Double-sided Arc Welding Process Research Articles

Investigation of angular deformation control for T-joint rib using multi-point constraint method

The circular rib is a crucial component of large pressure vessels, and its cross-section is primarily a T-joint structure. The double-sided arc welding (DSAW) process is an advanced technology for T-joint connection. However, during the T-joint welding process, harmful deformation still occurs in the form of angular deformation, including web and flange angular deformation. This paper proposes an innovative multi-point array constraint method to control the angular deformation of the rib based on the DSAW process for circular ribs. The welding deformation of the T-joint rib under multi-point constraints is studied using both numerical and experimental methods. The results of the numerical and experimental are consistent, with a relative error of no more than 12%. The multi-point constraint method is found to control angular deformation effectively, with the maximum angular deformation of the web not exceeding 1.77 mm and that of the flange not exceeding 0.45 mm after welding and releasing the constraint. The deformation control is significantly better than that of the rigid jig. Moreover, the coupling deformation of the web and flange caused by double-sided heat source and multi-point constraint forms an overall bending deformation. The deformation trend of each welding process is the same, with the main deformation occurring in the stage of releasing the constraint.

Butt brazing of titanium alloys/stainless steel plates by MIG-TIG double-sided arc welding process with copper filler metal

Butt brazing of titanium alloys with stainless steel by MIG-TIG double-sided arc welding (DSAW) process with copper filler metal has been performed. The microstructures and mechanical properties of the joint were investigated. The results show that a butt brazing joint with sound double-sided appearance was achieved. With low heat input of brazing mode and rapid cooling rate of arc welding process, the joint is free of brittle Ti-Fe intermetallic compounds (IMCs). The phase compositions in the joint are TC4/Ti2Cu+TiCu/TiCu+Ti5Si3/Cu+(Ti5Si3+Cu+βTiCu4)/Fe5Si3+(Cu)+FeSi/Fe(s,s)/304ss orderly from Ti6Al4V to 304ss. The average tensile strength of the butt joint reaches 278MPa. Compared with the fusion welding joint, the tensile strength of the arc-brazing joint is significantly increased because of the elimination of Ti-Fe IMCs.

Double sided arc welding of AA5182 aluminium alloy sheet

The feasibility and merits of using the double sided arc welding (DSAW) process for making square welds in 1˙2 mm thick AA5182-O aluminium sheets in the butt-joint configuration for applications such as tailor welded blanks (TWB) has been studied. Full penetration, conduction mode DSAW welds were made using a balanced square wave AC, constant current power supply at welding speeds of 30 to 40 mm s–1 when using 2˙1 kW welding power and between 40 and 60 mm s–1 when using 3˙4 kW welding power. There was good cathodic cleaning of the oxide on both sides of the sheet and the weld bead quality and properties were excellent. All welds exhibited a columnar to equiaxed grain transition with up to 40% equiaxed grain area. The DSAW process was found to be capable of producing welds of equal or better quality and at comparable welding speeds to those produced using more traditional welding processes for TWB applications.

Numerical simulation of dynamic development of keyhole in double-sided arc welding

Double-sided arc welding (DSAW) is a novel process for joining metals that is capable of achieving deep narrow penetration in a single pass with minimized distortion. A clear understanding of the process fundamentals is critical in order to fully examine the potential of DSAW, to guide the further developments of the process, to direct the practicability study, and to design the process parameters. This paper aims at developing a numerical model for examining and simulating the dynamic keyhole establishment process, which will be a key in developing an effective control technology for DSAW. The model is used to determine the geometrical shape of the keyhole and the weld pool, and the temperature distribution in the workpiece. Quantitative information on the establishment of the keyhole in DSAW, such as the transient development of the keyhole and the weld pool, the increase rate of the depth of the surface depression, the time interval from full penetration to the keyhole establishment, the minimum span of the weld pool for describing the conditions required to complete the keyhole establishment, and variation of the overflow height of the weld pool surface on the plasma arc welding side, has been obtained through numerical analysis. The DSAW experiments show that the predicted weld cross-section is in agreement with the measured one. The results lay a foundation for guiding the further development of the DSAW process and its effective control.

Numerical analysis of temperature field during double-sided arc welding of thick materials

Double-sided arc welding (DSAW) is a novel arc process developed at the University of Kentucky in which the workpiece is disconnected from the power supply and the two torches are used to establish two arcs on the both sides of the workpiece to close the current loop. As a result, the welding current is forced to flow through the workpiece along the thickness direction. This configuration and current flow direction improve the concentration of the arc energy distribution and provide a mechanism to guide the arc into the keyhole. Hence, DSAW process is capable of achieving deep narrow penetration and symmetrical welds. However, despite the progress in process development, there is a lack of a clear understanding of the physical processes and phenomena occurring in the weldment. In this study, a numerical model is developed to compute the temperature field and history in double-sided arc weldment. Using this numerical model, the temperature distributions and profiles at different cross-sections and along different lines of interest have been computed and compared with the results in regular plasma arc welding. It was found that DSAW process has advantages in obtaining deep narrow penetration, in producing symmetrical hour glass-shaped welds, in reducing the sensitization zone, in lowering the temperature gradient along the thickness, thus lowering the thermal distortion and residual stress, and in decreasing the sensitization duration.

Sensing and Control of Double-Sided Arc Welding Process

The welding industry is driven to improve productivity without sacrificing quality. For thick material welding, the current practice is to use backing or multiple passes. The laser welding process, capable of achieving deep narrow penetration, can significantly improve welding productivity for such applications by reducing the number of passes. However, its competitiveness in comparison with traditional arc welding is weakened by its high cost, strict fit-up requirement, and difficulty in welding large structures. In this work, a different method, referred to as double-sided arc welding (DSAW) is developed to improve the arc concentration for arc welding. A sensing and control system is developed to achieve deep narrow penetration under variations in welding conditions. Experiments verified that the pulsed keyhole DSAW system developed is capable of achieving deep narrow penetration on a 1/2 inch thick square butt joint in a single pass.

Stochastic modelling of plasma reflection during keyhole arcwelding

Keyhole arc welding (KAW), including the keyhole double-sided arcwelding process being developed at the University of Kentucky and keyholeplasma arc welding, can achieve much deeper narrower penetration than allother arc welding processes. If it could be controlled such that the heatinput and weld pool are minimized while at the same time the desired fullpenetration is guaranteed, it could become an effective yet affordabletechnology to improve productivity in welding thick materials. However, thekey in developing such a controlled KAW technology is the sensor which candetect the evolution of the keyhole. Preliminary study shows that the plasmareflection could lead to a practical yet accurate sensor. In this study, thedynamic behaviour of the plasma reflection is described using the reflectionarc angle (RAA). It is found that the RAA series can be considered anautoregressive moving-average (ARMA) process. The orders of the ARMA model aredetermined using auto-correlation and partial auto-correlation functions. Theparameters of the ARMA are recursively estimated using the extended leastsquares algorithm. It is found that the recursive estimates of the modelparameters change as the state of the keyhole changes. A discriminator hasbeen proposed to determine the state of the keyhole based on the recursiveestimates of the model parameters.

Welding of austenitic stainless steel using double sided arc welding process

This study explores an improved method of welding austenitic stainless steel. The method uses two series connected arcs to weld the workpiece simultaneously from opposite sides. Owing to this arc configuration, the welding current is forced to flow from one arc to the other through the workpiece. It is known that such current flow concentrates the arcs and thus improves the penetration capability. Also, the current flowing through the workpiece generates fluid flow within the weld pool. In addition, owing to the use of the two opposite arcs, the heating tends to be symmetric. In addition to the increased penetration, the use of this method for welding austenitic stainless steel results in improved microstructure in the resultant welds because of an increased columnar to equiaxed transition and a decreased angular distortion, which sometimes induces solidification cracking.

Improved microstructure and properties of 6061 aluminum alloy weldments using a double-sided arc welding process

Due to its popularity and high crack sensitivity, 6061 aluminum alloy was selected as a test material for the newly developed double-sided arc welding (DSAW) process. The microstructure, crack sensitivity, and porosity of DSAW weldments, were studied systematically. The percentage of fine equiaxed grains in the fully penetrated welds is greatly increased. Residual stresses are reduced. Porosity in the welds is reduced and individual pores are smaller. It was also found that the shape and size of porosity is related to solidification substructure. In particular, a weld metal zone with equiaxed grains tends to form small and dispersed porosity, whereas elongated porosity tends to occur in columnar grains.

Solidification behavior of Al-Mg aluminum alloy using double-sided arc welding process

As popular aluminum alloys, the 5xxx Al-Mg series, such as 5050 and 5052, etc., are widely used in applications such as automobile, pressure vessels, armor plate, and components for marine and cryogenic service. In this, as in all non-heat-treatable aluminum alloys, the weld metal zone is considered to be the weakest part of the joint and is the location of failure when the joint is loaded in tension during welding [1]. Solidification behavior of the weld pool, which controls the microstructure of the weld metal zone, plays a critical role in determining the ultimate strength of the joint.