冷金属过渡电弧增材制造多道搭接工艺研究

基于冷金属过渡(CMT)电弧增材制造技术,以2319铝合金为堆积材料,恒定送丝速度与不同焊接速度得到6组单层焊道,分别采用标准曲线对单层焊道截面轮廓进行拟合,结果表明抛物线和圆弧曲线的拟合效果均较好。在损失较小模型精度的情况下简化搭接模型,基于抛物线曲线建立单层多道斜顶搭接模型,理论推导最优搭接间距为0.715倍单道宽度。为了验证模型的正确性,采用不同搭接间距成形单层两道进行试验验证,并将其与传统的平顶搭接模型进行对比。试验结果表明斜顶模型更加符合CMT电弧增材制造工艺过程。当搭接间距确定后,研究表明当单层焊道成形高度降低时,搭接表面不平度随之减小,有利于后续多层多道堆积成形。基于优化后的搭接参数,成形多层多道样件,成形形貌良好,三个方向的拉伸力学性能表现出各向异性。     

高氮钢-不锈钢电弧增材制造表面形貌研究

为了对异质材料电弧增材成型的结构机理进行研究,采用机器人电弧增材成型技术,对高氮钢多方式(普通单道、单道多层、多道单层)沉积表面进行分析,筛选最佳工艺参数、焊道间间距,进行电弧交织结构的增材成型。试验结果表明:高氮钢单道焊缝随着沉积速度增大,表面气孔减少;高氮钢多层多道沉积时,送丝速度增大,表面气孔增多;通过最佳焊道间距的预测,得到的过渡层表面平整,表面成形精度达到亚毫米级。     

ER120S-G高强钢电弧增材制造的工艺优化

针对ER120S-G高强钢电弧增材制造搭接间距的工艺优化问题,采用脉冲熔化极气体保护焊(GMAW-P)工艺,对5组单层焊道进行Canny边缘提取和高斯平滑滤波,并选用不同函数对单道形貌进行拟合。比较了常规搭接模型和优化的斜顶搭接模型,并计算出它们的最优搭接间距。研究结果表明,对于高强钢GMAW-P工艺,采用正弦函数拟合焊道边缘的效果最佳,并且采用优化的斜顶搭接模型得到的最优搭接间距为0.66倍的单道宽度。基于上述优化结果试验成形了多层多道块体样件,成形表面质量良好无缺陷,块体组织主要为针状铁素体、粒状贝氏体以及M-A组元等,抗拉强度呈现一定的各向异性。     

GH4169高温合金电弧增材制造焊道成形尺寸预测

采用GH4169高温合金焊丝进行钨极惰性气体保护焊电弧增材制造,采用二次回归通用旋转组合方案建立了焊接电流、焊接速度、送丝速度与单道多层焊道层宽、层高尺寸关系的预测模型,并对计算结果进行了试验验证。结果表明：单道多层焊道层宽和层高预测模型的最大相对误差分别为5.22%,5.82%,表明所建立的预测模型具有较高的可靠性;焊接速度、焊接电流和送丝速度对单道多层焊道成形尺寸的影响是相互耦合的,对单道多层焊道层宽影响最大的因素为焊接电流,对层高影响最大的因素为送丝速度。     

焊接速度对电弧增材熔池流动及焊道形貌影响的数值模拟研究

焊接速度对电弧增材成形过程中传热传质以及焊道成形有重要影响,为探究其影响机理,建立TIG电弧增材成形过程的三维瞬态数值模型,采用VOF方法追踪熔池自由界面,研究不同焊接速度下单道熔积成形过程中的传热及熔池流态,并分析焊接速度对单道焊道形貌的影响。数值模拟结果表明,随着焊接速度减小,熔池的热积累增强,体积增大,熔池表面峰值温度提高,弧坑深度也加深;同时,在电磁力和熔池表面力的共同作用下,熔池表面流速峰值随焊接速度减小而减小,熔池内部流速增大,对流更充分。此外,随着焊接速度减小,成形焊道的宽度和高度均有不同程度的增加。相同条件下的试验与数值模拟的焊道轮廓对比验证了数值模拟结果的有效性,研究结论可为电弧增材技术的工艺参数调控提供理论支撑和依据。     

电弧增材工艺参数对成形质量的影响

基于电弧增材逐层熔覆特性,单焊道成形质量对多层多道堆积成形具有重要影响。本文通过正交试验方法研究了TIG电弧增材技术中工艺参数对焊道余高及熔宽的影响规律,建立了焊道几何尺寸的数学模型。在此基础上进行了单道多层堆积及多道搭接实验,研究了其微观组织及显微硬度。结果表明:单层搭接时道间冷却充分,重叠部位分区明显,焊道两侧硬度大,不完全重结晶区域硬度较低;层间冷却5 s时堆积层分层不明显,顶层为片状组织,中下层大致为等轴晶组织,靠近基板的焊缝区硬度最大。     

冷金属过渡电弧增材制造5183铝合金温度场的数值模拟

利用有限元分析软件ABAQUS使用生死单元法建立冷金属过渡(CMT)电弧增材制造单道10层5183铝合金模型,模拟分析了增材制造过程中温度场的分布和变化规律,并进行试验验证;采用该模拟方法研究了增材制造路径(单向和交叉路径)、层间冷却时间(20,40,60 s)和焊接速度(400,450,500 mm·min^-1)对温度场的影响。结果表明：模拟得到在CMT电弧增材制造过程中基板某点的热循环曲线的变化趋势与试验结果基本一致,且峰值温度和波谷温度与试验结果的相对误差均不大于8.93%,验证了模型的准确性。随着堆焊层数的增加,熔池峰值温度升高,熔池区域变大;单向路径增材制造会在试样收弧端产生较严重的热积累,而交叉路径可以减弱热积累效应;层间冷却时间越长,焊道中点的峰值温度越低,且降低幅度随冷却时间的延长而逐渐减弱;焊道的峰值温度和波谷温度随焊接速度的增加而降低。     

相贯线焊接机器人多层多道焊轨迹规划算法研究

为了提高相贯线焊接机器人埋弧多层多道焊的焊接效率,提出了一套多层多道焊轨迹规划策略。设计出一种焊缝填充方法,即首先确定每层焊缝的高度,根据每条焊道的焊接参数调整焊道宽度;通过对相贯线插补算法的研究,设计出多道焊轨迹规划的算法,即通过改变每条焊道在相贯线插补算法中的半径参数R和r,即可计算出不同焊道相贯线轨迹点坐标。通过MATLAB仿真结果显示,该方法能够满足多层多道焊轨迹规划的要求,为相贯线焊接机器人的运动控制提供了理论基础。     

基于视觉信息融合的熔丝成形制造路径在线识别

在能源装备制造领域大型构件多层多道电弧焊接和航空制造领域重要构件电子束熔丝沉积增材制造过程中,迫切需要路径在线识别及实时自动导引技术。然而在熔丝制造过程中,相邻焊道之间的几何差异很小,传统的结构光焊缝识别技术无法适应。为解决该问题,针对多层多道电弧焊和电子束熔丝沉积增材制造两种场景,分别设计基于双侧定向光影与结构光信息融合的视觉检测装置,并进行成形试验。试验结果表明,将双侧定向光源单独点亮时获得的焊缝灰度图像作差时,焊道边界附近呈现明显的"高灰度-低灰度-高灰度"的过渡区域。时域融合处理可以有效消除弧光、飞溅的干扰。提出的定向光影视觉信息与结构光传感信息实时融合处理方法,较之已有基于线结构光信息的焊道识别和自动跟踪系统在某些场合具有更强适应性,为保证成形质量和提高生产效率提供了新的技术途径。     

中厚板多层多道焊接焊道尺寸与工艺参数相关性研究

以CO₂气体保护焊为基础,利用通用旋转方法设计了熔敷试验,通过试验重点研究分析了中厚板多层多道焊接焊道尺寸与工艺参数之间的相关性,建立了相关性数学模型,并进行了显著性和拟合性验证,获得了通用回归方程,最终绘制出了焊接工艺参数与焊道成型参数的关系曲线图。     

Effect of process parameters and mathematical model for the prediction of bead geometry in pulsed GMA welding

Pulsed gas metal arc welding is one of the most widely used processes in the industry. It offers spray metal transfer at low average currents, high metal deposition rate, versatility, less distortion, and the ability to be used in automated robotic welding systems. The weld bead plays an important role in determining the mechanical properties of the weld. Its geometric parameters, viz., width, reinforcement height, and penetration, are decided according to the welding process parameters, such as wire feed rate, welding speed, pulse current magnitude, frequency (cycle time), etc. Therefore, to produce good weld bead geometry, it is important to set the proper welding process parameters. In the present paper, mathematical models that correlate welding process parameters to weld bead geometry are developed with experimental investigation. Taguchi methods are applied to plan the experiments. Five process parameters, viz., wire feed rate, plate thickness, pulse frequency, pulse current magnitude, and travel speed, are selected to develop the models using multiple regression analysis. The models developed were checked for their adequacy. Results of confirmation experiments show that the models can predict the bead geometry with reasonable accuracy.     

Face milling for hypoid internal bevel gear using new type of tilt milling machine

An hourglass-like heat source model is developed to simulate the geometry of weld beads of laser beam welding. The welding experiments with different welding parameters were carried out to find whether the welds are full-penetrated or not. The laser powers ranged between 1.0 and 5.0 kW with steps of 1.0 kW. Five levels of the welding speed were used: 1.0, 2.0, 3.0, 4.0, and 5.0 m/min. The numerical analysis based on finite element method was used to predict the shape of weld pools during welding. To give a better representation of weld bead, an hourglass-like heat source model is developed to describe the unique shape of 1060 steel weld bead for laser beam welding without filler metal instead of the commonly used conical heat source. Comparing the predicted fusion profile with the experimental cross section of weld, it is found that hourglass-like heat source model is more consistent with the experimental results than the conical heat source for 1060 steel. In addition, the best heat source parameters are obtained by an error analysis. Compared to the experimental results, the simulated results for the welds using Power = 4000 W and Speed = 2.0 m/s and 5000 W and 2.0 m/s match the experimental results well.     

Processing parameter optimization of fiber laser beam welding using an ensemble of metamodels and MOABC

In fiber laser beam welding (LBW), the selection of optimal processing parameters is challenging and plays a key role in improving the bead geometry and welding quality. This study proposes a multi-objective optimization framework by combining an ensemble of metamodels (EMs) with the multi-objective artificial bee colony algorithm (MOABC) to identify the optimal welding parameters. An inverse proportional weighting method that considers the leave-one-out prediction error is presented to construct EM, which incorporates the competitive strengths of three metamodels. EM constructs the correlation between processing parameters (laser power, welding speed, and distance defocus) and bead geometries (bead width, depth of penetration, neck width, and neck depth) with average errors of 10.95%, 7.04%, 7.63%, and 8.62%, respectively. On the basis of EM, MOABC is employed to approximate the Pareto front, and verification experiments show that the relative errors are less than 14.67%. Furthermore, the main effect and the interaction effect of processing parameters on bead geometries are studied. Results demonstrate that the proposed EM-MOABC is effective in guiding actual fiber LBW applications.     

Integrated design and process analysis of a blow molding turbo-charged pipe

These days, the trend in every manufacturing industry including welding is to automate the processes in order to increase productivity. To achieve this objective, it is therefore necessary to make use of models to relate the input parameters with the responses. This paper reports on the applicability of fuzzy logic to predict the weld bead penetration in submerged arc welding process as affected by input welding parameters. Fuzzy logic is a computer technique which allows expressing, evaluating, and simplifying complexities in regard to the relationships in a process by describing the dependencies between output and input parameters in a linguistic form. To develop the fuzzy logic model, the arc voltage, welding current, welding speed, electrode stick-out, and thickness of TiO₂ nanoparticles were taken as the input parameters and the weld bead penetration as the response. In order to generate experimental data, a five-level five-factor rotatable central composite design of experiments was employed. Experiments were performed, and the weld bead penetrations were measured. The predicted results using fuzzy logic were compared with the experimental ones. The correlation coefficient value obtained was 99.99 % between the measured and predicted values of weld bead penetration. The results show that the fuzzy logic is an accurate and reliable technique used in predicting the weld bead penetration due to its low error rate.     

外加磁场对高速GMAW电弧和熔池行为的主动调控效应

在熔化极气体保护焊(Gas metal arc welding,GMAW)过程中,当焊接速度超过临界值后,焊缝成形变差,出现咬边和驼峰焊道,无法满足生产要求。研究证明,熔池中动量很大的后向液体流是产生驼峰焊道的主要原因。自主研发外加磁场发生装置,向熔池施加横向电磁力,对后向液体流进行主动干预,并调控熔池流态,从而抑制驼峰焊道的形成。在Q235低碳钢板上开展焊接工艺试验,获得了不同磁感应强度下的焊缝表面成形;采用高速摄像技术,拍摄焊接过程中的电弧和熔池图像,分析外加磁场对电弧形态、熔池流场和焊缝成形的影响规律,初步揭示外加磁场抑制驼峰焊道的机理。试验结果表明,外加横向磁场能明显调控熔池流态,减小后向液体流的动量,并能有效抑制驼峰焊道和咬边等缺陷,显著改善焊缝成形,提高临界焊接速度。     

Prevention of humping bead associated with high welding speed by double-electrode gas metal arc welding

Manufacturing productivity can be improved by increasing the welding speed. However, humping bead will occur when welding speed is beyond a certain value. An experimental system of double-electrode gas metal arc welding (DE-GMAW) was developed to implement high speed welding and prevent from humping bead formation. The DE-GMAW appropriately partition the heat energy between the wire and the base metal so that higher deposition rate of filler wire and suitable shape and size of weld pool are ensured. The arc images captured during DE-GMAW process were used to optimize the geometric parameters between the gas tungsten arc welding and the gas metal arc welding (GMAW) torches. The main arc and bypass arc integrated well and satisfactory weld bead formation was obtained. Through observing the weld pool behaviors from side view during DE-GMAW process, it was found that the height of both solidified and molten region at the pool tail is almost flat so that no humping bead was formed during DE-GMAW with the welding speed up to 1.7?m/min. The side view images of weld pool in DE-GMAW were compared with those in conventional GMAW, and the reason why DE-GMAW can suppress humping bead is shortly discussed.     

Mathematical models for control of weld bead penetration in the GMAW process

This paper presents the effects of welding process parameters on weld bead penetration for the gas metal arc welding (GMAW) process. Welding process parameters included wire diameter, gas flow rate, welding speed, arc current and welding voltage. The experimental results have shown that weld bead penetration increased as wire diameter, arc current and welding voltage increased, whereas an increase in welding speed was found to decrease the weld bead penetration. However, the weld bead penetration is not affected significantly by gas flow rate changes. Mathematical equations for study of the relationship between welding process parameters and weld bead penetration have also been computed by employing a standard statistical package program, SAS.     

304不锈钢大功率光纤激光焊成形研究

为了研究大功率光纤激光焊在304不锈钢上的焊缝成形,使用5~7kW的激光功率,10~100mm/s的焊接速度在16mm厚的304奥氏体不锈钢上进行全覆盖参数试验。随后观察了焊缝的熔深、熔宽、焊缝形状等成形参数。结果表明,焊接速度低于20mm/s时,焊缝表面会形成隆起,熔深随速度减慢,迅速增加;焊接速度在30~40mm/s时,焊缝表面变得凹凸不平且两边存在咬边,熔深随速度减慢且小幅增加;焊接速度介于50mm/s和90mm/s之间时,焊缝的熔深和熔宽几乎不变;而当速度达到100mm/s时,熔深急剧减小,且钉头形焊缝的形状发生了很大的改变。通过以上试验结果结合小孔效应和熔池特性分析了激光焊缝的成形机理,对大功率光纤激光焊接形成了更全面的认识。     

光纤激光焊接的碳排放建模与多响应评价

全球暖化的背景下,环境影响与制造质量的协同探究成为了研究热点之一。激光焊接广泛应用于汽车、航空航天、轨道交通等制造业,但其碳排放高、能量利用率低。因此,亟需对激光焊接工艺的碳排放特性进行研究,并协同焊接质量展开综合评价。通过搭建激光焊接的碳排放监测平台,分析激光焊接平台各系统(激光发生器、冷水机、机器人、保护气体系统)的碳排放特性,构建激光对接焊的碳排放模型,计算了各系统不同阶段的碳排放占比。采用最优拉丁超立方采样法,开展激光对接焊实验,将拉伸强度和焊缝完整性作为焊接性能的评价指标,分析了激光工艺参数(激光功率、焊接速度、离焦量)对碳排放和焊接性能的影响。实验结果表明,焊接速度对碳排放影响最大,而激光功率对拉伸强度和焊缝完整性的影响最大。对于三个响应指标,激光功率呈正向作用,而焊接速度呈负向作用。根据提出的多响应综合评价方法,对25组激光对接焊的实验结果进行了评分与优劣排序。提出的方法可为激光低碳制造的工程评价提供一定的参考。     

Modeling of multiple characteristics of an arc weld joint

Process parameters modeling have always been one of the key aspects in development of an adaptive control of arc welding process. The welding process parameters are inherently nonlinear, time-delayed, and interdependent, and their on-time adjustment highly influences a sound weld bead formation and process monitoring. During the welding process, parameters control is the primary goal to leads a quality welding. Moreover, the final weld joint behavior, i.e., residual stress, welding strength, and micro-crack formation are generally observed after cooling of the weld product. Thus, it has always been a difficult task to control mechanical properties of a final weld joint. To obtain the best mechanical properties, the final weld joint characteristics needed to be controlled and predicted during the process itself by precise adjustment of the process parameters. The paper presents a neuro-fuzzy modeling approach to provide adaptive control for the automatic process parameter adjustment. Three input parameters wire feed speed, welding gap, and torch speed are modeled with welding current output, providing control over weld bead formation during the welding. The same input process parameters are also modeled to predict final weld joint characteristics, i.e., dilution ratio, hardness of weld bead, hardness of fused zone, and bead width. In order to ascertain the effectiveness of the neuro-fuzzy modeling approach, multiple regression models were also developed to compare the performances.