Solid-state Welding Method Research Articles

Analytical model for the temperature field around a nonuniform three-dimensional moving heat source: friction stir welding modelling

A transient semi-analytical solution is devised to find the temperature distribution around a nonuniform three-dimensional heat source in a finite rectangular plate with cooling surfaces and nonhomogenous boundary conditions. This solution can serve as a viable tool to find the temperature field and consequently provides useful insights into material modelling and response in a variety of industrial applications, including friction welding processes. As a numerical example, the established solution is applied to the friction stir welding as a solid-state welding method. The comparison between the obtained analytical results and the results found through FEM and experiment showed that the analytically obtained results and the numerical and experimental data are in good agreement.

Effect of cooling media on residual stresses induced by a solid-state welding: underwater FSW

In this article, the effect of cooling media on the residual stresses (RS) induced by a solid-state welding process is scrutinized through measuring and comparing RS caused by friction stir welding (FSW) underwater and in open air using the non-destructive ultrasonic method for aluminum AA7075-T6. Underwater FSW as a solid-state welding method can extend the application of solid-state welding techniques in marine industry. Results reveal that the longitudinal and transverse RS reduce under the water compared to open air. This reduction in the longitudinal RS is the maximum within the nugget zone (about 17 %). Meanwhile, such reduction for the transverse RS reaches 70 % within the heat-affected zone. In addition, under both air and water, the longitudinal RS is several times greater than the transverse RS and is in tensile and compressive states inside and outside the nugget zone, respectively.

FEM analysis of temperature distribution and experimental study of microstructure evolution in friction interface of GH4169 superalloy

Abstract The linear friction welding (LFW) process is a very effective solid-state welding method. Friction process is very significant for temperature distributions on the surface between two contacting workpieces during LFW process. In this paper, a finite element method (FEM) model is implemented to analyze the temperature distributions in friction interface of GH4169 superalloy cylindrical specimens. The simulation studies were conducted using ABAQUS software. Temperature distributions during the simulation of one rotation of the pressure head on the specimen were simulated. Temperature distributions of specimens in the end of different rotations were also investigated. The validation experiments were conducted to validate the simulation results. The detailed microstructure investigations demonstrate that the temperature distributions obtained in the present model are correct. This friction model is able to simulate the friction process of the GH4169 superalloy, but further research about FEM models is still needed for more precise prediction of microstructure evolution in the friction process of this alloy.

Study on governing parameters of thermal history during underwater friction stir welding

Underwater friction stir welding (FSW) could widely extend the submarine applications of solid-state welding methods. Since, in the case of underwater FSW, the temperature field exhibits profound effects on the acquired weld properties, studying the corresponding governing parameters is of high priority. With this end in view, in order to explicate the heat generated by the FSW tool, the applied forces on the FSW tool, as the unknown parameters in the heat generation equation, are obtained. Subsequently, the heat transfer of the surrounding fluid, which dictates the heat transfer through the workpiece is investigated. The results reveal that upon comparison to FSW in air medium, both translational and axial forces considerably increase leading to greater heat generated by the underwater FSW tool. However, the peak temperature in each point during underwater welding declines dramatically (40 %) compared to the in-air welding, which can be attributed to the extreme boiling heat transfer of water on both the workpiece and FSW tool. This behavior may be the main reason for the acquired mechanical properties of the underwater-welded AA7075-T6 plates as a precipitating hardening alloy. The mentioned heat transfer is non-uniform over the workpiece and comprises different types including nucleation and transition boiling as well as free convection. Furthermore, the study of the mechanical characteristics revealed that underwater welding leads to joints with more strength and lower ductility compared to those obtained by in-air welding.

Torsional Behavior of AISI 420/AISI 4340 Steel Friction Welds

Abstract The solid-state friction welding method, which is widely used in the automotive, machinery, aviation and aerospace industry, was applied in this study. AISI 420 martensitic stainless steel, which is difficult to join by using fusion welding methods, and AISI 4340 tempered steel, which is commonly used in the automotive industry, were joined. During the welding process, three different rotations as 700, 1000 and 1300 rpm were used and parameters such as friction pressure, friction time, upset pressure as well as upsetting duration were kept constant. After the welding process, welded joints were examined macroscopically and microscopically, and their microhardness were measured. Then, torsion tests were performed on these samples. During the torsion tests, the samples fractured outside the welded joint regions. Thus, it was concluded that torsional strength of welded joint zones was high and AISI 420 and AISI 4340 steels were smoothly joined by friction welding.

Dissimilar-Metal Joining Using Several Types of High-Speed Solid-State Welding Methods

Solid-state welding is useful to join dissimilar metal couples, in particular, with a large difference in physical and mechanical properties. However, conventional solid-state welding methods such as diffusion welding and roll bonding are not necessarily applicable to all metal combinations. In addition, they are time-consuming. In the present study, various dissimilar metal joints (e.g. Al/Fe, Al/Cu, Al/Ni, A2024/A5052, A6022/steel, A6022/Plated steel, A2024/AZ80) were fabricated by using several types of high-speed solid-state welding methods; friction stir spot welding, advanced stud welding and impact welding. The strength and characteristic interfacial morphology of the joints were investigated, and each joining mechanism is discussed. In particular, for the impact welding, both experimental and numerical analyses were performed. Two metal sheets were obliquely collided at a very high speed and joined by magnetic pressure or explosive force. Smoothed Particle Hydrodynamics (SPH) method was used to simulate the impact welding process. The emission of metal jet and the evolution of characteristic wavy interface at the joint interface could be clearly visualized. The effects of collision angle, collision velocity and difference in density of the metals on the wave morphology were revealed.

Welding strain analysis of friction stir-welded aluminum alloy structures using inherent strain-based equivalent loads

Friction stir welding is a solid-state welding method commonly used for aluminum alloy or lightweight metal. It has the advantages of low welding strain, high welding quality, and low residual welding stress while requiring no protection gas. Welding strain analysis of friction stir welding using finite element analysis has been the subject of many studies that focused on the substance fluid using threedimensional computational fluid dynamics; however, this approach is inefficient for large structures and requires much time for analysis. To address this drawback, this study proposes a faster method for analyzing extruded aluminum material that exploits the advantages of the inherent strain-based equivalent load.

The Effect of Helical Pin Profiles on the Friction Stir Welding Performance of Aluminium Alloy AA6082

Abstract In this study, one of the solid state welding methods, friction stir welding, was studied with the AA6082 aluminum alloy. Two types of pins with a special geometry were used to investigate the effect of pins profile, tool rotational speed, and welding speed on the mechanical properties of welded joints. The pin profile was associated with weld joint properties such as tensile strength, elongation, bending strength, bending force, hardness distributions and temperature. Results have shown that the friction surface area of the pin has a significant role on the mechanical behaviour of the joint. The results of tensile tests associated with the pin profile indicate that the helical two-flute pin has a high tensile strength and elongation compared to the helical four-flute pin. Discrepancies in the tensile strength of the welded samples of the two pin profiles have been found between 37–55 % at the same welding conditions. Despite the relatively poor static properties, the helical four-flute pin has better bending properties. Higher bending strength and force (260.634 MPa and 347.513 daN) were obtained at test conditions of 2000 rpm and 100 mm/min. Bending without any defect on the joint was achieved at 2000 rpm and 200 mm/min. The effect of welding parameters on the hardness profile was not clear, and it has been observed that, in comparison, the helical two-flute pin did not create a remarkable difference with regard to hardness.

Weldability of AISI 304 to Copper by Friction Welding

Abstract Friction welding is a solid-state welding method, which can join different materials smoothly and is excessively used in manufacturing industry. Friction welding method is commonly used in welding applications of especially cylindrical components, pipes and materials with different properties, for which other welding methods remain incapable. AISI 304 stainless steel and a copper alloy of 99.6 % purity were used in this study. This couple was welded in the friction welding machine. After the welding process, samples were analyzed macroscopically and microscopically, and their microhardness was measured. Tensile test was used to determine the bond strength of materials that were joined using the friction welding method. At the end of the study, it was observed that AISI 304 stainless steel and copper could be welded smoothly using the friction welding method and the bond strength is close to the tensile strength of copper.

Microstructure and Joint Strength of Similar- and Dissimilar Lap Joints Fabricated by Several Advanced Solid-State Welding Methods

Both similar- and dissimilar metal joints, which are difficult to be welded by using ordinary fusion welding methods, were successfully obtained by using several advanced high-speed solid-state joining methods. (1) Al/Al, Cu/Cu, Al/Fe(Steel), Al/Cu, Al/Ni, Cu/Ni and Al/Bulk metallic glass lap joints were magnetic pulse welded by means of mutual high-speed oblique collision of metal sheets at a high speed of about 500m/s. (2) 2xxx aluminum alloy pins were stud-welded to 5xxx alloy aluminum sheets and several kinds of plated steel sheets at a high speed by using a specially designed discharge circuit. The welding was achieved within a few milliseconds without producing any weld marks on the back surface of the plate. (3) 6022 aluminum alloy sheets were friction stir spot welded to steel sheets and various kinds of galvanized and aluminum-plated steel sheets. The welding was achieved within a few seconds. For those joints, joint strength and characteristic joint interface morphology were investigated.