铝合金多股复合焊丝脉冲mig焊接接头组织与性能分析

焊     接     学     报

TRANSACTIONS OF THE CHINA WELDING INSTITUTION

Vol.40(11):061 − 067November     2019

铝合金多股复合焊丝脉冲MIG焊接接头

组织与性能分析

董晓晶，    李    桓，    杨立军，    梁    裕

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(1. 天津大学 天津市现代连接技术重点实验室，天津　300072；2. 江苏联捷焊业科技有限公司，江阴　214400)摘    要： 选用铝合金多股复合焊丝对5A06板材进行脉冲MIG对接焊接，并与传统单丝TIG焊接接头的组织与性能进行对比. 结果表明，采用铝合金多股复合焊丝脉冲MIG焊时，焊接接头的抗拉强度最大可达340 MPa(为母材强度的86.7%). MIG焊接接头性能与TIG焊相比差异较小，但MIG焊可以提高焊接效率约4倍. 焊接接头热影响区的软化主要受较高的热输入导致的晶粒尺寸增加、再结晶比例较大以及析出相的粗化和减少影响，而采用铝合金多股复合焊丝脉冲MIG焊能够降低焊接过程的热输入，细化晶粒，减弱MIG焊接接头中Mg元素的烧损和析出物的减少，达到控制焊接接头软化的目的.

关键词： 铝合金多股复合焊丝；脉冲MIG；焊接接头软化；析出相

中图分类号：TG 444+.2           文献标识码：A           doi：10.12073/j.hjxb.20194002

0    序　　言

铝合金因其质量轻、比强度高、耐腐蚀性和焊接性良好等特点被广泛应用于汽车、航空航天和船舶工业等领域

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连接的目标，新型多股复合焊丝的概念被提出.高顶等人

[6]

率先在国内申请多股复合焊丝专利，

[7]

阐述了复合焊丝熔深、熔宽较大，熔敷效率高，适用于全方位连续焊接技术的特点. Fang等人分析了七股复合焊丝电磁压力、电阻热和旋转电弧对埋弧堆焊工艺和微观性能的影响，与传统单丝焊进行对比后发现使用多股复合焊丝可使稀释率下降33%，熔覆率提高40%，并且由于电弧的旋转效应，熔池的冷却速度提高，晶粒得到细化. 目前，多股复合焊丝主要应用于厚钢板焊接，但在铝合金领域的研究及应用尚未有报道.

文中选用铝合金多股复合焊丝，结合脉冲MIG焊接优势，对5A06铝合金板材的脉冲MIG平板对接焊接接头的力学性能进行研究. 同时，与传统单丝脉冲TIG对接焊的接头性能进行对比，分析焊接接头的组织和力学性能差异及影响因素，并对铝合金新型多股复合焊丝的实用性做出讨论.

. 如何高效、优质地进行铝

合金材料的焊接，受到国内外学者的广泛关注.目前，大多数研究着眼于脉冲类型、频率对焊接接头成形的影响以及热输入和焊丝选择对接头性能的分析. Amir等人

[3]

研究了脉冲参数对铝合

金接头强度的影响，并对热影响区软化现象进行优化. 研究发现较高的脉冲频率会增加熔池的振荡效果，使枝晶断裂、细化，从而提高接头强度、降低热影响区的软化；金礼等人

[4]

研究了在双脉

冲MIG对接焊条件下，焊接热输入对6061铝合金焊接接头性能的影响，结果表明热输入降低时，焊接接头易出现气孔和未熔合等缺陷；热输入增加，则会导致热影响区变宽，熔合区晶粒变大. 陆江旭

[5]

研究了不同焊丝对5A06铝合金

TIG焊接性能的影响，认为采用低热输入、焊丝中Mg元素含量在5.5%（质量分数）并适当添加V元素的方式可细化晶粒，获得性能良好的焊接接头. 在上述研究基础上，为实现高效优质

收稿日期：2019 − 04 − 13

基金项目：国家自然科学基金资助项目(51675375)

1    试验方法

文中5A06铝合金母材和所用焊丝成分如表1所示，母材的力学性能如表2所示，焊接试验参数如表3所示. 母材选用尺寸为300 mm × 150 mm ×

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焊    接    学    报

表 1 母材及焊丝的主要化学成分(质量分数，%)

Table 1 Main chemical compositions of base metal and filler material

第 40 卷

材料5A065356

Si≤ 0.40.21

Fe≤ 0.40.36

Cu≤ 0.10.06

Mn0.5 ~ 0.80.092

Mg5.8 ~ 6.805.12

Ti0.02 ~ 0.10.083

Al余量余量

表 2 5A06母材力学性能

Table 2 Mechanical properties of 5A06 aluminum alloy

表 3 焊接试验参数

Table 3 Welding technology parameters

序号1号

送丝速度平均电流平均电压焊接速度热输入

−1−1−1

I/AU/Vv/(mm·min)vs/(m·min)Q/(kJ·cm)225225224(打底)3号

200(盖面)

191999

300350160150

7.17.11.31.8

11.409.779.909.60

抗拉强度Rm/MPa

379

屈服强度ReL/MPa

254

断后伸长率A(%)

20.0

6 mm的平板，加工60°的V形坡口(单边30°)，钝边尺寸为2 mm，对接无间隙焊接. 脉冲MIG焊所用焊丝为江苏联捷公司生产的铝合金3股复合焊丝ER5356，如图1所示. 焊丝直径为ϕ1.6 mm，焊接接头试样标号为1号，2号. 由于TIG焊中焊接接头性能一般优于MIG焊接，文中采用TIG焊接方法作为对比，以研究多股复合焊丝MIG焊接接头性能与最优焊接接头力学性能之间的差异及产

2号

生原因. TIG焊使用直径为ϕ1.6 mm的普通ER5356焊丝，进行打底和盖面，标号为3号，其中打底采用脉冲焊. 上述两种焊接过程中所用保护气体纯度均为99.999%的氩气，保护气流量为20 L/min.

AΦ1.6A 

图 1 三股复合焊丝示意图

Fig. 1 Structure schematic of multi-composite welding wires

A-A 截面焊接接头性能测试依据GB/T2651—2008《焊接接头拉伸试验方法》，进行室温拉伸试验，拉伸速率为3 mm/min. 同时,以焊缝中心为起始点垂直于焊缝方向进行显微维氏硬度测试，取点间隔为0.5 mm，加载力1 N，负载持续时间为10 s.

细小，存在回复再结晶.

EBSD晶粒尺寸统计分析结果如表4所示. 对于焊缝区域，晶粒平均尺寸由大到小依次为1号，2号，3号. 2号，3号的平均晶粒尺寸相近，但晶粒尺寸的均匀性存在较大差异，其中3号最均匀，2号次之. 晶粒尺寸的差异主要是由焊接过程中热输入与冷却速度共同控制的，热输入越低，冷却速度越快，则过冷度越高，晶粒成核越容易，晶粒长大受到抑制. 结合表3中热输入数据可知，焊缝区1号晶粒尺寸最大，最不均匀，2号和3号晶粒尺寸接近，但是2号最小晶粒尺寸在3组中最小. 在热输入相差不多的情况下，2号应用多股复合焊丝存在多丝

2    试验结果与分析

2.1 焊接接头晶粒形貌分析

对3种焊接接头的晶粒形貌进行EBSD检测，如图2所示. 焊缝、熔合区均以等轴晶为主，热影响区(HAZ)晶粒失去沿轧制方向生长的方向性，晶粒

第 11 期

董晓晶，等：铝合金多股复合焊丝脉冲MIG焊接接头组织与性能分析

熔合区热影响区63

焊缝100 μm(a) 1 号试样焊缝熔合区100 μm100 μm热影响区100 μm(b) 2 号试样焊缝熔合区100 μm100 μm热影响区100 μm100 μm(c) 3 号试样100 μm 

图 2 焊接接头的晶粒形貌与尺寸Fig. 2 Grain shape and size of welded joints

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电弧的旋转，电弧力对熔池产生的搅拌效果使枝晶断裂、细化，促进形核，降低了晶粒尺寸. 

88%；3号HAZ选区中最大晶粒尺寸为95.2 μm，最小约为4.1 μm，再结晶比例为81%. 在焊缝与HAZ过渡的熔合区，1号在熔合线两侧由于焊接热输入大且铝合金导热性能好，HAZ大部分晶粒发生了再结晶的粗化和长大，使得焊缝和HAZ晶粒尺寸差别较大，容易形成应力集中；2号，3号在熔合线处晶粒尺寸过渡平稳，应力集中不明显.2.2 焊接接头中析出相分布

图3是不同焊接方法下焊接接头各个区域的显微组织(SEM)及能谱分析(EDS). 母材中的析出相沿轧制方向呈现出明显的链状分布，其主要由α-Al、富Mg的Al3Mg2相和富Mn、Fe的Al6(Mn，Fe)相组成.

不同焊接工艺下，焊接接头各个区域析出相的尺寸和数量不同，如图3b所示. 1号，2号焊缝区析出相细小、分布均匀. 这是由于在焊接过程中，熔合

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表 4 焊接接头的晶粒尺寸

Table 4 Grain size of welded joints

序号1号2号3号

焊缝晶粒尺寸d1/μm最大值最小值平均值492.3200.6186.0

20.29.410.5

154.655.351.8

热影响区晶粒尺寸d2/μm最大值111.567.295.2

最小值4.95..1

平均值24.020.528.3

在HAZ区域，1号，2号，3号晶粒的平均尺寸分别为24.0，20.5，28.3 μm，其中1号HAZ选区中晶粒尺寸最大为111.5 μm，最小为4.9 μm，晶粒大小不均匀，发生再结晶的比例达到92%；2号HAZ选区中最大晶粒尺寸为67.2 μm，最小尺寸为5.6 μm，晶粒尺寸均匀性好，发生再结晶的比例为

焊    接    学    报第 40 卷

没有明显的沿轧制方向的链条状分布，分布更加分

谱图 1散；2号HAZ的热循环峰值温度低，晶粒小且均匀，析出相分布与母材接近. 由此可知，使用铝合金多股复合焊丝的焊接工艺可以有效的降低热输入，减少析出相的溶解，保留与母材相似的析出相分布形态，控制再结晶程度，减弱焊接过程对加工硬化

谱图 2MgAlMnFeCu20 μm谱图 12.5876.68.9711.40.45谱图 2--70.712.117.2--效果的不利影响.

(a) 母材 SEM 和 EDS 分析1 号焊缝1 号热影响区20 μm20 μm2 号焊缝2 号热影响区20 μm20 μm3 号焊缝3 号热影响区(上层)20 μm20 μm (b) 焊接接头的 SEM 图图 3 焊接接头的析出相

Fig. 3 Precipitated phase of welded joints

区的母材、焊丝熔化，熔池受到电弧力搅拌作用，导致析出相在非平衡凝固过程中溶解、凝结和生长，3号经历两次热循环，析出相发生部分重熔. 三种焊接工艺中HAZ析出相数量与母材相比均减少.

图4为HAZ的热循环曲线，5A06发生回复再结晶的温度范围为240 ~ 300 ℃[9]

，其中1号经历的峰值温度比2号高，在200 ~ 300 ℃的温度范围内停留的时间也更长，但冷却速度慢，故1号HAZ的晶粒发生的回复再结晶比例较大(92%)，且晶粒发生了不均匀粗化，粗化效果比2号更明显，同时，析出相数量减少，尺寸增大；3号在打底脉冲焊过程中的峰值温度较高，在回复再结晶温度范围内停留时间长，升温和冷却速度慢，这主要与焊接速度慢、能量的积累较多有关，在HAZ同样出现了晶粒的粗化，但相较于1号，晶粒大小和分布更加均匀；3号经历盖面焊接的重熔之后，HAZ热循环曲线的峰值温度明显降低，经历两次焊接后，析出相数量减少，

5001 号2 号4003 号-打底C3 号-盖面°/T300 度温20010000100200300 时间 t/s图 4 HAZ焊接热循环

Fig. 4 Welding thermal cycle of HAZ

2.3 焊接接头的力学性能

从焊接接头的显微硬度分布图5可知，3个试

样的硬度分布总体趋势大致相同，焊缝区硬度最低，随至焊缝中心距离的增加，硬度值有所增加，达到母材位置时，硬度值稳定在 HV1左右，但各个区域的大小、平均硬度值方面有明显差异. 其中1号，2号，3号在焊缝区的平均硬度值分别为80.1，81.7，85.5 HV1，分别达到母材的.2%，91.8%，96.1%.

100HAZ1 22 号3 号号)VH90( H 度硬微显80HAZ3HAZ170051015202530 距离焊缝中心的距离 d/mm图 5 焊接接头显微硬度分布

Fig. 5 Microhardness variation of welded joints

1号，2号，3号在HAZ的平均硬度值分别为83.4，.3，86.8 HV1. 其中2号在HAZ的硬度值与母材相当，1号和3号在HAZ的平均硬度分别达到母材的93.7%和97.5%. 在传统5xxx铝合金的

第 11 期董晓晶，等：铝合金多股复合焊丝脉冲MIG焊接接头组织与性能分析65

熔化焊接中，存在焊接接头焊缝区和热影响区的软化，而在文中3号的焊缝区和热影响区软化程度很小，硬度基本和母材持平；2号在焊缝区略有软化，HAZ不存在软化现象.

焊接热循环不仅可以影响接头晶粒大小、析出物尺寸和分布，还影响着HAZ宽度，MIG焊接1号的线能量高于2号，导致热输入1号大于2号；焊接过程中TIG焊能量更集中，但3号在经历两次热循环后，热量的积累与2号相差不大，从而1号HAZ宽度大于2号HAZ宽度，2号和3号HAZ宽度相当，这与焊接热循环的测试结果相吻合.

一般而言，金属材料的硬度值与其塑性变形密切相关，而多晶的塑性变形可以通过Hall–Petch公式与晶粒尺寸联系起来，即焊缝金属的显微硬度与晶粒尺寸的平方根倒数呈线性关系

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度也越低；HAZ中Mg含量高于焊缝，固溶液化效果更好，故焊接接头中HAZ硬度值高于焊缝. 

7Mg 元素含量 w (%)6543211 号2 号6.326.566.343 号6.175.395.536.56 0焊缝热影响区母材 

图 6 焊接接头中Mg元素分布

Fig. 6 Distribution of Mg element in welded joints

位错密度也是影响铝合金强度的主要因素之一，而位错主要集中于变形晶粒和亚晶界处，在再结晶晶粒内部较少

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，晶粒尺寸越

大，强化效果越弱. 结合表4与硬度分布图可知：1号焊接处晶粒平均尺寸最大，3号焊接晶粒尺寸最小，根据硬度分布图可知3号焊接处平均硬度值最大，1号焊接硬度值最小，满足Hall-Petch关系；在HAZ区域，3号晶粒平均尺寸最大，2号晶粒平均尺寸最小，但2号HAZ的平均硬度值最大，1号HAZ平均硬度值最小，与经验公式存在一定差异.由于在5A06铝合金中，Mg元素的减少会产生焊接接头软化的现象，可结合Al-Mg合金中Mg的增量强化公式(1)进行预测.

∆σssMg=HCMgα，因此再结晶比例的增大

会导致位错密度的降低，从而导致强度下降. 对于焊缝，类似于铸造态结构，不存在回复再结晶，位错密度较少，可以忽略此项因素；对于不可热处理强化的5A06铝合金来说，强化主要通过形变和固溶，因此HAZ区域中的位错密度不可忽略，统计三个试样的HAZ发生回复再结晶的比例，发现1号比例最大，2号次之，3号最小；结合析出相分布、晶粒尺寸和Mg含量等多种因素的综合作用，使得2号HAZ硬度值最大，3号次之，1号硬度值最小.

焊接接头的拉伸性能如表5所示. 1号，2号的平均抗拉强度分别为308，328 MPa，分别达到母材强度的81.3%，86.7%，二者断裂于焊趾处.这主要是由于焊趾处容易出现缺陷和应力集中，且二者在焊缝均存在软化现象，显微硬度值在该区域最低，由低强度向高强度过渡的薄弱区在受到拉伸应力作用时更容易发生断裂；而3号平均抗拉强度最高，强度可达到母材强度的93.1%断

(1)式中：CMg为Mg元素的含量；H，α为和材料有关的常数

[8,11]

.

通过对焊接接头不同区域进行能谱分析，得到如图6所示不同焊接方法下，焊接接头各个区域Mg元素含量. 由式(1)知，Mg元素含量减少，固溶强化效果也随之减弱，试样接头中Mg元素的分布趋势与硬度分布趋势相符，即在焊缝区Mg烧损严重：焊接处Mg元素含量越低，该试样焊缝处的硬

表 5 焊接接头的力学性能

Table 5 Mechanical properties of welded joints

编号1号2号3号

抗拉强度Rm/MPa①315324349

②305340356

③305322355

均值308328353

①11.4311.4514.5

断后伸长率A(%)②11.438.5820

③11.4310.2820

均值11.4310.1018.2

断裂位置

66焊    接    学    报第 40 卷

后伸长率可达母材的91%，其力学性能优于文献[5]中优化工艺和焊丝成分后的接头性能可达激光–TIG复合焊焊接接头力学性能水平

[14]

式中：G为剪切模量；B为Burgers矢量；L是析出相之间的平均距离. 在熔化焊过程中，较小析出相的溶解使得L值增大，从而强化效果减弱，产生软化，2号断口析出相密集，L值减小，强化效果提高，故2号强度比1号有所提高，但在微孔聚集断裂中，初始微孔很容易在基体界面和第二相中萌生

[15]

. 焊接接头

断裂于热影响区–母材位置，这主要是因为焊缝余高起到加强作用，而热影响区受热循环的影响，晶粒发生了回复再结晶，加工硬化效果降低，强度略有下降.

图7为焊接接头断口形貌，图中1号和2号的断口中存在较多韧窝和撕裂脊，2号断口中的韧窝比1号更明显、均匀，韧窝底部的第二相粒子较1号更多，根据式(2)

[8]

，第二相粒子的增多使得微孔更容易

形核、长大，并最终形成微裂纹，使断裂过程变得更加容易，故2号比1号有更高的强度和更低的韧性. 图7中的3号和母材表现出相同的韧性断裂特征，断口主要是由大尺寸韧窝和周围分布的大量小尺寸韧窝构成，在韧窝的底部存在大尺寸析出相.

√σpre=3GBL(2) 40 μm(1) 1 号断口(2) 2 号断口40 μm40 μm40 μm(4) 母材断口 

(3) 3 号断口图 7 焊接接头的断口形貌

Fig. 7 Fracture microstructure of welded joints

3    结　　论

(1)通过对焊接接头的显微组织分析发现，对于焊缝，晶粒粗化、Mg元素烧损是硬度降低的主要因素；对于HAZ，热输入大导致晶粒发生的回复再结晶、晶粒粗化、Mg含量及析出相的减少是其硬度主要影响因素.

(2)使用新型多股复合焊丝能够细化晶粒，使焊缝至熔合区的晶粒尺寸变化趋缓，有利于减小应

力集中.

(3)多股复合焊丝能够显著减小传统熔焊方法对热影响区的软化，其接头的力学性能可达母材的.7%，热影响区平均硬度约为.3 HV1.

(4)文中脉冲MIG焊接接头性能表现良好，优于大多数5系铝合金的熔焊接头性能，力学性能可达激光-TIG复合焊焊接接头的水平. 脉冲MIG一次焊接成形，其效率比TIG焊提高约4倍，在满足强度要求时，铝合金多股复合焊丝的脉冲MIG焊

第 11 期董晓晶，等：铝合金多股复合焊丝脉冲MIG焊接接头组织与性能分析

67

具备更高的经济效益.参考文献：

[1]Hadadzadeh A, Ghaznavi M M, Kokabi A H. HAZ softening be-havior of strain-hardened Al-6.7 Mg alloy welded by GMAW andpulsed GMAW processes[J]. The International Journal of Ad-vanced Manufacturing Technology, 2017, 92(5–8): 2255 − 2265.[2]Wang Y, Wei B, Guo Y, et al. Microstructure and mechanical

properties of the joint of 6061 aluminum alloy by plasma-MIGhybrid welding[J]. China Welding, 2017, 26(2): 58 − .[3]Hadadzadeh A, Ghaznavi M M, Kokabi A H. The effect of gas

tungsten arc welding and pulsed-gas tungsten arc welding pro-cesses parameters on the heat affected zone-softening behavior ofstrain-hardened Al-6.7 Mg alloy[J]. Materials & Design, 2014,55(3): 335 − 342.

[4]金　礼, 徐　敏, 薛家祥, 等. 热输入对铝合金双脉冲MIG焊接

头性能的影响[J]. 焊接学报, 2018, 39(1):  − 92.

Jin Li, Xu Min, Xue Jiaxiang, et al. Effect of line energy on prop-erties of aluminum alloy joints in double pulsed MIG welding[J].Transactions of the China Welding Institution, 2018, 39(1):  −92.

[5]陆江旭. 5A06铝合金TIG焊焊接接头性能研究与高韧性高强

度铝合金焊丝研制[D]. 杭州: 浙江大学, 2016.

[6]高　顶, 阿兰•托马斯•麦尔, 郝　锋. 中国矿业大学. 一种多股

绞合焊丝: 中国, 201455562U[P]. 2010–05–12.

[7]Fang C, Chen Y, Yang Z, et al. Cable-type welding wire sub-merged arc surfacing[J]. Journal of Materials Processing Techno-logy, 2017, 249(11): 25 − 31.

[8]Yan S, Nie Y, Zhu Z, et al. Characteristics of microstructure and

fatigue resistance of hybrid fiber laser-MIG welded Al-Mg alloy

joints[J]. Applied Surface Science, 2014, 298(11): 12 − 18.

[9]李念奎, 凌　昊, 聂　波, 等. 铝合金材料及其热处理技术[M].

北京: 冶金工业出版社, 2012.

[10]Dongxia Y, Xiaoyan L, Dingyong H, et al. Effect of minor Er and

Zr on microstructure and mechanical properties of Al-Mg-Mn al-loy (5083) welded joints[J]. Materials Science and Engineering A,2013, 561(3): 226 − 231.

[11]Kim Dongyoon, Kim Dongcheol, Kang Munjin, et al. Effect of

aluminum welding wire Mg content on the mechanical propertiesof Al 5083 alloy weld metal[J]. Journal of Korean Institute ofMetal and Materials, 2017, 55(10): 716 − 723.

[12]Howeyze M, Arabi H, Eivani A R, et al. Strengthening of

AA5052 aluminum alloy by equal channel angular pressing fol-lowed by softening at room temperature[J]. Materials Science andEngineering A, 2018, 720(12): 160 − 168.

[13]Lu J, Wu X, Liu Z, et al. Microstructure and mechanical proper-ties of ultrafine-grained copper produced using intermittent ultra-sonic-assisted equal-channel angular pressing[J]. Metallurgicaland Materials Transactions A, 2016, 47(9): 48 − 4658.[14]Chen Y, Miao Y, Li L, et al. Joint performance of laser-TIG

double-side welded 5A06 aluminum alloy[J]. Transactions ofNonferrous Metals Society of China, 2009, 19(1): 26 − 31.[15]Zhang L, Li X, Nie Z, et al. Comparison of microstructure and

mechanical properties of TIG and laser welding joints of a newAl-Zn-Mg-Cu alloy[J]. Materials & Design, 2016, 92(4): 880 −887.

第一作者简介：董晓晶，女，1993年出生，硕士研究生. 主要研究方向为铝合金焊接冶金及焊接工艺. Email：4613984@qq.com

通信作者简介：杨立军，男，博士，教授. Email：yljabc@tju.edu.cn

2019, Vol. 40, No. 11TRANSACTIONS OF THE CHINA WELDING INSTITUTION

III

Key words: high-speed welding；tandem TIG weld-ing；arc power matching；microstructures and properties ofweld

；austenite stainless steel

X-ray based defect testing method for a lap joint withunequal thickness steel plates CHI Dazhao1

， MA Ziqi2

，CHENG Yi2

， WANG Ziming1

(1. State Key Laboratory ofAdvanced Welding and Joining，Harbin Institute ofTechnology, Habin 150001, China；2. Shanghai AerospaceEquipments Manufacturer Co., Ltd., Shanghai 200245,China). pp 45-48

Abstract: It is difficult to automatically recognizedefects using digital image processing method in X-ray imagethat tested from lap joint with unequal thickness plates. Thisattributes to the very different gray levels in background imagecaused by the unequal thickness of the workpiece, and thecontinuous change gray levels caused by lap joint. Besides, theposition of the lap joint is uncertain placed before tested, i.e.there is always an angel between the directions of lap joint andgravity. And this makes it difficult for defect detection andlocalization. In this paper, a method of X-ray image correctionbased on invariant moments is presented to solve the problemof image skew. In addition, a defect detection methodcombined of image noise suppression, background removal,image segmentation and mathematical morphology ispresented. The results show that the proposed method caneffectively recognize the gas pores in lap joint with unequalthickness, and it is suitable for automatic detection.

Key words: lap joint；X-ray；digital image processing；defect detection

Effective three-dimensional deviation extraction of thewelding torch for robotic arc welding with steel sheets YU Zhuohua1

， HU Yanmei1

， HE Yinshui2

(1. East ChinaJiao Tong University, Nanchang 330100, China；2. NanchangUniversity, Nanchang 330031, China). pp 49-53

Abstract: Three-dimensional (3D) deviation extractionof the welding torch for the automated welding process is aprerequisite in robotic intelligentized arc welding. In thispaper, with the welding robot meal active gas (MAG) arcwelding method was used to join steel sheets with microgrooves. Passive vision sensors with the appropriatecombination of the filter and dimmer glass were used to captureimages which contained complete arc regions, edge lines of theseam, and joint lines. An effective algorithm was thenproposed to directly extract the seam line of the butt joint. Todetermine the tracking point at each sampling time the real-time position of the welding torch was first signed with the

geometric center of the arc region. Then, another algorithmwas suggested to determine the tracking point that lies in theextracted seam line. It was transformed into the worldcoordinate using existing vision calibrated techniques, and the3D deviation was yielded when the exact position of thewelding torch in the world coordinate system had beenrecorded from the control system of the welding robot.Experimental results show that the proposed method in thispaper can effectively acquire the 3D deviation of the weldingtorch in real time.

Key words: deviation extraction；three-dimensionaldeviation

；steel sheets；robotic welding；vision sensing

Effect of undercut defect on deformation behavior TC4titanium alloy laser welded butt joint under static tensileloading DUAN Aiqin， WANG Zhensu， PENG Huan，MA Xuyi (Science and Technology on Power Beam ProcessLaboratory, Beijing Aeronautical Manufacturing TechnelogyResearch Institute, Beijing 100024, China). pp 54-60

Abstract: By measuring and analyzing infraredthermal image of the specimen in static load tensile testprocess, it was studied that the influence of the undercutdefects and double-sided dressing method on the deformationbehavior of the laser welded joint specimens of TC4 titaniumalloy. The results showed that for the unmodified specimens,the yield phenomenon occurs first in the region of the joint, butthe undercut value has an effect on the stress and strain ofstarting to yield phenomenon, and a great effect on the plasticdeformation behavior. When the undercut is less than a certainvalue, the large plastic deformation occurs in the base metalregion and the plasticity of the specimen is comparable to thatof the base metal, but the larger undercut defect results in aconcentrated plastic deformation in the joint region and rapidlyfailed in this region. But the double-sided dressing specimen issignificantly different. The physical yield is no longerconcentrated in the joint region, but at the same time occurs inthe several regions including joint and the base metal. And theplastic deformation mainly occurs in the base material area,similar to that of the base material.

Key words: TC4 titanium alloy；laser welding；under-cut defect

；static tensile loading；infrared thermograph method

Microstructure and mechanical properties of pulse MIGaluminum alloy welded joints by means of a novel multi-strands composite welding wire DONG Xiaojing1

， LIHuan1

， YANG Lijun1

， LIANG Yu2

(1. Tianjin KeyLaboratory of Advanced Joining Technology, TianjinUniversity, Tianjin 300072, China；2. Jiangsu Lianjie Welding

IVTRANSACTIONS OF THE CHINA WELDING INSTITUTION2019, Vol. 40, No. 11

Technology Co.,Ltd., Jiangyin 214400, China). pp 61-67

Abstract: In this study, a novel multi-strand compositewelding wire was adopted in 5A06 aluminum pulse MIGwelding method, and the microstructures and properties ofaluminum alloy multi-strand composite wire welded jointswere compared with those of traditional TIG welded joint. Theresults show that the welded joint used by this novel wire has abetter tensile strength, which reaches up to 340 MPa (86.7% ofthe base metal). The performance of MIG welded joint issimilar to that of TIG welded joint, and it can improve weldingefficiency by about 4 times. It is also found that the softeningof the heat affected zone of the welded joint is mainly affectedby the larger grain size and the higher recrystallization ratio,the lower Mg content as well as the coarsening and reductionof the precipitated phase caused by higher heat input. Inaddition, the pulse MIG welding method with this novel wirecan reduce the heat input in welding process, refine grains, andcan significantly weaken the loss of Mg element andprecipitation. Based on these advantages, the softening of thepulse MIG welded joint decreases and the excellent propertiesof welded joint can be obtained.

Key words: multi-strands composite welding wire；pulsed MIG weld；softening behavior of welded joint；precipit-ated phase

Mechanism analysis of interaction between laser andparticles in laser additive manufacturing YANGYicheng1,2

， HUANG Ruisheng1

， SUN Qian1

， JIANG Bao1

，WANG Ziran1

(1. Harbin Welding Institute LimitedCompany, Harbin 150028, China；2. China Academy ofMachinery Science and Technology Group Co., Ltd., Beijing100044, China). pp 68-74

Abstract: The degree of interaction between laserbeam and powder particles decided the statue of the particlesbefore entered the molten pool. In this paper, both the transientstate image captured by shadowgraphy enhancement and imageinformation processing were used to analysis the changecharacteristics of the whole powder stream and single particlesafter irradiated by laser from macro and micro perspectives.Characteristic parameters, including amount of high lightparticles, total area of high brightness area, the intensity of asingle particles irradiated by laser were extracted to analysisthe influence of the different parameters on the interactionbetween laser and powder particles. The results show thatbetter regulation of the interaction between laser and particlescan be achieved based on the reasonable match of mainparameters. By increasing the laser energy density and theinteraction time of laser and powder particles, the intensity of

particles irradiated by laser is increased and the particles aremore likely to enter the molten pool in liquid state.

Key words: additive manufacturing；interaction oflaser and powder particles

；image processing

Experimental and simulation study on multiple cracks ofweld toe WEI Guoqian1,2

， CHEN Siwen1

， YU Xi1

，CHENG Lifu1

(1. Key Laboratory of Metallurgical Equipmentand Control Technology, Ministry of Education, WuhanUniversity of Science and Technology, Wuhan 430081, China；2. Hubei Key Laboratory of Mechanical Transmission andManufacturing Engineering, Wuhan University of Science andTechnology, Wuhan 430081, China). pp 75-81

Abstract: The fatigue cracks at weld toes of weldedjoints mostly take the form of multiple cracks.Carrying out thetensile fatigue tests based on spectrum with variable amplitudeloading of cruciform joints. The evolution process of beachmarks characterizing the instantaneous front track of cracks isobtained, the existence of multiple cracks is verified. It wasfound that the multiple cracks at weld toes of welded joints hadobvious asynchronous characteristics. By means of finiteelement simulation technology, several semi-elliptical initialcracks were inserted into the weld toe step by step, and theevolution process of multiple cracks was simulated. Thesimulation results were consistent with the experimentalfracture. The results show that the shape of crack front changescontinuously due to crack fusion, but eventually it tends toevolve towards semi-elliptical shape;The life of crack initiationand small crack propagation in welded structures accounts for alarge proportion in the whole fatigue process and has animportant influence.

Key words: weld toe；multiple cracks；beach marks；crack fusion

；crack evolution

Surface stress correction of the thick welded platemeasured by contour method using eigenstrain method YAN Yi， LIU Chuan， WANG Chunjing， SHEN Jiabing (Jiangsu University of Science and Technology, Zhenjiang212003, China). pp 82-86

Abstract: The longitudinal stress distribution on thecut plane is constructed by the eigenstrain method based onpart of the internal stress data measured by contour method,and the surface stress error is corrected by the eigenstrainmethod; the effect of the order of basis function forconstructing eigenstrain distribution on the constructed stress isalso investigated. Results show that longitudinal stressdistribution trend on the cut plane constructed by eigenstrainmethod agrees well with that by the contour method, thesurface stress is increased by about 27% as compared with the