Optimum Welding Parameters Research Articles

Pulsed FCAW of Martensitic Stainless Clads onto Mild Steel: Microstructure, Hardness, and Residual Stresses

The low carbon martensitic stainless AWS 410NiMo steel has in its chemical composition 13% chromium, 4% nickel, and 0.4% molybdenum (wt.%) and is used in turbine recovery, rotors, and high-pressure steam pump housings due to its resistance to impact at low temperatures, as well as to corrosion and cavitation. Those applications of the AWS 410NiMo steel frequently demand repair, which is performed by welding or cladding. Arc welding is a well-established technique for joining materials and presents several parameters that influence the mechanical performance of the weld bead. Although numerous welding processes exist, optimizing welding parameters for specific applications and materials is always challenging. The present work deals with a systematic study to verify the correlation between the pulsed fluxed core arc welding (FCAW) parameters, namely pulse current and frequency, welding speed, and contact tip work distance (CTWD), and the bead morphology, microstructure formation, residual stress, and hardness of the martensitic clad. The substrate used was the AISI 1020 steel, and the AWS 410NiMo steel was the filler metal for clad deposition. From the initial nine (9) samples, three (3) were selected for in-depth characterization. Lower heat input resulted in lower dilution, more elevated hardness, and lower compressive residual stresses. Therefore, the results highlight the need for selecting the proper heat input, even when using a pulsed FCAW procedure, to achieve the desired performance of the clad. In the present case, a higher heat input appears to be more advantageous owing to the lower convexity index, smooth hardness transition between fusion and heat-affected zones in addition to more elevated compressive stresses.

Welding parameters optimization during plunging and dwelling phase of FSW 2219 aluminum alloy thick plate

The influence of welding parameters on temperature distribution during plunging and dwelling phase of friction stir welding (FSW) 2219 aluminum alloy thick plate has not been studied. Improper selection of welding parameters will result in uneven temperature distribution along with the thickness of the weldment, leading to welding defects and ultimately affecting the mechanical properties of the weldment. To achieve the prediction of temperature distribution and the optimization of welding parameters, a simulation process model of FSW 18-mm-thick 2219 aluminum alloy is established based on DEFORM. The validity of the simulation is verified by experiments. With the minimum temperature difference in the core area of the weldment as the target value and weldable temperature range of 2219 aluminum alloy as the constraint conditions, orthogonal experiments are conducted considering the rotational speed, the press amount, the tool tilt angle, the plunging traverse speed and the dwelling time. The results of variance analysis show that the rotational speed and the dwelling time are significant factors affecting the temperature field during the plunging and dwelling phase. Through single factor simulation, the welding parameters during the plunging and dwelling phase are optimized. This study guides the selection of welding parameters of the FSW 2219 aluminum alloy thick plate.

Investigating the effect of GTAW parameters on the porosity formation of C70600 copper-nickel alloy

ABSTRACT In this study, the optimisation of welding parameters was investigated in a cupronickel alloy. The welding process was gas tungsten arc welding (GTAW) which is a prevalent method for welding pipes. The filler material type, shielding gas, and welding conditions were considered constant parameters, while heat input, shielding gas flow rate, wind flow speed and arc length were the variable parameters. In order to control variables precisely, the test coupons were assembled on a hand-made rotating machine with a controlled rotational speed. The microstructure and mechanical properties of the welded specimens were examined through the metallography and tensile test, respectively. The results showed that the optimum heat input and flow rate, which resulted in the lowest amount of porosity, were 10.2–11.3 kJ/cm and 6 L/min, respectively. It was also shown that by increasing the wind flow speed from 3 to 10 km/h, the porosity increased from 1.4% to 14.8%. In addition, reducing the arc length from 2 to 1 mm led to better weld protection and arc stability and consequently resulted in decreasing the amount of porosity from 1.1% to 0.23%. The tensile test results showed that the ultimate tensile strength of the welded specimen using appropriate parameters will be significantly reduced if improper welding parameters are used. The main reason for this decrease was the increase of porosity.

Ultrasonic welding of polyetheretherketone for dental applications

ObjectiveDue to its favorable properties, the high-performance polymer polyetheretherketone (PEEK) is used as a metal-free alternative for the fabrication of denture frameworks. For dental applications, PEEK is available in different colors, such as red or white, by compounding with different fillers. In order to permanently bond such different dental PEEK types together in a denture framework, ultrasonic welding could be a viable process.Therefore, the aim of this study was to determine the optimum processing welding parameters for welding different dental PEEK grades in terms of maximum weld strength. MethodsRectangular plates from three PEEK compounds were prepared according to the dimensions of a removable partial denture (RPD) of PEEK. These were combined in a way that four groups resulted, whereas the combination of pure PEEK served as control. In each group, 5 samples were ultrasonically welded at one of four welding energies using a microprocessor-controlled ultrasonic welder, where the welder was activated only once. Afterwards, the samples were subjected to tensile tests to evaluate the shear bond strength (SBS) of the joint. ResultsIncreasing the welding energy resulted in an increase in the welding time. Accordingly, the increase in the welding energy increased the surface deformation for all tested samples. The shear bond strengths ranged from 4.8 ± 0.68 MPa for samples welded with 50 Ws to 16.37 ± 1.69 MPa for samples welded with 90 Ws. Excessive weld energy of 130 Ws led to a significant decrease of SBS due to a severe indentation and perforation induced by the sonotrode. SignificanceThe SBS and topography of the welded samples were systematically studied and the optimal welding parameters were determined. This could serve as a reference and instruction for clinical applications.

Optimization of High Frequency Welding Parameters of PVC Coating on Polyester Fabric

This study optimized welding parameters on polyester fabric coated with PVC by applying high frequency welding technique. Taguchi experimental design was adopted in this evaluation. Three levels of width of seam and time of high frequency welding were applied and analyzed with ANOVA statistical method with α = 0.05. The optimized result shows that the input parameters providing maximum failing load for welding in warp and weft directions are the following: Width of seam (27 mm) and time of welding (12 s). The maximum failing load were 87.8 and 75.8 N/mm for warp direction and weft direction, respectively, In addition, the statistic analytical result indicated that the width of seam was the most significant factor and the predicted optimal value of failing load were 88.5 and 80.5 N/mm for warp direction and weft direction, respectively, shows that the average percentage error is less than 2 % so that the forecast equation is appropriate for the explanation of the variables for this study and provide statistical reliability. The result was verified through confirmation experiments, the high frequency welding was suitable for welding PVC Coating on Polyester Fabric.

Investigation on electron beam welding of dissimilar wrought/selective laser melting AISI 304 stainless steel plates

The selective laser melting (SLM) process gives a possibility to create complex shape parts. Joining SLM alloy parts to similar or dissimilar alloy parts can overcome some product design limitations such as limited dimensions and residual stress concentration. In this study, successful electron beam joining work on to SLM AISI 304 stainless steel plates was performed. The influence of beam current on the weld bead profile was investigated. Typical welded joints were analyzed by microstructure, microhardness, and tensile tests. The optimal welding parameters were obtained accordingly. A thorough analysis of the element and microstructure distribution in SLM and its influence on the properties of the welded joints were also investigated.

Laser Welding of 316L Austenitic Stainless Steel in an Air and a Water Environment.

Laser welding is an innovative method that is frequently used and required by different disciplines and represents a technique of choice in a wide range of applications due to important advantages such as precision, speed, and flexibility. However, the welding method must be used properly otherwise it may deteriorate the mechanical properties of the welded metal and its environment. Therefore, the laser parameters should be precisely determined and carefully applied to the sample. The primary objective of this study was to investigate and propose optimal welding parameters that should be adjusted during the neodymium-doped yttrium aluminum garnet (Nd: YAG)-pulsed laser welding of austenitic stainless steel 316L in an air welding environment by using Argon shielding gas and in wet welding settings in serum medium. The investigation of the welding process in serum medium was conducted in order to propose the most suitable welding parameters being important for future possible medical applications of laser welding in in-vivo settings and thus to investigate the possibilities of the welding process inside the human body. In order to evaluate the quality of welding in air and of wet welding (in serum), a detailed parameter study has been conducted by variation of the laser energy, the welding speed and the focal position. The relationship between the depth of penetration and specific point energy (SPE) was also evaluated. The microstructure of the welded metal was examined by an optical microscope and scanning electron microscope (SEM). Based on the microscopy results, it was found that the largest depth of penetration (1380 µm) was achieved with 19 J laser energy in air medium, while the depth reached the largest value (1240 µm) in serum medium at 28 J laser energy. The increasing energy level showed opposite behavior for air and serum. The results of our study imply that when welding of 316L stainless steel is implemented properly in the body fluid, it would be a promising start for future in-vivo studies.

Microstructural and Impact Considerations of Heat Affected Zone in Gas Tungsten Arc Welding of Armor Steel

Abstract Gas tungsten arc welding is a preferred welding process due to its excellent heat control which provides high quality joinings of various metals. Welded armor steels are widely used in armored vehicles for the ease of production. Thus, characterization of gas tungsten arc welding of armor steels reveals important data on both present applications and potential uses of gas tungsten arc welding in future. In this study, microstructural and mechanical properties of welded armor steel were investigated. Optimal welding parameters depending on a previous research were used to eliminate welding defects. The results have shown that application of pre-heating and/or multi-pass welding on armor steel could provide fine and homogeneously dispersed carbides in heat affected zone.

Artificial neural network based fatigue life assessment of friction stir welding AA2024-T351 aluminum alloy and multi-objective optimization of welding parameters

In this paper, the fracture behavior and fatigue crack growth rate of the 2024-T351 aluminum alloy has been investigated. At first, the 2024-T351 aluminum alloys have been welded using friction stir welding procedure and the fracture toughness and fatigue crack growth rate of the CT specimens have been studied experimentally based on ASTM standards. After that, in order to predict fatigue crack growth rate and fracture toughness, artificial neural network is used. To obtain the best neuron number in the hidden layer of the artificial neural network, different neuron numbers are tested and the best network based on the performance is selected. Then the fitting method is applied and the fitted surfaces that illustrate the behavior of welding are shown and the results of artificial neural network and fitting method are compared. Also, multi-objective optimization algorithm is used to obtain the best welding parameters and finally sensitivity analysis is applied to measure the effect of rotational and traverse speeds on the fracture toughness and fatigue crack growth rate.

Underwater friction-stir welding of a stir-cast AA6061-SiC metal matrix composite: optimization of the process parameters, microstructural characterization, and mechanical properties

Abstract It is an underlying fact for the case of the joining process especially welding to have optimized parameters to achieve joints with outstanding mechanical characteristics. In the current article, using stir-cast aluminum-based alloy (Al 6061) is stir-cast with Al 6061/5%wt. silicon carbide, Al 6061/10%wt. silicon carbide, and Al 6061/18%wt. silicon carbide was welded using an underwater friction-stir welding process. Optimum welding parameters [namely, tool rotating speed (N), welding speed (S), and silicon carbide (SiC)] are investigated using analysis of variance (ANOVA) and response surface methodology (RSM) statistical approaches. High ultimate tensile strength and microhardness were set as required characteristics of quality welds. Since there are two responses and two objectives, multiple-criteria decision-making approach—response surface methodology was performed alongside ANOVA. Optimal parameters from these statistical approaches are converged to a tool rotating speed of 1,736.36 rpm, a welding speed of 11.58 mm/min, and a SiC of 16.67%, respectively. For the current inquiry, the computed ultimate tensile strength and microhardness are 984 MPa and 89.9 HV, respectively, and these values are congruent with the findings of effectiveness studies. It is deduced from this study that the optimal parameters are convergent irrespective of the two used techniques for the investigated experimental data.

Optimization of welding application parameters of thin sheet blocks used in the new-generation ship hull

The main material of merchant ships is steel. Generally, block sheets used in forming a ship hull are between 7 and 12 mm. On a 60 m ship, the hull consists of approximately 25–35 mega-blocks and 45–60 blocks. Welding operations cause expansion and shrinkage on the part due to regional temperature differences. The purpose of this study is determining the optimum welding parameter of panels with 48 × 1200 cm dimensions and 5 mm thickness. Because the thickness of the sheet metal used is very thin, the blocks to be welded are very large and the mega-blocks formed by welding are used in large numbers and include uncertainties such as optimal parameters in the process application and mechanical behavior on the weld. To reduce the number of experiments within the scope of the study, welding application conditions were determined by using Taguchi experimental design (L9). In the determined parameters, submerged arc welding was carried out on the panels in a horizontal position. Taking 10 × 48 cm sections as head–middle–end from each combined panel, visual control and radiographic testing (ISO 5580) was performed. Tensile (TS EN ISO 4136) and notch-impact (TS EN ISO 9016) mechanical tests were also conducted. By conducting statistical analysis (analysis of variance) of the selected parameters used in the Taguchi experimental design, percentage effects of each parameter on yield strength, tensile strength and notch-impact tests were obtained. The impact percentage of the highest current was determined; the results were 50.24% for yield strength, 51.43% for tensile strength and 57.53% for notched-impact test results. Data means were checked with design of experiment analysis. The best welding results were obtained at parameters of 650 A, 32 V and 150 cm/min.

Welding Parameter Optimization for Improvement of Mechanical Strength of Weld Line

In this study, MIG welding parameters were optimized by experts. The results showed that heat input affected the welding of all five specimens, and similar structural changes were observed. The part adjacent to the weld line, using low HI (BM) lower than the melting point, increased the grain size and decreased the average hardness (87 HV) at HAZ. In comparison, high HI (WZ) at melting point resulted in fine grain with a high hardness of 126.8 HV and tensile strength of 686 MPa. Nevertheless, fatigue testing revealed that the specimens suffered a brittle fracture under a slight load cycle of 104 Nf. Correlation analysis of HI, mechanical properties and optimization plot revealed the optimum HI of 363 J/mm, and the verification by fatigue testing showed the optimum load cycle of 106 Nf. However, the determination of maximum strength should be done using several techniques for more effective improvement of quality and yield using the research findings of this study.

Double-Pulse Ultrasonic Welding of Carbon-Fiber-Reinforced Polyamide 66 Composite.

Ultrasonic welding of thermoplastics is widely applied in automobile and aerospace industries. Increasing the weld area and avoiding thermal decomposition are contradictory factors in improving strength of ultrasonically welded polymers. In this study, relations among the loss modulus of carbon-fiber-reinforced polyamide 66 composite (CF/PA 66), time for obtaining stable weld area, and time for CF/PA 66 decomposition are investigated systematically. Then, a double-pulse ultrasonic welding process (DPUW) is proposed, and the temperature evolutions, morphologies and structures of fractured surfaces, and tensile and fatigue properties of the DPUWed joints are measured and assessed. Experimental results show the optimal welding parameters for DPUW include a weld time of 2.1 s for the first pulse, a cooling time of 12 s, and a weld time of 1.5 s for the second pulse. The DPUW process enlarged the weld area while avoided decomposition of CF/PA 66 under appropriate welding parameters. Compared to the single-pulse welded joint, the peak load, weld area, and endurance limit of the DPUWed joint increased by about 15%, 23% and 59%, respectively. DPUW also decreases the variance in strengths of the joints.

Experimental investigation and optimization of weld bead shape factor and form factor using recycled steel slag as a flux in submerged arc welding process

The quality and productivity of welds produced depend upon the weld bead profile which is represented by weld penetration shape factor (WPSF) and weld reinforcement form factor (WRFF). The weld profile is further dependent upon welding parameters used hence optimization of welding parameters is essential. In this research work, the steel slag has been recycled to act as a flux in submerged arc welding. The effect of process parameters on WPSF and WRFF using recycled slag has been evaluated. The mathematical models have been developed from the data created. It was found that the weld deposited with recycled steel slag performs well as the WPSF and WRFF are comparable with that deposited with fresh flux. The welding parameters have been optimized using the desirability approach and genetic algorithm. The genetic algorithm yielded more accurate results as compared to the desirability approach.

Investigation of Weld Root Defects in High-Power Full-Penetration Laser Welding of High-Strength Steel

The currently available high-power laser shows promising opportunities for the welding of thick plates in a single pass. However, weld-root defect frequently occurs when a high-power laser is used to join thick plates in a full-penetration mode, which has a significantly adverse effect on the serviceability of the weld joint. The purpose of this work is to understand the defect formation mechanism and reduce these defects through controlling welding parameters. In this study, the characteristics of weld root defects were investigated using a 10 kW fiber laser using a program of experiment and theoretical analysis. The corresponding defect formation mechanisms were discussed based on the bottom molten pool behaviors observed by the high-speed camera. The results showed that there were four types of weld-root appearances as follows with an increase of linear heat input from 300 J/mm to 1000 J/mm: weld-root humping (30 mm/s), sound weld (25 mm/s), weld sagging (20 mm/s) and excessive weld sagging. The remedies for reducing weld-root defects were also presented to obtain sound weld bead by optimizing welding parameters. Weld-root humping was formed due to the quasi-full-penetration keyhole. Weld sagging resulted from the imbalance of the hydrostatic pressure and surface tension in the condition of a through keyhole. It was also found that the sound weld was formed when a through keyhole and a proper molten pool size were obtained. Thus, the state of the keyhole and molten pool geometry were the major factors that affect weld-root defects.

Optimization of continuous drive friction welding process for AA6061-T6 circular pipe and conical head

Aluminum alloy double-layer grid structure with bolt-ball joint has the advantages of light weight, corrosion resistance, convenient construction, etc. However, when circular pipe and conical head are connected by fusion welding, its strength is low. In order to solve this problem, the continuous drive friction welding (CDFW) process of aluminum alloy circular pipe and conical head and its strength of joint were studied in this paper. Based on the orthogonal experiment scheme, the CDFW experiments were conducted on AA6061-T6 circular pipe, then the tensile tests were completed on the standard samples to obtain joint efficiency under different welding parameters. The optimum welding parameters were determined by the method of variance and range analysis. The microstructure of joints was characterized by hardness test, OM, XRD, SEM, etc. The test results show that parameters affecting joint efficiency are friction pressure, rotational speed and upsetting rotational speed in descending order. Under the optimal welding process, the joint efficiency can reach 87.0%, which is superior to fusion welding. The fracture form of the welded joint is a mixture of intergranular and ductile transgranular fracture. WNZ is the crucial region of the welded joint, where the grain growth is greatly influenced by friction pressure. The friction pressure of the optimal welded joint is moderate, so the grains in WNZ are fine and grow adequately. The hardness softening of the welded joint also has certain influence on its mechanical properties. The solid solubility of the optimal welding sample is high and alloy elements are stable in the Al matrix, so it exhibits good mechanical properties. Finally, the CDFW experiments and tensile tests of circular pipe and conical head were conducted, which verifies the effectiveness of the optimal welding parameters.

OTOMOTİV SEKTÖRÜNDE KULLANILAN DİRENÇ NOKTA KAYNAK İŞLEM PARAMETRELERİNİN KAYNAK MUKAVEMETİ ÜZERİNE ETKİLERİNİN İNCELENMESİ

The most widely used welding joining method in the automotive industry is resistance spot welding. Resistance spot welding (RSW) is the welding area where heat is produced by the effect of resistance against the flow as a result of exposing the welded parts to a local electric current. It has become an important issue to apply an effective approach method to guarantee weld quality and optimize welding parameters. This is of high value in theory and practice. In the literature, the effects of spot welding process parameters on the weld core diameter and electrode penetration depth are mostly investigated. Weld strength in RSW is affected by many process parameters such as applied electric current, compression force, welding time. Due to the contact resistance and joule heating, a molten weld nugget zone is formed on the work pieces. It is desirable to have the maximum temperature at the interface of the parts to be joined. In practice, the production of welds of acceptable quality depends on the definition of optimum weld parameters and the application of appropriate controls to ensure constant weld quality over a long production period. In the experimental studies, the optimization of the welding parameters was studied in order to obtain the maximum tensile-shear strength. The most prominent process parameters in experimental studies are electrode force, welding currents and welding times. Different algorithms have been developed for the optimization of welding parameters. The verification tests clearly show that it is possible to increase the tensile-shear strength of the connection with the combination of appropriate welding parameters. As a result, the experimental results confirm the validity of the algorithms used to improve welding performance and optimize welding parameters in resistance spot welding processes.

The effect of aluminum interlayer on weld strength, microstructure analysis, and welding parameters optimization in resistance spot welding of stainless steel 316L and Ti6Al4V titanium alloy

Stainless steel (SS) and Titanium alloy (Ti) are the most commonly used materials in many industrial fields such as the automotive and aerospace industry. Stainless steel has good corrosion resistance and titanium alloy has an extremely lightweight characteristic. The combination of both materials has become a tremendous innovation in the industrial sector. Resistance spot welding which has commonly applied in many industrial fields is a good consideration to join these two dissimilar materials due to the high efficiency that could be achieved by using this method. However, the way of joining these dissimilar materials should be carefully considered due to the significant difference in mechanical properties between SS and Ti. In the present study, 3 mm of SS316L and Ti6Al4V sheets were joint under the resistance spot welding method with an aluminum interlayer. The optimized welding parameters were provided under the Taguchi method L9 orthogonal array along with the mechanical properties’ investigation. The optimum welding parameters were 11 kA of weld current, 30 Cycles of welding time, and 5 kN of electrode force which produced 8.83 kN tensile-shear load of the joint. The mechanical structure analysis shows the different morphology between stainless steel and titanium interfaces and the intermetallic compound layer was formed on the SS/Al and Al/Ti interfaces. The EDX analysis shows the atomic diffusion-reaction on the application of aluminum as an interlayer on the SS/Ti joint.

Simulation of tensile properties of a friction stir welded Al-Si-Mg aluminum alloy

The mechanical and microstructure properties of a friction stir welded (FSW) joint is dependent on tool design and the welding parameters. A systemic randomization and optimization of processing and welding parameters can produce welds with little or no defects with improved properties. The tensile properties of aluminum AA6082 alloy fabricated through the friction stir welding technique was simulated using the finite element model (FEM). The investigation was specifically based on the weld zone (WZ) for both the mechanical characterization and the computational modeling. The weld nugget is the region of complete deformation and recrystallization. A severe plastic deformation was experienced by the materials; hence, there is a visible microstructural evolution. The finite element modeling (FEM) of tensile properties, was computationally performed with a commercial software program, MSC MARC. The generated data was validated by the experimental results under tensile-loading conditions (i.e., maximum stress). Approximately 70 % weld strength was used as reference for the validation process while FEM was implemented under optimum processing parameters to predict the integrity of the produced welds. The maximum values of the equivalent Von Mises was approximately 12 % below the measured UTS for all the samples. This can be attributed to a strong bond between the molecules of the base metal while in solid state. A good exactness of the simulated and the experimental values validates the 3D model.

Optimization of FSW process parameters for welding dissimilar 6061 and 7075 Al alloys using Taguchi design approach

Friction stir welding (FSW) produce a strong metallurgical joint with the application of severe deformations and frictional heating in the metals and alloys by using a non-consumable rotating tool consisting of pin and tool shoulder. During welding, the plastic deformations of base metals vary for the varying mechanical properties such as tensile strength (TS), impact strength (IS), and hardness (HV) which in turn varies the welding conditions and parameters. Therefore, selection of optimal weld parameters plays an important role in enhancing the quality of weld joint. In this article, friction stir butt welds made of 6061 and 7075 Al alloys are performed with various welding parameters such as rotational speed of tool, angle of tilt, and axial force using tool has taper pin profile. Experiments are carried out on twenty-seven joints that are made on 6061 and 7075 Al Alloy plates of 6.50 mm thick of same nature and tested for its tensile, impact and HV properties.