Quantitative research on the heat affected zone of weave bead welding for Invar alloy

Quantitative research on the heat affected zone （ HAZ） o f weave bead welding （ WBW） joint fo r Invar alloy is carried out in this paper. Based on the morphology and related data analysis of the weld seam, the width difference o f each layer and the forming mechanism are analyzed. Results show that the bottom layer （ Layer 1 ） has the widest HAZ and the smallest fluctuation, which reaches 1 200 ｜jLm. HAZ width o f layer 2 to 5 is relatively narrower which is basically below 600 jjim, while the amplitude fluctuation is greater. The main reason lies in the welding path. The long straight welding without weave causes the base metal near the groove fully melts which causes by the long straight welding without weave, while welding with weave leads to the uneven and inadequate melting of metal near groove.

Analysis of microstructure and performance of temper bead welded joints for SA508-3 steel by Quenching and Tempering mode

The HAZ microstructure and performance of Quenching and Tempering mode temper bead welding and general welded joints which were made on SA508-3 steel of 60 mm thickness were compared in this article. The result shows that tempering sorbite which has excellent overall performance was obtained in both modes. The microstructure of Quenching and Tempering mode welded joints got more fine grain. Even though the hardness of tempering bead welded joints is higher than the general one,it still meets the standards which is lower than 350 HV. The impact absorbing energy of each district of tempering bead welded joints HAZ reached 170 J,which is equal to general one.

Effect of Welding Parameters on Dilution and Weld Bead Geometry in Cladding

The effect of pulsed gas metal arc welding （GMAW） variables on the dilution and weld bead geometry in cladding X65 pipeline steel with 316L stainless steel was studied. Using a full factorial method, a series of experiments were carried out to know the effect of wire feed rate, welding speed, distance between gas nozzle and plate, and the vertical angle of welding on dilution and weld bead geometry. The findings indicate that the dilution of weld metal and its dimension i.e. width, height and depth increase with the feed rate, but the contact angle of the bead decreases first and then increases. Meantime, welding speed has an opposite effect except for dilution. There is an interaction effect between welding parameters at the contact angle. The results also show forehand welding or decreasing electrode extension decrease the angle of contact. Finally, a mathematical model is contrived to highlight the relationship between welding variables with dilution and weld bead geometry.

Welding Polarity Effects on Weld Spatters and Bead Geometry of Hyperbaric Dry GMAW

Welding polarity has influence on welding stability to some extent, but the specific relationship between welding polarity and weld quality has not been found, especially under the hyperbaric environment. Based on a hyperbaric dry welding experiment system, gas metal arc welding（GMAW） experiments with direct current electrode positive（DCEP） and direct current electrode negative（DCEN） operations are carried out under the ambient pressures of 0.1 MPa, 0.4 MPa, 0.7 MPa and 1.0 MPa to find the influence rule of different welding polarities on welding spatters and weld bead geometry. The effects of welding polarities on the weld bead geometry such as the reinforcement, the weld width and the penetration are discussed. The experimental results show that the welding spatters gradually grow in quantity and size for GMAW with DCEP, while GMAW with DCEN can produce fewer spatters comparatively with the increase of the ambient pressure. Compared with DCEP, the welding current and arc voltage waveforms for DCEN is more stable and the distribution of welding current probability density for DCEN is more concentrated under the hyperbaric environment. When the ambient pressure is increased from 0.1 MPa to 1.0 MPa, the effects of welding polarities on the reinforcement, the weld width and the penetration are as follows： an increase of 0.8 mm for the weld reinforcement is produced by GMAW with DCEN and 1.3 mm by GMAW with DCEP, a decrease of 7.2 mm for the weld width is produced by DCEN and 6.1 mm by DCEP; and an increase of 3.9 mm for the penetration is produced by DCEN and 1.9 mm by DCEP. The proposed research indicates that the desirable stability in the welding procedure can be achieved by GMAW with DCEN operation under the hyperbaric environment.

Effect of welding current and speed on occurrence of humping bead in high-speed GMAW

The developed mathematical model of humping formation mechanism in high-speed gas metal arc welding （GMAW） is used to analyze the effects of welding current and welding speed on the occurrence of humping bead. It considers both the momentum and heat content of backward flowing molten jet inside weld pool. Three-dimensional geometry of weld pool, the spacing between two adjacent humps and hump height along humping weld bead are calculated under different levels of welding current and welding speed. It shows that wire feeding rate, power intensity and the moment of backward flowing molten jet are the major factors on humping bead formation.

Process parameters-weld bead geometry interactions and their influence on mechanical properties:A case of dissimilar aluminium alloy electron beam welds

Prediction of weld bead geometry is always an interesting and challenging research topic as it involves understanding of complex multi input and multi output system. The weld bead geometry has a profound impact on the load bearing capability of a weld joint, which in-turn decides the performance in real time service conditions. The present study introduces a novel approach of detecting a relationship between weld bead geometry and mechanical properties(e.g. tensile load) for the purpose of catering the best the process could offer. The significance of the proposed approach is demonstrated by a case of dissimilar aluminium alloy(AA2219 and AA5083) electron beam welds. A mathematical model of tensile braking load as a function of geometrical attributes of weld bead geometry is presented. The results of investigation suggests the effective thickness of weld-a geometric parameter of weld bead has the most significant influence on tensile breaking load of dissimilar weld joint. The observations on bead geometry and the mechanical properties(microhardness, ultimate tensile load and face bend angle) are correlated with detailed metallurgical analysis. The fusion zone of dissimilar electron beam weld has finer grain size with a moderate evaporation and segregation of alloying elements magnesium and copper respectively.The mechanical properties of weld joint are controlled by optimum bead geometry and HAZ softening in weaker AA5083 Al alloy.

A Three-Dimensional Numerical Model for Predicting the Weld Bead Geometry Characteristics in Laser Overlap Welding of Low Carbon Galvanized Steel

Laser welding (LW) becomes one of the most economical high quality joining processes. LW offers the advantage of very controlled heat input resulting in low distortion and the ability to weld heat sensitive components. To exploit efficiently the benefits presented by LW, it is necessary to develop an integrated approach to identify and control the welding process variables in order to produce the desired weld characteristics without being forced to use the traditional and fastidious trial and error procedures. The paper presents a study of weld bead geometry characteristics prediction for laser overlap welding of low carbon galvanized steel using 3D numerical modelling and experimental validation. The temperature dependent material properties, metallurgical transformations and enthalpy method constitute the foundation of the proposed modelling approach. An adaptive 3D heat source is adopted to simulate both keyhole and conduction mode of the LW process. The simulations are performed using 3D finite element model on commercial software. The model is used to estimate the weld bead geometry characteristics for various LW parameters, such as laser power, welding speed and laser beam diameter. The calibration and validation of the 3D numerical model are based on experimental data achieved using a 3 kW Nd:Yag laser system, a structured experimental design and confirmed statistical analysis tools. The results reveal that the modelling approach can provide not only a consistent and accurate prediction of the weld characteristics under variable welding parameters and conditions but also a comprehensive and quantitative analysis of process parameters effects on the weld quality. The results show great concordance between predicted and measured values for weld bead geometry characteristics, such as depth of penetration, bead width at the top surface and bead width at the interface between sheets, with an average accuracy greater than 95%.

FUZZY REGRESSION MODEL TO PREDICT THE BEAD GEOMETRY IN THE ROBOTIC WELDING PROCESS

Recently, there has been a rapid development in computer technology, which has in turn led to develop the fully robotic welding system using artificial intelligence （AI） technology. However, the robotic welding system has not been achieved due to difficulties of the mathematical model and sensor technologies. The possibilities of the fuzzy regression method to predict the bead geometry, such as bead width, bead height, bead penetration and bead area in the robotic GMA （gas metal arc） welding process is presented. The approach, a well-known method to deal with the problems with a high degree of fuzziness, is used to build the relationship between four process variables and the four quality characteristics, respectively. Using these models, the proper prediction of the process variables for obtaining the optimal bead geometry can be determined.

Effect of FCAW Process Parameters on Weld Bead Geometry in Stainless Steel Cladding

Recently automated and / or robotic welding systems have received a great deal of attention because they are highly suitable not only to enhance production rate and quality, but also to decrease cost and time to manufacture for a given product. To get the desired quality welds it is essential to have complete control over the relevant process parameters in order to obtain the required bead geometry. Mathematical models need to be developed to have such control and to make effective use of automated and / or robotic arc welding process.

Evaluation of Geometric Quality of Weld Beads in the Joining of Carbon Steel Pipelines with Single Pass

This work presents the uncertainty evaluation associated with the measurement of linear parameters that define the weld geometry, specifically the width, using a profile projector, in order to meet the current technical standards. The following steps were proposed and implemented: identification of linear parameters that define the weld geometry;identification and study of variables that affect the measurement of these parameters;the adoption of the mathematical model to estimate the uncertainty;planning and execution of experiments for data collection, calculation of uncertainty and, finally, analysis and discussion of the results. Through the results analysis it was concluded that the weld in overhead position produces the lowest front bead width values and the vertical weld produces the largest width values. The expanded uncertainty values were between 0.016 mm and 0.075 mm for all measurements, and the overhead position showed, on average, the highest values.

Optimization of back bead geometry in the PMAG-TIG twin arc hybrid root welding process using grey based Taguchi method

This study investigated multi-response optimization of the pulse metal active gas-tungsten inert gas( PMAG-TIG) twin arc hybrid root welding process for an optimal parametric combination to yield favorable back bead geometry of welded joints using grey relational analysis and Taguchi method.Eighteen experimental runs based on an orthogonal array following the Taguchi method were performed to derive objective functions to be optimized within the experimental domain.The objective functions were selected in relation to parameters of PMAG-TIG twin arc root welding back bead geometry: back bead width to root reinforcement ratio and deposited metal height.The Taguchi approach was followed by grey relational analysis to solve the multi-response optimization problem.The significance of factors on overall quality characteristics of the weld joint was also evaluated quantitatively using analysis of variance.Optimal results were verified through additional experiments,and showed to feasibility of applying grey relation analysis in combination with Taguchi technique for continuous improvement of product quality in the manufacturing industry.

铸造低合金钢回火焊道技术适用性判别分析

回火焊道技术是通过第二层焊道的热循环来改善第一层焊道的组织和性能的焊接技术,但目前尚无明确标准规定其适用范围。以A217 WC6和A217 WC9钢为对象,采用Gleeble热模拟试验判断二次回火对两种铸造低合金钢性能的影响规律,进而用回火焊道技术制造焊接试样,进行焊态、热处理态下的组织和性能对比试验。试验结果表明,A217 WC6钢在一次高温热循环后,冲击功从70 J提升至126 J,硬度值从154 HV10增至375 HV10。二次热循环后,A217 WC6钢的硬度整体降低,回火峰值温度对其性能有显著影响。相比之下,A217 WC9钢的冲击功从77 J降至52 J,硬度值从182 HV10增至364 HV10,二次热循环对其性能影响不显著。焊接试样的性能和硬度变化趋势与Gleeble热模拟试验一致。由此得到结论:Gleeble热模拟试验可以判断钢种是否适用于回火焊道技术;A217 WC6钢较A217 WC9钢更适合采用回火焊道技术进行修复。

基于摆动激光扫描的GMAW焊缝成形调控

将摆动激光与GMAW工艺复合,利用“8”字形摆动激光扫描液态熔池,对其温度场和流场进行调控,以改变熔池温度梯度,主动调控熔池流动以改善焊缝成形.在6061铝合金板材表面进行堆焊试验,重点探究了光丝间距、摆动幅度、激光功率对于焊缝成形的影响,采用高速摄像机拍摄激光扫描熔池过程.结果表明,摆动激光扫描可以有效抑制成形缺陷的发生,当摆动激光扫描熔池中部时可以获得最佳的焊缝成形效果.摆动激光扫描降低了熔池温度梯度分布,同时激光扫描产生的激光蒸发反力可以驱动熔池流动,促进了液态熔池的流动铺展,从而有效抑制了不规则焊缝成形缺陷,减少焊缝内部气孔和裂纹缺陷.调节摆动激光摆幅可以在一定范围内对焊缝宽度进行调控.

铸造低合金钢回火焊道与焊后热处理焊接接头性能对比研究

为评估回火焊道工艺在铸造低合金钢焊接中的应用效果,研究回火焊道工艺能否替代传统的焊后热处理工艺。采用焊条电弧焊(SMAW),选用R307、R407焊条分别对A217 WC6和A217 WC9进行焊接。控制预热温度、电流、电压、搭接率和层厚,以实现回火焊道工艺。焊后对接头进行金相、硬度、拉伸、冲击和侧弯试验。试验结果表明,A217 WC6焊接接头在焊态和热处理态下的性能均满足标准要求,而A217 WC9焊接接头在焊态下的冲击功小于母材,侧弯试样在熔合线附近出现表面裂纹,且硬度明显高于热处理态。分析表明,回火焊道工艺能有效改善A217 WC6钢焊接接头的组织和性能,可替代焊后热处理。但在A217 WC9钢的焊接中,回火焊道工艺未能达到改善组织和性能的目的,焊接接头性能不满足标准要求,不能替代传统的焊后热处理工艺。

基于虚拟现实的立管横焊机器人辅助焊接工艺设计与实现

焊接工艺参数的选择对焊接质量有重要影响。针对立管J型铺设窄坡口横焊熔池下淌特性,提出基于横焊焊道厚度及热输入恒定策略的焊接工艺参数匹配算法。基于Unity3D开发平台和工艺参数匹配算法,通过C#开发了立管横焊CAPP模块,扩展了虚拟现实人机交互系统的功能模块;开展立管横焊计算机辅助焊接工艺实验,焊后焊缝成形良好,无焊接缺陷。实验结果表明:CAPP模块可有效获取匹配的焊接工艺参数,能缩短焊接工艺开发周期,降低工艺开发成本,有效提升系统的智能化水平。

基于BAS算法优化的电弧增材制造焊道尺寸预测

目的为提高实际应用中电弧增材制造对工艺参数的选取效率及成形形貌的控制效果,建立高效且精准的成形尺寸预测模型,实现对焊道尺寸的合理预测。方法在单层单道CMT电弧增材制造实验的基础上,建立基于天牛须搜索算法(Beetle Antennae Search,BAS)优化BP神经网络的焊道尺寸预测模型,利用BAS算法实现对BP神经网络初始权值和阈值的优化,可以实现预测不同工艺参数(焊接速度、送丝速度、干伸长)下焊道的成形尺寸(熔宽、余高)。利用试验验证BAS-BP预测模型的性能,与现有模型进行对比,结果结果表明该模型具有较高精度的预测效果,能够有效映射工艺参数与焊道尺寸之间的非线性关系,印证了该模型具有良好的拟合和泛化能力,同时其对焊道熔宽和余高的预测误差分别不超过0.2、0.12 mm,预测平均误差率均不超过6%,相对于其他预测模型表现出较好的准确性和稳定性。结论BAS-BP神经网络预测模型的输出误差较小,网络训练收敛速度加快,避免了过拟合及欠拟合的风险,有效提高了预测模型的泛化能力和预测精度,可以实现一定工艺参数范围内的焊道尺寸预测,为后续电弧增材的实时预测及控制参数应用提供了技术支持。

自适应分流交替电弧WAAM电弧行为与熔滴过渡

传统电弧由于热输入高、熔覆率低,无法直接应用于电弧熔丝增材制造(wire and arc additive manufacturing,WAAM)技术.该文提出极性变换自适应分流交替电弧WAAM工艺方法,在钨电极,工件和丝材间形成交替电弧.根据EN/EP电流转换时自适应分流并主动诱导交替电弧形成.该新型热源能满足以丝材阳极-钨电极阴极的EN电弧熔化丝材;以钨电极阳极-工件阴极的EP电弧清理工件,并通过适当的调节实现电弧热质力传输的受控解耦.验证了该新型热源的适用性,并对比分析了焊接速度和丝材高度下对电弧行为及熔滴过渡的影响.结果表明,当焊接速度为5.7 mm/s和丝材高度为8 mm时,沉积层形貌较好且熔滴过渡规律;与传统变极性等离子电弧(variable polarity plasma arc,VPPA)熔丝增材制造技术相比,其自适应分流交替电弧显著提高了丝材的沉积效率且降低了母材热输入,较好的兼顾了增材质量与增材效率.

基于二次通用旋转组合设计的冷金属过渡电弧增材制造AZ31镁合金焊道截面尺寸研究

基于冷金属过渡的电弧增材制造技术制备了AZ31镁合金单道试样,测试了单道试样的焊道宽度和焊道高度。根据二次通用旋转组合试验设计与二次多项式逐步回归分析,建立了高度显著的焊道宽度和焊道高度与摆动宽度、焊接速度、送丝速度和基板温度等工艺参数间的关系式。结果表明,工艺参数对焊道宽度的影响主次顺序依次为摆动宽度、送丝速度、基板温度、焊接速度,对焊道高度的影响主次顺序依次为焊接速度、摆动宽度、基板温度、送丝速度。随摆动宽度的增大,焊道宽度逐渐增大,焊道高度逐渐减小;随焊接速度的提高,焊道宽度和焊道高度均逐渐减小;随送丝速度的提高,焊道宽度和焊道高度也随之同步增大;随基板温度升高,焊道宽度增大,焊道高度降低。

焊接工艺参数与焊道成型参数研究

在复杂空间曲线的多层多道焊接过程中,每层道的焊道都会影响最终焊缝成型质量,而焊缝成型质量与焊接工艺参数相关。为了探究此种关系,搭建了以氩气作为保护气体的单道熔覆试验平台,根据对13组试验结果的分析,获得了各焊接工艺参数与焊道成型参数的影响规律,发现焊接电流保持不变,焊道横截面积、熔宽、余高都随着焊接速度的减小而增大,当焊接速度保持不变,焊道横截面积、熔宽、余高都随着焊接电流的减小而减小。采用二次旋转组合设计的方法建立数学模型,预测焊道成型参数以及根据焊道信息确定焊接工艺参数,将焊接速度作为模型的输入,焊接横截面积、余高、熔宽作为模型的输出,对该模型进行回归检验,并经过反编码计算得到输入与输出的关系表达式。最后,基于模型得到了焊接工艺参数与焊道成型参数的关系曲线图,为后续的焊接工艺参数选择以及多层多道焊路径规划提供理论指导。

浸锡导线电阻焊后锡珠控制研究

为解决小型断路器浸锡导线与线圈电阻焊接产生的锡珠喷溅不良率过高的问题,文中主要从辅助工装、电极材质、以及焊接工艺参数3个方面进行研究。试验研究结果表明,增加吹气工装、电极采用Cu-Al2O3、缓升时间为120 ms、保持时间为200 ms,锡珠喷溅不良率可以从53%降低至1%。