Arc Behavior and Droplet Transfer of CWW CO2 Welding

Cable-type welding wire (CWW)CO2 welding is an innovative process arc welding with high quality,high efficiency and energy saving,in which CWW is used as consumable electrode.The CWW is composed of seven wires with a diameter of 1.2 mm.One is in the center,while others uniformly distribute around it.The diameter of twisted wire is up to 3.6 mm,which can increase the deposition rate significantly.With continual wire-feeding and melting of CWW,the formed rotating arc improved welding quality obviously.The arc behavior and droplet transfer were ob-served by the electrical signal waveforms and corresponding synchronous images,based on the high speed digital camera and electrical signal system.The results showed that the shape of welding arc changed from bell arc to beam arc with the increase of welding parameter.The droplet transfer mode changed from repelled transfer,globular transfer to projected transfer in turn.Droplet transfer frequency increased from 18.17 Hz to 119.05 Hz,while the droplet diameter decreased from 1.5 times to 0.3 times of the CWW diameter.     

CO2气体保护焊中的未熔合缺陷分析

未熔合现象是CO2气体保护焊中最常见、危害性大且不易被发现的缺陷,约占缺陷总数的60％。分析认为,未熔合产生的主要原因是焊接电流大、焊接速度慢及操作不当等。施焊时应采用正确的焊接参数,合适的焊接角度,同时保证焊丝的摆动幅度,依据母材厚度确定焊接层数,尽量做到多层多焊道,防止未熔合现象的产生。     

大口径油气管道环焊技术的进展及在宝钢的应用

介绍了当前管道工业的发展及管道焊接技术的进展情况,并阐明了管道全位置下向焊接技术的特性.管道环焊缝是由根焊、热焊、填充焊、盖面焊等不同焊道组成.对常用的手工焊、半自动焊和自动焊接方法在管道环焊缝不同焊道焊接时的应用以及各自特点做了介绍,还对焊接材料的选用、焊接设备的选型作了描述.宝钢铜管厂大口径直缝埋弧焊管(UOE)项目即将投产,投产后大口径焊管产品使用技术的研究势在必行,宝钢应尽快开展大口径UOE焊管的环缝焊接技术的研究,为将来的推广应用提供必要的技术支撑.     

回转窑安装焊接方案

文章论述了目前国内先进的回转窑安装技术,采用激光经纬仪等科学的组对找正对准方法,简单易行,精确度高.对回转窑筒体等厚和异厚板采用细滴过渡CO2气体半自动保护焊焊接工艺技术,高效优质,合理可靠.     

耐火耐候钢焊接性能及焊接材料的研究

重点介绍了武钢技术中心高层办公大楼用WGJ510C2耐火耐候钢(14 mm 、25 mm)2种规格钢板与WQ-1埋弧焊丝匹配试验研究.按照工程提出的焊接技术条件,对武钢二热轧生产的WGJ510C2钢进行了埋弧焊对接性能试验,内容包括接头常规力学性能试验、高温拉伸性能试验、金相组织与硬度试验、电化学腐蚀性能试验.试验结果表明,采用WQ-1焊丝加CHF101焊剂匹配焊接WGJ510C2钢2种规格试板,接头常温拉伸强度和高温拉伸强度均满足WGJ510C2钢技术条件要求.焊缝、熔合线和热影响区低温冲击功大于140 J,接头各区电化学腐蚀电位相近,具有优良耐腐蚀性能,焊接接头综合性能指标完全满足高层建筑用钢焊接技术要求.     

Effect of submerged arc welding parameters on microstructure of SA516 steel weld metal

Abstract

The influence of submerged arc welding (SAW) process parameters on the microstructure of SA516 grade 70 steel weld metal (WM) was investigated in the present work. Steel plates of 17 mm thickness were submerged arc welded using welding currents of 700–850 A and welding speeds of 5·3–15·3 mm s^?1. The morphologies and volume fractions of the various ferrites in the WM were studied using optical microscopy and the morphologies and chemical compositions of the WM inclusions were examined using scanning electron microscopy and energy dispersive X-ray spectrometry. The results showed that the WM grain structure coarsened but the grain width of prior austenite grains decreased with increasing heat input. Also, the proportion of acicular ferrite (AF) in the WM increased initially, while the volume fractions of grain boundary ferrite and Widmanstätten ferrite decreased with increasing welding current. However, with further increasing the welding current above 800 A, less AF was produced. The weld nugget area decreased with increasing welding speed at all currents, but did not affect the amount of AF produced.

Au cours de ce travail, on a examiné l’influence des paramètres du procédé de soudage à l’arc sous flux en poudre (SAW) sur la microstructure du métal soudé (WM) de l’acier SA516, Gr. 70. On a soudé à l’arc sous flux en poudre des tôles d’acier de 17 mm d’épaisseur en utilisant des courants de soudage de 700 à 850 A et des vitesses de soudage de 5·3 à 15·3 mm s^?1. On a étudié la morphologie ainsi que la fraction volumique des diverses ferrites du WM en utilisant la microscopie optique et l’on a examiné la morphologie ainsi que la composition chimique des inclusions du WM en utilisant la microscopie électronique à balayage (SEM) et la spectroscopie à dispersion d’énergie (EDS). Les résultats ont montré que la structure de grain du WM grossissait mais que la largeur de grain des grains antérieurs d’austénite diminuait avec une augmentation de l’apport de chaleur. Également, la proportion de ferrite aciculaire (AF) dans le WM augmentait initialement, alors que les fractions volumiques de ferrite des joints de grain (GBF) et de ferrite de Widmanstatten (WF) diminuaient avec l’augmentation du courant de soudage. Cependant, avec une augmentation supplémentaire du courant de soudage au-dessus de 800 A, moins de ferrite aciculaire était produite. La région du noyau de soudure diminuait avec une augmentation de la vitesse de soudage à toutes les valeurs de courant, mais la quantité d’AF produite n’était pas affectée.     

A Feasibility Study on Manufacturing of Functionally Graded Structures Using SiC Ceramic Powder in a Steel‐Based Matrix by Gas Tungsten Arc Welding (GTAW)

The paper presents a feasibility study on application of the gas tungsten arc welding (GTAW) process to obtain metal composite functional coating for advanced tribological application. Silicon carbide (SiC) particles in the form of powder was added to a weld pool in autogenous mode as well as with an additional filler wire. Powder feeding was carried out at different angles and with varying separation distance from the welding torch. The metallurgical characterization of the cladded structure was carried out using optical as well as scanning electron microscopy (SEM). Energy dispersive X‐ray spectroscopy (EDS) was performed to analyze the composition of the deposited weld metal. It has been observed that due to low SiC density it was difficult for particles to penetrate the weld pool. Also the added SiC was found to be dissociated into Si and carbon (C) and the large amount of dissolved C in the weld pool resulted in formation of graphite phases.     

Thermodynamic Analysis and Experimental Study on Reaction of CO2 Gas with Hot Metal

The reaction of CO_2 gas with hot metal was investigated based on the thermodynamic analysis and experimental results.It shows that both silicon and carbon in hot metal can be oxidized by CO_2 gas in the temperature range of 1 300-1 500 ℃.When using graphite crucible,temperature has little influence on final mass percent of carbon w[C]because of the carburization effect.Decarburization degree rises significantly with increasing gas injection rate and w[C]can be reduced to 3.2% at most when using MgO crucible.Lower temperature or higher gas injection rate is propitious to promote desilication reaction,but only 5%-10% of desilication ratio could be obtained in 20 min.The final mass percent of silicon w[Si]when using MgO crucible is lower than that when using graphite crucible.Experimental results also demonstrate that CO_2 injection has no effect on the concentration of manganese,sulfur and phosphorus in hot metal.In view of the weak oxidation ability and temperature drop of hot metal,CO_2 gas is suggested to be used as carrier gas in desilication process rather than oxidizing agent.     

不同等离子气比例对PS-PVD射流及涂层结构影响研究

等离子物理气相沉积（PS-PVD）一般采用高氦气流量和高喷枪输入功率的工艺,获得具备优异性能的柱状/准柱状结构热障涂层。研究了低氦气流量和低喷枪输入功率条件下,沉积位置对应等离子射流中心的能量变化规律,及对涂层微结构的影响。结果表明：采用适配工艺优化的氧化锆粉体材料,90 L/min等离子气总流量条件下,Ar/He体积比从1︰2调整至2︰1,氦气流量降低,均能获得准柱状结构涂层。Ar/He体积比1︰1条件下射流能量最高,此时He对等离子射流收束作用减弱,制备涂层的柱状晶厚度降低、柱状晶间冷凝颗粒增多,涂层沉积效率明显降低;总气流量120 L/min,Ar/He体积比2︰1,可获得液相沉积为主的致密涂层结构。结合各元素特征峰的光谱分析结果,Zr Ⅰ特征峰强度在Ar/He体积比1︰1条件下最高,之后随着Ar/He体积比降低,He对等离子射流气相的约束及对等离子射流的能量场的综合影响决定了涂层微结构特性。