镀锌层对铝_镀锌钢板CMT熔_钎焊电弧加热行为的影响

收稿日期:2009-02-16

基金项目:哈尔滨工业大学(威海)校研究基金资助项目(HIT (WH )

X B200814)

镀锌层对铝/镀锌钢板CMT 熔-钎焊电弧

加热行为的影响

张洪涛1,　冯吉才2,　何　鹏2,　赵洪运1

(1.哈尔滨工业大学(威海)材料科学与工程学院,山东威海　264209

;

2.哈尔滨工业大学材料科学与工程学院,哈尔滨　150001)

摘　要:通过建立的电弧形态视觉传感系统以及电流电压波形采集系统研究了镀锌层对铝/镀锌钢板C MT 熔-钎焊电弧加热行为的影响.结果表明,小电流焊接时,镀锌层可以作为等离子体阴极,起到稳定电弧的作用,而在无镀锌层条件下,电弧的阴极斑点不停地跳跃,电弧极其不稳;随着焊接电流的增大,在镀锌钢板上焊接时,由于镀锌层的蒸发变得十分剧烈,这种蒸发行为也使得在镀锌钢板上焊接时的电弧的边缘上翘,减小了电弧与工件的接触面积,进而降低了焊接热输入,减小了界面脆性化合物层的厚度.关键词:铝;镀锌钢板;熔-钎焊;电弧形态;焊接热输入

中图分类号:TG 115.28　文献标识码:A 文章编号:0253-360X (2009)08-0037-04

张洪涛

0　序 言

近年来,能源危机与环境问题越来越严重,这些

压力也直接影响到汽车制造业中.汽车制造业中为了节约燃料,保护环境,汽车轻量化便成为一个重要的发展方向,增加铝材的使用数量是汽车轻量化的重要措施之一,所以在汽车工业生产中,“铝+钢”双金属焊接结构的应用越来越广泛,这也必然涉及到铝和钢两种材料之间的连接[1,2].

由于铝和钢的熔点以及热物理性能相差很远,同时铝铁之间也极易反应生成脆性的金属间化合物,以上这些因素给两者之间的熔焊连接造成了困难.若采用其他焊接方法,比如压力焊接和钎焊,接头的形状不但受到限制,而且生产效率也大大降低.近年来,国内外许多学者对铝和钢的熔-钎焊进行了探索性的研究,这种方法是通过熔化低熔点的铝板,同时保持钢板为固态,借助熔融铝的润湿铺展从而形成搭接接头实现两者之间的连接.同时发现接头界面脆性化合物层的厚度对接头的力学性能有重要的影响,而决定接头界面脆性化合物层厚度的关键因素则是焊接热输入[3,4].

在铝板和镀锌钢板的C MT (cold metal trans fer )熔

-钎焊中,由于镀锌层的沸点较低(906℃

),因此镀锌层在焊接时会被蒸发,这种蒸发也必然影响焊接时的电弧加热行为,从而改变焊接热输入[5],而关于镀锌层对焊接电弧以及焊接热输入的影响国内外鲜有报道.为了研究镀锌层对焊接加热行为的影响,采用高速摄像技术建立了电弧形态视觉传感系统,分别采集在镀锌钢板和非镀锌钢板上堆焊时的电弧形态,并对其特征差异进行分析,结合界面组织特点,阐明了镀锌层对电弧加热行为的影响机制.

1　试验方法

试验材料主要为镀锌钢板和非镀锌的Q235钢板(200mm ×50mm ×0.6mm ),纯氩,焊接过程中氩气流量为10L/min ;建立的电弧形态视觉传感系统与电流电压波形采集系统如图1所示.分别在Q235钢板和镀锌钢板上堆焊,采集焊接时的电弧形态特征,对比分析镀锌层对电弧形态特征的影响,同时对焊接时的电信号进行数据采集.焊接系统主要由C MT 焊机、M otoman 机器人组成.焊接方式为平板堆焊,填充材料为AlSi5合金,导电嘴距离钢板表面的距离为10mm ,通过更换Q235钢板和镀锌钢板,并调节焊接电流,从电弧正面拍摄其动态形状以进行对比.

2　试验结果与分析

2.1　镀锌层对电弧形态特征的影响

试验中发现,镀锌层的存在对焊接电弧的形态

第30卷第8期2009年8月

焊　接　学　报

TRANS ACTI ONS OF THE CHI NA WE LDI NG I NSTIT UTI ON

V ol.30　N o.8August 2009

图1　电弧形态视觉传感与电流电压波形同步采集系统示

意图

Fig 11　Diagram of arc shape and waveform synchronizing

collectting system

特征有很大的影响,这种影响与焊接工艺参数有关.当焊接电流较小时,镀锌层的主要作用是稳定焊接电弧;而焊接电流较大时,镀锌层对焊接电弧的影响主要集中在形态改变上.

当焊接电流较小时,位于镀锌钢板上方的电弧非常稳定地在焊丝的正下方燃烧,如图2所示,电弧形态呈现柱状特征.在整个周期内,电弧的位置始终位于焊丝的正下方

.

图2　电流20A 镀锌钢板表面的电弧形态变化(幅/4ms )

Fig 12　Arc shape on zinc 2coated steel sur face with welding

current 20A (frame/4ms )

而相同焊接工艺参数下,Q235钢板上燃烧的电弧无论是在形态上,还是稳定性上都与镀锌钢板上燃烧的电弧有较大的差异.电弧阴极斑点不停地发生跳跃,电弧燃烧过程极其不稳,如图3所示.同时由于没有镀锌层的存在,短路过渡时的表面张力比较小,因此熔滴过渡变得困难,往往呈大滴状粘在焊丝的端部,焊丝端部形状的改变也使得电弧的形态呈现球状特征.

对上面两种钢板表面堆焊时的电流电压信号进行数据采集,如图4所示.结果发现,

镀锌钢板表面

图3　电流20A 时Q235钢板表面的电弧形态变化(幅/4ms )

Fig 13　Arc shape on Q235steel sur face with welding current

20A (frame/4ms

)

　图4　电流20A 时在不同钢板上堆焊时的电流电压波形

对比

Fig 14　Comparison of voltage and current waveforms welding

on different steels with current 20A

堆焊时的电流电压信号上下波动较小,在每个特定的区间基本稳定保持为直线,直流脉冲特征明显;而Q235钢板堆焊时电压数值明显增加,呈上下起伏的

波浪线,电流数值上下波动也非常剧烈.电流电压参数的变化对电弧的形态有一定的影响,这种形态变化主要由于熔滴过渡的不稳定性决定的,但两者最明显的差别还在于电弧的稳定性方面.当有镀锌

38　焊　接　学　报第30卷

层存在的时候,由于锌的电子逸出功较小,因此镀锌

层可以作为等离子体阴极,这样便去除了斑点的选择性形成的问题,提高了焊接电弧的稳定性.

当焊接电流大于20A 后,镀锌层的蒸发变得剧烈,电弧在弧柱区有明显的膨胀现象,电弧边缘上翘.这主要是由于在焊接过程中,镀锌层的蒸发所造成的,在电弧的边缘部位,电弧压力较小,因此锌蒸气往往通过电弧的边缘蒸发,从而影响到电弧形态.锌蒸气可以形成等离子阴极,这使得电弧能够在焊丝和电弧边缘的锌蒸气之间继续燃烧,从而使电弧边缘上翘,改变了电弧的形态,如图5所示

.

　图5　电流62A 镀锌钢板表面的电弧形态变化(幅/4ms )

Fig 15　Arc shape on zinc 2coated steel sur face with welding

current 62A (frame/4ms )

当采用同样的焊接电流在Q235钢板表面进行堆焊时,在一个周期内的电弧形态变化如图6所示.由于电流的增大,熔滴过渡促进力增加,因此,没有出现熔滴粘在焊丝上的现象,这也使得电弧的周期性变化特征稳定.与相同参数下的镀锌钢板上的电弧形态相比,Q235钢板上的电弧形态呈钟罩形,其

电弧铺展面积明显大于同种参数下在镀锌钢板上的

图6　电流62A 时Q235钢板表面的电弧形态变化(幅/4ms )Fig 16　Arc shape on Q235steel sur face with welding current

62A (frame/4ms )

电弧铺展面积.并且随着焊接电流的增加,在镀锌钢板和Q235钢板上堆焊时的电信号波形特征趋于一致,如图7所示

.

　图7　电流62A 时在不同钢板上堆焊时的电流电压波形

对比

Fig 17　Comparison of voltage and current waveforms on dif 2

ferent steels with welding current 62A

2.2　电弧加热直径的变化

从上面的分析可以看出,在镀锌钢板上进行堆焊,当焊接电流大于20A 时,电弧形态由于镀锌层的蒸发而发生明显改变.为了定量地研究镀锌层对电弧加热行为的影响,因此定义电弧与工件表面接触区域的直径为电弧加热直径,用符号D 表示,通过已知的焊丝直径(1.2mm ),可以根据比率计算出电弧加热直径的大小.图8为电弧加热直径随焊接电流的变化关系图,从图中可以看到,镀锌层的蒸发可以明显地减小电弧加热直径.2.3　镀锌层对界面脆性化合物层厚度的影响镀锌层通过蒸发改变了电弧的加热行为,从而对焊接的温度场产生了直接的影响,焊接温度场又决定了铝/钢界面脆性化合物层的厚度.图9是焊接电流62A 时分别在镀锌钢板和Q235钢板上堆焊时的界面组织形貌.可以发现镀锌钢板表面堆焊时

第8期张洪涛,等:镀锌层对铝/镀锌钢板C MT 熔-钎焊电弧加热行为的影响39

　

图8　电弧加热直径随电流的变化关系图

Fig 18　Relationship between arc heating diameter and weld 2

ing

current

图9　相同焊接参数下Q235和镀锌钢板堆焊试样界面组织

Fig 19　Inter facial micro structure s of different steels

界面脆性化合物层的厚度明显小于Q235钢板上堆焊时界面化合物层的厚度;同时Q235钢板上堆焊时

的针状化合物也明显地比相应的镀锌钢板堆焊时的针状化合物更为粗大.正因为在Q235钢板上堆焊

接头的化合物层的厚度,特别是靠近钢侧的化合物

层的厚度显著增加,在进行线切割时,接头从界面处开裂,造成钢板与熔化金属的脱离.

3　结 论

(1)在小电流焊接时,镀锌层的存在主要起稳

定电弧的作用.Q235钢板表面燃烧的电弧阴极斑点发生无规律的跳动,电弧稳定性降低,而在镀锌钢板表面燃烧的电弧则非常稳定地处于焊丝正下方.

(2)当焊接电流大于20A 以后,镀锌层的蒸发使得电弧边缘上翘,改变了焊接电弧形态,减小了电弧加热直径,进而降低了电弧对钢板的热输入.

(3)焊接热输入的降低也使得堆焊接头界面脆性化合物的生成数量减少,有利于提高接头的力学性能.参考文献:

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[3]　张洪涛,何　鹏,冯吉才,等.铝钢异种材料焊接研究现状与

发展[J ].焊接,2006(12):7-12.

Zhang H ongtao ,He Peng ,Feng Jicai ,et al .Research status and de 2velopment of welding for dissim ilar materials alum inium and steel.W elding &Joining ,2006(12):7-12.

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[5]　李瑞峰,于治水,施一丰,等.Q235和镀锌钢板氩弧钎焊电弧形

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作者简介:

张洪涛,男,1980年出生,博士,讲师.主要从事异种

材料熔-钎焊以及特种焊接方面的研究.已发表论文10余篇.

Email :hitzht @https://www.360docs.net/doc/cb12121270.html,

40　焊　接　学　报第30卷

na,T aiyuan030051,China).p17-20

Abstract:　The metal trans fer behavior of mes o2spray trans fer is studied under self2adapting control of mes o2spray in pulse MIG welding of aluminum.The main acting forces against a droplet and the im portant role of sur face tension are analyzed by the waves testing and high speed camera of short circuit,mes o2spray and spray from different parameters in pulse MIGwelding.The results of experiment dem onstrate that a self2adapting process should be accurately con2 trolled for the narrow w orking range of mes o2spray trans fer in pulse MIG welding of aluminum,and the proposed control parameters can make the arc running within the narrow range and the special droplet trans fer process stable.

K ey w ords:　aluminum;pulse MIG welding;self2adapting control;droplet trans fer;high speed camera

Pre2processing softw are for three2dimensional simulation and prediction of w eld solidification cracks DONG Zhibo1,ZH AN X iaohong2,WEI Y anhong1,2,LU Y afeng3,G UO Ping3,Y ANG Y ong fu3(1.S tate K ey Laboratory of Advanced Welding T echnology Production,Harbin Institute of T echnology,Harbin150001,China;

2.Department of Material Science and T echnology,Nanjing Univer2 sity of Aeronautics and Astronautics,Nanjing210016,China;

3. T itanium Alloy Institute,N orthwest Institute F or N on2ferrous Metal Research,X i’an710016,China).p21-24

Abstract:　A s oftware consisted of pre2processing,post2pro2 cessing and s olidification cracks predicting subsystems is developed, which can simulate and predict the weld s olidification cracks with three dimensional FE M.The pre2processing helps users to choose the w orkpiece,to input the thermal2mechanical properties of materi2 als and welding parameters,to set boundary conditions,and to auto2 matically generate command streams of MSC.Marc to create process files for final FE M calculation.Furtherm ore,system can trans fer the process files to s oftware package of MSC.Marc to com plete the cal2 culation of thermal,strain and stress distributions in background. Therefore,the simulated results are prepared for the post2processing.

K ey w ords:　s olidification cracking;pre2processing;simula2 tion and prediction

Full digitalized w elding pow er platform with multi2function pur2 poses SH A Deshang1,LI AO X iaozhong1,SH AN Lijun2,BAO Y unjie2(1.School of Automation,Beijing Institute of T echnology, Beijing100081,China;2.Beijing T ime T echnology C om pany Ltd, Beijing100085,China).p25-28

Abstract:　A welding platform used in shielded metal arc welding,TIG,C O2short2circuit G M AW,single pulsed MIG/M AG and double pulsed MIG/M AGwelding is established.The platform is com posed of welding power,wire feeder and water cooler,which op2 eration principles and main function are analyzed.The full digital control theories of short circuiting trans fer,single pulsed and double pulsed MIG/M AG are explained in detail.Experimental results of a 400A prototype show that it is feasible to apply different welding methods only by changing s oftware and without changing any hard2 ware,and the welding per formance is als o per fect.

K ey w ords:　welding power;full digital control;gas metal arc welding

I nfluence of nano2Al2O3suspension concentration on forming of plasm a spraying coating FAN X iang fang,QI U Changjun, CHE N Y ong(C ollege of Mechanical Engineering,Nanhua Universi2 ty,Hengyang421001,China).p29-32

Abstract:　The nano2alumina coating was prepared by sus2 pension plasma spraying under atm ospheric conditions,and the effect of nano2Al2O3suspension concentration on forming of plasma spray2 ing coating was studied by scanning electron microscopy and theory analyses.The results show that the concentration of nano2Al2O3sus2 pension has a significant in fluence on the size of droplet,the en2 thalpy needed for spraying suspension,the roughness of coatings sur2 face and the microstructure of coatings.Low concentration of the suspension is beneficial for fine nanostructures coatings,which means low spraying efficiency.The optimized concentration of nano2 alumina suspension is between5%(wt)and10%(wt).

K ey w ords:　nano2alumina;suspension concentration;plas2 ma spraying;coating forming

E ffect of alloying elements on intermediate temperature filler metal in stepped w elding of6063aluminum alloy ZH U hong1,2,X UE S ongbai1,SHE NG Zhong1(1.C ollege of Materials Science and T echnology,Nanjing University of Aeronautics and As2 tronautics,Nanjing210016,China;2.The14th Research Institute, China E lectronic T echnology G roup C orporation,Nanjing210013, China).p33-36

Abstract:　The contents of S i,Cu,Ni and RE are changed by using orthog onal test in order to study the effect of the content changes on the melting points,spreading property and shear strength of Al2S i2Cu2Ni2RE,and the microstructure of filler metal is analyzed by SE M and E DS.I t is indicated that the spreading area is mainly affected by the com position of filler metal and tem perature;the DSC results show that Cu has the m ost im portant in fluence on the melting points filler metal,which decreases sharply with the Cu content in2 creasing,and then Ni,S i and RE come second;the black brittle phaseθ(CuAl2)and the macrosegregation flocculent phase g o a2 gainst the per formance of joint,but the matrix phaseα(Al)with face2centered cubic s olid s olution and the S i phase with conglobula2 tion make the per formance of joint better.

K ey w ords:　orthog onal test;spreading property;melting point;microstructure

E ffect of zinc coating on arc heating beh avior for joining Al and zinc coated steel by w elding2brazing process ZH ANG H ong2 tao1,FE NGJicai2,HE Peng2,ZH AO H ongyun1(1.School of Mate2 rials Science and Engineering,Harbin Institute of T echnology at Weihai,Weihai264209,China;2.School of Materials Science and

ⅡMAI N T OPICS,ABSTRACTS&KEY W ORDS2009,V ol.30,N o.8

Engineering,Harbin Institute of T echnology,Harbin150001,Chi2 na).p37-40

Abstract:　The effect of the zinc coating on the arc heating behavior was studied by the arc shape visual sensing system and v olt2 age and current collecting system.The results show that the zinc coating can stabilize the arc as the plasma cathode during welding with lower current,but with the rise of the welding current the zinc coating will vaporize acutely,which make the arc edge ascend,and the contact area between the arc and the w orkpiece is lessened to re2 duce the heat input,which reduces the thickness of the inter facial brittle com pounds.

K ey w ords:　aluminium;zinc coated steel;welding2brazing; arc shape;heat input

Penetration state recognition of MIG w elding b ased on genetic w avelet neural netw ork WE N Jianli1,LI U Lijun2,LAN Hu1 (1.School of Materials Science and Engineering,Harbin University of Science and T echnology,Harbin150080,China;2.Ningbo In2 stitute of T echnology,Zhejiang University,Ningbo315100,China). p41-44

Abstract:　A netw ork m odel for penetration state diagnosis based on the signal characteristics of arc s ound in MIG welding is developed by recombining and im proving artificial neural netw ork, wavelet trans form,and genetic alg orithm.The arc s ound signals, which are denoised by using wavelet trans form and extracted by the frequency2band energy characteristics via wavelet packet decom posi2 tion and reconstruction,are used as the input eigenvectors of the wavelet neural netw ork m odel,the genetic alg orithm which has the ability of global optimization is adopted to dynamically m odify the netw ork structure and parameters and eliminate the rate tardiness of neural netw ork training and relapse into local extremum,and then the com plex nonlinear m odeling and data mining are accom plished. The penetration state diagnosis result of the trained netw ork m odel verifies the feasibility and validity of the m odeling methods.

K ey w ords:　wavelet trans form;neural netw ork;genetic al2 g orithm;penetration;pattern recognition

The new type of low sp atter and high energy w aveform control technology for short2circuiting w elding FE NG Y uehai1,LI U jia2,YI N Shuyan2,W ANG K ehong1(1.Department of Materials Science&Engineering,Nanjing University of Science and T echnolo2 gy,Nanjing210094,China;2.C ollege of Mechanical Engineer and Applied E lectronics T echnology,Beijing University of T echnology, Beijing100022,China).p45-48

Abstract:　The waveform control project is the key of realizing better control for C O2short2circuiting welding.F or the shortage of extension adaptability for constant2current waveform control project and the higher probability of transient short circuit occurring due to the bigger repulsion effect of droplet in arcing evening for constant2 v oltage waveform control project,a new waveform control method, NWC(natural waveform control),is brought forward.In order to re2duce the repulsion effect of the droplet and realize the natural short circuiting trans fer,the method not only adopts slope control m ode in arc period and short2circuiting period,but als o can automatically m odule waveform control parameters with the time and space in for2 mation for short circuit welding.The experiment results validate the NWC project has the characteristics of im proving the natural short circuit trans fer,g ood regular waveform control effect and better arc stability.

K ey w ords:　gas metal arc welding;digital control systems; short2circuiting trans fer;waveform control

Microstructure investigation on Type IV cracking in P92steel M A Chong1,2,J I NG H ongyang1,2,X U Liany ong1,2,X U Delu3, CHE N Y ucheng3(1.School of Materials Science and Engineering, T ianjin University,T ianjin300072,China;2.T ianjin K ey Labora2 tory of Advanced Joining T echnology,T ianjin300072,China;3. China E lectric P ower Research Institute,Beijing100192,China).p 49-52

Abstract:　The microstructures and hardness distribution of P92welded joint was analyzed,and the creep damages of the joints were observed under various times of creep tests at650℃and70 MPa.I t was found that no obvious creep damage was observed in the all zones of P92welded joints for the3000h creep specimen,many creep v oids occurred in fine grain heat2affected zone and intercritical heat2affected zone regions and no creep v oids were found in the coarse fine heat2affected zone and the weld metal in4032h creep specimen,the v oids grew up and tend to coalesce in7000h s peci2 men,and micro fissures began to form in7026h s pecimen.T here2 fore,this creep fracture could be clearly identified as T y pe I V crack2 ing.

K ey w ords:　P92;welded joint;T ype I V cracking;creep; microstructure

Improvement of joint brazability of aluminum alloys to stainless steel in the air LI U Shuying1,S UZ UM URA Akio2,IKESH O J I T oshi T aka2,Y AM AZ AKI T akahisa2(1.Henan Province K ey Labo2 ratory of Advanced N on2Ferrous Metals,Henan University of Science and T echnology,Luoyang471003,China;2.G raduate School of Science and Engineering,T oky o Institute of T echnology,T oky o1522 8550,Japan).p53-56

Abstract:　Based on the numerical analysis of is othermal s o2 lidification process of brazing filler on pure aluminum and the esti2 mate and experimental results of disappearance time of the m olten brazing layer,the experiment of brazing joint is processed by electric furnace after understanding of the poor brazability between the alu2 minum alloys and stainless steel.The quality of brazing joint is eval2 uated by T C M10000universal testing,and then the methods of the im proved brazability between aluminum alloys and stainless steel and the wider brazing gap in joint position are suggested,which include brazing filler metal wetting on the sur face of stainless steel and braz2 ing the aluminum alloys.The experimental results of m ore com plex

2009,V ol.30,N o.8TRANS ACTI ONS OF THE CHI NA WE LDI NG I NSTIT UTI ONⅢ