镀锌钢-6016铝合金激光焊接组织性能与第一性原理计算

采用基于密度泛函理论的第一性原理方法,计算Fe8Al8及(Fe7X)Al8(X=Pb,Sn,Ti,Cu,Mn,Si,Zn)超胞模型的弹性模量与电子结构,在分析合金化元素改善FeAl金属间化合物力学性质的基础上,选取降低脆性效果较好的Cu和最好的Pb,对1.2 mm厚DC56D+ZF镀锌钢和1.15 mm厚6016铝合金平板试件进行加入中间夹层Cu和Pb的激光搭接焊试验。结果表明:FeAl金属间化合物为脆性相,其电子结构根源在于Fe的sd态与Al的sp态存在电子轨道杂化,为明显的共价键特征;FeAl合金化后,脆性降低,相应脆性由低到高的顺序为(Fe7Pb)Al8、(Fe7Sn)Al8、(Fe7Ti)Al8、(Fe7Cu)Al8、(Fe7Mn)Al8、(Fe7Si)Al8、(Fe7Zn)Al8、Fe8Al8,Pb合金化降低脆性效果最好,激光搭接焊加入中间夹层Pb,钢侧母材与焊缝界面区由母材侧较大晶粒和焊缝的细小晶粒交错形成,熔池金属与母材铝之间没有明显的分界线,焊接接头界面熔合良好;与未加夹层相比,加入中间夹层Cu和Pb后,焊接接头力学性能提高,其中Pb的作用优于Cu的,试样断口均具有韧性断裂特征。     

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.     

镀锌钢一6016铝合金异种金属加入中间夹层铅的激光焊接

对1．2mm厚镀锌钢板和1．15mm厚6016铝合金平板试件进行了加入中间夹层铅的激光搭接焊试验,通过调整焊接工艺参数获得最佳焊接成形,利用卧式金相显微镜、扫描电镜、x射线衍射、微机控制电子万能试验机等手段研究了焊接接头各区域的金相组织、断口形貌、主要物相与接头力学性能．结果表明,在钢／铝激光焊中添加中间夹层铅,焊接接...     

Effect of welding speed on microstructural and mechanical properties of laser lap weld joints in dissimilar Al and Cu sheets

Conventional fusion welding of aluminium and copper dissimilar materials is difficult because of poor weldability arising from the formation of brittle intermetallic compounds on the weld zone as well as different chemical, mechanical and thermal properties of welded joints. Joining of Al and Cu plates or sheets offers a metallurgical challenge due to unavoidable formation of brittle intermetallic compounds. Therefore, it is necessary to effectively suppress the formation and growth of Al–Cu intermetallic compounds. For welding of dissimilar Al and Cu sheets, no systematic work has been conducted to reduce these defects. Thus, this paper focuses on the effect of welding speed on the quality of a lap weld joint in the Al and Cu sheets with a single mode fibre laser. It was found that consequently sound strong weld joints could be produced by suppressing the formation of intermetallic compounds in the interface zone at extremely high speeds.     

高匹配搭接角焊缝力学性能及应用效果分析

采用等匹配和高匹配焊材完成了高钢级B型套筒修复高钢级管道的试验研究. 结果表明,等匹配焊接和高匹配焊接的角焊缝焊接接头都具有良好的拉伸强度和冲击韧性,高匹配焊接接头熔覆金属的冲击韧性略低于等匹配,其焊接接头延展性略差;施焊后等匹配搭接角焊缝未发现焊接缺陷,焊接接头维氏硬度最大值为293 HV10,出现在角焊缝外表面与套筒搭接焊缝处;高匹配搭接角焊缝出现了起源于角焊缝外表面层的横向裂纹,且该焊接接头硬度整体偏高,最大值出现在外表面中心位置焊缝处,为403 HV10,与裂纹起裂位置对应,其产生原因与焊接过程中不同部位熔池金属冷却速率有关,尤其是外表面盖面焊处冷却速度较快,外壁层硬度值异常偏高,萌生裂纹.因此建议搭接角焊缝焊接焊材选择时,在不影响密封和承载前提下,可尝试降低焊缝匹配强度等级.     

Microstructural and mechanical characteristics of laser welding of Ti6Al4V and lead metal

Titanium alloy Ti6Al4V and lead metal were welded using a continuous wave Nd:YAG laser. The influences of laser power, scanning velocity, and laser beam offset on weld morphology were investigated. Microstructure, chemical composition and mechanical properties of the joints were evaluated. Experimental results showed that fusion weld formed at the upper part of the weld and brazing weld with solder of Pb formed at the lower part of the weld under appropriate process condition. Interfaces were formed between mixed fusion zone and liquid lead zone in molten pool during laser welding of Ti6Al4V and lead. Reasons for interface formation may be different driving force of various regions in molten pool, and the miscibility gap of Ti and Pb binary system. Ti-Pb intermetallic compound Ti₄Pb was detected at the fusion weld zone, which made the microhardness of the weld seam was higher than that of the base materials. The strength of the joint was at least equal to or larger than that of lead base material.     

镀锌钢/铝添加中间夹层Cu、Pb的激光搭接焊研究

对1.2 mm厚DC56D+ZF镀锌钢和1.15 mm厚6016铝合金平板试件进行了添加中间夹层Cu、Pb的激光搭接焊实验研究,利用体视显微镜、卧式金相显微镜、扫描电镜、X射线衍射仪、微机控制的电子万能试验机等手段研究了钢/铝焊缝的表面成形性、接头各区域的金相组织、界面元素分布、断口形貌、主要物相与接头力学性能。结果表明:添加中间夹层Cu、Pb,焊接接头的平均抗拉强度分别为49.44、73.51 MPa,伸长率分别为1.63%、2.37%,与未添加夹层相比,抗拉强度和伸长率提高,其中Pb提高效果优于Cu;不加夹层,钢/铝试样断口呈明显脆性断裂特征;加入夹层Cu,脆性断裂特征不明显;而加入夹层Pb,试样断口呈韧性断裂特征;添加夹层Pb,钢/铝界面连接处Fe、Al、Zn、Mg、Pb元素变化剧烈,混合区宽度大,新生成Mg2Pb金属间化合物的结构比FeAl金属间化合物稳定,能抑制脆性FeAl金属间化合物生成。这是添加夹层Pb明显改善钢/铝焊接接头力学性能的重要原因。     

Ni/Si中间层对铝/钢激光焊接头组织与性能的影响

研究了以Ni箔以及预置Si粉的Ni箔为中间层的铝/钢异种金属激光焊行为. 系统考察了不同激光功率下预置Si粉的Ni箔中间层对铝/钢异种金属激光焊接头组织与性能的影响. 结果表明,加入预置Si粉的Ni箔做复合中间层时,与只添加Ni箔片做中间层时相比,焊接接头的最大剪切力明显提高,其中激光功率为2 150 W时焊接接头的最大剪切力提高至1 307.96 N;Si粉的添加增加了熔池的流动性,并使得铝/钢界面的物相组成、元素分布和微观组织形态发生了改变;焊缝区生成了Fe-Si及Al-Si二元新相,有效抑制了Fe-Al二元脆性相的生成,改善了铝/钢的焊接性. 因此,预置Si粉的Ni箔复合中间层的加入,可以有效地改善铝/钢异种金属激光焊过程中的冶金反应,进而提高焊接接头的力学性能.     

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.     

铝合金/镀锌钢板Nd:YAG激光+MIG电弧复合热源熔-钎焊接头的组织与性能(英文)

基于铝合金和镀锌钢在熔点上的差异,以ER4043(AlSi5)为填充材料,采用大光斑Nd:YAG激光+MIG电弧复合热源焊接工艺实现两者的熔-钎焊接,研究熔钎焊接头组织和性能。铝合金/镀锌钢板熔钎焊接头分为熔焊接头和钎焊缝两部分,熔焊缝组织由α(Al)等轴晶和晶界上短棒状的Al-Si共晶组织组成,焊趾处的富锌区为α-Al-Zn固溶体和Al-Zn共晶组织。钎焊缝为Fe-Al金属间化合物层,厚度为2~4μm,金属间化合物包括FeAl2、Fe2Al5和Fe4Al13,其中FeAl2和Fe2Al5位于近钢侧的紧密层,而Fe4Al13则呈舌状或锯齿状向熔焊缝内生长。接头抗拉强度随着焊接电流和激光功率的增大呈先增大后减小的趋势,最高可达247.3 MPa。拉伸断裂位置一般位于熔焊缝的熔合区,为以韧性断裂为主的混合断裂。接头内硬度的最大值位于钎焊缝处,然后分别沿着两侧钢板和铝合金熔焊缝逐步降低。     

Evolution of bond formation and fracture process of ultrasonic spot welded dissimilar materials

Ultrasonic spot welding was applied for dissimilar lap welding of aluminium alloy and steel sheets. With a combination of heat and force input during the welding process, the welded interface at aluminium/steel interface was formed. A graphical model was established to represent the weld formation process. The thickness of top aluminium sheet was reduced with an increase in welding time, which led to the failure mode switching from debonding failure to pullout failure. The intermetallic at the welded interface was verified by energy-dispersive X-ray spectroscopy on the surface of the fractured specimen. In addition, the vibration direction of the sonotrode during ultrasonic spot welding influenced joint strength by changing the alignment of micro bonds at the welded interface.     

Effect of Al coating conditions on laser weldability of Al coated steel sheet

Al coated steel sheets with excellent heat resistance, thermal reflection, and corrosion resistance are widely used in various applications. The laser weldability of the Al coated steel sheet for full penetration welding was reported. The phenomenon caused by intermixed aluminum and behavior of aluminum in the weld were investigated. Al coated steel sheets that have various thickness and coating mass were prepared for laser welding. The effects of parameters such as welding conditions and Al coating conditions were investigated. Al content mixed in the weld after laser welding was evaluated, and then a correlation between the mixed Al and mechanical properties was investigated. The results show that the Al-rich zones which have Fe-Al intermetallic compounds are found in the weld. The intermetallic compounds cause the decreased strength of the weld.     

镀Zn钢-6016铝合金异种金属的激光熔钎焊及数值模拟

熔钎焊是抑制或减少钢/铝异种金属激光焊接过程中FeAl脆性金属间化合物产生的有效工艺方法。采用光纤激光器,不添加任何钎料,对1.2 mm厚DC56D+ZF镀锌钢和6016铝合金平板试件进行激光搭接焊试验,利用MATLAB软件,针对焊接过程的实际情况,在一定的基本假设下建立准稳态下钢/铝异种金属激光焊接熔池形状的数学模型,基于准稳态形状控制方程数值计算获得的熔池几何形状分布,结合试验来调整焊接工艺参数,获得最佳焊接成形,利用卧式金相显微镜、扫描电镜和X射线衍射仪等手段研究焊接接头各区域的金相组织、主要元素分布与物相组成。结果表明:焊接激光束照射搭接在钢板上的铝板对接焊缝时,焊接功率和焊接速度对熔池几何形状的影响较大,随着激光功率的增大,熔深增加;而随着焊接速度的增加,熔深却变浅。当焊接功率为1 600~1 800 W、焊接速度v=30 mm/s、离焦量D=0 mm时,焊缝成形性良好,无明显裂纹、气孔等缺陷,焊接接头区域存在一个台阶状结构,在平台区域,钢/铝两钟金属存在明显的界限,界面结合依靠液态的铝在钢母材表面上的润湿、填充和铺展等作用;下凹区域,钢/铝熔合较好,Fe和Al元素的混合区宽度较大,未形成明显的FeAl脆性金属间化合物,Fe和Al的热扩散是该区域界面结合的主要原因。     

Methods for electromagnetic pressure seam welding of Al/Fe sheets

Aluminium (Al), despite its low melting point, has a high electric conductivity and thermal conductivity but poor heating efficiency, ranking as a hard-to-weld material. It is routinely necessary to weld aluminium sheets to sheets made of a dissimilar metal, such as steel sheets (Fe). In this case, it is advisable to use seam welding than spot welding in order to ensure good weld strength and joint tightness. However, seam welding of Al/Fe sheets is difficult and little reported in literature.     

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.     

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.     

Fe基手工自蔓延焊接接头的组织和性能

针对手工自蔓延焊接接头力学性能低的问题,以CuO+Al和Fe2O3+Al等高热剂反应为放热源,通过添加铁合金材料,开发了一种新型Fe基手工自蔓延焊接材料,研究其焊缝的组织形貌及性能.结果表明,实现了手工自蔓延焊接接头的熔焊连接,焊缝成形良好;熔池凝固过程中发生Cu-Fe合金的液相分离,焊缝金属呈现出富Fe相和富Cu相明显分离的宏观偏析凝固组织,富Fe相填满焊缝间隙;接头的抗拉强度达520MPa,冲击韧度32.1 J/cm2,表面硬度可达360 HB,满足金属零部件野外应急维修需要.     

Tensile resistance,microstructures of intermetallic compounds,and fracture modes of welded steel/aluminum joints produced using laser lap welding

The joining of DP780 steel to Al5052 was conducted by laser lap welding, in which the metal vapor and spatters were monitored by a high-speed camera. A universal testing machine was used to test the mechanical properties of the welded joints, and the changing law of lap tensile resistance with the laser welding parameters was analyzed. Optical microscope and scanning electron microscope were used to observe the macro-structure and micro-structure, respectively. Three different intermetallic compounds (IMCs) phases, i.e. banded Fe₂Al₅, FeAl₂ and needle-like FeAl₃ were generated at the steel/Al interface on microscopic observation. The aim of this research is to investigate the relationship among the lap tensile resistance, the welding parameters and the failure mode under different energy densities. Experimental results showed that the steel/Al joints have two different fracture modes at low heat input and high heat input. The failures happened along the heat-affected zone of the weld and along the steel/Al joint interface, respectively. And both of the two failure modes are brittle fractures. Additionally, cracks appeared at the fracture interface, and needle-like particle clusters were found in the fracture microstructure.     

LF2铝合金与Q235钢加入中间Cu层电子束焊接接头组织及形成机理

对2 mm厚的LF2铝合金和Q235钢平板试件进行了加入中间过渡层金属Cu的电子束对接焊接试验,利用光学金相、扫描电镜及能谱分析等方法研究了接头各区域的组织结构和成分分布.结果表明,接头可分为三个焊缝组织区域,其中靠近钢侧的焊缝区主要为Fe基固溶体,并含有少量金属间化合物;靠近铝侧的焊缝区为含有Fe-Al系及Al-Cu系金属间化合物的Al基固溶体;焊缝中部区为呈层带状分布的多种Fe-Al以及Al-Cu脆性金属间化合物混合区.分析认为虽然引入了铜过渡层,但在焊缝中依然有较多金属间化合物生成,特别是焊缝中部区域上,呈连续层带状分布的多种脆性金属间化合物的产生是影响接头强度的主要因素.在对接头组织结构分析的基础上,建立了描述LF2/Q235异种金属电子束对接接头形成过程的物理模型.     

Dissimilar metal joining of aluminum alloy to galvanized steel with Al-Si, Al-Cu, Al-Si-Cu and Zn-Al filler wires

Aluminum alloy sheets were lap joined to galvanized steel sheets by gas tungsten arc welding (GTAW) with Al-5% Si, Al-12% Si, Al-6% Cu, Al-10% Si-4% Cu and Zn-15% Al filler wires. Different amounts of Si, Cu and Zn were introduced into the weld through different filler wires. The effects of alloying elements on the microstructure in the weld and tensile strength of the resultant joint were investigated. It was found that the thickness of the intermetallic compound (IMC) layer decreased and the tensile strength of the joint increased with the increase of Si content in the weld. The thickness of the IMC layer could be controlled as thin as about 2 μm and the tensile strength of the dissimilar metal joint reached 136 MPa with Al-12% Si filler wire. Al-Si-Cu filler wire could result in thinner interfacial layer than Al-Cu filler wire, and fracture during tensile testing occurred in the weld for the former filler wire but through the intermetallic compound layer for the latter one. A Zn-rich phase formed in the weld made with Zn-15% Al filler wire. Moreover, the Zn-Al filler wire also generated thick interfacial layer containing a great amount of intermetallic compounds and coarse dendrites in the weld, which led to a weak joint.