A-TIG焊研究进展及前景展望

对活性化钨极氩弧焊(A-TIG)焊接工艺、活性剂的研发及其在增加焊缝熔深机理等方面的研究做了比较详尽的综述,并指出活性化TIG焊研究过程中存在的问题、发展前景及今后研究方向。认为对活性焊剂增加熔深的机理还有待深入研究,可以利用数值模拟过程结合活性化TIG焊试验深入研究活性焊剂增加焊缝熔深的机理。可以基于A-TIG焊基本思想结合其他方法研发新的活性焊方法。总之,A-TIG焊具有巨大的发展潜力和良好的应用前景。     

2219高强铝合金活性TIG焊工艺

采用单组分活性剂(AlF_3和LiF)、3组分(AlF_3+30%LiF+10%KF-AlF_3)和4组分(AlF_3+30%LiF+10%KFAlF_3+10%K_2SiF_6)混合组分活性剂进行2219高强铝合金直流正极性活性TIG焊(DCSP A-TIG),研究4种类型活性剂对焊缝表面成型、焊缝内部质量(气孔)、焊缝熔深、电弧形态、接头组织与力学性能的影响。结果表明:涂覆活性剂有助于去除2219铝合金表面的氧化膜,提高焊缝表面成型质量,涂覆4组分活性剂的DCSP A-TIG焊缝表面成型质量最佳;与变极性TIG焊(VPTIG)焊缝内部质量相比,DCSP A-TIG焊接方法可显著降低2219铝合金焊缝内部气孔的产生;AlF_3单组分活性剂可显著增大焊缝熔深,其电弧形态具有明显的拖弧现象;DCSP A-TIG焊焊缝组织具有与母材相同的组织组成物,电流对A-TIG焊缝组织影响较大,增大焊接电流,会造成接头晶粒组织粗大;涂覆4组分活性剂的DCSP A-TIG接头强度和伸长率最高,与VPTIG焊接头力学性能具有相近的技术指标。2219高强铝合金的DCSP A-TIG焊接方法具有很大的工程应用价值。     

活性剂在焊接中的应用及展望

综述了活性剂在A-TIG焊、钎焊、电子束焊、FBTIG焊、激光焊、以及CO2气体保护焊中的应用,探讨了活性剂在A-TIG焊、钎焊中的作用和机理,以及国内外活性剂的开发、应用和活化焊接技术的研究及发展中存在的问题和差距.     

The mechanism of penetration increase in A-TIG welding

The mechanism of the increasing of A-TIG welding penetration is studied by using the activating flux we developed for stainless steel. The effect of flux on the flow and temperature fields of weld pool is simulated by the PHOENICS software. It shows that without flux, the fluid flow will be outward along the surface of the weld pool and then down, resulting in a flatter weld pool shape. With the flux, the oxygen, which changes the temperature dependence of surface tension grads from a negative value to a positive value, can cause significant changes on the weld penetration. Fluid flow will be inward along the surface of the weld pool toward the center and then down. This fluid flow pattern efficiently transfers heat to the weld root and produces a relatively deep and narrow weld. This change is the main cause of penetration increase. Moreover, arc construction can cause the weld width to become narrower and the penetration to become deeper, but this is not the main cause of penetration increase. The effects of flux on fluid flow of the weld pool surface and arc profiles were observed in conventional TIG welding and in A-TIG welding by using high-speed video camera. The fluid flow behavior was visualized in real-time scale by micro focused X-ray transmission video observation system. The result indicated that stronger inward fluid flow patterns leading to weld beads with narrower width and deeper penetration could be apparently identified in the case of A-TIG welding. The flux could change the direction of fluid flow in welding pool. It has a good agreement with the simulation results.     

Genetic-Algorithm-Based Computational Models for Optimizing the Process Parameters of A-TIG Welding to Achieve Target Bead Geometry in Type 304 L(N) and 316 L(N) Stainless Steels

The weld-bead geometry in 304LN and 316LN stainless steels produced by A-TIG welding plays an important role in determining the mechanical properties of the weld and its quality. Its shape parameters such as bead width, depth of penetration, and reinforcement height are decided according to the A-TIG welding process parameters such as current, voltage, torch speed, and arc gap. Identification of a suitable combination of A-TIG process parameters to produce the desired weld-bead geometry required many experiments, and the experimental optimization of the A-TIG process was indeed time consuming and costly. Therefore it becomes necessary to develop a methodology for optimizing the A-TIG process parameters to achieve the target weld-bead geometry. In the present work, genetic algorithm (GA)-based computational models have been developed to determine the optimum/near optimum process parameters to achieve the target weld-bead geometry in 304LN and 316LN stainless steel welds produced by A-TIG welding.     

Zone-wise investigation of creep behaviour 9Cr–1Mo steel weld joints

Distinct regions such as weld metal, heat-affected zone (HAZ) and base metal of P9 steel weld joints fabricated by various welding processes were investigated using impression creep testing. Smaller prior austenitic grain size, lower density of precipitates and dislocations resulted in faster recovery and higher creep rate of HAZ in comparison to the weld and base metal. Compared to base metal, shielded metal arc weld (SMAW) and activated tungsten inert gas (A-TIG) weld of the P9 steel weld joints exhibited better resistance to creep and displayed higher activation energy due to their coarser prior austenite grain size. A-TIG HAZ exhibited superior creep properties compared to the SMAW and TIG HAZ due to the presence of higher number density of precipitates.     

活性剂增加不锈钢A-TIG焊熔深机理研究

目的研究涂敷活性剂条件下1Cr18Ni9Ti奥氏体不锈钢的熔深增加机理。方法采用B1活性剂,涂敷在1Cr18Ni9Ti奥氏体不锈钢表面,进行A-TIG焊试验,分析活性剂对电弧形貌、阳极斑点、电弧电压和焊缝熔深的影响情况。结果涂敷活性剂后,电弧和阳极斑点都发生了收缩,电弧宽度由4.97 mm变为4.12mm,减小了17.1%,阳极斑点长轴长度由9.92 mm变为8.22 mm,短轴长度由4.75 mm变为4.35 mm,电弧电压提高了2.7 V,阳极区和弧柱区收缩,提高了弧柱电场强度;相同参数下,涂敷活性剂后熔宽缩小0.62mm,熔深增加了3.01 mm,显著增加熔深。结论阳极斑点收缩和电弧收缩是活性剂增加不锈钢A-TIG焊熔深的主要原因。     

Optimization of Welding Process Parameters for 9Cr-1Mo Steel Using RSM and GA

Optimization of A-TIG welding process parameters for 9Cr-1Mo steel has been carried out using response surface methodology (RSM) and genetic algorithm (GA). RSM has been used to obtain the design matrix for generating data on the influence of process parameters on the response variables. A second-order response surface model was developed for predicting the response for the set of given input variables. Then, numerical and graphical optimization was performed using RSM to obtain the target depth of penetration (DOP) and heat-affected zone (HAZ) width using desirability approach. Multiple regression models were developed based on the generated data, and then the models were used in GA to determine the optimum process parameters for achieving the target DOP and HAZ width. GA-based models employed two different selection processes. Both the RSM- and GA-based models suggested a number of solutions in terms of process parameters, and the identified solutions were validated by experiments. GA-based model employing tournament selection has been found to be a more accurate method for determining the optimum A-TIG welding process parameters.     

奥氏体不锈钢A-TIG焊工艺研究

目的研究焊接参数对焊缝成形和接头宏观组织的影响。方法改变焊接电流、焊接速度、焊接电压以及活性剂中的一个参数,固定其他3个参数不变,对奥氏体不锈钢进行焊接,分析其接头宏观形貌、组织和力学性能。结果随着电流、电压的增加,焊接接头的熔深和熔宽都在增加,随着焊接速度的增加,焊接接头的熔深和熔宽都在降低,在相同参数下,将不同活性剂下的A-TIG焊接头的熔深和熔宽进行比较,发现涂敷C4活性剂接头熔深最大达到4.29mm,而常规TIG焊接头熔深为1.38mm,涂敷C4活性剂的接头熔深为TIG焊的3.11倍,且熔宽也有所减小。结论 C4活性剂A-TIG最佳工艺参数为:I=175 A,U=14 V,v=80 mm/min,此时能将6 mm板材焊透,成形良好,在此工艺下焊缝等轴晶范围最大,焊缝组织最为细小。相比于TIG焊,涂敷C4活性剂接头强度系数提升4.1%。     

活性剂对铁素体不锈钢A-TIG接头熔深及组织性能研究

目的 选用430铁素体不锈钢作为研究对象,对比研究添加SiO2、TiO2、Cr2O3和未添加活性剂对A-TIG焊接接头显微组织和力学性能的影响。方法 采用3种活性剂涂覆在430铁素体不锈钢上进行A-TIG试验,分析活性剂对接头熔深、组织、性能、元素含量的影响情况。结果 同一焊接工艺参数下,活性剂的加入均能提高焊缝的熔深和深宽比,减少熔宽;其中,SiO2为活性剂时获得了最佳的焊缝几何形貌。同时,对比常规TIG焊接(未添加活性剂)接头的显微组织及力学性能可知,活性剂的加入并未改变焊接接头的显微组织且无新相的生成;活性剂的添加能够细化接头组织,从而使得接头硬度有所提高。结论 活性剂的加入能够显著增加铁素体不锈钢TIG焊缝熔深,改善接头组织,提高接头硬度。     

粉煤灰复合活性剂在A-TIG焊中增加熔深的机理研究

为实现对工业废弃物粉煤灰的剩余价值利用,尝试以粉煤灰作为主要原料制备焊接复合活性剂,并在AZ91镁合金板上进行A-TIG焊.利用焊缝的电特性实时采集、焊接温度场采集、电弧力测试等手段研究活性剂对电弧影响,通过熔池Bi粒子示踪实验探究活性剂对表面张力温度梯度影响.结果 表明:与常规TIG焊相比,粉煤灰复合活性剂可以使焊缝熔深增深1.4倍,熔宽减小,深宽比是常规TIG焊的1.43倍.粉煤灰复合活性剂中氟化物的解离和电离吸热过程、带电粒子的电子扩散和复合过程可以促进电弧收缩,使焊接电压升高,热输入量提高.而活性剂中的氧化物既可以通过对电弧的机械压缩作用强迫电弧收缩,又可以通过电离产生的氧元素实现对熔池液态金属表面张力温度梯度系数的改变,提高熔池中心热输入.A-TIG焊AZ91镁合金熔深增加是电弧收缩理论和表面张力温度梯度改变理论共同作用的结果.     

Optimization of A-TIG process parameters using response surface methodology

In the present work, the influence of process parameters such as welding current (I), welding speed (S), and flux coating density (F) on different aspects of weld bead geometry for example depth of penetration (DOP), bead width (BW), depth to width ratio (D/W), and weld fusion zone area (WA) were investigated by using the central composite design (CCD). 9–12% Cr ferritic stainless steel (FSS) plates were welded using A-TIG welding. It was observed that all input variables have a direct influence on the DOP, BW, and D/W. However, flux coating density has no significant effect on WA. Mathematical models were generated from the obtained responses to predict the weld bead geometry. An optimized DOP, BW, D/W, and WA of 6.95?mm, 8.76?mm, 0.80, and 41.99?mm², respectively, were predicted at the welding current of 213.78 A, the welding speed of 96.22?mm/min, and the flux coating density of 1.99?mg/cm². Conformity test was done to check the practicability of the developed models. The conformity test results were in good agreement with the predicted values. Arc constriction and reversal in Marangoni convection were considered as major mechanisms for the deep and narrow weld bead during A-TIG welding.     

粉煤灰/二氧化硅活性剂在Q235钢A-TIG焊中的应用

为了探究粉煤灰作为A-TIG焊活性剂的可行性,以粉煤灰和不同含量的二氧化硅制备复合活性剂在Q235钢基体表面进行A-TIG焊,研究了复合活性剂成分含量对焊缝截面形貌、显微组织和元素分布的影响.结果表明:采用粉煤灰-40%SiO_2作为复合活性剂进行A-TIG焊时,可将6 mm厚Q235钢板一次性焊透,焊缝深宽比可达到0.85;焊缝出现明显的中间收缩倾向,呈"深口杯"状,可实现单道焊双面成型的效果;其焊缝柱状晶数目较多、组织排列规则且具有方向性,熔合区和热影响区组织均匀细小,可降低焊接母材的过热倾向;相对于100%SiO_2活性剂,Si元素的溶入量和溶入深度显著增加,这说明粉煤灰中其他成分的存在对Si元素溶入焊缝、进而增加焊缝熔深起到促进作用.采用粉煤灰-40%SiO_2为活性剂进行A-TIG焊时焊缝熔深的增加机理可能是以电弧收缩理论为主,但考虑到Al元素溶入较深且溶入量较多,粉煤灰中其他物相又十分复杂,在高温电弧作用下各物相之间相互反应放热致使电弧热输入增加、其他组分在熔池中改变了熔池表面张力温度梯度等均可能致使焊缝熔深增加.     

Characterisation of dissimilar P91 and P92 steel welds joint

In the present study, dissimilar weld joint was prepared using the P91 and P92 steel plate of 8-mm thickness, using the multi-pass gas tungsten arc (GTA) welding with filler (weld 1) and autogenous tungsten inert gas welding (A-TIG) process (weld 2). Evolution of δ-ferrite patches was studied in weld zone and heat affected zone (HAZ) for both weld 1 and weld 2. Effect of varying post weld heat treatment (PWHT) duration was also studied on δ-ferrite patches and mechanical properties of the dissimilar weld joint. PWHT was carried out at 760°C. For weld 2, weld zone showed poor impact toughness and higher peak hardness as compared to weld 1. After the PWHT, a considerable reduction in hardness was obtained for both weld 1 and weld 2,while impact toughness of weld zone showed a continuous increment with PWHT duration. For weldments characterisation, optical microscope, scanning electron microscope (SEM) and microhardness tester were utilised.     

活性剂对CO_2气体保护焊焊缝成形及飞溅的影响

使用自制的活性焊丝,研究了活性剂对CO2气体保护焊焊缝成形及飞溅的影响。结果表明,使用活性剂可以使焊接飞溅率大大降低,焊缝熔深增加,熔宽增大,焊缝表面成形光滑。认为CO2气体保护焊飞溅降低的原因,是因为活性剂的加入在降低了混合气体的有效电离电压的同时显著增加了CO2电弧的导电能力,使电弧能量密度增加,从而使中等电流下的熔滴过渡方式由大颗粒过渡转变成细颗粒过渡。     

炼油厂石油焦活性炭的制备

用炼油厂石油焦为原料,以ＫＯＨ为活性剂进行活化制备活性炭,考察了活化温度、活化时间以及活化剂用量对ＢＥＴ比表面积和亚甲基蓝吸附的影响,优化出最佳工艺过程：活化温度为８００ ℃,活化时间为１ ｈ,活化剂与石油的用量比为５：１。用双柱定容容量法测定了实验制备活性炭对甲烷的吸附量,与常用活性炭比较,是其吸附量的５ 倍左右。     

污水厂脱水污泥制吸附剂及脱除H2S效能研究

采用热解炭化法制备了一系列污泥吸附剂,优化制备工艺,利用扫描电镜(SEM)、比表面积和孔径分析等技术对污泥吸附剂的结构进行了表征,并研究了脱除H2S效能。结果表明,活化温度、活化时间和固液比等因素均对污泥吸附剂的碘吸附值产生影响。当活化温度为550℃、活化时间为2.0h、固液比为1∶2时所制备材料(SA)的碘吸附值最高,为493.12mg/g;制备的SA具有较好的脱除H2S效能,能满足精脱硫的要求,当空速为4600h-1时,SA的除臭时间可达48min;此外SA中含有的多种金属元素,平均孔径为3.4nm,这些性质均有利于H2S的吸附脱除。     

Preparation of activated carbons from coffee husks utilizing FeCl3 and ZnCl2 as activating agents

Ferric chloride was used as a new activating agent, to obtain activated carbons (AC) from agro industrial waste (coffee husks). This material was compared with two samples from the same raw material: one of them activated by using the classical activating agent, zinc chloride, and the other, activated with a mixture of the two mentioned activating agents in the same mass proportion. The carbonaceous materials obtained after the activation process showed high specific surface areas (BET), with values higher than 900 m(2)g(-1). It is interesting to observe that the activation with FeCl(3) produces smaller pores compared to the activation with ZnCl(2). An important fact to emphasize in the use of FeCl(3) as activating agent is the activation temperature at 280 degrees C, which is clearly below to the temperature commonly employed for chemical or physical activation, as described in the bibliography. All the studied materials showed different behaviors in the adsorption of methylene blue dye and phenol from aqueous solutions.     

蒙乃尔合金活性化TIG焊工艺

介绍了采用活性化焊剂TIG焊(A-TIG)对蒙乃尔合金400进行焊接的工艺评定情况。在A-TIG焊条件下,该工艺可以单面完成6mm及双面完成10mm直边对接板的焊接;对焊接头进行的金相组织和力学性能试验表明,使用A-TIG焊不仅能够大幅度增加焊接熔深,还能获得优良的力学性能;同时可节省昂贵的焊材。A-TIG焊焊接蒙乃尔合金是一种值得推广的焊接新工艺。     

Therapeutic nanoreactors: combining chemistry and biology in a novel triblock copolymer drug delivery system

Triblock copolymeric nanoreactors are introduced as an alternative for liposomes as encapsulating carrier for prodrug activating enzymes. Inosine-adenosine-guanosine preferring nucleoside hydrolase of Trypanosoma vivax, a potential prodrug activating enzyme, was encapsulated in nanometer-sized vesicles constructed of poly(2-methyloxazoline)-block-poly(dimethylsiloxane)-block-(2-methyloxazoline) triblock copolymers. The nanoreactor is functionalized by incorporation of bacterial porins, OmpF or Tsx, in the reactor wall. Efficient cleavage of three natural substrates and one prodrug, 2-fluoroadenosine, by the nanoreactors was demonstrated.