Development of high frequency pulse power source using two powersfor TIG welding

A high frequency pulse power source for TIG welding is developed. The structure of two powers is adopted. The by pass circuit effectively eliminates the effect of the cable equivalent inductance. The maximum frequency of the output pulse current reaches to 16 kHz . The base current and the peak current can be regulated separately.

A novel variable polarity welding power based on high-frequency pulse modulation

A new type of variable polarity welding power modulated with high-frequency pulse current is developed. Series of high-frequency pulse current is superimposed on direct-current-electrode-negative （DCEN）, which can improve the crystallization process in the weld bead as a result of the electromagnetic force generated by pulse current. Digital signal processor （DSP） is used to realize the closed-loop control of the first inverter, variable polarity output of the second inverter and high-frequency pulse current superposition.

Effect of variable polarity frequency on 2A14-T6 aluminum alloy welds using HPVP-GTAW process

Hybrid ultrahigh frequency pulse variable polarity gas tungsten arc welding （HPVP-GTAW） for 2A14-T6 high strength aluminum alloy was carried out and the effects of variable polarity frequency with constant pulse current frequency 40 kHz on weld bead geometry, microstrueture and microhardness were analyzed. Experimental results indicate that, compared to that of the conventional VP-GTAW process, the weld depth and ratio of weld depth to width are improved significantly by the variable polarity frequency in the HPVP-GTAW process, which the ratio of weld depth to width is improved by 36% at equal variable polarity frequency of 100 Hz, and improved by 55% with that of 200 Hz. Weld microstructure and microhardness distribution are changed obviously with the increase of variable polarity frequency. In the conventional VP-GTA W process, the grains in weld central zone are coarser, and the microhardness in weld central zone and fusion zone is about 95 HV and the lowest 82 HV, respectively. The microhardness is enhanced to a certain extent both in the weld central zone and fusion zone with the variation of variable polarity frequency in the HPVP-GTAW process due to the refinement and uniformity of weld microstructure. With the variable polarity frequency of 600 Hz, the microhardness in weld central zone and fusion zone reaches nearly 110 HV and 97 HV, respectively.

Effect of pulse frequency on hardness characteristics of Al-Cu alloy HPVP-GTAW joints

AA 2219-0 Al-Cu alloy single bead welds were obtained by hybrid ultrahigh frequency pulse variable polarity gas tungsten arc welding （HPVP-GTAW） process with pulse frequency varying from 25 kHz to 70 kHz. Weld hardness characteristics which mainly depicted by microhardness and its gradient were investigated systematically. The results show that pulse frequency has a great effect on the hardness characteristics. The weld zone microhardness and its gradient with different pulse frequency present an evident fluctuant trend. The fluctuation of gradient is slight, illustrating that the mierostructure is uniform with pulse frequcncy varied from 35 kHz to 60 kHz. The fusion zone microhardness and its gradient foUow the similar trends but fluetuate greatly. Maximum value of gradient appears around the fusion boundary due to the coarse and non- uniform microstrueture. The maximum gradient at 60 kHz is only 25.5 % of that at 45 kHz. According to the study, the best hardness characteristics are achieved at 60 kHz frequency.

Numerical simulation of applied electromagnetic field and electromagnetic force in all-position welding

All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to ＂push＂ the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.

A computer control system for automatic TIG welding of aluminium alloy sheets

Aimed at the welding ttechnological requirements of foe missile shell,a computer control system for automatic TIG welding of aluminium alloy sheets has been developed in this paper.The hardware of the system is composed of the four sub-systems,i.e.weldingpower source,arc length controller,welding wire feeder and welding head traveller.The software of the system comprises the on-line executing program and the off-line serving program.The operating principle,specifications and control of the system are introduced.The experiments indicate that the system possesses rational hardware structure and practical software function,and has solved the problem of high frequency interference to the computer control system. Therefore,the control system can satisfy the requirements of automatic TIG welding of the missile shell.

Investigation on the communication network of long wire transmitting in remote welding

According to the characteristics of remote welding, including multiple parameters, real-time, and reliability of long wire transmitting, a distributing computer control scheme is adopted. A serial communication network between the master and the slavery computers is constructed. A synchro-control network among slavery computers is designed. Uniform message format and communication protocols are made. Considering intensive high-frequency noises at the welding zone, a quadruple check mode, including data sum check, parameter type check, welding parameters check and Exclusive OR （ XOR ） check, is adopted to assure the reliability of communication among multiple computers. Based on disturbing circuit, common circuit and sensitive circuit, the measures are brought forward to ensure the stabilization of communication network of remote arc welding by analyzing the wiring principle of anti-high-frequency interference of system bus, signal wires and shielding twisted-pair（STP） wires. The results provide the theoretical and practical references for the manufacture of remote welding robot and the quality of remote welding.

热处理对薄壁TA1焊管高频感应焊接接头显微组织和力学性能的影响

首先对壁厚0.4 mm的薄壁TA1焊管进行高频感应焊接,随后,在不同温度下对焊接接头进行5 min的热处理。利用光学显微镜和扫描电镜分析了热处理前后焊接接头的显微组织,并对焊接接头的力学性能进行了测试。结果表明:热处理使TA1焊管焊接接头的显微组织和力学性能发生显著变化,当热处理温度为600℃时,焊接接头发生了完全再结晶,晶粒细小,抗拉强度略有下降,塑性增强,拉伸断口呈典型的韧性断裂特征,这主要是针状马氏体消失和细晶强化所致。

Inconel-52M焊丝高频脉冲TIG电弧及熔池流动行为研究

基于高速摄像机和图像处理技术,分析了脉冲频率(0~60 kHz)对焊接电弧和Inconel-52M镍合金焊丝熔池流动行为的影响及其作用规律.结果表明,在常规低频脉冲电流上复合高频脉冲电流会使电弧形态显著收缩,随着高频脉冲频率的增加,电弧弧根尺寸逐渐减小.与常规低频脉冲焊相比,高频脉冲电弧的整体面积减小,核心区面积及其占比增加,电弧能量集中度和温度(能量)得到提高.在高频脉电流的作用下,电弧轴向压强和径向电磁力增大,最大可分别提高18.0%和8.1%.电弧轴向电磁压强增大导致熔池流动性增强,使焊缝液态金属流动更充分,从而易形成大焊缝宽度和低润湿角的焊缝形貌.

Gleeble 3500热模拟HFW焊接工艺研究

采用Gleeble 3500实验机模拟了HFW焊接过程,研究了焊缝区金属挤出温度及其硬度和组织。结果表明:挤压形变量、挤压应力的波动变化主要与焊缝区金属挤出过程及焊后冷却过程中的相变有关;试验钢碳当量越高,焊缝区金属挤出开始温度就越高,终止温度就越低,不仅影响焊接质量,而且影响生产效率。

薄壁H65黄铜管高频感应焊接接头组织和力学性能

对薄壁H65黄铜高频感应焊接后的焊接接头微观组织和力学性能进行了研究。结果表明,利用高频感应焊接技术焊接H65黄铜管,获得了表面成型良好的焊接接头,实现了高质量焊接。焊接接头熔合区和热影响区均呈上下宽,中间窄的腰鼓状,焊接接头宽度约为173μm,其中熔合区宽约15μm,由大量细小的等轴状晶粒和少量条状晶粒组成,熔合区和热影响区的晶粒较母材得到细化。焊接接头抗拉强度为400 MPa,达到母材抗拉强度的97.6%,这是由于在拉伸变形过程中,晶粒的细化阻碍位错变形,且各晶粒间的位向差使位错相互交割,提高了焊接接头的强度,焊接接头断裂发生在热影响区,为韧性断裂,这是焊接过程中挤压辊的加工硬化与焊后退火软化共同作用影响热影响区力学性能所致。焊接接头显微硬度呈现“ʌ”形分布,熔合区平均硬度值为145HV,热影响区137HV,母材129HV,熔合区硬度较母材提高了16%,焊接时产生的加工硬化使熔合区强度得到提升。

HFW管高频感应加热过程电磁热耦合数值模拟

以提高直缝焊管质量为目的,重点研究了高频感应加热过程中热影响区的温度分布对焊缝质量的影响.针对高频感应加热的特点,对ANSYS有限元软件进行了二次开发,在应用物理环境法的基础上,利用APDL语言编制了直缝焊管高频感应加热过程中电磁热耦合的命令流程序,建立了三维有限元模型,分析了电磁场和温度场的分布规律.对某厂生产的219mm钢管模拟分析,综合考虑不同的磁棒分布形式对加热效率影响和自身冷却条件.结果表明,阵列式分布的小磁棒较好,这正是与生产实际相符合的.

超薄壁黄铜散热器扁管高频感应焊接接头的组织和性能

采用高频感应焊接技术对0.13 mm壁厚的H65黄铜扁管进行焊接,利用光学显微镜、扫描电镜、电子探针、电子背散射衍射、显微硬度仪以及拉伸实验对焊接接头的微观组织和力学性能进行了研究。结果表明:高频感应焊接H65黄铜扁管的焊接接头无裂纹、气孔等缺陷,焊缝区没有出现Zn的大量蒸发。焊接接头的抗拉强度达到400 MPa,达到母材的94%,伸长率为33.89%,与母材接近;焊接接头的显微硬度呈W型分布,熔合区最高,母材区次之,热影响区最小。焊接过程的挤压作用导致焊缝位错密度增加,产生加工硬化,是影响焊接接头硬度分布的主要原因;与母材相比,焊接接头的显微组织得到明显的细化,平均晶粒尺寸为1μm,是母材的50%,小角度晶界增加到了72%,大角度晶界下降到了28%,其中孪晶界下降到2%,进一步提高了焊接接头的力学性能。

中频退火装置感应线圈定位和焊缝跟踪系统在HFW焊管生产线上的应用

中频退火装置在焊管生产线上的作用较大,其感应线圈对焊管焊缝的热处理效果除了取决于中频电源的设计外,还与感应线圈是否有效定位在焊缝处有着密切的关系。介绍了一种中频退火装置感应线圈定位和焊缝跟踪系统在宝山钢铁股份有限公司HFW焊管生产线上的应用情况,该系统的设备组成结构、工作原理和功能使用要点,以及该系统进行钢管焊缝跟踪和根据产品规格进行线圈定位调整的方法。实际应用表明,该系统应用效果良好,具有一定的推广价值。

HFW508直缝焊管机组的技术先进性分析

FFX成型及定径、高频焊接、焊缝热处理、无损探伤等新技术和设备的开发并应用于中直径HFW钢管生产,促进了HFW钢管生产和技术的迅猛发展。中直径HFW钢管已在海上和陆上油气输送方面得到了广泛使用。近年来,X80钢级管线管及TUF油井管的问世,为中直径HFW钢管开辟了更广泛的应用领域。以华油钢管公司扬州分公司的HFW508直缝焊管机组为例,介绍了该类机组的技术特点及先进性。

TA1高频感应焊接头和基体在NaCl溶液中的电化学腐蚀行为

高频感应焊TA1薄壁管的焊接接头和基体在微观结构方面存在差异,电化学腐蚀行为往往是不同的。采用动电位极化技术和电化学阻抗谱(EIS),分析了TA1基体和焊接接头在不同浓度NaCl溶液中的电化学腐蚀行为。实验结果表明,随着氯离子浓度的增加,TA1基体和焊接接头的腐蚀电位呈负偏移,极化电阻逐渐减小,腐蚀速率增大。相比基体,焊接接头的腐蚀电位更高、极化电阻更大、腐蚀速率更低,表明耐腐蚀性能更好。实验可为高频感应焊TA1薄壁管在海水环境中的实际应用提供一定的理论依据。

高频脉冲微TIG焊接电弧基值效应研究

为了探索微TIG焊接的焊接电流下限,研制了一种高频脉冲微TIG焊接电源,利用脉冲基值电弧电特性的改善提高焊接稳定性。通过电弧电流、电压波形,分析了电弧的电压滞后性,探讨了脉冲频率对脉冲电弧基值效应的影响,并进一步对零基值脉冲TIG进行了研究。结果表明,高频脉冲下的微电弧基值电压较稳态电弧大幅下降,更有利于维持微电弧的燃烧;在基值电流为0 A的条件下高频脉冲电弧也可维持燃烧,平均焊接电流可低至0.5 A,极限0基值时间与脉冲电流大小呈正相关。对于微细漆包线和端柱的微型工件连接,零基值脉冲微TIG焊获得了较好的焊接效果。

宝钢610HFW焊管机组的现状与发展

介绍了宝钢610HFW焊管机组的产品定位、工艺流程及产品开发,包括结构管产品的规格和典型壁厚结构管拉伸性能、套管产品规格及其力学性能、管线管产品及其力学性能。结果表明,宝钢610HFW焊管机组已生产产品性能均达到或超过相关标准要求。

HFW焊管高温力学性能和热物理性能分析

针对某80钢级HFW焊管在井下作业过程中需承受不同高温下的服役环境,通过EBSD相机分析管体微观组织,测试获得了该焊管试样几个典型温度下的强度变化规律及弹性模量-温度曲线、热膨胀-温度曲线及导热系数-温度曲线等。结果表明,试样在300℃左右表现出较高的强度,在600~900℃时,杨氏模量和剪切模量降低速度较快;试样开始相变温度A_（c1）=759℃,相变转变结束温度A_（c3）=860℃,导热系数在700℃时出现极低值23.3 W/m·K。通过测试研究管体的高温力学性能和热物理性能,可为某80钢级HFW焊管在高温下的实际生产和井下安全服役提供作业参考。

中大直径HFW焊管高频接触焊接和高频感应焊接的比较

针对HFW焊管焊接采用的高频感应焊接(HFIW)和高频接触焊接(HFCW)两种焊接方式,从适用范围、能耗、产品质量成本方面作了比较。接触焊接最显著的优点就是能耗少,但质量成本比感应焊接要高;如果感应焊接配置得当,焊管厂家在成本和质量方面将取得最优化。