Manual TIG Welding Research Articles

Microstructure and mechanical properties of welds at keyhole closures in variable-polarity plasma arc aluminum welding

The variable-polarity plasma arc (VPPA) keyhole welding technology offers an efficient solution for producing defect-free aluminum alloys, but a keyhole is left at the end of the welding process. Traditional manual TIG welding, which involves filling keyholes, often lacks productivity and can result in inconsistent weld quality, hindering the production of high-strength and high-precision parts. In this study, a keyhole self-closing method was proposed, and the microstructure and mechanical properties of keyholes closed by the proposed method were compared to those closed by manual TIG welding. The results showed that the self-closed keyhole had a smaller fusion line wide, and the weld zone had a uniform distribution of equiaxed crystal, with fewer pore defects. While the manual TIG welding-filled keyhole had a higher density of dislocations, which leads to an increase in the microhardness. The presence of pores in the manual TIG welding-filled keyhole reduces its tensile strength and elongation, which were lower than those of the self-closed keyhole by 61.5 MPa and 5.8 %, respectively. The self-closing method can effectively address the keyhole retention issue in VPPA keyhole welding. By using this method, higher-quality welds with better microstructure and mechanical properties can be produced, which can have important implications for various industrial applications, and in applications where mechanical properties are critical.

TENSILE, IMPACT AND NON-DESTRUCTIVE ANALYSIS OF 316 L STAINLESS STEEL FOR MARINE APPLICATIONS

Welding is an age-old method used for joining the metals permanently. The marine industry is a major user of sheet metal components that benefit from custom welded blanks (TWBs). These advantages encompass weight, cost, and noise savings, as well as increases in crash safety, improved efficacy, and oxidation resistance. However, machinability issues are prevalent as a result of the welding process. These benefits and drawbacks are explored, as well as TWB forming techniques, welding procedures, and materials utilized in the marine sector. In this study two different thickness 316L stainless steel grade plate welded using manual and automatic TIG Welding process. The process parameters are chosen for this study is welding current, voltage, welding speed, shielding gas & filler diameter. The manual TIG welded specimen was than compared with automatic TIG welded specimen in terms of Liquid Penetration test, tensile and impact test. The result and discussion are briefly explored.

Numerical and experimental investigation on distribution of residual stress and the influence of heat treatment in multi-pass dissimilar welded rotor joint of alloy 617/10Cr steel

In the present study, numerical and experimental investigation of stress distribution pattern has been performed for thick walled nuclear rotor pipe joint of Alloy 617 and 10Cr steel. Hot wire Tungsten Inert Gas (HW-TIG) welding process has been adopted for multipass narrow groove welding since it yields better mechanical properties at low heat input than manual TIG welding and decreases the accumulation of residual stress significantly. The residual stress generated at the surface of the welded joint was evaluated experimentally using the Blind hole drilling technique (BHD), and consequently, the distribution of stresses along the thickness of the welded joint was masured using the Deep hole drilling (DHD) method. According to the findings, shrinkage at the HAZ area of the weld influences the stresses generated at the cylinder outer surface. The distribution of residual stresses in the weld region is driven mostly by the bending effect produced during the welding process. The influence of post weld heat treatment (PWHT) on residual stress distribution has also been investigated using both experimental and numerical approaches. Numerical investigations have been performed using ABAQUS finite element method. A 2D finite element model has been developed to simulate the welding process and the subsequent heat treatment, using coupled thermo-mechanical analysis. The residual stress results obtained from the numerical approach were validated with the experimentally obtained results and a good correlation has been found. The lumped pass model along with an equal density heat source has been implemented to minimize the computation complexity without affecting the accuracy of the simulated results. The obtained findings revealed that apart from weld centerline, hoop tensile residual stresses were higher around the buttered layer of Alloy 617 and 10Cr steel in an as-welded state. It has been found that nearly 80% of the stresses generated along the weld section have been released after PWHT.

Fatigue life assessment of the structure with widespread damage exposed to high temperature

The exhaust nozzle represents a part of a jet engine which is crucial to its overall performance, since it accelerates the flow of hot gases out of the engine and creates a thrust. During its long service, it is exposed to elevated temperatures and high compressive and hoop stresses, which makes the cracks’ occurrence in the exhaust nozzle’s inner sleeve almost unavoidable. The aim of this paper is to analyze and numerically estimate the fatigue life of inner sleeve in the presence of widespread damage. When damage is detected, two repair methods are employed: welding of single cracks (manual TIG welding) and the use of welded patches. Using numerical simulations based on extended finite element method (XFEM) and finite element method (FEM), fatigue life of repaired inner sleeves were estimated. Based on the comparison of the results obtained in simulations, it was shown that the repair method with welded patches provides longer fatigue life of widespread damaged nozzle than the other with welding of cracks.

Research on Automatic TIG Root Welding of Low Temperature Carbon Steel and Stainless Steel Pipeline for LNG Module Construction

We investigated the application of automatic TIG welding for LNG process pipeline in Yamal LNG module construction project. The study achieved efficient automatic TIG welding of low temperature carbon steel and stainless steel pipeline in root welding and hot welding. The properties of the weld meet the requirements of project technical specification and standard ASME B31.3. Welding efficiency increases 2 times compared with conventional manual TIG welding in root welding and hot welding. Therefore, the construction quality and progress of the project are improved.

Research on Metallurgic Active Precursors

The paper presents the current state of researches carried out in order to improve homogeneity of mixtures for metallic powders; our priority is those with different participation in the mixture, by mechanical alloying. Mixtures of this type are used in the production of welding and related materials.Recently, research has been done to improve deposited metal properties by welding with coated electrodes, by depositing nanostructures, with uncertain results due to the low degree of homogeneity of blends involved in the electrode coating.The performance enhancement method for coated rods, developed by introducing in their coat activating precursors, used for brazing, is well known. The solution to improve the degree of homogeneity of alloying systems by mechanical alloying has been successfully applied for the manufacture of coated electrodes and those tubular with a composite core which are deposited by manual welding or TIG welding, type Fe25% Cr-4% W-V-Ti-La. The grouping of powder components for mechanical alloying was done in such a way that, finally, we have groups with the granulation, respectively specific weight, close and a low potential of segregation.The method of mechanical alloying of the components was used in the manufacture of coated rods in order to improve the fluidity of silver-rich buffer layers deposited in order to favor the diffusion phenomena of brazing alloys in the base materials.Testing the homogeneity of the alloying systems was performed indirectly by metallographic analysis and sclerometric tests.

Dissimilar TIG Welding of HSLA to Austenitic High-Mn TRIP Steels

Abstract The microstructure and mechanical properties of dissimilar butt-joints of high-strength low-alloy steel to austenitic high Mn TRIP steels produced by manual TIG welding with AISI 309L filler metal were investigated. The heat input was varied by changing the welding current between 40 and 70 A. A fully austenitic microstructure with nearly equiaxed grains and without any iron/manganese carbide is observed in the high Mn TRIP base metal, whereas polygonal ferrite and pearlite colonies oriented along the rolling direction are found in the high-strength low-alloy steel base metal. Coarse and refined heat-affected zones (HAZ) were observed in the high-strength low-alloy steel, whereas no significant HAZ was detected at the TRIP side. Bainite and/or martensite grew in the coarse HAZ of the high-strength low-alloy steel steel joined with highest current. The weld seam was formed by austenitic dendrites with interdendritic ferrite and martensite. The best welding condition was achieved with an intermediate current of 50 A, where the hardness transition was smooth, fracture occurred in the HSLA base metal and the joint ductility was higher.

Measurement of the thermal cycle in the base metal heat affected zone of cast ATI®718PlusTM during manual multi-pass TIG welding

This paper presents a method to acquire thermal data in the base metal heat affected zone (HAZ) during manual multi-pass TIG welding of ATI®718PlusTM, representing conditions close to an actual repair welding operation. Thermocouples were mounted in different locations along side walls of linear grooves to record temperature data. The thermal cycling was found to be largely independent of location within the HAZ. The recorded temperatures were below the incipient laves melting temperature, indicating that the current test setup requires optimisation to study HAZ liquation. Based on the results of this study, a modified thermocouple mounting technique is proposed.

Technological Aspects Regarding Manual Metal Arc Welding Using Pulsed Current for Fillet Joints Applications

The idea of using electrical pulse current at manual arc welding with coated electrode starts from the observation of frequency influence, unchanging in manual TIG welding with filler materials, on weld pool volume, by partial solidification of the weld pool in base time of the pulse current, thus being able to control its volume.This paper presents for the first time this new challenge of inverter modern sources: manual metal arc welding using pulsed current.Experimental research findings highlight the technological aspects when using pulsed current in manual metal arc welding, using STEL welding equipment that has this option. The application - concerns the establishment the lack of fusion welded joints in fillet positions. It highlights the beneficial effect of pulsed current, in particular by the joint penetration.Experiments have pursued highlighting of welding pulsed current and frequency of the pulses by the appearance of the joint and the influence by weld geometry for lack of fusion fillet joint. Also, the influence of frequency pulsed current by arc stability, sprays, etc. compared with standard welding was observed.

Investigation of effect of post weld heat treatment conditions on residual stress for ITER blanket shield blocks

The blanket shield block (SB) shall be required the tight tolerance because SB interfaces with many components, such as flexible support keypads, First Wall (FW) support contact surfaces, FW central bolt, electrical strap contact surfaces and attachment inserts for both FW and Vacuum Vessel (VV). In order to fulfil the tight tolerance requirement, stress relieving shall be performed for dimensional stability after cover welding operation.In this paper, effect of Post Weld Heat Treatment (PWHT) conditions, temperature and holding time, was investigated on the residual stress and hardness. The 316L Stainless Steel (SS) was prepared and welded by manual TIG welding by using filler material with 2.4mm of diameter. Welded 316L SS plate was machined to prepare the specimen for PWHT. PWHT was implemented at 250, 300, 400°C for 2 and 3h (400°C only) and residual stress after relaxation were determined. The evaluation of residual stress and hardness for each specimen was carried out by instrumented indentation technique. The residual stress and hardness were decreased with increasing the heat treatment temperature and holding time.

Weldability of Superalloys Hastelloy X by Yb: YAG Laser

Hastelloy X is a commercially available nickel-chromium-molybdenum superalloy with a good oxidation resistance, a good mechanical properties at high temperature and a significant formability; sine qua criteria for the choice of materials for the production of chambers turbojet combustion which is part of this study [1]. Arc welding technique is commonly used for the manufacturing of parts but the aeronautical requirements becoming increasingly severe especially in terms of reproducibility of geometry and metallurgical grade fillet weld. Laser welding is a viable method of assembly to meet these new demands by its automation to replace longer term the manual TIG welding. The high power CO2laser is extensively used for practical applications such as cutting and welding laser welding. The CO2laser is very used in the industry with regard to Yb:YAG laser which until now was not rather powerful but this changes. The aim of this study was to evaluate the effect of Yb:YAG laser beam parameters on the microstructure and mechanical properties of the laser beam welded superalloys Hastelloy X to define a field of weldability. The implementation of an experimental design approach is required due to the multitude of input parameters and the complexity of the phenomena involved [2-3].

Weldability of the superalloys Haynes 188 and Hastelloy X by Nd:YAG

The requirements for welded aircraft parts have become increasingly severe, especially in terms of the reproducibility of the geometry and metallurgical grade of the weld bead. Laser welding is a viable method of assembly to meet these new demands, because of automation, to replace the manual TIG welding process. The purpose of this study is to determine the weldability of Hastelloy X and Haynes 188 alloys by the butt welding process with a Nd:YAG laser. To identify the influential parameters of the welding process (laser power, feed rate, focal diameter and flow of gas) while streamlining testing, an experimental design was established with the CORICO software using the graphic correlation method. The position of the focal point was fixed at 1/3 of the thickness of the sheet. The gas flow rate and the power of the beam have a major effect on the mechanical properties and geometry of the weld. The strength of the weld is comparable to that of the base metal. However, there is a significant decrease in the elongation at break of approximately 30%. The first observations of the cross section of the weld by scanning electron microscopy coupled with EBSD analysis show a molten zone presenting dendritic large grains compared to the equiaxed grains of the base metals without a heat affected zone.

Study on the Effect of Homemade Welding Wire Contaning Ni, Cr Elements on the Weldability of Industrial Pure Aluminum

Industrial pure aluminum has been widely used in industry. However, it caused great difficulties in welding process due to its characteristics such as easy oxidation, high thermal conductivity and specific volume, low melting point. In order to overcome this problem, improving the welding quality of industrial pure and reducing the welding defects is of great significance. In this paper, the weldability of 1050A industrial pure aluminum plate (5 mm thick) with HS331, SAl-2, 1050A leftover materials and homemade welding wire with Ni-Cr alloy as four different filler materials was studied by using manual TIG welding. Metallographic test and mechanical performance test were used to assess microstructure and mechanical properties of the resulting welding joint. The results show that the microstructure and mechanical properties of the resulting welding joint with homemade welding wire with Ni-Cr alloy is relatively better than the others, which offers important implication for the improvement of the welding properties of industrial pure aluminum.

INFLUENCE OF STAINLESS STEEL CIRCULAR PIPES WELDING METHODS AND PARAMETERS TO THE PROCESS ACCURACY AND PRODUCTIVITY

This article describes the interacting of AISI 304L stainless steel circular pipes automatic and manual TIG welding method and its parameters to the process accuracy and productivity. Pipe edge preparation described applying seam sequence for manual welding. Length of samples deformation is analyzed and their axial deviation after automatic and manual welding is determined. Basing and measurement principal schemes are presented. The results of measurements are systematized applying appropriate tables with presenting the results analysis. The research is based on experimental results and measurements deleting axial deviation of welded pipes after manual and automatic welding. Looking of best productivity index and welding quality the optimal welding speed and other parameters have been defined experimentally. Further research discusses the possibilities of improvement the productivity index increasing created product and process value. DOI: http://dx.doi.org/10.5755/j01.mech.19.2.4161

Geometric Parameters Optimization Design for Aluminum Alloy Welding Joint Based on Increasing Fatigue Strength

The geometric parameters of the welding joint had an important effect on fatigue strength, so the stress concentration of the typical double sided asymmetric V-notch joint on high speed train was calculated, the relationship between geometric parameters and the stress distribution of the welding joint was analyzed by FEM, also the geometric parameters optimization design of welding joint was proposed. According to theoretical optimization design scheme, the geometric parameters optimization adopted shaping the weld joint by manual TIG welding and processing circle arc on weld toes by milling respectively,. and the fatigue property of the welding joint optimized by different methods was tested. By comparing the experimental results, it was found that manual TIG welding was difficult to obtain the favorable weld toe angle to decrease the stress concentration, and the welding joint was softened obviously. Accordingly, it revealed that the fatigue property was lower than that of initial joint in fatigue testing. On the contrary, the radius of the weld toes circle arc can be controlled accurately by mechanical processing. The stress concentration was reduced obviously by rounding off the weld toe, as a result the fatigue strength of the welding joint could be increased remarkably. Keywords: A7N01, optimization design, geometric parameters of welding joint, FEM

The effect of PURGING GAS on 308L TIG root pass FERRITE CONTENT

Argon is commonly used as root shielding gas in TIG-welding of stainless steels. As argon world-wide is in short supply and prices are rising, it is of interest to investigate what effects changing to alternative root shielding gases might have on weld metal microstructure. Manual TIG welding was used for root and hot pass welding in 304L pipe and plate material using Ar2 as shielding gas and Ar2, N2+10%H2 or N2 as root shielding gas. A significant increase in the nitrogen content of root beads was found when changing the root shielding gas from pure argon to a nitrogen-rich gas. Typically the root bead nitrogen content increased from 500–600 ppm for argon shielding to 1 100 ppm with nitrogen as root shielding gas. As a result the ferrite content decreased with up to 5 FN from about 8–9 FN to 3–5 FN. However, no indication of hot cracking was found and all root beads solidified as predicted by the WRC-92 diagram with ferrite as the leading phase. It is suggested that typical 304L steel and 308L consumable compositions will permit use of nitrogen-rich gases for root shielding without a significantly increased risk of hot cracking. However, the increased nitrogen level must be considered in the choice of steel and consumable. It is advised to use the WRC-92 diagram to make sure there is sufficient safety margin for actual compositions and, if possible, check root bead ferrite content.

Corrosion of Zircaloy-4 and its welds in nitric acid medium

Zirconium and its alloys are considered as candidate materials for various applications in spent nuclear fuel reprocessing plants involving nitric acid of various concentrations at different temperatures. In the present work an attempt was made to study the corrosion behaviour of Zircaloy-4 (Zr-with Sn-1.5%, Fe-0.22%, Cr-0.1%) in wrought and welded forms in comparison with other candidate materials like commercially pure Titanium (CP-Ti), Ti–5%Ta and Ti–5%Ta–2%Nb. Manual TIG welding and electron beam welding was carried out with Zircaloy-4 pipes of 5 mm thick and 120 mm diameter, and radiography was made for choosing defect-free regions for making samples for corrosion investigations. Three phase corrosion testing in liquid, vapour and condensate regions was conducted in boiling 11.5 M nitric acid medium using a specially designed experimental set up. The results indicated that Zircaloy-4 exhibit superior corrosion resistance in both wrought and welded conditions in comparison with other materials. The electron beam welded samples did not show any deterioration and performed similar to wrought alloy. The detailed results of microstructure, microhardness, corrosion rate, morphology of attack and nature of surface film formed are presented in this paper. The results of the present investigation indicated that Zircaloy-4 could be a candidate material for nitric acid medium of high concentration and temperature in reprocessing plants and other industries.

Metallographic investigations of the heat-affected zone II/parent metal interface cracking in 18Ni maraging steel welded structures

During the fabrication of a large diameter pressure vessel out of 18 Ni maraging steel by manual TIG welding, microcracks were noticed at the heat-affected zone (HAZ)/parent metal interface. The location of these cracks was very different from those reported at the fusion zone/HAZ I interface due to “constitutional liquation”. Extensive optical metallography, scanning electron microscopy and energy dispersive X-ray analyses were carried out to identify the cause for the occurrence of these cracks. It is inferred from the experimental results that the microsegregation of titanium and nickel due to repeated thermal cycling during multipass welding led to the formation of TiC/Ti(CN) and stable austenite film on the grain boundaries. Under severe thermal stresses developed during welding, microvoids generated at the interface of TiC/Ti(CN) inclusions and austenite and further propagated intergranularly due to the premature failure of the austenite films.