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Mechanism of Metal Transfer in DE-GMAW

Kehai Li

材料科学技术(英)

Modification of conventional gas metal arc welding (GMAW) process is of great potential to achieve high productivity with low cost and strong usability. Double-Electrode GMAW (DE-GMAW) is such a modified arc welding process which is formed by adding a bypass torch (gas tungsten arc welding torch) to a conventional GMAW system. The mechanism of metal transfer in DE-GMAW was proposed and verified in this paper. Experiments show that the critical current is decreased so that spray transfer can be obtained at a lower current level in DE-GMAW. Analysis of this significant change in metal transfer phenomena is conducted, and explanation is given out. It is found that the bypass arc in DE-GMAW lifts the anode point on the droplets such that the electromagnetic force becomes larger and squeezes the droplets so that spray transfer can take
place under welding current lower than that in conventional GMAW.

关键词: Metal transfer , null , null

Properties of ZnO : Al films on polyester produced by de magnetron reactive sputtering

Materials Letters

High preferred (002) orientation Al-doped ZnO (ZAO) films have been prepared by de magnetron reactive sputtering of an alloy target (98.5 wt.% Zn-1.5 wt.% Al) onto polyester substrates. The structural, mechanical, electrical and optical properties were investigated. The ZAO film has a sheet resistance of as low as 47.5 Omega/square and an average visible transmittance of about 70%. An average IR reflectance of about 70% in the region of 2.5-25 mum also has been obtained. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词: Al-doped ZnO (ZAO);polyester;mechanical;IR reflectance;thin-films;optical-properties;oxide-films;electrical-properties;rf;temperature;orientation;parameters;deposition;substrate

Formation of Al-doped ZnO films by de magnetron reactive sputtering

Materials Letters

Highly preferred (002) orientation transparent conductive Al-doped ZnO (ZAO) films were successfully prepared by de magnetron reactive sputtering from a Zn target mixed with Al of 2.0 wt.%. The film has a resistivity of 4.80 X 10(-4) n cm and a visible transmittance of as high as 90%. XPS analysis indicates Al-enrichment on the film surface. The asymmetry of Al 2p(3/2) XPS peak is resolved into two components: one centering at 72.14 eV attributed to metallic Al and the other having a binding energy of 74.17 eV due to oxidized Al. (C) 2001 Elsevier Science B.V. All rights reserved.

关键词: Al-doped;ZnO;XPS;Al-enrichment;oxide thin-films;optical-properties;electrical-properties;rf;dc;transparent;deposition

DE-GMAW高速电弧焊工艺机理的研究

武传松 , 张明贤 , 李克海 , 张裕明

金属学报 doi:10.3321/j.issn:0412-1961.2007.06.021

通过大量的工艺实验,找出了DE-GMAW双焊枪组合的匹配参数,测试了焊接电流波形,拍摄了熔滴过渡图像,并获得了无成型缺陷的焊缝照片.基于实验结果解释了高速焊接工艺的机理.建立了适用于DE-GMAW焊接工艺的有限元模型,并对该工艺条件下的温度场、应力-应变场进行了数值模拟.结果表明:计算出的DE-GMAW焊缝横断面形状尺寸与实验结果吻合良好;在通过焊丝的总电流相同时,DE-GMAW焊接时焊缝尺寸、热影响区宽度、应力、应变及变形均小于常规GMAW焊时的结果.这为DE-GMAW焊接工艺参数优化提供了基础数据.

关键词: 高速电弧焊接 , 工艺机理 , DE-GMAW , 有限元分析

Mechanism of Embrittlement and De-Embrittlement for 225Cr-1Mo Steel

ZHANG Xi-liang , ZHOU Chang-yu

钢铁研究学报(英文版)

The constant embrittlement curve for constant segregation concentration on grain boundary of impurity element P and relationship between equilibrium grain boundary segregation concentration and operation time for 225Cr-1Mo steel were derived based on the theory of equilibrium grain boundary segregation. The mechanism of step-cooling test and mechanism of de-embrittlement for 225Cr-1Mo steel were explained. The segregation rate will increase but equilibrium grain boundary segregation concentration of impurity element P will decrease as temperature increases in the range of temper embrittlement temperature. There is one critical temperature of embrittlement corresponding to each embrittlement degree. When the further heat treating temperature is higher than critical temperature, the heat treating will become a de-embrittlement process; otherwise, it will be an embrittlement process. The critical temperature of embrittlement will shift to the direction of low temperature as further embrittlement. As a result, some stages of step-cooling test would change into a de-embrittlement process. The grain boundary desegregation function of impurity element P was deduced based on the theory of element diffusion, and the theoretical calculation and experimental results show that the further embrittlement or de-embrittlement mechanism can be interpreted qualitatively and quantitatively by combining the theory of equilibrium grain boundary segregation with constant embrittlement curve.

关键词: step-cooling test , critical embrittlement temperature , embrittlement mechanism , grain boundary desegregation

DE-GMAW高速电弧焊工艺机理的研究

武传松 , 张明贤

金属学报

根据当前制造业对高效、优质、低耗焊接技术的迫切要求,研发出低成本的高速电弧焊接新工艺DE-GMAW。该工艺在常规GMAW焊接设备的基础上,通过附加GTAW焊枪构成旁路电弧,分流了一部分通过焊丝的焊接电流,在施加于焊丝的电流较大的情况下(保证了熔敷率),减小了作用于母材的热输入,解决了高速焊接面临的矛盾,实现了高速电弧焊接。建立了适用于DE-GMAW焊接工艺的有限元模型,并对该工艺条件下的温度场和应力变形进行了数值模拟。结果表明:计算出的DE-GMAW焊缝横断面形状尺寸与实验结果吻合良好;在通过焊丝的总电流相同时,DE-GMAW焊接时焊缝尺寸、热影响区宽度、应力、应变及变形均小于常规GMAW焊时的结果。这为DE-GMAW焊接工艺参数优化提供了基础数据。

关键词: 高速电弧焊接 , process mechanism , DE-GMAW , finite-element analysis

DE-81(3)型碱性锌酸盐镀锌工艺的应用

王朝铭

电镀与涂饰 doi:10.3969/j.issn.1004-227X.2005.04.014

DE-81(3)型碱性镀锌工艺具有单位面积电流密度大、生产效率高,镀液对金属杂质的容忍量大等优点.介绍了该镀锌工艺的生产流程和工艺配方,及其钝化工艺配方;各成分的用量范围及其作用.详细说明了镀液维护的要点.采用DE-81(3)型碱性镀锌工艺大批量处理多品种、尺寸不一、形状各异的零件,经过多年的生产实践和抽样检测结果,镀层外观、附着力、厚度和耐盐雾试验均达到国家标准.

关键词: 锌酸盐镀锌 , 应用

非线性电活性绝缘弹胶物DE的应变能模型材料常数

祁新梅 , 宗志坚 , 郑寿森

高分子材料科学与工程

应用Mooney-Rivlin、Yeoh和Ogden应变能模型研究DE材料驱动建模。首先根据单轴拉伸实验数据,分析文献中的材料常数和本文DE材料的适合程度,发现文献中的材料常数均不适合本试验中的绝缘弹胶物(DE)材料变形特性;进一步根据试验数据及理论模型回归分析求出适合本试验变形范围内的DE材料的材料常数。结果表明,Mooney-Rivlin模型不能很好地反映非线性特征,Yeoh和4参数及6参数的Ogden模型均能反映DE材料的非线性特征。

关键词: 电活性聚合物 , 绝缘弹胶物 , 类天然肌肉 , 应变能模型

铝-镀锌钢板异种金属Pulsed DE-MIG熔钎焊方法研究

顾玉芬 , 邵玲 , 石玗 , 黄健康

材料科学与工艺

为精确控制焊接热输入,从而控制铝钢异种金属界面区金属间化合物生长,提出一种新型高效低热输入的脉冲旁路耦合电弧MIG焊(Pulsed DE-MIG)方法,用ER5356铝合金焊丝在镀锌钢板上利用平板堆焊实验对工艺参数进行优化。在焊丝总电流保持不变,不同的Pulsed DE-MIG焊接参数下焊接,结果表明随着旁路电流的增大,焊缝宽度显著变小,且焊缝堆高明显变高。采用OM、SEM、EDS等测试手段观察和分析连接界面区的微观组织,发现在连接界面区形成Fe2 Al5、FeAl3金属间化合物层,且母材热输入大时,FeAl3析出得多,随着母材热输入的减小,FeAl3析出逐步减少直至FeAl3无析出。

关键词: 脉冲旁路耦合电弧MIG焊( Pulsed DE-MIG) , 铝-镀锌钢板异种金属焊接 , 母材热输入 , 金属间化合物

Shubnikov-de Haas effect and magnetic breakdown in the low-temperature charge-density-wave state for the thallium purple bronze TlMo6O17

Physical Review B

Magnetoresistance has been studied for quasi-two-dimensional thallium purple bronze T1Mo6017 at a temperature of 4.2 K in fields up to 12 T. Shubnikov-de Haas oscillations are observed. The calculated Fermi surface size is about 5x10(-4) in the high-temperature Brillouin zone and consistent with hidden Fermi surface nesting theory. The field dependence of magnetoresistance is studied in the vicinity of magnetic breakdown. The characteristic field of breakdown is around 0.08 T corresponding to an energy gap of about 2 meV. The effective mobility and cyclotron mass are about 0.025 m(2) V-1 s(-1) and 0.3m(e), respectively.

关键词: molybdenum bronzes;instability

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