Post-weld Process Research Articles

Control of the Weld Heterogeneity by Using a Novel Counter Variable Pin Shoulder Rotation Friction Stir Welding: A Simulation and Experimental Study

Abstract Friction stir welding (FSW) produces inhomogeneous mechanical and metallurgical properties in the weld, which further require post-weld processing to control the heterogeneity. In the present study, the heterogeneity in the weld is reduced through counter-variable rotation friction stir welding (CVRFSW). The material flow and temperature distribution significantly affect the inhomogeneity of the FSWed properties which has been studied by developing a three-dimensional Lagrangian method-based viscoplastic model. The material flow, strain rate, and temperature distribution in conventional FSW (CFSW) and CVRFSW are studied quantitatively. The study revealed that CVRFSW improved joint strength and reduced the inhomogeneity of temperature, strain, and hardness. At a 10% lower shoulder speed than a pin, the weld strength improved by 16%. The simulation predicted that the temperature difference between the advancing side (AS) and the retreating side (RS) was 36 °C in CFSW, which was reduced to 8 °C in CVRFSW. Material deformation in CVRFSW occurred at a strain rate more than twice that of CFSW, and the asymmetry of strain rate between AS and RS reduced to one-fifth. Microstructures and their orientations of the welds were studied in detail. These findings contribute to the understanding of CVRFSW processes for enhanced weld quality and mechanical performance for industrial applications.

Combining electric discharge surface alloying and high-frequency mechanic impact post-processing for increased corrosion fatigue life of as-welded transverse non-load-carrying attachments of the S355 steel

The combined effects of severe plastic deformation induced by high-frequency mechanical impact (HFMI) treatment and the electric discharge surface alloying (EDSA) with chromium on the corrosion fatigue life of low-carbon S355 steel transverse non-load-carrying specimens are studied in this paper. First, for various alternations of the combined HFMI + EDSA process, the surface alloyed layer integrity and depths were analyzed using scanning electron microscopy (SEM) accompanied with energy dispersive spectroscopy (EDS) and hardness measurements. The alloying and hardening depths were respectively observed to be 10–30 μm and 0.15–0.75 mm and the surface hardness increased up to 3.6–3.9 GPa. Polarization tests demonstrated higher corrosion resistance of the EDSA-processed samples in 3%NaCl. The near-surface layers of the HFMI + EDSA(Cr) + HFMI processed sample characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) contain the dislocation-cell structure formation and partially dissolved cementite. The fatigue tests in 3%NaCl confirmed that the HFMI + EDSA(Cr) + HFMI post-weld process increased corrosion fatigue life (1.77 × 106 cycles) of the S355 steel welded joint at the stress level of 260 MPa by 2 and 12 times in comparison with the HFMI-treated (0.9 × 106) and as-welded (0.14 × 106) samples, respectively.

A Survey on Post-Weld Modification of Microstructural and Mechanical Properties of GTAWed Aluminum Butt Joints Through FSP and T6 Heat Treatment

Ergitme kaynağı ile birleştirme endüstrinin her alanında yaygın olarak uygulanan imalat yöntemlerindendir. Özellikle yüksek ısıl iletim ve genleşme katsayısına sahip, sıvı halde hidrojen çözünürlüğü yüksek olan ve yüzeyinde rijit oksit tabakası bulunan alüminyum alaşımlarının ergitme kaynağıyla imalatında iri tane oluşumu, mekanik özelliklerde düşüş vb. olumsuzluklar gerçekleşebilmektedir. Bu nedenle ergitme kaynaklı birleştirmelerin ömürleri ve mukavemetleri açısından kaynak sonrası işlem ile kaynak bölgesinin iç yapı ve mekanik özelliklerinin iyileştirilmesi çoğu uygulama için önemli rol oynamaktadır. Çalışmamızda, tungsten inert gaz (TIG) kaynağı ile birleştirilen AA6082-T6 plakaların kaynak bölgesi özelliklerine kaynak sonrası işlem olarak uygulanan sürtünme karıştırma prosesi (SKP) ve T6 ısıl işleminin etkileri araştırılmıştır. SKP ve T6 ısıl işleminin mekanik özelliklere ve iç yapıya etkileri çekme testi, mikrosertlik testi ve mikroyapı incelemeleri ile araştırılmıştır. SKP ile kaynak dolgusunun işlem gören bölgesindeki (karıştırma bölgesi) dendritik tanelerin parçalanarak ince taneli iç yapının elde edildiği tespit edilmiştir. Bununla birlikte, SKP’nin malzemede oluşturduğu ısıl girdi ile ısıdan etkilenen bölgenin (IEB) genişlemesine ve sertliğin daha geniş bölgede düşmesine sebep olduğu gözlemlenmiştir. Kaynak sonrası uygulanan T6 ısıl işlemi ile kaynaklı birleştirmenin mekanik özelliklerin arttırıldığı ancak tokluğunun azaldığı gözlemlenmiştir.

The Effects of Postweld Processing on Friction Stir Welded, Additive Manufactured AlSi10Mg

Given the limited build volumes for most current additive manufacturing (AM) machines, a method for taking advantage of the unique capabilities offered by AM while combining it with traditional manufacturing methods is needed. Welding of AM-produced components is a solution to this challenge. The objective of this study was to determine the feasibility of using friction stir welding (FSW) to join AlSi10Mg melted with laser powder bed fusion (PBF-L) and examine the effects of postweld heat treatment (HT) and hot isostatic pressing (HIP) on overall joint quality and mechanical performance. Samples were examined using optical microscopy, scanning electron microscopy, hardness testing, and tensile testing. Examination of the samples that underwent a postweld annealing HT revealed cracking along the stir zone and the thermomechanically affected zone (TMAZ) boundary. Examination of the crack revealed evidence of liquation near single-phase silicon precipitates in the TMAZ despite the annealing temperature being 27°C (81°F) below the solidus temperature of the material according to the material specification. Using a calculated pseudobinary phase diagram of AlSi10Mg, the annealing HT was determined to be in the partial liquation regime for AlSi10Mg. The voids and crack formation mechanisms were determined to be caused by constitutional liquation coupled with the unique TMAZ microstructure and stress state. The as-welded and HIP coupons were void and defect free, and FSW was determined to be a feasible method of joining PBF-L aluminum alloys with minimal knockdown in tensile strength.

Microstructure and mechanical properties of underwater friction stir welding of CNT/Al-Cu-Mg composites

The friction stir welding (FSW) joints of CNT/Al-Cu-Mg composites have severe flash defects and softening phenomena due to the excessive heat input. In this paper, underwater friction stir welding (UFSW) was used to transfer the heat input and increase the cooling rate of the joint, which was beneficial to suppress the coarsening of the strengthening precipitates in the thermal mechanically affected zone (TMAZ) and narrow the range of TMAZ. The DIC results demonstrate that the joints obtained by UFSW alleviate the strain concentration in the TMAZ. The nugget zone (NZ) with outstanding performance could synergistically engage in plastic deformation. Thus, the mechanical properties of the UFSW joint increase to 523 MPa, reaching 94.7% of the CNT/Al-Cu-Mg composites, providing further improvement of the FSW joints. Additionally, the flash defects have been improved due to the descent of the thermal cycle, which alleviates the difficulty of post-weld processing and promotes welding efficiency.

Research Status of Post-welding Treatment Process for Welded Joints

Research Status of Post-welding Treatment Process for Welded Joints

A comprehensive review on the effect of precipitation on mechanical properties of friction stir welded aluminium alloys

Friction Stir Welding (FSW) is one of the excellent metals joining processes in terms of joint strength efficiency, quality of the weld and eco-friendliness. The strength of the joint and quality of the weld depend upon the FSW processing parameters. This paper aims to provide overview of the FSW process by considering the effect of alloying elements and its precipitates on mechanical properties of aluminium and its alloys. The importance of grain growth and its effect on mechanical properties after welding is also analysed and discussed in detail. The interesting observation is that the precipitates and its size, residual stress play an important role in changing the hardness, tensile strength and fatigue strength across the weld zones. In general, the hardness of the stir zone is lesser when compared to base metal and this is noticed for all series of aluminium and its alloys, irrespective of the precipitates and its structure. Grain size and its morphology also have significant role in affecting the mechanical properties of the welded joint and it is found that post welding process has noticeable effect on the mechanical properties closer to base aluminium and its alloys.

Improving the Quality of Friction Stir Welds in Aluminium Alloys

The Stationary Shoulder Friction Stir Welding (SS-FSW) technique benefits from reduced heat input, improved mechanical properties and surface finish of the weld, avoiding the need for post weld processing. Coatings on the tool probe and the shoulder for welding of aggressive Aluminium alloys have rarely been successful. Such coatings must be well adherent and inert. In this study, coated tools were used for SS-FSW of AA6082-T6 alloy. Performance of a nanoscale multilayer TiAlN/VN coating deposited by High Power Impulse Magnetron Sputtering (HIPIMS) technology was compared with amorphous Diamond Like Carbon (a-C:H) by Plasma Assisted Chemical Vapour Deposition (PACVD), AlTiN deposited by arc evaporation and TiBCN along with TiB2 produced by Chemical Vapour Deposition (CVD) methods. The TiAlN/VN coating was found to have low affinity to aluminium, acceptable coefficient of friction and provided excellent weld quality by inhibiting intermixing between the tool and workpiece materials resulting in a significant reduction in tool wear.

Optimizing the process parameters in Friction stir Spot Welding Of Dissimilar Aluminum Alloys Using Genetic Algorithm

Welding of dissimilar aluminum alloys by Resistance spot welding and Self-piercing rivets requires high energy consumption, increased cycle time, and costs. Friction stir spot welding (FSSW) is one of the best alternative welding techniques to join dissimilar aluminum alloys with the help of frictional heat and plastic deformation. However, the drawback of this process is the keyhole left behind by the tool. Hence this study focusses on avoiding the keyhole post welding process by the use of pinless tools to join thin sheets of Al 6061 and Al 5754. The influence of process parameters such as tool rotational speed, plunging speed, dwell time, plunge depth, and shoulder diameter was studied on the Tensile shear force of the joint. The optimal welding condition was predicted with the help of the Genetic algorithm. The confirmation tests showed that the predicted optimal conditions were in closer agreement to the experimental value.

The Application of Neutron Diffraction Techniques (NDT) in Measuring Residual Strain-Stresses of Engineering Materials

In order to quantitatively understand the residual strain distributions and benefits of engineering components following special technique treatment, such as Autofrettaging, Hot Isostatic Pressing (HIP) and Dissimilar Material Welding (DMW), the Neutron Diffraction Technique (NDT) has been employed recently to measure residual strain and stress distributions on following three cases of (a) Autofrettaged Aluminum 7075 high pressure vessels; (b) Hot Isostatic Pressed (HIPPED) heavy metals of tungsten clad in tantalum plate and (c) Dissimilar Material Welding (DMW) of 316L austenitic stainless steel and ferritic steel AS508 with Alloy 52 weld filler. This paper reports the recent research findings, including (a) NDT can identify optimal Autofrettage pressure level, by which load bearing capacity of the Autofrettaged pressure vessel increased by 215MPa; (b) NDT is able to reveal residual strains within heavy metals of Tungsten clad in Tantalum plate HIPPED and (c) NDT revealed a maximum residual tensile hoop stress value of about 494MPa in the interface between parent material SA508 and the weld seam. This is vital information for the post weld process and subsequent safe use of the dissimilar materials weld. Other researchers’ successful examples of working with NDT are also briefly reviewed. Future prospective of Engineering Materials Diffractometer (EMD) at CSNS is described too with a view to demonstrating the application and importance of NDT in revealing residual strain-stresses that are inevitable within engineering materials and engineering components following any manufacturing process.

Laser welding of ASTM Corten A588 grade steel - a case study

Corten A588 grade structural steel is a high strength low carbon alloy with high atmospheric corrosion resistance. A significant defect in Corten A588 grade steel is its mechanical, metallurgical and corrosion properties gets altered and gets affected after post welding process. This is due to the Corten A588 grade steel during welding process gets exposed to high temperature in and around the weld zone making it less reliable after the fabrication. Laser beam welding (LBW) is an autogenous welding method in which the heat affected zone and weld zone formed is considered to be very narrow. In this research Carbon dioxide laser beam welding (CO2 - LBW) is performed on a 2 mm thick Corten A588 grade steel under optimal welding condition. Then the mechanical property such as tensile, impact, bending and hardness of the LBW Corten A588 grade steel weld joints are evaluated as per ASTM standards. This research gives detailed information about laser beam welding (CO2 - LBW) of Corten A588 grade steel, various issues faced by the material and helps in widening the applications of this material in various other sectors.

The Effect of Cooling Media on Tensile Strength of Medium Carbon Steel in Post Welding Process Using Electric Welding (SMAW) with E7018 Electrodes

The use of cooling media in post welding process will affect the tensile strength of a material. This study aims to determine how much the influence of using cooling media in post welding and which cooling media is appropriate to use. The process is done by comparing the tensile strength of each cooling media, namely the cooling media of water, air, and coolant. The use of cooling media is carried out after the welding process, until the material that is ready to be welded reaches room temperature. Based on the experiments that have been conducted, the use of post-welding cooling media affects the tensile strength of medium carbon steel with the highest effect on the water cooling media, then the coolant media, and the lowest is the air cooling media. Therefore, the choice of the use of cooling media significantly affects the tensile strength of medium carbon steel in the post-welding process.

Effect of Heat Treatment and Drawing on High-Manganese Steel Pipe Welded by Gas Tungsten Arc

This study investigated the effect of post-weld processes including annealing and drawing on the microstructure and mechanical properties of high-Mn steel pipes welded by gas tungsten arc welding. The weld metal showed a solidified microstructure having coarse and elongated grains due to coalescence of columnar dendrite into welding heat direction. After post-annealing, the solidified microstructure changed into equiaxed grains due to recrystallization and grain growth. Mn segregation occurred during welding solidification and caused lower stacking fault energy (SFE) in the Mn-depleted region. Although ε-martensite formation in the as-welded state and during deformation was expected due to decreased SFE of the Mn-depleted zone, all regions showed a fully austenitic phase. The annealing process decreased strength due to grain coarsening but increased ductility. The drawing process increased strength of weld metal through work hardening. All pipes showed decreasing strain rate sensitivity (SRS) with deformation and negative SRS after certain strain levels. It was confirmed that negative SRS is related to less formation of mechanical twinning at a higher strain rate. This work provides fundamental insights into manufacturing a high-Mn steel pipe and manipulating its properties with annealing and drawing processes.

Influence of Post-Weld Processing Techniques on Laser Beam-Welded Al–3Mg–0.25Sc Alloy Sheets

Fusion welding in aluminium alloys had always remained an issue for aero- and auto industries. An Al–3Mg–0.25Sc alloy is classified as weldable aluminium alloys. In this study, two welding techniques, keyhole and conduction welding, have been used for joining Al–3Mg–0.25Sc sheets of thickness 1.6 mm. Experiments were carried out using different beam diameter (0.16–2 mm dia), beam power (2–4.5 kW) and laser head speed (ranging from 0.5 to 6 m/min). The results for all autogenous keyhole welding clearly demonstrated a drop in ductility ( 50% of base metal). Residual stress-induced distortions affected the final shape of the product, and for that, a suitable stress relief annealing was also required. Hereby, we chose two heat treatment schedules: (1) solution treatment and annealing and (2) retrogression and re-ageing. Retrogression and re-ageing is a precipitation-controlled phenomenon and comprises of an intermediate annealing step between tempering and solutionizing temperature to dissolve the nano-clusters present in the matrix (retrogression) and re-precipitating and growing them by ageing (re-ageing). These two steps were repeated cyclically, and as a result, the strength (190 MPa) and ductility (~ 9%) of the material were improved substantially. The improvement of ductility and strength was explained in detail in the light of microstructural studies.

Formability studies on plasma arc welded duplex stainless steel 2205 sheet

AbstractSheet metal forming is cost‐effective manufacturing process and hold a significant key position in fabrication works. Welding being a popular technique the industries primarily prefer for joining of sheet metal formed parts. The inherent material properties changes at the weld metal and heat affected zone post welding process, hence the impact and changes on mechanical strength aspects need to be studied. The current study focuses on influence of plasma arc welding on formability of 1.6 mm thick duplex stainless steel 2205 sheet using Erichsen cupping test by gauging the height of the cup formed. The performed tests such as uniaxial tensile, microhardness showed better mechanical properties and decrease in formability noted from Erichsen cupping test for weld metal compared to base metal. Finite element analysis of Erichsen cupping test is conducted using ABAQUS software and results are matched with experimental outcomes for validation. The comparison shows that a deviation of less than 5 % is noticed between actual and predicted formability index values. Microstructure examination reveals that, equiaxed grains at the weld center and columnar grains at sides typically formed in the weld metal region. The decrease in formability of weld blank compared to base blank is attributed to an increase in ferrite content. This is supported by amount of ferrite content measured in weld metal is 55 % and base metal is 52 %. The scanning electron micrographs (base and weld blank) reveal the mode of failure is ductile.

Experimental Investigations On Friction Stir Spot Welding Process Of Dissimilar Metals

Friction stir spot welding (FSSW) is derived from friction stir welding process, which is an unconventional joining process. This process exhibits great capability to continue substitute of distinct tip joining process similar to riveting and impeding post welding process. The joining of dissimilar AA2524 –T3 and AA7051-T7451 aluminum plates of 3 mm thickness was carried out using friction stir spot welding (FSSW) technique. Current study considers the tool geometry; rotational speed and joining force as main performance parameters. Three types of tools with various designs have been utilized to analyze the process. An impact of process parameters on mechanical strength and micro structural analysis of lap joints were investigated. The most significant parameter such as tool shoulder diameter to pin diameter ratio shows the greatest influences the joint shear resistance followed by tool rotational speed. The results show that the temperature obtained during processing performs a weighty role in finding the microstructure and features of the processed plates. Failure modes are observed under different load conditions. The welded surfaces were analyzed by scanning electron micrographs.

Investigation on Process and Welded Joint Mechanical Properties of Bainitic Steel Rail Flash Butt Welding

Combine with the characteristics of bainitic rail U20Mn2SiCrNiMo, the flash butt welding process that suitable bainitic rail is optimized for improving bainitic joints’ performance basing on the mature technology of pearlitic rail flash butt welding, through approaches of lower heat input appropriate and matched upset forging length parameters, et.. In the post welding treatment, controlling the heating process strictly and using slow cooling measures are done to further optimize the properties of the welded joints. Then the performance tests are done on the bainitic rail joints welded with optimized welding and post welding process. The study results approve that the qualified bainitic rail joints can be obtained through appropriate flash butt welding process. Tensile strength and impact energy of bainitic joints are superior to pearlitic rail joints, but the elongation is reverse. The impact fracture of bainitic rail flash welded joints appear more defects such as hot cracks and silicate inclusions than pearlitic joints. Compared with parent metal, both types of the rail joints appear higher strength, but lower elongation and impact energy. The decreased percentage of bainitic rail joints compared with their parents is larger than pearlitic joints.

Effect of weld on the mechanical properties of high strength and ultra-high strength steel tubes in fabricated hybrid sections

The effect of welding on the mechanical properties of high and ultra-high strength tubes in hybrid sections is a critical factor which influences the global performance of fabricated members and should be considered in the design and incorporation of these materials. To investigate and quantify these effects on the material of welded steel, a specific type of hybrid section composed of plates and tubes is considered in which two scales of experimental analysis are conducted at different positions from weld. In the macro scale, standard tensile tests are performed at various distances from weld to obtain the mechanical properties of heat affected steel in the axial direction parallel to the weld. Comparisons are made among three different welded materials: mild steel, high strength steel and ultra-high strength steel. The original and after-weld alteration in the ultimate tensile strength (UTS) and the strain corresponding to the UTS are investigated giving particular attention to the effect of yield strength and strain hardening rate. At the micro level, the microstructure of three above-mentioned materials in addition to microhardness profiles have been examined providing extensive data of the material behavior after welding. It is shown that the welding and post welding process, such as heat input and cooling rate affect the local material properties at different distances from weld leading to an overall heterogeneity in the material influencing the mechanical behavior.

Analisis Kesalahan Esensial Hasil Pengelasan Peserta Lomba Kompetensi Siswa SMK Tingkat Daerah Istimewa Yogyakarta

The purpose of this study is to examine various defects in the welding joint works from the participants of Vocational High School students’ skills competition in Yogyakarta area for welding field. This study can be categorized as a qualitative descriptive study. The data collection method was using documentation. The data was analyzed using descriptive qualitative technique. The results showed that in the preparation, the students were lack of understanding and knowledge in determining the welding requirements, the welding current, the type of electrodes SMAW. In the welding process, some participants did not fulfil the welding procedure during the welding process such as mistakes in setting up the SMAW machine, setting the welding current properly, selecting an electrode based on the type and thickness of the workpiece, and mistakes in the process of fit up. In the post-welding process, there were a few mistakes such as the grinding process to clean weld spatter that damaged the ridge.

Evolution of microstructure, porosity and mechanical properties of AZ80 Mg joints during two post-weld processing routes

The evolution of microstructure, porosity and mechanical properties of AZ80 joints during two post-weld processing routes were investigated for comparison. During the partial rolling process, the welding area was effectively strengthened and the porosity was largely reduced with increasing rolling reduction. The Mg17Al12 phases in the fusion zone and heat affected zone were essential on the microstructure evolution during the hot deformation process and subsequent aging process. By proper processing sequence, the strengthening effect of Mg17Al12 phases can be brought into full play, and abnormal grain growth in the heat affected zone can be reduced. The importance of post-weld processing sequence for AZ80 Mg alloy joints was emphasized.