Automatic Welding Process Research Articles

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]).

Parametric Optimization of the GMAW Welding Process in Thin Thickness of Austenitic Stainless Steel by Taguchi Method

In the present work, an analysis of different welding parameters was carried out on the welding of stainless-steel thin thickness tubes by the Gas Metal Arc Welding (GMAW) process. The influence of three main parameters, welding voltage, movement angle, and welding current in the quality of the welds, was studied through a specifically designed experimental process based on the establishment of three different levels of values for each of these parameters. Weld quality is evaluated using destructive testing (macrographic analysis). Specifically, the width and root penetration of the weld bead were measured; however, some samples have been disregarded due to welding defects outside the permissible range or caused by excessive melting of the base metals. Data are interpreted, discussed, and analyzed using the Taguchi method and ANOVA analysis. From the analysis of variance, it was possible to identify the most influential parameter, the welding voltage, with a contribution of 43.55% for the welding penetration and 75.26% for the bead width, which should be considered in the designs of automatic welding processes to improve the quality of final welds.

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.

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.

Prediction of distortions and residual stresses in narrow gap weld joints prepared by hot wire GTAW and its validation with experiments

The present paper aims to predict distortions and residual stresses in thick plate weld joints of austenitic stainless steel material prepared by automatic hot wire gas tungsten arc welding (GTAW) process and narrow gap technique using finite element analysis (FEA). The prediction has been validated by carrying out experiments. The variables considered in welding of plate joints are narrow groove configuration, high deposition rate leading to lower heat input (hot wire GTAW), and stress relieving treatment. A suitable stress-relieving treatment has been proposed for relaxing residual stresses and preventing sensitization of the heat-affected zone (HAZ) of the ASS weld joint. Predicted and experimental results of temperature distribution, distortions, and residual stresses were found to be in good agreement. The applicability of prediction of residual stresses for higher weld thicknesses has also been verified. The nature of residual stresses across thickness has also been compared with that given in Structural Integrity Assessment Procedures for European Industry (SINTAP) and BS 7910 standards. Details of the above finding are discussed in this paper.

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.

Welding procedure qualification of small diameter thin-walled titanium pipes

The small diameter thin-walled TA2 titanium tubes are used in a technical renovation project. In order to ensure the performance of the product, the automatic GTAW welding process is adopted by analyzing the weldability of TA2 titanium tubes. The process qualification tests such as appearance inspection, nondestructive testing, mechanical properties and metallographic examination are carried out. The test results show that the welding joint with good performance can be obtained by reasonable welding procedure parameters and strict gas protection measures. The welding procedure and related measures can be used as a reference for manufacture and installation of titanium pipes.

Experimental Investigation of Fatigue Crack Growth Behavior of the 2.25Cr1Mo0.25V Steel Welded Joint Used in Hydrogenation Reactors.

In this work, the fatigue crack growth (FCG) behavior and fatigue damage mechanism of the 2.25Cr1Mo0.25V steel welded joint used in hydrogenation reactors were investigated. The multi-pass welding was carried out to manufacture the welded joint using the combined shielded metal arc welding (SMAW) and submerged automatic arc welding (SAAW) processes. The FCG behavior of different zones in the welded joint, including the base metal (BM), the heat-affected zone (HAZ) and the weld metal (WM), were studied by compact tension tests. Moreover, the acoustic emission (AE) technique was used to monitor AE signals generated from FCG process for further understanding FCG behavior and fatigue mechanisms. Additionally, the microstructures and fracture surfaces of different specimens were observed by optical microscopy (OM) and scanning electron microscopy (SEM). The results revealed that the microstructure of BM is fine granular bainite, while the WM shows coarser bainite grains. The HAZ exhibits the most significant inhomogeneity with large dispersion of grain size. FCG results showed that the HAZ exhibits much higher fatigue crack growth rate (FCGR) at low ΔK values, while the BM shows the most superior fatigue resistance. The AE technique is successful in monitoring and identifying damage evolutions during the FCG process. Moreover, an enhanced AE activity is observed in FCG of the WM specimen, which is attributed to the combined influence of the formation of numerous secondary cracks and coarse-grained microstructures.

PENGELASAN DISIMILAR MATERIAL (DUPLEX STAINLESS STEEL) 2205 DAN (HIGH STRENGTH STEEL) GRADE VL D36 UNTUK KAPAL OIL TANKER

The choice of Duplex Stainless Steel material for oil tanker ship construction is very appropriate because in addition to having good mechanical properties (high tensile and yield strength and toughness) as a ship construction structure, it is also resistant to loads of highly corrosive liquid chemicals. Unlike Mild Steel or Duplex Stainless Steel A, welding and treating Duplex Stainless Steel requires very strict procedures and care must be taken. The choice of welding process, namely a combination of (Flux Cored Arc Welding) and SAW (Submerged Arc Welding) is a welding process that is very suitable for welding ship construction. The welding process is categorized as a semi-automatic and automatic welding process that can increase productivity while speeding up welding work. This paper illustrates the welding of two materials with different specifications, namely Duplex Stainless Steel 2205 plate material and VL D36 plate material, along with practical instructions for welding it up to the things that must be considered regarding the handling procedure. In welding Duplex Stainless Steel 2205 plate material it is very important to keep the heat input in the range of 0.5-2.5 kj / mm.

Research on Automatic Welding of Marine Steel Plate Based on Artificial Intelligence

As one of the diversified means of transportation for human beings, at present, the effects of ships in the transportation industry are also very high-quality. However, in the early years, various accidents occurred frequently due to the instability of the welding quality of its own steel plates when ships sailed. These examples have attracted the attention of experts. It was at that time that the technology of welding steel plates for ships was formally studied and widely used[1]. Moreover, under the leadership of artificial intelligence technology, the process of automatic welding of steel plates through the recognition of machine vision control robots is also in the process of development. The error of the manual welding method of the previous marine steel plate is very large. Fortunately, the welding error of the automatic welding technology of the marine steel plate using artificial intelligence is very small.

A Robust Weld Seam Tracking Method by Using Intensity-Modulated Structured Light

The seam tracking method by using structured light is widely used in the automatic welding process. Most of the noise can be filtered out by a narrow-band optical filter whose center wavelength is the same as the structured light. However, it still suffers from light noise caused by sparks and fumes when the structured light is getting close to the welding pool. This limitation of the structured-light based method is inherent because light noise caused by the welding process has a wide spectrum and couldn't filter out by the optical filter. To circumvent this problem, we proposed a seam tracking method that can modulate the intensity of the structured light at a high frequency by an acoustic-optic modulator (AOM) and extract the modulated frequency from multiple seam images by Fourier transformation. As the frequency of noises such as sparks is random and different from the modulated frequency, the proposed method can remove these noises in the frequency domain directly. We demonstrated the robustness of this method by detecting seam in noisy welding conditions.

A new mechanical calibration strategy for U-channel extrusions

The extrusion process of aluminum profiles introduces dimensional variations commonly exceeding the dimensional tolerance requirements for fit-up and assembly when using automated welding processes in the automotive industry. Improving dimensional accuracy of extrusions is challenging from both a technical and economical point of view. However, an alternative technical approach is to introduce fast and simple downstream processes, such as mechanical calibration, to achieve components or products with improved dimensional characteristics. In this paper, a new mechanical calibration strategy is proposed based on the principle of combining transversal stretching and local bending. The strategy is tested on a U-channel extrusion—which is a particularly challenging geometry for extrusions concerning dimensional accuracy. The overall objective is to improve gap opening variations on U-channels compared with as-extruded dimensional capabilities, especially in the case of alloys that are water quenched to obtain high strength and ductility. The study is also intended to serve as basis for future optimization of the mechanical calibration process. An experimental platform and die/tool system was developed, and finite element simulation was used as a research tool to re-produce and better understand the calibration process, thus further analyzing the mechanisms and deformation characteristics important to dimensional accuracy. The experimental results show that the mechanical calibration strategy has good potential to improve the dimensional accuracy of gap openings of U-channels by 90%. The study demonstrates that as-extruded profiles with tolerance limits exceeding the requirements of the final component can effectively be calibrated with the proposed method and hence used in high-volume manufacturing.

Real-Time Detection of Weld Defects for Automated Welding Process Base on Deep Neural Network

In the process of welding zinc-coated steel, zinc vapor causes serious porosity defects. The porosity defect is an important indicator of the quality of welds and degrades the durability and productivity of the weld. Therefore, this study proposes a deep neural network (DNN)-based non-destructive testing method that can detect and predict porosity defects in real-time, based on welding voltage signal, without requiring additional device in gas metal arc welding (GMAW) process. To this end, a galvannealed hot-rolled high-strength steel sheet applied to automotive parts was used to measure process signals in real-time. Then, feature variables were extracted through preprocessing, and correlation between the feature variables and weld porosity was analyzed. The proposed DNN based framework outperformed the artificial neural network (ANN) model by 15% or more. Finally, an experiment was conducted by using the developed porosity detection and prediction system to evaluate its field application.

Real-time monitoring of immobilized oxide defects on bead surface in welding of high-strength galvanized steel

Welding is widely used for joining steel components in the automobile industry. With the use of high-quality materials, welding defects began to become increasingly complex. Immobilized oxide is one of the recent complex defects. Immobilized oxide defects generated in gas metal arc welding (GMAW) of high-strength steel and high-strength galvanized steel result in unpainted part on the surface of welding beads. Thus, it is necessary to be eliminated by using grinding and peening. However, it is difficult to find where oxides generate and how oxides generate in order to eliminate it. Few studies have explored the mechanism of immobilized oxide formation in other fields so far. In this study, the generation patterns of oxide defects were confirmed. Further, an oxide defect monitoring system for GMAW was developed by using an infrared camera and image processing equipment. The chemical properties of the immobilized oxide were verified by performing energy dispersive spectroscopy (EDS). The oxide appeared to be brighter in the infrared image, and then, image processing was conducted to determine the boundary of oxide defects. The processed images were laid over the original images, and the oxide defect area was displayed on the monitoring panel. Patterns of oxide defect generation were confirmed when it was combined with the following molten pool area moving in the opposite direction of the welding direction in our results. The developed monitoring system can be easily applied to the automatic welding process in the automobile industry.

Discerning Weld Seam Profiles from Strong Arc Background for the Robotic Automated Welding Process via Visual Attention Features

In the robotic welding process with thick steel plates, laser vision sensors are widely used to profile the weld seam to implement automatic seam tracking. The weld seam profile extraction (WSPE) result is a crucial step for identifying the feature points of the extracted profile to guide the welding torch in real time. The visual information processing system may collapse when interference data points in the image survive during the phase of feature point identification, which results in low tracking accuracy and poor welding quality. This paper presents a visual attention feature-based method to extract the weld seam profile (WSP) from the strong arc background using clustering results. First, a binary image is obtained through the preprocessing stage. Second, all data points with a gray value 255 are clustered with the nearest neighborhood clustering algorithm. Third, a strategy is developed to discern one cluster belonging to the WSP from the appointed candidate clusters in each loop, and a scheme is proposed to extract the entire WSP using visual continuity. Compared with the previous methods the proposed method in this paper can extract more useful details of the WSP and has better stability in terms of removing the interference data. Considerable WSPE tests with butt joints and T-joints show the anti-interference ability of the proposed method, which contributes to smoothing the welding process and shows its practical value in robotic automated welding with thick steel plates.

Characteristics of Susceptible Microstructure for Hydrogen-Induced Cracking in the Coarse-Grained Heat-Affected Zone of Carbon Steel

Hydrogen-induced cracking (HIC) susceptibility of the coarse-grained heat-affected zone (CGHAZ) of carbon steel was evaluated using implant tests and the characteristics of susceptible microstructure to HIC was investigated. Three types of carbon steel with different alloying elements were employed as base metals to vary the microstructure of the CGHAZ and implant test assemblies were prepared using an automatic shielded metal arc welding process. A clear difference in microstructure was observed between the CGHAZs of steel with high and low HIC susceptibility; the formation of the primary ferrite in the CGHAZ of carbon steel plays an important role in decreasing the HIC susceptibility.

Features of repair welding of power hydrocylinder elements

At present, the use of power hydraulic cylinders is an integral part of most industrial equipment. They provide translational and horizontal movements, replacement of goods, fixation, etc. These devices are necessary elements of the equipment where application of the corresponding level of effort is applied. Often hydraulic cylinders are created specialized to perform certain types of work. It should be noted that part of the elements of the power cylinder in the manufacture is combined with welding. Such integral connections provide rigidity of installation, tightness of a design, fatigue strength at multicycle loadings. Difficult operating conditions, significant workloads, the presence of various external factors often leads to the destruction of individual elements of the cylinder. At the same time, the cost of repairing equipment that involves replacement with new power devices is quite high. This causes the implementation of repair and restoration work carried out at specialized enterprises. However, in the case of repairs, there are often a number of problems that require prompt resolution in the production environment. These should include the provision of basic materials with similar physical and chemical properties, the establishment of welding modes, the selection of the necessary welding materials, the use of appropriate techniques for conducting the arc process, etc. Therefore the repaired welded design of the case of the power hydraulic cylinder needs additional studying for weldability of separate elements among themselves, formation of a zone of thermodeformation influence. In general, the repaired hydraulic cylinder should meet the installation operating requirements depending on the purpose. The design of the considered hydraulic cylinder of the press installation is rather technological from the point of view of maintenance of automation of welding process. It contains long welds of a simple ring configuration. At the same time, the significant linear dimensions and the presence of a cylindrical surface cause some complexity in the implementation of processes. The construction material of the power hydraulic cylinder is low-carbon low-alloy steels. The analysis of technological weldability indicates a tendency to crack due to the thermal cycle of welding. The simulation of welds of the power hydraulic cylinder is performed in the work. The number of rollers was taken into account when obtaining butt welds. A comparative analysis of different electrode materials with different doping systems is done. The most applicable welding materials by chemical composition and properties of the weld metal are determined. According to the literature data and the results of comparative analysis, the optimal range of cooling rate of the main material of the hydraulic cylinder was established. The properties and structure of the zone of thermal influence of the butt welds of the power hydraulic cylinder have been studied. The magnitude of deformations and stresses caused by the thermal cycle of welding of the shell structure of the hydraulic cylinder liner is investigated. The admissible parameters of the zone of plastic deformations during butt welding are determined.

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.

Effects of heat input on the mechanical properties of butt-welded high and ultra-high strength steels

In this study, the mechanical properties of butt-welded thin plates made of S700, S960 and S1100 steels under various heat inputs (HI) are investigated. The gas metal arc welding (GMAW) process with two different levels of HI, and laser welding (LW) are implemented for this purpose. Fully automated welding process is employed to attain high quality and homogeneous weldments. Standard tensile tests of the butt-welded joints, together with micro-hardness measurements are conducted in this study. The microstructure of the heat affected zones (HAZ) of the weldments are closely examined using scanning electron microscopy (SEM). It was observed that while the fracture was occurred at the base materials of all S700 and S1100 weldments, the S960 suffered from failure at the HAZ which resulted in reduction of the joint’s strength and ductility. For all the studied steels, it was found that the joint’s ductility is highly dependent on HI values over the range of 0.3–1.4 kJ/mm for each welding pass. Though, the S1100 steel showed the best performance under welding HI with a moderate change in its mechanical properties and a stable microstructure after welding compared to S700 and S960.