔合线走势基本相同.另外,在平行于焊缝的截面上观察,熔池内部易出现逆时针环流. 相似文献
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为探索焊接过程实现高稳定性工艺的潜在途径,最大限度地减少重要钢结构制造中焊缝咬边及成形缺陷带来的焊后返修工作,提出并试验了一种利用埋弧焊渣金间随焊施加辅助外电场对渣金电导载流进行导流,进而提高焊接工艺稳定性的方法,并应用焊接电信号分析仪对弧压信号进行了采集统计分析.结果表明,以钨电极作阴极利用电场在渣金熔体内部形成稳定的电导载流,可使熔渣电导性能得以改善,并引导电子进入电弧阴极中心以增强电弧的集聚程度.同时外电场作用也使渣金内部的带电粒子形成有序运动并在界面结合成低表面能的活性氧化物,又可改善液态熔渣在焊缝金属表面的润湿铺展性能.实施辅助电场引入的这些有益作用使焊缝形状、表面光洁度、尤其是焊缝边缘平直均匀性得到较好地改观,焊接过程工艺稳定性得以进一步提高. 相似文献
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《Science & Technology of Welding & Joining》2013,18(8):683-693
AbstractIn order to understand the temperature fields, cooling rates and mixing in the weld pool, a comprehensive, three-dimensional heat transfer and fluid flow model is developed and tested by comparing model predictions with two sets of experimental data. The first set of data was taken from the literature. The experiments varied the separation distance between the heat sources for three arc current levels at a constant laser power. The second set of experiments analysed the effect of varying laser power for a constant heat source separation distance. The results demonstrate that the distance between the two heat sources significantly affects the cooling rates. The calculated results showed that the hybrid weld pool was very well mixed with strong convection currents resulting from the interaction between the electromagnetic and Marangoni forces. The calculated and experimental results showed that hybrid welding increases the weld pool width and gap bridgability when compared with laser welding. The weld pool depth in hybrid welding was affected mainly by the characteristics of the laser beam. Hybrid weld pool penetration depth is maximised at an optimal distance between the arc electrode and laser beam. The cooling rate increases significantly when the heat sources are separated beyond a critical distance. At close separation between arc and laser, calculations show that the arc radius must be decreased to achieve the observed weld depths. 相似文献
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Modeling the keyhole shape and dimension in plasma arc welding 总被引:1,自引:1,他引:0
It is of great significance to model the keyhole shape and dimensions to optimize the plasma arc welding process parameters. In this study, through employing a combined volumetric heat source mode, the weld pool in keyhole plasma arc welding is determined firstly, and then the dynamic force-balance condition on the interface between the plasma jet and the molten metal is dealt with in describing the keyhole formation inside the weld pool. The effects of welding current on the shape and size of keyhole are numerically analyzed. The sharp transformation from a partial keyhole to a full-penetration keyhole is quantitatively demonstrated. 相似文献
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《中国焊接》2018,(4)
This paper deals with a novel dual shield TIG welding method named gas pool coupled activating TIG( GPCA-TIG)welding. The welding method divides the shielding gas into two layers. Inert gas such as Ar is adopted as the inner layer gas to protect the tungsten electrode and the molten pool metal. Pure O_2,N_2 or mixture of them are used as the outer layer gas to increase the weld penetration and improve the low temperature toughness of weld metal. Through analyzing the interaction between outer gas and arc and the distributions and existing forms of oxygen and nitrogen elements,the transfer behaviors of nitrogen and oxygen from arc to pool were investigated. The results show that,the interaction between the outer gas and arc plasma makes the arc slightly constrict. The incoming oxygen enriches on the molten pool surface and exists in the form of iron oxide,chromium oxide,manganese oxide and silicon oxygen compounds. The incoming nitrogen evenly distributes in the molten pool and exists in the form of nitrogen atom. 相似文献
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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. 相似文献
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薄板TIG 焊时,利用脉动电流引起熔池振荡,当脉动电流与一定尺寸熔池自然振荡频率相同时,则熔池产生谐振,造成电弧长度及电弧电压有较大的往复变化。对电弧电压变动部分进行滤波,放大并用计算机采样,发现当熔池谐振时,电弧电压变动部分达到最大幅值,谐振后幅值很快衰减。本文以熔池谐振信号做为熔透信息进行熔透控制,给出了脉动电流电源,计算机检测系统。研究了熔透信号的变化规律及影响因素,在定点电弧及对接焊时,熔池尺寸与熔池谐振频率有较好的对应关系;以焊接电弧做为传感器,用熔池谐振频率控制熔透及熔池尺寸,有很好的重复性及较高的精度,这对解决熔透闭环自适应控制有很大的实际意义。 相似文献
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空心钨极同轴填丝焊接焊丝与电弧(丝-弧)交互过程是决定焊接质量的关键.首先利用高速摄像观察分析了空心钨极电弧与实心钨极电弧形态,及其对焊缝成形特征的影响规律,然后构建了熔丝过程受力模型,系统分析了同轴填丝焊接过程中熔滴形成及过渡过程动力学特征.结果表明,空心钨极电弧表面辐照区域大于实心钨极,在大电流工艺条件下焊缝成形稳定;熔滴形成阶段,焊丝末端熔滴处于静力平衡状态,在较大表面张力作用下,无法自发从焊丝末端直接过渡进入熔池;熔滴过渡阶段,部分电流从焊丝流过,产生电磁收缩力,引起焊丝与熔池之间的熔滴摆动. 相似文献