Papers by Keyword: GMAW

Abstract: Geopolymer is an alkali-activated aluminosilicate material that combine ceramic-like thermal performance with low thermal conductivity, high-temperature resistance, while remaining castable and structurally adaptable. It is synthesized from calcined kaolin (metakaolin) and fly ash, which react with alkaline solutions to form strong covalent bonds through geopolymerization. This material offers a viable alternative to conventional refractories and imported ceramic products.In this study, a geopolymer material was developed for welding applications and utilized as a weld backing strip for gas metal arc welding (GMAW) of ASTM A36 carbon steel. Weld backing strips are essential for achieving full penetration and consistent root quality in large-scale steel fabrication, particularly in structural, shipbuilding, and heavy industrial construction. The geopolymer binder consisted of 35 wt% metakaolin, 15 wt% fly ash, and a 1:1 ratio of 10 M NaOH and sodium silicate solution. To enhance thermal resistance, river sand, fine glass powder, or recycled SAW flux was incorporated as an external solid phase. Geopolymer specimens were thermally cured and fired at 500 °C to eliminate moisture and organic. Moreover, it was heated to 900 °C to simulate welding heat exposure. Microstructural, mineralogical, and functional group transformations were evaluated using XRD, SEM, and FTIR, while mechanical strength, thermal conductivity, and density were also assessed. The results indicated that glass-enhanced geopolymer exhibited the lowest thermal conductivity (0.89 W/m·K) and highest compressive strength retention after firing, owing to its partial crystallinity and preserved amorphous phase. Flux-based composites showed extensive ceramic phase formation, while sand-based composites retained high thermal conductivity and suffered severe strength loss. Welding trials confirmed that geopolymer backings effectively supported root bead formation with no cracking.

Abstract: Automation of welding with robotic arms has become an inevitable trend in modern manufacturing technologies. This process can be automated by using a "click and go" in which the robot will weld a line where the spot is described or by using an in-line tracking algorithm in which the robot will choose the spot where to weld the line in each layer. This paper presents a simple methodology for the reconstruction of the weld joint and the classification of the joint geometry to serve as a first step to the automatic determination of the robot trajectory. The weld joint has been reconstructed using a laser profilometer placed as a tool on the robot. Spurious data has been removed by signal processing. The joint has been reconstructed three-dimensionally. The classification of the joint profiles was generated using an algorithm based on signal processing and artificial intelligence. This algorithm has been tested for the classification of V-joints (bevel-bevel) and single bevel joints.

Abstract: This paper will discuss the effect of welding variables on the transverse tensile strength and hardness of mild steel welding made by GMAW. The welding variables included are base metal thickness, welding voltage, wire feed speed (WFS), and base metal groove shape. The results show that higher welding transverse tensile strength has obtained higher FZ hardness, while they both increased with decreased welding heat input. E.g., the highest tensile strength (238 MPa) has shown 2162 HV at 768 J/mm heat input, while the lowest tensile strength (120 MPa) of welding made at 2376 J/mm has shown 2108 HV. The FZ of welding made at V groove-shaped base metal has higher hardness and transverse tensile strength, as shown 2159.5 HV and 215 MPa in order when compared to 177 MPa and 2147 HV for X groove-shaped. The hardness at V groove-shaped FZ had an average of 2159.5 HV, while the hardness at X groove-shaped had an average of 2147 HV at 10 mm base metal thickness. The increased hardness of V groove-shaped FZ could be related to the increased stresses at V groove-shaped due to interpass heat input. The intricate physical shape of FZ and HAZ for X groove configuration possibly contributes to the lower transverse tensile strength of welding. A favorably increased hardness and transverse tensile strength are associated with softer and finer ferritic and perlitic grains in FZ and less dendritic perlite structure in HAZ. The Widmanstatten ferrite has contributed to decreased tensile strength.

Abstract: This research is focused on the effect of welding parameter conditions, using Gas Metal Arc Welding, on the macrostructure, mechanical properties, and quality of dissimilar steel weld joints. In this study, the selected joints were low carbon steel (AISI 1015) and austenitic stainless steel (304L SS). The welding current used had three different variations, such as 100, 110, and 120 A. The solid wire electrode used was ER70S6, with a diameter of 1.2 mm. Identification of the macrostructure in the heat-affected zone (HAZ), micro-Vickers hardness, and tensile tests carried out for each GMAW joint specimen. The results were then discussed. The macrostructure of dissimilar steel welded joints at a welding current of 100 A produced a good quality of welded joints and penetration compared to those using welding currents of 110 and 120 A, which had excessive penetration and caused distortion and deformation. The microhardness of the weld metal area was far higher than in other areas. At the current 100 A, the micro-Vickers hardness value of stainless steel 304L SS closing the heat-affected zone (HAZ) had increased from 209 to 226 HV. Likewise, For the welding current of 110 A, the micro-Vickers hardness value rose from 249 to 259 HV, and for the welding current of 120 A, the hardness increased from 225 to 227 HV. In the weld metal area, micro-Vickers hardness for each welding current was 318, 364, and 366 HV, while in the low carbon steel area, the hardness value decreased significantly to 180, 190, and 196 HV. At the current of 100 A, the lowest tensile strength was 359.28 MPa, and yield strength was 303.82 MPa. The tensile strength and yield strength for the current of 110 A were 367.24 MPa and 309.83 MPa, respectively. Meanwhile, at the current of 120A, the tensile strength was at the highest that is 374.86 MPa, and the yield strength value was 315.67 MPa. This study found that the dissimilar steel welded joints experienced an increase in the hardness value of the weld metal, and the tensile test results show that the welded steel joints fractured in the low carbon steel area.

Abstract: Reproducibility in respect to welded structures realization is one of the main requirements for a wide variety of industrial applications. One of the international tendencies regarding the use of the steel is the replacing, in critical areas, of structural steels with high performance steel, e.g. with HSLA steels. The paper presents the results of a factorial designed experimental program focused on determining mathematical correlations between the GMAW process parameters for T joints of 4mm thick steel plates of structural (S235JR+AR according to SR EN 10025-2) and hot-rolled, high-strength low-alloy (HSLA) steel plates (S420MC according to EN 10025-4), respectively. A comparison between the obtained mathematical correlations that connect the welding parameters and the main mechanical characteristics is presented. The correlations can be used for applying the optimal combination of welding process parameters for realizing the T-joints of welded products.

Abstract: In all industrial fields, the product requirements are more and more demanding. HSLA steels are designed to provide higher atmospheric corrosion resistance and improved mechanical properties than structural steels. The paper presents the results of an experimental program based on factorial design, applied to predict the mechanical properties of butt-welded joints of S420MC and S460MC hot-rolled, high-strength low-alloy (HSLA) steel plates with 2mm, 4mm and 8mm thickness. Gas Metal Arc Welding (GMAW) was used and correlations between the main process parameters and the related mechanical properties of the welded joints were found. Obtained mathematical correlations can be exploited to provide optimal combination of welding parameters to fit the quality requirements of the end-users for envisaged welded product.

Abstract: In this work, gas metal arc welding of AISI 304 stainless steel at varying compositions of argon-CO₂ shielding environment was performed using an established optimum parametric combination. Thereafter, investigations on the microstructure of the welded joints and mechanical properties of the weldments were carried out. Weldments of excellent surface quality that are void of spatters and pores were obtained when the shielding gas composition (wt.%) range is between 100% argon and 75% argon - 25% CO₂. Increasing percentage composition of CO₂ beyond 25% resulted in irregular bead formation characterized with spatters and pores. The hardness of the welded joint became significantly high as the CO₂ composition in the shielding gas increased. The highest value of 310 HV was obtained when the shielding gas composition was 5% argon- 95% CO₂. The least (220 HV) was obtained when the shielding gas was 100% argon. High ultimate tensile strength (596 - 378 MPa) was achieved when the shielding gas composition range is between 100% argon and 75% argon-25% CO_2. The UTS dropped significantly as the CO₂ composition in the shielding gas increased beyond 25%. It decreased from 336 MPa at 70% argon-30% CO₂ shielding gas composition to 133 MPa when 100% CO₂ was utilized as the shielding gas. At the end, the effects of the CO₂ addition and suitable composition of CO₂ addition to argon shielding environment during GMAW of AISI 304 stainless steel have been established.

Abstract: Experiments proved that the arc voltage influences its spatial form and electrode metal transfer behavior characteristics during twin electrode GMAW with a single power source. Two specific arc forms were revealed for two corresponding types of metal transfer. The V-shaped arc exists on the melt drop common to the two consumable wires at voltage rate 24-27 V. The columnar shaped arc is formed due to voltage increase up to 34-36 V, which results in increased mobility of the cathode spot in the weld pool surface. As a result, the arc travels between the ends of two electrode wires, and the metal is transferred in drops of small size. It was demonstrated that for the common drop formation the gas mixture of 82% Ar+18% CO₂ is preferable to pure argon. It decreases the surface tension on the boundary between the melted electrode metal and the vapor-gas mixture, resulting in the increased volume of the common drop. It was found that a consistent common arc from two electrode wires decreases dilution is made up 43%, which is 1,65 times more and improves the deposited metal formation quality.

Abstract: Wire arc additive manufacturing (WAAM) of titanium parts shows promising potential for aerospace application due to its high deposition rates allowing a fast and economical production of large integral parts. However, due to the demands of aerospace industry an extensive qualification procedure is necessary to enable the parts as ready to fly. Nowadays, qualification for additive manufactured parts is a time-consuming process, so the advantages in additive manufacturing cannot be fully utilized. For this reason, a complete process qualification for WAAM would reduce the costs drastically in contrast to qualifying manufactured parts individually. As a first step the robustness and reproducibility of the energy reduced WAAM process was investigated. Thick-walled samples are manufactured layer by layer with an oscillating welding head motion. The mechanical properties of the samples are compared on an adequate statistical basis. Microstructural-and computer tomography analysis are conducted to comprehend shown interactions. The reproducibility is investigated in dependence of different heat treatment states, different directions of mechanical testing and two manufacturing systems of the same type.

Abstract: In this study, the GMAW parameters for welding of A36 mild steel have been investigated to get the minimum of distortion. The type of welded joint used was square groove T-joint fillet weld with filler wire ER70S-6. The welding current and the welding speed were selected as input parameters while the response used was distortion (longitudinal bending distortion and angular distortion). Taguchi method was used to determine optimal welding parameters which the minimum distortion. Design of experiment was set two factors with three level in each factor and three replication, so the L₉ Taguchi’s orthogonal array was applied. The minimum conditions were determined using S/N ratio with a quality character of smaller is better (SB). In addition, to determine the significance of the welding parameters used ANOVA. The results show that the welding current of 170 A and the welding speed of 4.0 mm/s were obtained as the minimum of longitudinal bending distortion and angular distortion. Based on analysis of variance, the welding current was a parameter that greatly affects the longitudinal bending distortion with the percentage contribution of 64.36% while angular distortion was strongly influenced by welding speed parameter with the percentage contribution of 53.38%.