Effect of activating fluxes on weld mechanical properties in TIG welding

Activating TIG (A-TIG) welding has received many attentions worldwide since the end of 1990s. Compared with conventional TIG welding A-TIG welding can greatly improve the welding productivity and reduce the welding cost without altering the equipments under the same welding procedures and is considered as a innovative variant of conventional TIG welding. The materials applied by A-TIG welding have ranged from original titanium alloy to stainless steel, carbon steel, high temperature alloy steel and so forth. The effects of activating fluxes with single component on weld mechanical properties such as tensile strength, hardness and elastics during A-TIG welding of stainless steel are discussed in this paper. The experimental results show that different fluxes have different effects on the weld mechanical properties. Among these fluxes the flux SiO_2 is the best in the performance of tensile strength and ductility, while flux Cr_2O_3 is the best in the performance of weld hardness compared with conventional TIG welding. These experiments provide the foundation for selecting the most suitable fluxes for stainless steel in practical welding production.

Microstructure, Mechanical Property and Corrosion Resistance Property of Cr26Mo3.5 Super Ferritic Stainless Joints by P-TIG and Laser Welding

The characteristics of microstructure, mechanical property and corrosion behavior of Cr26Mo3.5 super stainless steel joints by pulse tungsten inert gas(P-TIG)welding and laser welding were investigated. The results indicate that the widths of the center equiaxed grain zone(EGZ)and the columnar grain zone(CGZ)increase with the increase of heat input in both welding processes. The precipitates of Nb and Ti carbides and nitrides are formed in the weld metal(WM)and the heat affected zone(HAZ). The joints by laser welding show better tensile and corrosion resistance properties than those by P-TIG welding due to the heat concentration and lower heat input. The tensile strength and elongation increase with the decrease of heat input, and the fracture mode of the joints turns into ductile-brittle mixed fracture from ductile fracture when the welding method turns into P-TIG welding from laser welding. Moreover, the corrosion resistance of all joints declines slightly with the increase of heat input. Hence, laser welding is more suitable for welding Cr26Mo3.5 super stainless steel in engineering applications.

Influence of filler materials on microstructure and mechanical properties of MGH956 alloy in TIG welding

In order to improve the mechanical properties of MGH956 alloy fusion weZding joint, two kinds of self-made materials were used as filler materials to MGH956 alloy for TIG welding respectively. Microstracture and tensile fracture of joints were researched by scanning electron microscope（SEM）. Reinforced particles were researched by SEM, X-ray diffraction （ XRD ） and energy dispersive X-ray spectrometry （EDS）. These results were compared with joint which is filled with base materials. The results show that new reinforced phases such as TiC, TiN, Ni3Al and A1Ni are produced in the weld metal zone with two kinds of self-made materials as filler materials. The size of these reinforcements is about 1 μm, and the distribution of particles is very uniform in the matrix. The number of pores is reduced. Agglomerate Al-Y-O composite oxides are correspondingly decreased compared to the joint filled with base material. Thus, welded joint perormanee is enhanced. The average room temperature tensile strength of joints are 581 MPa and 607 MPa respectively. The fracture of joints both in general exhibit brittle fracture.

Research on the Mechanism of Penetration Increase by Flux in A-TIG Welding

The mechanism of penetration depth increased by activating flux in activating tungsten inert gas (A-TIG) weldingwas studied by measuring the distribution of trace element Bi in the weld and monitoring the change of arc voltageduring A-TIG welding of stainless steel 0Crl8Ni9 with fluxes SiO2 and TiO2. The results show that the mechanismof penetration depth in A-TIG welding depends on the sort of flux used. The weld pool convection after coating theflux SiO2 and flux TiO2 is changed inversely compared with convectional TIG welding without flux. The arc voltageis increased by flux SiO2 whilst flux TiO2 does not have effect on the arc voltage. The reason of penetration depthincrease for SiO2 is due to the constriction of arc plasma and the change of surface tension gradient. The increaseof weld penetration depth with TiO2 only ascribes to the change of surface tension gradient.

Effects of fluxes with single component on weld depth in A-TIG welding of magnesium alloy

The effects of fluxes with single component on weld penetration depth in TIG welding of magnesium alloy were investigated. Seven kinds of halides were selected as the activating flux in the experiments. The effects of coating quantity of these fluxes on weld depth-to-width ratio were also studied. The results show that all of the selected halides can increase the weld depth under the same welding conditions compared with conventional TIG welding. The increase of penetration is different for the fluxes with different component. Among them, the flux of CdCl2 is the best, which can increase up to 334% of weld depth compared with the conventional TIG welding.

Effect of preheat on TIG welding of AZ61 magnesium alloy

The effects of preheat treatments on the microstructures and mechanical properties of tungsten inert gas （TIG）-welded AZ61 magnesium alloy joints were studied by microstructural observations, microhardness tests and tensile tests. The results showed that the vol- ume fraction of the lamellar β-Mg17（Al,Zn）12 intermetallic compound of in fusion zone （FZ） increased from 15% to 66% with an increase in preheat temperature. Moreover, the microhardness of the FZ and the ultimate tensile strength of the welded joints reached their maximum values when the preheat temperature was 300℃ because more lamellar β-Mg17（Al,Zn）12 intermetallic compounds were distributed at the α-Mg grain boundaries and no cracks and pores formed in the FZ of the welded joint.

High speed tandem TIG welding of ferritic stainless steel plate

Weld humping and undercut are the most common appearance defects in high speed welding. A high speed tandem TIG welding process was developed to suppress the formation of these appearance defects and to improve the productivity of TIG welding. In this paper, the mechanical properties and microstructure of joints obtained front tandem and single 77G welding were tested and compared. The results show that the sound weld appearance can be obtained by tandem TIG welding at the welding speed of 3 m/min for 1.5 mm thick 409L stainless steel plate. The mechanical properties of the tandem T1G welded joint are in the similar level with single TIG welded joint. The analysis of the tandem TIG welding process indicates that the assistant arc with a push angle can prevent the liquid metal flowing backward to the trailing region of weld pool and the premature solidification of thin liquid layer in the gouging region.

Effect of weld microstructure on weld properties in A-TIG welding of titanium alloy

Conventional TIG welding is known as its low productivity and limited weld depth in a single pass. Activating TIG welding (A TIG) can greatly improve the penetration when compared with the conventional TIG welding. The effects of five kinds of activating fluxes with single component (NaF, CaF 2, AlF 3, NaCl or CaCl 2) on penetration, microstructure and weld mechanical properties during the TIG welding of titanium alloy Ti 6Al 4V were studied. Compared with the conventional TIG welding, the experimental results show that the fluxes can greatly improve the penetration at the same welding specifications. This is because of the constriction of anode spots and the change of surface tension grads. Among them the effect of flux NaF is the best in the weld tensile strength, and the effect of flux CaF 2 on the weld bend intension is the best. The appearance of inferior crystal grains and the structure of trident crystal grains are the main reasons that the performance of weld with fluoride is improved. These experimental results can be used as an aid for selecting suitable activating flux for titanium alloy.

焊前热处理对J55钢自动TIG焊接头组织性能的影响

目的针对J55钢焊接性较差、接头热影响区(HAZ)易出现脆硬马氏体组织等问题,在焊前对J55钢母材进行热处理,研究其焊接接头。方法在焊前对J55钢母材进行了760℃与880℃的热处理,采用TIG焊方法进行了焊接,研究了热处理前后TIG焊对接头显微组织和力学性能的影响。结果经焊前760℃热处理后,母材中的珠光体(P)含量显著减少并且发生细化,焊后接头HAZ组织转变为晶界铁素体(GBF)、针状铁素体(AF)和P;经焊前880℃热处理后,母材的显微组织主要为多边形铁素体(PF)和AF,在焊后接头的HAZ中形成了PF、贝氏体(B)和M-A组元。2种热处理接头焊缝区(WZ)的盖面层组织为GBF和AF,靠近和远离盖面层的打底层组织主要为PF和P;未热处理接头HAZ组织为PF、B和马氏体(M)。与2种热处理接头相比,未热处理接头的显微硬度居中,抗拉强度最高,延伸率最低,拉伸断裂位于熔合线与HAZ之间,断口呈脆性断裂特征。与760℃热处理相比,经880℃热处理的焊接接头HAZ显微硬度最高值达523HV,为760℃热处理的2.2倍,接头抗拉强度提高了2.2%,但延伸率降低了7.6%。2种热处理接头拉伸后均断裂在母材,断口均呈韧性断裂特征。结论先在焊前对J55钢母材进行热处理再采用TIG焊进行焊接,可获得力学性能优异的焊接接头,在焊前760℃热处理的条件下,得到的接头力学性能最优。

2219/5A06异种铝合金脉冲VP-TIG焊工艺

为了获取最优的焊接接头性能,采用脉冲VP-TIG焊方法,对5.5 mm厚的2219-T87和5A06-H112异种铝合金进行单层单道对接试验,设计了5种工艺参数3个因素水平的L_(27)(3^(9))型正交试验,同时考虑3种因素间的交互作用,分析各因素对接头抗拉强度的影响,结果显示工艺参数对接头性能的影响从主到次依次为:焊接速度-坡口角度-峰值电流-脉冲频率-送丝速度;通过正交优化,获得了理想的无缺陷焊接接头,对优化后焊接接头的力学性能、微观组织与腐蚀性能进行试验.结果表明,接头断裂沿着2219侧熔合线附近最大应变处发生,该位置是整个接头中硬度最低的区域,2219侧熔合线和焊缝耐蚀性最差,是点蚀优先发生的位置.

TC32钛合金TIG焊接接头显微组织及力学性能研究

利用不同成分的填充材料对TC32进行TIG焊接试验,分析接头不同区域的显微组织和力学性能。结果表明,采用TC4实心焊丝、TC32药芯焊丝和Ti-Al-V-Zr系药芯焊丝所获的焊接接头组织均不同,焊缝区宏观形貌均由上中部柱状晶区和下部等轴晶区组成,热影响区均出现三个不同的亚区;三种焊接接头的热影响区硬度显著高于母材,且每组接头的显微硬度在上、中、下区域有相同变化趋势;在焊态条件下,接头的抗拉强度与母材相当,但塑性较差。研究表明,药芯焊丝与实心焊丝相比较,药芯焊丝更容易产生气孔缺陷,导致接头的强度和韧性降低。

BFe10-1-1合金K-TIG焊接接头的组织和性能

采用Keyhole TIG(K-TIG)焊接工艺开展了10 mm厚BFe10-1-1铜合金板的焊接试验。结果表明:采用K-TIG焊实现了单面焊双面成型,焊缝成型美观,接头焊缝截面无气孔、未熔合、裂纹等缺陷;焊缝区主要为枝晶状α组织,由熔合线向焊缝中心生长延伸;母材区和热影响区的组织是孪晶状的α相,且热影响区距离焊缝越近,其晶粒尺寸越大。焊缝区的硬度值较高,从焊缝到母材的硬度值先降低再增加,近熔合线的焊缝区和打底焊缝上部区域出现轻微软化。接头平均抗拉强度为346.5 MPa,断裂位置为母材;在α=180°、d=4 t条件下进行侧弯测试,未发现裂纹。

活性剂对厚壁管TIG焊接的影响

TIG焊接焊缝质量高但其熔深小,生产率低。若在被焊工件表面涂敷一层特殊的活性剂,再进行TIG焊接,能够起到增大熔深的效果,即A-TIG焊。研究了三种不同活性剂对φ54 mm×8 mm厚的20#钢厚壁管TIG焊接的影响,研究发现:添加3号活性剂的接头外观质量最好,添加2号活性剂的次之,添加1号活性剂的最差;三种活性剂熔深均大于8 mm,熔深增加量均达到3.211 mm以上,而不添加活性剂的厚壁管则不能焊透。使用2号活性剂增加焊接熔深的效果最明显。20#钢管母材显微组织是铁素体和珠光体,接头热影响区组织相较于母材更粗大,焊缝区的晶粒进一步长大,在原奥氏体晶界处产生针状粗大的先共析铁素体,主要组织仍为珠光体和铁素体混合物。添加三种活性剂的焊缝组织无明显变化,获得的焊接接头拉伸试样均断裂在母材,焊缝强度均高于母材。

N06022镍基合金TIG+SMAW焊接接头微观组织及力学性能

采用钨极氩弧焊(TIG)+焊条电弧焊(SMAW)对10 mm厚的N06022镍基合金进行焊接,分析研究接头的微观组织、显微硬度、腐蚀性能和拉伸性能。研究表明:采用TIG+SMAW焊接接头表面成形良好,整个焊缝呈银白色,半椭圆状的鱼鳞纹均匀分布;母材与焊缝区组织存在明显的分界线,且无明显的热影响区域,焊缝区域组织为等轴晶和树枝晶组织;整个焊接接头的硬度呈“M”形分布,NZ区域的显微硬度较为稳定,在250 HV附近,HAZ区较BM区域高,而较NZ区域低,从HAZ区域到NZ区域接头的显微硬度变化不大;焊接接头的平均抗拉强度(799 MPa)高于母材(782 MPa),焊接接头较母材提高了2.56%,保证了该类焊接结构的可靠运行,接头的断裂形式为韧性断裂;接头腐蚀性能满足设备技术要求和标准规定。

2.25Cr1Mo0.25V耐热钢与304不锈钢AA-TIG焊接接头组织及性能研究

采用电弧辅助活性AA-TIG焊对2.25Cr1Mo0.25V耐热钢和304不锈钢管进行异种钢材焊接,并对其焊接接头的组织、硬度及力学性能进行分析。结果表明,使用AA-TIG焊能够一次性焊透2.25Cr1Mo0.25V耐热钢和304不锈钢,得到成形良好的焊接接头。焊缝处无裂纹等焊接缺陷,焊缝处各元素在焊缝水平方向分布均匀。在靠近两侧母材的焊缝区,Cr、Fe、Ni元素有一定的梯度,但无明显偏聚。焊接接头两边的母材区硬度值较低,在焊缝区域硬度达到最大,焊缝区域的硬度波动范围在400~489 HV之间,最终拉伸试样都断在304母材上,得到的平均拉伸强度为406 MPa,最大的抗拉强度为542 MPa。

30CrMnSiA与1Cr18Ni9Ti异种钢TIG自动焊工艺研究

本文针对30CrMnSiA和1Cr18Ni9Ti异种钢焊接难点,开展TIG自动焊接工艺研究。采用TIG自动焊工艺所获得的焊接接头表面及内部质量均无缺陷。通过对焊缝显微组织进行分析,1Cr18Ni9Ti侧热影响区组织晶粒粗化,而30CrMnSiA侧热影响区出现了比母材细小的组织。经力学性能测试发现室温拉伸强度接近于1Cr18Ni9Ti母材,应用TIG自动焊接工艺能够获得良好的力学性能。

Experimental study on activating welding for aluminum alloys

TIG welding and EB welding Jbr aluminum alloy 3003 were carried out to study the effects of activating flux on weld penetration of activating welding for aluminum alloys. SiO2 was used as the activating flux. It is found that, SiO2 can increase the weld penetration and decrease the weld width of FBTIG when the flux gap is small. For A-TIG welding and EB welding with focused mode, the weld penetrations and the weld widths increase simultaneoudy. SiO2 has little effect on the weld penetration and weld width of EB welding with defocused mode. It is believed that, change of surface tension temperature gradient is not the main mechanism of SiO2 improving weld penetration of activating welding for aluminum alloys.

Activated flux tungsten inert gas welding of 8 mm-thick AISI 304 austenitic stainless steel

AISI 304 stainless steel plates were welded with activated flux tungsten inert gas(A-TIG) method by utilizing self-developed activated flux. It is indicated from the experimental results that for 8 mm-thick AISI 304 stainless steel plate, weld joint of full penetration and one-side welding with good weld appearance can be obtained in a single pass without groove preparation by utilizing A-TIG welding. Moreover, activated flux powders do not cause significant effect on the microstructure of TIG weld and the mechanical properties of A-TIG weld joints are also superior to those of C-TIG(conventional TIG) welding.

小孔TIG焊技术在中大厚度TC4板上的应用研究

对14 mm及26 mm厚TC4板进行了小孔TIG焊工艺试验,研究了工艺参数对焊缝成型、内部质量及接头组织性能的影响。结果表明,采用优化的小孔TIG焊工艺可以不开坡口实现14 mm厚TC4板的单面焊双面成型,焊缝及热影响区出现马氏体组织转变,接头与母材相比出现明显硬化。对于26 mm厚Y型坡口试板,采用小孔TIG焊从背面打底可以完成14 mm钝边熔透焊,从正面打底可以完成10 mm钝边熔透焊,打底焊道美观,内部质量优,可直接采用常规TIG焊工艺填充盖面。制备的中大厚度TC4板接头强度与母材的相当,工艺性能良好,焊缝冲击性能与母材的相当,热影响区冲击性能优于母材的。

大厚度TA17钛合金磁控窄间隙TIG焊接头组织和力学性能

对120 mm厚的TA17钛合金板进行了磁控窄间隙TIG焊接试验,系统表征了该焊接接头不同区域的显微组织和力学性能,并阐明接头显微组织演变过程及其对力学性能的影响。结果表明沿接头横向存在显著的组织不均匀性:靠近焊缝的母材区主要由拉长的α晶粒和沿晶界分布的β相构成,接头热影响区组织为粗大α集束构成的魏氏组织,熔合区为细小α片层交错组成的网篮组织。沿接头厚度方向,显微组织差异较小,接头上层熔合区观察到少量马氏体片层组织。接头熔合区硬度显著低于母材区的,拉伸过程中熔合区优先发生屈服,随后成为塑性变形集中区域,导致接头强度和塑性较母材降低。