Automatic Gas Metal Arc Welding Research Articles

Fracture behavior, mechanical properties, and microstructural analysis of vacuum automated GMAW welded dissimilar A353 and A516 steels for pressure vessels

In this study, the performance of the automatic gas metal arc welding (GMAW) process in vacuum for similar and dissimilar joints of A353 and A516 steel plates with different thicknesses was intensively evaluated. Fracture of all vacuum-welded samples occurred in the heat-affected zone (HAZ) of A516 steel, highlighting the significant influence of HAZ microstructure and width on the cryogenic impact energy and strength of these joints. According to microscopic observations and impact tests, the fractures were fully ductile for notches in the weld and A353 HAZ, where dimples were observed on the fracture surfaces and the impact energy exceeded 50 J. This ductile behavior is particularly significant for notches in the weld due to the presence of a vacuum during welding prevents the formation of gas voids and oxide and hydride compounds that are normally the origin of cracks. However, for notches in the A516 HAZ, where the cleavage faces were observed on the fracture surfaces and the impact energy was less than 30 J, the fractures were quite brittle. For dissimilar vacuum-welded samples, the impact energy and fracture type for notches in the weld and A353 HAZ were nearly the same as those in similar A353 joints. However, for notches in the A516 HAZ, the impact energy and fracture type were close to those observed in the A516 joints. Yield strength and ultimate tensile strength (UTS) of A353-A353 non-vacuum-welded samples compared to vacuum-welded samples decreased by more than 78% and 40%, respectively. As well as, yield strengths and UTSs of A516-A516 non-vacuum samples compared to vacuum samples decreased by more than 34% and 4%, respectively. On the other side, the impact samples with a notch position in the weld suffered brittle fracture instead of ductile fracture because their impact energy decreased by about 40%.

Desain dan Perancangan Alat Welding Holder untuk Pengelasan Pelat pada Las GMAW

One of the metal welding processes required by the manufacturing industry is gas arc welding (GMAW). The welding process that is capable of transmitting large amounts of heat at high speeds is gas electric welding or GMAW (Gas Metal Arc Welding). The design mechanism for the movement of the X and Y axes in the development of GMAW welding holders uses the stages of finding ideas, studying literature, identifying problems, designing, making tools and testing machines. The purpose of this study was to design a mechanism for moving the X and Y axes in the development of an automatic GMAW torch holder machine and to calculate the machine elements in the development of an automatic GMAW torch holder machine. The process of designing and constructing the movement of the X and Y axes in the development of an automatic GMAW welding torch holder machine is carried out with a design procedure that is used as a reference in solving problems. The track shaft uses chrome steel with a diameter of 25 mm and a length of 800 mm, Linear bearings use type SCS25UU with an inner diameter of 25 mm, Linear rail shafts use aluminum alloy material with a diameter of 25 mm which is used to support the end of the track shaft, Ballscrew uses the SFU 2005 type with a size of 3/4 inch which is equipped with a ballscrew nut and also a nut housing, Bearing block uses a UCP type with a diameter of 20 mm, Flexible coupling measuring 5 mm to 10 mm is used to connect the drive screw with the stepper motor, The stepper motor is used as the main power to drive the drive screw type Nema 17 (17HD48002H-22B) with the specifications Step Angle: 1.8o, Rated Current: 1.5 Ampere, Voltage : 2.7V.

Crack Identification and Trajectory Planning for Automatic Gas Metal Arc Welding

Gas metal arc welding process has the capability of producing high quality, all position welding, and is easily adaptable for automated welding applications. Repair welding of random cracks on existing assembly/structure through automatic welding would need real time crack/gap identification and weld path generation. In this work, an image processing-based system is presented for identifying the crack geometry. Graphical user interfaces are also developed to take necessary user inputs required at different stages for crack identification, predicting weld bead dimension, and weld path generation. Based on the identified crack geometry and predicted weld bead feature, linear and curved weld path planning methodology is proposed. The proposed modules are validated for a case study by successfully generating the desired weld paths. Different natures of velocity profiles are considered to appraise the role on motion behaviour and a suitable profile is selected for reducing the jerks at sharp corners/via points on the weld path and maintaining uniform bead geometry.

Effect of member orientation on static strengths of cold-formed high strength steel tubular X-joints

Rotation of brace and/or chord members has a significant effect on the static strengths of tubular joints. Brace-rotated and bird-beak tubular joints are obtained by rotating the brace and/or chord members along their respective longitudinal axes by angles corresponding to their cross-sectional diagonal planes. This paper presents an experimental investigation of 29 cold-formed high strength steel (CFHSS) brace-rotated (BR), square bird-beak (SBB) and diamond bird-beak (DBB) tubular X-joints. The tubular members were made of S960 steel, having a nominal yield strength of 960 MPa. An axial compression load was applied through the braces of brace-rotated and bird-beak tubular X-joints. The welds connecting braces and chords of brace-rotated and bird-beak tubular X-joints were laid using the automatic gas metal arc welding process. The measured values of brace-to-chord width ratio (β) ranged from 0.33 to 0.83, effective brace-to-chord width ratio (β’) ranged from 0.25 to 0.87, brace-to-chord thickness ratio (τ) ranged from 0.67 to 1.28 and chord width-to-chord thickness ratio (2γ) ranged from 25.3 to 39.1. Three failure modes were observed in this study, namely chord face failure by plastification, a combination of this with chord sidewall failure (i.e., combined failure), and chord crown failure by plastification. Nominal strength prediction methods, from prior studies on member-rotated tubular joints as well as from the prEN 1993-1-8 (2021) and CIDECT (2008, 2009), were evaluated against the static strengths obtained from the tests. Reliability analysis was also performed to check the reliability levels of the existing design rules. For the range of tests undertaken, it was found that the current design rules of RHS-to-RHS, CHS-to-RHS and CHS-to-CHS tubular X-joints given in the CIDECT (2008, 2009), when used in conjunction with a material factor of 0.80, were found suitable and reliable for the design of CFHSS BR, SBB and DBB X-joints, respectively. In addition, the effect of change of member-rotation on the joint strengths and load–deformation curves was also assessed by comparing the structural performance of member-rotated tubular X-joints with the those of corresponding identical traditional RHS-to-RHS X-joints (Pandey and Young [1]).

Post-fire behaviour of cold-formed high strength steel tubular T- and X-joints

An experimental programme to investigate the post-fire residual strengths of cold-formed high strength steel (CFHSS) tubular T- and X-joints subjected to ISO-834 standard fire [1] exposure has been presented in this study. A total of 32 joints, including 16 T-joints and 16 X-joints, was tested. The tubular members of T- and X-joints were made of S900 and S960 steel grades. The test specimens were divided into 3 sets, and subsequently, these sets were then heated up to 300 °C, 550 °C and 750 °C by generally following the ISO-834 standard fire [1] curve, respectively. Once the fire exposed tubular T- and X-joints cool down to ambient temperature, tests were then conducted. The brace members of tubular T- and X-joints were made of square, rectangular and circular hollow sections (SHS, RHS and CHS), while SHS and RHS were used as the chord members. In this study, two configurations of tubular T- and X-joints were tested, first, where SHS and RHS were used as the brace and chord members (i.e. RHS-RHS), and second, where braces were made of CHS and chords were made of SHS and RHS (i.e. CHS-RHS). The T-joints were tested by applying axial compression load through the brace members and the chord ends were supported on rollers. The X-joints were tested by applying axial compression load through the brace members without chord preload. The welding was performed using automatic gas metal arc welding process. For T- and X-joints, the nominal values of brace-to-chord width ratio (β) ranged from 0.42 to 1, brace-to-chord thickness ratio (τ) ranged from 0.75 to 1, chord width-to-thickness ratio (2γ) ranged from 25 to 35 and chord side wall slenderness ratio (h0/t0) ranged from 15 to 35. Currently, there are no specific design rules to predict the post-fire residual strengths of tubular joints. Thus, the post-fire residual joint strengths obtained in this investigation were compared with the nominal strengths calculated from the CIDECT [2] and Eurocode 3 (EC3) [3] using the measured post-fire residual mechanical properties. It is shown that the current design rules of T- and X-joints given in the CIDECT [2] and EC3 [3] could not accurately predict the post-fire residual strengths of cold-formed S900 and S960 steel grades tubular T- and X-joints.

Analysis of mechanical and microstructural properties of gas metal arc welded dissimilar aluminum alloys (AA5754/AA6013)

The use of aluminum alloys to reduce weight in air, sea, and land vehicles is increasing rapidly, especially due to their low density, excellent corrosion resistance, good forming properties, and increasable mechanical properties. A common aspect of all the relevant industrial sectors is the need to join the many parts of manufactured technological products using welding methods. In these industries, using welding to join different aluminum alloys having high mechanical properties is especially important. However, despite the widespread usage areas, it is very difficult to join different aluminums and their alloys via welding. In this study, AA5754/AA6013 aluminum alloys were joined using automatic gas metal arc welding (GMAW). Welded joints were created at two different welding speeds (150 and 180 mm/min) and three different welding current values (130, 140, and 150 A). This study investigated the microstructural and mechanical properties of AA5754/AA6013 aluminum alloy sheets joined at different welding speeds and current values. The macro and microstructures of samples taken from the welded joints were examined. In addition, hardness, tensile, bending, and fatigue tests were performed on the welded samples. The findings obtained as a result of the tests were evaluated and interpreted in light of the literature.

Ultimate resistances of member-rotated cold-formed high strength steel tubular T-joints under compression loads

Brace-rotated and bird-beak joints are novel tubular joint configurations, which are obtained by the rotation of rectangular and/or square hollow section (RHS and/or SHS) members along their respective longitudinal axes by angles corresponding to their cross-sectional diagonal planes. The load vs deformation behaviour and static joint resistances of these novel tubular T-joints are presented in this study. In total, 30 cold-formed high strength steel (CFHSS) member-rotated tubular T-joints were tested. In this paper, member-rotated joints include brace-rotated (BR), square bird-beak (SBB) and diamond bird-beak (DBB) configurations, where RHS and SHS were used as braces and SHS were used as chords. The steel grade of RHS and SHS members was S960. The joint resistances of test specimens were determined by applying axial compression loads through the braces and supporting the chord ends on rollers. The automatic gas metal arc welding process was used to connect braces and chords. The brace width-to-chord width ratio (β) ranged from 0.33 to 0.83, effective brace width-to-chord width ratio (β′) ranged from 0.25 to 0.88, chord width-to-chord thickness ratio (2γ) ranged from 25.3 to 38.9 and brace thickness-to-chord thickness ratio (τ) ranged from 0.67 to 1.28. Three failure modes were observed in this investigation, which include chord face failure (F), combined failure (F + W), and chord crown failure (C). The joint resistances were compared with the nominal resistances obtained from the literature and EC3 (2005, [1]). It has been demonstrated that the design rules available in the literature are generally not suitable for the design of CFHSS brace-rotated and bird-beak T-joints made of S960 steel. Further, the effect of change of member-rotation angle (ω) on the joint resistances of CFHSS T-joints made of S960 steel was observed by comparing the joint resistances of BR, SBB and DBB T-joints of this investigation with the joint resistances of traditional RHS T-joints (Pandey and Young (2019), [2]) made of identical tubular member dimensions and steel grade.

Experimental investigation on stress concentration factors of cold-formed high strength steel tubular X-joints

This paper describes a test programme to investigate the stress concentration factors (SCF) of cold-formed high strength steel (CFHSS) traditional (without brace and/or chord rotation) and member-rotated tubular X-joints. The braces of traditional tubular X-joints were made of square, rectangular and circular hollow sections (SHS, RHS and CHS), whereas chords were made of SHS and RHS. The braces of member-rotated tubular X-joints were made of SHS and RHS, whereas chords were made of only SHS. The member-rotated tubular joints include brace-rotated (BR), square bird-beak (SBB) and diamond bird-beak (DBB) tubular joints. The tubular members were cold-formed from thermomechanically control processed (TMCP) S900 and S960 steel grades plates. A total of 15 tests was conducted to investigate the SCF of CFHSS traditional and member-rotated tubular X-joints subjected to brace axial compression loads. The brace and chord members were joined together using the automatic gas metal arc welding process. The measured values of brace width-to-chord width ratio (β) ranged from 0.33 to 0.74, effective brace width-to-chord width ratio (β’) ranged from 0.25 to 0.85, chord width-to-chord thickness ratio (2γ) ranged from 20.5 to 38.7 and brace thickness-to-chord thickness ratio (τ) ranged from 0.66 to 1.27. The experimentally obtained SCF values were compared with the SCF values calculated from the CIDECT [1] and literature [2,3]. It has been demonstrated that the existing SCF parametric equations are generally quite conservative and over-predicted the SCF values for cold-formed traditional and member-rotated tubular X-joints of S900 and S960 steel grades. Moreover, in order to observe the effect of member-rotation(s), the maximum SCF values of the brace and chord members of CFHSS member-rotated tubular X-joints were also compared with the maximum SCF values of CFHSS traditional tubular X-joints.

Static resistances of cold-formed high strength steel tubular non-90° X-Joints

This paper presents a test programme to investigate the static joint resistances and load vs deformation behaviour of cold-formed high strength steel (CFHSS) tubular non-90° X-joints. The investigation presented in this study predominantly focused on the chord failure of non-90° X-joints under brace axial compression loads. The experimental programme comprised of 26 tubular non-90° X-joints, which were fabricated with three included angles (θ1), i.e. 30°, 50° and 70°. Circular and square hollow sections were used as braces, while chords were made up of rectangular and square hollow sections. The nominal yield strengths of the tubular members were 900 and 960 MPa. The brace and chord members were connected using automatic gas metal arc welding process. The measured value of brace-to-chord width ratio (β) ranged from 0.53 to 1, brace-to-chord thickness ratio (τ) ranged from 0.52 to 1.01, chord width-to-thickness ratio (2γ) ranged from 20.5 to 38.7 and chord side wall slenderness ratio (h0/t0) ranged from 15.4 to 38.9. A total of three failure modes was observed, including chord face failure, chord side wall failure and combination of these two failure modes. The static joint resistances obtained from the tests were compared with the nominal joint resistances of X-joints given in the CIDECT and Eurocode 3. It is shown that the existing design rules in these specifications are not suitable for the design of S900 and S960 steel grades tubular non-90° X-joints. Further, the impact of the included angle (θ1) on the joint resistances of X-joints was observed by comparing the joint failure resistances of tubular non-90° X-joints obtained in this investigation with the joint failure resistances of tubular 90° X-joints of identical nominal tubular member dimensions and steel grades. In addition, tensile material properties from the weld heat affected regions of S960 steel grade tubular members of different thicknesses were also investigated.

Investigation on joint properties of AA5754 and AA6013 dissimilar aluminum alloys welded using automatic GMAW

Aluminum alloys AA5754 and AA6013 were joined using gas metal arc welding (GMAW) and the mechanical, microstructure and corrosion properties of the joints were investigated. The welding process was performed using argon as shielding gas with three different wire feed speeds and welding speeds. Metal wire (ER5356 filler) with a diameter of 1.2 mm was used in the welding process. In order to determine the mechanical properties of the joints, the welded specimens were subjected to tensile and hardness tests. In addition, an electrochemical corrosion test was conducted to determine the corrosion resistance of the specimens. The welding zone of the specimens was characterized via microstructure examination. In the tensile tests, fractures occurred in the weld metal and the heat affected zone (HAZ). However, tensile strength performance of the joints exceeded 90% under the appropriate welding parameters. The corrosion test results showed that the samples with joint defects (insufficient melting) were exposed to corrosion more rapidly than the others. Hardness test results revealed that maximum hardness values were measured at the HAZ of the AA6013 specimen, followed by the weld metal and HAZ of the AA5754 specimen, respectively. Microstructure inspections showed the structures of all the weld metals to be dendritic.

A Study on Global and Cluster-wise Regression Model in the Automatic GMA welding

The automatic welding system is presently made use of high volume production industries even if the cost of the related equipment is justified by the large number of pieces to be made. Also, the detailed movement devices with the predetermined sequences of welding parameter and the use of timers to form the weld joints were required. A new mathematical model that predict the optimal welding parameters on a given bead geometry and accomplish the desired mechanical properties of the weldment to make the automatic GMA (Gas Metal Arc) welding process should be needed. The developed model should be employed a wide range of material thicknesses and be applicable for all welding positions as well. In addition, the algorithm must be available in the form of mathematical equations which can be programmed easily to the robot and give a high degree of confidence in predicting the bead dimensions. In this study, two regression models with global regression and cluster-wise regression are proposed to be applicable for prediction of optimal welding parameters on the bead reinforcement area. For development of the proposed regression models, an attempt has been done for applying to a several methods. A series experiments to research the effects of welding parameters on bead reinforcement area as a function of key output parameters for the lab-joint weld in the automatic GMA welding process was performed. Not only the fitting of these models was checked and compared by using a variance test (ANOVA), but also the prediction of bead reinforcement area using the developed regression models were carried out the basis of the additional experiments.

A Study on Experimental Design Methods for the Automatic GMA Welding Process

Generally, the welding parameters directly affect the weld forming and the joint performance. Because many parameters are involved in the automatic arc welding process, it is not realistic to use traditional experimental methods, such as full factorial design. Therefore, it is important to find out the good experimental design method to determine the welding parameters for optimal joint quality with a minimal number of experiments. Therefore, this study is aimed at investigating the effect of DOE (Design of Experiment) methods on bead width of mild steel parts welded by the automatic GMA (Gas Metal Arc) welding process. In this work, Taguchi method was used for studying the effect of the welding parameters on optimization of bead width, while Box-Behnken method was utilized to develop a mathematical model relating the bead width to welding parameters such as welding voltage, arc current, welding speed and CTWD (Contact Tip to Work Distance). The S/N (Signal-to-Noise) ratio and the ANOVA (Analysis of Variance) were employed to find the optimal bead width. Confirmation tests were carried out to validate the effectiveness of the Taguchi method. The experimental results show that welding current mainly affected the bead width. The predicted bead width of 3.12mm was in good agreement with the confirmation tests. With the regression coefficient analysis in the Box-Behnken design, a relationship between bead width and four significant welding parameters was obtained. A second-order model has also been established between the welding parameters and the bead width as welding quality. The developed model is adequate to navigate the design space.

Tests of cold-formed high strength steel tubular T-joints

The paper presents an experimental investigation on cold-formed high strength steel tubular T-joints. The fabricated T-joints include brace members made up of square, rectangular and circular hollow sections, while chord members were made up of square and rectangular hollow sections. The nominal yield strengths of square and rectangular tubular members were 900 and 960 MPa, while the nominal yield strength of circular tubular members was 900 MPa. Two configurations of tubular joints were fabricated, first, where both brace and chord members were made up of square and rectangular hollow sections, and second, where circular hollow section braces were welded to square and rectangular hollow section chord members. The brace and chord members were joined together by automatic gas metal arc welding process. In total, 24 tubular T-joint tests were conducted where an axial compression was applied through the brace members of the T-joints, while the ends of the chord members were supported on rollers. The ratios of brace-to-chord width (β) ranged from 0.34 to 1, brace-to-chord thickness (τ) ranged from 0.52 to 1.27 and chord width-to-chord thickness (2γ) ranged from 20.63 to 38.55. The resistances and deformations of tubular T-joints were carefully examined. In order to evaluate the applicability of the existing design provisions for high strength steel tubular T-joints, test results were compared with the nominal strengths obtained from the Eurocode 3 (EC3) and CIDECT. It is shown that the existing design provisions are not capable of providing accurate and reliable predictions for the design of cold-formed high strength steel tubular T-joints made up of S900 and S960 steel grades.

Prediction model for bead reinforcement area in automatic gas metal arc welding

Automatic welding systems are widely used for high-volume production industries, where the cost of related equipment is justified by the large number of pieces to be made. Detailed movement devices are required, including predetermined welding parameter sequences and timers, to form the weld joints. Automatic gas metal arc welding processes require new mathematical models to predict optimal welding parameters for a given bead geometry to accomplish the desired mechanical properties of the weldment. The developed algorithm should be able to be employed across a wide range of material thicknesses and all welding positions, and available in analytical form to be easily applied to the welding robot with high degree of confidence in predicting bead dimensions. Therefore, this study investigated welding voltage, arc current, welding speed, contact tube weld distance, and welding angle on bead reinforcement area for automated gas metal arc welding processes using a central composite design to generate response surface methodology and artificial neural network models. Average absolute deviation was used to compare accuracy between the two models. Analysis of variance showed coefficients of determination of 0.894 and 0.948 with average absolute deviation 4.01% and 3.11% for the response surface methodology and artificial neural network models, respectively. This suggests that artificial neural network is a better modeling technique for predicting bead reinforcement area compared to response surface methodology.

Investigation on various welding consumables on properties of carbon steel material in gas metal arc welding under constant voltage mode

In this present work, the influence of different consumables on weld properties of carbon steel plate was studied by automatic gas metal arc welding under constant voltage mode. For all experiments, the process parameters such as welding current of 200 A, voltage of 28 V and welding speed of 200 mm/min were kept constant. The results indicate that the angular distortion remained higher for solid wire, whereas it was minimum for flux-cored wire and the lowest in metal-cored wire. Mechanical properties such as yield strength, tensile strength, elongation and joint efficiency remained high for solid wire relative to cored wire. Excellent impact toughness of the weld metal and heat-affected zone was reported for the flux-cored welds compared with solid wire and metal-cored welds.

A study on the modified Hough algorithm for image processing in weld seam tracking

Nowadays, automatic Gas metal arc (GMA) welding is receiving a growing attention for its fast production speed and wide-ranging versatility. Furthermore, automatic and robotic welding systems are urgently needed for general application, which depends on the realization of auto-weld seam tracking. Seam tracking system allows for not only robot or machine trajectory shifts, but also adaptive control to change weld bead formation, making further improvement on the weld quality. Based on the laser vision system, this study aims for development of an image processing by the modified Hough algorithm which applied for seam tracking system in GMA welding. To achieve this objective, image features in the procedure of welding processing were discussed and specially treated. Algorithms in the image processing were investigated to maximize the processing effect based on the modified Hough algorithm, which was quite costefficient in line detection. Quantitative evaluations of the used algorithm were set up to acquire optimal image processing algorithm. Finally, a common image processing method was employed to verify efficiency of proposed image processing and extract the welding location in a shorten time for industrial application. It can be concluded the detected feature points and centerlines proved that this algorithm can be used for automatic GMA welding process as well as industrial applications.

Effect of process parameters on toughness and metallurgical behaviour during uniaxial automatic gas metal arc welding of austenitic stainless steel AISI 316

Gas metal arc welding (GMAW) is extensively used for joining of different graded steels as well as aluminium and other nonferrous materials. GMAW offers clean welding with low defects without using flux and suitable for different positional welding. In the present work, a fabricated automatic movement setup is used for GMAW to study the influences of four different process parameters during joining of austenitic stainless steel AISI 316 using AISI 304 (ER304) filler wire. With this setup, welding is carried out maintaining a constant contact tube-to-workpiece (CTW) distance and uniform heat input. Experimental results and subsequent analysis show that the toughness is most significantly influenced by voltage followed by welding speed, gas flow rate, and current. Toughness reduces with the increase in shielding gas flow rate and welding speed as austenite and traces of retained delta ferrite may be present due to high solidification rate. Metallurgical observations by X-ray diffraction (XRD) and scanning electron microscopy indicate that solidification mode is mainly characterized by formation of fully austenite or austenite and ferrite at cell and dendritic boundaries. XRD results revealed that higher toughness is observed due to minimum formation of carbides.

Environmental and Social Life Cycle Assessment of Welding Technologies

Life Cycle Assessment (LCA) and Social Life Cycle Assessment (SLCA) are applied in evaluating possible social and environmental impacts of the state-of-art welding technologies, such as Manual Metal Arc Welding (MMAW), Manual Gas Metal Arc Welding (GMAW), Automatic GMAW and Automatic Laser-Arc Hybrid Welding (LAHW). The LCA results indicate that for 1 meter weld seam, MMAW consumes the largest amount of resources (like filler material and coating on electrodes) and energy, which contributes to comparatively higher environmental impacts in global warming potential, acidification, photochemical ozone creation potential and eutrophication than other chosen processes. With regard to social aspects, the health issues and fair salary are under survey to compare the relative potential risk on human health caused by fumes in different welding technologies, and to indicate the sufficiency of current salary of welders in Germany. The results reflect that the wage status of welders is still fair and sufficient. The manual processes bring much higher potential risk of welders’ health than the automatic processes, especially MMAW.

Influence of Heat Input in Automatic GMAW: Penetration Prediction and Microstructural Observation

In the present work, the influence of heat input is studied on depth of penetration while depositing bead on AISI 304 stainless steel using an indigenously fabricated automatic gas metal arc welding (GMAW) movement setup. Depth of penetration and fusion zone profiles are predicted at different conditions by the bond graph modeling approach and validated using measured depth of penetration and fusion profile. The effects of heat input on toughness and metallurgical behavior are analyzed while joining AISI 304 plates using automatic GMAW. Heat input and gas flow rate significantly influence the toughness at room temperature and at −20°C. Metallurgical observations by scanning electron microscopy are carried out and it is observed that high heat input and lower cooling rate increase grain size. High heat input and rapid cooling prevent grain growth and lead to grain refinement.

Development of Automatic GMAW Setup for Process Improvements: Experimental and Modeling Approach

Gas metal arc welding (GMAW) offers highly efficient and low-cost welding, but manual movement of torch affects the uniformity of bead geometry, penetration, and heat input. In the present work, an indigenous automatic movement setup is designed and fabricated for GMAW. System behaviors like drive motor response, carriage, and wheel movement are studied through bond graph modeling. Welding time and welding velocity obtained from simulation are used to obtain the deposition efficiency during weld bead deposition on low carbon steel and stainless steel workpieces. Spatter index is also calculated for both the materials. Welding performance of automatic welding is compared with manual movement welding, and automatic welding is found capable to offer high deposition efficiency, low spatter index, uniform depth of penetration, and lower distortion for both the materials. Variation in microhardness and metallurgical observations by scanning electron microscopy are carried out for microstructure analysis.