Journal of Welding Science

FeCo-V alloys are one of the most important groups of magnetic material which currently used in high speed engines due to their excellent magnetic and mechanical properties. Welding of these alloys is a great challenge since various phase transformation result in significant changes in magnetic and mechanical properties. In this research ultra-thin FeCo-V magnetic foils were welded using laser and electron beam welding processes. After development of mathematical models, working limits of process parameters were chosen to obtain welded joints which have simultaneously appropriate maximum energy product and mechanical strength.

In this investigation, the effect of heat input of SMAW process on the corrosion behavior of Hadfield steel weld joints was investigated. For this purpose, 4 annealed sheets with thickness 25 mm prepared from Hadfield steel and then welding applied by SMAW process with 6.75 and 11.25 kJ/mm heat input values. For corrosion behavior evaluation of base metal and weld metal areas, potentiodynamic polarization and electrochemical impedance spectroscopy methods were used in the 3.5% NaCl solution. The result of corrosion tests indicated that by increasing the heat input in the SMAW process, the corrosion resistance in the weld metal were reduced. It was also found that in both heat input values, base metal had more corrosion resistance compared to weld metal.

Today, steel to aluminum joints are used to facilitate transportation and fuel consumption. These joints are applied from nuclear, aerospace and naval to automobile and kitchen industries. According to previous studies fusion welding processes are not suitable methods for these joints, solid-state welding, especially friction stir welding, is a proper way to use for these joints. However, using this method for these two metals needs adequate prediction of temperature distribution and material flow to obtain enhanced joints. In this study, a finite element method is used to predict the temperature distribution. In addition, a computational fluid dynamics solution is coupled with the thermal solution. Therefore, the flow rate, strain rate and dynamic viscosity is obtained. Also, the joint morphology is predicted using the Level Set method. It is shown the material flow depends on flow rate, strain rate and dynamic viscosity and is intensively function of rotational speed. Additionally, offset to the aluminum side improves the morphology of the stir zone.

Weldability of high carbon steels due to the high percentage of carbon and consequently formation of martensitic structure is very poor. In this research, resistance spot welding of eutectoid high carbon steel 1075 is experimentally and numerically investigated from various points of view. The effect of welding current as one of the most effective parameters on failure mode, mechanical properties and nugget size diameter in resistance spot welding is analyzed with experimental tests and numerical simulations. The results show that with increase of welding current, the diameter of nugget size is increased and consequently the failure mode changes from interfacial mode to pull out mode.

In this study the microstructure and mechanical properties of super duplex stainless steel UNS S32750 welding was studied. For this purpose, the method of gas tungsten arc and filler metal AWS ER2594 with a diameter of 4.2 mm was used. In order to investigate the microstructure light microscopy and electron microscopy equipped with backscatter electron diffraction were used. Mechanical properties were studied by hardness and tensile tests. Weld metal had  Cast structure with austenite in the dendrite form  located in ferrite matrix. It was also observed in the melting zone after welding, the ferrite volume fraction decreased to 50 percent 60% base metal ferrite) ,Due to the low cooling rates and  high heat input method in the gas tungsten arc welding. Vickers micro-hardness test method was carried out on the samples showed that average about 285 Vickers hardness of base metal; however, hardness in the fusion region due to increased austenite fraction fell to 250 Vickers. But hardness in the heat-affected zone due to lower volume fraction of austenite and ferrite phase formation of chromium carbide intermetalic compounds increased to 340 Vickers. The results of the tensile test showed that the tensile strength decreased with increasing heat input, because of increase the size of grains due to the increased heat input.

Cellulose is a natural biopolymer with the general (C6H10O5)n formula, which according to AWS A5.5 standard, more than 40wt% of coating of cellulosic electrodes is consisted of cellulose. In this study to evaluate the effect of cellulose type on the performance of E8010-P1 cellulosic electrode, equal  amounts  of two celluloses with the same commercial properties but produced by two different companies, were used for production of two E8010-P1 electrodes.Experimental studies illustrate significant difference between structural and mechanical properties of deposited weld metals from these electrodes. FTIR, DTA and XRD testes of as-received celluloses show despite the same brandforthese celluloses, their properties such as bonds types,thermal behavior and crystallinity are different that cause variation ofweld metal penetrate and tensile strength around 25±2% and 5±2%respectively.

Fusion welding is widely used in heavy industries to join different parts together. But sometimes welding-induced distortions cause problems like misalignment during assembling and make costs to remove them. Thus it is imperative to predict and mitigate them to improve weldments quality and also reduce in fabrication costs. This study at first will introduce inherent deformation method for prediction of welding-induced distortion. In following a relatively large panel will be simulated by finite element software ANSYS and its distortion will be calculated. The results will be compared by experimental measurement. Afterward this investigation will present an efficient welding sequence which produce minimal distortion.

This Paper presents the welding parameter's effect (forging pressure, welding time) on macrostructure and mechanical properties of friction welding valve steel HNV3 to Nimonic 80A super alloy. For this purpose, two rods with 20 mm diameters are prepared and with using different parameters (Increase forging pressure and welding time) by friction welding method are welded together. Tensile Test carried out on samples for investigating the effect of a parameter. It was discovered that when the welding parameters used in connecting HNV3 and Nimonic 80A Superalloy couple through friction welding were selected correctly; strength of the connection would increase compared to the main material.

The aim of this study was to evaluate the mechanical properties and corrosion behavior of friction stir welding (FSW) connection of A517 (B) steel plate. Mechanical properties and corrosion behavior of weld zone were evaluated after reaching to optimum FSW microstructure with the lowest martensite phase. Thus, after the identifying phase microstructure by SEM and XRD analysis, mechanical properties were analyzed by micro-hardness and tensile test. Micro hardness data shows slight increases in stir zone (SZ) compared with the base metal (BM); although a reduction of about 17% in hardness of heat-affected zone (HAZ) was sensible. Reduction of hardness in the HAZ was appeared as drop by about 12 percent of the yield strength and 19 percent of ultimate strength compared with BM. SEM images from fracture surface of the tensile sample showed bi-modal distribution of large and small Dimples being sings of softness of HAZ .Comparing corrosion behavior in solution consist of 3.5 wt% of NaCl showed that there was no passive layers to prevent dissolution of the metal in the SZ and BM. while BM and SZ had fairly similar corrosion rates, Difference of 50 mV between corrosion potential of SZ and BM showed that in galvanic condition, corrosion resistance of BM could be lower than SZ.

In this study, commercially pure titanium and aluminum alloy 5083 in connection rotational speed of 1120 rpm and a feed rate of 50 mm per minute for butt welding by friction stir welding has been successfully completed. Micro-structure, hardness and tensile test was conducted on the connection. Welding area is a composite of aluminum and titanium particles that the particles plays an important role in increasing hardness and tensile strength. Welding area is also has three areas. Vickers hardness is 480 times the area of welding means that the hardness in the area of the base metal of titanium and aluminum increased by 16% and 60% for titanium aluminum intermetallic compounds is created in the area is weld.

In this research, lap joint frictionstir welding of IF sheets with thickness of 0.7 mm is investigated. For this purpose, mechanical properties of joints and also microstructural evolutions are studied. It was found that increase in tool rotational speed and decrease in travel speed results in increase in fracture stress of welded joints. Texture study indicates that no changes can be observed in texture components after friction stir welding. This phenomenon in texture components can be related to high stacking fault energy of IF steel and consequently severe dynamic recrystallization during welding. The results show with increase in the tool rotational speed between 900-1400 Rev/min, ultimate force of fracture of friction stir welded joints is increased. Also, it is concluded from results that with increase in tool travel speed between 50-160 mm/min, ultimate force of fracture of welded joints is decreased. Finally it is proved from results of this paper that in the frictionstir welding of IF sheets with thickness of 0.7 mm, maximum force of fracture of welded joints is achieved in rotational speed of 1400 Rev/min and travel speed of 105 mm/min.   

Recent research suggests that extraordinary combinations of strength and ductility can be achieved in the so-called TRIP steels. With the development of these steels, welding with small weld nugget size and acceptable strength are needed. For these reasons present study was carried out to investigate the effect of heat input onweld size, microstructure and the hardness of the welded metal of 0.4%C- 4%Al δ-TRIP steel after continues fiber-laser welding process. To achieve this goal a bead on plate welding with three different values of heat input 28, 60 and 80 J/mm were used.The results of welding process revealed that by increasing the heat input, cooling rate decreased and the volume percent of the δ-ferrite in weld metal increased due to the availability of sufficient time for partitioning of Al in high heat input which leads to the stable δ-ferrite and as a result the difference between the hardness of the weld metal in comparison to the base metal decreased.

In this study, microstructural features and mechanical properties of Incoloy 825-316L stainless steel dissimilar joints have been investigated. For this purpose, pulsed gas tungsten arc welding method was employed and 316L, Inconel 82 and Inconel 625 alloys were used as filler metal. First, specimens were cut. Pulsed gas tungsten arc welding was performed using peak and base currents of 220 A and 110 A, respectively. Microstructure of welded joints was studied using metallographic observations and energy dispersive spectroscopy (EDS) analysis. In order to evaluate the mechanical properties, tensile and microhardness measurements were done on the joints. In all specimens, dendritic and equiaxed and/or cellular growth of austenite phase was observed. Incoloy 625 weld metal had the finest dendritic structure. Tensile test results revealed the ductile fracture with a high percent of elongation for all specimens. The highest tensile strength and percent of elongation of 610 MPa and 48% were obtained for specimen welded using Inconel 625 filler metal. Inconel 625 and 316 stainless steel weld metals showed the highest and lowest microhardness with values of 232 HV and 224 HV, respectively.  

In this investigation, the effect of heat input of SMAW process on the microstructure and mechanical properties of Hadfield steel weld joints was investigated. For this purpose, 4 annealed sheets with thickness
2 mm prepared from Hadfield steel and then welding applied by SMAW process with 6.75 and 11.25 kJ/mm heat input values. The evaluation of the microstructures of welding joints was conducted by optical microscopy and the joints mechanical properties were examined by tensile, charpy impact and microhardness measuring tests. The results indicated that by increasing the heat input in the SMAW process, microstructure consisted from smaller grains, and strength and microhardness increased but impact energy was reduced.  

High-strength low alloy steels are a class of steels used in applications that require high strength and good weldability, including ship hulls, gas pipelines and oil industry. One way to build parts is fusion welding that create areas with a large grain size in the heat-affected zone and increased susceptibility to hydrogen cracking. One way to solve this problem is to use solid state friction stir welding process. In this study, microstructural evaluation and mechanical properties of friction stir welding X-60 cross sections examined by optical microscope and by tensile and micro-hardness tests. The results indicate that changing welding parameters and thereby, change the heat input during friction stir welding have a great impact on maximum temperature and cooling rate that cause creating ferrite and bainitic ferrite in the weld zone. This change in microstructure of weld zone cause to improve mechanical properties that increase yield strength from 380 MPa to 420 MPa .Also, the friction stir process cause increasing hardness of 220 Vickers to an average of 280 Vickers and uniform distribution of hardness in the cross-section of friction stir joints.

The aim of this study is to reach an increased service life for parts using in sour environment by weld overlaying process. In this investigation, two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps, Post Weld Heat Treatment (PWHT) was conducted. Microstructural analysis, X-ray diffraction studies, and mechanical tests show significant increase for austenite volume fraction after second stage of PWHT. In fact, not only two-stage PWHT  reduce the samples hardness, but it also increases austenite volume fraction which is a more resistant microstructure against hydrogen cracking.

Studies on welding process of Aluminium weldments shows that post-weld residual stress and deformation are influential on structure efficiency and there are different variable which affect these stresses and deformation. In this study the effect of geometrical variables and welding sequence on residual stresses and deformation in Aluminium H321 have investigated by the finite element software Ansys. Thermo elastic-plastic model was verified by metallography experiment and measurement of post-weld deformation afterward, weld leg, penetration depth and welding sequence were optimized to minimize the distortion. It was concluded that weld-volume increase post-weld distortion and it can be minimize by choosing an appropriate weld sequence

The fine grain structure of friction-stir welded aluminum alloys is unstable during post weld heat treatment and some grains abnormally grown. In this study, the sequence of abnormal grain growth during T6 heat treatment of Al-7075 friction-stir weld and its effect on mechanical properties of the weld was studied. The results showed that heat treatment in 510 ˚C resulted in drastic grain growth in stir zone and fine equiaxed grains in the stir zone of as-welded joint were substituted by millimeter-scale irregular grains. Post weld heat treatment resulted in decrease in the tensile elongation from about 10% to 1.5% although the joint tensile strength improved by 28%. In addition, post weld heat treatment changed the fracture location from the 
heat-affected zone to the stir zone.

Nowadays, cemented carbides-steels joints by brazing method are taken into consideration. One of the problems of these joints is the creation residual stresses that can reduce it with choose correct parameters of brazing. In this study, Silver base alloy filler containing copper, zinc and cadmium have been used in temperature 780°C and the effect of time parameter 5, 10 and 15 minutes on microstructure and mechanical properties were investigated. The results indicated that brazing in 15 minutes causes a columnar growth of solid solution phase of copper from cemented carbide side to steel and provides maximum strength of 94MPa. As well as, by passing of time wetting angle of cemented carbide surface reduces from 40° to about 27°.

This paper investigates the effect of boehmite nano-particles surface adsorbed byboric acid (BNBA) along with other input welding parameters such as welding current, arc voltage, welding speed, nozzle-to-plate distance on weld penetration. Weld penetration modeling was carried out using multi-layer perceptron artificial neural network (MPANN) technique. For the sake of training the network, 70% of the obtained data from experimentation using five-level five-factor central composite rotatable design of experiments was used. The performance of the network shows a good agreement between the experimental data and the data obtained from the network. Hence, it is to be concluded that MPANN is highly accurate in predicting the weld penetration in SAW process.