气保护药芯焊丝熔滴过渡的形式及特点(精)

气保护药芯焊丝熔滴过渡的形式及特点
3
李桓曹文山陈邦固孙小兵
33
(天津大学天津300072
摘要根据气保护药芯焊丝的特点,设计了以激光为背光的高速摄影试验。

基于试验结果,总结出了药芯焊丝熔滴过渡的各种形式及存在条件并分别做了描述,阐述了药芯焊丝熔滴过渡的特点。

认为药芯焊丝的熔滴过渡形式与实芯焊丝相比,既有共同点,又有不同点。

与实芯焊丝熔滴过渡过程相比,药芯焊丝熔滴过渡的特点是:焊丝端部与熔池之间始终存在着半熔化状态的渣柱,其长度取决于药芯材料的熔点。

由于熔滴可附着于渣柱周围以附渣的形式进行过渡及渣柱的导向性等,因此除短路过渡以外,渣柱在一定程度上有利于稳定熔滴过渡过程和减少飞溅。

关键词:药芯焊丝气保护熔滴过渡中图分类号:TG403
李桓
0序言
药芯焊丝是近年来国际上迅速发展起来的一种
新型焊接材料。

国内对药芯焊丝的研究和开发也正处于高速发展的时期,已取得一定成果。

但对药芯焊丝焊接过程的深入研究还开展得不多。

本文利用高速摄影的试验手段,对药芯焊丝的熔滴过渡行为做了研究,总结出了气保护药芯焊丝的各种熔滴过渡形式及其特点。

1试验方法
本文采用高速摄影的方法[1]对药芯焊丝的熔滴过渡行为做了研究。

图1为高速摄影试验的装置及光路示意图。

它由四大部分组成,即光源部分、扩束部分、成像部分及摄影部分。

(1光源部分:即图1中的激光源,使用的是波长为6.328×10-7m 的氦-氖激光器;
图1高速摄影装置及光路示意图
Fig.1Device of high -speed photographing and optical p ath
(2扩束部分:由显微目镜及凸透镜的扩束镜,即图1中的透镜1、透镜2;
(3成像部分:包括焊丝、成像物镜、小孔光阑、干涉滤光片。

成像物镜即图1中的透镜3,干涉滤光片的中心波长为6.328×10-7m ;
(4摄影部分:高速摄影主机,即图1中的摄影机。

主要器件的性能:
激光器:是由北京科学仪器厂生产的H N -T 4
型氦-氖激光器,波长为6.328×10-7m ,最大功率40mW ,试验中使用的功率为24mW ;
高速摄影机:选用原民主德国生产的Pentazet35型35mm 标准底片高速摄影机,最高摄影频率为2000幅/s 。

试验中使用的摄影频率为750幅/s 。

收稿日期:1998-09-21
3国家自然科学基金资助项目(59571066。

33参加本项研究工作的还有张文钺、雒玉岐。

焊接工艺参数如下。

干伸长:20mm ;
保护气体流量:20L/min ;
第21卷第1期2000年3月
焊接学报
TRANS ACTI ONS OF THE CHI NA WE LDI NG I NSTIT UTI ON
Vol.21No.1March 2000
焊丝直径:<1.2mm;
极性:直流反接;
焊机型号:天津市电焊机厂生产的G D-500型C O2气体保护半自动焊机;
送丝机型号:新乡市电气控制设备厂生产的S86A型送丝机。

试验用的药芯焊丝为天津三英焊业有限公司生产的S Q J501、韩国现代公司生产的SF-71和自行研制的Y an507。

试验中还用到了实芯焊丝作为对比,试板材料为Q235钢。

2药芯焊丝熔滴过渡的形式
选取不同的电流、电压、保护气体进行焊接,做了大量高速摄影试验。

然后将所得底片进行整理、分析和归纳,得出如下结论。

同实芯焊丝[2]类似,药芯焊丝的熔滴过渡形式也有如下几种:①大滴排斥过渡;②细颗粒过渡;③射滴过渡;④射流过渡;⑤短路过渡。

这几种过渡形式的形成条件和过渡状况如表1所示。

其中细颗粒过渡是主要的过渡形式,其形成条件为:C O2气保护,焊接电流240A,电弧电压30V,焊丝直径<1.2mm。

2.1大滴排斥过渡
当焊接电流较小和电弧电压较高(160A,30V时,弧长较长,熔滴不易与熔池短路。

因电流较小,弧根面积的直径小于熔滴直径,熔滴与焊丝之间的电磁力不易使熔滴形成缩颈。

斑点压力也阻碍熔滴过渡。

随着焊丝的熔化,熔滴长大,其重力克服表面张力的作用形成大滴状熔滴过渡(熔滴直径为焊丝直径的2.5倍。

表1药芯焊丝熔滴过渡形式、形成条件及过渡状况
T able1Metal transfer p atterns,their existing conditions and description
T rans fer patterns
Existing conditions Description
T ypes of
gases
W elding
currents I/A
Arc
v oltages u/v
W ire feeding
speeds v/(m・min-1
S izes of metal
drops(times of the
wires diameter
Frequencies of
trans fer
(drops・s-1
Repelled globular CO2160307.2 2.514 Small drop CO22403011.0 1.524 Projected spray Ar2703215.00.96162 S treaming spray Ar2903515.80.43244 Short-circuiting CO216020 6.4 1.168
试验中用的是C O2保护气体,而C O2气体高温分解吸热对电弧有明显的冷却作用,使电场强度增高,电弧收缩,弧根面积减小,增加了斑点压力对熔滴过渡的阻碍作用,最终形成大滴状排斥过渡。

典型照片如图2a所示。

2.2细颗粒过渡
在C O2气体保护情况下,随着焊接电流的增加(至240A,斑点面积也增加,熔滴所受的等离子流力和电磁力增加,熔滴过渡频率也增加(为24滴/ s。

这时,熔滴直径为焊丝直径的1.5倍左右,属于细颗粒过渡。

典型照片如图2b所示。

过渡时,会出现熔滴这一次在左,下一次在右的位置交替现象,典型照片如图2c所示。

这种现象是由于未完全熔化的渣芯阻挡了熔滴向焊丝根部的热传递造成的。

试验中还发现,相同电流、电压情况下,药芯焊丝的熔滴尺寸比实芯焊丝小,这说明药芯焊丝比实芯焊丝容易形成细颗粒过渡。

药芯焊丝的这种过渡形式飞溅较少,电弧稳定,焊缝成形好,所以在生产和试验中得到广泛应用。

也就是说,细颗粒过渡是药芯焊丝熔滴过渡的主要形式。

2.3射滴过渡
使用Ar作保护气体时,用<1.2mm的药芯焊丝,270A,32V,会出现射滴过渡。

过渡时,熔滴直径接近于焊丝直径(0.96倍焊丝直径,熔滴脱离焊丝沿焊丝轴向过渡,形成熔滴“抱着”渣芯向下滑落的状态。

这时的过渡频率为162滴/s。

典型的高速摄影照片如图2d所示。

形成射滴过渡的原因是,使用Ar作保护气体时,弧根面积扩大并包围熔滴,使斑点压力和电磁收缩力都有利于熔滴过渡,只有表面张力对熔滴过渡起阻碍作用。

这种情况下,熔滴容易下落,并被电磁收缩力、等离子流力、重力等加速,形成射滴过渡。

这时熔滴下落的加速度远远大于细颗粒过渡时熔滴的加速度。

2.4射流过渡
使用Ar作保护气体,用<1.2mm的药芯焊丝, 290A,35V时,会出现射流过渡。

典型的高速摄影照片如图2e所示。

这时,熔滴直径为焊丝直径的0.43倍,过渡频率为244滴/s。

基本上每次过渡一
41焊接学报21卷
滴,但偶尔会出现一次过渡两滴的现象。

一次过渡
两滴时,熔滴呈一左一右的位置。

此时熔滴下落的加速度比射滴过渡时还要大。

图2药芯焊丝的熔滴过渡
Fig.2Metal transfer of flux -cored wire
不难发现,药芯焊丝的射流过渡与实芯焊丝的射流过渡有很大区别。

最主要的区别就是,实芯焊
丝的端部呈明显的“铅笔尖”状;而药芯焊丝则由于未完全熔化的渣芯的阻挡,所谓“铅笔尖”状只形成了一半,甚至不到一半(见图2e 。

“铅笔尖”其实被渣芯阻挡住了,在阻挡处可以看到,液态金属变成散碎的小滴,沿渣芯一侧快速滑落进入熔池。

2.5短路过渡
在较小电流低电压(160A ,20V ,C O 2气保护时,熔滴尚未长成大滴就与熔池短路,在表面张力与电磁收缩力的作用下,熔滴向母材过渡,形成短路过渡。

典型高速摄影照片如图2f 所示。

此时,熔滴直径约为焊丝直径的1.1倍,平均过渡频率为68滴
/s 。

这种过渡形式在实芯细焊丝(<0.8~1.6mm 气保护焊时,电弧稳定,飞溅较小,焊缝成形较好,广泛应用于薄板和全位置焊接过程。

而对于药芯焊丝,由于渣芯的存在,使其在短路爆断的瞬间容易产生
飞溅,所以这种过渡形式却不是最好的过渡形式。

3药芯焊丝熔滴过渡的特点
3.1药芯焊丝熔滴过渡的特点
与实芯焊丝熔滴过渡过程相比,药芯焊丝熔滴过渡的特点是:焊丝头与熔池之间始终有半熔化状态的渣柱存在。

根据药芯焊丝品种的不同,渣柱长短有所差异,即药芯熔点低者渣柱较短;药芯熔点高者渣柱较长。

除短路过渡以外,此渣柱不影响正常
的熔滴过渡,相反,熔滴粘着于渣柱之上,以附渣的状态进行各种过渡,这对于减少飞溅大有益处。

即,一定程度的药芯滞熔不影响正常的熔滴过渡。

细颗粒过渡时,典型的熔滴照片如图3所示,图中可清晰地看出熔滴、渣柱、电弧共存的情况。

图3高速摄影熔滴照片
Fig.3Photo of transferring metal drop
CO 2-shielded ,240A ,30V ,<1.2mm
3.2药芯滞熔的允许程度
上文提出,一定程度的药芯滞熔不影响正常的熔滴过渡。

但是,文献[3,4]认为,应尽量减小药芯滞熔程度。

那么,药芯滞熔的程度到底多大为好呢?根据本文所做试验,认为:(1渣柱刚好接触熔池时过渡最稳,如图4a 所示。

这种情况下,渣柱端部与熔池接触的同时刚好完全熔化,熔化的液态渣随即流入熔池,于是渣柱形成一个稳定的渣桥,金属熔滴
5
11期气保护药芯焊丝熔滴过渡的形式及特点
顺着渣桥滑落进入熔池;(2渣柱还没有接触到熔池
时就已熔化,这时往往在渣柱端部形成一个液态渣滴,如图4b 。

当金属滴下落时往往将此渣滴带落进入熔池,增加对熔池的冲击力,易导致飞溅;(3渣柱进入熔池,进入熔池的渣柱在熔池热的作用下熔化、分解,分解出的气体会造成崩溅,而未完全熔化部分会造成夹杂等,如图4c。

图4
药芯的滞熔程度示意图
Fig.4Melt -retard ation of core column
4结论
(1按形成条件的不同,药芯焊丝的熔滴过渡
可分几种形式:①大滴排斥过渡;②细颗粒过渡;③
射滴过渡;④射流过渡;⑤短路过渡。

细颗粒过渡时焊接过程稳定,飞溅小,焊缝成形良好,生产效率较高,因此细颗粒过渡应是药芯焊丝熔滴过渡的主要形式。

(2药芯焊丝熔滴过渡的特点是:焊丝头与熔池之间始终有半熔化状态的渣柱存在。

但是,除短路过渡以外,此渣柱不影响正常的熔滴过渡。

当渣芯有适当的滞熔时,有利于药芯焊丝的熔滴过渡。

参考文献
1李桓.CO 2气体保护焊无爆短路过渡控制研究:[博士学位论文].
天津:天津大学,1997.
2姜焕中.电弧焊及电渣焊.北京:机械工业出版社,1988.
3陈邦固,雷万钧.“滞熔”现象对碱性气保护药芯焊丝飞溅的影响.
焊接技术,1995,6:4~5
4陈邦固,曹文山,等.药粉预熔对改善药芯焊丝滞熔现象的作用.
焊接,1998,3:16~18
作者简介李桓,男,1955年7月出生,博士学位,副教授;从
1986年起在天津大学焊接专业任教,现担任中国焊接学会焊接物理
委员会副主任职务。

研究方向为焊接电弧物理、焊接工艺及设备等,承担过国家自然科学基金委员会、国家教育部、天津市科委及石油天然气总公司等许多重要课题并多次获奖,取得国家专利4项,发表论文30余篇。

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在哈尔滨市政府大力支持下,由哈尔滨焊接研究所、中国焊接协会、中国机械工程学会焊接学会、国家焊接材料质量监督检验中心、机械工
业火焰切割机械产品质量监督检测中心联合创办的哈尔滨现代焊接技术发展中心已正式运营,创办这一中心的目的是建立一个全国性的焊接技术信息中心、焊接器材商务中心和焊接行业活动中心。

本“中心”设有各种格局的临街铺面、展示大厅、各种开间的写字间及可举办各种会议的多功能大厅。

其中,焊接器材、焊接技术展示大厅
约200m 2
,设有几十个展位,常年为焊接材料、焊接设备、焊接检验设备制造厂家展示最新产品和高新技术,包括企业形象的宣传。

展示厅招展有关事宜如下。

●展示时间常年展出,从即日起参展产品随到随展,从展出之日起计算展费。

●展示费用
实物展品展示费按占地面积计算,定价每年1500元/m 2;立式展板每块(800mm ×1200mm 1000元/年;音像资料展示500元/年。

临街广告灯箱每个3000元/年。

●展品范围 1.电弧焊设备及弧焊电源;2.电阻焊设备;3.电子束焊设备;4.激光焊接与切割设备;5.热喷涂设备及辅具;6.钎焊设备、材料及
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取。

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MAIN TOPICS,ABSTRACTS&KE Y WOR DS
Mech anism of Laser Welding for SiCw/6061A l Composite Niu Jitai (Harbin Institute of T echnology,Harbin,China,W ang Muzhen,Lai Zhonghong,et al.p1~4
Abstract:S iC w/6061Al com posite was welded by pulse laser welding success fully.The in fluence of the parameters such as surface treatment state, laser output power,welding speed,protective atm osphere,and pulse frequency on the welding quality was studied.The results show that laser output power and welding speed are the main factors which affect the microstructure and the property of weld,and change of laser pulse frequency has the definite in flu2 ence on them.H owever,surface treatment state has little in fluence on the properties of joint.At the same time,we obtained g ood effect by using nitrogen gas instead of arg on gas.The microstructure of joint was observed and the strength loss of joint was analyzed by SE M and TE M.The main reas on for the decrease of the strength of welded joint is that when laser welding was used, S iC whisker reacted with Al to form brittle Al4C3.Therefore,the conception of the critical activityα[Si]min was put forward.
K ey w ords:aluminum matrix com po site,laser welding,critical activity α
[Si]min
Study on the T echnique of N eural N etw ork and Fuzzy Control for GTAW G ao X iangdong(S outh China University of T echn ology, G uang zh ou,China,H uang Shisheng,W u Naiy ou.p5~8
Abstract:An intelligent system including both neural netw ork and fuzzy controller for the gas tungsten arc welding(G T AWwas presented in this pa2 per.The discussion was mainly focused on the application of neural netw ork and fuzzy logic in m odeling and controlling the penetration depth as well as the seam tracking.A visual sens or CCD was used to obtain the image of the m olten pool.A neural netw ork m odel was established to estimate the penetra2 tion depth based on the welding current,pool width and seam gap.Als o,the fuzzy logic technique was combined to prom ote the control accuracy of pene2 tration depth.It was dem onstrated that the proposed neural netw ork could pro2 duce highly com plex nonlinear multi2variable m odel of the G T AW process and thus it offered the accurate prediction of welding penetration depth.It was dif2 ficult to obtain the accurate m odels of the actuators,in that the torch drivers were extremely com plex systems which had highly nonlinearity.In order to re2 s olve this problem,a self2adjusting fuzzy controller to control the torch m otion was proposed,which was used for seam tracking.The self2organizing artificial neural netw ork alg orithm was used to detect the weld position.The control pa2 rameters were adjusted on2line automatically according to the tracking errors s o that the tracking errors could be decreased sharply.The experimental re2 sults showed that the proposed system yielded conspicuously controlling perfor2 mance and provided an efficient approach to realize the intelligence of G T AW process.
K ey w ords:neural netw ork,fuzzy control,G T AW,pool depth,seam tracking
H AZ Structure,Toughness and Ch aracteristics to H ydrogen2I nduced
Cracking(HICof Steel20MnN iMo Zhang X ianhui(Harbin Research Institute of W elding,Harbin,China,Jiao W ei,T an Changying.p9~12 Abstract:In this paper the effect of the cooling condition during welding on H AZ structure,toughness and susceptibility to
Hydrogen2Induced Cracking (HICof steel20MnNiM o was studied.The experimental results showed that the cooling rate t8/3considerably affected both the H AZ toughness and the susceptibility to HIC.The M or M with a little B structure in H AZ and better low tem perature toughness were obtained,when t8/3was less than55s.H owev2 er this structure was sensitive to HIC.In order to av oid HIC and get better toughness in H AZ,the lower heat input,lower tem perature preheating and hy2 drogen rem oval prom ptly after welding were recommended.
K ey w ords:H AZ,structure,toughness,hydrogen2induced cracking
Metal T rans fer of G as Shielded F lux2cored Wire and I ts Ch aracteristics Li Huan(T ianjin University,T ianjin,China,Cao W enshan,Chen Bang2 gu,et al.p13~16
Abstract:According to the metal trans fer particularity of gas shielded flux2cored wire,the high2speed photographic experiments with the laser as back light were designed,on which the metal trans fer patterns and their exist2 ing conditions were summarized and described,respectively.M oreover,the characteristics of metal trans fer were clarified.C om pared with the trans fer of
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2000,V ol.21,N o.1TRANS ACTI ONS OF THE CHI NA WE LDI NG I NSTIT UTI ON
MAIN TOPICS ,ABSTRACTS & KEY WORDS 2000 ,Vol. 21 ,No. 1 Ⅵ solid wire ,the metal transfer of flux2cored wire has such particularities : there Zhangui ,et al . p17～20 Abstract :The shielded metal arc welding (SMAW of a high manganese steel part as a frog of railway track to a high carbon steel part as rails of the Process Han Zandong ( Tsinghua University ,Beijing , China ,Du Dong , Zhang Renhao. p21～24 K
words :flux2cored wire ,gas shielded ,metal transfer ey K words :rail and
frog ,SMAW ,process method ey Electrode Sun Xian ( Taiyuan University of Technology ,Taiyuan ,China , Bai Y ingbin ,Liu Mingliang ,et al . p25～29 Abstract :The droplet transfer characteristics and its influence factors of typical stainless steel electrodes are studied with experimental methods includ2 in fining droplet . The droplet will become fine when coating thickness and limited by maximum admitted silicon content . The basicity ,constituents and ble increasing silicon content of electrode is proposed. Di (South China University of Technology , Guangzhou ,China ,Song Y onglun , Ye Feng ,et al . p30～33 nize feature Map (SOM neural networks. Experiments show that this strategy realizes effectively the identification of weld defects and can be used in the sive usability as the droplet transfer exponent optimizes and the flux2wall guid2 content of welding slag have a certain influence upon the transitional charcter2 K words :droplet transfer ,stainless steel electrode ,influence factor ey Identification of Weld Defects in GMAW Based on Arc Sensing Li Abstract :CO2 gas shielded arc welding is widely used in automatic and robotic welding. The automatic monitoring of weld quality is a problem that arc welding process. It is based on the feature extraction for the arc signals by could be applied in process and quality real2time control where metal transfer must be exactly detected. Meanwhile ,the reason and theoretical explanation of needs urgently solved in industry. Through2the2arc sensing ,due to its advan2 This paper presents a monitoring method of weld defects for CO2 gas shielded Self2Organize feature Map (SOM Reflection of Metal Droplet Transfer Liu Gang ( Tianjin University , Tianjin ,China ,Li Junyue , Yang Lijun ,et al . p34～36 new sensoring method of metal transfer , this paper provided the parasyn2 speed photography apparatus. The testing result shows that the pulses in spec2 K words :welding arc spectrum ,metal transfer ,pulse characteristics , ey Abstract :On the basis of cognition of the potential significance of weld2 K words :welding , quality , through2the2arc sensing , signal features , ey speed camera etc. The results show that the electrode has the best comprehen2 is always an incompletely melting slag column between the end of electrode the short ciruiting transfer is in progress smoothly. quirements for welding technology.
The SMAW method was used to solve those tained and the carbides had not been precipitated. Meantime ,the problems of welding deformation and residual stress was also solved. ters and thereby changing arc time ,droplet transfer frequency was controlled. justing wave parameters when the wire extension varied in welding process , trol ,PID control problems by increasing the thickness of the intermediate layers and using U2 rials were surfaced on the base metals at first ,and then two pieces of base were used too. The test results indicated that the good welded joint was ob2 Fuzzy and PID Control of Droplet Transfer Frequency in CO2 Welding Abstract :On the basis of microcomputer controlled IG inverter power BT veloped in CO2 welding process. The system structure , control principle and quency ,while the PI control method was adopted for smaller error. The control parameter self2study function was realized in fuzzy control process. G ood dy2 namic responsibility and static precision were ensured when welding condition and welding parameters were changed. Welding experiments showed that this eters. Research on Droplet Transfer and Its Influence Factors of Stainless Steel K words :CO2 welding process ,droplet transfer frequency ,fuzzy con2 ey control algorithm were introduced in this paper. By adjusting the wave parame2 and the control effect didn’ depend on the preset value of the control param2 t system ensured the stability of droplet transfer frequency by automatically ad2 The fuzzy control method was adopted for bigger error of droplet transfer fre2 source ,the fuzzy and PID control system of droplet transfer frequency was de2 groove symmetrical welding. The intermediate layer of rail sides was Ni2Cr2Mo alloy system ,and that of frog side was Mn2Cr2Ni alloy system. All these mate2 metals with intermediate layers were welded together. Other special procedures and welding pool ,and its length depends on the melting point of flux2cored column has guiding property for the metal transfering ,the slag column ,in some extent ,is favorable to stabilizing metal transfer and decreasing spatter while railroad is the welding of dissimilar steel . It is difficult to weld them together , material . Because the melt2drop may adhere to the slag column ,and the slag Welding of R w R and Manganese Steel Frog Guo Mianhuan ail ay ail ing collecting droplet into water ,surfacing on the plate and
analyzing by high ed transfer form occurs. The SiO2 in coating can play the most important part ( Harbin Institute of Techndogy , Harbin , China , Shao Dechun , Dong because the poor weldability of the two kinds of steels and their different re2 on2line monitoring of welding process. It is very improtant for the welding pro2 cess in achieving the aim of“zero defect ” products. ing arc spectrum dynamic characteristics and with the destination to find out chronous principle and in turn verified the relationship between the pulses in the waveform of arc spectrum signals and metal droplet transfer with para2high trum waveform were correspondingly brought up by droplet transfer ,the pulses pulse appearance were given. istics of droplets too. The concept of droplet essential mass ratio and permissi2 tages in practical applications ,gets more and more concerns in recent years. welding current increase ,but it is restricted by usability of electrode. The sili2
con2reducing reaction in the droplet stage benefits droplets fining , but it is the classification of signals’ histogram in the welding process using Self2Orga2 N ature of Pulse Waveform of MIG/ MAG Welding Arc Spectrum ———。