交流脉冲MIG焊接铝合金薄板的工艺特性

交流脉冲MIG焊其焊缝熔深及焊丝熔化速度不仅与焊接电流有关，而且与负极性比率有关。当负极性比率等于零即直流且焊丝为正极性的MIG焊时，其焊缝熔深最大，焊丝熔化系数最小，熔敷速度最小；随着负极性比率增加，焊缝熔深减小，同时焊丝熔化系数增加，熔敷速度增加。交流脉冲MIG焊接铝合金薄板时，通过调整焊接电流及负极性比率，形成浅焊缝熔深的同时，形成较高的熔敷速度，从而可以提高焊接速度，避免出现烧穿及熔池下塌现象，保证焊接质量。     

交流电阻点焊中电极位移波动特征的分析

利用改进的交流电阻点焊监控系统采集电极位移和焊接电流,经分析认为电极位移曲线上的波动是由50 Hz的交流电阻热脉冲引起的.利用电阻点焊中的洋葱环现象分析了电极位移波动特征的机理,认识到电极位移在熔核形成前以热膨胀为主,在熔核形成后以相变膨胀为主,并且都具有波动特征.利用焊接电流曲线提供的晶闸管触发角和导通角依次计算功率因数角、动态电阻和动态电阻热.通过位移波动周波峰值与动态电阻热的对比分析,发现位移波动周波峰值在点焊过程中对热膨胀与相变膨胀有较强的敏感性,能用来反应熔核形成过程的不同阶段.     

用电流波形控制法提高镀锌钢板点焊电极的寿命

作者通过分析镀锌钢板点焊电极寿命降低的原因，提出了提高镀锌钢板点焊电极寿命的电流波形控制法。采用该方法进行了点焊电极寿命试验，研究了工件表面飞溅率和电极寿命随焊前电流脉冲的幅值、焊前电流通电时间的变化规律。试验结果表明：采用电流滤形控制法可将镀锌钢板点焊电极的寿命由原来的400点以980点；工件表面的飞溅率及电极寿命与焊前电泳脉冲幅值、焊前电流通电时间有关。     

AC MIG与DC MIG焊接工艺及控制的分析

比较分析了DCEP P MIG焊与DCEN MIG焊的焊接现象,在此基础上,解释了研究开发AC P MIG焊的意义。AC P MIG焊克服了DCEP MIG焊时容易产生的磁偏吹现象,且比DCEP P MIG焊的焊丝熔化速度快、焊缝熔深浅。AC P MIG焊有多种电流模式,其交流电流负极性比率AC I EN％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,AC P MIG焊的焊缝熔深随AC I EN％增加而减小,焊缝表面光泽好,焊丝熔化金属热含量低等,这些特点最适宜用于焊接薄板。     

交流点焊工艺参数对AZ31B镁合金接头性能的影响

研究了AZ31B镁合金交流点焊中焊接电流、电极压力及焊接时间等工艺参数对接头拉剪力的影响规律，确定了最佳工艺参数为焊接电流17000A，电极压力2475N，焊接时间为10个周波，预压时间为20个周波，该条件下接头达到最大拉剪强度为l980N；同时试验得出表面状态对接头性能有着显著的影响。     

脉冲频率对三丝间接电弧焊稳定性的影响

三丝间接电弧焊是一种新的焊接方法,焊接过程中工件不连接电源,主丝连接焊接电源正极,两边丝分别连接两焊接电源的负极,电弧建立在主丝与两边丝之间.焊丝熔化后主丝与边丝导电距离的变化以及焊丝形成的多条熔滴过渡路径均对建立稳定的焊接过程提出了挑战.文中通过调控脉冲频率,分析了脉冲频率对电弧特性、熔滴过渡路径以及焊接电压和焊接电...     

Development of an automatic arc welding system using a sliding mode control

This paper describes the development of an automatic welding control system for alternating current shield metal arc welding. This method could replace manual operations which require a well-trained technician. We have derived a mathematical model of the welding control system and identified system parameters. An adaptive sliding mode controller, estimates the bound of uncertainties, and modulates the rate of the electrode feed mechanism that regulates the arc current. The electrode feed-rate mechanism with this controller is driven by an AC servomotor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. The method can be easily applied to any welding system in which the electrode is consumed during the welding process. By maintaining the magnitude of the arc current at the desired value and the stability of the arc length, excellent welding performance is obtained. The simulation and the experimental results both show that this automatic welding control system, based on the adaptive sliding mode controller, can perform effectively.     

交流脉冲MIG弧焊电源及弧长控制

AC PMIG的控制模式是一周一脉一滴，脉冲电流设计在电弧EP极性时间里，其余时间均为基值电流。弧焊电源一次逆变控制电流快速动态过程，二次逆变控制电弧极性。控制系统采用双闭环结构，内环模拟控制电弧电流，外环80C196KC单片机控制电弧电压及电弧极性。根据电弧电压偏差信号及电弧状态，设计了四个控制规则及其控制参数的计算方法。正常焊接状态时变频控制交流脉冲频率。采用这种控制方案，获得了稳定性高、熔滴过渡均匀的焊接过程。     

变极性TIG焊接电源的研制

变极性TIG焊接电源是一种用于铝合金焊接的新型焊接设备，其焊接电流频率、正负半波电流时间和幅值都可以分别独立调节。主电路结构采用2级逆变，前级为全桥逆变式结构，后级为半桥逆变式结构。该电源可实现变极性方波交流、直流、脉冲电流等多处输出。在DCEN向DCEP过渡时采用叠加电流脉冲进行稳弧，小电流时焊接电弧也十分稳定。调节正负半波的幅值、频率及占空比能满足铝及铝合金的焊接工艺要求。     

熔化极脉冲焊熔滴过渡合理形式的研究

本文利用高速摄影机和示波器研究了钢焊丝熔化极脉冲焊的各种熔滴过渡形式,试验是在平焊和仰焊位置进行的。作者指出虽然一脉冲一滴和一脉冲多滴的过渡形式在平焊和仰焊位置都能提供稳定而有力的轴向熔滴过渡,但前者只能在很窄的焊接规范区存在,而后者有较宽的焊接规范区间。因此一脉冲多滴的过渡形式是更合理的。熔化极脉冲焊存在两个区分不同熔滴过渡区的临界电流。第一个称为“临界脉冲过渡电流”它是一脉冲过渡一滴的下限电流。第二个称为“临界跳弧电流”,它是一脉冲过渡多滴的下限电流。文中还对熔化极脉冲焊的电弧形态与熔滴过渡形式的关系进行了研究和讨论。发现一脉冲多滴过渡的产生过程总是伴随着“跳弧”现象,亦即附着在熔滴端面上的烁亮弧根突然上跳到缩颈的根部。这种跳弧现象在一定的脉冲电流幅值和相应的脉冲电流时间产生。在通常的熔化极气电焊中,当由颗粒过渡转变到射流过渡时也出现这种跳弧现象。实质上,常规的熔化极气电焊过程的临界电流就是连续电流下的临界跳弧电流。下面的现象可说明这一点,在熔化极脉冲焊过程中,当延长脉冲电流时间时,临界跳弧电流将逐渐接近常规熔化极气电焊的射流过渡临界电流。在一脉冲一滴和一脉冲多滴的过渡过程,在脉冲电流停止后还能出现熔滴脱离的现象,这可能是由于焊条熔化金属运动的惯性和焊条端头上金属细液柱的失稳现象所引起的。     

双电极焊条单弧焊的电弧特性

针对双电极焊条单弧焊焊接新工艺，作者研究了其电弧静特性和双电极焊条的熔化特性，并用高速摄像机对双电极焊条单弧焊的电弧形态进行了研究。结果表明。双电极焊条单弧焊具有上升的电弧静特性，静特性曲线随两焊芯间距的增大而上移；在两焊芯间距合适的情况下，双电极焊条阴、阳极熔化速度可以保持一致，故双电极焊条单弧焊可使用交、直流电源，其熔化速度比单芯焊条的大并随焊接电流的增大和两焊芯间距的减小而增大；双电极焊条单弧焊电弧有多种形态。     

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．     

脉冲频数对pulsed DE-GMAW焊缝成形的分析

针对脉冲旁路耦合电弧焊（pulsed DE-GMAW）焊接过程中熔滴过渡和焊缝成形控制难题,基于高速摄像等在内的硬件系统和xPC的快速原型软件系统构成的试验系统,对不同的脉冲数量对熔滴过渡和焊缝成形的影响进行了分析.结果表明,在主路电流不变的情况下,随着双脉冲旁路电流的峰值脉冲数增加,自由过渡的次数增加;随着双脉冲旁路电流的基值脉冲数增加,短路过渡的次数增加.但较多的短路过渡次数会导致焊接过程不稳定,产生较大飞溅.在此基础上,确立了双脉冲旁路电流的双脉冲峰值脉冲数与基值脉冲数匹配来控制熔滴过渡方式,因此获得较好的焊缝成形.     

焊接与切割设备的使用和维修(四十八)--TIG焊机的使用与维修

首先简要介绍了交流电源的电流衰减方式；其次讲述了交流方波TIG焊机的特点、工作原理以及工作波形；最后详细介绍了脉冲TIG焊的主要特征、原理以及焊接时的工艺参数，并例举了不锈钢、钛合金、铝合金焊接时的工艺参数选择范围。     

Influence of process variables on weld bead quality in two wire tandem submerged arc welding of HSLA steel

Two-wire tandem submerged arc welding process involves simultaneous depositions from two electrode wires with the leading wire usually connected to a DC power source and the trailing wire connected to a pulsed AC power source. The weld bead profile and mechanical properties in the tandem submerged welding are significantly affected by the leading and trailing wire current transients and the welding speed. We present here a detailed experimental study on the influence of leading wire current, trailing wire current pulses, and welding speed on the weld bead dimensions and mechanical properties in single-pass tandem submerged welding of a typical HSLA steel. It is realized that the weld bead penetration is primarily influenced by the leading wire current while the weld bead width and the reinforcement height are sensitive to the trailing wire current pulses. Greater magnitude of trailing wire current pulses and shorter negative pulse duration increase the weld pool volume leading to reduced cooling rate and poor mechanical properties as the formation of the strengthening phases like acicular ferrite is inhibited. In contrast, increase in welding speed reduces the rate of heat input thereby enhancing the cooling rate and the weld bead mechanical properties. A set of empirical relations are developed to estimate the weld bead dimensions and mechanical properties as function of the welding conditions. The predictions from the empirical relations and the corresponding measured results are observed to be in fair agreement.     

添加镍颗粒的铝/钛异种材料电阻焊接头力学性能及显微组织分析

使用三相次级整流电阻焊机对LY12铝合金/TC4钛合金进行电阻点焊,并在板材中间添加了镍颗粒. 结果表明,最佳工艺参数为电极压力3.03 kN,预热脉冲焊接电流7.5 kA/10 cyc(1 cyc=0.02 s),焊接脉冲焊接电流12.1 kA/45 cyc,缓冷脉冲焊接电流7.5 kA/10 cyc,接头的最大拉剪力为7.12 kN. 铝合金侧熔核的显微组织为细小的等轴晶,钛合金侧熔核的显微组织为针状马氏体,IMC层由靠近铝合金侧的一层1～2 μm厚的NiAl3和在钛合金/铝合金之间散乱分布着的TiAl3共同构成.     

Relationships governing slip in the structure of the weld metal of welded joints in heat-resisting pearlitic steels

Summary

Previous papers have shown the high‐current AC‐MIG welding process to be superior to the conventional DC‐MIG process in terms of welding efficiency and welded joint performance. The authors have used the AC‐MIG process to weld heavy‐gauge steel plates at a tensile strength level of 980 MPa. Weld metal with a very low hydrogen content is obtained by the newly developed process, resulting in a reduced preheating temperature during welding of high‐strength steels. The AC‐MIG process also produces an arc climbing effect with electrode negative polarity ‐ a desirable effect in narrow‐gap welding. AC‐MIG weld metal further contains low oxygen, conferring high toughness. As a result, a narrow‐gap AC‐MIG welding process has been developed to ensure high efficiency in processing and metallurgically high‐quality welds in welding of 980 MPa high‐strength steels for penstocks (pressure shafts) in hydroelectric power stations. Welding wires with chemical compositions satisfying suitable strength and toughness criteria have been trial‐manufactured. Suitable welding parameters have also been determined for narrow‐gap welding of penstocks.     

Monitoring of expulsion in small scale resistance spot welding

Abstract

Although there have been many investigations into monitoring and control of resistance spot welding (RSW) of sheet metal having a thickness greater than 0.5 mm, that of thinner components has rarely been investigated. Monitoring of expulsion in a small scale RSW process was carried out via measurement of voltage, electrode displacement, and force change during the welding current pulse. It was found that electrode displacement increased steadily during the current pulse for an expulsion free weld. For welds with visible expulsion, the electrode voltage had a small but readily observed spike; the electrode displacement showed a dip or a decrease in total amplitude; the force change during a welding cycle was of greater magnitude. Since the system uses a constant current power supply, the voltage increase corresponds to an increase in dynamic resistance associated with the expulsion event. It was also observed that the magnitude of the electrode displacement dip was directly related to the volume of expelled material. The force change is a relatively sensitive indicator for use in expulsion detection. Of the three signals, detection of the voltage spike is the most readily implemented method for monitoring expulsion in small scale RSW. It was also shown that, owing to the small magnitudes of the forces and displacements, careful design of the welding system is necessary to ensure that unwanted vibrations do not interfere with the process signals.     

Pulsed arc welding with intermittent spray metal transfer by rectangular pulses

Special features of producing rectangular pulses from welding power sources with inverter transducers for the intermittent spray transfer of electrode metal are investigated. The methods for obtaining the required current pulse parameters ensuring the stability of consumable electrode pulsed arc welding in a mixture of the shielding gases 80% Ar + 20% CO₂ are discussed.     

脉冲电源双熔敷极焊条电弧焊焊缝熔深

脉冲电源应用于双熔敷极焊条电弧焊,采用正交试验研究分析脉冲参数对焊缝熔深的影响.结果表明,脉冲参数的变化引起焊缝熔深的相应变化,脉冲参数对焊缝熔深的影响程度由大到小的次序为峰值电流、频率、占空比、基值电流.在试验范围内获得较大熔深时的脉冲参数分别是峰值电流为230~240 A,频率为3.3~3.7 Hz,占空比为48%...