Showing papers on "Submerged arc welding published in 2020"

Element Transfer Behaviors of Fused CaF 2 -SiO 2 Fluxes Subject to High Heat Input Submerged Arc Welding

Abstract: A series of fused CaF2-SiO2 binary fluxes have been developed to investigate element transfer behaviors under high heat input submerged arc welding. Transfer of elements is quantified by Δ quantities, which demonstrate respective contributions from the flux to the weld metal. Effects of SiO2 contents on the transfer of Si, Mn, and O have been thoroughly evaluated. Thermodynamic considerations have been attempted for constraining chemical reactions and mechanisms involved in welding.

Element Transfer Behaviors of Fused CaF 2 -TiO 2 Fluxes in EH36 Shipbuilding Steel During High Heat Input Submerged Arc Welding

Abstract: Fused CaF2-TiO2 fluxes are developed and applied on EH36 shipbuilding plates under high heat input submerged arc welding. Transfer behaviors of O and major alloying elements are systematically investigated. TiO2 contributes to O gain in the weld pool, but leads to concurrent losses of Si, Mn, and C via deoxidation and decarburization reactions. Transfer of Ti to the weld metal is suppressed due to improved flux O potential and chemical interaction between CaF2 and TiO2.

Element Transfer Behaviors of Fused CaF 2 -SiO 2 -MnO Fluxes Under High Heat Input Submerged Arc Welding

Abstract: Submerged arc welding is conducted employing CaF2-SiO2-MnO fluxes with varying MnO content under high heat input of 60 kJ/cm using EH36 shipbuilding steel. Transfer of elements between slags and weld metals is quantified. Mn and O transferred from slag to weld metal increase with MnO addition, whereas the transfer of Si seems to be independent of MnO content. Factors that govern the transfer of elements between slag and weld metal are evaluated.

Mathematical modeling and intelligent optimization of submerged arc welding process parameters using hybrid PSO-GA evolutionary algorithms

Abstract: Now-a-days, submerged arc welding processes (SAW) are immensely being applied for joining the thick plates and surfacing application. However, the selection of optimal SAW process parameters is indeed an intricate task which aims to accomplish the desired quality of welded part at an economic way. Therefore, in the present paper, the research efforts are made on an implementation of efficient hybrid intelligent algorithms, i.e., hybrid particle swarm optimization and genetic algorithm (hybrid PSO-GA) for the optimization of SAW process parameters. The emphasis was given on different direct parameters such as voltage, wire feed rate, welding speed and nozzle to plate distance and indirect parameters such as flux condition and plate thickness, respectively. The parameters were chosen at two levels using fractional factorial design to study their effect on responses including flux consumption, metal deposition rate and heat input. Besides, the linear regression technique and analysis of variance were used for mathematical modeling of each response. Then, the direct effect and interaction effect on selected responses were investigated by 3D surface plots. At the end, the performance of hybrid PSO-GA is compared with general PSO and GA algorithms for indices including success rate, best solution, mean, computational time, standard deviation and mean absolute percentage error between. The overall results suggested that the hybrid PSO-GA is better option than other two algorithms, i.e., PSO and GA for obtaining the optimum SAW process parameters.

Repair of light rail track through restoration of the worn part of the railhead using submerged arc welding process

Abstract: A surface worn C-Mn rail is repaired by retrieving the lost part of the railhead using a commercial rutile flux-cored wire submerged arc welding (SAW) method. Optical microscopy (OM), scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy (EDS), and Rockwell B hardness test are employed to investigate the properties of the repaired rail specimen. After the first set of analysis, the as-repaired rail is heated up to 1100 °C and water-quenched to room temperature to increase hardness. Each specimen is analytically partitioned into three zones including weld zone (WZ), heat-affected zone (HAZ), and the unaffected rail substrate. The as-repaired rail WZ is primarily composed of pearlite, ferrite, and austenite with a low hardness of 80 HRB, whereas the austenite phase is gone in the as-quenched rail and a massive extent of carbides are precipitated which increased hardness to 95 HRB. The microstructure of the HAZ in the as-repaired sample is a uniform distribution of fine-grained ferrite, pearlite, and carbide with the hardness of 92 HRB, while the microstructure of the identical zone in the as-quenched specimen is mainly martensitic-pearlitic with the highest average hardness among all zones, 110 HRB. The results presented an immense potential for SAW in rail repair.

Phase chemistry of submerged arc welding (SAW) fluoride based slags

Abstract: Phase chemical analysis of post-weld slags from Submerged Arc Welding (SAW) is applied to explain the chemical function of flux constituent compounds in the welding process. FactSage 6.4 calculations were used to aid in the interpretation of the phase chemical analyses. Five commercial agglomerated fluxes from two suppliers were used. These fluxes cover three types of fluoride based flux classes: Fluoride Basic flux, Aluminate Basic flux and Aluminate Rulile flux. Basic fluxes are based in the SiO2–Al2O3–MgO CaF2 system. The slag liquidus lowering effect of CaF2 is 19 °C/%CaF2 in the Fluoride Basic fluxes, and 4 °C/%CaF2 in the Aluminate Basic fluxes. The Aluminate Rutile flux is based in the SiO2–Al2O3–MgO–TiO2–MnO–CaF2 system. Little CaF2 addition is used in this flux since TiO2 addition lowers its liquidus temperature sufficiently. The level of CaF2 addition sets the quantity and chemistry of fluoride gas compounds formed. The main gas fluoride gas species expected to form in welding with the five fluxes are CaF2, MgF2, NaF, KF, NaAlF4, and AlF3. In addition, TiF3 is expected to form in welding with the Aluminate Rutile flux, indicating the importance of titanium oxidation state in fluoride gas formation.

Structural Roles of TiO2 in CaF2-SiO2-CaO-TiO2 Submerged Arc Welding Fluxes

Abstract: A series of fused CaF2-SiO2-CaO-based fluxes geared towards submerged arc welding has been prepared with incremental TiO2 additions. Through systematic investigation on physical properties, quantitative relationship between TiO2 content and corresponding structural information has been established, and the roles played by TiO2 have been profiled. It is found that TiO2 has been introduced into the silicate network by acting as network-former, increasing the degree of polymerization while lowering the strength of the flux.

Mechanical properties and microstructural characterization of a novel 316L austenitic stainless steel coating on A516 Grade 70 carbon steel weld

Abstract: The aim of this work is to characterize properties and microstructure of AISI 316L stainless steel used as a coating on welding of carbon steel sheets. Two carbon steel plates were set as the metal base and the stainless steel coating was applied on the weld bead. The applied process used was the submerged arc welding (SAW) and tests were carried out for the tensile strength and Vickers hardness, in addition to observation of the microstructure by optical microscopy. The results indicated that the stainless-steel coating applied on the weld bead provided relatively high values of tensile strength. Moreover, the hardness values suggest that the investigated innovative material can be applied in corrosive environments.

Residual neural network-based fully convolutional network for microstructure segmentation

Abstract: In this study, microstructures of weldment produced using carbon steel A516 grade 60 were analysed via a deep learning approach to measure the fraction of acicular ferrite which considerably influe...

Elucidating the Roles of SiO2 and MnO upon Decarburization During Submerged Arc Welding: A Thermodynamic Study into EH36 Shipbuilding Steel

Abstract: By employing CaF2-SiO2 and CaF2-SiO2-MnO system fluxes, the roles of SiO2 and MnO in decarburization behaviors during submerged arc welding of EH36 shipbuilding steel have been quantified and evaluated. All possible reactions associated with C transfer and interfaces at which these reactions occur are systematically discussed. It is concluded that the addition of SiO2 and MnO exerts synergistic effects on the extent of decarburization due to increased partial pressures of O2 and SiO gases in the plasma, improved O level in the weld pool, and higher activities of the oxides, such as SiO2, MnO, and FeO, at the slag–metal interface. The investigation over the macrographic detached slag surfaces shows that the possibility of bubble nucleation is highly influenced by flux formula. The effect of heat input on decarburization is discussed, and the optimal flux compositions expected in the present study are analyzed.

Multi-objective optimization of residual stresses and distortion in submerged arc welding process using Genetic Algorithm and Harmony Search:

Abstract: Residual stresses and distortion in welded joints undermine the durability of the structure and prevent a correct assembly of the parts. The principal objective of this study is to find a solution ...

Microstructure and Charpy Impact Properties of FCAW and SAW Heat Affected Zones of 100 mm Thick Steel Plate for Offshore Platforms

Abstract: In this study, heat affected zone (HAZ) specimens were fabricated by applying flux-cored arc welding (FCAW) and submerged arc welding (SAW) processes to steel plate with a thickness of 100 mm and yield strength of 460 MPa for use in offshore platforms. The correlation between microstructure and Charpy absorbed energy was investigated, and fracture mechanisms were analyzed. As distance from the fusion line increases, heat input and cooling rate decrease, making it difficult to form low-temperature transformation microstructures in HAZ specimens and increasing the grain size of quasi-polygonal ferrite. The FCAW process is advantageous for low-temperature transformation microstructures because it has a lower heat input and a faster cooling rate than the SAW process. Plastic deformation and ductile fracture occurred at low temperatures in fine acicular ferrite and quasi-polygonal ferrite regions of HAZ specimens, but brittle fractures occurred in bainitic ferrite, granular bainite, and coarse quasi-polygonal ferrite regions. The unit crack path in the brittle fracture region was similar to the grain size. In other words, as the volume fraction of fine acicular ferrite and quasi-polygonal ferrite increased in HAZ specimens, Charpy absorbed energy at low temperature increased.

Fine-Tuned Element Transfer Strategies for Ternary CaF2-SiO2-CaO Fluxes in Submerged Arc Welding: An Environmentally Friendly Approach

Abstract: Submerged arc welding under high heat input has been conducted on EH36 plate employing two series of CaF2-SiO2-CaO-fused fluxes. The effects of CaO and SiO2 on element transfer between slag and weld metal are systematically evaluated using thermodynamics. It is concluded that the substitution of CaF2 by CaO is an environmentally friendly approach to suppress the transfer of Si to weld metal and decrease the loss of Mn from weld metal to slag.

Effects of the Welding Process and Consumables on the Fracture Behavior of 9 Wt.% Nickel Steel

Abstract: In recent years, stringent environmental regulations for air pollution have led to increased demand for liquefied natural gas (LNG). Therefore, the demand for the design and construction of LNG-fueled vessels has also increased. One of the most important points for the design of LNG-fueled vessels is the structural integrity of the LNG fuel tank, particularly at cryogenic temperatures. Low temperature materials are used in the construction of LNG fuel tanks to ensure structural safety. Among the various low temperature materials, nickel steel is commonly employed for the design of LNG storage tanks. In addition, Shielded Metal Arc Welding (SMAW) and Submerged Arc Welding (SAW) are commonly applied to the construction of LNG storage tanks. On the other hand, the application of Flux Cored Arc Welding (FCAW) for nickel steel as an alternative to SMAW and SAW appears to be necessary, considering the high productivity. Nevertheless, there have been few studies of the fracture behavior of nickel steel with FACW compared to SMAW and SAW processes. This study examined the fracture characteristics of 9% nickel steel and weldments considering application for the LNG storage tanks. The fracture characteristics of FCAW was compared with SMAW at 25°C and − 163°C temperatures. As the result, the mechanical properties with FCAW were higher than those with SMAW at 25°C and − 163°C. In addition, SMAW is slightly better than FCAW in terms of the impact absorbed energy. Moreover, the crack tip opening displacement (CTOD) values of the weld metal and heat affected zone (HAZ) with FCAW were higher than those with SMAW.

Performance Evaluation of Alternating Current Square Waveform Submerged Arc Welding as a Candidate for Fabrication of Thick Welds in 2.25Cr-1Mo Heat-Resistant Steel

Abstract: The paper evaluates the performance of alternating current (AC) square waveform submerged arc welding (SAW) as a candidate technology for manufacturing thick welds for high-pressure vessels. A new mathematical formulation for calculating melting efficiency in square waveform arc welding is presented. The melting efficiency and the heat consumption are presented as a mathematical model of welding parameters, namely welding current, welding speed, current frequency, and electrode negativity (EN) ratio. The proposed approach is demonstrated through the welding of 2.25Cr-1Mo heat-resistant steel performed over a wide range of welding parameters. The investigation provides deeper insights into the interplay between process parameter, total heat consumption, and melting efficiency. The effect on flux consumption is also explained. The melting efficiency is inversely proportional to flux consumption. The welding heat does not necessarily promote the plate melting. Improper use of welding heat may lead to decreased melting efficiency and increased unwanted melting and consumption of welding flux. Compared to the conventional direct current (DC) power sources, the AC square waveform welding achieves almost the same order of melting efficiency with added advantages of better weld bead shape and flux consumption in a desirable range. The two additional parameters (frequency and EN ratio) of the AC square waveform power source provide more freedom to fine-tune the process and thereby efficiently use welding heat. The results of this investigation will be advantageous to the designers and fabricators of high-pressure vessels using AC square waveform welding.

Develop a flux cored wire for submerged arc welding of Ni-Mo low alloy steel

Abstract: Ni-Mo low alloy steel exhibits an admirable amalgamation of high strength and toughness at subzero temperature and show resistance to brittle fracture with good weldability. This steel has been established to fulfill the needs of specific applications, such as the construction of ships and submarines. To develop a companionable wire for welding of Ni-Mo low alloy steel, the amount of the alloying elements in a wire is increased to toughen of weld metal, the wire itself has high strength so that the wire is hardened at the wire drawing, making the wire production difficult. In order to avoid the problems related to the solid wires, various flux cored wires have been developed. In this work, the effect of flux basicity index and heat input on chemical composition, oxygen-nitrogen analysis, mechanical properties and microstructure of Ni-Mo low alloy steel welded by SAW welding using flux cored wires are presented along with the effect of flux cored wire and basicity index on deposition rate.