The Effect of Nanostructured Functional Ceramics Additives on the Properties of Welding Electrodes

The present work aimed to develop a new coated electrode weld based on ceramic materials. Photocatalysts of nanostructured functional ceramics (PNFCs) were synthesized by means of concentrated solar radiation on ceramic materials. This new process allows the efficient conversion of the energy of the primary source into pulsed radiation, through the adjustable and judicious choice of parameters. The photocatalysts also showed high activity when they were introduced into an electrode coating. The main problem is the complexity of the production of NFC photocatalysts on an industrial scale. A new method was developed for producing ZB-1-grade NFC catalysts using conventional technology, with subsequent activation via pulsed radiation generated by functional ceramics. The results of the addition of NFC photocatalysts obtained using this technology on the welding and technological properties of welding electrodes of the MR-3 brand are presented. The introduction of 1% to 8% NFC of the ZB-1 grade into the coating enhanced the stability of arc burning (Lbla) and increased the diameter of the weld point (ødp.). Moreover, the addition of 1% to 8% NFC of the ZB-1 brand into the coating contributed to a reduction in the losses factor for waste and splashing of electrode metal (ψ) leading to a reduction in the height of the visor at the end of the electrode (hk)

Effect of Binary Oxide Flux on Weld Shape, Mechanical Properties and Corrosion Resistance of 2205 Duplex Stainless Steel Welds

Duplex stainless steel (DSSs) is characterized by excellent corrosion resistance with high strength. Twelve single-component fluxes (TiO2, Fe2O3, Cr2O3, ZnO, ZrO2, CaO, Mn2O3, V2O5, MoO3, SrO, MgO, and LaO2) were tested in the initial experiment using activated Tungsten inert gas (ATIG) technic, and then three couples of oxides were selected as binary fluxes (Fe2O3-Cr2O3, ZnO-Mn2O3, and V2O5-Mn2O3) for the rest of the study. The results show that the depth weld of binary oxides (Fe2O3-Cr2O3, ZnO-Mn2O3) was increased by 3.7 times in comparison with tungsten inert gas (TIG) weld bead. The hardness and the tensile strength of welds carried out with Fe2O3-Cr2O3 and ZnO-Mn2O3 binary fluxes were close to those of the parent metal. Weld bead executed with ZnO-Mn2O3 oxides has more capability to withstand sudden loads. Potentiodynamic polarization tests were performed. The metal welded with flux composed of Fe2O3-Cr2O3 has been found the most resistant to corrosion

Mechanical Properties and Microstructure of TIG and ATIG Welded 316L Austenitic Stainless Steel with Multi-Components Flux Optimization Using Mixing Design Method and Particle Swarm Optimization (PSO)

In this study, the effects of pseudo-ternary oxides on mechanical properties and microstructure of 316L stainless steel tungsten inert gas (TIG) and activating tungsten inert gas (ATIG) welded joints were investigated. The novelty in this work is introducing a metaheuristic technique called the particle swarm optimization (PSO) method to develop a mathematical model of the ultimate tensile strength (UTS) in terms of proportions of oxides flux. A constrained optimization algorithm available in Matlab 2020 optimization toolbox is used to find the optimal percentages of the selected powders that provide the maximum UTS. The study indicates that the optimal composition of flux was: 32% Cr2O3, 43% ZrO2, 8% Si2O, and 17% CaF2. The UTS was 571 MPa for conventional TIG weld and rose to 600 MPa for the optimal ATIG flux. The obtained result of hardness for the optimal ATIG was 176 HV against 175 HV for conventional TIG weld. The energy absorbed in the weld zone during the impact test was 267 J/cm2 for the optimal ATIG weld and slightly higher than that of conventional TIG weld 256 J/cm2. Fracture surface examined by scanning electron microscope (SEM) shows ductile fracture for ATIG weld with small and multiple dimples in comparison for TIG weld. Moreover, the depth of optimized flux is greater than that of TIG weld by two times. The ratio D/W was improved by 3.13 times. Energy dispersive spectroscopy (EDS) analysis shows traces of the sulfur element in the TIG weld zone

Particle Swarm Method for Optimization of ATIG Welding Process to Joint Mild Steel to 316L Stainless Steel

316L stainless steel joined to mild steel is widespread in several applications to reach a requested good association of mechanical properties at a lower cost. The activating tungsten inert gas (ATIG) weld was carried out using a modified flux composed of 76.63% SiO2 + 13.37% Cr2O3 + 10% NaF to meet standard recommendations in terms of limiting the root penetration. Modified optimal flux gave a depth of penetration 1.84 times greater than that of conventional tungsten inert gas (TIG) welds and a root penetration of up to 0.8 mm. The microstructure of the dissimilar joints was investigated using a scanning electron microscope and EDS analysis. The mechanical properties of the weld were not affected by the modified flux. The results show that the energy absorbed in the fusion zone in the case of ATIG weld (239 J/cm2) is greater than that of TIG weld (216 J/cm2). It was found that the weld bead obtained with the optimal flux combination in ATIG welding can better withstand sudden loads. The obtained UTS value (377 MPa) for ATIG welding was close to that of TIG welding (376 MPa). The average Vickers hardness readings for ATIG welds in the fusion zone are up to 277 HV, compared to 252 HV for conventional TIG welding

The Influence of Tool Pin Geometry and Speed on the Mechanical Properties of the Bobbin Tool Friction Stir Processed AA1050

AA1050 plates of 8 mm thickness were processed via bobbin-tool friction stir processing technique at a constant rotation speed of 600 rpm and different travel speeds ranging from 50 to 300 mm/min using three-pin geometries of triangle, square, and cylindrical. The temperatures of the processed zone, the advancing side, and the retreating side were measured; the machine torque during processing was also recorded. The processed materials were evaluated in terms of surface roughness, macrostructure, tensile properties, and hardness measurements. The fracture surfaces of the tensile fractured specimens were investigated using SEM. The results indicated that the pin geometry and processing speed significantly affect the generated heat input and the morphology of the processed zone. The peak temperature in the center of the processed zone decreases with increasing the travel speed from 50 to 300 mm/min at all applied pin geometries. The maximum temperature of ~400 °C was reached using the cylindrical pin geometry. The machine torque increases with increasing the travel speed at all applied pin geometries, and the highest torque value of 73 N.m is recorded using the square pin geometry at 300 mm/min travel speed. The top surface roughness of the processed area using the cylindrical pin is lower than that given by the other pin geometries. Under all applied conditions, the hardness of the processed area increases with increasing travel speed, and the cylindrical pin shows a higher hardness than the other pin geometries with 19% enhancement over the BM. The AA1050 processed using a cylindrical pin at 200 mm/min travel speed and a rotation speed of 600 rpm produces a sound processing zone with the highest ultimate tensile strength of 79 MPa

Microstructure, Crystallographic Texture, and Mechanical Properties of Friction Stir Welded Mild Steel for Shipbuilding Applications

In the current work, mild steel used in shipbuilding applications was friction-stir-welded (FSWed) with the aim of investigating the microstructure and mechanical properties of the FSWed joints. Mild steel of 5 mm thickness was friction-stir-welded at a constant tool rotation rate of 500 rpm and two different welding speeds of 20 mm/min and 50 mm/min and 3° tool tilt angle. The microstructure of the joints was investigated using optical and scanning electron microscopes. Additionally, the grain structure and crystallographic texture of the nugget (NG) zone of the FSWed joints was investigated using electron backscattering diffraction (EBSD). Furthermore, the mechanical properties were investigated using both tensile testing and hardness testing. The microstructure of the low-welding-speed joint was found to consist of fine-grain ferrite and bainite (acicular ferrite) with an average grain size of 3 µm, which indicates that the temperature experienced above A1, where a ferrite and austenite mixture is formed, and upon cooling, the austenite transformed into bainite. The joint produced using high welding speed resulted in a microstructure consisting mainly of polygonal ferrite and pearlite. This could be due to the temperature far below A1 experienced during FSW. In terms of joint efficiency expressed in terms of relative ultimate tensile, the stress of the joint to the base material was found to be around 92% for the low-speed joint and 83% for the high-welding-speed joint. A reduction in welding was attributed to the microstructure, as well as the microtunnel defect formed near the advancing side of the joint. The tensile strain was preserved at 18% for low welding speed and increased to 24% for the high welding speed. This can be attributed to the NG zone microstructural constituents. In terms of crystallographic texture, it is dominated by a simple shear texture, with increased intensity achieved by increasing the welding speed. In both joints, the hardness was found to be significantly increased in the NG zone of the joints, with a greater increase in the case of the low-welding-speed joint. This hardness increase is mainly attributed to the fine-grained structure formed after FSW

Bobbin Tool Friction Stir Welding of Aluminum: Parameters Optimization Using Taguchi Experimental Design

This work aims to optimize the performance evaluation characteristics such as the temperature at the weld center of the lap joint (Tw), the tensile shear load (TSL), and the hardness using an experimental design experiment for bobbin tool friction stir welding (BT-FSW) of AA1050 lap joints. BT-FSW is characterized by a fully penetrated pin and double-sided shoulder that promote symmetrical solid-state welds. This study contributes to improving the quality of 10 mm thick lap joints and addressing challenges to obtaining a sound weld deprived of any defects. Taguchi L9 orthogonal array (OA) experimental design was performed. Three different pin shapes (cylindrical, triangular, and square) and three levels of welding travel speeds of 200, 400, and 600 mm/min were selected as input controllable process parameters at a constant tool rotation speed of 600 rpm. A travel speed of 200 mm/min with square pin geometry significantly improves the TSL of the joint up to 6491 N. However, the hardness characteristic is optimized by using 600 mm/min travel speed and a cylindrical tool pin. The minimum temperature in the weld joint can be obtained using 600 mm/min or more with triangular pin geometry. From ANOVA results, it was seen that the BT-FSW of AA 1050 thick lap joints performance in terms of TLS and Tw were greatly influenced by travel speed; however, the tool shape influences the hardness more. For the validation of the models, BT-FSW experiments have been carried out for AA1050 using the applied processing parameters. Furthermore, regression models were developed to predict the Tw, TSL, and hardness. The calculated performance properties from the mathematical models were in an acceptable range compared to the measured experimental values

Microstructure, Crystallographic Texture, and Mechanical Properties of Friction Stir Welded Mild Steel for Shipbuilding Applications

In the current work, mild steel used in shipbuilding applications was friction-stir-welded (FSWed) with the aim of investigating the microstructure and mechanical properties of the FSWed joints. Mild steel of 5 mm thickness was friction-stir-welded at a constant tool rotation rate of 500 rpm and two different welding speeds of 20 mm/min and 50 mm/min and 3° tool tilt angle. The microstructure of the joints was investigated using optical and scanning electron microscopes. Additionally, the grain structure and crystallographic texture of the nugget (NG) zone of the FSWed joints was investigated using electron backscattering diffraction (EBSD). Furthermore, the mechanical properties were investigated using both tensile testing and hardness testing. The microstructure of the low-welding-speed joint was found to consist of fine-grain ferrite and bainite (acicular ferrite) with an average grain size of 3 µm, which indicates that the temperature experienced above A1, where a ferrite and austenite mixture is formed, and upon cooling, the austenite transformed into bainite. The joint produced using high welding speed resulted in a microstructure consisting mainly of polygonal ferrite and pearlite. This could be due to the temperature far below A1 experienced during FSW. In terms of joint efficiency expressed in terms of relative ultimate tensile, the stress of the joint to the base material was found to be around 92% for the low-speed joint and 83% for the high-welding-speed joint. A reduction in welding was attributed to the microstructure, as well as the microtunnel defect formed near the advancing side of the joint. The tensile strain was preserved at 18% for low welding speed and increased to 24% for the high welding speed. This can be attributed to the NG zone microstructural constituents. In terms of crystallographic texture, it is dominated by a simple shear texture, with increased intensity achieved by increasing the welding speed. In both joints, the hardness was found to be significantly increased in the NG zone of the joints, with a greater increase in the case of the low-welding-speed joint. This hardness increase is mainly attributed to the fine-grained structure formed after FSW

Friction Stir Spot Welding of Different Thickness Sheets of Aluminum Alloy AA6082-T6

Friction stir spot welding (FSSW) is one of the important variants of the friction stir welding (FSW) process. FSSW has been developed mainly for automotive applications where the different thickness sheets spot welding is essential. In the present work, different thin thickness sheets (1 mm and 2 mm) of AA6082-T6 were welded using FSSW at a constant dwell time of 3 s and different rotation speeds of 400, 600, 800, and 1000 rpm. The FSSW heat input was calculated, and the temperature cycle experience during the FSSW process was recorded. Both starting materials and produced FSSW joints were investigated by macro- and microstructural investigation, a hardness test, and a tensile shear test, and the fractured surfaces were examined using a scanning electron microscope (SEM). The macro examination showed that defect-free spot joints were produced at a wide range of rotation speeds (400–1000 rpm). The microstructural results in terms of grain refining of the stir zone (SZ) of the joints show good support for the mechanical properties of FSSW joints. It was found that the best welding condition was 600 rpm for achieving different thin sheet thicknesses spot joints with the SZ hardness of 95 ± 2 HV0.5 and a tensile shear load of 4300 ± 30 N