Showing 125 results for Welding
Dr. Mohammad Yousefieh,
Volume 7, Issue 1 (8-2021)
Abstract
In this paper, using the Taguchi method, the parameters affecting the toughness of super duplex stainless steels in friction stir welding were optimized. In order to achieve optimal conditions, maximum toughness, the quality characteristic was used as the higher the better. Analysis of Taguchi results showed that in order to achieve optimal conditions in super duplex stainless steel weldments must have a tool rotational speed of 500 rpm, a welding speed of 60 mm / min, an initial pressure of 70 MPa and a tool tilt angle with the workpiece is equal to 3 degrees. Under optimal conditions, the toughness obtained from the confirmation test was 61 J, which was very close to the predicted toughness (58 J). Analysis of variance was also performed on the results of signal to noise (S/N) ratio. According to the results of analysis of variance, the tool rotational speed parameter with an influence percentage of 64% was the most effective parameter on toughness in friction stir welding of super duplex stainless steels. On the other hand, the parameters of welding speed (with an influence percentage of 17 %), initial 2 pressure (with an influence percentage of 16%) and tool tilt angle to the workpiece (with an influence percentage of 3%) were in the next ranks. Also, SEM micrographs from fracture surface of the samples in the impact test proved that the sample that had the least toughness in the impact test had a cleavage morphology and as a result, brittle fracture. This was while the morphology of the fracture surface of the tested sample under optimal conditions (with the highest toughness in this study = 61 J) had a large amount of fine and deep dimples. The presence of these dimples in large quantities indicated ductile fracture and eventually reaching the highest toughness.
H. Sabet, R. Tahavori, A. Alimoradi,
Volume 7, Issue 2 (1-2022)
Abstract
Effect of Interlayer Composition on the Microstructure and Mechanical Properties of 1050 Aluminium to St14 Carbon Steel Joint Via Resistance Spot Welding Method.
Hosseinn Soleimani, Kamran Amini, Farhad Gharavi,
Volume 7, Issue 2 (1-2022)
Abstract
In this research, butt joining of Al2024 and Al7075 plates were performed by Friction Stir Welding (FSW) and the effect of tool position on microstructural and mechanical properties in about 1 mm from center line of joint towards the advancing side (AS) and the retreating side (RS) was investigated at three positions of +1, 0, -1 mm. In this regard, the plates of Al2024 and Al7075 were selected as the AS and the RS, respectively. In this joining method, transvers speed of 200 mm/min and tool rotation speed of 600 rpm were chosen. Macro- and Micro- structures of various welding areas and fractography of samples were evaluated by optical and scanning electron microscopies. In addition, mechanical properties were investigated using micro-hardness and tension tests. From the obtained macro-structures, it was observed that in all three joints, the surface of weld was without any defects (i.e., porosity, lack of penetration…). With varying tool offset position, welding micro-structure morphology was changed from homogeneous mode to layer or onion ring- shaped mode. Moreover, with varying tool position into the AS-side, tensile strength increased about 17.5% as opposed to the zero-tool position, but there was a decreasing about in tensile strength with changing tool position towards the RS-side as compared with the zero-tool position. Value of micro-hardness was approximately similar in all welded samples, but the highest value of hardness was observed at the weld zone (WZ). Thus, the obtained results showed that with varying tool position into the AS-side, mechanical properties were improved as opposed to the zero-tool position and tool position towards the RS-side.
Homan Nikbakht1, Mohammadreza Khanzadeh, Hamid Bakhtiari,
Volume 7, Issue 2 (1-2022)
Abstract
In the present study, the corrosion behavior and microstructural changes of 5000 series aluminum and copper sheets after the explosive welding process have been investigated. Explosive welding is performed with a fixed stop interval and change of explosive load. Dynamic potential polarization tests and electrochemical impedance spectroscopy, light microscopy, and scanning electron microscopy were used. The results of TOEFL polarization curves show that the lowest corrosion velocity was related to the sample with an explosive load of 1.5 and the highest corrosion velocity was related to the sample with an explosive load of 2.5. The corrosion resistance of a sample with an explosive load of 2.5 is less than that of a sample with an explosive load of 1.5 due to more severe plastic deformation at the joint. The metallographic results show a wave-vortexing of the joint due to the increase in the explosive charge. The results of the impedance test in welded samples showed that the value of n (experimental power parameter) decreased with wave-vortexing of the joint and the sample with 2.5 explosive load had the highest corrosion rate. Based on the results of scanning electron microscopy, it was observed that with an increasing explosive charge, the thickness of the local melting layer gradually increases.
Mr. N. Taheri Moghaddam, Dr. A. Rabiezadeh, Dr. A. Khosravifard, Dr. L. Ghalandari,
Volume 7, Issue 2 (1-2022)
Abstract
Conventional fusion welding of aluminum alloys results in coarse-grained structure, inevitable defects, and significant softening in the welding region. Friction stir welding with bobbin tool is a technique of friction stir welding method that has a great potential for developing applications of friction stir welding method in marine, aerospace, and automotive industries due to having an extra shoulder. Sheets of 5083 aluminum alloy with a thickness of 3 mm were welded using the bobbin tool friction stir welding method to assess the feasibility of similar joining. The effect of different process variables such as shoulder pinching gap, transverse speed and tool rotation speed was investigated. The results showed that a sound joint is achieved at a transverse speed of 13 mm / min and a tool rotation speed of 1350 rpm. The results of tensile test showed that the obtained joint efficiency is 94.5%, which is higher than the joint efficiency of fusion methods and comparable to the joint efficiency of conventional friction stir welding. Microscopic evaluation of the fracture surface of welded specimens showed that for similar joints, the dominant fracture mechanism is ductile fracture.
Dr Seyed Mahdi Rafiaei, Eng. Gholamhosein Eslami,
Volume 7, Issue 2 (1-2022)
Abstract
In this research, Ti-6Al-4V alloy sheet with a thickness of one millimeter with butt joint design was welded by tungsten-gas arc welding process using pulse current (PCGTAW) and using AMS 4954G filler metal. In this study, the effect of pulse system frequency on microstructure and mechanical properties was investigated by optical microscopy, Vickers hardness and tensile strength tests. In the non-frequency welding sample, due to the lack of pulse current and lower cooling rate of the molten pool, the formation of large amounts of soft phases of the Weidmann-Statten layer in the weld metal region is possible. Finally, in this method, the lowest average hardness of 341 Vickers was obtained. The experimental results showed that using pulsed current and increasing the pulse frequency up to 450 Hz increased the cooling rate of the molten pool, followed by increasing the amount of martensitic phase α 'in the form of a basket in the weld metal region and finally increasing the average microhardness in this region. In other words, using the maximum frequency led to a significant increase in hardness up to 367 Vickers in the weld zone. Finally, using the tensile strength test, it was shown that in all the samples, failure occurred from the base metal area, which was a very good phenomenon due to the proper welding quality of the samples.
Majid Aslani, Mahdi Rafiei,
Volume 7, Issue 2 (1-2022)
Abstract
In this study, in order to modify the weld structure obtained from repair welding of AZ91C magnesium alloy and improvement of tensile strength, input parameters such as current intensity and preheating temperature were optimized for this alloy. T6 heat treatment was separately done befor and after the welding to homogenize the microstructure and improvement of the mentioned properties. Using variance analysis, the accuracy of the models was checked and analyzed. Optical microscopy, scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS) and tensile tests were used to characterize the microstructure and mechanical properties of the repaired parts. The results of microstructural studies showed that the samples 2 (samples that were subjected to T6 heat treatment before and after welding) had continuous precipitates which these precipitates affected the strength due to the interruption of more slip planes and creating stronger barriers in the path of dislocations, resulting the better mechanical properties as compared with samples 1 (samples that were subjected to heat treatment only after welding). Also, by plotting response surface graphs and level diagrams, the highest tensile strength for samples 1 was observed at preheating temperatures of 493 to 513 K and current intensities of 80 to 90 A, and for samples 2 at temperatures of 513 to 553 K and current intensities of 100 to 110 A.
Dr. Seyedeh Zahra Anvari, Eng. Meysam Khandozi,
Volume 7, Issue 2 (1-2022)
Abstract
In the present study, to resolve the problems in fusion welding methods as well as to increase the strength, FSW method was used to join aluminum alloy sheets 6061 and 2024. Moreover, optimal parameters for joining of these two alloys were also taken into consideration. Various tool rotation speeds of 565, 950 and 1500 rpm were selected. For each tool rotation speed, two traverse speed variables, two penetration depth variables, and two tool angle variables were specified. The analysis of mechanical properties of welded samples was conducted through tensile and micro-hardness tests. Furthermore, microstructure of welding zone was investigated using optical and electron microscopes. The ratio of shoulder diameter to pin diameter is among the most significant and practical factors for welding tools. So, a shoulder diameter three times larger than that of pin diameter was selected. In the present study, alloy 2024 was placed at the precursor as the harder alloy. Tensile strength and indentation hardness of optimal specimen 300 MPa and 85 HV were achieved. Moreover, hardness behavior and tensile strength of heat-affected zone (HAZ) was evaluated to be lower in alloy 6061 compared to other zones.
Behrooz Beidokhti, Amin Ghorbani,
Volume 7, Issue 2 (1-2022)
Abstract
The present study investigated the effect of electrode composition and buffer layer on the microstructure and mechanical properties of H13 tool steel repair welds. Three specimens were welded applying two conditions; i.e. with and without stainless steel underlay. The microstructure of all weld metals contained the martensitic matrix with distributed chromium carbide precipitations. The microstructure of the underlay was a mixture of austenite and layers of ferrite with the skeletal morphology. The results showed that hardness of the welded substrates with underlay was higher than that of the specimens without underlay. This difference could be more than 240 HV. However, the highest hardness values were obtained in the heat affected zone of welds. The application of tough underlay improved the weld toughness and bending properties of the welded specimens. Also, it encouraged the ductile fracture mode in weldments. Also, the higher hardness of weld metal could be resulted from the application of buffer layer.
Dr Homam Naffakh-Moosavy, Eng. Ali Rasouli,
Volume 7, Issue 2 (1-2022)
Abstract
In this research similar joining of NiTi shape memory alloy was studied. For this purpose, NiTi alloy in the form of wires with circular cross section possessing martensitic phase structure at room temperature was used. By utilizing Nd:YAG pulsed laser welding method followed by optimizing its technical parameters, a defectless joint in terms of appearance and metallurgical properties was obtained. In the next step, the effect of various pulsed laser duration time on properties of the obtained similar joint of NiTi was investigated. Moreover, the resultant microstructures were studied using optical microscope (OP) and Scanning Electron Microscope (SEM) equipped with chemical analysis of EDS. Furthermore, the samples prepared under different pulsed laser duration time conditions were characterized by using tensile and micro-hardness tests. Investigating the results of the performed evaluations revealed that higher levels of heat input has resulted in grain growth, dissolution of precipitations as well as reduction in hardness and ultimate tensile strength of the samples in the joint zone.
M. Karbasian, N. Adabavazeh, M. Nikbakht,
Volume 7, Issue 2 (1-2022)
Abstract
One of the most dangerous industries is welding and inspection. Risk assessment is a rational procedure for determining the probable repercussions of prospective incidents on people, materials, equipment, and the environment. The risk assessment identifies the efficacy of selected control mechanisms and offers essential data for risk reduction, risk management, control system enhancement, and risk response planning. The current study identified 13 dangerous parts of the "hot crack" and "cold crack." The discovered dangers were then ranked by expert academics in the welding and inspection industries using the best worst fuzzy method. A fuzzy method has been developed to address risk uncertainty and minimize decision inconsistencies. The findings indicate that the primary risk factors for weld metal hot cracking in order of importance are "frozen structure, separation, high tensile stresses in the weld metal, material composition, bonding, preheating, high flow intensity, high-thickness workpiece, and weld pollen form." And "the quantity of hydrogen in the weld metal, high tensile stresses, a vulnerable structure, and a relatively low temperature" are all factors in cold welding of weld metal. The study's results may be used to guide the selection of solutions, remove the primary dangers, and establish security policies in the welding and inspection industries.
S.e. Moosavi, M. Movahedi, M. Kazeminezhad,
Volume 8, Issue 1 (8-2022)
Abstract
In this study, thermo-mechanical stability of two-pass constrained groove pressing (CGP) AA1050 sheets towards friction stir welding (FSW) employing hybrid powder (%50vol. micrometric graphite powder+%50vol. α-Al2O3 nanoparticles) was investigated by examining its microstructural evolutions and mechanical properties. FSW was carried out via different process variables in order to reach the highest ultimate mechanical properties of joints. The welding variables employed in this study were single-pass and multi-pass FSW, and different rotation speed to traverse speed ratios (ω/v) were. In order to appraise the powder effect on mechanical properties in the fabricated hybrid metal matrix composite (HMMC), some CGPed sheets were also welded with no powder. Besides optical microscopy and field emission scanning electron microscopy (FESEM) observations, Vickers microhardness and transverse tensile tests were conducted to examine mechanical properties of the weld zone. It was revealed that the effect of graphite powder as a solid lubricant was substantially influenced by the welding variables. More precisely, by employing graphite powder during the FSW, the peak temperature decreased to 224 ℃, while the peak temperature of 489 ℃ was resulted by welding without any powder. Thus, the thermo-mechanical stability of CGPed aluminum and their mechanical properties were enhanced. On the other hand, graphite powder can be responsible for mechanical properties drop due to deteriorating material flow. In addition, different strengthening mechanisms, including grain boundary Zener-pinning and particulate stimulated nucleation (PSN) mechanism, were provided and governed by both powders. However, increasing the ω/v ratio was a practical approach to obtain uniform powder distribution, and consequently, to attain ultimate mechanical properties. Moreover, weld soundness was perceived to be achievable by increasing the number of FSW passes due to eliminating the cavities and improved material flow, resulting in an ultimate tensile strength of 101 MPa, as an optimum efficiency of ~ %80, in three-pass FSW at ω/v=70.
M. Vatandoost, E. Mohammadi Zahrani, B. Beidokhti, A. Davoodi,
Volume 8, Issue 1 (8-2022)
Abstract
The welding joints were investigated due to the significance of similar welding of Corten A weathering steel and its dissimilar welding with St12 plain carbon steel in industrial applications. The gas metal arc welding (GMAW) technique with carbon dioxide shielding gas was utilized in the present work. The welding process comprised current and voltage control, welding wire injection rate, shielding gas rate, welding speed, connection configuration, and microstructure evolution. Mechanical properties and microstructure evolution in similar and dissimilar joints and weld defects were evaluated by tensile, bending, hardness, metallographic, and radiographic tests. The weld microstructure in similar and dissimilar joints included grain boundary ferrite, acicular ferrite, and WidmanStatten ferrite. The tensile strengths of the similar and dissimilar joints were respectively 497 and 303 MPa. The weld zone hardness was 210 and 180 Vickers for similar and dissimilar joints, respectively. In conclusion, similar welding outperformed dissimilar welding considering weld joint defects, mechanical properties, and microstructure.
M. Foumani, H. Naffakh-Moosavy, A. Rasouli, H. Aliyari,
Volume 8, Issue 1 (8-2022)
Abstract
Surface roughness in the welding processes is one of the important parameters in the laser welded metal connections which affects laser beam absorption directly. When the laser beam is irradiated to the surface of the base metal, the surface roughness plays an important role in the amount of beam absorption and the amount of melting achieved and directly affects the penetration depth. The main purpose of this study is to investigate the effect of roughness mentioned above in the equal parameter for this widely used aluminum alloy. Microstructural Surveys were performed on three different roughness levels of the sample and the results obtained from the analysis of samples by optical microscope (OM), atomic force microscope (AFM) and Scanning electron microscopy (SEM) analysis showed that, increasing the surface roughness up to Ra = 0.16 micrometer, caused the greater degree of beam engagement by the surface grooves, hence more concentration of the beam photons and more melting obtained, so the depth of penetration increases by consuming a lower amount of energy.
H. Gorji, Dr. S. M. Barakat, S. R. Shoja Razavi, S. S. Babaie Sangetabi, M. Erfanmanesh,
Volume 8, Issue 1 (8-2022)
Abstract
The aim of the present study is to investigate the mechanical and microstructural properties of 1.7225 steel in laser welding process using Nd:YAG pulsed laser device and then to determine the optimal focal length relative to the part in the welding area. After welding, microstructural characterization, microhardness and tensile tests were performed. Evaluations showed that the optimal focal length for welding of steel sheet 1.7225 with a thickness of 1 mm, it was about 9 mm and the focus was 1 mm below the surface of the part. Due to the high thermal concentration and cooling rate in laser welding, a completely martensitic microstructure has been observed in the molten and heat-affected regions of all specimens. In this alloy, the hardness of the base metal is 310±10 HV. After welding, the hardness of the sample with the optimal focal length has reached 625±10 HV in the heat affected zone and 730±10 HV in the melting zone. Also, the results of tensile test showed that the tensile properties of the sample with the optimal focal length were almost similar to the base steel and fracture was observed in the base steel region.
S. Golestanehzadeh, Dr. S.h. Mousavi Anijdan, Dr. H.r. Najafi Dezdeh Monfared,
Volume 8, Issue 1 (8-2022)
Abstract
In this investigation the effect of oxides powders of SiO2, MoO3 and CuO on the depth of penetration, microstructure and hardness profile of GTAWeld precipitation hardening martensitic 17-4PH was assessed. Samples were taken from 17-4PH steel sheet with the dimensions of 150*50 mm and with the thickness of 5 mm, and were welded by oxide powder of SiO2, MoO3 and CuO. Results showed that using oxide powder increased the penetration depth of the welded joints by about 150 percent compared to the normal condition. Also, it was shown that although using SiO2 powder increased the penetration depth to about 7.49 mm, it provides inferior weld bead appearance. The use of MoO3 and CuO powder increased the penetration depth of the weld to about 5.3 mm. Although inclusions were found throughout the side of the weld bead when MoO3 powder was employed for welding. The microstructure of the weld in different samples did not vary and included dendritic structure with delta ferrite located between the dendrites. The hardness profile of the welded joints showed the closeness of the hardness of the welded joints using different oxide powder with the base metal.
S. Varmaziar, M. Atapour, Y. Hedberg,
Volume 8, Issue 1 (8-2022)
Abstract
The influence of filler metals on the microstructure and corrosion behavior of AISI 316L welds was investigated. Gas Tungsten Arc welding (GTAW) process was applied to join the AISI 316L plates using ER 316L and ER 312 filler metals. The obtained microstructures were characterized by optical metallography and scanning electron microscope (SEM). Corrosion assessments were conducted in 3.5% NaCl using a three electrode cell. Open circuit potential and potentiodynamic polarization examinations were conducted on the welds and base metal. Microstructural evaluations indicated that a combination of austenite and ferrite phases was formed in the welds fabricated by both filler metals. Based on the micro hardness tests, the weld fabricated by ER 312 filler exhibited superior harness compared to the ER 316L weld. Corrosion evaluations also show that the weld metal obtained from two filler metals has a lower corrosion rate due to the higher amount of chromium and higher ferrite compared to the base metal. Also, the lower corrosion current of ER 312 weld metal compared to ER 316L weld metal is for this reason. In contrast to the base metal compared to the two welding metals, the result of the two filler metals has shown better pitting corrosion results according to the electrochemical tests and also the examination of the surfaces using an optical microscope after these tests, that these results are due to The presence of two phases of austenite and ferrite in the vicinity of each other in weld metals and the intensification of galvanic corrosion is due to the discharge of the austenite phase from chromium and molybdenum.
N. Taheri Moghaddam, A. Rabiezadeh, A. Khosravifad, L. Ghalandari,
Volume 8, Issue 2 (1-2023)
Abstract
Despite the increased use of aluminium alloys in several industries, their common concern is the difficulty of joining dissimilar alloys using welding techniques. Based on this, the primary purpose of this research is to assess the mechanical characteristics of dissimilar joining of heat-treatable 6061 and non-heat-treatable 5083 aluminium alloys by gas tungsten arc welding and to discover the link between microstructure and mechanical properties. Similar welds were also implemented and evaluated in order to more properly analyze and compare the outcomes. The quality of the weld generated after establishing the health of the joint using non-destructive testing was evaluated by destructive bending, tensile, metallographic, and hardness tests to check the mechanical and microstructural qualities. The intended dissimilar weld was produced under the parameters of pulse current 120-80 amps, voltage 20 volts, welding speed 15 cm/min, and filler 5356. It should be highlighted that the dissimilar weld had the maximum joint efficiency, and with perfect control of welding settings and the absence of flaws, only 36% loss of strength was recorded when compared to the base metal. Metallographic images revealed that the formation of hot cracks in the dendritic structure of the weld metal is the major cause of strength loss for 5083 similar weld and the production of numerous porosities in the weld metal for 6061 similar welds.
Gh. Khalaj, E. Asadian,
Volume 8, Issue 2 (1-2023)
Abstract
In this paper, the microstructure and mechanical properties of the plain carbon steel-bronze interface of explosive welding and rolling were investigated. Explosive connection was done at two stop distances and with two different thicknesses of explosive material. Rolling of the welded composite was done at both ambient and preheated temperatures of 300 °C and with a constant thickness reduction of 33.3%. The results showed that the wave interface of the steel-bronze connection includes different parts. By rolling, the connection interface was stretched and flattened and the vortex areas were compressed together and in some cases entered the steel field. The steel particles separated from the background along the wave crest and remained as isolated islands in the bronze background. On the other hand, in the areas near the vortex, a part of the bronze flying metal was caught under the wave and was observed as islands separated from the bronze background inside the steel. Porous areas were crushed and compressed as a result of rolling. The rolling force and temperature had partially removed the diffusion barriers and a metal bond had been formed between bronze and steel. During the connection, the voids and shrinkage pores were pressed together due to rolling and the separate borders were close to each other. Explosive joining and cold rolling had increased the hardness in the interface, and hot rolling has led to a decrease in the hardness in the interface. In the hardness test, the welding samples are arranged in the order of the highest impact energy. The effects of welding parameters remain after cold and hot rolling and the hardness rating does not change.
S. Kazemi, G. Khalaf, A. Afsari, M.j. Marzban,
Volume 8, Issue 2 (1-2023)
Abstract
Stainless steel cladding is the formation of an alloy by creating a thin layer of stainless steel on another metal. In this research, a layer of SA240-TP316 austenitic stainless steel was coated on SA516-GR60 steel. Experiments were conducted to compare the mechanical properties of SA240-TP316 and claded SA516-GR60 steel welds in order to investigate the possibility of replacing the SA240-TP316 steel alloy. Examining the results of the chemical analysis of SA240-TP316 alloy shows that the coating has a similar chemical composition to SA240 alloy and with increasing depth, the hardness of the weld metal and the percentage of chromium is higher and the percentage of molybdenum in the weld alloy is lower. Comparing the ultimate strength of SA516 alloy after cladding and welding with SA240 stainless base alloy shows the improvement of tensile strength. In the first case, the strength changes in the range of 470 to 503 MPa and in the second case in the range of 477 to 570 MPa. The highest hardness was obtained in the heat affected area. Bending test showed that bending without cracking up to 180 degree angle is a sign of weld metal remaining ductile. The results of the impact test also show the ability to absorb energy, especially around the voltage of 150 volts.
