Experimental Study on Metal Transfer and Welding Spatter Characteristics of Cellulose Electrode

Welding spatter cause many problems during the welding process and this issue is particularly important for cellulose electrode welding. The hot flying spatter balls often deteriorate the working environment, and decrease the welding efficiency. Many factors affect the welding spatter, and metal transfer behavior is one of the main factors. Many studies concerning the spatter mechanism in arc welding process were made; most of them focused on the solid wire welding and the study on cellulose electrode is rarely reported. In this paper the metal transfer behavior and the weld spatter characteristics of three commercial cellulose electrodes were studied experimentally by using a high speed camera for visually capturing the metal transfer. The relationship between the metal transfer and the welding spatter was analyzed experimentally by comparing the spatter loss coefficient, which is for quantitative evaluation of welding spatter, with the statistical analysis of the large droplet transfer mode. The results showed that short circuiting transfer, large droplet spray transfer, fine droplet spray transfer and explosive transfer govern the metal transfer modes in cellulose electrode welding. Weld spatter occurred mainly in the deflection of large droplet process, explosive transfer process and fine droplet spraying process. Different metal transfer modes lead to different spatter. The deflection of large droplet and explosive transfer are the main factors of the spatter formation. Minimizing the droplet size and reducing the deflection of large droplet and explosive transfer leads to the reduction the amount of spatter in cellulose electrode welding.

EXPERIMENTAL STUDY ON METAL TRANSFER OF CELLULOSE ELECTRODE IN VERTICAL DOWN WELDING

A high-speed photographic method is mainly used to analyze metal transfer ofa cellulose covered electrode in the vertical down welding. The experimental results show that finedroplets spraying transfer and globular transfer are the dominant transfer characteristic. The largedroplet spatter, especially the upwards spatter, is a particular phenomenon. It is found that thecombination action of gas blow force, surface tension, gravitational force and electromagnetic forcelead to globular transfer. Gravitational force and electromagnetic force, which hasten big dropletspatter, should not be neglected.

Study on arc characteristics and behavior of metal transfer in pulse current flux-cored arc welding of mild steel

The variation in arc characteristics and behavior of metal transfer with the change in pulse parameters has been studied by high speed video camera during pulse current flux-cored arc weld deposition.A comparative study of similar nature has also been carried out during flux-cored arc weld deposition in globular and spray transfer modes.The effect of pulse parameters has been studied by considering their mean current and arc voltage.The arc characteristics studied by its root diameter,projected diameter and length,and the behavior of metal transfer noted by the metal transfer model and the droplet diameter have been found to vary significantly with the pulse parameters.The observation may help in understanding the arc characteristics with respect to the variation in pulse parameters which may be beneficial in using pulse current FCAW to produce desired weld quality.

Arc Characteristic and Metal Transfer of Pulse Current Horizontal Flux-Cored Arc Welding

In this work, we utilized high-speed video photography to investigate the arc characteristics, metal transfer behavior, and welding spatter of the pulse-current flux-cored arc welding (P-FCAW) process in the horizontal position. The results indicate the presence of a stable “flux pole” during both the pulse-on and pulse-off periods when the mean current ranged from 140 to 170 A. The existence of this “flux pole” was beneficial for droplet transfer in the “axial droplet transfer” mode. With respect to welding spatter, with an increase in the welding current, we observed three kinds of spatter—explosive spatter, rebounded droplet spatter, and scattering spatter. With an increase in the pulse current from 310.6 to 345.6 A, the deflection of the arc reduced from 30.4° to 16.6°, which positively influenced the arc rigidity, particularly in the horizontal position. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

Effect of pulse M-Arc frequency on Tri-Arc DE droplet transfer and weld forming

In view of the unstable welding process of Tri-Arc DE,surfacing test with Q235 steel plate was completed with the help of the self-built high-speed camera and waveform synchronous acquisition system using the Tri-Arc DE technology. The effects of pulsed M-Arc frequency on Tri-Arc DE droplet transfer and weld formation were analyzed. The results show that while the gradual increase of pulse frequency,the droplet transfer frequency gradually decreases,which is followed by several drops per pulse,one drop per pulse,and one drop within several pulses. The most ideal transfer form is one drop per pulse,of which the welding process is the most stable,and the quality of weld formation is the most satisfied.

Welding characteristics of AZ31B magnesium alloy using DC-PMIG welding

Direct current pulsed metal inert-gas （DC-PMIG） welding was carried out on AZ31B magnesium alloy to obtain continuous welding joints of 3 mm and 8 mm thickness with 1.6 mm diameter of filler wire. The behavior and mechanism of metal transfer, the parameter ranges of stable welding process, the microstructure and mechanical properties of magnesium alloy were investigated. The results show that the metal transfer form of magnesium alloy using DC-PMIG welding is realized in modes of globular transfer, projected transfer and spray transfer. Welding spatter with a large size will be produced in the mode of globular transfer, and high-quality joints with few spatters can be obtained in the mode of projected transfer and spray transfer when the linear energy of filler wire is 242-27l J/cm, droplet diameter is 1.6-0.9 mm tensile strength of weld beads is 94.2% of that of base metals. and transition frequency is 30-69 Hz. The average ultimate

Study of porosity tendency in the Cr-Ni austenitic weld based on inclusion’s characteristic in the droplet

The effect of nonmetallic inclusions in the droplet of the stainless steel covered electrode on the porosity was researched.The result shows that the nonmetallic inclusions in the droplet are spherical,their composition is different from the one of slag and the inclusions have the character of “inner formation”.When the ratio of rutile to ilmenite in the coated material is increased, the droplet becomes coarse, the content of nonmetallic inclusion in the droplet decreases,and the porosity sensitivity in the weld metal also decreases.When the ratio of fledspar to ilmenite in the coated material is increased, the droplet becomes fine,the content of nonmetallic inclusion in the droplet increases, and the porosity sensitivity in the weld metal increases. When the ratio of Fe_2O_3 to ilmenite in the coated material is increased, the droplet becomes fine, the content of nonmetallic inclusion decreases, while the porosity sensitivity does not reduce.

焊条典型熔滴过渡形态的判读

粗熔滴短路过渡,渣壁过渡,爆炸过渡和喷射过渡是焊条的基本过渡形态。过去一直采用光电示波器记录的电弧电压、焊接电流波形图,定性地描述熔滴过渡的一般特征,不可能进行精确的定量分析。通过对汉诺威弧焊质量分析仪获取的焊条四种典型熔滴过渡形态的电弧电压、焊接电流概率密度分布图的特征和短路时间t1、燃弧时间t2、加权燃弧时间t3和过渡周期tC的数据进行统计分析,可精确地描述焊条熔滴过渡形态的电弧物理特征,并能够判别焊条熔滴过渡形态。为焊条熔滴过渡形态的判定提供了一种新方法。

双电极焊条熔滴过渡的特点及形式

用激光背光高速摄像系统研究了双电极焊条的熔滴过渡 ,阐述了双电极焊条熔滴过渡的特点 ,基于试验结果 ,总结了双电极焊条熔滴过渡的各种形式。双电极焊条单弧焊 ,工件不接电源 ,熔滴的过渡方向与电流方向不同 ,电弧对药皮的加热易于使焊芯两边药皮产生滞熔 ,形成两边尖中间凹的套筒形状 ,从而有利于熔滴以渣壁过渡形式过渡。钛钙型双电极碳钢焊条和不锈钢焊条具有渣壁过渡、喷射过渡和爆炸过渡等多种过渡形式 ,以细熔滴渣壁过渡为主 ,而石墨型堆焊焊条主要以粗熔滴渣壁过渡为主。

高纤维素型焊条熔滴过渡形态和工艺性分析

主要通过高速摄影方法和工艺性试验 ,对高纤维素型焊条立向下焊的熔滴过渡形态以及主要工艺性进行了试验分析。结果表明 ,高纤维素型焊条立向下焊时表现为混合过渡形态 ,有细颗粒和大颗粒喷射过渡 ,爆炸过渡 ,短路过渡。飞溅形式为大颗粒偏飞和小颗粒飞溅。大颗粒熔滴的形成、长大 ,直到发生过渡、爆炸或偏飞具有明显的周期性特征 ,而小颗粒的喷射过渡或飞溅则伴随焊条燃烧全过程。有规律的强喷射过渡形态有利于改善焊条工艺性 ,是高纤维素型焊条理想的过渡形态 ;大颗粒的偏飞是导致电弧不稳定、熔敷效率低等恶劣工艺性的主要原因 ,应该对此进行深入分析 ,防止其产生。

单电源双丝旁路耦合电弧熔化极气体保护焊工艺

针对常规双丝旁路耦合电弧熔化极气体保护焊(GMAW)的控制过程较复杂、焊接成本较高等问题,提出了采用单电源实现双丝旁路耦合电弧GMAW的方法,并设计了采用快速原型技术的实验系统.同时,进行了大量焊接工艺实验.实验结果表明:采用单电源的双丝旁路耦合电弧GMAW可以稳定焊接,但相对于双电源的双丝旁路耦合电弧GMAW其稳定工作区间更窄;通过调节旁路送丝速度快慢的焊接工艺实验,分别找到了在主路电流为300、350、400、450、500、550A时旁路送丝速度的稳定工艺区间.

自适应恒频短路过渡焊接过程的控制系统

短路过渡焊接时，熔滴过渡频率通常被作为评价焊接过程稳定性及焊接质量的重要指标。本文首先根据短路阶段电源输出电阻的变化曲线，确定了有利于消除瞬时短路及提高熔滴过渡规则性的短路过渡焊接控制电流波形。其次鉴于干伸长电阻热对过渡频率的影响，提出了通过短路过渡中期电源输出阻抗实时检测焊丝干伸长，采用干伸长变化前馈补偿干伸长电阻热对过渡频率影响的方法。最后利用ＭＣ６８ＨＣ１１Ａ１ 单片机建立了焊丝干伸长变化前馈—过渡周期负反馈恒频短路过渡控制系统。试验表明，恒定频率的短路过渡焊接飞溅小，焊接过程稳定，焊缝质量良好，且改变目标过渡频率可以控制熔滴尺寸及焊缝成形。

不锈钢焊条熔滴过渡形态与焊接冶金学的相关性

采用高速摄影、平板堆焊等试验方法,研究了典型金红石型不锈钢焊条熔滴过渡形态及其与焊接冶金学的相关性。结果表明,金红石型不锈钢焊条有渣壁过渡和混合过渡两种基本过渡形态,前者使焊条的综合工艺性极佳;后者随混合过渡中短路过渡成分的增加,焊条工艺性变差,常用的熔滴过渡形态评定方法有4种。两种熔滴过渡形态焊接冶金学特征差别在于:前者具有特大反应相界面等更有利条件,较后者冶金反应更激烈。熔滴过渡区的冶金反应对熔滴过渡形态的影响,很大程度受熔滴增Si量控制,熔滴增Si量较高时,熔滴的表面张力γD减小,熔滴易被细化,有利于形成渣壁过渡;反之,熔滴的γD较大,熔滴较粗,难于形成渣壁过渡。提出"熔滴过渡形态对气孔影响理论",凡是促使熔滴尺寸变化的因素,都将通过冶金原理对气孔产生影响,其影响规律与熔滴大小存在对应关系。

不锈钢焊条工艺稳定性分析与评价

焊条渣壁过渡形态的倾向大小是衡量不锈钢焊条工艺稳定性的主要标志。利用汉诺威弧焊分析仪对不锈钢焊条的焊接电参数进行测试分析,提取短路电压概率密度和、平均电弧电压、平均焊接电流和短路频率等与不锈钢焊条渣壁过渡倾向大小有关的4个特征信息,然后采用主成分分析法确定不锈钢焊条工艺稳定性评价指数。研究结果为定量判断不锈钢焊条熔滴过渡形态和科学评价不锈钢焊条工艺稳定性提供了新方法。

焊接电流对不锈钢焊条熔滴过渡及熔滴中夹杂物的影响

采用水中收集熔滴、光学显微分析、电子扫描能谱分析、计算机图象分析及平板堆焊等试验方法 ,研究了焊接电流对E30 8- 16不锈钢焊条熔滴中夹杂物的影响 .结果表明 ,焊接电流增大时 ,焊条的熔滴质量比和熔滴的平均质量减小 ,熔滴的过渡频率增高 ,熔滴中非金属夹杂物含量增大 ,焊缝中的气孔率与熔滴中夹杂物含量之间不存在严格的规律性对应关系 ;熔滴中非金属夹杂物是熔滴区化学反应的产物 ,属“内生”性质 .

药芯焊丝电弧焊熔滴过渡与焊接飞溅

针对不同焊接参数下SQJ501型、SQJ507型和SQJ50MX型药芯焊丝电弧焊的熔滴过渡行为进行了拍照,并对焊接飞溅进行了测量,研究药芯焊丝电弧焊的熔滴过渡行为及其焊接飞溅的基本规律。试验结果表明:三种药芯焊丝随着焊接参数的增大,均依次发生短路过渡、大滴排斥过渡和细颗粒过渡。SQJ501型和SQJ50MX型药芯焊丝电弧焊电弧形态呈锥形,SQJ507型电弧形态接近于钟形。SQJ507型药芯焊丝出现细颗粒过渡的焊接参数比其他两种焊丝大。焊接工艺参数以及焊丝种类影响了熔滴过渡行为进而影响焊接飞溅,细颗粒过渡时产生的飞溅最小。

焊丝直径和保护气体对GMAW熔滴过渡形态的影响

综述了焊丝直径和保护气体对GMAW熔滴过渡影响的新发现。研究表明,对于直径小于0.90 mm焊丝,转变电流后熔滴的平均直径并未小于原来的焊丝直径。随着焊丝直径的减小,临界电流呈减小趋势,但超细焊丝未测出这种趋势。直径小于0.90 mm的焊丝,增大电流不发生转变,是因为焊丝直径不能明显改变阳极斑点面积,电弧无法爬上熔滴。CO_2对较细焊丝熔滴过渡转变的影响,并未遵循随着CO_2含量的增大,转变电流提高的一般焊丝的模式。无论焊丝直径如何,用含30﹪以上的CO_2保护气体时,排斥过渡仍占主导地位。

焊条电弧焊电弧物理及化学冶金若干问题

通过焊条熔化和熔滴过渡的基础研究,分析了不锈钢焊条发红开裂的问题,把一个焊条工艺问题转化为电弧物理的研究问题予以解决,说明焊条研制中基础研究的重要性,同样也阐述了碱性焊条飞溅的问题要由其化学冶金的基础研究来解决,文中也示出了电弧物理及化学冶金研究的方法和装置以及研究得到的主要结果。

压力对水下焊条局部干法焊接电弧稳定性的影响

在压力舱中进行不同压力下的水下焊条局部干法焊接试验，采用统计分析和快速傅立叶变换研究了压力对水下电弧稳定性的影响．结果表明，铁粉低氢钾型焊条焊接主要进行粗熔滴短路过渡，随着压力的增加，短路时间由常压焊接的5-7ms增加到8～10ms，表明熔滴的平均尺寸增大．压力环境下，焊条熔化速度增大，弧压反馈调节系统的工作点上移，电弧电压增大．傅里叶变换结果表明，常压电弧电压信号的主要特征频率低于10Hz，压力下电压信号的频谱图中出现大量高于10Hz的谱线，说明信号突变性更强，电弧稳定性降低．

高纤维素型焊条熔滴过渡特性的研究

采用立焊条件下的高速摄影装置，拍摄了纤维素型焊条的熔滴过渡形态。通过观察、分析，确定ＴｉＯ２－ＳｉＯ２－ＭｇＯ渣系纤维素型焊条熔滴基本过渡类型为喷射过渡，同时还对影响焊条熔滴过渡形态的因素进行了探讨。