TIG-welded Joints Research Articles

Effects of X-rays Radiation on AISI 304 Stainless Steel Weldings with AISI 316L Filler Material: A Study of Resistance and Pitting Corrosion Behavior

This article investigates the effect of low-level ionizing radiation, namely X-rays, on the micro structural characteristics, resistance, and corrosion resistance of TIG-welded joints of AISI 304 austenitic stainless steel made using AISI 316L filler rods. The welds were made in two different environments: natural atmospheric conditions and a closed chamber filled with inert argon gas. The influence of different doses of radiation on the resistance and corrosion characteristics of the welds is analyzed. Welded material from inert Ar gas chamber TIG showed better characteristics and lesser irradiation damage effects.

Effects of X-rays Radiation on AISI 304 Stainless Steel Weldings with AISI 316L Filler Material: A Study of Resistance and Pitting Corrosion Behavior

This article investigates the effect of low-level ionizing radiation, namely X-rays, on the micro structural characteristics, resistance, and corrosion resistance of TIG-welded joints of AISI 304 austenitic stainless steel made using AISI 316L filler rods. The welds were made in two different environments: natural atmospheric conditions and a closed chamber filled with inert argon gas. The influence of different doses of radiation on the resistance and corrosion characteristics of the welds is analyzed. Welded material from inert Ar gas chamber TIG showed better characteristics and lesser irradiation damage effects.

Creep Deformation and Rupture Behavior of Single- and Dual-Pass 316LN Stainless-Steel-Activated TIG Weld Joints

Creep deformation and rupture behavior of single-pass and dual-pass 316LN stainless steel (SS) weld joints fabricated by an autogenous activated tungsten inert gas welding process have been assessed by performing metallography, hardness, and conventional and impression creep tests. The fusion zone of the single-pass joint consisted of columnar zones adjacent to base metals with a central equiaxed zone, which have been modified extensively by the thermal cycle of the second pass in the dual-pass joint. The equiaxed zone in the single-pass joint, as well as in the second pass of the dual-pass joint, displayed the lowest hardness in the joints. In the dual-pass joint, the equiaxed zone of the first pass had hardness comparable to the columnar zone. The hardness variations in the joints influenced the creep deformation. The equiaxed and columnar zone in the first pass of the dual-pass joint was more creep resistant than that of the second pass. Both joints possessed lower creep rupture life than the base metal. However, the creep rupture life of the dual-pass joint was about twofolds more than that of the single-pass joint. Creep failure in the single-pass joint occurred in the central equiaxed fusion zone, whereas creep cavitation that originated in the second pass was blocked at the weld pass interface. The additional interface and strength variation between two passes in the dual-pass joint provides more restraint to creep deformation and crack propagation in the fusion zone, resulting in an increase in the creep rupture life of the dual-pass joint over the single-pass joint. Furthermore, the differences in content, morphology, and distribution of delta ferrite in the fusion zone of the joints favors more creep cavitation resistance in the dual-pass joint over the single-pass joint with the enhancement of creep rupture life.

Comparison of microstructure and mechanical properties of TIG and laser welding joints of a new Al–Zn–Mg–Cu alloy

Sheets of a new Al–Zn–Mg–Cu alloy with T6 temper were welded using TIG and laser welding method. Microstructure characteristics and mechanical properties of joints were contrastively analyzed. Results show that the width of the fusion zone (FZ) and heat affected zone (HAZ) in laser joint is obviously smaller. The FZs in TIG and laser joints are both made up of dendritic equiaxed grains and lots of coarse particles, the mean grain size is 33.9μm and 6.1μm respectively, and the coarse particles are identified as the T (AlZnMgCu) phase. The two factors of grain size and alloying elements distribution are combined to result in almost the same microhardness of the two FZs. Moreover, the grain morphology, grain size and degree of recrystallization of the two HAZs are almost the same with base metal (BM). Due to the higher heating and cooling rate of welding thermal cycles in HAZ of laser joint, the microhardness is obviously higher. The minimum microhardness of the two joints is obtained in FZ where the fractures always occur in the tensile tests, the ultimate tensile strength of TIG and laser joints is 436.2MPa and 471.1MPa, the elongation of them is about 7.5% and 5.1% respectively.

Study on Creep Properties for TIG Welded Joints of CLAM Steel

The reduced activation ferritic/martensitic steel will withstand long-term high-temperature loading during the application in fusion reactors. In this work, the investigation of creep properties of China low activation martensitic (CLAM) TIG welded joints has been carried out at 823 K and with the applied stresses ranging from 180 to 260 MPa. The creep curve has been studied and plotted and the mathematical model has been constructed to analyze the creep mechanism. According to the results, the TIG welding joints of CLAM exhibited the typical three-stage creep curves, and at the constant temperature, the steady creep rate increased and the rupture time decreased with the increase of stress. The stress exponent n obtained from creep equation was higher than the typical values about 3–5, and activation energy Q was about 436 kJ/mol K, also higher than the self-diffusion energy of Fe (300 kJ/mol K), indicating the dislocation creep deformation mechanism, which is further proved by the microcosmic TEM images.

Study on the Fatigue Properties of the TIG Weld Joint with the Stainless Steel Conduit in Aircraft

The research focus on the material of the stainless steel thin conduit in aircraft, named 1Cr18Ni9Ti , and the TIG weld joint of which was investigated to analysis the fatigue properties. The fracture mechanics was used to analysis the crack initiation life and crack propagation life, and the fatigue surface was characterized with scanning electron microscope (SEM). The experimental and analytical results show that, the origin position of fatigue crack is the surface of the conduit. The stress concentration at the weld toe, the crystal structure is not uniform and Stress concentration in the heat affected zone (HAZ) and fusion line, so the fatigue cracks are easily generated in these locations. Delta K increases to a certain value, the HAZ has become one of the most dangerous position. The crack initiation life of HAZ in the total fatigue life is far higher than the proportion of crack propagation life.

Structure and properties of EB- and TIG-welded joints of high-strength two-phase titanium alloys

Structure and properties of EB- and TIG-welded joints of high-strength two-phase titanium alloys

Some advantages of butt joints of thin wrought aluminium alloys AMg5M and AMg6M produced by FSW, compared to TIG-welded joints

Some advantages of butt joints of thin wrought aluminium alloys AMg5M and AMg6M produced by FSW, compared to TIG-welded joints

Transformation Reactions by TIG Welded Joints of the Alloyed Steels Used for Endless Saw Blades

Butt welding by TIG method using a low alloyed steel wire with solid state transformation point, G3Si1, having 1 mm diameter is a feasible solution for both unique and small series production and for saw blades reshuffling made of dissimilar steels (rapid steel HS 2-10-1-8 for the active part and X32CrMoV4-1 steel for the tool holder).This paper analyses the structural and chemical composition modifications occurred in the heterogeneous welded joints areas by endless saw blades. The phenomena which manage the continuous evolution of the weld chemical composition are highlighted by Energy Dispersive X-Ray Analysis (EDX) and Scanning Electron Microscopy (SEM).

Microstructure and Properties of TA1 TIG Joint via Micro-Arc Oxidation

This paper applied the micro-arc oxidation technology to TIG weld joint based on titanium alloy. The optical microscope, SEM, XRD and polarization curve were used to analyze the joints metallographic phase, the coating morphology, the phase composition and corrosion resistance. Research results showed that the grain was grew gradually coarser from base metal to joint. The joint surface obtained a uniform morphology after micro-arc oxidation. The joint and base metal was made up of α-Ti and their coatings are mainly composed by rutile-TiO2. The surface morphology and phase composition are similar after micro-arc oxidation. Polarization curve tests demonstrated that the corrosion potential performance of the coating was enhanced by micro-arc oxidation.

Effects of nano-particles strengthening activating flux on the microstructures and mechanical properties of TIG welded AZ31 magnesium alloy joints

Abstract In this paper, AZ31 magnesium alloy joints were processed by nano-particles strengthening activating flux tungsten inert gas (NSA-TIG) welding, which was achieved by the mixed TiO2 and nano-SiC particles coated on the samples before welding tests. The macro/micro structural observation and mechanical properties evaluation of the welding joints were conducted by using optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray diffraction and tension and microhardness tests. The results showed that nano-particles strengthening activating flux effective improved the microstructure, microhardness in fusion zone, ultimate tensile strength of the TIG welding joints. In addition, the chemical reaction between part of SiC particles and AZ31 magnesium alloy produced Al4C3 and Mg2Si in the joints. The Al4C3 performed as nucleating agents for α-Mg and the dispersed Mg2Si and SiC particles enhanced the mechanical properties of the NSA-TIG welding joints. However, large heat input induced by the increase of the surface coating density of the nano-particles strengthening activating flux, increased the α-Mg grain sizes and weakened the mechanical properties of the welded joints. Therefore, the grain size of α-Mg, distribution of β-Mg17Al12, Mg2Si and SiC particles together influenced the evolution of the mechanical properties of the NSA-TIG welded AZ31 magnesium alloy joints.

Effect of Vanadium on Microstructure and Mechanical Properties of TIG Weld Joint of China Low Activation Martensitic Steel

The microstructure and mechanical properties on weld metal of China low activation martensitic steel were investigated in this paper. Welding wire of various Vanadium content was used and Tungsten Inert Gas welding was taken in this research. Microstructure and microhardness distributions along weld sample were detected. The component of weld metal and precipitated phases were observed by SEM and EDS. The results indicate that the addition of Vanadium can preferentially generate VC with Carbon. The precipitation of VC can enhance the hardness and tensile strength of the welding line, but decrease the impact toughness. At the same time the precipitation of Cr23C6 can provide a certain improvement on intergranular corrosion.

Microstructure and Stress Distribution on TIG Welded Joint of CLAM Steel

China low activation martensitic steel, 5 mm, were butt-welded in tungsten insert gas welding. Mechanical properties and microstructure in joints were studied in detail. The residual stress and deformation in the joints were numerically simulated using finite element method. Hardening at WM and softening in heat affected zone is detected in weld joint. The tensile specimen always undergoes localized necking and breaks in BM when the temperature of PWHT was lower than 800 °C. Until PWHT was done at 760 °C/30 min, the specimen ductile fractured in local area, but the absorbed energy of each CIT specimen is much lower than that of BM. The microstructure in WM is mainly tempered martensite with a little of delta ferrite. Tempered lath martensite containing dislocations and M23C6 carbides is the primary structural feature. According to the results of numerical studies, angular distortion is the main form of residual deformation, and caused by the transverse shrinkage of WM.

Studies on Improvement of Toughness in Modified 9Cr-1Mo Steel A-TIG Weld Joint

Modified 9Cr-1Mo steel plates of 10 mm thickness have been fabricated by double side welding procedure employing A-TIG welding process. Even after regular post weld heat treatment (PWHT), the impact toughness of A-TIG weld joint was found to be lower compared to that of conventional TIG weld joint. Therefore, post weld heat treatments of longer durations were considered for improving the toughness. Accordingly, in the present study, PWHT was carried out on A-TIG weld joints at 760 °C for 4, 6 and 8 h duration to optimize the tempering time for improving the toughness by careful study of the microstructures. It was observed that the A-TIG weld joint subjected to PWHT at 760 °C for 4 h exhibited higher hardness (410 VHN) and lower toughness (39 J) resulting from partial tempering of as-welded martensitic microstructure. The weld joint that was tempered at 760 °C for 6 h exhibited fully tempered martensite microstructure with extensive precipitation of M23C6 type carbide. The joint in this condition exhibits good impact toughness to a value of 96 J. After 8 h of tempering at 760 °C, the hardness decreased to a low value of 170 VHN and the toughness value increased beyond 200 J. It was attributed to over tempering of matensite resulting in coarsening of M23C6 precipitates and reduction in dislocation density. A-TIG weld joint with fully tempered martensite microstructure exhibit an average toughness value of 96 J and minimum single value of 75 J. Therefore, PWHT at 760 °C for 6 h was identified as the optimum tempering treatment for improving the impact toughness in mod. 9Cr-1Mo steel A-TIG weld joint.

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.

Effects of arc-ultrasonic on pores distribution and tensile property in TIG welding joints of MGH956 alloy

MGH956, a kind of oxide dispersion strengthened (ODS) alloy, which is considered as candidate structural material for advanced nuclear systems because of its excellent radiation resistance and high-temperature capability. However, pores in fusion welding joints seriously reduced the quality and performance of the joint and structure. Arc-ultrasonic technology was applied in this research in order to prevent pores and improve tensile strength. The results showed that the excitation current of arc-ultrasonic has great effect on the pores distribution and tensile property. When it is increased to 20A or 30A, few pores are in the joint and the tensile strength (about 550MPa) is also improved. When the arc-ultrasonic frequency decreased from 60kHz to 30kHz, bubbles floated outside more easily, the tensile strength is increased to about 543MPa. But arc-ultrasonic has little influence on weld joints microhardness change.

Comparison of Tensile Damage Evolution in Ti6A14V Joints Between Laser Beam Welding and Gas Tungsten Arc Welding

The present paper studied the evolution of tensile damage in joints welded using laser beam welding (LBW) and gas tungsten arc welding (TIG) under a uniaxial tensile load. The damage evolution in the LBW joints and TIG-welded joints was studied by using digital image correlation (DIC) technology and monitoring changes in Young’s modulus during tensile testing. To study the mechanism of void nucleation and growth in the LBW joints and TIG-welded joints, test specimens with various amounts of plastic deformation were analyzed using a scanning electron microscope (SEM). Compared with TIG-welded joints, LBW-welded joints have a finer microstructure and higher microhardness in the fusion zone. The SEM analysis and DIC test results indicated that the critical strain of void nucleation was greater in the LBW-welded joints than in the TIG-welded joints, while the growth rate of voids was lower in the LBW-welded joints than in the TIG-welded joints. Thus, the damage ratio in the LBW joints was lower than that in the TIG-welded joints during tensile testing. This can be due to the coarser martensitic α′ and the application of TC-1 welding rods in the TIG-welded joint.

Strength Evaluation of a Single Layer Passed TIG Weld Joint in Advanced Reduced Activation Alloy by Small Punch Test for HCCR TBM in ITER

Korea has developed a helium-cooled ceramic reflector (HCCR) test blanket module (TBM) for ITER, and Korean reduced activation ferritic martensitic (RAFM) steel, which is named ARAA (advanced reduced activation alloy), has also been developed for a structural material of the KO HCCR TBM. To evaluate the welding fabrication technology in the TBM, one case of TIG welding conditions was selected based on the previous work by Yoon et al. (2013), and a single pass with one side weld procedure through a thickness in TIG weld was carried out using ARAA, Batch 2 (F206). The microstructure was observed in the base, heat affected zone (HAZ), and weld region, and the micro-hardness was measured from the base to the weld region. In addition, a small punch (SP) test considering the base metal and HAZ region was carried out at room and high (550°C) temperatures. The empirical mechanical properties of the HAZ were estimated based on the correlation between the tensile and SP test in the base metal, and the fracture morphology was observed after the SP test.

Tungsten Inert Gas and Friction Stir Welding Characteristics of 4-mm-Thick 2219-T87 Plates at Room Temperature and −196 °C

2219-T87 aluminum alloy is widely used for fabricating liquid rocket propellant storage tank, due to its admirable cryogenic property. Welding is the dominant joining method in the manufacturing process of aerospace components. In this study, the tungsten inert gas welding and friction stir welding (FSW) characteristics of 4-mm-thick 2219-T87 alloy plate at room temperature (25 °C) and deep cryogenic temperature (−196 °C) were investigated by property measurements and microscopy methods. The studied 2219 base alloy exhibits a low strength plane anisotropy and excellent room temperature and cryogenic mechanical properties. The ultimate tensile strength values of TIG and FSW welding joints can reach 265 and 353 MPa at room temperature, and 342 and 438 MPa at −196 °C, respectively. The base metal consists of elongated deformed grains and many nano-scaled θ (Al2Cu) aging precipitates. Fusion zone and heat-affected zone (HAZ) of the TIG joint are characterized by coarsening dendritic grains and equiaxed recrystallized grains, respectively. The FSW-welded joint consists of the weld nugget zone, thermo-mechanically affected zone (TMAZ), and HAZ. In the weld nugget zone, a micro-scaled sub-grain structure is the main microstructure characteristic. The TMAZ and HAZ are both characterized by coarsened aging precipitates and elongated deformed grains. The excellent FSW welding properties are attributed to the preservation of the working structures and homogenous chemical compositions.

Activated flux TIG welding of titanium

Metallurgical characterization and qualification of activated flux TIG (ATIG) weld joints of titanium produced using in-house developed activating flux are presented. The flux formulation was optimized after carrying out trials with different sets of flux powders and subsequent metallographic observation of weld bead profile. ATIG welding of titanium using this flux, with optimized welding parameters, produces full penetration welds in 6-mm-thick plates having weld bead depth-to-width ratio of 1.25 compared to 0.25 of conventional TIG welds. ATIG weld joints were prepared using 6-mm-thick titanium plates using square-butt joint geometry and these joints were qualified by radiography. Root and face bend tests passed 4T bend radius as per American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code-Section IX requirements with bend angle of 180°. Transverse tensile testing of weld joints showed fracture in the weld metal with sufficient ductility and tensile strength of 398 MPa, which was close to the base material tensile strength of 402 MPa thereby meeting ASME Section IX requirements. Uniform hardness across the weld confirmed that the weld was not contaminated by components of flux or atmospheric gases, which can result in increased hardness of the weld metal leading to embrittlement. The corrosion test of the weld joints in 11.5 M boiling nitric acid showed improved corrosion resistance compared to base material.