有色合金A-TIG焊研究现状

电弧热力行为是影响液态金属流动,调控焊接质量的关键要素.利用高速摄像与数值模拟相结合的研究方法,系统分析了空心钨极与实心两种电极特征对电弧热力分布特征的影响.结果表明,焊接电流为350 A时,实心钨极焊缝呈现出深而窄的焊缝成形特征,空心钨极焊缝呈现出浅而宽的焊缝成形特征;距试板表面1 mm,实心钨极与空心钨极电弧沿水平方向的温度场和压力场均呈典型高斯分布特征,中心位置处空心钨极电弧的温度值和压力值分别为实心钨极的61.9%和23.5%;中轴线上实心钨极电弧压力分布呈U形特征,空心钨极电弧压力分布呈N形特征;构建的电弧与熔池强耦合分析模型与实际情况之间具有较好的一致性,可实现对电弧和熔池热力行为的分析与预测.     

Prediction of bead geometry in pulsed GMA welding using back propagation neural network

This paper presents the development of a back propagation neural network model for the prediction of weld bead geometry in pulsed gas metal arc welding process. The model is based on experimental data. The thickness of the plate, pulse frequency, wire feed rate, wire feed rate/travel speed ratio, and peak current have been considered as the input parameters and the bead penetration depth and the convexity index of the bead as output parameters to develop the model. The developed model is then compared with experimental results and it is found that the results obtained from neural network model are accurate in predicting the weld bead geometry.     

Optimization of bead geometry in electron beam welding using a Genetic Algorithm

Bead-on-plate welds were carried out on austenitic stainless steel plates using an electron beam welding machine. Experimental data were collected as per central composite design and regression analysis was conducted to establish input–output relationships of the process. An attempt was made to minimize the weldment area, after satisfying the condition of maximum bead penetration. Thus, it was posed as a constrained optimization problem and solved utilizing a Genetic Algorithm with a penalty function approach. The Genetic Algorithm was able to determine optimal weld-bead geometry and recommend the necessary process parameters for the same.     

Optimization of welding parameters for laser bead-on-plate welding using Taguchi method

This paper presents the results obtained by the optimization of laser bead on plate welding parameters for 3.5 kW cooled slab laser using Taguchi technique. The trials were conducted on two different shielding gases 100% Nitrogen and 50% Nitrogen + 50% Argon. The input process parameters such as beam power, travel speed and focal position are selected suitably in order to obtain the desired output i.e., bead width and depth of penetration. The quality of the weld is evaluated by studying the features of weld bead geometry. Grey relational analysis is applied to optimize the input parameters simultaneously considering multiple output variables. In this investigation the nearest optimal solution which would improve the weld quality was found out. Experimental trial on super austenitic stainless steel has been conducted to validate the optimized parameters. Further, the optimized parameters were evaluated through the microstructural characterization and hardness measurements across the weld zone.     

Optimization of green sand mould system using Taguchi based grey relational analysis

The strength of the mould cavity in sand casting is very much significant to attain high-quality castings. Optimization of green sand process parameters plays a vital role in minimizing casting defects. In the present research work, the effect of process parameters such as AFS grain fineness number, water, molasses, bentonite, fly ash, and ramming, and their levels on the resultant mould properties were investigated and optimized using Taguchi based grey relational analysis. The Taguchi L18 orthogonal array and analysis of variance(ANOVA) were used. The quality characteristics viz., green compression strength, permeability, bulk density, mould hardness and shatter index of green sand mould were optimized using grey relational grade, based on the experiments designed using Taguchi's Design of Experiments. ANOVA analysis indicated that water content is the most influential parameter followed by bentonite, and degree of ramming that contributes to the quality characteristics. The results are confirmed by calculating confidence intervals, which lies within the interval limits. Finally, microstructure observations and X-ray diffraction analysis have been performed for the optimal sand parametric combination. Results show that presence of maximum amount of SiO_2, which might be the reason for enhancement of the physical properties of the sand.     

Sensitivity model for prediction of bead geometry in underwater wet flux cored arc welding

To investigate influence of welding parameters on weld bead geometry in underwater wet flux cored arc welding (FCAW), orthogonal experiments of underwater wet FCAW were conducted in the hyperbaric chamber at water depth from 0.2 m to 60 m and mathematical models were developed by multiple curvilinear regression method from the experimental data. Sensitivity analysis was then performed to predict the bead geometry and evaluate the influence of welding parameters. The results reveal that water depth has a greater influence on bead geometry than other welding parameters when welding at a water depth less than 10 m. At a water depth deeper than 10 m, a change in travel speed affects the bead geometry more strongly than other welding parameters.     

激光-电弧复合焊接头根部特性分析

对厚板HQ785T1低合金高强钢填充HS-70焊丝激光—电弧复合焊接头根部化学成分分析及元素线扫描分析，结果表明，焊缝部位主要元素的含量介于母材和焊丝之间，焊缝从上部到根部，随着深度的增加，焊缝元素组成越接近母材，根部焊缝组成以母材成分为主，焊丝成分所占比例较小；焊缝根部冲击韧性低于焊缝上部, 增大坡口钝边，焊缝根部的冲击韧性降低；金相显示根部焊缝中心组织为粒状贝氏体组织，随着钝边尺寸的增加，碳化物析出量减少，组织略显粗大，组织脆性增加.     

Optimization of submerged arc welding process parameters for overlay welding

In this work, we evaluated the influence of welding variables on weld beads applied by the submerged arc process (SAW) with conventional current, aiming future application in overlays against corrosion. Segments of steel API 5L Gr B pipe as substrate, a 1.13 mm-diameter electrode wire of nickel alloy, classification AWS ERNiCrMo-4 (Hastelloy C-276) as filler metal, and a flux neutral, basic and crowded were used. The variables voltage, wire feed speed and contact tip to work distance (CTWD) were analysed, with the remaining parameters constant by an experimental design with full factorial design in two-level and central points. Statistically significant and predictor mathematical models for response dilution and average current were obtained. However, for the response reinforcement/width, the model was characterized as statistically significant, but not predictive, and containing a lack of fit. The CTWD was the most significant variable reducing the dilution.     

13%Cr不锈钢的激光复合焊工艺

激光-MIG复合电弧焊接工艺综合了激光焊接和电弧焊接的优点,具有低热输入(0.25 kJ/mm)、高焊接速度(55～60 mm/s)、低变形等特点。应用在巴士和卡车底盘的马氏体不锈钢的焊接中取得了很好的效果,通过实验证明,激光-MIG复合焊的焊缝成形良好,接头力学性能、母材疲劳性能优越,其效率是普通MIG焊接的6.5倍。     

中国船舶焊接技术进展

通过焊接热模拟研究了在超大线能量下焊接时Al元素、Mg元素和Ti元素含量对EH36高强船板钢热影响区粗晶区组织、性能的影响规律,采用Thermo-Calc热力学计算与SEM,EDS测试相结合的方法揭示了Al元素、Mg元素和Ti元素含量与母材中氧化物类型、尺寸、数量及粗晶区相变的关系. 结果表明,Al₂O₃无法诱导针状铁素体相变,当Al元素质量分数低于0.005%时,钢中可形成Mg元素、Ti元素或其复合氧化物,可促进粗晶区针状铁素体相变. Mg元素和Ti元素联合添加时,当Mg元素质量分数由0.0042%降低为0.0013%,氧化物类型由MgO转变为Mg₂TiO₄,经统计20个视场内的氧化物数量由408个提高到503个,平均直径由1.37 μm减小到1.10 μm,显著提高了非均匀形核的比表面积,抑制了晶界铁素体的形成,使t_8/5 = 300 s时粗晶区热模拟试样−20 ℃冲击吸收能量由43 J提升到127 J.

     

基于田口试验的轮毂法兰盘热锻工艺优化

采用Deform-3D有限元数值模拟软件对轮毂法兰盘热锻成形进行数值模拟,并对初定成形工艺方案进行分析,确定了预锻+终锻成形方案。针对工件表面应力较大、模具磨损较为严重的问题,通过田口试验优化法对成形参数进行优化组合。模拟结果表明,当轮毂法兰变形温度为1200℃、模具温度为230℃、变形速率为1.0 mm·s~(-1)、摩擦系数为0.05时,工件应力、模具载荷和模具磨损能有效降低,且工件成形质量较优。各参数对零件质量和模具磨损的影响程度依次为:摩擦系数变形速率变形温度模具温度。     

旋转电弧CO2焊接焊缝成形的敏感度分析

在焊接生产中经常遇到需要进行全位置焊接的场合,采用旋转电弧焊接可获得美观的焊缝成形。旋转电弧CO2焊接的参数众多,而且参数组合对焊缝成形的影响很大。在此对旋转电弧实心焊丝CO2仰焊的焊缝成形与焊接参数的关系进行研究,采用敏感度分析技术,研究焊接参数对熔深和熔宽的影响。研究结果表明,旋转直径和焊接速度对熔宽的敏感度的绝对值最大,说明可以通过调节旋转直径和焊接速度来改变熔宽;增大旋转直径和减小焊接速度,熔宽明显增加。旋转频率越高,导电嘴至工件距离(CTWD)越大,则焊缝熔宽越窄。本研究结果对旋转电弧仰焊工艺参数的制定有指导作用。     

异种铝合金自动双丝焊工艺优化

针对厚度为5 mm的6061与5083异种铝合金的焊接,采用自动双丝焊技术,借助Minitab软件分析研究焊接工艺参数对焊接接头强度及成形的影响。依据优化后的焊接工艺参数窗口进行的验证试验,结果显示,采用自动双丝焊技术焊接6061与5083异种铝合金,单面焊双面成形;接头强度达到并超过母材相应标准强度指标要求。与手工TIG双面焊比较,提高焊接效率2倍。     

双细丝埋弧焊+陶瓷衬垫焊接工艺

双细丝埋弧焊+陶瓷衬垫可用于无间隙装配、坡口内定位焊、背面应用陶瓷衬垫+正面大能量输入的双细丝单面埋弧焊焊接,焊缝正反面一次成形.双细丝埋弧焊是利用单电源单送丝机送出两条具有一定距离的并联细丝,在保持大能量输入同时,把焊接电流进行分流,从而降低电弧能量过多集中于中坡口根部的问题.由于细焊丝干伸长度电阻热增加,焊丝熔化速度加快;电极之间电弧辐射热相互作用,能量利用率高,熔滴过渡更细,焊接过程更平稳,焊缝成形更美观;对于板厚12～18 mm,可大幅度提高焊接效率10倍以上,焊接质量稳定,应用前景良好.     

Analysis of keyhole geometry in plasma arc welding

The key problem for numerical simulation of plasma arc welding （PAW） process is to develop a suitable and adaptive volumetric heat source mode which reflects the physical characteristics of keyhole PAW. To this end, the keyhole geometry under different PAW process conditions must be predicted. In this paper, a mathematical model for determining the keyhole shape is developed with considering the mass and momentum conservation of the in-keyhole plasma jet as well as the pressure equilibrium at the plasma jet/liquid metal boundary. A suitable heat source model related to the keyhole shape is applied to the calculation of PAW weld dimensions. The predicted results are in good agreement with the experimental ones.     

电弧弧长对激光-电弧复合焊飞溅和底部驼峰的影响

由于热源形式的特殊性,激光-电弧复合焊接过程中激光和电弧间易发生相互干扰,产生飞溅和底部驼峰等缺陷。以590 MPa级船用高强钢为研究对象,研究了电弧弧长对激光-电弧复合焊飞溅和焊缝底部驼峰的影响。为了深入研究激光-电弧复合焊飞溅和底部驼峰的产生机理,利用高速摄像设备对熔滴过渡行为和焊缝底部熔池进行了观察。结果表明,适当缩短电弧弧长可以降低激光和电弧间的相互干扰,提高复合焊接过程的稳定性,进而降低飞溅产生的倾向。底部驼峰是小孔熔透性差和底部熔池流动不连续所引起的。缩短电弧弧长可以对底部驼峰的产生起到抑制作用,这是因为缩短电弧弧长可以降低等离子体对激光的吸收,提高激光的能量利用率,增加小孔熔透性和稳定性。创新点： 研究了电弧弧长对激光-电弧复合焊飞溅和底部驼峰的影响,采用高速摄像方法对底部熔池流动进行了观察,进一步明确了激光-电弧复合焊接焊缝底部驼峰的产生原因。     

Optimization of arc welding processes using a neural network

X-ray and neutron diffractometric methods are described for the early-stage diagnosis of materials. A comparison is made between traditional and innovative technologies, which aim at being included amongst the NDT methods usable on-site. Emphasis is also placed on the gradual removal from instruments of structural restraints, with a tendency towards anthropomorphic functionalities and flexibility. Prototype production and conceptual schemes are presented and discussed. Conceptual tests, applications and case studies are shown as per the state of the art. Particular reference is made to results obtained from data collected from materials containing welding (e.g. titanium alloys, P22, T92 and P92 steel) and micro- and nano-structural alterations (e.g. ceramics, glass and other materials). These results indicate the meaning and usefulness of the early observation of effects induced in the reticolum of metals by loads, residual stress and structural micro/nano variations. It follows that reticular measurements and the diffractometric methods related to them are onlythose currently available to obtain appropriate early-stage diagnosis. A discussion is provided of photonic (X-ray) and neutronic diffraction with corresponding limits and advantages. The hypothesis of creating a new mobile diagnostic device intended for the application of neutron diffraction is introduced.     

Suppressing of humping bead using an external magnetic field in high-speed gas metal arc welding

During high-speed gas metal arc welding （GMAW）, the backward flowing molten jet with high momentum in the weld pool is considered to be responsible for the occurrence of humping bead. To suppress humping bead, an electromagnetic device is developed and coupled with the welding system. By adjusting the conditions of external magnetic field, forward electromagnetic force is obtained to reduce the momentum of the backward flow of molten metal in weld pool. Consequently, the humping bead can be suppressed by adjusting the external magnetic field. Bead-on-plate welding experiment was conducted on mild steel plates, and the influence of magnetic flux density on the arc deflection angle and weld bead quality is investigated. It is found that external magnetic field can remarkably adjust the momentum of backward flow jet and significantly improve the quality of weld bead.     

基于响应面法的埋弧焊磁控传感器参数优化

为解决磁控埋弧焊传感器焊缝跟踪信号不稳定性、成形质量差等问题,采用BBD(Box-Behnken design)设计试验方案,基于响应面法建立了的埋弧焊焊缝自动跟踪磁控传感器参数(励磁频率、励磁电流、磁极高度、焊接电流)与预测响应值(焊缝跟踪信号、熔宽)的数学模型,并检验数学模型在试验点上的拟合情况,以能够根据跟踪信号质量和焊缝成形的要求优选传感器参数. 并通过优化传感器参数来预测埋弧焊焊缝跟踪信号质量以及焊缝的熔宽,实现跟踪信号与焊缝成形的最佳组合,以提高磁控埋弧焊的焊缝跟踪精度及焊接质量.