Weld Area Research Articles

Laser Weld Aspect Optimization of Thin AISI 316 SS Using RSM in Relation with Welding Parameters and Sulfur Content

A quantitative and qualitative study of the effect of laser (light amplification by stimulated emissions of radiation) welding parameters, such as focus point, welding speed, power beam and shield gas on bead profile in relation with microchemistry compositions differences of two thin AISI 316 industrial stainless steel casts have been studied. One cast contains 60 ppm (0.006%) of sulfur considered as high sulfur content and the other one contains 10 ppm (0.001 %) sulfur which can be considered as low sulfur content. A set of 27 tests were carried out by combining three welding speeds (1500, 3000, and 4500 mm/min), three shield gases (helium (He), mixture of 40% helium and 60% argon (Ar) and mixture of 70% helium and 30% argon) with flow rate of 15 L/min, and three focal lengths (+2, +7, and +12 mm). The depth, aspect ratio (the ratio between the penetration depth weld and the weld width) and the bead cross section profile are investigated using response surface methodology (RSM). Linear and quadratic polynomial models for predicting the weld bead geometry were developed. The results of the preliminary validation indicated that the proposed models predict the responses adequately. The geometry of the welded area was analyzed using optical microscopy, and correlations between weld morphology (depth, weld aspect parameter and weld area) and welding parameters were performed. For the cast 316 HS (high sulfur content), the main input factor influencing the depth weld (Yd) is the focus point with a contribution up to 19.32. On the other hand, the main input factor affecting the depth weld (Yd) of the cast 316 LS (low sulfur content) is the combination effect of focus point and power input energy with contribution up to 10.65%. Sulfur as the surfactant element contributes to determining the laser weld bead shape up to 71% when the welds are partially penetrated and diminishes to 50% when the welds are fully penetrated with the occurrence of the keyhole mechanism.

Effect of welding current on the microstructural evolution and lap-shear performance of resistance spot-welded 340BH steel

In this study, we used experimental characterizations and finite element analysis (FEA) techniques to investigate the effect that welding current exerts on the microstructural features and mechanical properties of bake-hardened (BH) steels. Resistance spot welding (RSW) experiments were conducted using 5.0 and 7.0 kA of welding current. The microstructure across the weld regions was analyzed using optical microscopy (OM) and electron backscatter diffraction (EBSD). FEA was employed to simulate the RSW process, predict nugget dimensions, and determine cooling rates. The results of the OM analysis showed that nugget size increased with an increase in the welding current, and EBSD characterization revealed similar microstructures under both levels of current, but significant variations were observed within weld zones. Lath martensite formed as a result of rapid cooling in the fusion zone (FZ). Whereas, fine and coarse grains were found in the heat-affected zone (HAZ). In addition, the formation of lath martensite in the FZ resulted in high hardness on a 2D map of microhardness. The welding current had no substantial effect on microhardness, but it did impact the mechanical properties under lap-shear test conditions, which resulted in significant changes in the fracture mode. The deformation and fracture behavior of spot-welded specimens was studied using a lap-shear test coupled with 3D digital image correlation (DIC). The experimental results indicated a fracture in the 5.0 kA current samples near the FZ/HAZ boundary, while 7.0 kA welding current resulted in base metal (BM) necking and tensile fracture. FEA was also employed to elucidate the local deformation properties and fracture modes during lap-shear testing. The results of this study show that nugget size has no effect on a failure site during lap-shear loading, but size does affect the nugget load-carrying capabilities. The failure behavior was influenced by the microstructural properties of the distinct weld areas.

Weld corrosion of GH3535 in molten (Li,Na,K)F

The corrosion of structural materials in molten fluoride salts restricts the development of a molten salt reactor (MSR), with local galvanic corrosion of the weld joint being one of the major failure modes associated with the structural materials in the operating environment of an MSR. In this paper, in situ electrochemical measurements, combined with scanning electron microscopy (SEM/EDX) and metallographic microscope testing methods, are used to study the weld corrosion of GH3535 at 700 degrees C in molten (Li,Na,K)F. The results show that each part of the welding areas is in active dissolution state at the open circuit potential. The electrochemical behavior of the heat affected zone is similar to that of the GH3535 parent material. When the weld zone of the GH3535 is coupled with the parent alloy, galvanic corrosion occurs and the galvanic corrosion effect is larger than 1.

Investigation of Post-weld Heat Treatment of Laser Welded Ti6Al4V Materials

In this study, the changes in the internal structure and mechanical properties of laser-welded Ti6Al4V material after heat treatment were experimentally investigated. The transformation temperatures of the α and β phase structures of the Ti6Al4V material influenced the heat treatment temperatures. Optical microscopes, XRD, and SEM experiments were performed to detect the microstructural change. Hardness and tensile tests were also carried out to determine the change in mechanical properties. The experimental study determined that the mechanical properties of laser-welded Ti6Al4V material improved after heat treatment. It was observed that ductility and strength increased significantly at heat treatment temperatures above the β phase temperature. It was determined that the Widmanstatten morphology visible in the weld area increased the hardness.

Influence of preheating on residual stresses in ultra-high strength steel welded components

Preheating is generally required in the welding of ultra-high strength steels (UHSSs) for avoiding cold cracking. The present work systematically explores the influence of preheating on welding residual stresses (WRS) in components made of UHSS by means of both experiments and numerical simulations. The results reveal that, no matter what UHSS is with or without metallurgical phase transformation, preheating has a great influence on the magnitude of transverse residual stress (σT-RS). In general, the higher preheating temperature (TPH) the lower magnitude of σT-RS is. Preheating would change the longitudinal residual stress (σL-RS) sign in the weld area and σL-RS amount obviously diminishes with the increase of TPH for transforming UHSS, while that has nearly no influence on the maximum σL-RS but has an impact on the area of tensile σL-RS for non-transforming UHSS. The effect of entire preheating and partial preheating on WRS in UHSS welded components could be nearly the same. Nevertheless, TPH in the partial preheating case (about 300 °C here) should be higher than that in the entire preheating one (corresponding 100 °C here) for that same effect. The weld dimensions, especially the size of the heat-affected zone (HAZ), and cooling time Δt8/5 significantly increase with TPH. Preheating has almost no influence on the restraint degree of welded components.

Mechanical Properties Of Welding API 5l X-65 Cladded UNS N08825 Material Due To The Effect of Welding Repair

Abstract This study evaluate the mechanical characteristics and microstructure of API 5L X-65-clad UNS N08825 during repair welding. Gas tungsten arc welding (GTAW) and shielded metal arc welding were used in combination to carry out the welding and the repair welding (SMAW). Filler metals ER NiCrMo3 and E NiCrMo3 were used throughout the GTAW and SMAW welding processes. The first specimen served as the primary focus, after which the weld areas of the remaining four specimens were ground, re-beveled, and then re-welded using the same parameters. It performed tensile testing, bending tests, Impact Charpy tests, macro photography tests, and Vickers hardness tests. Repairs weld carried out, the heat-affected zone's hardness in the capping region increased. The findings of the tensile test demonstrate that the tensile strength is not considerably impacted by the welding repair at any particular welding repair location. The biggest decline in the number is caused by the welding repair at PTR 2, which is 0.83 percent. The heat affected area (FL) value decreased by 10.44 percent according to the charpy impact test results. The PTR 1 and PTR 2 areas in the weld metal area had the lowest charpy impact test results, respectively, of 88 J and 258 J.

Topological optimization of magnetic pulse welding coils for maximizing the effective weld area with a discretized differential evolution algorithm

A topologically constrained optimization methodology associated with a discretized differential evolution (DE) is employed for the structure design of a magnetic pulse welding (MPW) coil. To reveal the explicit expression for the effective welding area produced by the MPW process, the impact angle and collision velocity are innovatively considered for determination of the objective function. As several disconnected regions are generated by the Rand-to-Best/2/exp mutation strategy and subsequent superposition-style crossover operation, the algorithm is combined with geometrical correction to form a simply connected conductor. The proposed algorithm is effective and robust as it have been verified based on the evolutionary history and numerical trials with coupled electromagnetic–mechanical simulations. According to physical validation results, a wider effective welding area is produced between aluminum alloy and steel planar plates by the optimized coil, which results in better performance in a tensile test. Under a 23 kJ discharge current, the maximum loading is significantly enhanced by 46.21% compared with the original coil.

Influence of initial residual stresses on welding residual stresses in ultra-high strength steel S960

In general, the as-received steel components before welding have usually suffered from numerous manufacturing processes. There is no doubt that initial residual stresses (IRS) remain in the steels with different magnitudes and even signs if no any stress-relieving process is applied before welding. Nevertheless, the relationship between IRS and welding residual stresses (WRS) is still not unclear yet, especially in ultra-high strength steels (UHSS). The current work aims to elucidate the influence of IRS on WRS in ultra-high strength steel S960. The X-ray diffraction (XRD) was applied to measure both IRS and WRS here. The experimental results exhibit that IRS in the weld area are completely eliminated because of the metallurgical and mechanical melting effect, which have no influence on WRS. In the heated zone out of the weld area, initial longitudinal residual stress (σRSL) can significantly affect welding σRSLonly if it is in tension. In the cold area, WRS are the combination of IRS and welding-induced residual stresses (WIRS). Furthermore, IRS play the dominant role here in general. No matter how much and what sign IRS are in the cold area, IRS here almost have no impact on WRS in the weld area.

Defect detection method for high-resolution weld based on wandering Gaussian and multi-feature enhancement fusion

As the weakest point of the pipeline, the weld seam is prone to various internal defects and has great safety risks, so it is necessary to conduct a weld seam inspection. In addition, accurately detecting small-sized defects from high-resolution and low-contrast X-ray images is still a challenging task. Therefore, this paper proposes a defect detection method for high-resolution weld images, including three steps: welded extraction, weld restructuring, and defect detection. Because the resolution of the original image is high and the defect features are mainly concentrated in the weld area, it is not easy to directly defect detection. Firstly, a new irregular long weld extraction algorithm based on wandering Gaussian was designed. Secondly, because the existing welding seams aspect ratio is large and the information loss of conventional compression methods is serious, a new feature reorganization method was provided to maximize the effective information of the weld. Finally, a new method of welding defects detection method based on cross-layer feature fusion has been redesigned to take into efficiency and accuracy. The experiments show that the proposed method achieves the best detection performance on the public GDXray dataset compared with other advanced defect detection methods, from which it can locate the weld defects automatically and fast with high accuracy. It provides an effective solution for high-resolution weld defect detection.

Thermal Effect of Bobbin Tool Friction Stir Welding on the Mechanical Behavior of High Density Polyethylene Sheets: Experimental Study

Bobbin friction stir welding (BT-FSW) is a variant of the conventional friction stir welding (C-FSW). This method has been applied of welding high density polyethylene (HDPE) plates; where a rotating symmetrical tool causes a fully penetrated bond, it can weld the upper and lower surface of the work-piece in the same pass. BT-FSW process involves complex heat generation and HDPE flow, which directly affects on the weld area and on mechanical properties of welded joint. Heat generation and material flow during BT-FSW are significantly affected by the tool design features, process parameters and mechanical behavior of work piece materials. Studying the temperature of polyethylene sheets welded by BT-FSW can help in analyzing the mechanism of weld formation and also can provide theoretical guidance for the tool design, process parameter selection and even new process development. In the unique work described in this paper, the 11.4 mm-thick HDPE plates were welded successfully by bobbin-tool friction stir welding. Measurements of the material temperatures were performed by thermocouples which are placed near and at the weld seam. The weld quality was determined in terms of no defects in the stir zone and the tensile strength of the joint. It was found that considerable melting occurred between the rotating shoulders and on the trailing side of the rotating pin. Movement of the molten material by the rotating tool created a very black band in the stir zone. Thermocouples measurements indicated that the temperatures were higher on the advancing side (AS) compared to those on the retreating side (RS). Tensile tests and hardness measurements were performed on welded and seamless sheet samples. The results were analyzed to compare the mechanical properties. To demonstrate the variation in micromechanical properties between welded and seamless sheet samples, micro hardness (HV) testing was used to explain the difference. The HV of the HDPE plates weld by BT-FSW, were relatively symmetrical with respect to the parting line. The maximum hardness levels were reached in the weld bead at around 66 HV in the welded nugget; there was a rise in the level of hardness, in particular at retreating side (RS) and at advancing side (AS) where the value reached 68.60 HV.

Mechanical and microstructure characteristics of 7475-T7351 aluminium alloy joints welded by robot cold metal transfer

The purpose of this research is to analyse the microstructural parameters, as well as mechanical properties of robotic CMT, welded AA7475-T7351 alloy. The welded joint’s morphology and evolution, as well as its mechanical properties and also fracture behaviour, were studied. In contrast to the weld, the base metal carries the maximum tensile strength. The weld metal (WM) has the lowest hardness, just 58.24% of the base metal (BM). The general microstructure of the weld area was studied for the welded joint. Weld fractography revealed a high number of equiaxed dimples uniformly spread over the fracture surface, as evidenced by scanning electron microscopy (SEM) micrographs and a corresponding energy dispersive X-ray (EDX) of the weld.

P‐99: Development of Deep Learning Models for FMM Welding Point Qualification

Fine Metal Mask (FMM) is the core technology of the evaporation process (EV) in manufacturing AMOLED panels [1]. The FMM made by the welding process. As the AMOLED's resolution becomes higher, the FMM becomes thinner, and the inspection system for securing the welding reliability becomes an issue in the FMM manufacturing process. Currently, inspection is conducted manually on random samples thus it is impossible to inspect all welds. In this study, the red‐dot labeled image training model was developed to automatically classify and determine weld defects, thereby enhancing the detection consistency of welds. This paper applies weld‐defect‐qualification‐function based on deep learning for FMM mass production process. The ‘Red‐dot labeled image training method' draws a red point in the center of the weld and separates the red‐channels. The separated channels are used as labeled images for learning. The problem is that if the model learns the welds directly, a detection error that catches the wrong area occurs, and the welding area is not correctly cropped. Additionally, the image processing and OpenCV's contour are errors occur by the image's contrast or facility light condition. On the other hand, the weld area can be correctly cropped by the red‐dot training model, even only with 1 pixel. The effect of this technology is to solve the problem of defect leakage and deviation of workers resulting from the existing manual sampling inspection, and to make a consistent qualification and automatic full inspection based on the deep learning model. Through this paper, the problem of full‐automation‐inspection, which was not possible in the past, is solved and the foundation of the inspection technology applicable to mass production is established.

Hot tapping process analysis on gas distribution pipes online service using Shielded Metal Arc Welding

In a piping system makes it possible to add branching into an existing piping system. In this research will discuss about installation 12 " branch pipe in to 16” existing pipe. The system should be installed without interrupting the operation of the pipeline to avoid huge losses. Hot-tapping is a technology that works to create branching on the online service pipe condition. Calculation and analysis of the results to ensure the process of hot-tapping absolutely safe to operate. parameters that must be considered include the heat input, the operating pressure during welding hot-tapping process with Shielded Metal Arc Welding, stress that occurs at the branching system. Analysis on split tees must be done because of stress that occurs due to the welding process and the reduction in thickness. Analysis on the plumbing system must be done because of a new branching thus causing new stress. The results of the analysis on split tees and the pipe system is used as a reference-making procedures for implementing hot-tapping. Maximum stress that occurs in the pipes during hot-tapping process is the welding area (22.828 psi). The welding process causes melting partial in the metal pipe so, during welding process (hot-tapping) working pressure should be reduced by 25.27%. The condition of the fluid in the existing pipeline still safe because liquefaction as a result of the welding process does not penetrate to the inner pipe. The new design results in branch pipe eligible to fabricated because stress that occurs is still below the allowable stress values

Finite element simulation prediction of repeated bending failure zone of roll-welded bellows based on an equivalent welding model

In this paper, an equivalent welding model is proposed that takes the tensile stress and strain parameters of the axial weld area of the roll-welded bellows as the material properties to replace welding simulation. The integrated finite element method is used to simulate the following two model forming processes for the roll-welded bellows: (i) welding-bulging-repeated bending model, and (ii) equivalent welding-bulging-repeated bending model. The stress and strain distributions of the two models are compared and analyzed, and the main failure areas of the roll-welded bellows in the repeated bending process are predicted. At the same time, the accuracy of the model prediction is verified by the limited repeated bending test of the roll-welded bellows, and the failure mechanism of the roll-welded bellows is revealed. The results indicate that the stress and strain distributions of the two models are essentially the same, thus verifying the feasibility of the equivalent welding model. When the cyclic deformation reaches the limit, the predicted stress failure risk zone is located at the base metal position of the first wave-like trough of the bellows near the heat affected zone at the fixed end, which is consistent with the experimental results. This indicates that the equivalent welding-bulging-repeated bending model can accurately predict the position of the repeated bending fatigue failure of the bellows, thus laying a foundation for the optimization of the roll-welded bellows.

PENGARUH LAJU ALIR TUNGSTEN IN-ERT GAS TERHADAP KEKUATAN TARIK DAN KEJUT PADA SAMBUNGAN LAS TIG BAJA GALVANIS DAN ALU-MINIUM 5052 DENGAN FILLER AL-SI 4043

This study aims to determine the effect of the protective gas flow rate on the tensile and shock strength of welded joints of dissimilar metals, namely aluminum 5052 – galvanized steel with Al-Si 4043 filler using argon gas as a shielding gas. The protective gas flow rate parameters used in this study were 14, 17, and 20 liters/minute with a current of 80 A. The results showed that the higher the flow rate of the shielding gas, the lower the porosity defects that occurred in the welding results, resulting in higher tensile and shock strength values. Based on the analysis through the results of penetrant testing, it shows that the addition of the protective gas flow rate is given to reduce the porosity defects in the welding area. The surface area experiencing porosity decreases with the addition of the protective gas flow rate of 14, 17, and 20 liters/minute of 59.748%, 50.918%, and 48.857% respectively. The highest tensile strength was obtained from welding with a protective gas flow rate of 20 liters/minute of 20.01 MPa, then a protective gas flow rate of 17 liters/minute of 16.32 MPa, and the lowest at a protective gas flow rate of 14 liters/minute of 10 ,44 MPa. The highest shock strength is obtained from welding with a protective gas flow rate of 20 liters/minute of 0.5644 mJ/mm2, then a protective gas flow rate of 17 liters/minute of 0.4048 mJ/mm2, and the lowest is a gas flow rate protection 14 liters/minute of 0.2981 mJ/mm2.

Amendments of weld formation in human skin laser soldering.

A computational modeling is employed for quantitative assessment of weld formation and area of tissue temperature necrosis during the human skin laser soldering. The evaluation is carried out depending on the components composition of using solders, including bovine serum albumin (BSA), indocyanine green (ICG), and carbon nanotubes (CNT), as well as the angle of incidence of laser light and its pulse duration. The influence of CNT on the change of thermodynamic characteristics of albumin denaturation and the rate of formation of the laser weld is investigated. The obtained results suggest to limit the duration of laser light pulse by temperature relaxation time to minimize transfer of thermal energy to reduce the heating of human skin tissues. The developed model has a great potential for further optimization of laser soldering of biological tissues technology with greater efficiency in minimizing the weld area. This article is protected by copyright. All rights reserved.

An automatic exposure imaging and enhanced display method of line scan camera for X-ray defect image of solid rocket engine shell

During the long-term operation of solid rockets and equipment welding, some invisible defects will appear inevitably. These defective work pieces will bring major safety hazards during service. Based on the designed imaging device, this paper proposed two new automatic-exposure imaging methods suitable for line scan cameras. An efficient feature statistical welding positioning method was designed to ensure the best imaging quality of the effective welding area. To improve the identification of defect information, a new adaptive high-grayscale pseudo-color enhancement algorithm, dynamically updating the number of quantized colors, was designed. The experimental results show that the automatic exposure algorithm of the line scan camera not only can effectively achieve high-quality imaging of X-ray film, but also can greatly shorten the scanning time and improve the scanning efficiency of the X-ray film. The proposed algorithm has been well applied in the high-definition X-ray film digitization equipment developed.

Effect of inertia friction welding speed on microstructure and mechanical properties of 2205/316L stainless steel joints

In this paper, inertia friction welding (IFW) is used to enable a high-quality and efficient joint between 2205 duplex stainless steel and 316 L stainless steel. Specifically, stainless steel bars (2205/316 L) with a diameter of 35 mm and length of 120 mm are used. In addition, the effect of IFW speed on the microstructure and properties of welded joints is assessed using scanning electron microscopy, electron backscattered diffraction, energy dispersive X-ray spectroscopy, microhardness test, and tensile tests. The results indicate that dynamic recrystallization of the microstructure of joints occurs during IFW welding, which causes grain refinement. The diffusion of Ni from the 316 L base metal to the 2205 base metal, as well as the diffusion of Cr from the 2205 base metal to the 316 L base metal, results in a strong metallurgical bond between the two materials. In addition, the microhardness of the welding area exceeds that of the base metal (the closer to the weld zone, the greater the microhardness value). The tensile strength of the joints initially increases with increasing IFW speed, but then it starts decreasing beyond a certain point. The optimal welding parameters for achieving high-quality joints between 2205 duplex stainless steel and 316 L stainless steel are as follows: axial pressure = 5 MPa, rotational inertia = 4.17 kg·m2, and IFW speed = 2700 r/min.

An evaluation of mechanical properties and estimation of environmental reduction factors in welded API X70 steel pipeline in natural seawater

Due to the detrimental effect of damage induced by seawater in pipeline structures, there is a need to investigate the effects of natural seawater and air environments on mechanical properties of representative pipeline materials, to obtain useful data for estimation of their service lives. Hence, in this work, a X70 steel pipeline plate was welded using submerged arc welding technique; and subjected to air and natural seawater environments. Test specimens were soaked in seawater for twelve months at 28 °C. The parent plates, weld regions and the heat affected zones were investigated by evaluating their mechanical properties and fracture surfaces. The experimental findings revealed that the tensile strengths of parent and weld were 634.00 MPa and 674.00 MPa respectively, while the compressive stresses were 750.10 MPa and 750.40 MPa respectively with highest hardness value of 239HV. The findings also revealed that weld area and heat affected zone depend on material thickness, heat input and possible effect of residual stresses in the weldment. The fracture surfaces of test specimens showed combination of brittle and ductile failure mechanisms. Comparison of the test results revealed that seawater had significant effect on the mechanical properties and surface morphology of the API X70 steel pipeline with respect to immersion time.

Metallurgical, mechanical and corrosion behaviour of pulsed and constant current TIG dissimilar welds of AISI 430 and Inconel 718

This research work explore the weldability, structural integrity, mechanical properties and corrosion behaviour of dissimilar welds of Inconel 718 and AISI 430 developed by using constant and pulse arccurrent modes in TIG welding process. The welded structures defects for inspected by employing X-ray radiography images as well as macrostructures. Metallurgical changes were observed using optical & scanning electron microscope techniques. Mechanical properties of the joined structures were evaluated by performing tensile test on UTM and hardness measurements on weld surfaces using Vickers hardness tester. The resistance against the corrosion especially at the weld area of both welded structures was measured. The joined structures were free from flaws and also seen the uniformity of the filler distribution towards the base metals. The grain coursing with well-defined grain structures were identified in CC-TIG weldmentswhereas fine grains with clear distribution of filler alloying elements were seen in PC-TIG weldments. PC-TIG weldments exhibited with better mechanical and corrosion resistance properties than the CC-TIG weldments vowing to pulse arc mode during welding process. The aerospace and nuclear industries will benefit from the study's findings especially turbine disc and shaft assembly.