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Hot-rolled backup rolls are widely used in steel rolling and usually need to be repaired by arc hardfacing after becoming worn. However, a corrugated-groove defect commonly occurs on the roll surface due to the uneven hardness distribution in the hardfacing layers, affecting the proper usage of the roll. Accordingly, a new swing-arc submerged arc welding (SA-SAW) process is proposed to attempt to solve this drawback. The microstructure and hardness are then investigated experimentally for both SAW and SA-SAW hardfacing layers. It is revealed that a self-tempering effect occurs in the welding pass bottom and the welding pass side neighboring the former pass for both processes, refining the grain in the two areas. In all the zones, including the self-tempering zone (STZ), heat-affected zone (HAZ), and not-heat-affected zone in the welding pass, both SAW and SA-SAW passes crystallize in a type of columnar grain, where the grains are the finest in STZ and the coarsest in HAZ. In addition, the arc swing improves the microstructure homogeneity of the hardfacing layers by obviously lowering the tempering degree in HAZ while promoting the even distribution of the arc heat. Accordingly, the hardness of the SA-SAW bead overall increases and distributes more uniformly with a maximum difference of < 80 HV0.5 along the horizontal direction of the bead. This hardness difference in SA-SAW is accordingly decreased by ~38.5% compared to that of the SAW bead, further indicating the practicability of the new process.

To solve the problems of poor weld formation, difficult slag removal, and inferior joint microstructure and hardness in conventional narrow-gap submerged arc welding (NG-SAW), a swing arc NG-SAW process assisted by pre-embedding cold wires was proposed. Synergistically optimizing the welding energy parameters and additional cold wires ensured sound weld formation and enhanced slag detachability, while the efficiency of multilayer welding was improved by reducing the number of weld layers by 33.3%. The slag adhesion mechanism is clarified as follows: a high welding heat input facilitates elemental diffusion at the weld–slag interface, leading to the formation of a continuous and thick interlayer composed of (Fe,Mn)O and MgO-Al2O3-CaO phases. This interlayer strengthens the chemical bonding between slag and weld, thereby impeding slag removal. Microstructure evolution analysis of the multilayer welded joint revealed that the variable-angle design increases the groove volume and, combined with the heat-absorbing effect of the additional wires, accelerates molten pool cooling, thereby refining grains in both the weld metal zone and reheat-affected zone. Meanwhile, the tempering exerted by the heat-affected zone (HAZ) of the subsequent weld layer on the previous layer is attenuated. This promotes the gradual transformation of hard-brittle lath martensite in the coarse-grained heat-affected zone (CGHAZ) of the bottom layer into tougher tempered martensite/bainite in the CGHAZ of the upper layers. As a result, the hardness uniformity within the HAZ, the critical weak region of the joint, was enhanced by 54%, enabling synchronous improvement in microstructural homogeneity, hardness distribution, and overall welding efficiency.

Square butt joints were prepared using two microalloyed ASTM A572 Gr.50 steels: niobium (Type 1) and vanadium (Type 2). Both single-wire submerged arc welding (SAW) and two-wire tandem submerged arc welding (SAW-T) processes were utilized, with a constant heat input of 2.5 kJ/mm. The weld profile, microstructure, and mechanical properties were systematically analyzed for both welding processes. It was observed that the weld width, hardness, yield strength, ultimate tensile strength, and impact toughness of the welds increased with SAW-T compared to SAW. Type 1 steel weld exhibited higher acicular ferrite, 8% higher yield strength, and 5% higher ultimate tensile strength due to the intra-granular nucleation of niobium carbonitrides in austenite. In contrast, Type 2 steels displayed a 13% higher percentage of elongation, 4.3% higher hardness, and 30% higher impact toughness at 25 °C. At − 20 °C temperature, SAW-T welds show higher HAZ toughness than SAW welds. Also, Type 2 welds showed enhanced toughness compared to Type 1 welds by mitigating the pinning effect of precipitates.

This article reports on a numerical and experimental investigation to understand and improve computer methods in application of the Goldak model for predicting thermal distribution in submerged arc welding (SAW) of APIX65 pipeline steel. Accurate prediction of the thermal cycle and residual stresses will enable control of the fusion zone geometry, microstructure, and mechanical properties of the SAW joint. In this study, a new Goldak heat source distribution model for SAW is presented first. Both 2D and 3D finite element models are developed using the solution of heat transfer equations in ABAQUS Standard implicit. The obtained results proved that the 2D axi-symmetric model can be effectively employed to simulate the thermal cycles and the welding residual stresses for the test steel. As compared to the 3D analysis, the 2D model significantly reduced the time and cost of the FE computation. The numerical accuracy of the predicted fusion zone geometry is compared to the experimentally obtained values for bead-on-plate welds. The predictions given by the present model were found to be in good agreement with experimental measurements.

The alloy 2.25Cr-1Mo-0.25V is commonly used for heavy wall pressure vessels in the petrochemical industry, such as hydrogen reactors. As these reactors are operated at elevated temperatures and high pressures, the 2.25Cr-1Mo-0.25V welding consumables require a beneficial combination of strength and toughness as well as enhanced creep properties. The mechanical properties are known to be influenced by several welding parameters. This study deals with the influence of the heat input during submerged-arc welding (SAW) on the solidification structure and mechanical properties of 2.25Cr-1Mo-0.25V multilayer metal. The heat input was found to increase the primary and secondary dendrite spacing as well as the bainitic and prior austenite grain size of the weld metal. Furthermore, it was determined that a higher heat input during SAW causes an increase in the stress rupture time and a decrease in Charpy impact energy. This is assumed to be linked to a lower number of weld layers, and therefore, a decreased amount of fine grained reheated zone if the multilayer weld metal is fabricated with higher heat input. In contrast to the stress rupture time and the toughness, the weld metal’s strength, ductility and macro-hardness remain nearly unaffected by changes of the heat input.

High-manganese steel (high-Mn) is valuable for its excellent mechanical properties in cryogenic environments, making it essential to understand its deformation behavior at extremely low temperatures. The deformation behavior of high-Mn steels at extremely low temperatures depends on the stacking fault energy (SFE) that can lead to the formation of deformation twins or transform to ε-martensite or α′-martensite as the temperature decreases. In this study, submerged arc welding (SAW) was applied to fabricate thick pipes for cryogenic industry applications, but it may cause problems such as an uneven distribution of manganese (Mn) and a large weldment. To address these issues, post-weld heat treatment (PWHT) is performed to achieve a homogeneous microstructure, enhance mechanical properties, and reduce residual stress. It was found that the difference in Mn content between the dendrite and interdendritic regions was reduced after PWHT, and the SFE was calculated. At cryogenic temperatures, the SFE decreased below 20 mJ/m2, indicating the martensitic transformation region. Furthermore, an examination of the deformation behavior of welded high-Mn steels was conducted. This study revealed that the tensile deformed, as-welded specimens exhibited ε and α′-martensite transformations at cryogenic temperatures. However, the heat-treated specimens did not undergo α′-martensite transformations. Moreover, regardless of whether the specimens were subjected to Charpy impact deformation before or after heat treatment, ε and α′-martensite transformations did not occur.

Pipeline welding is an integral part of oil and gas exploration industries. Often the welded joint failures were due to lack of weld quality, improper heat treatment and even poor workmanship. Further, the use of new material in pipeline industry puts focus on a better understanding of qualifying requirements of welding for reducing the failures in future. This necessitates the need for development and design of suitable welding fluxes for joining these materials. In this paper an attempt is made to study the effects of submerged arc welding fluxes on weldability as well as structural integrity issues in pipeline steels. Physicochemical and thermophysical properties of submerged arc fluxes widely affects the mechanical behaviour of pipeline steels. This paper presents an overview of the role of welding parameters, flux composition, cooling rate, slag behaviour and physicochemical properties of slag on final welded joint properties such as tensile strength, impact toughness etc. during submerged arc welding.

In this study, two types of submerged arc welding (SAW) wires were prepared—one without cerium (Ce) and another containing 0.14 wt.% Ce. Deposition experiments were carried out on corrosion-resistant crude oil storage tank steel plates using a multi-layer, multi-pass welding process. Through a combination of microstructural characterization techniques, including optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM), along with mechanical property testing, a systematic investigation was conducted to evaluate the influence of Ce on the weld metal microstructure and its impact toughness at −20 °C. The results reveal that Ce introduced via the welding wire into the weld seam refines and disperses inclusions, leading to the formation of composite inclusions primarily composed of Ce2O3, Ce2O2S, and CeS. These Ce-enriched inclusions serve as heterogeneous nucleation sites, increasing the area fraction of acicular ferrite (AF) within the weld columnar grain region from 52% to 83%, and within the heat-affected zone from 20% to 37%. Correspondingly, the proportions of blocky and polygonal ferrite decrease, while the size of martensite/austenite (M/A) constituents is reduced. The addition of Ce thus diminishes the size of hard phase inclusions and M/A constituents in the weld metal, enhancing the critical fracture stress and increasing the energy required for crack initiation. Meanwhile, the higher proportion of AF elevates the density of high-angle grain boundaries, thereby improving crack propagation resistance. These combined effects raise the −20 °C impact energy of the weld metal from 117 J to 197 J.

In a hydrogen production reactor based on the principle of coal-to-hydrogen, the welds, which are considered the weak points, must exhibit a good impact resistance property and high hardness under special operating conditions. This paper investigates the influence of submerged arc welding (SAW) process parameters on the hardness and the impact resistance property of welds in the steel used for a hydrogen reactor. It establishes the relationship between the microstructure of the welds and their hardness and impact resistance property under varying welding parameters. Based on orthogonal welding experiments and a comprehensive balance method, the welding parameters were optimized to obtain the best combination of parameters. The results indicate that as the current and voltage increase, the average hardness of the welds first decreases and then increases, while the impact resistance property initially improves before declining. As the welding speed increases, the average hardness of the welds initially increases and then decreases, while the impact resistance property gradually declines. After optimization under specific experimental conditions, the best welding parameters are determined to be a current (I) of 320 A, a voltage (U) of 34 V, and a welding speed (v) of 33 cm/min. Compared to the base metal, the hardness of the weld increased by 36.1%, and the impact resistance property improved by 71.5%.

This article investigates the influence of process and geometric parameters on deformation during mild steel Submerged arc welding (SAW). This article focuses on optimizing welding process parameters to reduce distortion and improve product quality. The intent of this study is to investigate the effects of technical and geometrical parameters on deformation during submerged arc welding of mild steel using ANSYS and experimental values employing element type brick 8 node 70. The temperature distribution was analyzed using the double ellipsoidal heat source model developed by Goldak, and the amount of deformation was predicted by changing the plate thickness, welding speed and current. The finite element method (FEM) was used to simulate the welding process and obtain an approximate solution. ANSYS software was used for modeling and analysis. The effect of four main parameters of the series (A, B, C, D) on the distortion was analyzed. The simulation results were compared with the experimental values. The study revealed that the maximum distortion determined for SET A was 1.341 mm, corresponding to the experimental value of 1.20 mm. SET B resulted in a maximum distortion of 0.88 mm, corresponding to an experimental value of 0.60 mm. The increase in heat-input in SET C increased the strain/distortion from 1.341 to 2.989 mm, which closely matches the experimental value of 2.60 mm. Increasing the welding speed for SET D reduces the deformation from 2.989 to 2.230 mm, in good agreement with the experimental value of 2.012 mm. SET E investigated the effect of different plate thicknesses on deformation, and the thicker the plate, the lower the maximum deformation. This research can aid in the optimization of welding process parameters and the reduction of distortion in the finished product by forecasting the maximum distortion by varying these parameters. The novelty of this study lies in its investigation of the influence of various variables on the welding process and the distortion that results, which has the potential to significantly enhance the welding process and the caliber of the final product. The findings of this study can be applied in the shipbuilding and automotive industries.