Molten pool and temperature field in CO2 laser welding

Two measuring methods, high-speed camera and optical monitoring system, were used to study processes of laser welding. Molten pool, cooling time and temperature field were analyzed based on real measured images and optical signal data. The results show that the width of molten pool is almost equal to the width of weld, and length is about 7. 8 mm. The solidification time is about 0. 5 s and the temperature gradient is great, so HAZ is very small. The method and results will be of benefit to build the relationship between welding parameters and microstructure.     

Finite element simulation of three-dimensional temperature field in underwater welding

Mathematical models of three-dimensional temperature fields in underwater welding with moving heat sources are built. Double ellipsoid Gauss model is proposed as heat sources models. Several factors which affect the temperature fields of underwater welding are analyzed. Water has little influence on thermal efftciency. Water convection coefftcient varies with the temperature difference between the water and the workpiece , and water convection makes molten pool freeze quickly. With the increase of water depth, the dimensions of heat sources model should be reduced as arc shrinks. Finite element technology is used to solve mathematical models. ANSYS software is used as finite element tool, and ANSYS Parametric Design Language is used to develop subprograms for loading the moving heat sources and the various convection coefftcients. Experiment results show that computational results by using double ellipsoid Gauss heat sources model accord well with the experimental results.     

Calculation of temperature field near stagnation point in explosive welding

0IntroductionResearch of temperature field near stagnation pointquantificationally is of great importance to control the qual-ity of explosive welding. If the temperature at the weldinginterface is too high the material will melt in excess andthe metal plates can not be welded well and if the tempera-ture is too lowthe plates can not be well-knit. At the sametime to calculate the heat behavior in the flow field of ex-plosive welding quantificationally is the basis to analyze themetallurgic eff…     

Modelling of the plasma-MIG welding temperature field

A three-dimensional simulation model for the plasma-MIG welding process, which takes the interaction between the plasma arc and MIG arc into account, is presented and the quasi-steady temperature fields on the workpiece are calculated with the model. The 10 mm-5A06 aluminum alloy is welded and the temperature fields are measured with the thermoelectric couple. The simulation results and measured results show that the biggest deviation of peak temperature between them is below 20 ℃, which indicates good coincidence between the simulation and measurement.     

Penetration analytical model of three dimensional welding temperature field and experiment rectification

0　ＩｎｔｒｏｄｕｃｔｉｏｎＡｔｐｒｅｓｅｎｔ,ｍｕｃｈａｔｔｅｎｔｉｏｎｗａｓｐａｉｄｔｏｔｈｅｓｔｕｄｙｏｆｔｈｅｐｅｎｅｔｒａｔｉｏｎｃｏｎｔｒｏｌｉｎａｒｃｗｅｌｄｉｎｇ,ａｎｄｍａｎｙｍｅｔｈｏｄｓｗｅｒｅｕｓｅｄｔｏｒｅａｌｉｚｅｒｅａｌｔｉｍｅｃｏｎｔｒｏｌｉｎｔｈｅｗｅｌｄｉｎｇｐｒｏｃｅｓｓ.Ｂｙｍｏｎｉｔｏｒｉｎｇｔｈｅｂａｃｋｉｎｆｏｒｍａｔｉｏｎｏｆｗｅｌｄｔｅｍｐｅｒａｔｕｒｅｆｉｅｌｄ,ｔｈｅｗｅｌｄｐｅｎｅｔｒａｔｉｏｎｃａｎｂｅｃｏｎｔｒｏｌｌｅｄ.Ｉｎａｌｌｔｈｅｐｅ…     

Acquisition and processing of coaxial image of molten pool and keyhole in Nd：YAG laser welding with high power

An experimental setup of acquiring the coaxial visual image of the molten pool and keyhole in high power Nd:YAG laser welding is introduced in this paper. It is one of the most difficult problems in acquiring coaxial image that the coaxial imaging signal of molten pool and keyhole must be separated from the laser beam with high power. This problem was resolved by designing a dichroitic spectroscope. The characteristics of imaging signal were analyzed and the coaxial image of molten pool and keyhole was acquired. A smoothing filter and a homomorphic filter were designed to remove the low frequency noise and to enhance the image according to the characteristics of imaging signal. At last, edges of molten pool and keyhole were detected and extracted based on image segmentation with threshold.     

Numerical simulation of temperature field in multilayer heterogeneity lamination laser soldering

A temperature field numerical simulation is carried out using the finite dement method for laser soldering on PECT (piezoelectric ceramics transformer). A three-dimensional model of laser soldering temperature field of multilayer materials is established. Then, the model was simplified in order to perform an efficient finite dement analysis. Moreover, the temperature distribution characteristic in the laser soldering is investigated and verified by experiments. In all cases, the numerical results are in good agreement with the experimental measurements.     

Numerical simulation of gas metal arc welding temperature field

The infrared camera is used to investigate the temperature field of gas metal arc welding.The results show that the temperature distribution of weld pool and adjacent area appears cone shape.A new heat source model combined by Gaussian distribution heat source of the arc and conical distribution heat source of the droplet is set up based on the experimental results, and with the combined boundary conditions,the temperature field of gas metal arc welding is simulated using finite element method.According to the comparison between the results of experiment and simulation in temperature field shows that the new combined heat source model is more accurate and effective than the Gauss heat source model.     

Relationship between sound signal and weld pool status in plasma arc welding

1　ＩＮＴＲＯＤＵＣＴＩＯＮＰｌａｓｍａａｒｃｗｅｌｄｉｎｇ (ＰＡＷ )ｉｓｃｈａｒａｃｔｅｒｉｚｅｄｂｙｅａｓｙｏｐｅｒａｔｉｏｎａｎｄｌｏｗｃｏｓｔａｍｏｎｇｔｈｅｈｉｇｈ ｅｎｅｒｇｙ ｄｅｎｓｉｔｙ ｂｅａｍ ｐｒｏｃｅｓｓｉｎｇｔｅｃｈｎｉｑｕｅｓ (ｆｏｒｅｘａｍｐｌｅ ,ｅｌｅｃｔｒｏｎｂｅａｍ ,ｌａｓｅｒａｎｄ ｐｌａｓｍａ) .ＰＡＷｉｓｗｉｄｅｌｙｕｓｅｄｉｎｗｅｌｄｉｎｇｏｆｓｔａｉｎｌｅｓｓｓｔｅｅｌ,ｈｉｇｈ ｎｉｃｋｅｌａｌｌｏｙｓ ,ｃａｒｂｏｎｓｔｅｅｌ,ｃｏｐｐｅｒ ,ｃｏｐｐｅｒ …     

Application and prospect of computer technology in welding materials field

0ＩｎｔｒｏｄｕｃｔｉｏｎＷｉｔｈｔｈｅｓｐｒｅａｄａｎｄｄｅｖｅｌｏｐｍｅｎｔｏｆｃｏｍｐｕｔｅｒ,ｔｈｅａｐｐｌｉｃａｔｉｏｎｏｆｃｏｍｐｕｔｅｒｉｎｗｅｌｄｉｎｇｆｉｅｌｄｂｅｃｏｍｅｓｗｉｄｅｓｐｒｅａｄａｎｄｇｏｅｓｉｎｔｏａｌｍｏｓｔｉｔｓａｌｌａｓｐｅｃｔｓ .Ａｃｃｏｒｄｉｎｇｌｙ ,ｈｏｗｔｏａｐｐｌｙＣＡＷｔｅｃｈｎｏｌｏｇｙｔｏｉｍｐｒｏｖｅｗｅｌｄｉｎｇｑｕａｌｉｔｙａｎｄｒａｉｓｅｐｒｏｄｕｃｔｉｖｅｅｆｆｉｃｉｅｎｃｙａｔｔｒａｃｔｍｏｒｅａｎｄｍｏｒｅｗｅｌｄｉｎｇｗｏｒ…     

Numerical analysis of temperature profile and weld dimensions in laser ＋ GMAW hybrid welding of aluminum alloy T-joint

The temperature fields in the transient state and weld dimensions in laser ＋ gas metal arc welding （GMAW） hybrid welding of aluminum alloy T-joint for different welding conditions were calculated using the developed heat source model, and the effect of welding speed on them was analyzed. The results show that the temperature field for the first weld pass only shows the feature of GMAW and the one for the second weld pass has the characteristics of both laser welding and GMAW. Welding speed can affect greatly weld dimensions and temperature distribution. When welding speed reaches 3.5 m/min, the fusion zones of two weld passes are separated and the maximum peak temperature of thermal cycle on the workpiece surface decreases largely.     

Welding mode transition and process stability in high power laser welding

For high-power CO_2 laser welding, besides two well known stable welding processes, i.e. stable deep penetration welding (DPW) and stable heat conduction welding (HCW), the authors have found the third welding process, i.e. unstable-mode welding (UMW) under the certain condition. UMW has its basic feature that the two welding modes (DPW and HCW) appear intermittently, with jumping of penetration depth and weld width between large and small levels. In this paper, effects of welding parameters (focal position, laser power and traveling speed) on laser welding mode and weld appearance have been comprehensively studied Double-U curves of laser welding mode transition have been obtained, which indicate the ranges of the three mentioned welding processes. This work affords science foundation for selecting the welding process parameters correctly and obtaining stable laser welding.     

A phase field investigation of dendrite morphology and solute distributions under transient conditions in an Al–Cu welding molten pool

A quantitative phase field model is developed to simulate dendrite morphology and solute distributions of the Al–4?wt-% Cu alloy in Gas Tungsten Arc Welding (GTAW) welding molten pool under transient conditions. The functions of temperature gradient and travel velocity are used to obtain transient conditions of the welding molten pool. Time evolutions of the dendrite morphology, solute distributions of different positions and interfaces are obtained. The dendrite growth process can be divided into four stages, namely linear growth, non-linear growth, competitive growth and short-term steady growth. The solute concentration near the primary dendrite tip region is the smallest, while solute concentration is larger in the front of plane crystals growth interface and the solute concentration in the liquid region among the primary dendrites is obviously the largest, where the solute segregation forms readily. For the given welding parameters, the dendrite morphology and the initial instability of solid/liquid interface agree well with the experimental result.     

Simulation on temperature field of TIG welding of copper without preheating

1 Introduction Fusion welding of red copper easily leads to many defects, such as backing’s lack of fusion, groove’s hard of through-welding, bad surface forming. All these have relations with thermophysical performances of red copper. The heat conduct…     

Prevention of porosity by oxygen addition in fibre laser and fibre laser–GMA hybrid welding

Prevention of porosity in partial penetration fibre laser and fibre laser–gas metal arc hybrid welding is investigated. It is found that modulation of laser power prevents porosity formation in fibre laser welding, but that this method is not effective in hybrid welding. However, the addition of a small amount of oxygen to the molten pool can prevent porosity formation in both fibre laser and hybrid welding. This is attributed to stabilisation of the keyhole. During welding, oxygen reacts with dissolved carbon to form carbon monoxide (CO) in the keyhole. The CO partial pressure in the keyhole prevents the intense interaction between laser beam and molten metal, thus stabilising the keyhole. The role of CO formation is confirmed by the enhancement of porosity suppression with increased carbon content of the base metal.     

On-line quality inspection in laser blank welding using ART2 neural network

Laser blank welding is becoming more and more important in the automotive industry and the quality of the weld is critical for a successful application.A fully automated solution is required to inspect the quality of the blanks.This paper presents a vision inspection system with a CMOS camera which uses ART2 network to inspect the defects on-line to obtain the geometry and the quality of the weld seam.The neural network ART2 has the capability of self-learning from the environment. It can distinguish the defects that have been learned before and give new outputs for new defects.So ART2 network is suitable for weld quality inspection in laser blank welding.Additionally,a CO_2 laser is used for the blank butt-welding.     

Initial temperature field’s simulation and analysis of 2024 aluminum alloy piate's friction stirring welding

搅拌摩擦焊下压过程中温度场的建立对工件的焊接质量有重要的影响.在搅拌摩擦焊接过程中,搅拌工具与焊接工件的摩擦接触关系及焊接工艺参数的选取,决定了焊接过程中工件的温度场分布.基于修正的库仑摩擦定律,建立了火箭燃料贮箱所用3mm厚2024铝合金材料搅拌摩擦焊接下压过程的热量输入模型,通过有限元分析得到了整个过程中的温度场分布.分析结果表明,该模型的下压阶段温度场计算精度较高.模型的计算结果对指导铝合金焊接初始下压过程中转速、下压速度及项锻力的大小等焊接工艺参数的选取具有重要意义.     

Research and engineering application of the arc welding pulsed controller technology

0IntroductionSubmerged arc welding(SAW)is a welding processwhere the arc burns under flux[1].Automatic SAW hasbeen widely put into practice in the fields of ship-building,energy industry and mechanical engineering for its high ef-ficiency,good quality,flexibility of adjustment and fairlynice working condition.In a word,SAW can carry outwelding of high quality with high current at high speed.High heat input is usually applied for more depositedmetal when SAWis used to weld thick plate.In …     

Relation between welding parameter and acoustic emission information during laser deep penetration welding

In laser non-penetration deep penetration welding process, welding material will vaporize, metal vapor and ambient gas will produce a higher degree ionization, which forms plasma of high concentration. In the case of forming a small hole, plasma will eject .from the hole, and form acoustic emission ( AE ) signals. Because AE information has many advantages such as non-contact measuring, fast response, and high ratio of signal to noise, it can be used as a monitor variable for in-process control. By studying AE information, information of welding pool and small hole can be obtained. According to characteristic of AE information, this paper reveals the correlation between welding parameters and AE signals, and provides a good base for further quality control.