Journal of Welding Science and Technology of Iran

Fabrication of synchronized hammer peening with pulsed laser welding and its effect on 6061 aluminum alloy weld

H. Farhangi

The non-continuous laser beam in pulsed lasers allows the mechanical peening between two consecutive beams on a still hot weld bead. At a very short time (20, 150 and 300 ms) after laser pulse application, mechanical peening was performed on the welding bead. To achieve these short times, the light sensor detects the nth laser pulse and the mechanical arm starts moving. Upon reaching the tip of the pin near the workpiece, the n + 1th pulse was irradiated to the workpiece surface, and so the pin impact to the weld bead after traveling a short distance. Desirable mechanical properties were obtained at the highest time (300 ms) and highest pressure (6 bars). In this time and pressure the weld beads were not broken due to bending forces of peening.

Welding challenges facing advanced automotive steels in resistance spot welding process: A review

R. Ashiri

Nowadays, the use of advanced high strength steels (AHSSs) in body-in-white is one of the hot applied strategies which is followed by the most of the automakers. The study of weldability and weld challenges facing these steels in resistance spot welding process as the most widely used process in the assembly lines of the automotive industry is essential to use the outstanding mechanical responses of AHSSs. This study can result in improvement of mechanical performance of the resistance spot welds of AHSSs. Our results indicate that AHSSs experiences different welding challenges which this work aims to study them by discussing their causes, mechanisms involved and potential ways to address them.

Effect of rotary friction welding variables on mechanical and physical properties of aluminum-copper tube joints

A. Zolriasatein

The aim of this study is to investigate the effect of rotary frictional welding process variables on microstructure, mechanical and physical properties of copper-aluminum dual-tube pipes. For this purpose, using a thermosetting friction welding machine, a copper pipe (99.44% purity) with a similar diameter aluminum tube (1050), was welded in three different conditions with different friction pressures and forging, and then by metallographic, hardening and microstructural testing it placed. The results of this study showed that with increasing friction pressure from 10 and 15 Bar respectively, in the interconnected phase, fuzzy interclass metal samples were created and caused a great loss in the deformation percentage and tensile strength of the interconnected sample. Also, with the reduction of frictional pressure and the removal of forging pressures down to 5 Bar, there is no proper bond between the two samples and formed in the interface between porosity and cracking. The most suitable result for the microstructure, mechanical and physical properties of the samples is in tubes with an outside diameter of 15 mm and an inner diameter of 10 mm, for samples having a friction pressure of about 10 Bar and a forge pressure of 15 Bar. The presence of intermetallic Al-Cu phases such as CuAl₂, due to higher electrical resistance and ceramic nature, increases the electrical resistance of the joint and, on the other hand, the presence of cracks and pores has reduced the flow rate and eventually increased electrical resistance of the samples

The effect of activated flux type on the weld profile and angular distortion of A-TIG welding of the AISI 2205 duplex stainless steel

H. Sabet

In this investigation, the AISI 2205 duplex stainless steel was welded in the form of bead on plate by A-TIG process with different amount of the ZrO2 and TiO2 activated fluxes. The results of the visual inspection showed that the specimen with 50% ZrO2 and 50% TiO2 activated flux, had the lowest face width and the specimen with contains 90% ZrO2 activated flux, had the highest penetration depth. Also, the results showed that the angular distortion of the specimens with mix of the ZrO2 and TiO2 activated flux were 225% less than the specimen without activated flux. The results of macroscopic examination of different samples showed that the maximum length and width of the macroscopic grains were related to the sample with 90% ZrO2 activated flux and the smallest length and width of the macroscopic grains were related to the sample with 90% TiO2 activated flux. The hardness test results showed that the highest hardness of the samples was gained to 90% TiO2 activated flux specimen with 950 HV and the lowest hardness value for the sample with 90% ZrO2 activated flux with 410 HV. The results of all tests showed that surface activated fluxes (ZrO2 and TiO2) affected to the depth of penetration, face width, angular distortion, length and width of macroscopic grains and the hardness of weld metal by changing the longitudinal and transverse melt flow in the weld pool.

Experimental study of formability of friction stir welded ultra-thin sheets of IF steel

M. Safari

In this paper, the experimental investigation of formability of friction stir welded ultra-thin sheets of IF steel is investigated experimentally. First, the sheets are joined by friction stir welding process based on the tests determined according to the Taguchi design of experiments. The investigated parameters in the welding process are as tool rotational and traverse speeds. Then, the tailor welded blanks are formed based on dome height test up to the defect stage and the dome height is measured for each test. Therefore, the effects of friction stir welding process parameters on formability of friction stir welded ultra-thin sheets of IF steel are evaluated. The results show that by increasing the rotational speed, the dome height in forming process decreases, while with increasing the traverse speed, the formability of tailor welded blanks by friction stir welding process improves. Also, the results of optimization based on signal to noise ratio method show that the tool rotational speed has the greatest effect on the dome height of tailor welded blank.

Modeling of temperature in friction stir welding of duplex stainless steel using multivariate lagrangian methods, linear extrapolation and multiple linear regression

M. Yousefieh

In this study, the temperature in friction stir welding of duplex stainless steel has been investigated. At first, temperature estimation was modeled and estimated at different distances from the center of the stir zone by the multivariate Lagrangian function. Then, the linear extrapolation method and multiple linear regression method were used to estimate the temperature outside the range and center of the stir zone. Temperature estimation is based on three parameters rotational speed, welding speed and distance from the center of stir zone. In the first method, by generalizing the multivariate Lagrangian method, the multivariate Lagrangian temperature function was generalized according to the above parameters. In the second method, in order to investigate the effect of the variables in the regression model, a comparison of two complete models and a reduced model based on the sum of squares errors was used. Then, by analyzing the multiple regression equations governing the output variable, a multiple linear regression function was introduced. Since the temperature of the stir zone is not measurable by the thermocouple, so in general the best fit curve for estimating the function is when the modeling is based on parameters that minimize the error function.To implement the multiple linear regression method, the error function was introduced to minimize the sum of the error squares and the error derivative was calculated in relation to the parameters of tool rotation speed, welding speed and distance from the center of the stir zone. Therefore, multiple linear regression method was considered as the basic method and as a criterion with other methods. According to the results obtained from the prediction in the center of the stir zone, the temperature difference in all three methods is desirable and negligible. The maximum temperature difference of multiple linear regression method with multivariate Lagrangian method in all nodes was 18.8 ^oC and multiple linear regression method with linear extrapolation method was 26.36 ^oC. Therefore, the multivariate Lagrangian interpolation method is less different than the linear extrapolation method in the center of the stir zone and is more accurate.

The effect of bonding temperature on the characteristics of TLP bonded joints in AISI 2205/BNi-3/AISI 2205 assembly

S. A. Beheshti Bafqi

In the present study, the transient liquid phase bonding of AISI 2205 dual phase stainless steel with amorphous BNi-3 interlayer was carried out. Based on the initial experimental and analytical studies, the parameters of temperature and bonding time were determined. In order to investigate the effect of bonding temperature on the microstructural changes of the joint, bonding was performed in the temperature range of 1050-1200℃ for 20 min. The microstructural and phase analyses indicated the completion of isothermal solidification and the formation of a uniform Ni-solid solution in the bonding zone centerline. The interdiffusion between the bonding zone and the adjacent base metal resulted in the formation of boride and nitride intermetallic compounds in the base metal adjacent to the bonding zone, which the area fraction of this intermetallics significantly decreased with increasing bonding temperature from 1050℃ to 1200℃ (reduction of the intermetallic area fraction from 85% to 40%). Evaluation of shear strength of samples showed that despite the completion of isothermal solidification in all samples and shear strength of bonded samples significantly depends of amount and morphology of intermetallic compounds on the transient liquid phase bonding shear strength. By increasing the bonding temperature to 1200℃ and reducing the area fraction of intermetallic compounds up to 40% of the shear strength of the samples increased from 450 MPa of TLP bonded specimen of 1050℃ to about 85% of base metal shear strength.

The evaluation of microstructure and mechanical properties of API 5L X80/DSS 2205 weld metals produced by PCGTAW

R. Dehmolaei

Microstructure and mechanical properties evaluation of diffusion bonded joints of titanium to AISI 304 austenitic stainless steel

S. Z. Anvari

In this study, diffusion bonding between titanium and AISI 304 austenitic stainless steel by Ag interlayer was investigated. In order to carry out this research, samples prepared after surface preparation were placed inside the fixture and placed at the temperatures of 750,800 and 850 °C in the 30,60 and 90 min in the furnace under argon protective gas. The phase transformation and microstructure of diffusion bonding interfaces of the joints were studied using optical microscopy, scanning electron microscopy and x-ray diffraction. Then, the hardness of the samples was measured using a hardness test apparatus. Finally, the samples were tested after being placed in the shear strength test holder using a pressure test device and the shear strength of the samples was measured. Examination of optical microscopic images shows the diffusion of silver in titanium and the partial diffusion of silver in stainless steel. On the other hand, increasing the temperature increases the diffusion region as well as increasing the grain size in the specimens. SEM images from the samples also confirmed the diffusion of silver in titanium and partially diffusion into stainless steel. The results of the XRD test on the samples showed that the temperature rise to 800 °C leads to the formation of TiAg and Ag₃Fe₂ intermetallic compounds, which the existence of TiAg intermetallic compound increases the hardness of the sample. For this reason, the sample at 800 °C showed the highest hardness. The shear strength of the samples showed that the increase in temperature increased the shear strength of the samples and decreased the shear strength by increasing the temperature above 850 ° C due to the formation of brittle intermetallic compounds.

Corrosion behavior of dissimilar welded joint between Inconel 617 alloy and A387-Gr.11 low-alloy steel

Z. Shahryari

In this study, Inconel 617 alloy was welded to A387-Gr.11 low-alloy steel using ER309L filler metal via gas tungsten arc welding (GTAW). First, the corrosion behavior of Inconel 617, A387-Gr, and the weld metal was evaluated by the Tafel polarization test and electrochemical impedance spectroscopy (EIS) in acidic (H2SO4), neutral (NaCl), and combined (H2SO4 + NaCl) solution at ambient temperature. The results of polarization and EIS measurements in all corrosive solutions indicate that the corrosion resistance decreases from 617 alloy to weld metal and from weld metal to low-alloy steel, respectively. The Comparison of the polarization curves of the base metals and the weld metal showed susceptibility to galvanic corrosion between Inconel 617 / weld metal in 1M NaCl solution. The behavior of galvanic corrosion of this pair was evaluated using the mixed potential theory and the electrochemical noise measurement. The results showed that in a galvanic couple of alloy 617 / weld metal, the weld metal acts as anode and corrodes in such a way that its corrosion rate increases from 0.22 μA/cm2 before joining to 1 μA /cm2 after joining.

Ultrasonic welding of thermoset matrix composites reinforced with glass fibers using a co-cured retaining layer

A. JabariRad

In this paper, ultrasonic welding of glass fiber reinforced thermoses, co-cured whit a thermoplastic has been studied. Co-curing process forms a connection between the thermoset and the thermoplastic while curing the composite. Considering that the calculated stress should not be related to the dimensions of the sample, a horn with a tip dimension smaller than the standard overlap was used. The results show that the actual weld dimensions are bigger than the intended weld dimensions. This has happened due to the movement of the melted thermoplastic to the sideways during the welding. The design of experiment has been done using response surface central composite, and a quadratic equation based on the lap shear strength of the welds containing three principle parameters time, force and amplitude was suggested, as well as predicting the optimum values. The equation shows that the force is an insignificant factor. In the samples with a higher time value the thermosetting resin started to degrade. The dominant failure mode of the specimens is segregation between the thermoset and fibers. The results show that the optimum parameters can result in a lap shear strength of 28.2 MPa, which is a very decent value compared to other methods of joining.

Evaluation of fatigue behavior of cast and ultra-fine processed Al-7075 by using friction stir technique

A.R. Soltanipour

This paper presents experimental results on the fatigue properties of the modified microstructure of cost Al-alloy 7075 via friction stir processing (FSP). The microstructural behavior was investigated by using optical microscope (OM). The grain size of cast FSP-ed at different locations was investigated via XRD. Uniaxial tensile and bending fatigue tests were carried out at room temperature on both cast and after FSP conditions. Fatigue properties were investigated using a fully reversible bending testing machine. Significance enhancement of mechanical properties was attributes to the elimination of porosities as well as uniform distribution of ultra-fine grains throughout the matrix. A fractographic study was done to understand the fracture behavior being changed from quasi-cleavage fracture to dimple fracture. The resultant ultra-fine grain structure causes significant increasing in tensile and fatigue properties.