Neutral Point indicates the flux formula where no transfer of alloying element between the flux and weld metal occurs. For the submerged arc welding process, Neutral Point is an essential definition ...for flux design and specification since it helps to identify the flux microalloying ability. The scientific hypothesis that the Neutral Point is only a function of the flux formula is considered as the basis of the Mitra kinetic model. Within this framework, by performing submerged arc welding with CaF2-SiO2-Na2O-MnO agglomerated fluxes under various heat inputs, the moving of Neutral Point has been captured, indicating the scientific hypothesis proposed in Mitra kinetic model may be revised under high heat input welding. Additionally, although some studies have incorporated the consideration of the gas-slag-metal equilibrium, only the effective equilibrium temperature of 2000 or 2100 °C is utilized, which may be insufficient to constrain Mn content in the weld metal. In this study, we have incorporated all possible effective equilibrium temperatures that may be attained in the submerged arc welding process to simulate the transfer behavior of Mn. Then, a novel thermodynamic approach is proposed to detect the moving direction of Neutral Point for Mn from both slag-metal and gas-slag-metal equilibrium considerations, which may pave a vital way for the flux design and the setting of welding parameters. The factors responsible for the deviation between real and predicted data are discussed. The mechanism responsible for the moving of Neutral Point regarding the Mn element is evaluated from the perspective of both slag-metal and gas-slag-metal equilibrium considerations.
•Heat source distributions of arc with 600 a were simulated by a grid-based method.•Penetration depth obtained by coupled DEM-ISPH simulation agreed with experiment.•Welding flux initially heated the ...metal and was subsequently heated by the metal.•The slag covering the metal maintained the metal surface temperature.
Two-dimensional axisymmetric heat source distributions of the arc plasma were obtained by a grid-based simulation. These distributions and a particle-based method that couples the discrete element method (DEM) and incompressible smoothed particle hydrodynamics (ISPH) were then applied to verify the mechanisms of slag and weld pool formation and the thermal effects of flux and slag on the base metal, weld pool and weld bead. The slag and weld pool were simulated together, and their formation and resolidification mechanisms were verified. The velocity fields in the weld pool showed that the transport of high-temperature molten metal from the weld pool surface behind the center of the heat source to the bottom of the weld pool heated the bottom of the weld, leading to deep penetration. It was found that the heat on the metal surface near the heat source was temporarily absorbed by the flux, and the heat was transferred back to the metal surface after the heat source passed. The temperature decrease of the metal surface was also limited by the slag covering the metal surface, leading to a higher surface temperature in submerged arc welding than in gas metal arc welding.
In present study, the wettability behaviour of basic submerged arc welding fluxes for the CaO–CaF2–SiO2 & CaO–SiO2–Al2O3 welding flux system was studied by measuring the contact angle between the ...solid/liquid interfaces. Twenty-one submerged arc welding fluxes were formulated using mixture design approach. Contact angle of twenty-one basic fluxes were measured at 1100 °C at constant heating rate. X-ray fluorescence technique was used to evaluate the purity level of individual flux components. Phase analysis and structural properties of different fluxes were determined using Fourier transform infrared spectroscopy & X-ray diffraction technique. Using Young's & Boni's equations different surface tension values for CaO–CaF2–SiO2 & CaO–SiO2–Al2O3 flux systems were determined from measured contact angle value. Dupre's equation was used to find the adhesion energy of the fluxes. Optimum wetting behaviour was observed for lower compositional range (i.e. for CaO/SiO2 & CaO/CaF2 ratio). Flux number 1, 2, 3, 4, 7, 12, 14, 17, 18, 19, 20 & 21 gives higher wettability and spreading area (mm2) due to lower value of contact angle. With increase of CaO/SiO2 ratio there is significant increase in calculated surface tension.
In this study, the usability of a new submerged arc welding flux was investigated to develop the surface properties of Hardox steels. In the hardfacing welding processes for Hardox 400 steel, four ...welding speeds resulting in varied heat inputs were applied. Through an analysis of the chemical composition, microstructure examinations, hardness measurements and wear tests, the possibility of hardfacing properties control due to the change of process parameters were determined. In the experimental studies, the hardness of the hardfacing obtained at a welding speed of 30 cm × min-
was measured as 42 HRC while the hardness of the hardfacing obtained at a welding speed of 48 cm × min-
was measured as 57 HRC. Moreover, in the wear tests, results consistent with the hardness values were obtained. It was understood in the light of the results that the use of high carbon ferro-chromium 20 wt.-% in a submerged arc welding flux mixture may be useful in improving hardness and wear properties of Hardox steels through hardfacing welding processes.
Hardfacing deposition processes were carried out using unalloyed S1-EL12 welding wire and submerged arc welding fluxes produced by agglomerated method containing 4-16 wt.% ferrochromium and 2 wt.% ...ferroboron to achieve wear-resistant of hardfacing deposits on common steel substrates via submerged arc welding. Typical parameters such as slag detachment behaviour, measurements of weld seam widths and heights, microstructural examinations, and hardness and wear tests of hardfacing deposits were characterized. End of the characterization processes, with the increase of chromium, carbon, and boron transition from welding fluxes to hardfacing deposits, the welding seam widths, and heights were determined to increase from 14.12 mm to 15.65 mm and 6.14 mm to 6.50 mm, respectively. Besides; carbide and boro-carbide ratios in the microstructures increased, the hardness values increased from 43 HRC to 61 HRC and the wear losses decreased from 5.79 to 4.43. (10 –7 mm 3 (N m) –1).
Acicular ferrite (AF) can significantly improve the mechanical properties of steel welds. One practical approach to enhance the formation of AF is to provide the heterogonous nucleation sites such as ...Ti oxides. In this study, Ti was added to different conventional welding processes including shield metal arc welding (SMAW), submerged arc welding (SAW) and tandem SAW (T-SAW). In the SMAW process, TiO
2
particles as a source of Ti were inserted into the weld groove, while in the SAW and the T-SAW processes, the Ti-enriched S2MoTB wire was used as the filler metal. The microstructural evolution of weldments was characterized by employing optical and scanning electron microscopes. In addition, microhardness (Vickers, HV), Charpy impact and tensile tests were carried out to investigate the mechanical properties of weldments. Although the microhardness measurements of all weldments did not vary significantly and were in the range of 205-252 HV, there was a considerable difference in tensile and impact properties of the SAW and the T-SAW weldments. In the SMAW process, the addition of TiO
2
results in no significant enhancement in tensile and impact toughness. This can be attributed to the inhomogeneous distribution of TiO
2
particles as well as the formation of large inclusions in the structure. On the other hand, Ti addition to WM increased the yield strength from 489 to 552 MPa for the SAW process, and in contrast, it decreased the impact toughness from 75 to 33 J. This detrimental effect can be related to the higher deposition of other alloying elements in the WM and the formation of more ferrite side plate phase. By applying the T-SAW process, more Ti in WM led to a higher content of AF in the microstructure and increased both yield strength and impact toughness from 528 to 595 MPa and 100 to 180 J, respectively.
The thermal cycles that high strength low alloy (HSLA) low carbon steels experience during welding inevitably affect the microstructure and mechanical properties of the weld joints. It is generally ...agreed that the coarse-grained heat affected zone (CGHAZ) and the intercritical reheated coarse-grained heat affected zone (ICRCGHAZ) in one-pass and multi-pass welding, respectively, have the poorest microstructure and mechanical properties relative to the rest of the steel joint. The martensite-austenite (M-A) constituents formed in the HAZ regions predominantly govern property deterioration in the CGHAZ and the ICRCGHAZ by promoting the initiation and propagation of micro-cracks. However, the characteristics of the M-A constituents, i.e., fraction, size, shape and aspect ratio, are strongly affected by the welding heat input. Accordingly, in this study, the aim was to evaluate the influence of a cold wire addition in conventional tandem submerged arc welding (TSAW + cold-wire) on the microstructure and micro-hardness in the CGHAZ and ICRCGHAZ. Microstructural characterization showed that a lower fraction of finely distributed M-A constituents associated with smaller prior austenite grains (PAGs) formed in the CGHAZ of the steel welded by the TSAW + cold-wire process (CW-OD weld) relative to that welded by the conventional TSAW process (TW-OD weld). Furthermore, the fraction of M-A constituents in the ICRCGHAZ of the CW-OD weld was decreased. A higher fraction of slender shaped M-A constituents in the ICRCGHAZ of the TW-OD weld resulted in an increase in the micro-hardness. The microstructure and micro-hardness changes associated with cold wire addition were attributed to the lower welding heat input and, consequently, the faster cooling rate with a corresponding reduction in the retention time in the austenitic region and ferrite/austenite region in the CGHAZ and ICRCGHAZ regions, respectively.
•The influence of cold wire addition to the tandem submerged arc welding process on the ICRCGHAZ is investigated.•Comprehensive characterization of the microstructure and micro-hardness in the ICRCGHAZ of a HSLA steel is performed.•A lower fraction of finely distributed M-A formed in the ICRCGHAZ of TSAW + cold wire steel, leading to lower micro-hardness.•The aspect ratio and inter-particle spacing of M-A constituents decreased in the ICRCGHAZ through cold wire addition.
In this study, we investigated the microstructure and properties of hardfacing coatings produced using Submerged Arc Welding (SAW) process. Powder mixtures of ferro-chrome powder, cast iron chip or ...stainless steel shot were used as alloying source to form Fe–Cr–C coating. Modified alloys were also produced by the addition of boron-containing powder to partially or fully replace carbon in the carbide-based coatings. Microstructural examination of produced samples showed the formation of carbides and borides of different morphologies which were best interpreted as microstructures of undercooled alloys. Abrasive wear and impact testing were also performed on the coatings as a measure of process effectiveness. By adjusting the amount of powder input and process variables, hypoeutectic, eutectic and hypereutectic alloys were successfully produced.
•Hypoeutectic, eutectic and hypereutectic microstructures of iron-based coatings are produced using submerged arc welding.•Hypereutectic microstructures represent the structure of undercooled alloys.•The coatings show uniform wear resistance at the surface and 75% depth.•Good impact properties can be due to selected chemical composition of alloy.
Abstract In the welding process of medium-thick plates, it is common to create grooves and perform double-sided multi-pass welding. However, this approach leads to low welding efficiency and high ...costs. Hence, this study utilizes a groove-free, double-sided double-pass welding method to enhance welding efficiency and decrease shipbuilding expenses. A finite element model of groove-free submerged arc welding for medium-thick plates was established using SolidWorks software, and mesh division was carried out. Subsequently, numerical simulations of high-voltage, high-current double-sided double-pass submerged arc welding for medium-thick plates were conducted using Simufact Welding software. In the simulation, a mobile double ellipsoid heat source was utilized to replicate the dynamic alterations throughout the entire welding process. Subsequently, the temperature field of the welded material was computed. Finally, utilizing the temperature field results, the residual stress distribution within the welded material was computed through the thermal-structural coupling feature. The simulation results revealed a significant temperature gradient at the center of the heat source during the welding process, with a slower temperature change observed behind the heat source. Around 4000 seconds, the weldment cooled to room temperature. At this point, the thermal stress mainly concentrated around the weld seam. This numerical welding simulation serves as a crucial reference for designing welding process parameters and researching residual stress distribution. Consequently, it enhances welding efficiency in the field of shipbuilding.
