Influence of arc pressure on the forming of molten pool in tungsten inert gas arc butt welding with micro gap for tantalum sheet

Arc pressure is the key influencing factor to forming of molten pool. Countering the characteristic of tungsten inert gas arc welding with micro gap for tantalum sheet, according to the fundament of arc physics, a distribution model of arc pressure and forming mechanism of molten pool with micro butt gap are proposed, and the influences of arc pressure on forming of molten pool are discussed. Experimental researches for the dynamic formation process of weld molten pool by using high-speed vidicon camera show that when butt gap is appropriate, that is from 0. 1 to 0. 15 mm, molten metals formed on two workpiece uplift and grow up first, then are fused and form uniform molten pool finally.

基于电弧光谱的核电堵管TIG焊接质量在线监测

为了实现受操作空间限制和辐射环境下,高温气冷堆蒸汽发生器传热管道堵管钨极惰性气体保护电弧焊(tungsten inert gas welding, TIG)的质量监测,搭建了一套基于光纤光谱仪的TIG焊接过程实时监测系统,用于核电传热管道堵管TIG焊接熔深监测.试验研究采用该系统采集电弧光谱,利用主成分分析法获取不同焊缝熔深的光谱主成分特征,创新性提出了一种ATT-L2R-BiLSTM深度学习模型,实现了堵管TIG焊接过程中焊缝熔深的分类识别.结果表明,实验室条件下模型准确率可达92.61%,比Bi-LSTM网络准确率提高5.11%,该模型在核电蒸汽发生器堵管验证平台进行了测试和验证,准确率达到99.26%,最终,实现了光谱信息不完备下TIG焊接质量特征深度挖掘,以及TIG焊接熔深的精准评估.

Analysis of Arc Physical Property of Pulsed Tungsten Inert Gas Welding Based on Fowler-Milne Method

Pulsed tungsten inert gas （TIG） welding is widely used in industry due to its superior properties, so the measurement of arc telnperature is important to analyse welding process. Arc image of spectral line in 794.8 nm is captured by high speed camera; both the Abel inversion and the Fowler-Milne method are used to calculate the temperature distribution of the pulsed TIG welding. Characteristic of transient variation in arc intensity and temperature is analyzed. When the change of current happens, intensity and temperature of arc jump as well, it costs several millisoconds. The flirther the axial position from the tungsten is, the greater the intensity jumps, and the smaller the temperature changes.

数值模拟在不锈钢焊接中的应用

针对不锈钢包壳及端塞钨极氩弧焊(TIG)焊接过程,采用ABAQUS有限元软件及其Dflux子程序,对焊接温度场、应力场进行耦合数值模拟分析,建立了非稳态TIG焊接熔池形态的数值分析模型,计算了焊接电流、焊接速度、弧形、焊接频率对焊接温度场、应力场的影响,并通过模拟的手段,对缺陷机理进行了研究。同时借助少量工艺试验的手段,确定了脉冲频率1800 Hz,轴向装配间隙小于0.05 mm的焊接工艺,大大节约了不锈钢原材料的使用量,为后续焊接工作提供了理论指导。

Prevention of carbon migration in 9% Cr/CrMoV dissimilar welded joint by adding tungsten inert gas overlaying layer

High chromium （9-12% Cr） steels with excellent heat resistance and CrMoV steels with good toughness were potential candidates for combined rotor for steam turbine operated over 620℃. Two welding techniques were used to fabricate 9% Cr and CrMoV dissimilar welded joint. The results show that the carbon migration only appears in the specimen using narrow gap submerged arc welding （NG-SAW） technique, yet it can be effectively prevented by adding tungsten inert gas （TlG） overlaying process before the NG-SAW. The carbon migration occurred in NG-SAW resulting from the sharp transition of the strong carbide-forming element Cr between the weld （-2.7 wt%） and the base metal （- 9 wt%）. On the contrary, the application of TIG overlaying layers can promote the diffusion of Cr element, and therefore result in its much smaller concentration gradient. That is to say, a gentle transition zone of Cr element can be created among the SAW weld, TIG overlaying layers and the base metal, which effectively prevents the carbon migration and therefore produces a decreased carbon concentration adjacent to the fusion line.

Fracture behavior of double-pass TIG welded 2219-T8 aluminum alloy joints under transverse tensile test

2219-T8 aluminum alloys were butt welded by the double-pass tungsten inert gas （TIG） arc welding process. The transverse tensile test of the joint showed that the fracture mainly occurred in the partially melted zone （PMZ）. Effects of the PMZ on the fracture behavior were systematically studied. Continuous intergranular eutectics were observed in the PMZ close to the fusion line. Away from the fusion line, the intergranular eutectics in the PMZ became discontinuous. The fracture morphology and the microhardness distribution of the joint showed that the PMZ was gradient material with different mechanical properties, which strongly affected the fracture process. It was observed that the crack initiated in the PMZ near the front weld toe, and propagated in the PMZ away from the fusion line. Then, the crack tip was blunt when it propagated into the PMZ with higher plasticity. Finally, the rest part of the joint was shear fractured.

SiC_P/Al复合材料脉冲氩弧焊接研究

研究在脉冲氩弧焊条件下铝基复合材料 Si CP/2 12 4 Al的可焊性。通过正确选择填充材料和在焊接过程中加入微量脉冲 ,大大减弱了增强体 Si C颗粒与基体 Al之间的界面反应。拉伸实验和显微硬度测试表明 ,接头质量良好 ,与母材强度相比 ,接头的抗拉强度未见有大幅度下降 ;金相组织观察显示 ,焊缝组织致密、无夹杂和裂纹等缺陷。对接头进行 X射线衍射相结构分析和拉伸断口扫描电镜观察等微观分析 ,并从热力学角度探讨焊接过程中抑制 Si C/Al界面反应发生的机理 ,提出了在氩弧焊条件下获得高质量 Si

B304N奥氏体不锈钢焊条电弧焊与钨极氩弧焊焊接接头的冲击性能比较

分别采用焊条电弧焊工艺和钨极氩弧焊工艺焊接B304N奥氏体不锈钢,并对焊接接头冲击性能进行测试,分析对比两者焊接接头焊缝、熔合线、热影响区的冲击性能。结果表明,钨极氩弧焊焊缝的冲击性能比焊条电弧焊焊缝的冲击性能要高一倍以上,其熔合线的冲击性能也好于焊条电弧焊,热影响区冲击性能接近。

TIG 焊自动接触引弧技术研究

本文提出了一种ＴＩＧ（ＴｕｎｇｓｔｅｎＩｎｅｒｔＧａｓ）焊自动接触引弧方法，介绍了该方法的原理。试验证明该技术引弧可靠性高，钨极损耗量少，为接触引弧技术开创了一条新途径。

Al-Si-Cu系铸造铝合金钨极氩弧焊

用金相、扫描电镜、电子探针和X射线衍射等检验方法,从焊接工艺和焊接接头区域组织结构两方面进行分析。结果表明,采用交流钨极氩弧焊和Al-Si合金焊丝(MS311)作填充金属,可获得满意的结果。该工艺可推广应用于各种铸造铝合金构件的焊接与焊补。

自动钨极氩弧焊在大型阀件上的应用

叙述了奥氏体不锈钢的焊接性,通过几种焊接工艺方法的对比试验,选择自动钨极氩弧焊焊接大型阀件,经过焊接工艺评定,焊制出优质的Ⅰ级焊缝。

新型晶闸管直流TIG焊机研制

研制了一种１５０Ａ直流ＴＩＧ焊机，采用特殊的晶闸管主电路和集成电路控制技术，具有简单、可靠和高性能的特点。

异种金属材料焊接性的研究——HSn62-1与1Cr18Ni9Ti焊接铜渗透裂纹

本文是在冷却器HSn62—1黄铜与1Cr18Ni9Ti奥氏体不锈钢熔—钎焊(Welding—braze)工艺试验的基础上,采用铜合金焊丝对奥氏体不锈钢的焊接中产生铜渗透裂纹进行了机理的研究。通过熔一钎焊的TIG工艺大量试验数据表明,液态铜对奥氏体不锈钢润湿、渗透,在焊接应力作用下,沿晶界渗透扩展而开裂,并且在裂纹中充满了液态铜。由于液态铜使晶界表面能明显降低,同时对裂纹尖端壁面产生一种附加压力,促使液态铜沿晶界加速扩展,形成奥氏体不锈钢液态金属脆化而导致铜的渗透裂纹。 本试验采用七种钢合金焊丝进行熔一钎焊的TIG最佳工艺试验,提出了适用的焊丝,指明了产生铜渗透裂纹的基本规律,为完善异种金属焊接提供了理论依据。

焊接工艺对不锈钢角焊缝连接试件力学性能影响研究

对12个奥氏体型及12个双相型不锈钢正面角焊缝和侧面角焊缝连接试件进行了单调拉伸试验,考察了不同焊接工艺对角焊缝连接力学性能的影响。结果表明:采用氩弧焊焊接工艺的不锈钢角焊缝试件破坏面与电弧焊焊接工艺的试件破坏面形状相差较大,后者破坏面更加光滑;同时由于受到复杂应力的作用,正面角焊缝试件的真实破坏角度并不为相关规范规定的理论值45°;对于奥氏体型不锈钢角焊缝,氩弧焊试件与电弧焊试件的强度比分别为1.03(正面角焊缝试件)及1.13(侧面角焊缝试件),相对变形量之比为1.46及1.11;而对于双相型不锈钢角焊缝,两者的强度比分别为1.12和1.04,相对变形量之比为1.66及1.45;氩弧焊试件表现出了更好的力学性能。对于两种不锈钢材料,正面角焊缝强度均远大于侧面角焊缝的强度,建议在工程设计和相关规范的编制/修订中考虑正面角焊缝强度提高的影响。

Welding of nickel free high nitrogen stainless steel: Microstructure and mechanical properties

High nitrogen stainless steel(HNS) is a nickel free austenitic stainless steel that is used as a structural component in defence applications for manufacturing battle tanks as a replacement of the existing armour grade steel owing to its low cost, excellent mechanical properties and better corrosion resistance.Conventional fusion welding causes problems like nitrogen desorption, solidification cracking in weld zone, liquation cracking in heat affected zone, nitrogen induced porosity and poor mechanical properties.The above problems can be overcome by proper selection and procedure of joining process. In the present work, an attempt has been made to correlate the microstructural changes with mechanical properties of fusion and solid state welds of high nitrogen steel. Shielded metal arc welding(SMAW), gas tungsten arc welding(GTAW), electron beam welding(EBW) and friction stir welding(FSW) processes were used in the present work. Optical microscopy, scanning electron microscopy and electron backscatter diffraction were used to characterize microstructural changes. Hardness, tensile and bend tests were performed to evaluate the mechanical properties of welds. The results of the present investigation established that fully austenitic dendritic structure was found in welds of SMAW. Reverted austenite pools in the martensite matrix in weld zone and unmixed zones near the fusion boundary were observed in GTA welds. Discontinuous ferrite network in austenite matrix was observed in electron beam welds.Fine recrystallized austenite grain structure was observed in the nugget zone of friction stir welds.Improved mechanical properties are obtained in friction stir welds when compared to fusion welds. This is attributed to the refined microstructure consisting of equiaxed and homogenous austenite grains.

Microstructure and mechanical properties of TIG/A-TIG welded AZ61/ZK60 magnesium alloy joints

The dissimilar joints of AZ61 and ZK60 magnesium alloys were obtained by tungsten inert gas arc(TIG)welding and activating tungsten inert gas arc(A-TIG)welding processes.Microstructure characterization shows that,the fineα-Mg equiaxed dendrite crystals contained Mg17Al12 and MgZn2 particles in the fusion zone.The average size of theα-Mg grains in the fusion zone was refined to 19μm at welding current of 80 A,which resulted in the largest tensile strength of 207 MPa.The tensile strength and the width of the beam of the A-TIG welded AZ61/ZK60 joints showed strong dependence on the amount of TiO2.However,the inhomogeneity of the heat-affected zone near different base metals presented no significant effect on the mechanical properties of the welded joint.

Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy TIG-welded joint

Microstructural evolution and its effect on mechanical properties in different regions of 2219-C10S aluminum alloy tungsten inert gas(TIG)welded joint were analyzed in detail.In weld zone(WZ),α+θeutectic structure formed at grain boundaries with no precipitates inside the grains.In partially melted zone(PMZ),symbiotic eutectic or divorced eutectic formed at grain boundaries and needle-likeθ′phases appeared in the secondary heated zone.In over aged zone(OAZ),the coarsening and dissolution ofθ′phases occurred and mostθ′phases transformed intoθphases.In general heat affected zone(HAZ),θ′phases coarsened.Factors such as the strengthening phases,the grain size,the Cu content in matrix and the dislocation density can affect the mechanical properties in different regions of the joint.Moreover,a model describing the relationship between mechanical properties of the material and the volume fraction of precipitates,the average diameter of precipitates and the concentration of soluble elements was proposed.

薄壁发动机壳体加工及热处理中的新工艺

以固体火箭发动机燃烧室壳体为例，介绍一种以提高加工精度、材料的强度和韧性为目标，在加工、焊接、热处理中的几种新工艺。并论述了该工艺的原理及使用原则。实践证明，这种新工艺是行之有效的。

Effects of graphene nanoplates on microstructures and mechanical properties of NSA-TIG welded AZ31 magnesium alloy joints

The effects of graphene nanoplates(GNPs)on the microstructures and mechanical properties of nanoparticlesstrengthening activating tungsten inert gas arc welding(NSA-TIG)welded AZ31magnesium alloy joints were investigated.It wasfound that compared with those of activating TIG(A-TIG),and obvious refinement ofα-Mg grains was achieved and the finestα-Mggrains of fusion zone of NSA-TIG joints were obtained in the welded joints with TiO2+GNPs flux coating.In addition,thepenetrations of joints coated by TiO2+GNPs flux were similar to those coated by the TiO2+SiCp flux.However,the welded jointswith TiO2+GNPs flux coating showed better mechanical properties(i.e.,ultimate tensile strength and microhardness)than those withTiO2+SiCp flux coating.Moreover,the generation of necking only occurred in the welded joints with TiO2+GNPs flux.

Diagnosis of TIG welding based on ultraviolet radiation

Through collecting the radiation of tungsten inert gas （TIG） welding arc, the radiation distribution in ultraviolet zone is analyzed in order to study the variation rule of ultraviolet radiation versus welding condition. The explanation for the variation is also provided based on spectral radiation theory of arc light. Furthermore, through analysis of disturbance factors, the integral intensity signal of radiation in ultraviolet zone is applied for diagnosis of welding process. The spectral signal of ultraviolet radiation can reflect the disturbance factors and welding conditions, which can be used for online diagnosis of welding process.