A study on mechanical properties and microstructure of microalloyed steels in the case of arc welding process

Arc welding is widely used in industrial applications. In arc welding process, welding parameters significantly affect weld quality such as mechanical properties. However it is very challenging to tune these parameters to achieve best weld quality. Some researchers developed some methods to optimize welding parameters, but these methods have many limitations. In this paper, we propose an innovative method to optimize welding parameters for robotic welding process using Gaussian Process Regression (GPR) and Bayesian Optimization Algorithm (BOA). The relationship between the weld quality and welding parameters is modeled based on GPR. To expedite the optimization process, BOA is applied to balance the modeling process and optimization process. The Gas tungsten arc welding (GTAW) process is utilized to test the proposed method. The tensile strength of the welded joints was measured to evaluate the weld quality. The experimental results demonstrate that the proposed method can find a set of optimal welding parameters using about ten experiments. Thus it greatly improves the welding parameter optimization process by reducing the number of trial experiments compared to the existing methods such as Design-of-Experiments. The proposed method can also achieve better solution by evaluating more parameter values and exploring the whole parameter space. Therefore it provides an efficient and effective tool to optimize welding process.

Duplex stainless steel is an exotic material known for its excellent corrosion resistance and mechanical properties due to the presence of a two-phase structure that is quite balanced between ferrite and austenite, making it one of the top choices for the oil and gas industry. In this paper, we will discuss the process and investigation of the welding results of the A/SA 790 UNS 31803 duplex pipe joint which is connected using the gas tungsten arc welding (GTAW) process for gas purification process applications. The welding process and qualification is based on the ASME BPVC Sec code. IX was then tested to obtain information on the characteristics of the mechanical properties, microstructure, and corrosion resistance of the resulting joints. Heat input in the welding process is a crucial factor that determines the equilibrium of the ferrite and austenite phases which then correlates with the mechanical properties and corrosion resistance of the joint. Based on the microstructural analysis, there was a decrease in the ferrite phase in the weld metal, but it was still within the required limits. Furthermore, the results of the mechanical properties test showed that the tensile strength of the joint was greater than the tensile strength of the base metal and no open discontinuity was observed in the bending test. The corrosion test showed no signs of pitting corrosion with a weight loss value of 1.7 g/m2.

5 - Gases for advanced welding processes

In the construction industry, power plants, shipbuilding, aerospace, automotive, oil and gas, and a wide variety of other industrial sectors, IS2062 steel is in high demand as a structural material. Gas metal arc welding (GMAW) process and shielded metal arc welding (SMAW) process, which are both traditional fusion arc welding methods, are utilised extensively for joining structural materials. This study presents the results of a comparative investigation into the mechanical properties and metallurgical characteristics of IS2062 E350 grade steel that has been fusion welded by GMAW and SMAW processes separately. Correlations were found between microstructures and the evaluation of tensile strength, impact strength and microhardness. Both GMAW and SMAW welded joints reached maximum transverse ultimate tensile strengths of 634 and 676 MPa, respectively. As an additional point of interest, the overall percentage of elongation for the GMAW and SMAW processes was 25.49% and 26.19%, respectively. Impact toughness of 235 J and 213 J was measured for joints that were created using GMAW and SMAW, respectively. When compared to other regions, the microhardness that was produced in the subcritical heat-affected zone was lower. The maximum microhardness obtained for GMAW and SMAW are 175 VHN and 185 VHN respectively. The investigation found that GMAW joints exhibited qualities that were somewhat better than those of SMAW joints. It has been discovered that the majority of weld failures occur in the subcritical heat affected zone. The reason behind these failures is that the weldment softens as a result of grain deformation.

The Gas Metal Arc Welding (GMAW) process is leading the way in arc welding process growth because it is more efficient, economical, and of high quality. The effects of ER70s filler metal on mechanical properties and corrosion behaviour in low carbon steel with a base metal thickness of 12 mm are investigated in this study using robotic gas metal arc welding (GMAW). After the welding process, the quality, microstructure, and micro-hardness of each specimen were measured and the effect was studied. The immersion test was studied using weight loss and corrosion rate measurements for 1, 2, 4, 6, and 8 weeks in the absence and presence of 3.5wt. % NaCl. As a result, the microstructure displayed the different grain boundaries of each parameter that affected the welding parameters. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are used to characterise the surface morphology and pitting areas on the welded substrate. The corrosion rate of the welded sample immersed in 3.5wt. % medium was higher than in the absence of NaCl. The SEM results revealed that NaCl played an aggressive role in inducing the corrosion process and producing significant pits on the welded joint, particularly in the HAZ area. This research may provide a significant understanding of how the welding process, filler metal, and low carbon steel metal caused corrosion behaviour in the marine environment, particularly for oil and gas applications.

Mechanical properties and microstructural characteristics of wire arc additive manufactured 308 L stainless steel cylindrical components made by gas metal arc and cold metal transfer arc welding processes

Experimental investigation on microstructure, mechanical properties, and residual stresses of dissimilar welded joint of martensitic P92 and AISI 304L austenitic stainless steel

Austenitic stainless steel (ASS) is the most common type of stainless steel which offers excellent weldability and mechanical properties. ASS is being used for various applications i.e. automotive, oil and gas and chemical industries in which the welding process plays a prominent role. Welding process selection is the main factor that emphasizes mechanical and corrosion resistance properties in various aggressive environments. There are various corrosion occurs in ASS but intergranular corrosion (IGC) forms during welding at elevated temperatures. IGC mainly occurs at grain boundaries of structure and resulting chromium depletion due to precipitation of chromium carbide at the grain boundary. In present work pulsed current gas tungsten arc welding (PCGTAW) process was used to investigate intergranular corrosion by oxalic acid test as per ASTM A262 Practice A. Experiments performed based on Taguchi L9 using design of experiments and corrosion rates are evaluated at base metal, heat affected zone and weld zone. This work is aimed to optimize process parameters followed by regression analysis to IGC susceptibility in the weldment. In this investigation, it has been found from ANOVA and main effects plots that peak current and base current are the most significant parameters in the PCGTAW process. The results of the corrosion test revealed that heat affected zone is more susceptible to IGC. At the end, it has been observed that the optimum value of peak current, base current and frequency based on regression analysis are 100 A, 50 A and 6 Hz respectively.

Aluminum 6061 is an aluminum alloy that is widely used in various industrial fields, which heat treatable. However, it can be joined using a welding process. Aluminum joining using the Gas Tungsten Arc Welding (GTAW) process has become the option to produce good quality joints. This research aims to get optimum welding parameters by knowing the mechanical properties and microstructure of the welding results. The GTAW process uses a 25-volt voltage, Argon protective gas flow rate of 15 liters per minute with filler rod ER 5356 with 2.4 mm diameter and electrodes tungsten 2.4 mm in diameter. This process uses a single V butt joint and groove angle of 60° with variations in the current of 100, 110 and 120 A. The results indicate that specimens with a variety of current of 110 A give better results in the absence of defects, have a tensile strength of 152 MPa, and get a hardness value of 87.55 HV, which is the highest compared to the other two specimens. Whereas specimens with the current variation of 100 and 120 A have defects in the weld area. The optimum parameters of the 6061 aluminum GTAW process with a thickness of 6 mm using a current of 110 A bring on better outcomes and mechanical properties than the use of currents of 100 and 120 A.

Microstructural characteristics and properties of wire arc additive manufactured 304L austenitic stainless steel cylindrical components by different arc welding processes

Gas tungsten arc and laser beam welding processes effects on duplex stainless steel 2205 properties

The welding has been utilized to stabilize the phase fractions in the microstructure of lean duplex stainless steel (LDSS) to build massive mechanical structures. The influence of heat input on the microstructure, mechanical properties, and corrosion behavior of LDSS 2101 during the gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW) processes is investigated in the present work. Specifically, we compared the outcomes between low heat input (LHI) at 0.85 kJ/mm and high heat input (HHI) at 1.3 kJ/mm for both welding techniques. Throughout the welding process, ER2209 filler wire was utilized. To assess the microstructural changes in the weldments, we employed an optical microscope, a scanning electron microscope, and X-ray diffraction. The results revealed that the volume phase fraction of ferrite was significantly higher in the LHI sample of GTAW compared to HHI GTAW and all SMAW welds. LHI GTAW welds have 18.2% greater Charpy impact toughness than LHI SMAW, whereas HHI GTAW has 35.7% higher than HHI SMAW specimens. The microhardness of the LHI GTAW weldments increased (from 230 ± 3.2 to 252 ± 4.8 HV10), whereas the microhardness of the LHI SMAW weldments increased (from 227 ± 2.8 to 246 ± 5.2 HV10). GTAW exhibited a fine grain structure, showcasing favorable tensile properties and higher hardness compared to SMAW. Conversely, the SMAW welds and their heat-affected regions exhibited coarse grain structures. These findings highlight the superior performance of GTAW in terms of microstructural characteristics, and mechanical properties when working with LD SS 2101 in comparison to SMAW.

Heat sources in wire arc additive manufacturing and their impact on macro-microstructural characteristics and mechanical properties – An overview

Review on the use of activated flux in arc and beam welding processes

For every manufacturing industry, materials that are applicable for particular conditions and are of low economy are highly required. Hence various studies are carried out to determine the working conditions for several materials. The wide application of steel in industry demands a significance study on physical, chemical and mechanical properties of steel, Here, the characteristic changes in the mechanical and microstructure properties due to the effect of heat inputs of gas tungsten arc welded AISI 316 Stainless steel were examined. The major issue faced during the welding process of stainless steel is the increase in grain growth in the heat affected zone (HAZ). The welding process have been carried out using three heat input parameters on the AISI 316 Stainless steel from the operating window of the gas tungsten arc welding process (GTAW) and they are categorized as low heat (2.563 KJ/mm), medium heat (2.784 kJ/mm) and high heat (3.017 kJ/mm) . These welded joints of AISI 316 SS have been subjected to evaluation of tensile testing microstructure and mechanical properties so as to interrupt and infer the impact of thermal arc energy on the mechanical properties and microstructure of AISI 316 SS welded joints. From this study, it has been inferred that the heat input has notable effect on Ultimate Tensile Strength, Hardness and Microstructure on AISI 316 SS GTAW plates.