Welding Brazing Research Articles

The Effect of Connections on The Global Response of Built-up Cold-formed Steel Beams with Corrugated Webs

The objective of this paper is to quantify the slippage and rotation in the connections of a double fixed corrugated web beam. Two types of connections between the component parts of the built-up beam were used, i.e. MIG brazing and spot welding, which offer different rigidities and bearing capacities for the built-up beams. Experimental tests were conducted on three MIG brazed and two spot welded specimens, respectively. The test setup consisted of a six-point bending configuration which is equivalent to a uniform distributed load applied to the beam. The load was applied from a 500kN actuator through a leverage system that allowed the distribution of the force. An out-of-plane structure prevented the beam from lateral torsional buckling. The testing exhibited relatively large slippage and deformation in the bolted connections and in the supporting device, respectively. However, the high rigidity of the beam maintained the mid-span deflection in the serviceability limit state limits. The built-up corrugated web beams made of cold-formed steel profiles represent an efficient and suitable structural solution for buildings. Nevertheless, experimental research due to inevitable slippage and the endplate deformation must be performed to characterize the connection.

Effect of brazing temperatures on microstructure and properties of TC4/Ti57Zr13Cu21Ni9/316L

Titanium alloy is an important metal material with excellent specific strength, which is widely used in aerospace field, nuclear industry, chemical medicine, and military industry. In order to investigate the connection conditions of TC4 titanium alloy and 316L stainless steel at different temperatures, the braze welding measurement with Ti57Zr13Cu21Ni9 filler metal was conducted in vacuum. The microstructure, morphology and phase of the joint were characterized by SEM (scanning electron microscope), EDS (Energy Dispersive Spectrometer) and XRD (X-ray diffraction), respectively. Microhardness and shear strength of the joint at room temperature and the bonding mechanism of TC4 and 316L were also investigated. The obtained results revealed that the main phases in the diffusion layer were Ti-based solid solution and Ti-Fe (TiFe and TiFe2) intermetallic compoundsands (IMCs) the center of the braze was mainly composed of Ti-Fe IMCs, (Ti, Zr)2(Ni, Cu), Ti-based solid solution. Additionally, the increase of brazing temperature firstly increased and then decreased the average shear strength with the maximum value of 133.9 MPa at 960 °C.

About the possibility of application of laser vacuum welding for the integration of elements of heat-protective structures from powder materials

The results of studying the process of laser vacuum welding of elements of heat-shielding panels made of heat-resistant dispersion-strengthened powder materials Ni-20Cr-6Al-Ti-Y2O3 of increased strength are presented. Such materials can be used to create ultralight heat-shielding panels, which are systems integrated on the surface of aircraft from typical modules of a cellular structure.
 Technical solutions of heat-insulating modules are considered, which are a cellular (honeycomb) structure consisting of two plates with a thickness of 0.1 to 0.14 mm, inside which there is a thin honeycomb filler. It is shown that the small thickness of the plates and the complexity of integrating the elements into a single system significantly impair the formation of a strong connection of such elements and do not allow the direct use of the known methods of diffusion welding or vacuum brazing.
 It has been established that laser welding of elements of heat-shielding structures in vacuum provides satisfactory strength of the structure of the heat-shielding element as a whole. Local heating at certain points prevents deformation of the parts to be joined during the welding process. The use of a pulsed Nd:Yag laser with a power of 400–500 W, operating in the frequency range of 50–200 Hz, allows welding with or without a filler powder. It was found that the use of filler additives practically does not affect the mechanical properties of the welded joint, however, it reduces the melt zone, while increasing the density of the welded joint.
 Based on the results obtained, it was concluded that it is possible to use laser vacuum welding for the integration of thin elements of heat-shielding modules. It is shown that a satisfactory joint strength is achieved by ensuring high cleanliness of the surfaces of elements before welding, maintaining a high vacuum (less than 10–2 Pa) and rational thermal loading of the surfaces of the elements to be integrated.
 The use of the proposed process makes it possible to obtain a stronger and denser seam in comparison with the known methods of soldering multicomponent powder dispersion-strengthened materials

Experimental Investigations on Capabilities of Resistance Spot Welding and MIG Brazing for Producing Corrugated Beams Using Galvanized Steel Sheets

This paper summarized the research work carried out by a team from Department of Steel Structures and Structural Mechanics, together with Department of Materials Science and Engineering, from University Politehnica Timisoara, which tried to determine the possibility to use welding for obtaining built-up cold-formed steel beams made of corrugated galvanized steel sheets (grade S350GD+Z). There were analyzed two joining processes: MIG brazing and Resistance Spot Welding with the aim to replace the self-drilling screws used until now. The results are very promising and these solutions of joining have beside economic advantages also technical and quality ones.

Joint Properties of Aluminum Alloy and Galvanized Steel by AC Pulse MIG Braze Welding

In response to global environment and fuel efficiency regulations aiming to reduce CO2 emissions, multi-material structures that use lightweight materials are currently being developed to realize the weight reduction of vehicles in automotive manufacturing. The dissimilar welding of aluminum alloy to steel has great importance, but it is still challenging due to their widely varying thermo-physical properties and the formation of intermetallic compounds. This study aimed to investigate the effect of process parameters on the wettability, mechanical properties, and microstructure in AC Pulse MIG welded joints of AA6061-T6 and galvanized steel sheets. A parametric study on torch aiming position and welding current with EN ratio variation was performed to optimize the process parameters. The result showed that the amount of metal deposition increased with EN ratio. When the EN ratio was higher, the wire feeding speed increased and the heat input process lowered. Moreover, the wetting length increased, ranging from 6.6 to 8.4 mm, and the wetting angle increased from 31.2 to 67.6°, respectively. As a result of the tensile shear test, the maximum tensile shear load of dissimilar welded joints produced at 70 A with a 20% EN ratio was approximately 8.8 kN. From the result of scanning electron microscopy with energy-dispersive spectrometry, FeAl3 IMC was observed at the joint interface, and the IMC layer thickness decreased with EN ratio at 70 A.

Growth characterisation of TiAl3 during initial period of hot dip aluminising on Ti6Al4V

ABSTRACT The interface reaction between solid titanium alloy and liquid aluminium is critical to understanding the evolution of the intermetallic compound (IMC) in brazing and weld brazing processes of titanium to aluminium dissimilar alloys. In this study, hot dip aluminising of solid Ti6Al4V under different temperatures was conducted to reveal the influence of reaction temperature and time on interfacial IMCs. Scanning Electron Microscopy (SEM), Electron Probe Micro Analysis (EPMA) and X-Ray Diffraction (XRD) were employed to investigate the interfacial microstructures and phases. The dominant IMC at the interface was identified to be TiAl3. With increasing dipping temperature and time, the thickness of TiAl3 increased. The TiAl3 layer grew parabolically and its growth was governed by a diffusion mechanism. A deviation from the normal parabolic to a smaller n value (n = 0.2) was observed and an activation energy of 71.6 kJ mol−1 was obtained. Both aluminium and titanium atoms were diffusing species through the TiAl3 layer. Grain coarsening of the TiAl3 and the existence of vanadium in the IMC possibly led to the deviation in the present study from the normal parabolic laws.

Effect of axial magnetic field on TIG welding–brazing of AA6061 aluminum alloy to HSLA350 steel

External magnetic field (EMF) is favored for application in welding, due to its positive effects on joint quality. In the present study, the effect of EMF on AA6061 Al alloy/HSLA350 steel welded joints were investigated. When no EMF, coarse Al grains were formed on the welded joint. The second phase including Al–Si eutectic and large Al3FeSi slats exists in the joint fusion zone. Refinement of the Al matrix and second phases were produced as a result of the Lorentz force generated by the 380 mt EMF treatment. The joint strength with EMF treatment at welding current 60 A increased from 170 MPa (without EMF treatment) to 195 MPa and the joint ductile fracture position was on the Al alloy base material under this same condition, due to the fine grained strengthening and dispersal strengthening of the second phases, meanwhile, the intermetallic compounds (IMCs) layer at the Al/steel welding seam interface was significantly reduced.

Simulation between Soldering and Brazing of Copper at 450 Temperature by Zn-Sn Fillet Alloy

In this research, a comparison between Soldering and Brazing welding of pure copper metal using a (Zn-Sn) alloy filler was numerically investigated. The welding operations on the eight pieces with dimension (30mm x 20mm x 2mm) were carried out used (Auto Desk Inventor program) to prepare four samples, while the simulation was conducted on these samples by utilized the (COMSOL Multiphysics 4.1 program) to investigate the heat distribution and tensile stress. The simulation study results showed that the thermal distribution of Soldering welding was less than that of the Brazing welding in the area between (40-60 mm) and the maximum temperature of Soldering welding in that region was (405 °C), while the highest temperature for the Brazing welding in the same area reaches to (449 °C). The total displacement of the Soldering welding was up to1.9 x10-7 mm greater than that of the Brazing welding when the shedding stress equal to 5x104 N/ m2

Залишкові напруження в з’єднаннях тонколистової оцинкованої сталі після дугового зварювання та плазмового паяння

Залишкові напруження в з’єднаннях тонколистової оцинкованої сталі після дугового зварювання та плазмового паяння

Developing a New Type of Jointing the Metal Plates of a Heat Exchanger

This paper proposes using a new composition of the metal polymer compound to joint heat exchanger plates. This composition makes it possible to improve the factors of plate junction, such as the cost, safety, efficiency, and rate of the junction procedure. We consider the benefits and drawbacks of the two main ways to joint metal plates of brazed steel plate heat exchangers (BPHE), namely, copper brazing and laser beam welding; propose to joint plates using a metal polymer compound consisting of the metal powder of steel 316L and binding agents; show the metal polymer compound production process; provide the results of the component mixing process depending on the parameters, such as duration and rate of mixing; as well as present the resulting density of the specimens made of the metal polymer compound, depending on the mixing conditions.

On the Joint Formation and Interfacial Microstructure of Cold Metal Transfer Cycle Step Braze Welding of Aluminum to Steel Butt Joint

Cold metal transfer cycle step braze welding process was modified to successfully produce an aluminum alloy/Zn-coated steel linear joint with a closed square butt joint configuration. The braze-welded joint shows wide-spreading and low wetting angle of molten filler alloy on both sides of the steel. The butt joint is formed by the overlapping of individual spot braze welds during cold metal transfer cycle step braze welding. The microstructure at the front, backside, and face side interface of the Al/steel joint were characterized in terms of the crystal structure, morphology, and thickness of intermetallic compounds by scanning electron microscopy, analytical transmission electron microscopy, and energy dispersive X-ray spectroscopy. The interfacial structure of Al/τ5(H)-Al8Fe2Si(film-like)/θ-Al3Fe(rod-like)/θ-Al3Fe(500 nm)/η-Al5Fe2(2.5 µm)/Fe is formed at the front interface associated with high-temperature interaction between liquid Al alloy and Zn-coated steel. On the contrary, Al/τ5(C)-Al8(Fe,Mn)2Si/τ5(H)-Al8Fe2Si/θ-Al3Fe(1.2 µm)/η-Al5Fe2(500 nm)/Fe is present at the backside interface associated with relatively low-temperature interaction between liquid Al alloy and Zn-coated steel. The intermetallic compounds and morphology at the face interface associated with medium temperature interaction are similar to those at the backside interface. However, the thickness of the η-Al5Fe2 layer is only 220 nm, which is caused as a result of the interaction of molten Al filler alloy with the bare steel sheared surface without Zn coating. The mechanism for the formation of varied intermetallic compounds at the different interfaces is discussed.

Experimental Studies of Different thick Steel sheets and variable clearance in MIG Brazing

Current automotive industry trend is developing the new materials and technologies for automobile BIW to enhance the latest stringent requirements like safety, weight and safer body. Main aim is to reduce the weight of body without compromising the targeted quality and safety norms. One of the solutions is different grades of steel sheets and different thickness combination are used combinedly to weld depend on the function of the designed structural component. Reduction of weight is searched most in the recent high strength steels. Target is to reduce dead load and reduce the cost. In this scenario roof outer and inner panel which is having closed ring type assembly. For ring panel assembly different thickness materials and variable clearance joinery is welded by MIG brazing tags. As per benchmark study the strongest joint 930.8 Mpa is achieved when the joint clearance is .038mm. When the clearance is narrower than it’s harder for the filler metal to distribute itself adequately throughout the joint and joint strength is weakened. Conversely, if the gap is wider than necessary, the strength of the joint will be reduced almost to that of the filler metal itself. But in ordinary day-to-day brazing, need not this much precise to get a sufficiently strong joint. In this study analyzing the tensile shearing strength of the joinery with respect to the thickness and variable clearance. Also, parameters contributing to the strength variation. MIG brazing welding processes is using CMT machine and CuSi3 of brazing wire.

Comparison of properties of Al-Cu soldered and resistance welded joints

The paper presents the results of qualitative tests of Cu-Al joints made by soldering, brazing and resistance welding. Aluminum and copper tubes with a diameter of 6.9 mm, used, among others in refrigeration systems, were soldered with ZnAl2 and AlSi12 filler metal. In addition, similar connections were made by resistance welding. Macroscopic tests of soldered and welded joints were carried out and the hardness distribution on the cross-section of joints was determined. The analysis of research results allowed to state that resistance welding of Cu-Al joints can be a good alternative to the soldering process, especially in series production, due to the possibility of easy application of process mechanization.

Microstructure and Performance of Laser-Welded GH3128/Mo Dissimilar Joints

Laser beam offset welding of GH3128 and molybdenum (Mo) dissimilar joints was studied with an emphasis on the role of laser beam offset (LBO). It was found that the change of LBO significantly affected the properties of GH3128/Mo dissimilar joints. When the LBO increased from − 0.1 mm (i.e., laser spot was centered on Mo surface) to + 0.3 mm (i.e., laser spot was centered on GH3128 surface) at the step size of 0.1 mm, the amount of melted Mo gradually declined; the welding mode gradually changed from fusion welding to welding–brazing; macro-segregation of Mo-rich phases in fusion zone (FZ) gradually disappeared; the average microhardness of FZ significantly decreased, and therefore, microhardness distribution in FZ became more uniformly; the quantity of grain boundary liquation observed in heat-affected zone (HAZ) of GH3128 side gradually decreased; and recrystallization of grains in the HAZ of Mo was gradually suppressed. Joints with the optimal LBO of + 0.2 mm reached the maximum tensile strength of about 560 MPa. When using a small LBO, i.e., LBOs were + 0.1, 0, − 0.1 mm, the HAZ of Mo was greatly softened and embrittled. When adopting a large LBO, i.e., LBO was + 0.3 mm, the melt near Mo-FZ interface might fail to moisten Mo surface and spread on Mo surface, thus resulting in the reduction in tensile strength.

Research Status and Progress of Welding Technologies for Molybdenum and Molybdenum Alloys

Owing to its potential application prospect in novel accident tolerant fuel, molybdenum alloys and their welding technologies have gained great importance in recent years. The challenges of welding molybdenum alloys come from two aspects: one is related to its powder metallurgy manufacturing process, and the other is its inherent characteristics of refractory metal. The welding of powder metallurgy materials has been associated with issues such as porosity, contamination, and inclusions, at levels which tend to degrade the service performances of a welded joint. Refractory metals usually present poor weldability due to embrittlement of the fusion zone as a result of impurities segregation and the grain coarsening in the heat-affected zone. A critical review of the current state of the art of welding Mo alloys components is presented. The advantages and disadvantages of the various methods, i.e., electron-beam welding (EBW), tungsten-arc inert gas (TIG) welding, laser welding (LW), electric resistance welding (ERW), and brazing and friction welding (FW) in joining Mo and Mo alloys, are discussed with a view to imagine future directions. This review suggests that more attention should be paid to high energy density laser welding and the mechanism and technology of welding Mo alloys under hyperbaric environment.

Assessment of structure and selected mechanical properties of braze welded joints of copper-lined steel tubes

In the paper, results of a research on braze welded joints of copper-lined 10CrMo9-10 (10H2M) steel tubes made by CMT arc braze welding are presented. As a filler metal, silicon bronze was applied. Results of metallographic examinations with the use of light microscopy, electron scanning microscopy and X-ray microanalysis are presented. Mechanical properties of the joints were assessed on the grounds of static tensile test, technological bending test, as well as hardness measurements. Quality of the obtained joints was good. No cracks were observed in the brazed joints and the obtained mechanical properties were satisfactory.

Mechanism of Zn Coating on the Wettability, Spreadability, and Microstructure of Al/Steel with the Laser Welding–Brazing Method

The wettability and spreadability of the molten Al drop on the surface of bare steel and galvanized (GI) steel was studied. It was expected that the role of Zn coating during the laser welding–brazing process of Al/steel could be understood through this study. The bare steel without coating and the GI steel with different Zn coating thicknesses of 10 and 20 μm were used. Different laser power was considered. The welding time was 1000 ms. Deposited filler metal ER4043 was applied, and the feeding rate was 5 m/min. The transferring, wetting, and spreading process of the molten drop on the steel surface was observed and recorded by a high-speed video camera. The temperature field was measured by an infrared thermometer. The microstructure of the joint was observed and analyzed after welding. The GI steel with a 10-μm coating improved the wettability of Al/steel compared with the bare steel, but the GI steel with a 20-μm coating deteriorated the wettability and the weld appearance compared with the GI steel with a 10-μm coating. The evaporation of Zn coating could protect the steel surface from oxidation and absorb the excessive heat input. The formation of the brazing interface and Zn-rich zones was revealed based on the adsorption values of Al-Si/Fe and Al-Zn/Fe systems.

Influence of energy ratio on dual–spot laser welded–brazed Al/steel butt joint

Al/steel butt joints were successfully obtained using a dual–spot laser welding–brazing process with different R (R = E Fe :E Al = 4:6, 5:5, and 6:4; E Fe and E Al represented the energy ratios of the laser near steel and Al, respectively). The molten filler metals wet and spread well along the front and back surfaces of the steel when R was 5:5 and 6:4, whereas an undercut occurred when R was 4:6. The interfacial intermetallic compound (IMC) along the brazing interface consisted of only thin–layered τ 5 –Fe 1.8 Al 7.2 Si when R was 5:5 and 4:6. The IMC had a greater thickness when R was 5:5 owing to its higher peak temperatures than when R was 4:6. A mixed IMC (θ–Fe(Al,Si) 3 +τ 5 –Fe 1.8 Al 7.2 Si) was newly formed in the top region of the brazing interface when R was 6:4. TEM observations revealed that two types of grains existed in θ–Fe(Al,Si) 3 : normal and twinned. Numerical simulations for the thermal cycles along the brazing interface indicated that the IMC thickness was determined by the interfacial peak temperature, while the IMC homogeneity was determined by the temperature gradient. The results of an experiment involving the tensile properties indicated that the highest average joint strength (193 MPa) and largest average fracture displacement (0.64 mm) when R was 5:5, owing to its satisfactory weld formation and reasonable IMC distribution.

Research on Friction Stir Spot Welding Brazing Process and Properties of Dissimilar Metals DP590 and 6061

Friction stir welding (FSW) is the most popular and efficient method for solid‐state joining of similar or dissimilar metals and alloys. This technology is mostly applied in aerospace, rail, automotive, and marine industries. In order to reduce the weight of special auto parts, friction stir spot welding (FSSW) was proposed by some researchers for the connection of steel‐aluminium dissimilar metals. However, the steel‐aluminium joints welded by FSSW are prone to brittle fracture and have lower shear load although they have high mechanical connection strength. The friction stir spot welding brazing process integrates the brazing effects with the friction welding effects by the addition of solder. A study of FSSW of DP590 and 6061 with the filler metal added was carried out in this paper. The orthogonal test was performed to optimize the process parameters in order to achieve the best shear load of the joint. The shear strength of the joint was studied by the shear test. The fracture morphology was investigated by optical microscopy (OM), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). The results showed that the shear load of the joint could reach 13.239 kN when the rotating speed, depth, and residence time of the mixing head were 1000 r/min, 0.2 mm, and 90 s, respectively. The aluminium‐zinc solder added could well wet the interface between aluminium and steel and promote the metallurgical bonding, thereby improving the shear load of the joint. The temperature field of DP590/6061 FSSW process was simulated by ANSYS software to verify the rationality of the optimal process parameters. The simulation results were confirmed to be basically consistent with the data measured by the thermocouple.

Effects of laser power on the interfacial intermetallic compounds and mechanical properties of dual-spot laser welded–brazed Ti/Al butt joint

A sound Ti/Al butt joint was successfully obtained by dual-spot laser welding–brazing with a Al-12Si wire as the filler. The influence of laser power on the weld appearance, microstructure of the interfacial intermetallic compounds (IMC), and tensile strength of joints was investigated. With an increase in laser power, the thickness of IMC layer also increased and the morphology of IMC layer changed from a cellular-shape to a serrated-shape, and finally to a club-shape. The microstructure of the interface IMC comprised a brazed zone in which Ti(Al, Si)3 was dominant and the microstructure at the Ti/Ti(Al, Si)3 interface was composed of nano-sized granular Ti5Si3, and Ti7Al5Si12. The highest tensile strength of the joints could reach up 75% of that of the Al base metal. The inhomogeneous IMC layer at the brazing interface caused a decrease in the tensile strength of joints and induced a deflection of fracture path during the tensile process.