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E308-16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.     

氟化物对不锈钢焊条工艺性及熔滴过渡特性的影响

采用水中收集熔滴，平板堆焊，高速摄影等试验方法，研究了氟化物对不锈钢焊条工艺性及熔滴过渡特性的影响。结果表明，多种氟化物同时加入能减弱焊条工艺性恶化程度和熔滴粗化倾向，并可提高氟化物的熔滴过渡形态转变量；ＣａＦ２加入量增大时，焊缝中的气孔倾向减小。     

不锈钢焊条熔滴过渡形态与交流稳弧性的关系

采用水中收集熔滴、平堆板焊、高速摄影等试验方法，研究了不锈钢焊条熔滴过渡形态与交流稳弧性的关系。结果表明：细熔滴过渡时交流稳弧性好，电极斑点面积增大是改善交流稳弧性的主要原因；促使熔滴细化的药皮组成物、适当的药皮厚度、合理的焊条烘干温度和合适的焊接电流，对改善交流稳弧性都具有重要作用。     

ZrO_2对不锈钢焊条工艺性能的影响

在国产不锈钢焊条配方基础上添加新成分ＺｒＯ＿２，通过测定焊条表面温度、熔滴尺寸以及用高速摄影法观察熔滴过渡形态，探讨了ＺｒＯ＿２对焊条工艺性能的影响。试验证明，焊条药皮中加入约４％的Ｚｒｎ＿２将使熔滴尺寸细化，表面温度下降；焊条综合工艺性能明显改善。     

低合金耐热钢焊条CJR307的电弧特性与熔滴过渡行为研究

研究了金红石对低合金耐热钢焊条CJR307的电弧特性及熔滴过渡行为的影响规律。结果显示,金红石含量从0增加至8%(w)时,焊条短路时间概率分布特征值t50从6.56 ms逐渐降低至5.58 ms,电弧稳定性增加、飞溅减小,工艺性能显著改善。随着焊条药皮中金红石含量的增加,熔敷金属化学成分中C、Mn增加,Si降低;熔敷金属抗拉强度与屈服强度呈现增加的趋势,-20℃低温冲击功先增加后降低,在金红石含量为4%时,冲击功平均值达到128 J。     

非金属夹杂物对钢性能的影响

本文分析了钢中非金属夹杂物的形成以及非金属夹杂物的分布状态与材料性能的关系,钢中非金属夹杂物对加工工艺的影响和性能改善的方法,以及在选材时对非金属夹杂物的综合因素分析。     

非金属夹杂物对纯镍N6焊接接头组织性能的影响

以纯镍N6为主要研究对象,借助光学显微镜(OM)、扫描电镜(SEM)、能谱分析仪(EDS)、X射线衍射仪(XRD)及电解萃取装置等手段分析了非金属夹杂物对纯镍N6焊接接头结构及性能的影响.结果表明:纯镍N6试样断裂与非金属夹杂物尺寸、形貌、数量等因素有直接的关系;非正常断裂试样的断口表现为沿晶断裂,断口上夹杂物主要由Al、Si、Ca、Mg、O、Fe等元素组成;对试样的金相组织与夹杂物进行分析发现非正常断裂试样中夹杂物数量及尺寸均大于正常试样,杂物数量大于50个/mm2且夹杂物尺寸大于10 μm的试样均发生断裂;夹杂物主要为氧化铝类(Al2O3、SiO2)、硅酸盐类、氮化物类(AlN、TiN、Ti(C,N))及复相夹杂物;原位拉伸试验表明,断裂的主要原因是在金属基体中存在的夹杂物诱发裂纹源,在应力的作用下裂纹扩展导致断裂.综合分析表明,纯镍N6焊接接头在生产中的断裂是由脆性夹杂物的存在而引起的.     

双丝单弧气保焊熔滴过渡及焊缝成形

双丝单弧气保焊是一种新型熔化极焊接方法,系统由单电源、单送丝机构和单焊枪组成,双丝共用一个具有两孔的导电嘴,单电源通过导电嘴同时向双丝输出电流形成单个电弧,双丝末端熔滴相互吸引形成共熔滴并稳定过渡到熔池。采用高速摄像、信息同步采集及焊接电源等装备,开发双丝单弧气保焊熔滴过渡试验系统,研究了不同焊接电流参数对熔滴大小、过渡行为及焊缝形貌的影响,并阐明了双丝单弧气保焊熔滴过渡机理。结果表明：随着焊接电流的增大,熔滴过渡形式依次为多脉一滴、一脉一滴、射流过渡和潜弧射流过渡四种模式,过渡频率逐渐增大,熔滴体积逐渐减小。焊缝形貌研究表明,随着焊接电流增大,焊缝熔深逐渐增大,熔宽先增大后减小,当焊接电流为570 A时,焊缝截面成形质量最佳,此时熔敷速度为15.8 kg/h。     

双电极奥氏体不锈钢焊条单弧焊工艺研究

本文研究了双电极奥氏体不锈钢焊条单弧焊电弧的静特性、焊接电流、电弧电压、焊芯间隙对双电极焊条单弧焊的工艺性能和焊缝成形的影响;通过热电偶测试技术,对双电极焊条单弧焊焊接过程中不同部位焊芯表面温升进行了测定.研究结果表明焊芯直径为φ4.0mm的双电极A102焊条,其合适焊接工艺参数为:焊接电流140～160A,电弧电压45V左右,焊条两芯间隙1.2～1.5mm,焊接板厚8mm的1Cr18Ni9Ti材料,焊缝成形良好.     

Improvement of pitting corrosion resistance of stainless steel by electric current pulse

ABSTRACT

The electric current pulse (ECP) was applied on the liquidus of 304 stainless steel during solidification and the pitting corrosion of the water-quenched specimens was explored in the present work. The results revealed that the utilisation of ECP can inhibit manganese sulphide from segregating around oxide inclusions during solidification and consequently, the pitting corrosion resistance of ECPed steel was significantly improved. Hence, the application of ECP during solidification might be an efficient way to improve the pitting corrosion resistance of the 304 stainless steel.

This paper is part of a themed issue on Materials in External Fields.     

Effect of water-shower cooling during welding on tensile residual stress improvement in multi-layer welding of austenitic stainless steel plates

Abstract

A new welding method that uses a water shower behind the welding torch has been developed in order to reduce tensile residual stress in a welded region. When this method is applied to the welding of austenitic stainless steel, the welding and cooling conditions mainly determine how much the residual stress can be reduced. To optimize these conditions, we first used the robust design technique to determine the effects of the interpass temperature, the heat input quantity and the water-shower area on the residual stress distribution of bead-on-plate. We found that, to decrease the tensile residual stress, the interpass temperature should be high, the heat input low, and the water-shower area large. Effect of the water-shower cooling on multi-layer welding was examined analytically and experimentally. It was found that the residual stresses were tensile without water-shower cooling, but compressive with water-shower cooling under the optimized conditions. It can therefore be concluded that the new welding method is appropriate for reducing tensile residual stress in multi-layer welding of austenitic stainless steel.     

Effect of welding processes on fatigue crack growth behaviour of AISI 409M ferritic stainless steel joints fabricated using duplex stainless steel fillers

The present investigation aims to study the effect of welding processes such as shielded metal arc welding (SMAW), gas metal arc welding (GMAW) and gas tungsten arc welding (GTAW) on fatigue crack growth behaviour of the ferritic stainless steel (FSS) conforming to AISI 409M grade. Rolled plates of 4 mm thickness were used as the base material and AISI 2209 grade duplex stainless steel (DSS) was used as filler metal, for preparing single pass butt welded joints. Centre cracked tensile (CCT) specimens were used to evaluate the fatigue crack growth behaviour. From this investigation, it is found that the GTAW joints showed superior fatigue crack growth resistance compared with SMAW and GMAW joints. The reasons for the superior performance were discussed in detail.     

Effect of laser welding parameters on fusion zone morphological,mechanical and microstructural characteristics of AISI 304 stainless steel

Nowadays, the Nd:YAG laser has been a promising key tool for joining thin components. In this research, mechanical and microstructural properties of laser welded thin austenitic stainless steel sheets were investigated with experimental investigations, as a function of laser welding parameters. Butt welded joints were made using a Nd:YAG laser in the pulsed wave mode. The appropriate laser welding parameters were found in order to obtain quality and strong weld seam. The pulsed laser seam welding process is controlled by a variety of parameters. We focus on the effects of the several processing parameters on mechanical and microstructural characteristics of joint and weld quality. The aim of this research was to evaluate the influence of these processing parameters on joint strength and microstructure. And also we examined the weldability of stainless steels in butt joint configuration by a pulsed Nd:YAG laser beam.     

不锈钢—碳钢单、双面复合板的爆炸焊接及性能研究

研究了不锈钢－碳钢单面、双面复合板爆炸焊接质量,结合界面的微观结构,剪切强度及耐蚀性能,结果表明,单、双面不锈钢－低碳爆炸焊接复合板的结合界面均为波状结构,结合面两侧存在一定组织变形,近界面处为角结晶组织,稍远处为拉伸变形后的维状组织,结合界面碳钢－侧过渡区存在增碳区,不锈钢一侧有一个脱碳层,双面复合界面的结合过渡区的单面为１．５倍宽,脱碳区也接近单面的１．５倍,采用切割爆炸焊接法有利于改善不锈钢－低碳钢复合板的边缘焊合,在同一基板上进行了双面不锈钢复合时,第一面复合界面的剪切强度比第二面复合界面的差,还是双面复合板,其界面结面强度均由起爆端的末端逐渐降低,结合界面的脱碳层对复合的耐蚀性能无明显影响。     

Determining the critical transition current for metal transfer in gas metal arc welding (GMAW)

It is of great significance to determine the critical transition current from globular transfer to spray transfer in gas metal arc welding (GMAW) because metal transfer modes affect the weld quality and welding productivity. In this study, a simple model is developed to calculate the critical transition current based on the analysis of various forces exerted on a pendent droplet at the electrode tip. It is found that the force exerted by the incoming molten metal from the wire on the drop, i.e., the term ṁ _c v _c, plays an important role in determining the critical transition current. For mild steel wires and argon shielding gas, the critical transition current is predicted with different levels of wire diameter and extensions. The calculated results match the experimental ones.     

Laser power coupling efficiency in conduction and keyhole welding of austenitic stainless steel

Laser welding of thin sheets of AISI 304 stainless steel was carried out with high power CW CO₂ laser. The laser power utilized in the welding process was estimated using the experimental results and the dimensionless parameter model for laser welding; and also the energy balance equation model. Variation of laser welding efficiency with welding speed and mode of welding was studied. Welding efficiency was high for high-speed conduction welding of thin sheets and also in keyhole welding process at high laser powers. Effect of pre-oxidization of the surface and powder as filler material on laser power coupling is also reported. The paper also discusses effect of microstructure on the cracking susceptibility of laser welds.     

Effect of explosive characteristics on the explosive welding of stainless steel to carbon steel in cylindrical configuration

The aim of this research is to study the influence of explosive characteristics on the weld interfaces of stainless steel AISI 304L to low alloy steel 51CrV4 in a cylindrical configuration. The effect of ammonium nitrate-based emulsion, sensitized with different quantities and types of sensitizing agents (hollow glass microballoons or expanded polystyrene spheres) and Ammonium Nitrate Fuel Oil (ANFO) explosives on the interface characteristics is analyzed. Research showed that the type of explosive and the type and proportion of explosive sensitizers affect the main welding parameters, particularly collision point velocity. The morphology of the wavy weld interfaces, chiefly the amplitude and length of the waves, is affected both by the impact velocity and the type and particle size of the explosive sensitizers, and increases with particle size. All the weld interfaces, except welds done with ANFO, displayed localized melted and solidified regions, whose chemical composition resulted from the contribution of both flyer and base metal.