Inert Gas Method Research Articles

Microstructural, mechanical and nondestructive characterization of X60 grade steel pipes welded by different processes

Abstract In this paper, the welding quality of API 5L X60 steel pipes was investigated after the application of three different welding scenarios by applying submerged arc welding (SMAW), tungsten inert gas (TIG) and hybrid (TIG + SMAW) welding methods with an average heat input of ca. 1 kJ mm−1 for all passes. For this purpose, the ultrasonic and radiographic tests were done to detect possible discontinuities such as crack and porosity in the welding zones. In addition, the macro and microstructures of weld zones were made to examine different zones in terms of weld quality and phases. Moreover, the hardness, impact toughness and tensile tests were carried out to determine the mechanical properties of the weldments. The tensile strength of the pipe weldments was recorded to be ∼603, 610 and 625 MPa after the welding of pipes by SMAW, TIG + SMAW and TIG welding, respectively. In addition, the impact toughness of the welds was obtained to be 48, 76 and 66 J, for these welding methods, successively. According to the experimental findings, all three welding plans were successfully applied to the steel pipes and found to be suitable regarding the relevant international standards.

Polyethylene deflagration characterization and kinetic mechanism analysis

In this paper, the combustion process of polyethylene (C100H202) was simulated by experiment and Reaction Force Field molecular dynamics (ReaxFF MD) simulation, and the influence of density and temperature on the deflation of C100H202 was investigated. The flame propagation characteristics of C100H202 with different concentrations were studied by the Hartmann experiment system, and the pyrolysis characteristics of C100H202 under N2 and O2 atmospheres were studied by the TG test. The pyrolysis activation energy of C100H202 in N2 and O2 atmospheres is 72.160 kJ/mol and 92.356 kJ/mol, respectively, which is consistent with the reaction activation energy of 97.110 kJ/mol calculated by simulation. In addition, it is found through simulation that the increase in system density will increase the generation and consumption of intermediate products such as C2H4, which explains the phenomenon of more intense detonation when the concentration of C100H202 increases from 0.0002 g/cm3 to 0.0005 g/cm3 in dust ignition experiment from the molecular level. The results show that physical methods such as cooling down and releasing inert gas and chemical methods that consume functional groups have significant effects on the inhibition of hydrocarbon deflagrations from a microscopic point of view, and provide theoretical support for the study of the inhibition of hydrocarbon deflagrations.

Analyzing and modeling of CO purging for high-temperature proton exchange membrane fuel cells

Purging offers a straightforward and cost-effective means of eliminating inert gases that accumulate in high-temperature proton exchange membrane fuel cells (HT-PEMFC) operating in dead-end anode (DEA) mode. Nevertheless, earlier studies primarily concentrated on inert gases, overlooking the significant challenge posed by the strong adsorption of CO within HT-PEMFC, complicating the use of inert gas methods for CO purification. This paper presents an analytical model that was validated experimentally. Leveraging this model, the paper analyzes the crucial parameter of CO concentration within the anode and deduces theoretical extreme values. Subsequently, it proposes purging strategies tailored to different operational conditions. The findings indicate that the minimum CO concentration within HT-PEMFC is influenced by current, feed gas flow rate, and feed gas CO concentration. Additionally, the maximum CO concentration is affected by the off-duration of the purge valve in addition to these factors. Specifically, under the operating condition of 473.15 K, adopting a CO concentration threshold purge strategy is recommended, whereas under the operating condition of 448.15 K, voltage drop and CO concentration threshold purge strategies should be respectively implemented above and below the cutoff line based on the current. This research contributes to mitigating the issue of CO accumulation in DEA mode.

INFLUENCE OF THE ARC WELDING RELATED ELECTROMAGNETIC FIELD ON PACEMAKERS

The patients with implanted pacemaker or cardioverter-defibrillator are exposed to a certain risk of affecting this device by surrounding electromagnetic field. There are many sources of potential risky electromagnetic fields, arc welding is definitely one of them. The aim of this article is to present research focused on analysis of the pacemaker function during welding. There were performed in-vitro measurements with 9 pacemakers during metal inert gas (MIG) and tungsten inert gas (TIG) method arc welding. The responses of pacemakers were monitored by communication via programmer. Based on these measurements there are proposed safe distances from the main parts of welding machines, and also conditions and instructions for arc welding by patients with pacemakers. To ensure patient safety, patients should maintain suggested safe distances, use direct current with minimal possible amplitude, and weld in short intervals. Additionally, their pacemakers should be set to bipolar configuration.

Zinc Electroplated Coating and Post Weld Heat Treatment on Micro Dissimilar Metal Inert Gas Welding

The welding process could reduce the performance of the material both microstructure and mechanical strength. Therefore, handling the welding results was necessary. There are several ways to improve the performance of welded joints, namely heat treatment and coating using electroplating. The materials used were galvanized and stainless steel 201 with a size of 100 x 50 x 0.5 mm. Welding used the Metal Inert Gas (MIG) method, while the filler metal used was AWS ER70S-6. The results of the welding were coated by electroplating, while the post-weld heat treatment was carried out to determine the effect of electroplating and heat treatment on the hardness of the joints. There were three temperature variations namely 250 °C, 300 °C, and 350 °C, and three variations of holding time, namely 30 minutes, 60 minutes, and 90 minutes. The highest value of roughness (116.68 VHN) was obtained from a combination of a temperature of 300 °C and a holding time of 30 minutes. While the lowest hardness value (54.93 HVN) was obtained from a temperature of 300 °C with a holding time of 90 minutes.

Analysis of the effect of welding sequence and speed on the distortion of ASTM A36 joints by MIG method

The welding process with the Metal Inert Gas (MIG) method often produces distortions that are detrimental to product quality, one of the factors that affect the characteristics of the welding results is heat input. The heat input provided in the welding process is influenced by arc current, arc voltage, and welding speed, besides that the welding sequence can also affect the distortion of thin plates due to welding on materials such as ASTM A36 plates. The welding process uses welding wire/electrode type AWS ER 70S-6 with a diameter of 1.0 mm, the welding parameters applied are: voltage of 22 Volts, current of 150 Amperes, DC + Current type (DCEP), the shielding gas used is 100% Argon with a flow rate of 15 liters per minute, horizontal welding position (1G), the amount of heat input is differentiated by changing the welding speed and the welding sequence used is the stepping stone method. The results of the study using ANOVA indicate that welding distortion increases with an increase in input heat, the repetition of welding sequences leads to greater distortion due to thermal stress, and the welding sequence and input heat have an influence of 80.4% in reducing distortion.

A novel high-efficiency solar thermochemical cycle for fuel production based on chemical-looping cycle oxygen removal

Solar-driven two-step thermochemical cycling is a promising means to convert solar energy into storable and transportable chemical fuel, in which hydrogen or carbon monoxide is generated by continuous reduction and oxidation reactions. However, the high energy consumption of deoxygenation in the reduction step is an important factor restricting its efficiency improvement. In this work, we propose a fuel production system with thermochemical cycles coupled with chemical-looping cycles, which uses the chemical-looping cycle oxidation reaction at relatively low temperature to absorb the oxygen produced by the thermochemical cycle reduction reaction. The oxygen-carriers in the chemical-looping cycle can be reduced by adding reductants or direct heating with waste heat from the thermochemical cycle. The coupled system can remove the oxygen in the thermochemical cycle reduction reaction and reduce the energy consumption in this process. In addition to the hydrogen production, waste heat from the thermochemical cycle can also be used in the chemical-looping cycle to generate extra electricity. Theoretical calculation results show that in the oxidation temperature range of 900–1100 °C, the energy consumption for separating oxygen from inert gas after sweeping in the traditional thermochemical cycle accounts for 30–57% of the total energy consumption, while the chemical-looping cycle part in the coupled system accounts for 26–36%. The coupled system can improve the solar-to-fuel efficiency by 45.9% to 20.9% and improve the solar-to-electricity efficiency by 104.1% to 14.6% without heat recovery compared to traditional thermochemical cycles when the reduction temperature is 1500 °C. Under the conditions of 20% solid-state heat recovery and 90% gas-state heat recovery, the coupled system achieves a solar-to-fuel efficiency of 28.1%. In addition, we also put forward a vacuum pump, inert gas and chemical-looping cycles combined oxygen removal method. Since the vacuum pump has high efficiency and fast deoxygenation speed in the low vacuum interval, the system efficiency can be further improved. Our research can provide a new solution to the high energy consumption of deoxygenation in thermochemical cycles.

Tension and Impact Analysis of Tungsten Inert Gas Welded Al6061-SiC Composite

An aluminum 6061 (Al6061) metal matrix composite (MMC) reinforced with silicon carbide was prepared by stir casting. Specimens of the required dimensions were welded using the tungsten inert gas (TIG) method. ER5356 (Al-5%Mg) was chosen as the appropriate filler material for TIG welding. The input current parameter was varied (150, 170 and 200nA) while maintaining the other welding parameters at constant values. An assessment of the mechanical (tensile and impact strength) and microstructure properties of the TIG-welded Al6061 MMC with 6 wt. % silicon carbide particles was accomplished. An 8.27% improvement was observed in ultimate tensile strength (UTS) for the 150 A TIG-welded sample. UTS and elasticity decreased linearly with an increase in welding current but exhibited higher values than in non-welded specimens. The microstructural analysis of the welded MMCs showed a mixed mode of failure, with equiaxial dimples being dominant in lower-weld-current specimens. Compared to non-welded specimens, a 40% increase in impact strength was observed for the 150 A TIG-welded specimens, which decreased with an increase in the welding current value. SEM analysis revealed ductile striations and continuous river patterns, resulting in mixed failure.

The Effect of Shot Peening on Residual Stress and Surface Roughness of AMS 5504 Stainless Steel Joints Welded Using the TIG Method.

This article presents the influence of the Shot Peening (SP) process on residual stress and surface roughness of AMS 5504 joints welded using the Tungsten Inert Gas (TIG) method. Thin-walled steel structures are widely used in the aviation and automotive industries, among others. Unfortunately, the fatigue properties become worse during the welding process. Samples of 1 mm-thick AMS 5504 steel plates were first prepared using TIG welding and then strengthened by the Shot Peening (SP) process. The technological parameters of the SP process were changed in the range of time t from 2 min to 4 min and of pressure p from 0.4 MPa to 0.6 Mpa. The residual stresses were measured by X-ray diffraction in three zones: fusion zone (FZ), heat-affected zone (HAZ) and base metal (BM). The results showed that SP introduced compressive residual stresses in all of the zones measured, especially in the FZ. The greatest value of compressive residual stresses σ = -609 MPa in the FZ was observed for the maximum parameters of SP (p = 0.6 MPa, t = 4 min). The increase in value of residual stress is about 580% when compared to welding specimens without treatment. As a result of shot peening in the FZ, the mean roughness value Ra decreased in range 63.07% to 77.67% in the FZ, while in the BM increased in range 236.87% to 352.78% in comparison to specimen without treatment. Selected surface roughness parameters in FZ and BM were analyzed using neural networks. In FZ, it was demonstrated that the most correlated parameters with residual stresses are Rt and Rsk. On the other hand, in the BM zone, the most correlated parameters were Rv, Rt and Rq. This enables the estimation of stresses in the welded joint after SP on the basis of selected roughness parameters.

Mechanical and Micrography Analysis of Armour Plate Weldment Using Tungsten Inert Gas and Oxy-Acetylene Welding Methods

Defence Industries Corporation of Nigeria (DICON) has compared the effect of Tungsten Inert Gas (TIG) and Oxy-Acetylene welding methods on microstructural and some mechanical properties of Armour plate for the modification of military troop carriers. The optical emission spectrometer (OES) at DICON was used to analyse the chemical composition of the armour plate strip. It was then machined and cut to various test piece dimensions for both welding processes, following which the weldment samples were subjected to post-weld mechanical tests (tensile, impact, and hardness) and metallographic examination. The samples were then welded according to the procedure outlined in this study. The fundamental composition of armour plates was preserved in the samples. When compared to Oxy-Acetylene (OA) welding, Tungsten Inert Gas (TIG) welding produced better results, with an average ultimate strength (UTS) of 603.52 MPa and an impact strength of 10.53 J. In addition, the TIG analysis hardness strength for the source material, heat affected zone (HAZ), and weldment sample is 510.3, 502, and 511-HV, respectively. At x200 magnification, the micrography of the TIG weldment revealed a small coarse grain size of ferrite and larger areas of pearlite.

The Phenomena and Criteria Determining the Cracking Susceptibility of Repair Padding Welds of the Inconel 713C Nickel Alloy.

The creep-resistant casting nickel alloys (e.g., Inconel 713C) belong to the group of difficult-to-weld materials that are using for precise element production; e.g., aircraft engines. In precision castings composed of these alloys, some surface defects can be observed, especially in the form of surface discontinuities. These defects disqualify the castings for use. In this paper, the results of technological tests of remelting and surfacing by the Tungsten Inert Gas method (TIG) in an argon shield and TecLine 8910 gas mixture are presented for stationary parts of aircraft engines cast from Inconel 713C alloy. Based on the results of metallographic studies, it was found that the main problem during remelting and pad welding of Inconel 713C castings was the appearance of hot microcracks. This type of defect was initiated in the partial melting zone, and propagated to the heat affected zone (HAZ) subsequently. The transvarestraint test was performed to determine the hot-cracking criteria. The results of these tests indicated that under the conditions of variable deformation during the remelting and pad welding process, the high-temperature brittleness range (HTBR) was equal 246 °C, and it was between 1053 °C and 1299 °C. In this range, the Inconel 713C was prone to hot cracking. The maximum deformation for which the material was resistant to hot cracking was equal to 0.3%. The critical strain speed (CSS) of 1.71 1/s, and the critical strain rate for temperature drop (CST), which in this case was 0.0055 1/°C, should be used as a criteria for assessing the tendency for hot cracking of the Inconel 713C alloy in the HTBR. The developed technological guidelines and hot-cracking criteria can be used to repair Inconel 713C precision castings or modify their surfaces using welding processes.

A Cooks Distance Approach to Control the Haz and Arc Length of Tig Mild Steel Weld

The heat affected zone and arc length parameters have a vital role to play in determining the integrity of a weld structure. The cooks distance is a statistical diagnostic employed in this study to select the best optimum combination of welding process parameters. Mild steel plate was the choice material used to produce the weld specimen, which was welded with the Tungsten inert gas method. The RSM model was used to develop an optimal solution that can explain the behavior of the welded joint with respect to the heat affected zone and arc length, different diagnostic techniques were employed which includes the normal probability plot and cooks distance plot. The model developed has sufficient merit as the results obtained shows that the cooks distance values is within the range of 0 and 1 indicating the absence of outlier in the data making the optimal solution highly acceptable.

A Cooks Distance Approach to Control the Haz and Arc Length of Tig Mild Steel Weld

The heat affected zone and arc length parameters have a vital role to play in determining the integrity of a weld structure. The cooks distance is a statistical diagnostic employed in this study to select the best optimum combination of welding process parameters. Mild steel plate was the choice material used to produce the weld specimen, which was welded with the Tungsten inert gas method. The RSM model was used to develop an optimal solution that can explain the behavior of the welded joint with respect to the heat affected zone and arc length, different diagnostic techniques were employed which includes the normal probability plot and cooks distance plot. The model developed has sufficient merit as the results obtained shows that the cooks distance values is within the range of 0 and 1 indicating the absence of outlier in the data making the optimal solution highly acceptable.

Effect of Magnetic Field Induce Arc in Autogenous TIG Welding of 304 Stainless Steel Butt Joint

This paper reports the use of External Magnetic Field-Tungsten Inert Gas (EMF-TIG) method in butt joint applications to determine the effect of welding arc compression on the quality of butt joint of SS 304 thin plate was reported. The welding process was performed without using filler or autogenous welds. The external magnetic field was generated by placing a magnetic solenoid around the TIG welding torch. The results of this study showed that EMF-TIG welding can produce a more uniform bead width along the weld line compare with conventional TIG. Moreover, the D/W ratio obtained under external magnetic field was higher than without magnetic. However, the tensile strength of butt joint decreased with EMF-TIG because there is constriction in arc welding which produces shrinkage weld pool volume. In addition, high welding speeds result in a decrease in the tensile strength of both conventional TIG and EMF-TIG welds.

Microstructural Characterization of Ni-Based B4C Reinforced Composite Coating Produced by Tungsten Inert Gas Method

Microstructural Characterization of Ni-Based B4C Reinforced Composite Coating Produced by Tungsten Inert Gas Method

Investigation of forming limit curves and mechanical properties of 316 stainless steel/St37 steel tailor-welded blanks produced by tungsten inert gas and friction stir welding method

The conventional welding method for joining dissimilar steels is the manual tungsten inert gas (TIG) method. Nevertheless, recently the benefits of solid state welding have been attracted attention of industrial manufacturers. In this article, TIG and friction stir welding method are compared based on the formability and mechanical properties of the welded sheets. Experimental evaluation of mechanical properties and forming limit curves have been carried out using uniaxial tensile test and Nakazima test, respectively. Results of experimental tests illustrated that formability of friction stir welded sheets was about 38% higher than the TIG-welded sheets. The microstructure analysis of TIG welded blanks revealed that grain growth in the heat-affected zone on the St37 steel, reduced the formability of welded joints in this method. Finite element simulation was used to estimate the forming limit diagram of the joints without considering the effects of welding heat on the material properties. The difference between the results of the FSW and finite element simulations was about 6%. While in the TIG welded blanks formability reduces significantly and difference between the result of experiment and simulation is about 33%. These results show that friction stir welding could more effectively preserve the sheets' formability after welding.

Microstructural Properties of Fe–Cr–C/NbC Composite Coating Produced on Medium Carbon Steel Surface by TIG Coating Process

In this study, Fe-based composite coatings were produced on a medium carbon steel surface by the Tungsten inert gas method. The microstructure and phase structure of the coatings were analyzed by an optical microscope with clemex image analysis, scanning electron microscope equipped with an energy-dispersive spectroscopy and X-ray diffractometer. The results show that the coating is metallurgically bonded to the substrate when it is produced with sufficient energy input. In the microstructure of Fe–Cr–C coatings, hexagonal-shaped M7C3 carbides solidified in γ-(Fe,Cr) eutectic matrix, while in Fe–Cr–C/NbC composite coatings, quadrangular-shaped NbC carbides solidified. As the amount of FeNb melted increased, the amount of NbC in the structure increased.

Effect of welding parameters on microstructure and mechanical properties of AA7075/AA5182 alloys joined by TIG and MIG welding methods

In this study, V and X welding grooves were opened to the forehead positions of the AA5182 and AA7075 aluminum alloy pairs and these alloy pairs were joined with tungsten inert gas (TIG) and metal inert gas (MIG) methods. Three different welding currents were used in joints. Gas flow rates of 12 and 17 l/min at the TIG welding and wire feed rates of 38 and 45 cm/min at MIG welding were selected. The effect of the welding grooves, welding current, gas flow rate and wire feed rate on microstructure and mechanical properties were investigated. Microstructures of welding zones were analyzed by an optical microscope and a scanning electron microscope (SEM). Vickers hardness of these zones was also measured. In addition, tensile and fatigue tests were carried out. Fracture mechanisms of failed specimens were conducted after the tensile tests were examined by using SEM. The highest hardness, tensile and fatigue strengths were obtained from the alloy pairs joined by opening X welding groove with TIG welding method. These values were 89 HV, 262.87 MPa, and 131.5 MPa, respectively. Similarly, the lowest tensile and fatigue strengths were obtained from the alloy pairs joined by opening V welding groove in the TIG welding method. These values were, respectively, 94.48 MPa and 19.1 MPa. However, the minimum hardness value was measured as 58 HV from the alloy pairs joined by opening V welding groove with MIG welding methods. In addition, it was observed on the fracture surfaces that the grain distributions and mechanisms differed depending on the welding methods, welding groove, and welding parameters.

Wear Characteristics of Hardfacing Coatings Obtained by Tungsten Inert Gas Method

Wear Characteristics of Hardfacing Coatings Obtained by Tungsten Inert Gas Method

Analysis of temperature and column variation in gas chromatography to dead time of inert gas and n-alkane homologous series using randomized block design

The dead time behavior from several inert gas and mathematical methods under temperature and column variation have been studied using randomized block design. Dead time of inert gas and mathematical dead time calculated using n-alkane homologous series that measurement with gas chromatography at temperatures of 60, 90 and 120°C and columns of PS-255, OV-11, CPSIL-5CB, HP -5 and HP-INNOWAX were used as a set data in randomized block design. The results showed that temperature variation affects all dead time values, either for inert gas dead time or mathematical method, except for Parcher method. Different column types between capillary and packed column exhibits a significant effect. For capillary column, all dead time values, either for inert gas dead time or mathematical method is not affected by polarity variation, but they are affected by the column length. Meanwhile for packed column, column length does not affect the mathematical dead time of Ne and He gases, but it affects the dead time of O2 and Ar gases. Parcher method exhibits the best result with a robust dead time, without significant effect in statistics by the change of temperature and column.