熔池深度随电渣重熔过程变化规律的数模研究

通过数据的数学处理,找出了熔池深度与锭高和重熔电流间的规律.这一数学模式可用于描述和预示任意重熔电流时的最大熔池深度及随锭高增长熔池深度变化的趋向.熔池的深浅,影响金属结晶生长方向改变及夹杂物和气体的去除过程.合理控制重熔电流与熔池深度,对改善ESR锭铸态组织和材料品质是有益处的.     

电渣熔铸过程中电流大小对钢锭应力场影响的模拟

针对电渣熔铸钢锭各部位温差大、易产生热应力及测量困难的特点,采用大型有限元分析软件ANSYS,对电渣熔铸过程中电流变化时的钢锭应力场进行了模拟研究.结果表明,电流变化时的钢锭表面沿轴向自顶而下等效应力和轴向应力分布均遵循对数函数关系,模拟结果与实际结果吻合.运用此模型可预报钢锭应力场状况.     

非熔化极电渣堆焊

非熔化极电渣堆焊不同于熔化极电渣堆焊,有其独特的适用之处。石墨棒、钨棒或水冷铜棒均可作为非熔化极,但是由于水冷铜棒在熔渣里易发生电腐蚀断裂,且使用寿命相对较短,故其使用较少。堆焊时,由于石墨棒和钨棒的氧化和熔化,其尺寸发生变化,应注意熔入熔敷金属的碳和钨。随着非熔化极电渣堆焊的进行,填充金属和熔渣分别熔化,但它们之间相互关联。尤其是当填充金属的送丝速度增加时,也需通过将电极浸入熔渣内,增大堆焊电流,从而增加熔渣池的输入热量。这些反应都将影响金属熔池的形状和熔敷金属的性质。解决这些问题将有效改善非熔化极电渣堆…     

电渣熔铸过程电流大小对金属熔池影响的数值模拟研究

电渣熔铸过程中,金属熔池深度直接影响熔铸件的结晶,从而影响钢锭的质量。本文借助大型通用有限元软件AN-SYS,对不同电流大小时的金属熔池进行了模拟研究,得出金属熔池深度与电流大小之间存在一次线性函数关系的结论。模拟结果与实验值吻合较好。运用此模型可预报金属熔池状况,指导实际生产。     

数值模拟电极缩孔对IN718合金电渣重熔过程的影响

利用自主开发的ESR过程仿真软件,针对直径430 mm的IN718合金铸锭,通过设计不同形状尺寸的电极缩孔,进行电渣重熔过程的数值模拟计算和分析。结果表明,基于电磁场、流场和温度场等多物理场耦合计算自主开发的ESR数学模型及仿真软件,可以用于ESR冶炼全过程数值模拟,模型计算的熔池形状和深度、二次枝晶臂间距分布规律与实际剖锭分析结果接近。电极中存在缩孔改变了电极与渣池的接触面积,从而显著影响渣池的焦耳热和电磁力分布,而缩孔沿电极轴向尺寸的变化对二者分布的影响则很少。在恒熔速条件下,当缩孔半径小于0.025 m时,缩孔对熔炼过程几乎没有影响;当缩孔尺寸继续增大时,渣池温度场和流场发生明显改变,渣池温度逐步升高,中心向下流速相对减弱;电极缩孔尺寸变化对熔池温度场及两相区尺寸影响不明显。缩孔半径尺寸对电流和功率等熔炼参数的影响呈非线性关系,临界变化值约为0.05 m,当缩孔半径低于临界值时,对电流和功率等影响较小;高于临界值时,随着缩孔半径增加,电流和功率显著增加,并且增速不断加快。从工艺过程控制稳定性角度而言,该尺寸电极缩孔半径应控制在0.05 m以下。     

三相电极电渣重熔系统中的磁流体流动和传热分析

建立了三相电极电渣重熔的全耦合三维非稳态模型,研究了电渣炉内的电磁现象、两相流动、传热以及凝固现象。其结果表明:大量的电流流经金属熔滴和熔渣,极少数的电流流经凝固锭。焦耳热功率密度的最大值出现在电极周围和金属熔滴中。高温区位于渣池上部的中心,渣池的平均温度随电流的增大而升高。金属熔池为扁平的U形轮廓,当电流升高时熔池加深并且加宽。     

竖向钢筋电渣对焊机的使用与维修

随着我国现代化建设的发展。竖向钢筋电渣对焊机的使用日渐广泛．了解和掌握该设备的工作原理、使用方法和维修技术．对于广大操作者和维修人员来说。是非常必要的。l工作原理竖向钢筋电渣对焊是一种集电渣焊、埋弧焊和压力对焊三种焊接特点于一体的新的焊接方法。它包括电弧的引燃、埋弧燃烧、电渣过渡过程和压力状态下对焊几个工作过程。待焊两钢筋的端部被包围于焊剂之中，强大的电流使两钢筋端部引弧燃烧，使两钢筋端部的金属熔化并形成渣池。电孤燃烧到一定程度（上、下钢筋各熔化1．5～Zcm）使上钢筋插入渣地，焊接过程由电弧过程转…     

电流密度对定向凝固组织中柱状晶间距的影响

以Ｍ－Ｓ理论为基础，导出了定向凝固过程中电流通过固液界的情况下，电流密度与柱状晶间距的理论关系式，并对其进行了实验研究。结果电流密度增加时，其柱状晶间距近似呈直线下降的趋势。理论计算与实验结果基本吻合。     

宽带极电渣堆焊的磁场控制

利用外磁场控制克服大电流、宽带极电渣堆焊引起的咬边和成形不良是一种有效的方法。在分析不同磁控方式使用效果的基础上，试制并应用了方便可调的通电线圈的磁控装置；阐述了磁极位置、磁控电流、焊接规范对磁控效果的影响；提出了应用磁控应注意的问题。     

竖向钢筋电渣压力焊研究——设备部分

本文以介绍竖向钢筋电渣压力焊的设备部分:设备的系统(焊接电源、控制系统、焊接夹具、电流转换)、技术性能及现场考核。认为是竖向钢筋电渣压力焊的理想设备。     

脉冲MIG焊熔滴过渡中值波形的控制策略

针对脉冲MIG焊熔滴过渡过程的控制，提出中值波形控制策略的新工艺方法，详细阐述了中值电流及中值时间对焊接过程熔滴过渡的影响规律。采用中中值波形控制方法对钢进行焊接试验，确定了最佳的中值电流和中值时间。试验结果表明，中值电流较小时出现瞬时短路，中值电流较大时失去了中值阶段的作用，中值电流为一理想值时焊接效果较好。在确定了中值电流给定为理想值的基础上，得到了中值时间为一理想值时焊接效果较好，中值时间较小时不会过渡熔滴，而中值时间较大时会在中值阶段过渡多个熔滴的结果。     

Wire melting phenomena in gas metal arc welding

Abstract

The wire melting rate in gas metal arc welding using constant voltage power supplies is well described by a parabolic model that considers the effects of electrical resistance and arc heating. However, tests performed with constant current power supplies indicate that the melting rate can deviate from this model when welding current is close to the globular–spray transition value. Although the causes of this anomaly have not yet been well established, most authors consider them to be related to variations in liquid metal temperature close to the metal transfer mode transition current. The present work evaluates the effect of welding parameters on the wire melting rate when a constant current power supply is used. A numerical model that considers the contribution of both Joule and arc heating was developed to calculate the temperature distribution in the wire and its melting rate. The model was used to assess the changes in either arc heating or metal vaporisation that might explain the melting irregularities. High speed cinematography was used to analyse metal transfer in the current range associated with the melting irregularities.     

Study on Heat Generation Mechanism and Melting Behavior of Droplet Transition in Resistive Heating MetalWiresEI北大核心CSCD

With the development of space technology, the ability of manufacturing in space is a necessary guarantee for a long-term space mission. To achieve the repair and maintenance of spacecraft structure in space, a metal additive manufacturing method named resistance heating metal wire additive manufacturing process has been proposed in this work. During the experiments, the wire and the base plate are short-circuited, the current output from the programmable power source flows through the wire and the base plate to generate resistance heat, and then the wire begins to melt and transfer to the base plate. A real-time synchronization system has been used to record the current, voltage and image of metal wire synchronously, to study the melting process of metal wire by resistance heating. The direct current and pulse current with different amplitudes which were supplied by programmable power source have been used to study the effect of the current style and value on the melting process and transition behavior of metal wire. The change characteristic of the resistance in the wire and base plate has been analyzed during wire melting, to study the relationship between the current resistance and the wire state. The effect of gravity on the wire melting process has been studied by the wire transfer experiments at different space locations. The results show that when the metal wire was heated by the constant current, the total heat of metal melt could be controlled by controlling the current value, but it was difficult to precisely control the heating speed and the heat input. When using pulse current heating, both the heating speed and the heat input could be precisely controlled by pulse frequency and pick value. In the melt transfer stage, the constant current provides a fixed force on the molten wire, but the pulse current makes the molten wire swing by the intermittent force. The real-time resistance of metal wire during heating could be used to reflect the melting state of wire in both current styles. On the ground environment, the surface tension and electromagnetic contraction force make the melting wire against the gravity and transfer to the base plate, which illustrated the feasibility of using this process in space environment.     

焊接速度和焊接电流对竖向高速GMAW驼峰焊缝的影响

运用自主研发的爬壁机器人研究焊接速度和焊接电流对竖向高速熔化极气体保护焊(gas metal arc welding，GMAW)驼峰焊缝的影响. 结果表明，焊接速度或焊接电流超过某一临界值时，竖向高速GMAW会形成驼峰焊缝，且熔池中由电弧压力、熔滴冲击力和重力作用下产生的动量很大的后向液体流是竖向高速GMAW形成驼峰焊缝的主要原因. 同时，焊接速度和焊接电流显著影响驼峰焊缝形貌. 当焊接电流不变时，随焊接速度提高，驼峰焊缝的驼峰间距和驼峰高度先稳定减小，后缓慢减小，而焊缝宽度则稳定减小；当焊接速度不变时，随焊接电流增加，驼峰焊缝的驼峰间距先增加后减小，驼峰高度则是先增加后不变，而焊缝宽度则稳定增加. 此外，焊接速度过小或焊接电流过大均会造成金属液下淌.     

Radiation of metal atoms in the plasma of an atmospheric pressure glow discharge with an electrolyte cathode

The radiation of atoms of lithium (λ = 670 nm), sodium (λ = 588–589 nm), and calcium (λ = 657.2 nm, triplet) in an atmospheric pressure glow discharge plasma when the solution of the salt of the respective metal serves as a cathode is experimentally studied. It is shown that, in a system with solution circulation, the intensity of the mentioned lines during the discharge burning process rises tending to a constant limit value. The characteristic time of the establishing of the radiation intensity asymptotic value for the solutions of lithium, sodium, and calcium salts is 22, 5.5, and 9.5 minutes, respectively. These variations correlate with the previously observed growth of the rate of the nonequilibrium transfer of the solution components into the plasma zone. It is also found that the relationship between the line intensity and the discharge current is characterized by the presence of the threshold current (10–15 mA). The transfer from an alkaline solution to an acid one is attended with an increase of the intensity of the radiation of metal atoms.     

超声电弧激励电流对MGH956合金TIG焊缝气孔和拉伸性能的影响

通过高频调制TIG焊电弧激发超声电弧,对MGH956合金进行TIG焊接,对比了在不同激励电流作用下焊缝的气孔数量和性能的变化,分析了超声电弧的作用机制.结果表明,与未施加超声电弧相比,在激励电流为5A或10 A时,焊缝气孔明显长大,但数量并没有减少,在激励电流提高到20A或30 A后,气孔数量急剧减少;超声电弧的引入,使焊接接头的抗拉强度得到提高,且在激励电流为20 A时,焊缝的抗拉强度达到最大为550 MPa,达到母材的76％,同时接头由完全的脆性断裂变成脆性-韧性混合断裂形式.     

Potentials of electrochemical reactions and nature of singularities in electrode polarization dependences

The conditions of transition of the electrochemical polarization mode to a faradaic process are studied on the metal electrode within the framework of the microscopic approach when the value of polarization potential reaches the threshold value of the potential of the electrochemical reaction. It is suggested that the elementary act of electron transfer between the metal and redox electrolyte occurs at the interface under polarization bringing the local electron level of the reagent to the Fermi level of electrons of the metal. Discharge through the Helmholtz layer limited by electrons occurs due to resonance “lightening” of the potential barrier between the metal and localized redox state of the reagent. Estimates are obtained for the values of threshold potential and exchange current of the faradaic process. A method is suggested for consideration of the elementary act of the electrochemical reaction on the basis of the Hamiltonian describing the microscopic mechanism of Fermi edge singularities. Application of the known solutions allows the appearance of threshold singularities of polarization dependences in electrochemistry to be explained.     

用开槽弯曲成形方法加工金属异型材

小批量多品种的金属异型材成形,可以采用开槽弯曲方法进行,即开槽弯曲成形方法。这种开槽弯曲成形金属异型材的加工方法步骤简便,工艺直观,不需制作复杂的模具,使用现有的通用板材加工设备和模具(如板料开槽机、板料折弯机)即可制作加工复杂的金属异形型材,具有在多种行业使用推广的价值。     

铝合金P-MIG焊接电流对电弧形态的影响

通过对铝镁合金进行脉冲氩弧焊(P-MIG),在相同平均电流和平均电压工作条件下,调节不同峰值电流和基值电流,获得了不同的电弧形态.峰值电流对电弧形态有着重要的影响,而基值电流基本没有影响.基值电流是维持电弧燃烧的参数,在基值时间阶段,必须给定一个足够大的基值电流才能维持电弧的稳定燃烧.文中定义了电弧形态的表征值,针对电流对电弧形态表征值的影响进行了分析.峰值电流是决定电弧温度和脉冲能量的重要参数,铝合金电弧充分燃烧时电弧长度、电弧宽度和电弧纵向截面面积随着峰值电流增加而增加.

Abstract：

Under the same average welding current and welding voltage, by regulating the different based current and peak current, the Al-Mg alloy was welded with Al-Mg filler wire. The photos of welding arc were obtained by using high-speed video photography.Peak current has great influence on the shape and characteristics of the arc. With increasing the peak cunent value, rotated arc appears and pulsed rotated metal transfer behavior occurs. Based current has little influence on the arc shape. Base current is the important parameter for keeping arc burning. At pulse off time, it must be given base current value which is large enough to keep the arc burning stably. In this study, the arc shape is defined by arc length, arc width and arc portrait cross-section area, which will be influenced by the weld current. Peak current is important parameter of arc temperature and pulse energy. The study shows that when the arc is burning at pulse on time, the arc length, arc width and arc pomait cross-section area increase with raising peak current.     

TC17钛合金电子束焊接接头的疲劳裂纹扩展规律及疲劳剩余寿命

首先通过试验取得母材及焊接接头的疲劳裂纹扩展速率,然后结合TC17钛合金电子束焊接接头CTOD试验结果及裂纹容限计算值,以估算其疲劳剩余寿命.结果表明:在低应力水平或低△K下,TC17电子束焊缝的da/dN数据与母材的基本相当;然而随着应力水平的增加,焊缝的da/dN值越来越大.在初始裂纹尺寸相同的情况下,TC17合金电子束焊缝与母材疲劳裂纹扩展寿命曲线存在交叉点.当应力幅大于交叉点应力幅时,TC17母材疲劳裂纹扩展到临界裂纹尺寸的剩余寿命要高于相应焊缝的剩余寿命;当应力幅小于交叉点应力幅时,TC17母材扩展到临界裂纹尺寸的剩余寿命要低于相应焊缝的剩余寿命.