外加纵向磁场GTAW焊接机理：Ⅰ电弧特性

针对外加纵向磁场GTAW（gas tungsten-arc welding)焊接过程,采用红外热像伪着色法测定了外加纵向磁场GTAW焊接电弧的温度场,并建立了外加纵向磁场GTAW焊接电弧热流密度径向分布模型,对焊接电反外形的变化,焊接电弧电流,电压与外加纵向磁场强度变化的关系进行了研究。     

外加纵向磁场GTAW焊接机理：Ⅱ。电弧模型

针对外加纵向磁场GTAW（gas tungsten-arc welding)焊接过程,采用小孔气体微压传感器法和钨极探针法分别测定了外加纵向磁场GTAW焊接电弧在水冷Cu阳极上的等离子流力和电流密度的分布,并对其规律进行了研究,建立了外加纵向磁场GTAW焊接电板等离子流力和电流密度的径向分布数学物理模型。     

外加纵向磁场GTAW焊缝成形机理

以外加间歇交变纵向磁场GTAW（气体保护钨极氩弧焊）为研究对象,通过采用测量相关参数和拍摄电弧的方法,研究了间歇交变纵向磁场GTAW焊接低碳钢、不锈钢和铝合金等材料焊缝成形发生变化的规律和原因。认为在本研究条件下,无论处于溶池下方还是上方的单励磁线圈产生的外加纵向磁场都使GTAW焊接电弧特征、熔池行为和结晶过程发生了变化,从而导致焊缝成形的改变;同时发现当励磁线圈和电弧中心线不同轴心时,外加磁场对焊缝成形的影响较为强烈,其中铁磁性材料所受影响较显著。     

快速行走TIG焊接时熔透信号的提取及分析

焊接熔池的振荡特性,可以做为焊缝的熔透信号。在脉冲电弧力作用下,熔池金属产生振荡,当电弧快速行走时,外加横向磁场控制电弧,可靠地提取出熔池振荡信号。检测发现,熔池振荡频率与熔池尺寸之间存在着良好对应关系,实验焊接速度达到200mm/min 以上.     

3D finite element modeling of the thermally induced residual stress in the hybrid laser/arc welding of lap joint

In this study, a three-dimensional (3D) finite element model is developed to investigate thermally induced stress field during hybrid laser–gas tungsten arc welding (GTAW) process. In the hybrid welding case, we focus on the GTAW process sharing common molten pool with laser beam and playing an augment role in the hybrid welding system. An experiment-based thermal analysis is performed to obtain the temperature history, which then is applied to the mechanical (stress) analysis. A modified material model is used to consider the influence of face-to-face contact between the top and bottom metal sheets in the thermo-mechanical analysis of welding lap joints. Results show that the normal stress components prevail in the weld zone during hybrid welding process, and maximum thermal stress exceeding the yield point of material exists at the heat affected zone (HAZ) near the weld pool. Increasing the welding speed causes the penetration and width of weld bead to decrease, and the thermal stress concentration at the welded joint is also reduced accordingly. After welding and cooling down, longitudinal tensile stress (SZ) and transverse compressive stress (SX) are retained in the formed weld, and the higher longitudinal compressive stress exists around the weld bead. In addition, a series of experiments are performed to validate the numerical results, and a qualitative agreement is achieved. Compared to the welded joint obtained by GTAW and laser welding alone, the residual stress concentration in the weld joint obtained by hybrid laser–GTAW is the minimal one.     

高频交变磁场对大电流GMAW熔滴过渡和飞溅率的影响

在熔化极气体保护焊过程中,采用大送丝速度,增大焊接电流和焊丝伸出长度是提高焊接熔敷率的直接途径.但当熔滴过渡转变为旋转射流过渡时,电弧不稳,飞溅增大,焊缝成形变差.施加不同频率的纵向交变磁场,对焊缝成形进行控制.采用高速摄像技术,拍摄焊接过程中的电弧形态和熔滴过渡,研究不同频率的磁场对熔滴过渡和焊接飞溅率的影响规律.结果表明,熔滴过渡形式不同,产生飞溅的机理不同;外加频率为1 000 Hz纵向交变磁场时,电弧的旋转半径减小,电弧的挺度增大,旋转射流过渡时电弧更稳定,焊接飞溅率降低,焊缝成形改善.     

外加纵向磁场GTAW平板堆焊温度场数值模拟与验证

利用ANSYS对外加纵向磁场作用下GTAW平板堆焊过程温度场进行了数值模拟,并进行了实验验证.结果表明.所采用的简单磁控焊接电弧热源模型在外加磁场作用下形成"钟罩形"电弧,模拟焊接温度场与实验结果基本吻合.     

外加磁场对CO2焊接焊缝成形的影响

针对CO2气体保护焊飞溅大、成形差的特点,利用外加纵向磁场控制CO2焊短路过渡.通过试验得出:在外加纵向磁场作用下,熔深减小,熔宽增加,焊缝堆高略有增加,焊缝大致成"宽而浅"的形状,明显改变了CO2焊短路过渡的焊缝成形.     

Experimental Investigation into the Effects of Weld Sequence and Fixture on Residual Stresses in Arc Welding Process

This study concentrates on the effects of weld sequence and welding fixtures on distribution and magnitude of induced arc welding residual stresses built up in butt-joint of Gas Tungsten Arc Welding (GTAW) AA5251 plates. Aluminum plates have been welded under different welding conditions and then, longitudinal and transverse residual stresses were measured in different points of the welded plates employing hole-drilling technique. The results indicate that welding sequence significantly alters the distributions of both longitudinal and transverse residual stresses while the changing in the weld sequence leads to 44% decrease in longitudinal residual stress. Besides, both the geometry of weld pool and distribution of residual stresses are affected by the welding fixtures while implementation of fixture causes about 21 and 76% reductions in the depth of weld pool and transverse residual stress, respectively, for the material and welding conditions used in this research.     

磁控焊接技术的研究现状

介绍了磁控焊接技术的基本原理及装置,并从其对电弧形态、熔滴过渡形式、熔池内液态金属温度场及流动状态等的影响进行了阐述。与普通的焊接技术相比,磁控焊接技术将磁场产生的磁场力引入到焊接过程中并对其进行干涉,通过调节磁场的方向和大小能够改善焊缝成形、改变接头组织及提高力学性能等。因此开展磁控焊接技术的研究具有很高的工程实用价值。     

GTA焊接电弧与熔池系统的双向耦合数值模拟

建立了GTA焊接过程电弧与熔池双向耦合统一数学模型．该模型考虑了熔池自由表面变化对电弧和熔池的影响,并通过不断更新自由表面形状实现了电弧与熔池相互耦合．电弧和熔池的两组控制及辅助方程采用有限差分法进行求解．计算中采用了适体坐标系以确定不断变化的自由表面形状．用所建模型对304不锈钢材料的定点GTA焊接过程进行了数值计算分析,取得了良好效果．     

焊接方法对双相不锈钢焊接接头耐蚀性的影响

采用气体保护钨极氩弧焊（GTAW）、焊条电弧焊（SMAW）和埋弧焊（SAW）对2205双相不锈钢进行焊接,采用光学显微镜对接头组织进行观察,采用数点法计算铁素体相的含量,测定接头的耐点蚀和耐CO2应力腐蚀性能,研究焊接方法对接头耐蚀性的影响。结果表明,焊接方法影响焊缝组织形态及铁素体含量。GTAW焊缝由不规则的条状组织和两相交织分布的块状组织组成,而SMAW和SAW焊缝为方位不一的条状组织和少量的块状组织。GTAW和SMAW焊缝的铁素体含量为35％～55％,而SAW的不足20％。接头的耐蚀性与铁素体相比例密切相关,GTAW、SMAW和SAW的耐蚀性依次降低。从铁素体相比例和耐蚀性角度考虑,GTAW和SMAW能够获得满意的焊接接头。     

9%Ni钢焊接中的磁偏吹及其防止

本文就9%Ni钢焊接中引起磁偏吹的原理作了初步阐述。外加磁场所产生的洛伦茨力和焊接电流自身产生的电磁收缩力向量的和决定了磁偏吹的强弱。9%Ni 钢焊接时,若母材剩磁强度超过60Oe,则可能引起未熔合、未焊透、夹渣等焊接缺陷。因此,在9%Ni 钢焊接时,要采取相应措施消除剩磁的作用,克服磁偏吹所引起的焊接缺陷,才能保证9%Ni 钢的焊接质量。     

外加横向磁场对高速GMAW焊缝成形的影响

对于高速熔化极气体保护焊接（GMAW）过程,当焊接速度超过临界值后,会出现驼峰焊道,焊缝成形变差.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.研发了外加横向磁场发生装置,通过产生的电磁力来抑制后向液体流的动量,从而抑制驼峰焊道的形成.应用特斯拉计测试和考察了工件上磁感应强度大小及分布的影响因素.通过开展焊接工艺试验分析了不同强度的外加磁场作用下的焊缝成形规律.结果表明,外加横向磁场能明显调控熔池流态,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.     

Magnetic field in electric arc welding

It is shown that the longitudinal magnetic field of welding current in welding of two sheets transforms to the field of a single sheet and this confirms the electromagnetic nature of the interatomic binding forces. At a gap of 0.002 m and as a result of the separation of the lines of force, the induction of the longitudinal magnetic field of welding current rapidly increases and the arc starts to rotate. The electromagnetic force and magnetic pressure directed forward and to the side edges of the weld pool then appear. This results in the movement of liquid metal to the front part of the crater and to the side edges, formation of welded joints without undercutting, and confirms the electromagnetic nature of the formation of undercutting in one-sided high-speed welding. A method of one-sided high-speed welding with a compound electrode on a flux cushion with a gap of 0.002 m has been developed. The method improves the stability of the process and impact toughness of welded joints.     

磁致旋转射流过渡MAG焊接工艺分析

在设计一种工程实用性强、小型化的纵向磁场发生装置的基础上,将纵向磁场引入到98％Ar＋2％O2保护的射流过渡MAG焊中,提出了一种稳定、可控、有规律的磁致旋转射流过渡MAG焊接工艺,并详细研究了励磁电流（磁场强度）对电弧形态及运动行为、焊丝熔化特性、熔滴过渡机制和焊缝成形的影响规律,同时指出了该工艺的不足之处一纵向磁场在抑制指状熔深的同时却形成了偏心焊缝。结果表明,外加纵向磁场后,MAG焊电弧、液锥和液流束都偏离焊丝轴线并高速旋转,熔滴过渡虽然偏离了焊丝轴线,但仍在电弧烁亮区内部进行;随着励磁电流的增大,电弧旋转角速度增加,可见弧长缩短,熔滴过渡速度加快,焊接电流减小,焊丝熔化系数提高。     

磁场与粉煤灰联合作用下TIG焊电弧行为

为了研究活性剂与高频磁场联合作用对电弧行为影响及熔深改变机理,使用粉煤灰作为活性剂对Q235钢进行A-TIG焊,并在焊接过程中施加高频纵向磁场,实现两者的联合作用.试验中对不同的涂覆量下A-TIG焊缝形貌进行分析,发现当涂覆量为0.3 mg/mm²时,熔深增加最为明显,在此涂覆量下引入1.5 kHz高频纵向磁场,熔深达到2.70 mm,为普通氩弧焊的1.8倍,但磁场频率继续增加,熔深则会出现下降趋势.采集焊接过程中电弧形貌、电流密度、电弧力及电弧温度的变化数据,分析活性剂与高频纵向磁场对TIG焊的联合作用机理,发现活性剂与磁场的联合作用能够改变外部磁场在等离子体内的分布使带电粒子受到更大的洛伦兹力,导致电弧在一定范围内进一步收缩;同时,与磁控-TIG相比,能够改善高频磁场引起的“磁抽吸”现象,使电弧热量更加集中.     

Co基堆焊合金力学性能的磁场控制

将直流纵向磁场引入等离子弧钴基合金堆焊过程中,研究了磁场强度和焊接电流对堆焊层硬度和耐磨性的影响,并对磁场作用机理进行理论研究分析。结果表明:磁场强度应和焊接电流配合使用;适当的外加磁场不仅可以细化堆焊层金属组织的晶粒,而且由磁场产生的电磁搅拌能够提高堆焊层金属的硬度,使堆焊层的耐磨性也显著增强,从而提高堆焊层金属的综合力学性能。     

弧光法与激光视觉法检测熔池振荡特征的对比分析

为了研究不同焊接条件下激光视觉法与弧光传感法对脉冲GTAW焊熔池振荡信号的传感效果,分别建立了相应的试验系统,并进行了提取脉冲GTAW定点及连续焊熔池振荡频率的试验,对比分析了两种方法的传感效果. 结果表明,定点焊时弧光传感法与激光视觉法都能够稳定并准确的检测出熔池振荡频率;连续焊时随着焊接速度的提高弧光法传感获得熔池振荡信号质量变差,而焊接速度的变化对激光视觉法获得熔池振荡信号质量影响较小. 因此在连续焊接条件下,激光视觉法具有更好的适应性.