基于Fluent的窄间隙TIG焊枪结构优化设计

针对大型工程项目当中的大口径、大厚壁、深窄间隙坡口的管道对接需求,设计了一款窄间隙TIG(NG-TIG)焊枪,并实现高效率焊接。该枪体为非对称的一体化扁平式结构,在间隙宽度为10 mm、深度15 mm的U形坡口内进行焊接试验,发现在窄间隙焊接过程中出现了焊缝成形不连续、焊缝出现气孔及电弧不稳等问题。为了达到理想的焊接工艺效果,文中通过Fluent软件进行了数值模拟仿真分析,对窄间隙TIG焊枪的保护气输送通道及其出口布局进行了结构优化,并且在与传统TIG焊枪的保护气体流量及运动轨迹等方面进行对比后,发现保护气体在钨极周围均匀向外扩散,且速度与传统TIG焊枪的气体保护状态接近,从而确定了窄间隙TIG焊枪的气体保护结构。结果表明,焊枪在焊接电流为120 A,焊接速度为100 mm/min,气体流量在25 L/min的焊接工艺参数下电弧稳定、无飞溅,焊缝成形美观无缺陷。 创新点： (1)通过Fluent软件对传统TIG焊枪的保护气体状态进行了仿真,并作为参照对窄间隙TIG焊枪的送气结构进行了优化设计。(2)窄间隙TIG焊枪既继承了传统TIG的优势,又解决了窄间隙焊接过程中电弧不稳、焊缝出现气孔等常见的问题。(3)通过非填丝和填丝,在坡口内和管壁盖面2种工况下进行了焊接试验,确定了窄间隙TIG焊枪的良好适用性。     

1.5mm镀锌板激光摆动填丝焊接工艺研究

以1.5mm镀锌板为研究对象,为解决镀锌板激光焊接间隙大（0.3mm～1.0mm）和飞溅产生气孔问题,采用摆动填丝进行焊接,通过改变激光功率、送丝速度、摆动速度、摆动直径等影响因素进行激光填丝焊接试验,探究出最优镀锌板激光摆动填丝焊接工艺参数。结果表明,与传统的接焊相比,激光摆动填丝焊有利于减少焊缝中气孔的生成,解决了激光焊接对镀锌板苛刻的间隙要求。     

车用薄镀锌板CMT搭接工艺特性

针对车用薄镀锌板材料,为了进一步降低冷金属过渡(cold metal transfer,CMT)时产生的飞溅,研究分析了薄镀锌板CMT搭接焊接工艺特性.采用Baumer HX 13工业级高速摄像机拍摄了CMT焊接熔滴过渡图像,利用NI PXI数据采集系统采集了CMT焊接电流电压信号.主要研究了短路前期阶段与短路后期阶段电流电压对CMT熔滴过渡的影响规律,同时分析了焊枪倾角对薄镀锌板CMT搭接焊接熔滴过渡行为的影响.结果表明,当CMT短路阶段电流小于基值阶段电流时,电信号波形未出现扰动现象,焊接过程稳定;当降低短路后期电流约5 A时,能够有效降低CMT搭接产生的飞溅;当焊枪与垂直平面呈30°夹角时,能够获得平稳的熔滴过渡,焊接飞溅最小,焊缝熔深最大,焊缝成形最佳.故短路阶段电流小于基值阶段电流且降低短路后期电流约5 A时,采用焊枪倾角30°的焊接工艺能够实现较小的焊接飞溅,为生产实践提供理论依据.     

三丝GMAW横焊工艺优化研究

利用实验室搭建的三丝焊设备,通过对电弧电压、焊接电流、焊接速度、保护气体流量和焊枪倾角的控制和调节,选定三丝横焊高效且保证质量的焊接工艺参数组合。结果表明:焊枪倾角影响焊缝的成形,3支焊枪需要合理布置以保证焊接质量。随着焊接电流的增大,焊缝余高先减小后增大,但过大的焊接电流会导致焊缝下塌,同时,飞溅明显增大;随着电弧电压的升高,焊缝余高变小。最终经过优化得出工艺参数组合:辅助焊枪与水平面的夹角呈30°,焊接电流为I1=140 A,I2=155 A,I3=140 A,电弧电压为U1=22 V,U2=21 V和U3=22 V,焊接速度为2.25 m/min,保护气体流量为20 L/min,焊丝伸出长L1=L2=L3=20 mm。对焊缝的显微组织进行分析,发现焊缝中存在粗晶区,说明焊接过程中热输入很大。进行硬度测试,发现焊缝硬度明显提高,这是因为焊缝中产生了魏氏组织。     

水下局部干法CO_2自动焊接工艺参数对焊缝成形规律的研究

采用水下局部干法CO2自动焊焊接方法对16 mm厚16Mn钢进行平板堆焊试验,分析研究了电弧电压、焊接电流、焊接速度和焊枪倾角4个焊接工艺参数对焊缝成形的影响规律。结果表明,水下局部干法CO2自动焊的熔深主要取决于焊接电流,电弧电压及焊接速度对其影响不大;焊接速度对余高影响不大。前倾焊时,熔深小,焊道平而宽,焊缝美观,容易观察焊道,气体保护效果好;后倾焊反之。     

基于气泡浮出速度理论的CO2气体保护焊焊缝中气孔倾向探讨

CO2气体保护焊焊缝中气孔类型可以归纳为两大类(冶金反应型和析出型),气孔的性质分别为CO气孔、氢气孔及氮气孔.气孔的形成由气泡生核、长大、逸出三个阶段组成.CO2气体保护焊对气孔的敏感性是该工艺方法冶金特性所决定的.在工艺影响因素中,对气孔倾向影响较大的主要是焊接电流、电弧电压、气体流量、电源极性及焊接速度."焊接飞...     

CO_2气体保护焊接操作方法上的几个问题

一、施焊方向问题使用 CO_2半自动焊接一般多习惯采用左焊法(右手持焊枪)。焊枪向施焊方向相反的一方倾斜。这就形成了:向前推着焊,保护气体向前吹的现象。如图:这种焊法,明显减弱了对熔池后部,半液态金属的气体保护作用。操作者一旦掌握不好,就会造成蜂窝状气孔或面包形焊缝。在水平位置,坡口焊缝焊接时尤为严重。     

焊接设备——熔焊设备

大功率、低噪声的系列TIG弧焊机；用三相交流电流工作的TIG弧焊机；用于大型钢结构工作中的熔化极惰性／活性气体保护焊焊机；焊剂带约束电弧超窄间隙焊接的实现；高性能焊枪[编者按]     

搭接接头CO2焊防止气孔的试验研究

针对搭接接头C02气体保护焊出现的气孔问题，首先分析了C02焊易产生气孔的气体，同时确定了搭接接头间隙大小和焊接位置对产生气孔倾向进行了研究，找到了产生气孔的原因，并确定了搭接接头C02焊防止气孔的措施。     

K-TIG焊接电弧特性的数值分析

以K-TIG焊枪为研究对象,根据磁流体动力学理论建立了电弧的三维有限元数学模型,利用FLUENT软件对K-TIG焊枪内部保护气体和焊接电弧进行了数值模拟,获得大电流焊接时的温度分布、电势分布、电弧压力及等离子体速度场分布.模拟结果可以用于指导K-TIG大电流焊枪设计、焊接过程控制及焊缝质量评价等.     

CO2气体保护的激光焊接12mm厚低碳钢板

采用CO2 作为保护气体消除大熔深激光焊接低碳钢时易发生的气孔问题 ,并对比研究了CO2 和Ar气保护条件下 12mm厚低碳钢板激光焊缝的组织和韧性。焊接试验利用 4kWNd :YAG激光器 ,采用双面深熔焊的方法 ,焊接条件为 4kW激光功率和0 .3 ,0 .5m/min的焊接速度。冲击试验采用一种自行设计的带侧面缺口的三缺口冲击试样 ,以保证断裂全部发生在焊缝。结果表明 ,利用CO2 作保护气体焊接低碳钢板 ,可以有效消除大熔深激光焊接时的气孔问题 ,并获得比Ar气保护下硬度较低 ,冲击韧性高的焊缝。研究工作为解决大功率激光深熔焊时容易发生的气孔问题提供了一条有效途径     

双层气体保护焊炬的试验研究

本文对新型双层气体保护焊炬的设计及气体保护性能进行了试验。结果表明,“三水内冷”的双层气体保护焊炬,具有良好的气体保护性能和防止因长时间使用飞溅积聚破坏双层气体保护的效能。内层气流的间隙效应的良好作用为应用挡气板解决平板堆焊及坡口表面焊道焊接时气体保护问题,提供了可能性。     

环保焊枪吸烟对小电流CO2气体保护电弧焊的影响

采用环保焊枪进行了小电流二氧化碳气体保护电弧焊平焊位置焊接,通过分析焊接过程中电弧形貌、电流电压和熔滴过渡方式变化以及焊缝成形、焊缝金属拉伸力学性能和X射线探伤结果,评估了吸烟功率变化时的吸烟效果以及吸烟行为对于焊接过程和焊缝质量的影响规律. 结果表明,使用环保焊枪可以显著降低小电流二氧化碳气体保护电弧焊时飘散在周围空间中的焊接烟尘. 吸烟过程虽然使得短路过渡熔滴频率略有增加,悬挂熔滴和电弧的稳定性略为变差,但对焊缝成形和焊接缺陷都无影响,焊缝金属屈服强度略有减小,抗拉强度略有增加.     

Development of adaptive control system for alternating current pulsed metal inert gas welding parameters

Abstract

A three-dimensional laser sensor is combined with an alternating current pulsed metal inert gas welding robot system to detect information about the variation of joint gap width and deviation of the joint position relative to the welding torch. Together with the joint tracking and torch direction adjustment, electrode negative polarity ratio and welding speed are also controlled adaptively according to the variation of joint gap width during welding. As a result, a high tolerance of joint gap variation is obtained and bead shape becomes more uniform and of reasonable quality in welding of aluminium alloy sheets.     

Effects of shielding gas composition on arc characteristics and droplet transfer in tandem narrow gap GMA welding

The effects of shielding gas composition in tandem narrow gap gas metal arc welding were studied. The shielding gas included argon, carbon dioxide and helium. The arc characteristics and droplet transfer process were analysed. The results show that in the same welding parameters, the trail wire welding current is higher than the lead wire welding current. With the increase of carbon dioxide content, the welding currents of two wires decrease, and the trail wire droplet transfer mode transforms from spray transfer to projected transfer. With the increase of helium content, the welding currents increase and the lead wire droplet transfer mode transforms from projected transfer to spray transfer. The weld width is the largest when the shielding gas mixture is 80%Ar10%CO₂10%He.     

CO_2激光焊接600MPa DP钢接头组织与性能

采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降.     

氮氧联合过渡对GPCA-TIG焊焊缝的影响

针对外层引入氮氧混合气体的气体熔池耦合活性TIG焊,通过改变焊枪内外喷嘴的相对位置,分别研究了外层气体与熔池表面的耦合程度不同时焊缝成形、焊缝中氮氧含量及焊缝组织性能的变化规律.结果表明,氮氧联合过渡时气体熔池耦合活性TIG焊焊缝窄而深;低温冲击韧性高于母材及传统TIG焊的7.5%以上,而抗拉强度和屈服强度均略低于母材;焊缝组织晶粒细小,奥氏体上沿晶界分布着少量铁素体.气体熔池耦合活性TIG焊焊缝中的氮氧含量可以通过调节焊枪内外喷嘴的相对位置进行微量控制.     

An optical sensing system for seam tracking and weld pool control in gas metal arc welding of steel pipe

A visual sensing system was developed for automatic gas metal arc welding (GMAW) of the root pass of steel pipe. The system consisted of a vision sensor that consisted of a charge-coupled device (CCD) camera and lenses, a frame grabber, image processing algorithms, and a computer controller. A specially designed five-axis manipulator was used to position the welding torch and to provide the vision sensor with automatic access to view the welding position. During the root pass welding, an image of the weld pool and its vicinity was captured using the camera without interference of the intensive arc light by viewing at the instance of a short-circuit of the welding power. The captured image was then processed to recognize the weld pool shape. For seam tracking, the manipulator was used to adjust the torch position based upon the pool image to the groove center. The measured gap size was used to determine the appropriate welding conditions to obtain sound penetration. The welding speed was chosen using fuzzy logic with the knowledge of a skilled welder and measured gap. The automatic welding equipment demonstrated that both welding conditions and torch position could be appropriately controlled to obtain a sound weldment and a good seam tracking capability.     

Effects of absorptivity,shielding gas speed,and contact media on sheet metal laser welding

Abstract

A three-dimensional quasi-steady state heat conduction model is developed for laser welding of sheet metals. The heat flux at the surface of the workpiece is considered to be due to a moving Gaussian laser beam. An analytical expression is obtained for the temperature distribution by solving the conduction problem using the Fourier integral transform technique. This expression is used to locate the melting temperature isotherm, and thereby determine the weld depth and width. Experimental and theoretical results for the weld depths and widths are illustrated for different welding parameters such as the laser power, absorptivity, welding speed, and shielding gas speed. The theory and experiment are found to agree reasonably well. The effects of absorptivity, shielding gas speed, and heat loss due to different contact media at the bottom surface of the workpiece are also investigated, and are found to be significant for thin metal laser welding.     

Effects of shielding gases on the microstructure and localized corrosion of tube-to-tube sheet welds of super austenitic stainless steel for seawater cooled condenser

The effects of shielding gas on the microstructure and localized corrosion of tube-to-tube sheet welds of SR-50A super austenitic stainless steel for seawater cooled condense were investigated in highly concentrated chloride environments. The localized corrosion resistance of the weld metal after welding with an Ar shielding gas supplemented with N₂ increased due to a decrease in the pitting resistance equivalent number (PREN) difference between the PREN_IR of interdendritic region and the PREN_DC of dendrite core. The localized corrosion was selectively initiated at the dendrite core because the PREN of the dendrite core was smaller than that of the interdendritic region.