A-TIG Welding of a Stainless Steel (original) (raw)
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A-TIG welding process for enhanced-penetration in Duplex stainless-steel: effect of activated fluxes
Materials and Manufacturing Processes, 2019
Weldability of duplex stainless steel (DSS) is an important issue in fabrication of pipes at petrochemical industries. Well-established tungsten inert gas (TIG) welding process has the limitations of lesser penetration; however, process parameters (such as current and voltage) need to increase to attain deeper penetration, which, in turn, affects the material's property owing to increased heat energy. Use of activated fluxes generate the extra heat energy with same process parameters and causes the deeper penetration and increased dilution. The aim of the present study is to investigate the effect of activated fluxes on penetration, dilution, weld chemistry, weld microstructure, gas and slag metal reactions which has resulted from extra heat energy produced. Different activated fluxes were investigated in context of heat energy, associated penetration, dilution and weld pool properties. The oxygen content in activated flux has played significant role in hot cracking and void formations in the weld. Similarly, it also changes the surface tension gradient of weld pool considerably. Dendrite growth is predominant in oxide-based fluxes and this growth in austenite and ferrite dendrite has been evidenced as a function of oxygen content. The process with relevant mechanisms is elaborated in the present study.
A novel perception toward welding of stainless steel by activated TIG welding: a review
Materials and Manufacturing Processes, 2020
Stainless steel is a widely used material in various industries such as aerospace, chemical processing and transportation. Tungsten Inert Gas (TIG) or Gas Tungsten Arc Welding (GTAW) process is extensively used for joining thin sections of stainless steel. However, it is not useful in joining thick sections in a single pass. Activated TIG (A-TIG) significantly increases weld penetration up to 1.5-4 times in a single pass. Because of its deep penetration ability, A-TIG is the focus of research amongst the researchers. This article reports the mechanisms associated with A-TIG, effects of various weld parameters on weld bead geometry and optimization techniques to optimize the process variable of the A-TIG welding process. The present work also analyzes the consequence of activated fluxes on microstructure and mechanical properties of A-TIG weld metal. Along with this, recent developments in the TIG welding process have been discussed. The study concludes that the A-TIG welding process enhances the weld penetration to a great extent, but a high amount of slug gets deposited on the weld surface. This drawback can be overcome by novel variants of the A-TIG welding process such as Flux Bounded TIG (FB-TIG) and Flux Zone TIG (FZ-TIG) welding processes which enhance the future scope of research.
Transactions of Indian Institute of Metals, volume: 70, Issue 3, 2017
This research investigation articulates the joining of AISI 316 L austenitic stainless steel plates of thickness 5 mm by activated tungsten inert gas (A-TIG) welding. Prior to the welding, the optimization of process parameters and the selection of suitable flux have been carried out to join the plates in a single pass welding. The experimental results show that the complete weld penetration can be achieved by using activating flux. The microscopic study divulges the presence of delta ferrite, sigma phase and various forms of austenite in the weld zone. Fischer Feritscope result indicates that the delta ferrite content in the weld is higher (7.8 FN) than the base metal (1.3 FN) which results in superior mechanical properties of the weld. Field Emission-Scanning Electron Microscope (FE-SEM) fractography reveals that the failure of weldments occurs in ductile mode. 180°bend test study reveals the good ductility of the joint.
Optimization of the A-TIG welding for stainless steels
IOP Conference Series: Materials Science and Engineering
The paper presents the influence of the activation flux and shielding gas on tungsten inert gas (A-TIG) welding of the stainless steel. In introduction part, duplex stainless steel was analysed. The A-TIG process was explained and the possibility of welding stainless steels using the A-TIG process to maximize productivity and the cost-effectiveness of welded structures was presented. In the experimental part duplex, 7 mm thick stainless steel has been welded in butt joint. The influence of activation flux chemical composition upon the weld penetration has been investigated prior the welding. The welding process was performed by a robot with TIG equipment. With selected A-TIG welding technology preparation of plates and consumption of filler material (containing Cr, Ni and Mn) have been avoided. Specimens sectioned from the produced welds have been subjected to tensile strength test, macrostructure analysis and corrosion resistance analysis. The results have confirmed that this type of stainless steel can be welded without edge preparation and addition of filler material containing critical raw materials as Cr, Ni and Mn when the following welding parameters are set: current 200 A, welding speed 9,1 cm/min, heat input 1,2 kJ/mm and specific activation flux is used.
Journal of Manufacturing Processes, 2015
Gas tungsten arc welding is fundamental in those applications where it is important to control the weld bead shape and the metallurgical characteristics. This process is, however, of low productivity, particularly in the welding of large components. Maximum 2-3 mm thick plates of carbon steel, stainless steel can be welded with GTAW process in the Argon shielding under autogenous mode. The activated flux TIG (A-TIG) welding process, developed by the Paton welding Institute in the 1960s, is now considered as a feasible alternative to increase the process productivity. A-TIG welding uses a thin layer of an active flux that results in a great increase in weld penetration. This effect is generally, connected to the capture of electrons in the outer parts of the arc by elements of high electronegativity, which constrict the arc causing an effect similar to that used in plasma welding [1]. Grade 91 (modified 9Cr-1Mo or P91 steel) steels are structural material and are widely used for high temperature components of power plants, petrochemical and nuclear industry because of its superior mechanical properties such as yield, ultimate tensile, and creep rupture strengths matching or exceeding that of 9Cr-1Mo, 2¼Cr-1Mo, HT9, EM12, and 304 stainless steel [2], but depth of weld penetration achievable in single pass with autogenous TIG welding is still lesser in Cr-Mo steel [3]. A novel variant of the autogenous TIG welding process (A-TIG) was applied on P91 steel in which oxide powders CaO, Fe 2 O 3 , TiO 2 , ZnO, MnO 2 and CrO 3 (elements of period IV in the periodic table of elements) were used to produce a bead on plate welds. Process parameters were optimized to achieve the desired depth of penetration at the lowest heat input possible. Variation in the depth of penetration and weld bead width as a function of current at fixed torch speed was determined employing A-TIG welding process. The purpose of the present work was to investigate the effect of oxide fluxes on weld morphology, arc voltage obtained with A-TIG welding, which applied to the welding of 6 mm thick modified 9Cr-1Mo steel plates. The experimental results indicated that the increase in the penetration is significant with the use of Fe 2 O 3 , ZnO, MnO 2 and CrO 3. Full penetration weld secured with the use of these fluxes.
Journal of Advanced Materials and Processing, 2012
Received: 1 October 2011 Accepted: 1 March 2012 Published online:14 July 2012 Gas tungsten arc welding is fundamental in those industries where it is important to control the weld bead shape and its metallurgical characteristics. However, compared to the other arc welding process, the shallow penetration of the TIG welding restricts its ability to weld thick structures in a single pass (~ 2 mm for stainless steels), thus its productivity is relativity low. This is why there have been several trials to improve the productivity of the TIG welding. The use of activating flux in TIG welding process is one of such attempts. In this study, first, the effect of each TIG welding parameters on the weld’s penetration depth was shown and then, the optimal parameters were determined using the Taguchi method with L9 (3) orthogonal array. SiO2 and TiO2 oxide powders were used to investigate the effect of activating flux on the TIG weld penetration depth and mechanical properties of 316L austeniti...
The effect of activating fluxes in TIG welding by using Anova for SS 321
Gas tungsten arc welding is fundamental in those industries where it is important to control the weld bead shape and its metallurgical characteristics. However, compared to the other arc welding process, the shallow penetration of the TIG welding restricts its ability to weld thick structures in a single pass (~ 2 mm for stainless steels), thus its productivity is relativity low. This is why there have been several trials to improve the productivity of the TIG welding. The use of activating flux in TIG welding process is one of such attempts. In this study, first, the effect of each TIG welding parameters on the weld's joint strength was shown and then, the optimal parameters were determined using the Taguchi method with L9 (9) orthogonal array. SiO2 and TiO2 oxide powders were used to investigate the effect of activating flux on the TIG weld mechanical properties of 321austenitic stainless steel. The experimental results showed that activating flux aided TIG welding has increased the weld penetration, tending to reduce the width of the weld bead. The SiO2 flux produced the most noticeable effect. Furthermore, the welded joint presented better tensile strength and hardness.
Welding of 304L Stainless Steel with Activated Tungsten Inert Gas Process (A-TIG
Gas tungsten arc welding is a popular process in those applications requiring a high degree of quality and accuracy. However, this process has a big disadvantage against the substantially high productivity welding procedures. Hence, many efforts have been made to improve its productivity. One of these efforts is the use of activating flux (A-TIG welding). In this study, the performance of A-TIG welding on 304L austenitic stainless steel plates has been presented. Two oxide fluxes, TiO 2 and SiO 2 were used to investigate the effect of A-TIG welding process on weld morphology, microstructure and mechanical properties of weldments. The experimental results indicated that A-TIG welding could increase the weld penetration and depth-to-wide ratio. It was also found that A-TIG welding could increase the delta-ferrite content of weld metals and improve the mechanical properties. Moreover, a 2D axial symmetric model was developed to simulate the flow behavior in the melting pool. These results were compared to those experiments carried out on a stainless steel (304L) melted by a stationary heat source.
Mechanical Engineering for Society and Industry
The activated-TIG (A-TIG) process is a recognised process for achieving higher depth-of- penetration (DoP) and it could be used for various stainless-steel grades welding. The oxygen content of oxide based activated fluxes provide the extra heat during decomposition of flux and result into deep penetration. This study reveals the effect of short weld time of 2 sec in stationary arc, shielding environment (Ar and Ar + 2.5 % H2) and an effect of oxygen element in activated flux (CrO3 and SiO2) on the microstructure and weld metal micro-hardness. Use of hydrogen mix shielding gas during A-TIG process has significant impact on the dilution rate, grain size and dendrite arm spacing. The fraction of oxygen in the flux and the presence of silicon in SiO2 flux play a significant role in achieving higher DoP. To evaluate the impact of different shielding environment on grain growth, the samples were investigated with weld pool morphology, depth of penetration, weld chemistry, optical microsc...
Effect of Active Gas on Weld Shape and Microstructure of Advanced A-TIG-Welded Stainless Steel
Acta Metallurgica Sinica (english Letters), 2016
Advanced A-TIG method was conducted to increase the weld penetration and compared with the conventional TIG welding process. A two-pipeline setup was designed to apply Ar ? CO 2 mixed gas as the outer layer, while pure argon was applied as the inner layer to prevent any consumption of the tungsten electrode. The results indicate that the presence of active gas in the molten pool led to the change in the temperature coefficient of surface tension so that the Marangoni convection turns inward and forms a deep weld zone. The increase in gas flow rate causes a decrease in the weld efficiency which is attributed to the increase in oxygen content in the weld pool and the formation of a thicker oxide layer on the weld surface. Moreover, the stir and the temperature fluctuation, led by double shielding gas, create more homogeneous nucleation sites in the molten pool so that a fine grain microstructure was obtained.