Papers by Keyword: Dissimilar Welding

Abstract: Welding process is widely used as a metal assembly technique in various industries, including construction, automotive manufacturing, pressurization, and shipbuilding. In ship repair and fabrication, dissimilar welding between carbon steel and cast iron is often required, for example, in assembling appendages such as propeller shafts, yokes, and other equipment. Although cast iron offers high strength about 700 MPa and weight reduction benefits, its poor weldability due to high carbon content often leads to cracking when joined to carbon steel. Previous studies have found that preheating before welding mitigates rapid cooling and martensite formation, while buttering with Ni-based filler reduces carbon diffusion and carbide precipitation at the fusion boundary. This research has been carried out to investigate various procedures for dissimilar welding ductile cast iron A536 and carbon steel A36, as follows: (1) no preheat or buttering (Control), (2) preheating only (PH), (3) buttering only (BT), and (4) combined preheat and buttering (PHBT) to evaluate their effects on tensile strength, hardness, and microstructural evolution. Successful study of dissimilar welding between carbon steel and cast iron will reduce the cost of ship maintenance, increase its service life, and provide a path for more sustainable development.

Abstract: Food-grade piping and water transportation systems extensively use dissimilar welding between stainless steel and carbon steel, where cost-effectiveness and corrosion resistance are essential consideration. However, the fusion zone of dissimilar welds often observed microstructural inhomogeneities and hardness changes, thus compromising mechanical qualities and corrosion resistance. This study was seperated in two phases to investigate and optimize dissimilar welding between carbon steel and stainless steel in both plate and pipe applications. Phase 1 studied welding A36 carbon steel plate and A304 stainless steel using gas tungsten arc welding (GTAW) with ER308L filler metal, the effect of post-weld heat treatment (PWHT) holding time on the mechanical and microstructural propertie. PWHT was performed at 650 °C for 20 and 60 minutes. The 20-minute condition yielded an optimal combination of mechanical strength and microstructural refinement, while the 60-minute condition led to grain coarsening and reduced strength. Phase 2 extended the findings to pipe welding applications, adopting the 20-minute PWHT condition. Welding was performed on dissimilar joints between A106-B carbon steel pipe and A312 TP304L stainless steel pipe (2-inch OD) using ER308L and ER309L filler metals under 99.99% argon shielding. Tensile and hardness testing indicated that welds with ER309L offered superior mechanical performance. Microstructural analysis revealed delta-ferrite and stabilized austenite in the fusion zone, with enhanced Cr and Ni concentrations contributing to improved corrosion resistance, as confirmed by electrochemical testing.

Abstract: This study investigates the influence of the thermal cycle induced by the multipass weld bead when double-pulsed Gas Metal Arc Welding (GMAW-DP) is used to join duplex stainless steel (DSS) with Lean Duplex Stainless Steel (LDSS) welds, with emphasis on microestructure evolution. The microstructures of the heated affected zone (HAZ) and weld metal (WM) were analysed by light optical micorscopy (LOM), scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS) and high-energy synchrotron X-ray diffraction (HEXRD) in the different passes. They are formed by austenite and ferrite with different morphologies and fractions, associated to the dilution and thermal cycle experienced. The ferrite content was between 50 and 80%, considering the consumable used. Mechanical behaviour was evaluated by Vickers microhardness profiles. These results provide experimental data that contribute to the understanding of dissimilar welding of duplex stainless steels through GMAW-DP process.

Abstract: In developing an accurate modelling technique of thermal profile parameters when welding High-strength steel, an algorithm based on an artificial neural network (ANN) for predicting cooling time using Gas Metal Arc Welding (GMAW) was set up. The neural network developed has a 4-20-1 architecture with the input parameters of the voltage of the station (U), welding current intensity (I), welding speed (V), and heat input (Q) with the output parameter Cooling time (∆t8/5). A protocol has been developed with the MATLAB R2020a software containing three neural networks. The goal was to determine the neural network that has the lowest root mean square error (MSE). The results showed that the first system produced an MSE of 1.295 × 10⁻³ and a regression R = 0.995 with a Relative error of 0 for 8 of the initial 14 data. The second system produced an MSE of 4.278 × 10⁻³ with a regression R = 0.978 with 11/15 showing an error of 0. Finally, the third system, consisting of associated experimental data to the analytical data produced an MSE of 2.506 × 10−3 with a regression R = 0.972 with a slight difference between the input data and predicted data on all 29 points. The results obtained by the first two systems are satisfactory and developed neural networks can be found reliable for predicting cooling times of welded joints of steel high-strength.

Abstract: Welding joint Austenitic stainless steels can undergo intergranular corrosion attack in some service conditions, such as oil refineries, petrochemical plants, and industrial furnaces operating at high temperatures (between 500°C and 675°C). This research focuses on fabricating dissimilar metal welds to avoid failure due to sensitization and investigate stress-relieved carbon steel by Post-weld heat treatment (PWHT). This work studies a dissimilar weld joint (DWJ) of ASTM 335 grade P11 joint to ASTM 304L and PWHT after welding. These welding processes are used in multi-pass gas tungsten arc welding (GTAW) using filler metal R309L. PWHT at temperatures of 550 °C with holding times of 40, 50, and 60 minutes and then slow cooling in atmospheric air temperature, It was used to compare the results holding time carbon steel ASTM A335 Gr. P11 while processing. Holding time at 50 minutes has the maximum result of PWHT with 182 HV and has a good distribution of perlite with fine grain and increasing holding time also increases formed carbide on the grain boundary of stainless steel 304L.

Abstract: Taking the advantage of its low density, high specific strength and strong corrosion resistance, titanium and aluminum alloys have high marine adaptability and can be directly used in various marine engineering equipment that will expose to seawater or directly contact with seawater. The seawater heater has to withstand 90~120°C corrosion in seawater. This unique working condition makes titanium and aluminum alloys are superior materials which can significantly lower the heater construction cost. In this study, the technology of friction stir welding was used to join the dissimilar materials of aluminum alloy 6061 and commercially pure titanium by means of butt joint. High-speed steel stir rod was used for the friction stir welding, and a 2^o title was applied to the stir rod during friction stir welding. To discuss the influence of different rotating speeds and travel speed, the specimens were analyzed for their microstructure, mechanical properties, and elemental analysis was carried out followed by the friction stir welding. Experimental results showed that the best mechanical properties of the butt joint can be obtained by setting the rotational speed of 1000 rpm and the travel speed of 100 mm/min. After welding, grain refinement can be observed in the stirring zone. However, the grains in the heat-affected zone had become larger, and there had a tendency of hardness decreasing, causing failure in this area during tensile testing.

Abstract: This work examines the feasibility of joining two dissimilar metals, vanadium (V) and wrought Nitronic 40 stainless steel, through electron beam additive manufacturing (EBAM). Depositing V on Nitronic 40 led to mixed results with some builds exhibiting microcracking and other builds exhibiting severe cracking resulting in delamination. These build failures are thought to be caused by a large coefficient of thermal expansion (CTE) mismatch and solubility issues, demonstrating the challenges associated with this material combination. The large melting temperature discrepancy between Nitronic 40 and V was thought to exacerbate the issues with CTE mismatch and solubility. Four strategies could be employed by EBAM to mitigate the observed issues to successfully deposit V on Nitronic 40: (1) adjust wire feed speed, (2) use dual wire feeders, (3) use different wire feedstocks to control composition, and (4) create a transition layer known as buttering to accommodate CTE mismatch.

Abstract: In order to improve the microstructure and mechanical properties of gas metal arc dissimilar weldment of AISI 304 and 1020 carbon steel, different post-weld heat treatment (PWHT) processes including annealing, tempering and normalizing were performed. The post-tempered weldment exhibited improved grain refinement over the as-welded. The as-welded joint is characterized with the formation of hard martensitic phase and CrC precipitates while the post-weld heat treated (PWHTed) joints consist more of softer ferritic phase. The PWHTs resulted in the weldment hardness reduction with post-annealed demonstrating the least hardness. Only the post-tempered weldment demonstrated improved tensile strength (~5.2%) over the as-welded (421 MPa). All the PWHT processes resulted in improved elongation (i.e., ductility) and impact energies over the as-welded. While the entire PWHTed weldments demonstrated ductile fracture mode, the as-welded sample exhibited a combination of ductile and brittle fracture mode after the tensile test.

Abstract: Fundamental investigation of mechanical properties on different types of dissimilar welded joints was described in this paper. Dissimilar metal welding was generally employed in chemical and petrochemical plants, oil and gas industries, nuclear power plants and aerospace industries etc. For enriching the structural integrity of aerospace industries, material with high temperature resistance and high corrosion resistance is needed. For fulfilling the above criteria, Inconel 718 (IN 718) was selected due to its felicitous strengths such as yield, tensile, and creep at high temperatures with significant corrosion properties. This paper reviews the different welding processes and the impact they have on mechanical properties, as well as some difficulties related to welding dissimilar metals. Gas Tungsten Arc Welding (GTAW) process comprises high micro-hardness and tensile strength properties during dissimilar welding of IN 718. SS 410 and Inconel 625 materials hold high micro-hardness and tensile strength values respectively. The effect of IN 718 filler metal has also been discussed in this paper. Some of the dissimilar welding defects can be eliminated by IN 718 filler metal. This paper will give better directions to the researchers to focus on future studies.

Abstract: This research was conducted to investigate the effect of variations in tool rotation and surface roughness towards shear strength on the newly developed friction lap welding (FLW) for dissimilar joints between stainless steel (SS) 304 and Nylon 6 plates. Under constant welding traverse speed at 30 mm/min, the variation of tool rotation used were 1100 and 2200 rpm and surface roughness of 0.32; 1.25; and 1.88 μm initially obtained from different surface modification methods. The shear test was conducted at FLW dissimilar joint based on AWS D8.9-97 standard. The results showed that the shear stress increased along with the higher tool rotation and at the greater surface roughness. The highest shear strength value was found at the tool rotation of 2200 rpm and surface roughness of 1.88 μm with 9.447 MPa. The tool rotation may produce a higher heat input as well as an effect on the value of nylon hardness. On the other hand, rougher SS surfaces provide a larger area for the interfacial adhesive bond between nylon and metal; therefore, they can act as an interlocking site when the shear loading was applied. These phenomena were also confirmed by fracture morphology and microscopic image analysis.