Conventional TIG Welding Research Articles

A Study of Laser Aided Activating TIG Welding

Laser aided activating TIG welding was called LA-TIG. At first, the surface of weld was melted by the mini power laser protected by oxygen, and then the conventional TIG was used to cover the weld, which achieved the target of the weld with deeper penetration and narrower width. In this article, the weld bead morphology, arc images, microstructures and mechanical properties of laser aided activating TIG welding joint were analyzed. The results shows that the penetration increased significantly, excellent weld appearance and finger shape penetration were gained by laser aided activating TIG welding. It was found that the arc images of the LA-TIG was only the enlarged form compared with which observed in the conventional TIG and the arc constriction was also observed. LA-TIG weld exhibits better mechanical properties than the conventional TIG welding. Thus laser aided activating TIG welding was developed as a novel active welding method.

EFFECT OF A-TIG WELDING PROCESS PARAMETERS ON PENETRATION IN MILD STEEL PLATES

TIG welding is mostly used to weldthin sections for high surface finish. A major drawback in the processis having very small penetration as compare to other arc welding process. The problem can be avoided by using active flux in conventional TIG welding. In the present study investigate theoptimization of A-TIG welding process on mild steel for an optimal parameter by using Taguchi technique. Theeffect of various process parameters (welding current (I), welding speed (V), active flux) .IN the present study efforts were made to increase the weld penetration by appling the active flux and to optimize the process parameters.

Microstructural Investigations on ATIG and FBTIG Welding of AA 2219 T87 Aluminum Alloy

Limitation in penetration depth is a concern in conventional TIG welding process. To improve penetration capability of TIG process, both Activated TIG (ATIG) and Flux Bounded TIG (FBTIG) are investigated in aluminum alloy AA 2219 T87. Undesirable arc wandering and cracking tendency are observed in ATIG welds. Microstructural investigation reveals ATIG welds are prone for liquation cracks. Morphology of the cracks along with the attributable factors are explained with optical and SEM (Scanning Electron Microscope) micrographs. Energy Dispersive Spectroscopy (EDS) results are also presented to explain the solute enrichment in the grain boundaries of the ATIG welds. FBTIG is found to produce good quality welds and is more suitable for welding aluminum alloys. Key words: Flux Assisted TIG; ATIG; FBTIG; Penetration Improvement; Microstructure; AA2219.

Experimental Research of Activating Fluxes in A-TIG Welding of 5052 Aluminum Alloy

AC A-TIG welding on 5052 aluminum alloy was investigated. The single component of oxide TiO2, SiO2, Cr2O3, V2O5 and halide CaF2 was served as activating fluxes to study the effect on weld penetration and weld forming. The experimental results show that weld penetration can be increased and welding productivity can be improved in A-TIG welding. Activating fluxes, especially TiO2 and SiO2, have more significant effect on weld penetration than conventional TIG welding, moreover the better weld shape formed after coating activating flux is obtained, weld width has slight decrease that makes HAZ of A-TIG welding smaller.

Comparação da eficiência térmica entre soldagem A-TIG e TIG convencional

O processo A-TIG (soldagem TIG com fluxo ativo) consiste em depositar uma fina camada de fluxo sobre a superfície da peça antes da soldagem. A deposição da camada pode ser feita através de pincel ou spray, e a soldagem é realizada após a secagem. Verifica-se que com este processo é possível aumentar a produtividade (velocidade de soldagem) em até três vezes em comparação ao processo TIG convencional. Entretanto, os fenômenos físicos associados a este ganho prático de produtividade ainda permanecem sob discussão. Desta forma, o objetivo deste trabalho é analisar a eficiência térmica (rendimento térmico) e aporte térmico na soldagem com o processo A-TIG em comparação com o processo TIG convencional, utilizando-se de um calorímetro por nitrogênio líquido, como forma de contribuir para o melhor entendimento dos fenômenos físicos associados. Pelos resultados encontrados, se verifica que os efeitos da soldagem A-TIG sobre a geometria do cordão de solda se apresentaram de acordo com trabalhos anteriores. Em adição, de forma inédita, se destaca a menor eficiência térmica da soldagem A-TIG em comparação com a soldagem TIG convencional. A partir dos resultados encontrados, se nota que a constrição do arco é mais importante que a redução da eficiência térmica.

Effect of Ternary Fluxes on Depth of Penetration in A-TIG Welding of AISI 409 Ferritic Stainless Steel

TIG welding is a preferred process for producing quality weld joints. However, because of its characteristic shallow depth of penetration, productivity achieved by this process is low. Depth of penetration of conventional TIG welding can be improved by Activated TIG (A-TIG) welding. In A-TIG welding, a thin layer of flux comprising mixtures of oxides, fluorides and chlorides is applied in the area to be welded to obtain two to three fold increase in depth of penetration. In this study, three single component fluxes viz., SiO2, TiO2 and Cr2O3 were employed for welding of AISI 409 ferritic stainless steel. Experimental trials were designed for the use of ternary fluxes. From the obtained results on bead geometry, using Minitab 16 software coupled with Matlab R2010 an optimum combination of these fluxes for maximum penetration was estimated. Confirmation test showed that two fold increase in depth of penetration could be achieved in A-TIG welding by using this flux combination over conventional TIG welding.

Development of simplified active flux tungsten inert gas welding for deep penetration

A new advanced active flux tungsten inert gas (AA-TIG) welding technique, named cap active flux tungsten inert gas (CA-TIG) welding using atmospheric oxygen, was proposed to increase the penetration depth of a weld. Only a simple nozzle cap with an air inlet was used for the welding. Flowing inert gas used as a shielding gas through a nozzle center led to the aspiration of oxygen from the atmosphere to the molten pool. The penetration depth was increased by the reversal of the Marangoni convection due to the entrained oxygen, and it reached three times deeper than that of the conventional TIG welding. Additionally, no degradation of the tungsten electrode was observed because it was protected by the inert gas. The penetration depth was changed by the oxygen content in the molten pool and it could be easily controlled by the nozzle cap design and the welding parameters.

Efeito da densidade do fluxo e da presença de aditivos na soldagem ATIG de aço inoxidável austenítico

A soldagem ATIG é uma variante simples do processo TIG convencional que permite aumentar a penetração da solda e, por exemplo, possibilitar a soldagem em um passe, com penetração total e sem abertura de chanfro, para juntas com espessura de 5 mm ou mais. Diferentes mecanismos foram propostos para explicar este efeito com destaque para o da contração do arco pela presença de íons negativos e o da alteração no movimento de metal líquido na poça de fusão associada com variações da tensão superficial em função da temperatura. O presente trabalho avalia o efeito da quantidade de um fluxo de um componente (óxido de cromo III, Cr2O3) colocado na superfície da peça e de adições de KClO4 e Al2O3 no formato do cordão de solda. Foram realizados três conjuntos de experimentos consistindo na deposição de cordões sobre chapa de aço inoxidável austenítico ABNT 304 com 5 mm de espessura. No primeiro conjunto, variou-se a quantidade de fluxo usada, no segundo, estudou-se o efeito de adições de KClO4 e, no terceiro, de Al2O3. Foram medidos os sinais elétricos (corrente e tensão) durante a soldagem e, em seções transversais dos cordões, a largura, a penetração e a área do cordão. Os resultados indicaram uma pequena variação na tensão de soldagem (aumento inferior a 1 V) na passagem da soldagem TIG para a ATIG. A concentração superficial de fluxo afetou a penetração da solda, ocorrendo um aumento brusco de penetração e área do cordão para concentrações entre 7,5 e 15 g/m², seguido por uma variação mais suave para concentrações maiores (até 120 g/m²). Por outro lado, enquanto a adição de KClO4, claramente reduziu o aumento de penetração causado pelo fluxo, a adição de Al2O3 teve um efeito menos significativo no processo.

The New Technology of Softening Control for Copper Weld Joint Using Pretension Method

In conventional TIG welding, copper weld joint and its heat affected zone (HAZ) have the disadvantage of softening. In this paper, the new technology of softening control for copper weld joint using pretension method was studied. The results show that hardness of copper weld seam and its HAZ was increased by pretension. Moreover, the tensile strength and elongation of the welding joint were obviously improved. Keywords: pretension, weld joint, softening control, copper

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 realtime 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.

Creep rupture strength of activated-TIG welded 316L(N) stainless steel

316L(N) stainless steel plates were joined using activated-tungsten inert gas (A-TIG) welding and conventional TIG welding process. Creep rupture behavior of 316L(N) base metal, and weld joints made by A-TIG and conventional TIG welding process were investigated at 923 K over a stress range of 160–280 MPa. Creep test results showed that the enhancement in creep rupture strength of weld joint fabricated by A-TIG welding process over conventional TIG welding process. Both the weld joints fractured in the weld metal. Microstructural observation showed lower δ-ferrite content, alignment of columnar grain with δ-ferrite along applied stress direction and less strength disparity between columnar and equiaxed grains of weld metal in A-TIG joint than in MP-TIG joint. These had been attributed to initiate less creep cavitation in weld metal of A-TIG joint leading to improvement in creep rupture strength.

Study of the Effect of Active Fluxes in Gas Tungsten Arc Welding

In order to investigate the effect of active fluxes on weld penetration, angular distortion and weld morphology in gas tungsten arc welding (GTAW), three types of oxide fluxes-CaO, TiO2and Al2O3-were used in the welding of 5mm think stainless steel plates. Those powders were applied through a thin layer of the flux to produce a bead on plate welds. The results showed that compared with conventional TIG welding, increased weld penetration and reduced angular distortion of the weld piece were obtained with the application of active fluxes. However, the weld morphology was not changed significantly when the powders were coated on the surface of steel. It was also found that each of the powders has a fittest range in penetration increment. Whether the rate of the coating run out of the range, the effects of these active fluxes on the increased weld penetration were not obvious. The CaO flux has a narrow effective range for deep penetration, while the Al2O3powder does have no effect on A-TIG penetration. The mechanism of those different performances has not been found out. According to the investment, the mechanism of active fluxes for the increased weld penetration and reduced angular distortion is related to the contraction of the arc.

Ferritic stainless steel welding with the A-TIG process

The main advantage of the TIG with flux process (A-TIG welding) is the possibility of obtaining greater penetration of the weld bead while employing the same welding parameters as conventional TIG welding. Various studies have shown the influence of active fluxes on the geometric characteristics of stainless steel austenitic welds. However, little is known about the influence of this process on the geometric and metallurgical characteristics of the weld beads in ferritic stainless steels. In this work, different types of flux are applied when welding ferritic stainless steel with the objective of verifying possible influences on the weld bead's profile, on its visual appearance, on the microstructure, on the hardness of the welded zone and on the impact resistance (Charpy test). The bead-on-plate welds were produced without using any addition metal. Six types of flux were used – one being an oxide produced in a laboratory (TiO2) and five commercial fluxes. The results showed that use of the flux allows an increase in penetration with significant changes in the appearance of the weld bead. It was also confirmed that the microstructure and the hardness of the weld bead for the steel studied were not affected by the type of flux used, with the microstructure analysed under an optical microscope. The steel in the study showed a high degree of fragility at ambient temperature.

Weld Pool Shape Variations and Electrode Protection in Double Shielded TIG Welding

A new welding method named double shielded TIG welding has been investigated and is described in this paper. It is applicable to the TIG process and can improve the weld depth/width ratio and protect the electrode from oxidation during the welding process. A two pipeline structure is designed in the torch. Pure inert gas passes though the inner pipeline which keeps the arc stable and protects the tungsten electrode. A mixed gas containing an active gas passes through the outer pipeline. The active element which is decomposed from the active gas dissolves in the weld pool so as to change the Marangoni convection from an outward to an inward direction, and, as a result, the weld pool shape becomes deep and narrow. The double shielded TIG welding method increases the weld depth by about 2~3 times over the conventional TIG welding. The effects of the active gas (oxygen) in the outer pipeline on the weld pool shapes are discussed. Heavy oxide layer is considered to weaken the Marangoni convection and changes the weld pool shape.

Penetration increase of AISI 304 using ultrasonic assisted tungsten inert gas welding

Ultrasonic assisted tungsten inert gas (U-TIG) welding method was developed. Both U-TIG and conventional TIG welding of AISI 304 stainless steel with 5 mm thickness were experimentally studied in this paper. The results show that the penetration depth is increased up to 300% for weld made with U-TIG welding compared with conventional TIG welding. Ultrasonic energy enhances arc push force, causes a continual high frequency oscillation in the arc plasma and increases welding penetration. These effects are thought to be responsible for enhancing the welding efficiency and improving the appearance of stainless steel weld joints.

Enhancement in Mechanical Properties of Tailored Welded Blanks Due to Pulsed Tig Welding

The present paper reports experimental results on enhancement in mechanical properties of tailored welded blanks due to Pulsed TIG welding. Experimental evaluation of various mechanical properties has been made under the influence of varying peak current, pulse frequency and pulse width. The resulting welds have been checked for ultimate tensile strength, % elongation, hardness, toughness and fatigue life. The mechanical properties of Pulsed TIG welded tailored blanks have further been compared with that produced by conventional TIG welding. It has been observed that the Pulsed TIG welding can successfully be employed to improve the mechanical properties of tailored welded blanks. The results of experiments have been analyzed and related discussion has been presented.

Soldagem de um aço inoxidável ferrítico com o processo A-TIG

O processo de soldagem TIG com fluxo (processo A-TIG) apresenta como principal vantagem a possibilidade de se obter uma maior penetração do cordão de solda empregando os mesmos parâmetros de soldagem do processo TIG convencional. Diversos estudos mostram a influência dos fluxos ativos sobre as características geométricas das soldas em aços inoxidáveis austeníticos, porém pouco se sabe sobre a influência deste processo nas características geométricas e metalúrgicas de cordões de solda em aços inoxidáveis ferríticos. Neste trabalho são aplicados diferentes tipos de fluxo na soldagem de aço inoxidável ferrítico com o objetivo de verificar possíveis influências no perfil do cordão de solda, no seu aspecto visual, na microestrutura, na dureza da zona fundida e na resistência ao impacto (ensaio Charpy). As soldagens "bead-on-plate" foram realizadas sem metal de adição. Foram utilizados seis tipos de fluxo, sendo um óxido elaborado em laboratório (TiO2) e cinco fluxos comerciais. Os resultados mostraram que a utilização do fluxo permite um aumento na penetração com mudanças significativas no aspecto do cordão de solda. Verificou-se ainda que a microestrutura e a dureza do cordão de solda do aço estudado não foram afetadas pelo tipo de fluxo utilizado, com a microestrutura analisada em microscópio óptico. O aço em estudo mostrou um alto grau de fragilidade à temperatura ambiente.

Observations of Molten Pool Behavior during A-TIG Welding

The effects of flux on fluid flow of the weld pool surface and arc profiles are observed in conventional TIG welding and in A-TIG welding by using high-speed video camera. The fluid flow behavior is visualized in realtime by micro focused X-ray transmission video observation system. The results indicate that stronger inward fluid flow patterns leading to weld beads with narrower width and deeper penetration can be apparently identified in the case of A-TIG welding. The flux can change the direction of fluid flow in welding pool and make the fluid flow speed increase four times. It agrees well with the simulation results.

ATIG Welding of Duplex Steel

The ATIG welding which is the high productivity version of conventional TIG welding, parallel with productivity increasing has some advantageous effect both on HAZ and weld joint grain structure. In this paper the effect of ATIG welding on austenite/ferrite ratio in duplex steel will be represented with experimental results performed on 8 mm thick 2205 type duplex steel. As collateral benefit through these results new evidences are originated to prove the “reversed Marangoni effect” theory.

Study of mechanism of activating flux increasing weld penetration of AC A-TIG welding for aluminum alloy

When multi-component flux AF305 is used as surface activating flux for an aluminum alloy, the weld penetration of activating flux-tungsten inert-gas (A-TIG) welding is over two times more than that of conventional TIG welding. Using A-TIG welding with the modes of alternating current (AC), direct current electrode negative (DCEN) and direct current electrode positive (DCEP), respectively, the flux differently affects weld penetration when the polarity is different. After studied the effect of compelled arc constriction on weld penetration of AC welding, it is believed that the constriction of the whole arc root is not the main mechanism that flux AF305 dramatically improves weld penetration. The penetration has a relationship with the separate distribution of slag on the weld surface. Then, an observation of scanning electron microscopy (SEM) and an electronic data systems (EDS) analysis of slag were performed respectively. The separate distribution of slag on the weld pool during welding and the great constriction of arc spots were confirmed by TIG welding with helium shielding gas. The relationship between slag distribution and weld penetration was studied by adding aluminum powder into flux AF305 to change the distribution of slag. During welding, the separate distribution of slag on the weld pool results in the great constriction of arc spots, an increase in arc spot force, and an increase in Lorentz force within the arc and weld pool. Finally, the weld penetration is increased.