双旁路耦合电弧MIG焊工艺研究

为了实现高速焊接,一方面要减小对母材的热输入和电弧压力,同时还要增大通过焊丝的焊接电流,这是一个矛盾。双旁路耦合电弧MIG焊是在常规的MIG焊枪两旁分别增加一把TIG焊枪,通过旁路电极产生旁路电弧和旁路电流,分流一部分通过母材的电流,有效降低大焊接电流时的电弧压力,避免高速焊时焊缝成形缺陷的产生,较好解决了这一矛盾。进行了双旁路耦合电弧MIG焊(DB-MIG)工艺试验的研究。通过大量的焊接工艺实验,找到了合理的焊枪组合的几何参数。实验结果证明,该方法与常规MIG焊相比,在相同的焊接规范下,能够提高焊接速度,实现了高速焊接。     

旁路耦合电弧高效焊接工艺的数字化与智能化

旁路耦合电弧GMAW在实现提高焊丝熔敷率的同时减少了母材热输入,大幅降低电弧压力和熔滴射滴过渡的临界电流,实现高速焊接与异种金属间的焊接.近年来,兰州理工大学针对该方法展开了一系列研究,利用数字化模拟技术,采用多场全耦合方法,模拟了双旁路耦合电弧形态及热场、流场、电磁场的分布;模拟分析旁路耦合电弧脉冲GMAW在铝-钢异种金属焊接过程中,工件温度场的变化与接头界面上的原子扩散行为;建立了双丝旁路耦合电弧GMAW的数字化自动控制平台,并采用模糊控制算法实现了单闭环智能控制与双闭环解耦的智能控制.     

采用单电源双丝旁路耦合电弧高效GMAW方法的“碳钢-不锈钢”堆焊接头微观组织测试与分析

双丝旁路耦合电弧高效GMAW采用特定的接法,通过旁路电弧的分流作用可以实现高效、低热输入、低稀释率的焊接过程。采用该方法在Q235碳钢表面堆焊了耐磨、耐蚀的316L不锈钢材料,同时检测分析了不同焊接参数下的异种钢堆焊接头微观组织形貌,分析了旁路电流的变化对接头界面区碳元素迁移与焊缝合金元素稀释的影响。结果表明:随着旁路电流的增加,对接头焊接质量影响较大的界面处碳迁移层厚度明显减小,焊缝中合金元素稀释的过渡区域宽度也显著降低。     

铝/钢异种金属MIG熔钎焊接头腐蚀性能研究

采用脉冲旁路耦合电弧(DE-GMAW MIG)熔钎焊和ER5356铝合金焊丝对1060铝/Q235镀锌钢异种金属进行了搭接焊。用浸泡腐蚀试验和电化学腐蚀试验对焊接接头的腐蚀行为进行了研究,分析了焊接热输入对焊接接头腐蚀性能的影响。通过SEM并结合EDS对接头的腐蚀形貌和表面腐蚀产物进行了观察与分析。结果表明:铝/钢焊接接头处出现了显著的电偶腐蚀,且随着焊接热输入的增大,焊接接头的耐腐蚀性能下降。铝/钢焊接接头界面反应层金属间化合物的形成对铝/钢焊接接头的腐蚀性能是不利的,应尽量避免形成过多的界面层金属间化合物。     

几种铝钢异种金属熔钎焊工艺的对比与分析

采用脉冲旁路耦合电弧MIG焊、CMT及激光焊方法实现铝/镀锌钢板搭接焊,对焊缝界面微观组织、形貌及元素成分进行了观察分析,并测试了其力学性能.结果表明,三种焊接方法均可以实现铝/镀锌钢板异种金属的优质连接,获得成形良好的焊缝,搭接接头的抗拉剪强度均可以达到铝合金母材的80%以上,拉伸试样断裂在焊缝铝合金母材热影响区.当母材热输入及工艺合适时,三种方法下搭接接头界面处均形成一主要成分为Fe₂Al₅和FeAl₃,平均厚度约为8 μm的金属间化合物,而且控制金属间化合物的生成是获得铝/钢焊接优质接头的关键.     

304不锈钢MIG、激光和激光-MIG复合焊接工艺对比研究

采用MIG焊、激光焊、激光-MIG复合焊分别在5 mm厚304不锈钢板上进行堆焊,对比分析三种焊接方式下焊接接头的宏观形貌和显微组织。试验结果表明,激光-MIG复合焊接中激光与电弧两热源叠加并产生复合作用,焊缝兼有MIG焊和激光焊的形貌特征,其中MIG电弧主要作用在复合焊熔池的上部,具有MIG焊焊缝大熔宽、浅熔深特征,激光热源主要作用于复合焊熔池的下部,具有激光焊焊缝大深宽比特征。因为热源的复合作用,激光-MIG复合焊接拥有比单MIG焊接和激光焊接更好的桥接能力、成形能力和组织性能。     

双丝旁路耦合电弧高效MIG焊方法及控制系统

提出了新型双丝旁路耦合电弧MIG高效焊接方法,理论分析证明其有利于高效焊接过程,但焊接试验表明该方法在开环情况下焊接过程极不稳定,焊缝成形差.分析了双丝旁路耦合电弧开环不稳定的原因,提出了双丝旁路耦合电弧MIG焊闭环控制方法,采用基于xPC实时目标机技术建立了双丝旁路耦合电弧控制硬件系统,运用Mat-lab/Simulink工具开发了其控制系统的快速原型.结果表明,模糊控制器的控制效果可以满足稳定焊接的要求.在此基础上进行了高效焊接试验,与传统MIG焊方法相比可大幅提高焊接效率.     

铝合金激光-小功率脉冲MIG电弧复合热源焊接特性分析

针对5A06铝合金,通过一系列对比数据综合分析了MIG焊和激光MIG复合热源焊接技术在焊缝熔深、焊缝成形、焊接速度、焊接热输入等方面的优缺点.结果表明,在MIG平均电流小于200 A的小功率脉冲MIG电弧区域内,等热输入且等焊接速度条件下,激光-MIG复合热源焊接技术与MIG相比可以提高焊缝深宽比1～2倍,增加焊缝熔深0.43～2.5倍;等热输入且等平均焊接电流条件下,与MIG相比,激光MIG复合热源焊接技术可以提高焊接速度0.6～1.5倍,增加焊缝熔深0.5～5.9倍;激光MIG复合热源焊接技术可以用高于MIG焊0.6～6.5倍的焊接速度和更小的焊接热输入获得与MIG同样的焊缝熔深;与MIG焊相比,激光MIG复合热源焊缝的铺展性更好,更适合于高速焊接;MIG复合2 kW的激光能量后会增加平均电弧电压、减小平均电流.     

焊接工艺参数对搭接接头形状及力学性能的影响

调查了焊接工艺参数对不锈钢搭接接头形状和力学性能的影响。对于1.5mm厚的304不锈钢薄板MIG焊搭接接头,焊接电流过小,搭接接头的承载能力很低;焊接电流过大,会导致焊件熔穿。过快的焊接速度会导致产生咬边。与焊接速度相比,不正确地设置焊接电流所带来的负面影响要更大一些。无论是改变焊接电流,还是调整焊速,确保焊件熔透是保证MIG焊搭接接头力学性能的关键。     

双丝旁路耦合电弧MIG焊嵌入式控制系统设计及实现

设计并实现了双丝旁路耦合电弧MIG焊嵌入式控制系统,并进行了控制试验.控制系统包括:主控板、送丝控制板和焊接参数显示模块,系统以32位ARM7微控制器LPC2124为基础,可采集并显示焊接参数,控制旁路弧长,控制母材电流.三块电路板之间采用基于RS-485接口和Modbus协议的总线结构连接,可进行数字化通信.通过控制试验表明:该嵌入式控制系统可以对旁路电弧和母材电流进行控制,满足双丝旁路耦合电弧MIG焊的控制需求,使得焊接过程稳定进行,并得到成形良好的焊缝.     

CO2 laser-micro plasma arc hybrid welding for galvanized steel sheets

A laser lap welding process for zinc-coated steel has a well-known unsolved problem-porosity formation. The boiling temperature of coated zinc is lower than the melting temperature of the base metal, which is steel. In the autogenous laser welding, the zinc vapor generates from the lapped surfaces expels the molten pool and the expulsion causes numerous weld defects, such as spatters and blow holes on the weld surface and porosity inside the welds. The laser-arc hybrid welding was suggested as an alternative method for the laser lap welding because the arc can preheat or post-heat the weldment according to the arrangement of the laser beam and the arc. CO₂ laser-micro plasma hybrid welding was applied to the lap welding of zinc-coated steel with zero-gap. The relationships among the weld quality and process parameters of the laser-arc arrangement, and the laser-arc interspacing distance and arc current were investigated using a full-factorial experimental design. The effect of laser-arc arrangement is dominant because the leading plasma arc partially melts the upper steel sheets and vaporizes or oxidizes the coated zinc on the lapped surfaces. Compared with the result from the laser-TIG hybrid welding, the heat input from arc can be reduced by 40%.     

铝合金/镀锌钢板脉冲MIG电弧熔-钎焊接头组织与性能

采用数字化脉冲MIG焊机,以ER4043焊丝为填充材料.实现了6013-T4铝合金薄板与镀锌钢板的熔-钎焊接,研究了焊接热输入对接头组织和性能的影响,结果表明,在熔-钎焊接头熔化焊缝焊趾处存在主要由Zn-Al共晶体、富A1的α固溶体和Fe3Al组成的富Zn区:钎焊界面上的Fe-Al金属间化合物层厚度在1.05-4.50μm之间.且随焊接热输入的增加而增大.Fe-Al金属间化合物呈"锯齿"或"舌"状向焊缝内生长,主要为FeAl₂,Fe₂Al₅和Fe₄Al₁₃.随着焊接热输入的增大,熔-钎焊接头的抗拉强度先增大而后减小.在850 J/cm的热输入下达到229 MPa,拉伸后在铝合金焊接热影响区发生断裂,为塑韧性断裂;当焊接热输入较小时接头在钎焊界面断裂,属于脆性断裂.     

Improving the accuracy of calculating the conditions of mechanized surfacing

For some years now, the light engineering sector has been in search of welding and/or joining technologies allowing high-speed processing at low temperatures. This way, damage to galvanized coating, for example in the case of steels, could be avoided or significantly reduced.

Damage to the galvanized coating represents an outwardly visible phenomenon that can have a negative impact on the component's corrosion resistance.

On the other hand, from the metallurgical viewpoint, controlling heat input represents an important way to solve the problems associated with heat joining of metals with incomplete solid-state solubility. The formation of fragile intermetallic phases during cooling, for example, occurs with aluminium/steel or aluminium/titanium. The process and the correct choice of filler materials are key points for the success of the joining method. In the case of the combination of aluminium and steel, zinc represents a suitable filler material, for example for brazing. The melting temperature is around 420°C and the wettability, with regard to galvanized steel, is favoured by the zinc layer, while on the aluminium part, it is possible to avoid the use of flux, thanks to the activating action of the voltaic arc. However, the low melting and vaporization temperatures of zinc make even ‘short arc’ processing rather difficult.

Only new developments in electrical sources for welding, and in particular new processes, offer the possibility of reducing the heat input by modifying the ‘short arc’ process. The difficulties described are also valid for the combination of titanium and aluminium, and are associated with the formation of phases such as Ti _x A1 _y . Again in this case, this paper will present a strategy for joining sheets less than 2 mm thick.

In the past years, an increasing number of strategies to join zinc-coated steels can be observed. Brazing represents a profitable way to join zinc-coated steels at low temperatures, reducing or avoiding zinc evaporation.

In order to completely avoid damaging zinc coating, the set of ZnAl-fìllers was already investigated for laser brazing of zinc-coated steels as well as for joining steel with aluminium.

Furthermore, thanks to new developments in arc wire technology, ZnAl-electrodes can be used for MIG-brazing as well. In this case, the conventional short arc, which normally does not allow brazing with zinc wires as eruption-like evaporation occurs, is modified and controlled. The drop formation on the wire tip, the metal transfer, and the heat input can be controlled and modified very precisely, so that processing of filler material can be performed easily for thin sheets (till 0.8–1.5 mm) and at low-processing speed, below 0.3–0.4 m/min. The control of the heat input occurs due to abruptly reducing the current after short arc.

The disadvantages connected with a lower heat input in the base material are a restricted wetting behaviour of the zinc pool on the base material and the low-brazing speed due to a very high cooling rate. The focus of the presented investigation is the development of strategies, in order to enhance process conditions for brazing sheets of zinc-coated steels and aluminium.     

Arc weldability of zinc coated steel sheets

Summary

CO₂ arc fillet welding of lap joints in zinc coated steel sheets and Zn-Fe coated steel sheets produced from base metals with a different surface roughness is performed to clarify the relationship between the properties of zinc coating layers and the factors affecting the generation of pits and blowholes during arc fillet welding of lap joints in zinc coated steel sheets. The results show that the generation of pits and blowholes is sharply reduced with a decreasing Fe content in the zinc coating layer and the decreasing surface roughness of the base metal. A reduction in the Fe content of the zinc coating layer decreases the melting point of the zinc coating layer, causing the zinc coating layer to melt faster and enabling the molten zinc to escape faster from the molten pool. A reduction in the surface roughness of the base metal increases the mobility of the molten zinc on its surface near the molten pool. When zinc coated steel sheets with a zinc coating weight of 40 g/m² produced from smooth surface base metal (Ra = 0.1 μm) were welded at a welding speed of 1.0 m/min, the generation of pits and blowholes was strongly suppressed to the same level as found during corresponding welding of cold-rolled steel sheets.     

Hybrid Laser-GMAW Welding of High Strength Quenched-Tempered Steels

High-strength quenched and tempered (HSQT) steels have been widely used in structural applications where light weight is of primary design interest.Gas metal arc welding is a common way to join QT steels.When GMAW is used to join the HSQT steel,multi-pass is usually required to achieve full penetration.In addition,weld crack is often observed because of HSQT steel’s high susceptibility to hydrogen embrittlement.In addition,due to the large amount of heat input from the arc,the heat affected zone is often softened.This reduces the ductility and strength of welds and makes the weld weaker than the base metal.In this study,a hybrid laser/GMAW process is proposed to produce butt joint for 6.5mm thick HSQT A514 steel plate.Hydrogen diffusion mechanism is first discusses for GMAW and hybrid laser-GMAW welding processes.Metal transfer mode during the hybrid laser/GMAW welding process is also analyzed.A high speed CCD camera with 4000 frame/second is used to monitor the welding process in real time.Welds obtained by GMAW and hybrid laser/GMAW techniques are compared and tested by static lap shear and dynamic impact.Effects of gap between two metal plates and laser beam/GMAW torch spacing on weld property are studied.By appropriately choosing these two parameters,crack-free butt joints with full penetration can be successfully obtained by the hybrid laser/GMAW welding process for HSQT A514 steel plate.     

高Nb X80管线钢焊接热影响区显微组织与韧性

为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊. 采用夏比冲击试验和金相分析方法,研究热影响区的微观组织差异和夏比冲击韧性. 并借助扫描电镜和超高温激光共聚焦显微镜分析不同Nb含量X80管体的微观组织对热影响区性能的影响. 结果表明,在0 ℃和−20 ℃时,0.075%Nb和0.055%Nb的X80钢管GMAW环焊接头热影响区均具有较高的冲击韧性,其平均冲击吸收能量均高于150 J. 其中0.055%Nb略高于0.075%Nb的GMAW环焊接头热影响区夏比冲击吸收能量;焊接热输入较低时,0.055%Nb低于0.075%Nb的X80环焊接头粗晶区的韧脆转变温度,具有更好的低温韧性. 焊接热输入较高时,0.075%Nb的X80环焊接头粗晶区具有更高的上平台冲击吸收能量,且上平台温度和韧脆转变温度也更低,其低温韧性也更优异;还发现了X80环焊接头热影响区的冲击韧性不仅与热输入量和热影响区马氏体−奥氏体组织(M-A)的形状、大小、分布有关,而且还受管体中Nb含量、原始的强度与韧性、微观组织状态的遗传影响.

     

Corrosion Behavior of MIG Brazed and MIG Welded Joints of Automotive DP600-GI Steel Sheet

Galvanized dual-phase steel sheets are extensively used by the auto industry for their corrosion resistance property. Welding by the metal inert gas (MIG) process causes degradation of the steel in the vicinity of the joint due to excessive zinc evaporation. In order to minimize Zn loss, the MIG brazing process has been tried out in lap joint configuration over a heat input range of 136–204 J mm^?1. The amount of zinc loss, intermetallic formation and corrosion properties in the joint area has been evaluated for both MIG brazing and MIG welding. Corrosion rate of 21 mm year^?1 has been reduced to 2 mm year^?1 by adopting MIGB in place MIGW. Impedance study has shown that the corrosion mechanism in base metal, MIG brazed and MIG welded joints is dominated by charge transfer, diffusion and mixed mode control processes, respectively.     

Quantitative characterization of porosity in Fe–Al dissimilar materials lap joint made by gas metal arc welding with different current modes

5052 Al alloy sheets and galvanized mild steel sheets were joined by gas metal arc welding with three different current modes, including direct-current pulse gas metal arc welding (DPG), alternate-current pulse gas metal arc welding (APG) and alternate-current double pulse gas metal arc welding (ADG). The effect of current mode on size, distribution and volume fraction of pores generated in Fe–Al dissimilar materials lap joint was quantitatively studied. EDS result showed that pores in Fe–Al joint were mainly caused by trapped zinc metal vapor from galvanized steel. Volume fraction of pores in joints made by APG and ADG processes was larger than that in joint resulted from DPG process. Moreover, pores in joints made by APG and ADG processes had smaller diameter, and tended to distribute in the middle of the weld seam. On the contrary, pores with large diameter were inclined to distribute close to upper weld surface of the joint resulted from DPG process. These results are attributed to the difference of arc stirring force and linear heat input in these three processes caused by different current modes.     

Join Al–steel dissimilar metal by novel high frequency electric cooperated arc welding

ABSTRACT

A novel high frequency electric cooperated arc welding method (HFAW) was developed to join aluminium and steel of 3.0?mm thickness without groove. Owing to the skin effect and proximity effect of high frequency current, a part of welding heat was directly distributed all over weld side wall. Consequently, sound double-sided weld formation was achieved under a low MIG heat input and high welding speed. The average thickness of interfacial layer was limited to 2.3?µm. Benefitted from the balanced heat input and thin interfacial layer, the failure mode of the HFAW joint was necking at Al base metal. For traditional MIG joint, however, poor back weld formation and thick interfacial layer resulted in spontaneous fracture at interface.