Effects of welding current on properties of A-TIG welded AZ31 magnesium alloy joints with TiO_2 coating

The effects of welding current on the macro-morphology, microstructure and mechanical properties of tungsten inert gas(TIG) welded AZ31 magnesium alloy joints with TiO2 coating were investigated. The results showed that the increase of welding current led to the increase in the depth/width ratio and deteriorated the surface appearance of the welded seams with TiO2 coating. The grain size of α-Mg and the amount of granular β-Mg17Al12 particles in the welded seams also increased. The welded joints with TiO2 coating exhibited a deeper weld penetration and larger grain size compared with the welded joint without TiO2 coating. When the welding current was less than 130 A, the ultimate tensile strength of the welded joints with TiO2 coating increased with the increase in welding current and then decreased when the welding current was greater than 130 A. The average microhardness of the heat-affected zone and fusion zone decreased gradually with the increase of welding current.

Optimality analysis of multiplex A-TIG welding flux for nickel-base superalloy

Orthogonal experiment is employed to study a new kind of multiplex flux for nickel-base superalloy. This activated TIG welding flux is composed of NaF, MgF2 and CaF2, and their proportion is 5：4：1. Compared with conventional TIG welding, the penetration increases 164% by the action of the flux. Tensile test result indicates that the fracture strength of the mixed flux A-TIG weld bead is higher than base metal, and it increases along with the decrement of the welding current. The average extensibility of the weldment is beyond 100%, which means perfect ductility. MetaUographs elucidate that there exist lots of deep and evenly distributed dimples on the fiacture section of weld bead while on that of base metal there only exists a few shallow dimples and massive tearing ridge.

Activated flux tungsten inert gas welding of 8 mm-thick AISI 304 austenitic stainless steel

AISI 304 stainless steel plates were welded with activated flux tungsten inert gas(A-TIG) method by utilizing self-developed activated flux. It is indicated from the experimental results that for 8 mm-thick AISI 304 stainless steel plate, weld joint of full penetration and one-side welding with good weld appearance can be obtained in a single pass without groove preparation by utilizing A-TIG welding. Moreover, activated flux powders do not cause significant effect on the microstructure of TIG weld and the mechanical properties of A-TIG weld joints are also superior to those of C-TIG(conventional TIG) welding.

Hybrid Intelligent Modeling for Optimizing Welding Process Parameters for Reduced Activation Ferritic-Martensitic (RAFM) Steel

Reduced-activated ferritic-martensitic steels are being considered for use in fusion energy reactor and subsequent fusion power reactor applications. Typically, those reduced activated steels can loose their radioactivity in approximately 100 years, compared to thousands of years for the non-reduced-activated steels. The commonly used welding process for fabricating this steel are electron-beam welding, and tungsten inert gas (TIG) welding. Therefore, Activated-flux tungsten inert gas (A-TIG) welding, a variant of TIG welding has been developed in-house to increase the depth of penetration in single pass welding. In structural materials produced by A-TIG welding process, weld bead width, depth of penetration and heat affected zone (HAZ) width play an important role in determining in mechanical properties and also the performance of the weld joints during service. To obtain the desired weld bead geometry, HAZ width and make a good weld joint, it becomes important to set up the welding process parameters. The current work attempts to develop independent models correlating the welding process parameters like current, voltage and torch speed with weld bead shape will bead shape parameters like depth of penetration, bead width, HAZ width using ANFIS. These models will be used to evaluate the objective function in the genetic algorithm. Then genetic algorithm is employed to determine the optimum A-TIG welding process parameters to obtain the desired weld bead shape parameters and HAZ width.

Microstructure and mechanical properties of TIG/A-TIG welded AZ61/ZK60 magnesium alloy joints

The dissimilar joints of AZ61 and ZK60 magnesium alloys were obtained by tungsten inert gas arc(TIG)welding and activating tungsten inert gas arc(A-TIG)welding processes.Microstructure characterization shows that,the fineα-Mg equiaxed dendrite crystals contained Mg17Al12 and MgZn2 particles in the fusion zone.The average size of theα-Mg grains in the fusion zone was refined to 19μm at welding current of 80 A,which resulted in the largest tensile strength of 207 MPa.The tensile strength and the width of the beam of the A-TIG welded AZ61/ZK60 joints showed strong dependence on the amount of TiO2.However,the inhomogeneity of the heat-affected zone near different base metals presented no significant effect on the mechanical properties of the welded joint.

Prediction of Ac1 temperature in P92 steel weld metal

The effects of major alloying elements on the Ac, temperature in P92 steel weld metal were evaluated by Thermo- Calc, and a formula relating Ac1 to the content of major alloying elements was developed using multiple regression method. Results show that both C and N reduce Ac, temperature in weld metal, the effect of N on Ac, is greater than that of C, but their influence on Act is not so significant when they individually vary in the specified chemical composition ranges. Si, Cr, Mo and W increase the Acl temperature, and the descending order of their effects is determined as Si, Mo, W, Cr. Mn and Ni decrease the AcI in weld metal, the decreasing effect is especially remarkable when the （ Mn ＋ Ni） ≥ 1%. The effect of Co is moderate and is much smaller compared to Ni. The variations of Acl for the ranges of micro-alloying elements Nb and V are also evaluated, the effect of V is greater compared to Nb and the effect of Nb could be ignored in the specified chemical composition range. A prediction formula for Ac, temperature in P92 steel weld metal within the specified chemical composition ranges was developed based on the comprehensive consideration of the calculated Ac, temperatures and the experimentally measured results.

Two-mode intelligent coordinating control of position for the welding positioner

A new intelligent control method for welding positioner is proposed. Applying an improved fuzzy controller and a variable PID controller, a two-mode intelligent coordinating controller ( TMICC ) is designed on basis of fuzzy logic and rules. The simulation and experimental results show that this control system can obtain better dynamic and static characteristics.

交流及脉冲GTAW铝合金焊接电弧温度及其形态数值模拟研究

控制钨极氩弧焊接(GTAW)的焊接电弧温度、形态等特性是制定其焊接工艺、提高其焊接质量与效率的措施之一。采用数值模拟研究方法,研究了6061铝合金GTAW焊接过程钨极氩弧温度及其形态,对交流及脉冲钨极氩弧温度及其形态进行了比较与分析,阐述了随焊接电流变化钨极氩弧温度及其形态变化规律。研究结果表明,在交流钨极氩弧焊接电流方向变化时焊接电弧将熄弧,其温度下降;焊接电弧形态基本保持钟罩型,其高温区域发生变化;在交流钨极氩弧达到稳定状态时,正接焊接电弧温度较反接的高,焊接电弧高温区域距工件更近,焊接电弧径向尺寸较反接的大;脉冲电流钨极氩弧焊接过程不会熄弧;从峰值到基值焊接电流过渡过程中,焊接电弧沿径向收缩,相反,焊接电弧沿径向扩张,其形态似“腰鼓”状;脉冲基值电流焊接电弧温度较峰值电流的小。

活性剂增加铝合金交流A-TIG焊熔深机理研究

采用多组元活性剂AF305进行铝合金交流A-TIG焊时,熔深达到传统TIG焊的3倍以上。进行了交流、直流正接和直流反接A-TIG焊,发现极性不同时活性剂对熔深的影响也不同。研究了强制电弧收缩对交流焊熔深的影响,发现弧根整体收缩并不是AF305增加交流A-TIG焊熔深的主要机理,熔深显著增加主要与焊渣成片分布有关。对焊渣进行了SEM形貌观察和EDS成分分析,并采用氦弧焊证实了焊接过程中焊渣在熔池表面成片分布,电弧斑点极大收缩。向AF305活性剂中添加铝粉改变焊渣分布,研究焊渣分布与熔深的关系,证实了焊渣成片分布能增加焊接熔深。认为焊渣成片分布使得电弧斑点极大收缩,斑点压力以及电弧和熔池内的Lorentz力增强,最终焊接熔深显著增加。

AC MIG与DC MIG焊接工艺及控制的分析

比较分析了DCEPPMIG焊与DCENMIG焊的焊接现象 ,在此基础上 ,解释了研究开发ACPMIG焊的意义。ACPMIG焊克服了DCEPMIG焊时容易产生的磁偏吹现象 ,且比DCEPPMIG焊的焊丝熔化速度快、焊缝熔深浅。ACPMIG焊有多种电流模式 ,其交流电流负极性比率ACIEN %主要用于控制焊缝熔深 ,其交流电流正极性脉冲IP主要用于控制熔滴过渡 ,最理想的是 1周 1脉 1滴的熔滴过渡形式。根据有关的研究表明 ,在相同送丝速度的条件下 ,ACPMIG焊的焊缝熔深随ACIEN %增加而减小 ,焊缝表面光泽好 ,焊丝熔化金属热含量低等 。

新能源汽车铝电池盒MIG焊接新工艺

在铝合金电池盒实际生产中,由于焊接位置较多、焊接接头板厚差异大,焊接一次合格率很难控制,这就需要研发一种焊接工艺提升铝合金薄厚板焊接的稳定性。目前铝合金电池盒MIG焊接主要是直流脉冲焊接,其中包括直流单脉冲或直流双脉冲焊接。通过分析发现,采用直流+交流摆动同步双脉冲焊接,在相同电流情况下可有效降低焊接热输入,在相同热输入情况下可增加焊缝a值。并在铝合金薄厚板焊接时,可在厚板位置使用直流脉冲,薄板位置使用交流脉冲,保证厚板熔深且薄板不烧穿。摆动同步交直流焊接技术已经在实际生产中得到应用,并有效提高了焊缝合格率和生产效率。

新型双主轴搅拌摩擦焊设备结构可靠性研究

为了实现厚板铝合金等轻量化板材的高效高可靠连接,双主轴搅拌摩擦焊技术应运而生,但是目前适用于双主轴搅拌摩擦焊接的设备并不成熟。针对双主轴搅拌摩擦焊技术,设计了一种新型双主轴搅拌摩擦焊设备,利用ANSYS Workbench软件对所设计设备的机身和主轴进行了静力学分析,校核了机身和主轴的刚度与强度,并通过模态分析研究了设备的振动响应特性,验证了设备的结构可靠性。结果表明:在额定工况下,机身最大形变量0.55 mm,主轴安装位置形变量约0.20 mm;主轴最大形变量1.73μm,最大应变1.97×10^(-4),最大应力20.64 MPa。机身以及主轴的强度与刚度均满足双主轴搅拌摩擦焊连接工艺需求。主轴安装位置和丝杠等重要位置最大应力约20 MPa,远小于机身材料的许用应力。机身的1阶固有频率为53.58 Hz,主轴的1阶固有频率为3 387.0 Hz,避开了电机的工作频率,设备工作过程中振动稳定,不会发生共振现象。

AC／DCRP交替MIG焊接方法的研究

介绍ＡＣ／ＤＣＲＰ交替ＭＩＧ焊接方法。它可以显著改善交流ＭＩＧ焊的焊缝成形，同时克服直流ＭＩＧ焊的电弧磁偏吹。利用这种方法还可进一步开发熔深控制功能。

林肯AC1200焊接电源的节电技术应用

对渤海装备华油钢管有限公司的一条预精焊生产线使用电源的工作情况进行了分析,介绍了大直径焊管生产线美国林肯AC1200焊接电源的工作原理,并分析计算出其控制方式存在巨大的电能损耗。提出了两种林肯AC1200焊接电源的节电控制技术方案及其注意事项。经生产实践证明,该节电技术简单有效,节能效果显著,同时增加了焊接电源的使用寿命,取得了明显的经济效益。

铝合金AC-P-MIG焊丝熔化速度与焊缝成形

铝合金AC-P-MIG焊丝熔化速度主要受焊接电流、BEN比率的影响,在相同BEN比率下,焊丝熔化速度随焊接电流的增大而增大;在相同电流下,焊丝熔化速度随着EN比率的增大而增大.由于阴阳极等效压降的不同及电弧形态特征的差异,随着BEN比率的增加,焊丝得到更有效、更多能量的加热,故熔化速度加快.在同样送丝速度与焊接速度下,随着BEN比率的增加,焊接电流减小,熔深、熔宽减小,余高显著增大.因此AC-P-MIG可以有效解决薄板焊接易烧穿问题,并且可以提高搭接间隙范围,实现薄板的高速、高质量焊接.

林肯AC-1200交流焊接电源安全隐患分析

在美国林肯AC-1200交流焊接电源的使用过程中,发现焊接电源的两个输出接触器(output contactors)在没有吸合的情况下,其工件端(work stud)和电极端(electrode stud area)出现80 V左右交流电压的安全隐患。针对该隐患,分析了林肯AC-1200交流焊接电源的工作原理,找出了导致隐患的原因,并提出了防治措施。

基于连续信号自适应分解的钢轨交流闪光焊接过梁爆破定量分析

为实现对钢轨闪光焊微观过程——过梁爆破的定量分析,将钢轨交流闪光焊接过程细分为断路、短路、多过梁爆破、单过梁爆破4种类型;基于GoogLeNet卷积神经网络,提出将钢轨交流闪光过程高频连续电信号进行类Gram矩阵转化,再依据矩阵元素自适应优化生成时域图谱的卷积神经网络识别方法;应用该方法对闪光焊接过程高频数据进行识别,并对完整焊接过程进行定量分析。结果表明:经过数据自适应优化,4种类型时域图谱的分类识别准确率上升至97.8%,识别的最大混淆发生在多过梁爆破和单过梁爆破之间;多过梁爆破比率在闪平和脉动阶段约为20%,进入连续阶段后迅速上升至80%以上,短路比率在稳定脉动期间可稳定维持在60%;各类型的比率在不同阶段呈现明显阶段特征,且各阶段特征与钢轨交流闪光焊接实际过程的宏观特征相匹配,采用该方法也可实现对闪光焊接微观过程的定量分析。

The mechanism of penetration increase in A-TIG welding

The mechanism of the increasing of A-TIG welding penetration is studied by using the activating flux we developed for stainless steel, The effect of fluxon the flow and temperature fields of weld pool is simulated by the PHOENICS software, It shows that without flux, the fluid flow will be outward along the surface of the weld pool and then down, resulting in a flatter weld pool shape. With the flux, the oxygen, which changes the temperature dependence of surface tehsion grads froma negative value toa positive value, can cause significant changes onthe Weld penetration. Fluid flow will be inward along the surface of the weld pool toward the center and then down. This fluid flow pattern efficiently transfers heat to the weld root and produces a relatively deep and narrow weld.This change is the main cause of penetration increase. Moreover, arc construction can cause the weld width to become narrower and the penetration to become deeper, but this is not the main cause of penetration increase. The effects Of flux on fluid flow of the weld pool surface and arc profiles were observed in conventiOnai TIG welding and in A-TIG welding by using high-speed video camera; The fluid flow behavior was visualized in realtime scale by micro focused X-ray transmission video observation system. The result indicated that stronger inward fluid flow patterns leading to weld beads with narrower width and deeper penetration could be apparently identified in the case of A-TIG welding.The flux couldchange the direction of fluid flow i-n welding pool. It has a good agreement with the simulation result.

Effect of Active Gas on Weld Shape and Microstructure of Advanced A-TIG-Welded Stainless Steel

Advanced A-TIG method was conducted to increase the weld penetration and compared with the conventional TIG welding process.A two-pipeline setup was designed to apply Ar ＋ CO_2 mixed gas as the outer layer,while pure argon was applied as the inner layer to prevent any consumption of the tungsten electrode.The results indicate that the presence of active gas in the molten pool led to the change in the temperature coefficient of surface tension so that the Marangoni convection turns inward and forms a deep weld zone.The increase in gas flow rate causes a decrease in the weld efficiency which is attributed to the increase in oxygen content in the weld pool and the formation o f a thicker oxide layer on the weld surface.Moreover,the stir and the temperature fluctuation,led by double shielding gas,create more homogeneous nucleation sites in the molten pool so that a fine grain micros true ture was obtained.

基于有限元分析的电机分瓣定子铁心拼接工艺技术

以某型号交流伺服电机分瓣定子铁心为例,针对分辦式定子铁心的拼接过程进行了研究,分析了分瓣式定子铁心拼接难点。进行了针对性的工装设计,通过样件的拼接、焊接以及精度检测验证,该工装的精度满足该型号分瓣式定子铁心的拼接要求,定子铁心拼接焊接后,外观质量、电气性能、精度要求均满足设计图纸要求,达到了预期效果。