Robotic Gas Metal Arc Welding Research Articles

An artificial intelligence system for quality level–based prediction of welding parameters for robotic gas metal arc welding

An artificial intelligence system for quality level–based prediction of welding parameters for robotic gas metal arc welding

Effect of Position of Robotic Gas Metal Arc Welding on Bead Quality and Multi-objective Optimization Through Gray Relational Analysis

Effect of Position of Robotic Gas Metal Arc Welding on Bead Quality and Multi-objective Optimization Through Gray Relational Analysis

Evaluation of Austenitic Stainless Steel ER308 Coating on H13 Tool Steel by Robotic GMAW Process

Within the drilling, petrochemical, construction, and related industries, coatings are used to recover components that failed during service or to prevent potential failures. Due to high stresses, such as wear and corrosion, which the materials are subjected to, industries require the application of coating between dissimilar materials, such as carbon steels and stainless steels, through arc welding processes. In this work, an austenitic stainless steel (ER308) coating was applied to an H13 tool steel substrate using the gas metal arc welding (GMAW) robotic process. The heat input during the process was calculated to establish a relationship between the geometry obtained in the coating and its dilution percentage. Furthermore, the evolution of the microstructure of the coating, interface, and substrate was evaluated using XRD and SEM techniques. Notably, the presence of martensite at the interface was observed. The mechanical behavior of the welded assembly was analyzed through Vickers microhardness, and a pin-on-disk wear test was employed to assess its wear resistance. It was found that the dilution percentage is around 18% at high heat input (0.813 kJ/mm) but decreases to about 14% with reduced heat input. Microhardness tests revealed that at the interface, the maximum value is reached at about 625 HV due to the presence of quenched martensite. Moreover, increasing the heat input favors wear resistance.

Characterization of Fillet Welded Armor Steel Performed by Robotic Gas Metal Arc Welding: Effect of Heat Input on Microstructure and Microhardness

Characterization of Fillet Welded Armor Steel Performed by Robotic Gas Metal Arc Welding: Effect of Heat Input on Microstructure and Microhardness

Behaviour of high strength steel butt joints exposed to arctic low temperatures

The present study investigated the tensile behaviour of high strength steel (HSS) butt joints exposed to arctic low temperatures. Two HSS grades, namely Q890 and Q960, with thicknesses of 6 mm and 8 mm, were employed. Single-V-groove butt joint specimens were fabricated by means of robotic gas metal arc welding using 1.2 mm-diameter ER100S-G and ER120S-G feedstock wires. The single-V-groove and butt joint tensile specimens were designed according to the Structural Welding Code-Steel AWS D1.1. Metallographic observations and Vickers hardness tests were performed on five series of HSS butt joint. Moreover, a total of 25 butt joint specimens were tested under uniaxial tension in a liquid nitrogen cooling chamber, with temperatures ranging from -75 °C to 25 °C. The stress-strain histories, tensile strengths and failure modes of the HSS butt joints exposed to arctic low temperatures are fully reported. The influence of low temperature exposure, parent steel grade and weld material selection on the tensile behaviour of the HSS butt joints is discussed. Based on the test results, recommendations for weld material matching for Q890 and Q960 HSS butt joints are provided. Additionally, prediction equations for HSS butt joint strengths exposed to arctic low temperatures are proposed using the best subset regression analysis. The findings from this study contribute to a better understanding of the behaviour of HSS butt joints under arctic low temperatures, and can be used to inform design and fabrication practices of HSS structures in cold environments.

Cold‐formed steel T‐joints with semi‐oval hollow section chord: Experimental insight and finite element modelling

AbstractExperimental study and finite element modelling of cold‐formed steel T‐joints with semi‐oval hollow section (SOHS) chord are presented. The rectangular or square hollow section (RHS/SHS) brace was welded to the flat flange of SOHS chord by robotic gas metal arc welding. Twelve SOHS T‐joints with brace‐to‐chord width ratio β from 0.29 to 0.89 were tested with the chord simply supported and the brace axially compressed. The joint strengths, failure modes and load‐deformation responses are discussed. The feasibility of the current design provisions in the CIDECT and Eurocode 3 initially developed for RHS T‐joints was examined. Generally, the predictions by these design methods are quite conservative for T‐joints with cold‐formed steel SOHS chord. In addition, a finite element model was developed to simulate the cold‐formed steel T‐joints with semi‐oval hollow section chord. Details of numerical model, including element type and mesh size as well as heat affected zone and cold‐working effect considerations, are described. The model was verified against the test results in terms of joint strength and load‐deformation response.

Investigation of Hardfacing on Ultra-High Strength Steel Base Material

The application of high-strength steels is increasing rapidly nowadays, and steels with more than 1000 MPa yield strength are usually used in welded structures. The welding of these materials has many difficulties, so very important the precise technology planning, and disciplined work during welding. The weldability of these materials is commonly investigated field in case of joining. The application of ultra-high strength steels expands rapidly, and in the last years, it started to use them as a base material for hardfacing. Besides the wearing, there is a claim about higher strength of base materials in case of relatively extremely loaded machines. Because this ultra-high strength steel appears as a base material for hardfacing and it brings new challenges for welding technologists. In case of joining, the welding technology is complicated, usually need preheating before welding, is important to calculate and to use the right t8/5 cooling time, and basically necessary to decrease the heat input as much as possible. The bad effect of welding heat input can be compensated by the filler material too in some cases. In contrast in case of hardfacing the base material itself usually has a big thickness, and no joint preparation, additionally important to reach deep fusion on the surface. It basically determines the heat input which has a different heat cycle as in case of joining. Therefore, the heat affected zone (HAZ) differs from the HAZ in case of joining application. In this investigation, four different hardfacing were made with four different technological parameters by robotic gas metal arc welding on S1100QL steel. During the welding parameter determination, we try to find a series of heat inputs from the lowest to the practically usable highest heat input. For the experiments, two filler materials used, one for the buffer zone, and for the hardfacing itself. Microstructural evaluation and hardness tests were made on the specimens which can show the differences between the heat affected zones.

Static strengths of cold-formed steel elliptical hollow section X-joints

The newly emerged elliptical hollow section (EHS) has a vast of structural and architectural merits and is favorable for engineers and designers. This paper presents an experimental investigation concerning the structural behavior of cold-formed steel EHS X-joints. Thirty elliptical hollow section X-joints with three different brace-chord orientations were carefully designed, fabricated by robotic gas metal arc welding and tested with the braces axially compressed. The width ratio between brace and chord (β) ranged from 0.29 to 1. The brace-to-chord thickness ratio (τ) ranged from 0.58 to 1.83 and the chord width-to-thickness ratio (2γ) ranged from 10.1 to 52.6. The static strengths, failure modes and load-deformation responses are discussed. The current codified design provisions do not cover the design of cold-formed steel elliptical hollow section X-joints investigated in this study. As the performance of EHS lies between the circular and rectangular hollow sections, the feasibility of the design provisions initially calibrated for conventional X-joints as specified in the CIDECT and Eurocode 3 with incorporation of equivalent section methods as well as the design recommendations previously proposed for hot-rolled steel elliptical joints was evaluated. In general, these design methods provide accurate strength predictions for cold-formed steel elliptical hollow section X-joints. Nevertheless, the scattering of predictions is still a concern and the design method shall be further improved.

Tests of Cold-Formed Steel T-Joints with Semi-Oval Hollow Section Chord

This paper presents a test campaign concerning the structural behavior of cold-formed steel T-joints with semi-oval hollow section (SOHS) chord. Three different sizes of SOHS and nine different sizes of rectangular hollow sections (RHS) or square hollow sections (SHS) were employed as chord and brace members, respectively, to fabricate the T-joint specimens. Robotic gas metal arc welding was adopted to connect the RHS/SHS brace to the flat flange of SOHS chord. The width ratio between brace and chord (β) ranged from 0.29 to 0.96. The brace-to-chord thickness ratio (τ) ranged from 0.46 to 0.72, and the chord width-to-thickness ratio (2γ) ranged from 10.3 to 13.9. A total of 29 T-joint specimens were tested with the chord simply supported and the brace axially compressed. The joint failure strengths, load-deformation histories, and failure characteristics of cold-formed steel T-joints with a SOHS chord are presented and discussed. The behavior of T-joints with a SOHS chord resembled that of RHS/SHS T-joints because the brace was connected to the SOHS chord at the flat flange. The feasibility of the design provisions in current standards initially developed for RHS T-joints was examined. The comparisons demonstrate that the strength predictions by the current standards are quite conservative for T-joints with cold-formed steel SOHS chord. The possible reasons for conservatism in design strength predictions are analyzed and discussed.

The effect of heat input in multi-pass GMAW of S960QL UHSS based on weaving and stringer bead procedure on microstructure and mechanical properties of HAZ

Quenched and tempered S960QL (yield strength ≥ 960 MPa) ultra-high strength steel (UHSS) thick plates were joined by multi-pass robotic gas metal arc welding (GMAW) using weaving and stringer bead techniques. The effects of microstructural changes in heat-affected zone (HAZ) of the joint on toughness and hardness were examined. Weaving and stringer bead techniques applied for the multi-pass welding procedure altered average peak temperatures and exposure time to those temperatures. Mechanical properties of HAZs were evaluated by utilizing notch impact and hardness tests, and these results were correlated with microstructural characterizations using optical (OM) and scanning electron microscopes (SEM). Prior austenite grain (PAG) coarsening occurred because of increased exposure time to peak temperature in coarse-grained HAZ (CGHAZ) of the W-5 (weaving pass) joint. CGHAZs at the face pass, which have not been subjected to a second thermal cycle, have the highest hardness in both joints. Hardness of SCHAZ and CGHAZ of S-12 joint was 7% and 1% higher compared with W-5 joint, respectively. Weld metal hardness of W-5 joint was 15% lower than that of S-12 joint. Both joints not only fulfilled the requirements of minimum 50 J per EN ISO 10025-6 at −20 °C but exceeded this limit by 50% (W-5) and 200% (S-12). Lateral expansions for impact toughness specimens were around 17.5% for S-12 joint, whereas it was 4% for W-5 joint. Since HAZ in the S-12 (stringer bead) joint is narrow compared with the one in the W-5 joint, impact toughness values were higher with the S-12 joint due to the locations of the notches of the impact specimens.

Possibilities of Artificial Intelligence-Enabled Feedback Control System in Robotized Gas Metal Arc Welding

In recent years, welding feedback control systems and weld quality estimation systems have been developed with the use of artificial intelligence to increase the quality consistency of robotic welding solutions. This paper introduces the utilization of an intelligent welding system (IWS) for feedback controlling the welding process. In this study, the GMAW process is controlled by a backpropagation neural network (NN). The feedback control of the welding process is controlled by the input parameters; root face and root gap, measured by a laser triangulation sensor. The NN is trained to adapt NN output parameters; wire feed and arc voltage override of the weld power source, in order to achieve consistent weld quality. The NN is trained offline with the specific parameter window in varying weld conditions, and the testing of the system is performed on separate specimens to evaluate the performance of the system. The butt-weld case is explained starting from the experimental setup to the training process of the IWS, optimization and operating principle. Furthermore, the method to create IWS for the welding process is explained. The results show that the developed IWS can adapt to the welding conditions of the seam and feedback control the welding process to achieve consistent weld quality outcomes. The method of using NN as a welding process parameter optimization tool was successful. The results of this paper indicate that an increased number of sensors could be applied to measure and control the welding process with the developed IWS.

Experimental investigation on cold-formed steel elliptical hollow section T-joints

A test campaign on cold-formed steel elliptical hollow section T-joints with the chord simply supported and the brace axially compressed is described in this paper. Four different sizes of elliptical hollow sections with the section aspect ratio ranged from 1.65 to 3 were employed to fabricate the T-joint specimens. Thirty-one T-joint specimens with three different types of member orientations were considered. Robotic gas metal arc welding was adopted to fabricate the elliptical hollow section T-joint specimens. The width ratio between brace and chord (β) ranged from 0.29 to 1. The brace-to-chord thickness ratio (τ) ranged from 0.60 to 1.77 and the chord width-to-thickness ratio (2γ) ranged from 10.6 to 52.3. All the T-joint specimens were tested with the chord simply supported and the brace axially compressed. The load-carrying capacities, load-deformation responses and failure modes of the elliptical hollow section T-joints are presented and discussed. Since no codified design provision is available for elliptical hollow section T-joints investigated herein, the feasibility of the design provisions originally developed for tubular T-joints with conventional cross-sections (i.e. circular hollow section and rectangular hollow section) as specified in the CIDECT and Eurocode 3 as well as the design recommendations proposed for hot-rolled steel elliptical joints was examined. Comparison results indicate that the joint strength predictions via these design methods are quite conservative and scattered for cold-formed steel elliptical hollow section T-joints.

Corrosion Resistance of GMAW Duplex Stainless Steels Welds.

The hydrocarbon industry constantly requires a better understanding of stainless-steel welding metallurgy. Despite the fact that gas metal arc welding (GMAW) is one of the most commonly employed welding processes in the petrochemical industry, the process is characterized by the presence of a high number of variables to control in order to obtain components that are dimensionally repeatable and satisfy the functional requirements. In particular, corrosion is still a phenomenon that highly affects the performance of the exposed materials, and special attention must be paid when welding is applied. In this study, the real operating conditions of petrochemical industry were reproduced through an accelerated test in a corrosion reactor at 70 °C for 600 h, exposing robotic GMAW samples free of defects with suitable geometry. The results show that, even if duplex stainless steels are characterized for being more corrosion resistant than other stainless steels, under these conditions it was possible to identify microstructural damage. In detail was found that the corrosion properties were strongly related to the heat input during welding and that the best corrosion properties can be obtained with the higher heat input.

Mechanical properties of high strength steels and weld metals at arctic low temperatures

This paper attempts to acquire fundamental knowledge on the mechanical properties of high strength steels and the corresponding high strength weld metals at arctic low temperatures. Two types of high strength steels (Q890, Q960) and three types of high strength weld metals (made of ER100S-G, ER110S-G, ER120S-G feedstock wires) were tested at arctic low and ambient temperatures ranging from −75 °C to 25 °C. Tensile coupon specimens for steel materials were directly extracted from high strength steel plates, whilst robotic gas metal arc welding was employed to fabricate the tensile specimens of weld metals. The tensile coupon specimens were designed as per ASTM E8M and wire-cut into shapes. Twenty-three tensile coupon tests on high strength steels and eighteen tensile coupon tests on high strength weld metals were carried out. Coupon specimens were tested in liquid nitrogen cooling chamber to mimic the arctic low temperature environment. The stress–strain responses and key mechanical properties of high strength steels and weld metals at both ambient and arctic low temperatures are presented and discussed. Prediction equations for key mechanical properties, including the Young’s modulus, yield stress and ultimate tensile strength, of high strength steels and weld metals at arctic low temperatures were proposed.

Microstructure and electrochemical evaluation of ER-308L weld overlays on AISI 321 stainless steel for repair applications

Weld overlaying is a promising and economical solution for repairing stainless steel structures. The present work deals with the deposition of ER-308L weld overlays on AISI 321 plate with Robotic gas metal arc welding setup. Microstructural examination depicts the presence of dendritic structures (equiaxed and columnar) and ferritic stringers. Energy-dispersive X-ray analysis confirmed the absence of precipitates and phases susceptible to corrosion in the as-deposited weld overlays. Specimens from ER-308L (weld overlay) and ER-308L&321-SS (interface) regions were subjected to electrochemical analysis using the Potentiodynamic polarization and double-loop electrochemical potentiokinetic reactivation measurements. Both overlay and interface sections exhibited comparable corrosion rate – 3.30 and 3.62 mils penetration per year, respectively with different passivation behaviour. The improved passivation behaviour of the ER-308L weld overlay authenticates the presence of δ-ferrite stringers. Double-loop electrochemical potentiokinetic reactivation tests highlighted the absence of sensitization on both weld overlay and interface specimens. This study presents the initial assessment results for repairing structural steel components subjected to corrosion damage.

Heterogeneous Measurement System for Data Mining Robotic GMAW Weld Quality

During robotic welding, several streams of heterogeneous data can be collected. To gain a systemic understanding of the welding process, these data streams have to be combined precisely and accurately, especially if our goal is to develop online weld quality assessments. Establishing correspondence among temporal and spatially based data is a nontrivial effort. This article presents a data collection system using a novel methodology for establishing correspondence across multiple data sources of robotic gas metal arc welding for objective quality assessment. First, correspondence between the weld process data and the resulting weld required time synchronization and spatial alignment. Second, an objective weld quality extraction technique that assigns quantitative measures at a resolution of 1 mm of linear weld travel was developed to evaluate weld quality. Specifically, in addition to developing a method for objective weld profile assessment, we developed an objective analysis of radiographic data for the occurrence of subsurface porosity to assess defects and demonstrate how to objectively quantify the occurrence of surface porosity. While some aspects of this paper have been addressed individually and separately by other research, this paper presents an integrated approach to these operations for a wide variety of weld data types and develops objective weld quality metrics that can be used for machine learning of weld quality for robotic welding.

Laser ultrasonic inspection of defects in wire arc additive manufactured samples with different surface profiles

The laser ultrasonic (LU) technique has the advantages of a wide frequency band, small non-detection zone, high resolution and non-contact compared to conventional ultrasonic testing, which makes it potential for on-line inspection of the wire arc additive manufacturing (WAAM) process. To investigate the influence of surface profile on the LU inspection of WAAM defects, multiscale analysis was adopted in the mathematical characterization of the sample surface profile. Finite Element (FE) models of LU inspection of WAAM defects with different surface profiles were established using COMSOL software. The propagation of acoustic waves and their interaction with surface profile and defects were numerically analyzed. The LU inspection methods, that is, superficial crack detected by through-transmission of Rayleigh wave and internal hole detected by pulsed-echo of shear wave were put forward. A set of WAAM samples with different surface topographies was manufactured by the robotic gas metal arc welding (GWAM) system through varying the process parameters and filler materials. LU inspection experiments were conducted to obtain B-scan images and A-scan signals of the defects in these samples. The experimental results indicate that surface roughness has a significant effect on the signal-to-noise ratio (SNR) of internal through hole detection, and surface waviness has a significant effect on the sensitivity of superficial crack detection. The experimental results are consistent with the numerical results, which validate the proposed FE model. The proposed FE model can be used for the quantitative study of the influence of WAAM sample profile on the LU inspection. Furthermore, it is also a guidance for the formulation of key process parameters in LU inspection, such as the maximum generating-receiving laser distance and the laser’s layout. At last, a robotic LU inspection system was built and preliminarily achieved the automatic inspection of a WAAM part. This research provides a theoretical basis for the on-line application of LU techniques in WAAM process monitoring.

Additive remanufacturing of coupler knuckle based on robotic gas metal arc welding

Take the wear parts of coupler knuckle as an example, the “Modeling—Slicing — Stacking” mode remanufacturing process is studied. First, the 3D model of the of the worn coupler knuckle surface is acquired by structured light 3D detection. The remanufacturing model of the failure part is built by Boolean operation between the original model and the acquired 3D model. Second, the user can slice layer of the remanufacturing model according to the remanufacturing stacking parameters. The zone that surrounded by the contour of each sliced layer is the robotic GMAW remanufacturing stack region. Third, the robotic GMAW remanufacturing path is planed within the region mentioned above and the executable program is generated to carry out the remanufacturing task layer by layer. Moreover, the worn coupler knuckle was repaired by adopting Robotic GMAW Process. The mechanical performances of component were tested, the results indicate that the remanufactured coupler knuckle satisfying the operating requirements.

Prediction of Mechanical Properties as a Function of Welding Variables in Robotic Gas Metal Arc Welding of Duplex Stainless Steels SAF 2205 Welds Through Artificial Neural Networks

Abstract Dual-phase duplex stainless steel (DSS) has shown outstanding strength. Joining DSS alloy is challenging due to the formation of embrittling precipitates and metallurgical changes during the welding process. Generally, the quality of a weld joint is strongly influenced by the welding conditions. Mathematical models were developed to achieve high-quality welds and predict the ideal bead geometry to achieve optimal mechanical properties. Artificial neural networks are computational models used to address complex nonlinear relationships between input and output variables. It is one of the powerful modeling techniques, based on a statistical approach, presently practiced in engineering for complex relationships that are difficult to explain with physical models. For this study robotic GMAW welding process manufactured the duplex stainless steel welds at different welding conditions. Two tensile specimens were manufactured from each welded plate, resulting in 14 tensile specimens. This research focuses on predicting the yield strength, tensile stress, elongation, and fracture location of duplex stainless steel SAF 2205 welds using back-propagation neural networks. The predicted values of tensile strength were later on compared with experimental values obtained through the tensile test. The results indicate <2% of error between observed and predicted values of mechanical properties when using the neural network model. In addition, it was observed that the tensile strength values of the welds were higher than the base metal and that this increased when increasing the arc current. The welds’ yield strength and elongation values are lower than the base metal by 6%, ~ 9.75%, respectively. The yield strength and elongation decrease might be due to microstructural changes when arc energy increases during the welding.

Stress concentration factors of cold-formed high strength steel tubular T-joints

A test programme looking into the stress concentration factors (SCF) of cold-formed high strength steel (CFHSS) traditional (without brace and/or chord rotation) and member-rotated tubular T-joints is described in this paper. The brace members of traditional T-joints were made of square, rectangular and circular hollow sections (SHS, RHS and CHS), while the brace members of member-rotated T-joints were made of SHS and RHS. On the other hand, the chord members of traditional and member-rotated tubular T-joints were made of SHS. In this study, member-rotated T-joints, include brace-rotated (BR), square bird-beak (SBB) and diamond bird-beak (DBB) tubular T-joints. The tubular members were cold-formed from thermomechanical control processed (TMCP) S900 and S960 steel grades plates. A total of 12 tests was conducted in this experimental investigation. An axial compression load was applied through the brace member, while the chord ends were supported on rollers. The brace and chord members of tubular T-joints were connected using the robotic gas metal arc welding process. The values of normal brace width-to-chord width ratio (β) ranged from 0.33 to 0.73, effective brace width-to-chord width ratio (β’) ranged from 0.40 to 0.87, brace thickness-to-chord thickness ratio (τ) ranged from 0.66 to 1.28 and chord width-to-chord thickness ratio (2γ) ranged from 20.6 to 39.0. The quadratic extrapolation method was used to estimate hot spot strains at the weld toes using the strains measured in the extrapolation regions. The experimental SCF values of CFHSS traditional and member-rotated tubular T-joints were compared with the SCF values obtained from the parametric equations given in the CIDECT (Zhao et al., 2001, [1]) and studies (Tong et al., 2013, [2]; Li et al., 2018, [3]; Tong et al., 2015, [4]). It was found that the existing SCF parametric equations given in the literature (Zhao et al., 2001, [1]; Tong et al., 2013, [2]; Li et al., 2018, [3]; Tong et al., 2015, [4]) could not accurately predict the SCF of cold-formed traditional and member-rotated tubular T-joints made of S900 and S960 steel grades.