Tungsten Inert Gas Welding Method Research Articles

Arc heating hot wire assisted arc welding technique for low resistance welding wire

An assistant arc was used to preheat the wire for hot wire tungsten inert gas (TIG) welding which was independent on the resistance of the welding wires and avoided the drawbacks of the traditional hot wire preheating method. The new method is suitable for low resistance wire such as copper and aluminium. The experimental results showed that the wire temperature varied linearly with preheating current and hyperbolically with wire feeding speed. The temperature of wires achieved 60% of their melting points when LF6, H90, HS201 and H08Mn2Si welding wires were used at a current less than 50 A. With arc assisted hot wire, the welding deposition efficiency of the HS201 wire was increased by 96% compared with the traditional TIG welding method, while its microstructure was similar to that of the cold wire welding.

Aluminum alloy tubular columns—Part I: Finite element modeling and test verification

A numerical investigation on fixed-ended aluminum alloy tubular columns of square and rectangular hollow sections is described in this paper. The fixed-ended column tests were conducted that included columns with both ends transversely welded to aluminum end plates using the tungsten inert gas welding method, and columns without welding of end plates. The specimens were extruded from aluminum alloy of 6061-T6 and 6063-T5. The failure modes included local buckling, flexural buckling, interaction of local and flexural buckling, as well as failure in the heat-affected zone (HAZ). An accurate finite element model (FEM) was developed. The initial local and overall geometric imperfections were incorporated in the model. The non-welded and welded material nonlinearities were considered in the analysis. The welded columns were modeled having different HAZ extension at the ends of the column of 25 and 30 mm. The nonlinear FEM was verified against experimental results. It is shown that the calibrated model provides accurate predictions of the experimental loads and failure modes of the tested columns. The load-shortening curves predicted by the finite element analysis are also compared with the test results.

Tests and Design of Aluminum Alloy Compression Members

A test program was performed on aluminum alloy columns of square and rectangular hollow sections that were compressed between fixed ends. In total, five series of tests were conducted that included columns with both ends transversely welded to aluminum end plates using the tungsten inert gas welding method, and columns without welding of end plates. The tests were performed over a range of column lengths in order to obtain a column curve for each series of test. Heat-treated aluminum alloys of 6063-T5 and 6061-T6 material were used for the column specimens. Nonwelded and welded material properties were obtained from various coupon tests. The column specimens failed by local buckling, overall buckling, as well as interaction of local and overall buckling. In addition, some welded columns failed in the heat-affected zone. The test strengths were compared with the design strengths predicted by the American, Australian/New Zealand, and European specifications for aluminum structures. Reliability of the design rules for transversely welded aluminum columns in the three specifications was examined using reliability analysis. It is shown that the design strengths predicted by the three specifications are conservative for the nonwelded columns. For the welded columns, the design strengths predicted by the American and Australian/New Zealand specifications are generally conservative, whereas the design strengths predicted by the European Code are relatively quite conservative. It should be noted that the design strengths predicted by the American and Australian/New Zealand specifications are unconservative in some cases for the welded columns.

Evaluation of welded titanium joints used with cantilevered implant-supported prostheses

Early failure of laser-welded titanium implant frameworks in clinical practice has prompted an investigation of the strength and durability of welded cantilevered titanium sections. The purpose of this study was to determine the effect that the use of filler wire in laser welding of titanium cantilever frameworks had on the flexural strength and fatigue resistance of the welded joints. Sixty titanium implant-supported frameworks with 12-mm cantilevers were fabricated in 4 groups (n=15), using 3 different laser welding protocols with 0, 1, and 2 weld passes with filler wire, and 1 conventional tungsten inert gas welding method. The volume of filler wire used (mean volumes 0, 1.7, 3.4, and 8.3 mm(3)) was determined by measurement of the length of wire before and after welding each joint. Ten frameworks from each group were tested for ultimate flexural strength by loading the cantilevers 10 mm from the abutment. The remaining 5 frameworks from each group were similarly tested under a simulated masticatory load of 200 N until failure, or to 1 million cycles. A 2-way analysis of variance was used to examine the flexural strengths, and log-rank statistics were applied to cyclic test data (alpha=.05). There were significant differences between the 4 groups for ultimate flexural strength (P<.001) and resistance to cyclic loading (P=.002). The volume of filler wire added was a significant predictor of ultimate flexural strength (P=.03), and was a borderline determinant of the number of cycles to failure at 200 N (P=.05). Each laser weld pass with filler wire roughly doubled the ultimate flexural strength and fatigue resistance of the joint relative to the previous weld. Tungsten inert gas welding with efficient argon shielding deposited the most filler wire and produced the strongest and most fatigue-resistant joints. The ultimate flexural strength and fatigue resistance of cantilevered joints in laser-welded titanium prostheses are improved by the use of filler wire. Tungsten inert gas welding with efficient argon shielding can be used in situations when a high-strength joint is required.

Experimental investigation of aluminum alloy circular hollow section columns

This paper presents an experimental investigation of aluminum alloy circular hollow sections subjected to pure axial compression between fixed ends. The specimens were fabricated using 6063-T5 and 6061-T6 heat-treated aluminum alloy. The test program included 29 column tests which were separated into 4 test series of different type of aluminum alloy and cross-section geometry. Each test series contained at least 5 columns with both ends transversely welded to aluminum end plates using the Tungsten Inert Gas welding method, and 2 columns without welding of end plates. Hence, the effects of welding on aluminum alloy columns could be investigated. The specimen length ranged from 300 to 3000 mm in order to obtain a column curve for each test series. The observed failure modes for the column tests include yielding, overall buckling, and material yielding in the heat-affected zone. The test strengths were compared with the design strengths predicted by the American, Australian/New Zealand and European specifications for aluminum structures. The purpose of this paper is to present the test results of aluminum alloy circular hollow section columns with and without transverse welds, and to check the accuracy of the design rules in the current specifications.

Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (II)

Overpack, a high-level radioactive waste package for geological disposal, seals vitrified waste and in line with Japan's waste management program is required to isolate it from contact with groundwater for 1,000 years. In this study, TIG (Tungsten Inert Gas) welding method, a typical arc welding method and widely used in various industries, was examined for its applicability to seal a carbon steel overpack lid with a thickness of 190 mm. Welding conditions and welding parameters were examined for multi-layer welding in a narrow gap for four different groove depths. Weld joint tests were conducted and weld flaws, macro- and microstructure, and mechanical properties were assessed within tentatively applied criteria for weld joints. Measurement and numerical calculation for residual stress were also conducted and the tendency of residual stress distribution was discussed. These test results were compared with the basic requirements of the welding method for overpack which were pointed out in our first report. It is assessed that the TIG welding method has the potential to provide the necessary requirements to complete the final closure of overpack with a maximum thickness of 190 mm.

Long-Term Integrity of Waste Package Final Closure for HLW Geological Disposal, (II) Applicability of TIG Welding Method to Overpack Final Closure

Overpack, a high-level radioactive waste package for geological disposal, seals vitrified waste and in line with Japan's waste management program is required to isolate it from contact with groundwater for 1,000 years. In this study, TIG (Tungsten Inert Gas) welding method, a typical arc welding method and widely used in various industries, was examined for its applicability to seal a carbon steel overpack lid with a thickness of 190 mm. Welding conditions and welding parameters were examined for multi-layer welding in a narrow gap for four different groove depths. Weld joint tests were conducted and weld flaws, macro- and microstructure, and mechanical properties were assessed within tentatively applied criteria for weld joints. Measurement and numerical calculation for residual stress were also conducted and the tendency of residual stress distribution was discussed. These test results were compared with the basic requirements of the welding method for overpack which were pointed out in our first report. It is assessed that the TIG welding method has the potential to provide the necessary requirements to complete the final closure of overpack with a maximum thickness of 190 mm.

Solidification microstructure of plasma sprayed and remelted carbide coatings (Cr3C2/ni-Al, W2C-WC/Co)

Carbide layers applied on the steel substrate by the plasma spraying method were remelted using high-energy heat sources. A diverse methodology of coating treatment was used: ranging from a single and multiple treatment with a continuous micro-plasma arc, through the treatment by the TIG (tungsten inert gas) welding method, to CO2 laser remelting. The quality of the remelted layers was evaluated based on macro- and microscopic structural examinations, x-ray phase analysis, tribological tests, and hardness measurements. The results of the investigations carried out confirmed the possibility of remelting sprayed coatings and obtaining layers free from faults and imperfections typical of plasma spraying. The micro- and x-ray structural examinations revealed, among other things, a significant reduction of porosity (both open and closed ones), homogenization of the chemical composition, smoothing of the surface, and the improvement of coating adhesion to the substrate. The present study is a continuation of the investigations carried out on thermally sprayed and micro-plasma remelted oxide layers, that were started at the beginning of the 1990s at the Material Engineering Institute of the Technical University of Częstochowa.

Re-weldability tests of irradiated austenitic stainless steel by a TIG welding method

Austenitic stainless steel (SS) is widely used for the in-vessel and ex-vessel components of fusion reactors. In particular, SS316L(N)-IG (IG-ITER Grade) is used for the vacuum vessel (VV), pipe lines, blanket modules, branch pipe lines connecting the module coolant system with the manifold and for the other structures of ITER. One of the most important requirements for the VV and the water cooling branch pipelines is the possibility to repair different defects by welding. Those components which may require re-welding should be studied carefully. The SS re-weldability issue has a large impact on the design of in-vessel components, in particular, the design and efficiency of radiation shielding by the modules. Moreover, re-welded components should operate for the lifetime of the reactor. This paper deals with the study of re-weldability of un-irradiated and/or irradiated SS316L(N)-IG and the effect of helium generation on the mechanical properties of the weld joint. Tungsten inert gas (TIG) welding was used for re-welding of the SS.

Reweldability test of irradiated SS316 by the TIG welding method

Stainless steel is a candidate material for the structural material in fusion reactors. Rewelding of irradiated materials will have a large impact on the design and the maintenance of in-vessel components. In the present work, the welding specimens made of type 316 stainless steel were irradiated in JMTR (Japan materials testing reactor) to a fast neutron fluence of ∼2.0 × 10 20 n/cm 2 ( E > 1 MeV) at a temperature of ∼200°C. The rewelding of unirradiated and/or irradiated stainless steel was performed by the tungsten inert gas (TIG) welding method and the weldments of unirradiated and/or irradiated SS316 were characterized by tensile testing (test temp.: 20°C and 200°C), hardness, metallographical observation and SEM/XMA analyses.