K-TIG焊接研究现状

随着科技的不断进步,锁孔效应钨极氩弧焊(keyhole tungsten inert gas,K-TIG)因其在中厚板焊接中的显著优势,成为现代工业中广泛应用的高效焊接技术之一,在航空航天、核工业、石油化工和船舶制造等对焊接质量要求极高的领域中,应用前景广阔.文中系统回顾了K-TIG焊的发展历程及其在各类材料,如不锈钢、镍合金和钛合金等应用中的现状,同时,智能化焊接技术的发展为K-TIG焊带来了新契机,通过实时监测、自动控制和焊缝跟踪等先进技术,进一步提升了焊接过程的精确性和可靠性,还探讨了熔池熔透识别技术和焊缝跟踪技术的发展现状,这些技术在提高焊接质量和效率方面发挥了重要作用,通过对K-TIG焊的全面分析,旨在为未来的研究提供参考,并为实际应用提供指导.

NUMERICAL ANALYSIS OF THREE-DIMENSIONAL FLUID FLOW AND HEAT TRANSFER IN TIG WELD POOL WITH FULL PENETRATION

A model is established to analyze three-dimensional fluid flow and heat transfer in TICweld pools with full penetration.It considers the deformation of the molten pool surfaceat the condition of full penetrated workpieees,takes the are pressure as the drivingforce of the pool surface deformation,and determines the surface configuration of weldpool based on the dynamic balance of arc pressure,pool gravity and surface tension atdeformed weld pool surface. The SIMPLER algorithm is used to calculate the fluid flowfield and temperature distribution in TIG weld pools of stainless steel workpieces.TIGwelding experiments are made to verify the validity of the model.It shows the calculatedresults by the model are in good agreement with experimental measurements. professor,Dept of Welding Engineering,Harbin Institute of Technology,Harbin 150006,China

Vision-based detection of weld pool width in TIG welding of copper-clad aluminum cable

In order to realize automatic control of the width of weld pool, a visual sensor system for the width of weld pool detection is developed. By initiative arc light, the image of copper plate weld pool is taken back of the torch through the process of weakening and filtering arc light. In order to decrease the time of processing video signals, analog circuit is applied in the processing where video signals is magnified, trimmed and processed into binary on the datum of dynamic average value, therefore the waveform of video signals of weld pool is obtained. The method that is used for detecting the width of weld pool is established. Results show that the vision sensing method for real-time detecting weld pool width to copper-clad aluminum wire TIG welding is feasible. The response cycle of this system is no more than 50 ms, and the testing precision is less than 0. 1 mm.

Numerical analysis for weld pool of pulsed TIG welding

A two-dimensional axisymmetric mathematical model of weld pool of pulsed TIG welding was established. Numerical simulation for weld pool of pulsed TIG welding was done using FLUENT software by selecting the appropriate boundary conditions and strongly coupled control equations. The distributions of temperature field and flow field of weld pool under the periodic change of welding current were obtained. According to the maximum temperature of upper and lower surface of workpiece and depth and width of weld pool, the distributions of temperature field and flow field under different pulsed frequencies and current duty cycles were obtained and periodic variation was analyzed under pulsed current. The analysis results show that with the increase of pulsed frequency, weld pool width increases slightly while depth decreases slightly, and with the increase of current duty cycle, the width and depth of weld pool both increase significantly, and the depth increases greatly.

Numerical simulation on the shape of liquid surface of TIG full-penetrated weld pool

Based on the analysis of the three-dimensional liquid surface behavior of TIG penetrated weld pool,the three-dimensional shape models of weld pool with different values of the back fusion zone radius RB were obtained.The effects of arc on the penetrated weld pool were studied by numerical simulation with finite elements analysis software Surface Evolver.The results show that the size and shape of the back weld pool are not affected obviously by the arc,and the top surface of the weld pool is lowered by arc.From pulse background to pulse peak,the increase of the arc voltage(or the arc light intensity) is due to two factors.One is the increase of the current,and the other is the lowering of the top weld pool surface.

Visual sensing of weld pool in variable polarity TIG welding of aluminium alloy

The passive visual sensing method was successfully applied to monitor the weld pool in TIG welding of aluminium alloy. In order to reduce the disturbance from the arc and acquire clear image, two techniques were used: one was the own-developed computer-controlled variable polarity power(VPP), the other was the composite filter technology. The VPP source did not have high-frequency electromagnetic interference from arc stabilizer in traditional AC welding power, and its output current wave was controlled by computer, so the imaging current and the imaging time could be adjusted easily. Filter spectral window was identified at 650 nm by analyzing the measured arc light spectral distribution. At the end, the high quality and clear images of welding pool of aluminium alloy were successfully acquired at low imaging current.

Modeling transient fluid flow and heat transfer phenothena in stationary pulsed current TIG weld pool

A mathematical model is presented to describe transient behavior of heat transfer and fluid flow in stationary pulsed current tungsten inert gas (PC-TIG) weld pool, which considers three kinds of driving, forces for weld pool convection, i,e. buoyancyforce, electromagnetic force and surface tension force. furthermore. the effect of vaporization heat flux at the free surface of weld pool and the temperature coefficient of surface tenston which is a function of temperatuer and composition are considered in the model In order to accelerate the convergence of iteration the AST(additive source term)method which concerns with the thermal energv boundary conditions is extended successfully to deal with the momentum boundary conditions by which the transient momentum equation and energy equation are mutually coupled. At the same time. ADI (Alternating direction implicit) method and DBC (double blocks correction) technque are employed to solve the finite difference equations. The results of numerical simulation demonstrate the transient behavior of PC-TIG weld pool, as well as the periodic variation of fluid flow and heat transfer with the periodic variation of welding current in stationary PC-TIG weld pool. The theoretical predictions based on this model are, shown to be in good accordance with the experimental measurements.

不锈钢水池热丝TIG自动焊技术的应用

不锈钢水池是储存放射性介质的重要设施。传统工艺采用手工钨极氩弧焊进行不锈钢覆面焊接,存在人员投入大、施工效率低、质量稳定性差等不足。经调研分析,热丝TIG自动焊是在传统TIG焊基础上发展的一种优质、高效、稳定、节能的焊接工艺,结合热丝TIG自动焊工艺特点采取部分加工控制措施可以很好地解决这些问题。通过某项目不锈钢水池热丝TIG自动焊技术的应用,总结分析了热丝TIG自动焊的实施效果,阐述了热丝TIG自动焊技术应用的控制要点。

基于TIG焊电弧-熔池统一模型分析焊接电弧

以TIG焊电弧为研究对象,建立了电弧—熔池的统一模型,并在此模型的基础上对焊接电弧进行了分析。建立此模型就避免了对阳极表面温度的假定,使得对焊接电弧的分析与实际情况更近了一步,从而也为将焊接电弧和熔池作为一个整体来进行分析奠定了基础。采用ANSYS软件分析并得到了阳极表面温度的变化情况,阳极表面电流密度的分布状况,得出热流密度与电流密度分布规律的一致性。并从电磁力和流体流动的角度揭示了电弧压力产生的原因,并通过试验验证了电流密度和电弧压力的分布情况。

表面活性剂对TIG焊电弧现象及焊接熔深的影响

在变动焊接电流下检测电弧电压，考察Ａ－ＴＩＧ焊电弧收缩及活性剂的影响。采取适当的试验方法研究Ａ－ ＴＩＧ焊活性剂对电弧现象及活性剂涂敷量对焊接熔深增加的作用。结果表明，Ａ－ＴＩＧ焊电弧是否产生收缩与所使 用的活性剂有关，即使在电弧未产生收缩情况下，表面活性剂仍然对焊接熔深的增加有较大的作用。

共熔池双TIG焊电弧稳定性研究

分析了共熔池双TIG焊的特点,通过试验,对由各种不同形态的电流组合构成的双弧系统的电弧稳定性进行了研究,探讨了共熔池双TIG焊过程的电弧系统稳定性控制方法。结果表明:通过控制焊接电流的形态及焊接电流值之间的绝对差值,采用双直流电弧、双脉冲电弧或直流与脉冲的混合电流形式都能得到稳定的双弧系统。但在采用较大的双脉冲电流的条件下,脉冲电流之间需存在交错延时,才能保证双弧的稳定性。

气体熔池耦合活性TIG焊方法

提出了一种新型活性TIG焊方法——气体熔池耦合活性TIG焊,即GPCA-TIG焊.该焊接方法将气体分两层流动,内层气体采用惰性气体起到保护熔池的作用;外层气体则为含活性元素O的气体,将活性元素O引入熔池金属,达到增加熔深的目的.文中以SUS304不锈钢为焊接母材,研究了GPCA-TIG焊接法对焊接电弧及焊缝成形的作用,以及该方法主要工艺参数对焊缝熔深和深宽比的影响.结果表明,在相同参数下,与常规TIG焊方法相比,GPCA-TIG焊可不开坡口一次性焊透8 mm不锈钢板,焊接效率明显提高.同时采用该方法,可以有效避免钨极的氧化烧损.

TIG焊熔池表面流动行为的研究

针对钨极惰性气体保护(Tungsten inert gas,TIG)焊熔池表面流动行为,在确定TIG焊熔池表面可采用粒子示踪的方法来进行其表面流动行为示踪的基础上,在以激光为试验背光光源,通过激光在TIG焊熔池表面镜面反射后,使得熔池及示踪粒子清晰成像于成像屏上。在此基础上,开展对304不锈钢和Q235普通碳钢的熔池表面流动行为的试验研究,对所获得这两种材料的TIG焊熔池试验数据进行处理与对比分析,探究熔池表面流动规律。研究结果表明:在TIG焊过程中,其焊接熔池存在两种运动模式,在304不锈钢焊接过程中熔池表面的液态金属由边缘向熔池中心流动;在Q235碳钢焊接过程中熔池表面的液态金属不定向、不规则地由熔池中心向熔池边缘流动,并测量304不锈钢TIG焊过程中熔池表面的液态金属流动速率为12 mm/s左右,Q235碳钢的熔池表面的流动速率为15 mm/s左右。

双层气流保护TIG焊接方法

介绍了一种双层气流保护TIG焊接方法,它适用于TIG焊接过程,解决现有普通TIG焊接熔池深度较浅和混合气体保护下钨极易氧化烧损的问题.该焊接方法将传统单一气体通道的TIG焊枪改造设计为双层气体通道,内层气体为纯惰性气体,保护电极,外层为惰性气体和活性气体的混合气体,向熔池过渡活性组元,改变熔池传热对流模式,增加熔池深度.结果表明,双层气流保护TIG焊接方法可使TIG焊熔池深宽比较普通弧焊深宽比增加2～3倍,同时避免了钨极氧化烧损,延长使用寿命.

氧含量对TIG焊瞬态熔池行为影响的数值分析

建立定点高斯热源作用下TIG熔池的三维瞬态数学模型,考虑焊接熔池内各项散热、焊件内部及表面传热、相变潜热、材料热物理性能参数随温度变化等问题,运用FLUENT软件及其UDF的二次开发功能,模拟不同氧含量对熔池温度场及速度场的影响.结果表明:表面张力温度系数发生转变时的临界温度对熔池温度场和速度场有着决定性影响,该临界温度随氧含量的增加而增加,并且随着氧含量增加逐渐向熔池中心靠近.随着临界温度线的转移,表面张力发生改变,熔池内的Marangoni对流也因此改变,进而使得熔池形貌从低氧含量时浅而宽的形状变成为高氧含量时的深且窄的形状.

钛管高速双枪TIG焊电弧和熔池动态行为的数值模拟

采用高速双枪TIG焊制造钛焊管。建立双钨极、双电弧和熔池耦合数学模型,研究温度场分布、电弧等离子体和熔池液态金属流动以及双枪TIG焊系统能量传输行为。电弧极性相同,在电磁力作用下,前后电极下方的电弧等离子体相向流动。熔池Marangoni力远高于电弧剪切力,是熔池上表面液态金属后向流动的主要驱动力。计算的双钨极电弧热效率为79.8%。高速双枪TIG焊可以提高钛焊管的制造效率和质量。

随焊超声施加方法对铝合金TIG焊缝成形影响

在铝合金TIG焊接的过程中,超声能量处理熔池可以改善焊缝成形、组织与接头力学性能.文中研究了随焊超声施加方法对铝合金TIG焊缝成形的影响,结果表明,连续施加超声会导致熔池熔体飞溅,焊缝成形不佳;间断施加超声可以有效避免熔体飞溅,焊缝成形良好.随焊超声冲击及随焊滚动超声技术均可实现间断施加超声,结果表明,尽管随焊超声冲击使熔宽变小,但是低频冲击作用对TIG焊缝成形具有副作用,会减小熔深.而采用随焊滚动超声技术,可以有效避免低频机械冲击的不利影响,焊缝熔宽变小的同时熔深也增大.

A-TIG焊熔池流体流动形态的测试

为了验证A-TIG焊时的熔池流场计算结果,利用自行研制的活性剂FS12对不锈钢A-TIG焊时熔池流体流动变化进行了测试。利用高熔点双薄钨板挡住熔池流体流动的方法试验,对比焊缝中钨板周围钨颗粒的分布,从而对流体流动的方向进行试验验证。试验结果表明:无活性剂时钨颗粒在焊缝中心浓度比较小,而在焊缝边缘浓度比较大,钨板外侧浓度最大。证实了熔池流体流动是从中心流向边缘。有活性剂时的钨颗粒在焊缝边缘浓度比较小,焊缝中心的浓度比较大,而熔池底部浓度最大。证实了熔池流体流动是从边缘流向中心。通过以上试验说明,活性剂的加入改变了熔池流体流动的方向,使用活性剂FS12后强烈的熔池流体向内对流是A-TIG焊时熔深增加的根本原因。

TIG焊接电弧与熔池统一模型有限元分析

根据磁流体动力学理论以及焊接的实际情况,建立了三维TIG焊接电弧与熔池的统一数学模型,避免了对电弧以及熔池界面条件的假定,使得对焊接电弧与熔池行为的分析与实际情况更近了一步。运用该数学模型对TIG焊接电弧和熔池的流场和热场进行了有限元分析。采用等效比热法来确定液相分数,假定固液相等同区来解决工件熔化区与非熔化区的移动边界。结果表明：用数学模型模拟出的电弧行为特征以及熔池形状与试验结果相吻合。

基于分形和数学形态学的TIG焊熔池图像分析

焊接图像中不可避免地存在烟尘和弧光等干扰造成的噪声,而传统的图像处理方法对噪声非常敏感,因此很难准确地对焊接图像进行处理.文中提出了一种基于分形和数学形态学理论的综合图像处理方法.该方法利用分形理论中的离散分数布朗随机场理论得到按分形维分布的熔池灰度图像,然后利用二值形态学中的连通域检测去除噪声并得到目标图像,进而利用形态学中的开运算和闭运算得到图像的强连通边界.试验结果表明,该方法能够快速、准确地检测熔池的边缘、高度、宽度以及面积等信息.