Kamel Touileb

Hot cracking in welding is a very complex phenomenon. It can happen in the weld metal zone during solidification but also in the heat-affected zone (HAZ). Hot cracking defects are material decohesion that occur at high temperatures along grain boundaries when the strain and strain rate exceed a certain level. The cracks can be internal or open to the surface in the weld bead. During a welding operation, different types of hot cracks can appear, such as hot cracking due to solidification, hot cracking due to liquation, hot cracking due to loss of ductility. The main factors favoring hot solidification cracking include the presence of residual elements and impurities, leading to the formation of a low-melting eutectic; the solidification mode; and mechanical restraints. This review paper gives an introduction to solidification cracking in stainless-steel welds, the weldability of the austenite grades, and the causes of solidification cracking occurrence. The main methods with which to detect and inspect cracks are investigated. Particular focus is placed on TIG (tungsten inert gas), also known as Gas Tungsten Arc Welding (GTAW). A review of the literature reveals that considerable progress has been made in terms of the improvement in the properties of the weld joint through the application of mitigation means and strategies. The effort made by researchers in understanding solidification cracking phenomena has been key to enhancing cracking resistance and ensuring the integrity of structures.

The objective of this work was to investigate the effect of a special activating component, under the ZB-3 brand, on the welding and technological properties of a welding electrode when incorporated into the coating of a rutile welding electrode. Pulsed radiation activation was used to produce the nanostructured activating component ZB-3. The results showed the beneficial effect of the electrode doped with ZB-3 on the formation of welding beads. At the same time, an improvement in the quality of weld formation is observed with a ZB-3 activator content of up to 8%. The qualities of the weld formation were significantly improved. Also, an increase in the breaking length of the electrode arc by more than 10% was established with a ZB-3 activator content of up to 2%, and the depth of penetration of the welded metal increased to 40%.

This paper examines the use of metallurgical process waste in welding electrode coatings and their impact on the quality and properties of welded joints in carbon steels. The results demonstrate that the use of metallurgical process waste in slag coatings for welding electrodes can significantly reduce the cost of the charge without degrading the welding properties of the electrodes or the quality and properties of the welded joints. The new electrode under study was fabricated using technological waste of metallurgical plants for the welding electrodes (IMAN-9). An activator additive consisting of nanostructured functional ceramics ZB-1 was introduced into the coating at an amount of 1% to increase the melting capacity of the welding electrode. This electrode is characterized by low cost, good welding properties, and ensures high-quality welded joints and beads. This paper also includes comparative tests of welded joints in low-carbon AISI 1017 steel using the IMAN-9 electrode and the ESAB E6013 electrode, which is widely used in the global market. Research has shown that IMAN-9 electrodes, compared to ESAB E6013 electrodes, offer superior performance in terms of weld metal penetration, weld metal structure, and weld joint ductility. In terms of strength, welds made by the IMAN-9 electrodes are slightly inferior to those made by the ESAB E6013 electrodes.

This study investigates, in the first stage, the mechanical properties of Glass Fiber (GF) and Date Palm Fiber (DPF)-reinforced polyester hybrid composites. Specimens were prepared with volume compositions of GF:DPF at 100:0%, 75:25%, 50:50%, 25:75%, and 0:100%. The results showed that the best Ultimate Tensile Strength (UTS) (23.00 MPa) was obtained for the 50:50% composition, while the highest absorbed energy (E-absor) in the impact test (3.76 J) was recorded for the 100:0% composition. In the second stage, the mechanical properties were further improved by incorporating nanoparticles: Carbon Nanotubes (CNT), Alumina (Al₂O₃), and Silica (SiO₂). A Design of Experiments (DOE) approach was carried out based on the best mechanical results, using ten nanoparticle-doped specimens. The mixing method in Minitab 17 software was used to identify the optimal combination, which was 88% CNT and 12% Al₂O₃. Consequently, the tensile strength increased to 35 MPa, and the (E-absor) reached 4 J.

The present work contributes to previous research regarding the influence of Photocatalyst Nanostructured Functional Ceramics (PNFC) additives on the welding and technological properties of welding electrodes of the MR-3 brand. It presents a comparative analysis of the properties of welded joints obtained during welding with the developed welding electrodes, with additives of PNFC brand ZB-2 (IMAN-8), and the ESAB E6013 welding electrodes. The focus was placed on the weld morphology, microstructure, and mechanical properties in Shielded Metal Arc Welding (SMAW). The results show that incorporating up to 2% PNFC ZB-2 in the electrode coating enhances melting efficiency, arc stability, weld formation, and the microstructural characteristics of the weld metal. Compared to ESAB E6013 electrodes, IMAN-8 electrodes exhibit better performance in arc penetration, weld metal structure, and mechanical properties of welded joints. From an economic perspective, IMAN-8 electrodes offer significant advantages over E6015 electrodes, reducing total welding time by up to 50%, lowering electrode and electricity consumption by approximately 50%, and cutting overall welding costs by nearly half. Also, the ability to weld thin sheets of carbon steel with IMAN-8 electrodes in one pass reduces the likelihood of defects requiring reworking the weld.

Tungsten Inert Gas (TIG) welding is a widespread welding process used in the industry for high-quality joints. However, this welding process suffers from lower productivity. Activated Tungsten Inert Gas (ATIG) is a variant of the TIG that aims to increase the depth penetration capability of conventional TIG welding. This is achieved by applying a thin coating of activating flux material onto the workpiece surface before welding. This work investigates the effect of the thermophysical properties of individual metallic oxide fluxes on 316L stainless steel weld morphology. Four levels of current intensity (120, 150, 180, 200 A) are considered. The weld speed up to 15 cm/min and arc length of 2 mm are maintained constant. Thirteen oxides were tested under various levels of current intensity in addition to multiple thermophysical properties combinations, and the depth penetration (D) and the aspect ratio (R) were recorded. This process has provided 52 combinations (13 oxides * 4 currents). Based on the numerical observations, linear and nonlinear models for describing the effect of the thermophysical parameters on the weld characteristics were tuned using a particle swarm optimization algorithm. While the linear model provided good prediction accuracy, the nonlinear exponential model outperformed the linear one for the depth yielding a mean absolute percentage error of 17%, a coefficient of determination of 0.8266, and a root mean square error of 0.9665 mm. The inverse optimization process, where the depth penetration ranged from 1.5 mm to 12 mm, thus covering a large spectrum of industries, the automotive, power plants, and construction industries, was solved to determine the envelopes’ lower and upper limits of optimal oxide thermophysical properties. The results that allowed the design of the fluxes to be used in advance were promising since they provided the oxide designer with the numerical ranges of the oxide components to achieve the targeted depths. Future directions of this work can be built around investigating additional nonlinear models, including saturation and dead-zone, to efficiently estimate the effect of the thermophysical properties on the welding process of other materials.

The present work is a comparative analysis of the properties of welded joints obtained during welding with the developed welding electrodes containing additives of photocatalysts of nanostructured functional ceramics (PNFC) brand ZB-1 (IMAN-7) and the ESAB E6013 welding electrodes. This study investigates the weld morphology, microstructure, and mechanical properties of Shield metal arc welding (SMAW) welded joints. The results of the studies showed that the introduction of PNFC brand ZB-1 into the coating of welding electrodes up to 1% has a beneficial effect on the melting ability and stability of the welding arc, formation of the bead, microstructure of the weld bead, and mechanical properties of the welded joints. It was found that IMAN-7 electrodes, compared to the ESAB E6013 electrodes, have better performance in terms of arc penetration, bead metal structure, and relative elongation of welded joints. In addition, the high melting capacity of the IMAN-7 electrode allows for economic advantages, such as increased productivity and a two-fold reduction in electrode consumption.

The synthesis of special photocatalysts of nanostructured functional ceramics (PNFC) under the ZKHM brand under the influence of concentrated solar radiation showed the effectiveness of these ceramic materials in multifunctional use, in particular as additives for coatings of welding electrodes. However, problems with producing these materials in solar ovens on an industrial scale did not allow the widespread use of this method. This problem was solved using the technique of PNFC synthesis, followed by activation by pulsed radiation generated by functional ceramics. The ceramic material obtained by this method under the brand name ZB-1 also showed its effectiveness when used as an additive in welding electrode coatings. A comparative analysis of the effectiveness of the actions of additives from the ZKHM and ZB-1 brands on the welding and technological properties of welding electrodes from the MR-3 brand was carried out. Comparative results for the formation of weld beads showed that beads with high-quality formation without external defects were achieved when surfaced with electrodes with additives from both brands at concentrations up to 1%. Also, at concentrations up to 1%, these additives increased the breaking length of the arc and the stability of arc welding. The different effects of these additives were observed in a comparative analysis of their impacts on the size of the visor at the end of the electrode, the coefficients of melting and surfacing, and the loss factor for fumes and splashing of electrode metal.

The present work aims to study the influence of Nanostructured Functional Ceramics Photocatalysts (PNFC) under the brand name ZB-2, obtained using a synthesis method deploying pulsed radiation activation technology on welding and technological properties. This method of obtaining ceramic material allows the latter to be produced on an industrial scale. Therefore, it can replace the technology for producing PNFC under the influence of concentrated solar radiation at the Big Solar Furnace (BSF) of the Institute of Materials Science, Academy of Sciences of the Republic of Uzbekistan. The ZB-2 ceramic material has shown its effectiveness when used as an additive in the coating charge of the MR-3 welding electrode. Thus, the breaking arc length of the MR-3 welding electrode is increased up to 2% with the addition of ZB-2 to the coating charge. With additions of more than 2%, the breaking arc length decreases. The additive ZB-2 has the same effect on the diameter of the deposited point of the MP-3 welding electrode. When its content in the coating is up to 2%, the diameter of the deposited point increases, and a further increase in the additive content reduces this indicator. Adding up to 1% ZB-2 into the coating composition has a beneficial effect on the size of the peak at the end of the electrode. When its content exceeds 1%, the latter decreases. Also, an increase in the content of the PNFC additive in the coating of the MR-3 electrode reduces the value of the melting coefficient and increases the value of the deposition coefficient, which contributes to a sharp reduction in losses due to waste and spattering up to 53% when the additive content in the coating mass is up to 8%.

Duplex stainless-steel grade 2205 (2205 DSS) is the most widely used of the current duplex materials. The duplex steel alloy is characterized by high strength and high corrosion resistance through enhancing nitrogen and molybdenum contents. The activated tungsten inert gas (ATIG) welding technique uses the same equipment as tungsten inert gas (TIG), but prior to the welding operation, a thin layer of flux is deposited. Activation fluxes are known to influence the shape and energy characteristics of the arc. They promote the change in shapes and dimensions of the welds, namely, increasing the depth and narrowing the weld width. This work is dedicated to investigate the influence of the thermophysical properties of individual metal oxide fluxes on 2205 DSS welding morphology. It helps also to identify the recommended flux properties in order to perform full penetrated ATIG welds. Thirteen kinds of oxides (SiO₂, TiO₂, Fe₂O₃, Cr₂O₃, ZnO, Mn₂O₃, V₂O₅, MoO₃, Co₃O₄, SrO, ZrO₂, CaO, and MgO) have been tested and three current intensity levels (120, 150 and 180 A) have been considered. The results showed that the main input factors affecting the weld depth (D) were the welding current intensity with a contribution of up to 53.36%, followed by the oxides enthalpy energy with 15.05% and then by the difference between the oxides and the base metal of 2205 DSS (BM 2205 DSS) melting points with a contribution of 9.71% of the data variance. The conditions on individual oxides’ thermophysical properties to achieve full penetrated weld beads have been also revealed.