Induction Brazing Research Articles

High-temperature lean Cu alloys with Cr-to-Nb atomic ratio of 2

Two Cu-Cr-Nb alloys, denoted as alloy 1 (comprising Cu-0.89 at% Cr-0.42 at% Nb) and alloy 2 (comprising Cu-1.84 at% Cr-0.99 at% Nb), were produced through a series of manufacturing processes including vacuum induction melting, melt spinning, consolidation, brazing, and baking, with both alloys aimed at achieving a nominal Cr-to-Nb atomic ratio of 2. Microstructural characterization using transmission electron microscopy and X-ray diffraction identified the cubic C15 Laves-phase Cr2Nb as the dominant precipitate in both alloys, cross-validated by thermodynamic calculations and atomistic simulation-based density functional theory (DFT). Besides cubic C15 Cr2Nb, hexagonal C14-phase Cr2Nb and α-BiF3 cubic structured Cr3Nb were also observed in the alloys, including a coherent interface formed between the Cr3Nb precipitate and the Cu matrix. The hardness of the alloys increases, and the electrical conductivity decreases with increasing alloying addition content; two practical equations described the trends. Further DFT simulations revealed that the electrical conductivity (conductance) of the Cu/Cr2Nb interface is an order of magnitude higher than the intrinsic Cu high-angle grain boundaries.

Induction brazing of DEMO's large bore cooling pipes

The DEMO first wall blanket components will be exposed to high neutron fluence and high levels of thermal energy, the latter being removed by a coolant fluid transmitted out of the reactor via service piping. Due to the thermal and nuclear loading on the first wall, the components will need to be periodically removed and replaced. Installation of new blankets requires the joining of their service pipes by remote handling.Brazing is one of the alternatives that are considered for joining the service pipes of the DEMO breeding blankets. This technique has great potential and has several major advantages over welding.The Fusion Technology Department of HUN-REN Centre for Energy Research (CER) has been working on the development of a viable brazing concept of thick, large bore pipes inside the ports of DEMO. Induction has been chosen as the heat source for the brazing operation, which is a well-studied technology and has many uses in the industry already. However, brazing in this size is a completely new horizon for induction heating so CER's work includes a significant amount of development. Firstly, the coil is naturally a bespoke component, which has been optimized by electromagnetic analysis. Secondly, a test rig has been designed and manufactured in-house by CER, to test the performance of the induction heater in a real scenario.This paper outlines the development strategy of the induction brazing of DEMO's large bore pipes.

Comparative study on induction brazing of diamond with rare earth Nd-doped crystalline and amorphous Ni-based filler alloy

This essay aims to comparatively study the microscopic morphology and grinding properties of brazed diamonds with amorphous and crystalline filler alloy in the case of rare-earth Nd-doped modified Ni-based filler alloy. The results show that at the same content of Nd, Cr7C3 is mainly generated at the brazing interface of crystalline samples. In contrast, Cr27C6 is mainly generated at the brazing interface of amorphous samples. Amorphous solder material achieves a robust chemical metallurgical union, producing a dense and homogeneous carbide layer. The bonding strength between amorphous solder material and diamond is further enhanced. The addition of rare earth element Nd contributes greatly to the forming ability of amorphous filler alloy. Nd atoms in the amorphous solder material readily bond with Ni atoms, reducing the chemical corrosion of Ni atoms on diamonds and resulting in a lower degree of graphitization. When the amount of Nd added is 1.0 wt%, the morphology of amorphous filler alloy brazing diamond is more complete than the effect of the crystalline state, the degree of thermal damage is lower, and the surface of amorphous filler alloy brazing is smoother. Frictional wear experiments show that the amorphous filler alloy holds diamond better than the crystalline filler alloy, and the diamond specimens prepared with the amorphous filler alloy demonstrate a significantly superior grinding performance in comparison to the diamond specimens prepared with the crystalline filler alloy.

Microstructure and Mechanical Properties of AA 6082/AISI 304 Joints Brazed Using Al-Ge-Si Filler Metal

Joining aluminum alloys with stainless steel is of great importance in many industrial sectors. Due to the low solidus temperatures of high-strength aluminum alloys, brazing with commercially available filler metals is not possible. Al-Ge-Si filler metals with a lower melting temperature of about 490 °C allow these alloys to be joined. They are manufactured in the form of foil via ultrafast solidification. AA 6082/AISI 304 joints are produced via induction brazing and vacuum furnace brazing. In this study, the tensile shear strength and the fatigue behavior of joints are investigated. Joints produced via induction brazing reached a maximum joining strength of 53 MPa, while vacuum-brazed joints achieved a maximum of 20 MPa. The fracture occurs in the reaction zone, especially inside the Al7Fe2(Si,Cr) intermetallic layer. The results of the fatigue tests show that the joints produced via induction brazing achieved 1 × 107 cycles at a stress amplitude of 7 MPa. Vacuum-brazed joints reached this at a stress amplitude of 3 MPa. All fatigue-tested samples fail in the reaction zone. The high hardness and growth of the SiGe solid solution and the Al7Fe2(Si,Cr) intermetallic layer had a major influence on the joining strength and fatigue behavior of AA 6082/AISI 304-brazed joints.

Microstructure and properties of diamond/Ni-based alloy composite coatings by induction brazing

Microstructure and properties of diamond/Ni-based alloy composite coatings by induction brazing

Influence of the application of ultrasound on the microstructure of cemented carbide/steel joints brazed with Ag49ZnCuMnNi

The poor wettability of cemented carbides by molten metals as well as the different material properties compared to steel makes thermal joining process challenging. In this regard, innovative ultrasonic-assisted induction brazing is capable of joining the materials quickly, cost-effectively and without using environmentally hazardous fluxes. Instead, the oxide scales are broken up within the joining process due to ultrasonic-induced cavitation in the molten filler alloy and hence promote the wetting. However, since the use of ultrasound in brazing steel/cemented carbide joints is still insufficiently investigated, there is still a need to explore the fundamental influences of ultrasound on the brazing process. In this work, the effect of ultrasound on the microstructure of the brazed joints and the diffusion depth of different elements were analysed. The two ultrasonic parameters activation time and amplitude were varied during the experiments. Acicular or dendritic structures that have formed in the braze metal without ultrasonic stimulation were transformed into globular structures, when ultrasound was applied. In addition, a non-eutectic silver-rich phase formed, which was not observed in joints manufactured without the use of ultrasound. Furthermore, the use of ultrasound led to increased diffusion between the base material and the filler material as well as the dissolution and distribution of oxides in the edge regions of the brazing joints.

Wear characteristics of single-layer cBN abrasive tools using ultrasonic vibration–assisted induction brazing techniques

Single-layer brazed superhard abrasive tools have been widely employed in grinding of difficult-to-machine materials in aerospace, aiming at the improvement of the grinding performance and quality. However, the chemical metallurgical reaction during conventional induction brazing (CIB) is severe, and the brazing quality is poor, resulting in a rapid wear and thus reducing service life of abrasive tools. In this case, the single-layer brazed cBN abrasive tools were fabricated using ultrasonic vibration-assisted induction brazing (UVAIB) technology, and the wear comparative experiments of Ti–6Al–4V alloys was carried out using UVAIB and CIB abrasive tools. Results indicate that compared to the CIB abrasive tool, the UVAIB abrasive tool has the higher average exposure height of abrasive grains, lower grinding forces and more stable grinding force ratio during wear processes. Meanwhile, the UVAIB abrasive tool has a slowly decreased exposure height of abrasive grains, a superior wear state and low proportion of macro-fracture as the material removal volume raises. In addition, UVAIB abrasive tool possesses micro-cracks at the top of abrasive grains, leading to micro-fractures of abrasive grains to improve the self-sharpening ability and grinding performance.

Induction brazing of Al2O3 ceramic and 316L stainless steel with Sn–Ti filler alloy

An induction brazing method for joining Al2O3 ceramic to 316L stainless steel (SS) was developed in this study. The Sn–Ti alloy was rapidly melted by induction heating, which enabled the active element Ti to react with O in Al2O3. Consequently, a metallurgical bonding formed between and Al2O3 and 316L SS. The microstructure of the joint was mainly composed of Fe2SnTi layer, FeSn2, Ti6Sn5 particles and TiO layer. The maximum shear strength of 20 MPa was obtained at 260 A/140 s. The induction heating exhibited a higher heating rate compared to traditional resistance heating, as evidenced by the brazing process with only approximately 140 s. The proof-of-concept study on the induction brazing of Al2O3 ceramic to 316L SS with high efficiency provides insights in the further development of ceramic/metal joining.

Key Parameters and Optimal Design of a Split Induction Coil for T-Shaped Pipe Brazing

The heat exchanger made up of several T-shaped joints is a critical component in energy equipment. A split induction coil was designed for T-shaped aluminum pipe brazing, and the Taguchi method was combined with multi-physical simulation to solve the multi-factor optimization of the split coil. The results showed that the multi-physical simulation model had high precision. The melting of filler metal was almost consistent with the spatial distribution of the temperature field, and the average simulation error was approximately 5.753 °C. The optimal coil parameters were obtained with a turn number of 3.5, a turn space of 7 mm, a heating distance of 15.6 mm, a coil diameter of 8 mm, and a coil length of 9 mm. Three well-formed T-shaped joints could be obtained at one time via the optimal split coil. During the induction brazing, the skin effects and the proximity effects induced a high magnetic field intensity around the joint, which had a significant relationship with the coil length and coil diameter. The high magnetic field intensity promoted a high eddy current density in this place, and as a result, the high Joule heat could be generated around the joint. In addition, the significant decrease in the heating rate at high temperatures promoted the homogenization of the temperature and the melting and filling of the filler metal as well as avoided local overheating.

Structure–Property Relationship in High-Strength Aluminum Alloys/Stainless Steel Brazed Joints

In many industrial sectors, for example, aerospace, automotive and high-performance electronic industries, there is a significant need to join dissimilar materials. In the case of medium-strength aluminum alloys, joints are commonly manufactured using Al-Si brazing fillers with a melting temperature of 575 °C. In comparison to medium-strength aluminum alloys, high-strength aluminum alloys exhibit lower melting temperatures. Therefore, the joining possibilities are limited. Due to the lower melting temperature of about 500 °C, Al-Ag-Cu brazing fillers allow the joining of these alloys. In this study, high-strength aluminum alloys/stainless steel joints were produced via induction brazing and vacuum furnace brazing. The mechanical properties of the joints were determined using tensile shear tests as well as fatigue tests at ambient temperature. The joints produced via induction brazing at 520 °C without holding time reached a maximum tensile shear strength of 32 MPa. The joints failed in the braze metal close to the reaction zone. The joints brazed in the vacuum furnace at 540 °C for 10 min reached a maximum tensile shear strength of 18 MPa. The fractures occurred in the reaction zone, especially inside the Al7Fe2Si intermetallic layer. The thickness of the intermetallic layers as well as the reaction zone had a significant influence on the joining strength and the fracture mechanism of the brazed joints. The results of the fatigue tests showed that the joints brazed without holding time achieved the defined limited number of cycles of 1 × 107 at a stress amplitude of 4 MPa. For all the fatigue-tested samples, the fracture occurred in the braze metal, especially in the eutectic. Hence, the reaction zone does not significantly influence the fracture mechanism of high-strength aluminum alloy/stainless steel brazed joints during cyclic loading.

Phase transformation and deformation of the high-frequency induction brazed grinding wheel based on multi-field coupling

With the characteristic of the high bonding strength to matrix, good sharpness, and large chip-storage spaces, the brazed super abrasive grinding wheels have superiorities in the machining of difficult-to-machine materials. However, thermal deformation is caused by the high temperature during the brazing process, leading to the accuracy of the brazed grinding wheel being degraded greatly. By means of local heating, high-frequency induction brazing can reduce the thermal deformation of the wheel. Aiming at the thermal deformation mechanism of the induction brazed wheel, a numerical simulation model of thermal-stress-phase multi-field coupling was established considering the temperature-dependent physical properties of the material. The simulation result indicated that the phase transformation occurred near the work surface of the wheel substrate. The depth of phase transformation layer decreased from 6.0 mm to 2.9 mm with the scanning speed increasing from 0.5 mm/s to 2.0 mm/s. The microstructure of the phase transformation layer mainly consisted of ferrite, pearlite, and bainite after brazing. An appropriate scanning speed was more important for the high accuracy of the wheel substrate during the induction brazing, since it had remarkable influence on the stress and deformation than brazing temperature. The experimental results of the microstructure morphology and deformation proved that the numerical simulation model was correct with 10.4% error.

Induction brazing of NdFeB magnet with PVD-deposited AgCu alloy

The NdFeB magnets service in high-power electric-mechanical conversion devices sometimes endure high stress and high-temperature impact, and adhesion of these magnets using glue cannot ensure the reliability. In this study, the NdFeB was induction brazed with physical vapor deposition (PVD)-deposited Ag72Cu28 alloy layer, then the microstructure, mechanical properties and magnetic properties of the brazed joints were characterized, and effects of the filler metal thickness and the induction heating time were analyzed. The results show that the PVD coating can effectively prevent the surface oxidation of the NdFeB. The AgCu filler metal penetrates into the NdFeB and is partly mixed with the liquefied Nd-rich intergranular phase of the NdFeB, forming a good metallurgical bonding. The thickness of the penetration layer increases obviously with increase of the heating time and filler metal thickness. The bonding strength of the NdFeB brazed joint increases firstly and then decreases with increasing heating time, and a peak bending strength of 196.94 MPa was obtained. Fracture of the brazed joint occurs inside the NdFeB substrate close to the penetration layer. After a further annealing, the coercivity of the brazed NdFeB sample is a little higher than that of the un-brazed sample, and the squareness decreases by only a little. Properties of the brazed joints might be further improved by optimizing the amount of filler metal and the induction heating parameters.

Computational model of soldered details heating with considering the magnetic field distribution

The main purpose of the software application is to simulate the temperature field in the process of induction pack of elements of machine-building structures of the fuel profile, which will further improve the quality of connections. The program simulates the flange heating process during the induction brazing process. The purpose of the developed module is to provide experimental studies of the induction soldering process. The program provides graphic information during the technological process, provides the ability to adjust the technological parameters, and allows the development of the technological process.

Effect of B on microstructure and properties of joints brazed by In-situ Ag-Cu-Zn-Sn filler metal with high Sn content

The copper brazed joints were obtained by induction brazing using in situ synthetic high Sn content silver filler metals with different B contents and the effect of element B on the wettability of filler metals and microstructure and mechanical properties of the joints were studied. With the addition of element B, the spreading area of the filler metals on the copper increases. The microstructure of the joints mainly consists of silver-based solid solution and copper-based solid solution, and the distribution of silver-based solid solution in the brazing seam becomes dispersed with the addition of B. The width of the brazing seam increases significantly with the increase in B content. Meanwhile, the B element was mainly distributed in the Ag-based solid solution. The tensile strength firstly increased and then sharply decreased with B added. The maximum average tensile strength of 206.83 MPa was obtained with a 2% addition of B and the joint fracture pattern is a brittle fracture.

Interfacial behavior of brazed Cu-Zn filler subjected to electromagnetic coupled cryogenic treatment

• A new electromagnetic coupled cryogenic treatment was applied to Cu-Zn interface. • The shear strength of the treated Cu-Zn filler interface increased by 35.2 %. • The treatment relieved the residual tensile stress of the Cu-Zn interface. • The dendrites and finer α-Cu(s.s), and soft β-Cu(s.s) increased shear strength. A Cu-Zn filler was used for the induction brazing of WC-11Co cemented carbide and AISI 4140 alloy steel. To enhance the shear performance of the brazed interface, a new electromagnetic coupled cryogenic treatment was proposed. Results show that the shear strength of the treated interface increased by 35.2%, and that the fracture surface exhibited more ductile fracture characteristics. The distinct microstructure after treatment was from precipitation of the soft β-Cu(s.s), and the grain refinement and dendritic structure were from α-Cu(s.s). The relaxation of residual tensile stress on the WC-11Co side also enhanced the shear strength.

Jointing of CFRP/5083 Aluminum Alloy by Induction Brazing: Processing, Connecting Mechanism, and Fatigue Performance

Carbon fiber reinforced polymer (CFRP) is widely used in the lightweight design of high-speed trains due to its high specific strength. In order to further reduce the weight of the high-speed train body, it is necessary to study the joining process and fatigue properties of CFRP/aluminum alloys (CFRP/Al) structure. In this work, the CFRP plate and 5083P-O aluminum plate were successfully connected by an induction brazing method. The optimum parameters of induction brazing were determined to be an induction temperature of 290 °C, a normal pressure of 200 kPa, and a holding time of 5 s. After the 5083 plate was pre-anodized, the tensile strength of the CFRP/5083 joint reached a maximum value of 176.5 MPa. The anodization process introduced more surface micro-structures on the 5083 plate, leading to a better wetting behavior between CFRP and oxide film. Meanwhile, a new chemical bond, Al-O-C, was also formed at the interface of the CFRP/5083 joint. The fatigue limit of the CFRP/5083 joint was calculated to be 71.68 MPa through high-cycle fatigue (HCF) testing. The fatigue cracks initiated from the interface of CFRP/oxide film, and then propagated to base metal. Finally, the oxide film was peeled off from the base metal under shear stress, which contributed to the fracture of the CFRP/5083 joint. The bonding strength between CFRP and 5083 aluminum alloy is far from the conventional welded joints. Therefore, feasible approaches should be proposed to obtain a more robust bonding between CFRP and aluminum alloy in the future.

Microstructure and damping property of Mn-Cu damping alloy by induction brazing and different heat treating

Mn-Cu damping alloy using in complex structural applications often experiences different thermal cycles, so the changes in the microstructure and damping properties of Mn-Cu damping alloys become a focus of attention. In this study, high frequency induction heating technique was used to prepare three-layer Mn-Cu damping structure. The microstructure and damping properties of the composite structure under different heat treatment processes and different heat treatment sequences were analyzed. The experimental results show that the composite Mn-Cu damping structure has good bonding interface and higher shear strength. After solid solution + brazing + aging, the Mn-Cu damping alloy has excellent damping properties for the formation of fine twins and about 10 μm brazing layer. In addition, with the increase of aging temperature and aging time, the quantity of twins becomes less, and α-Mn forms, which leads to the decrease of damping property. The interface between diffusion layer and brazing layer contributes to the improvement of damping properties. The specimen has the best damping property and thermal stability with the process of 900 ℃ × 1 h solid solution + brazing + 435 ℃ × 8 h aging treatment.

Structure design and experimental study on ultrasonic vibration–assisted induction brazing cubic boron nitride abrasive tools

Brazed superabrasive tool has been widely used in machining of difficult-to-cut materials to improve the machining efficiency and quality. However, the severe wear and associated short service life have to be faced for conventional induction brazed (CIB) abrasive tools during machining processes, owing to its weak bonding strength between abrasive grains and metal-bonded phases. In this case, the method of ultrasonic vibration–assisted induction brazing (UVAIB) was proposed to fabricate tools, through introducing ultrasonic vibration into brazing process to improve the abrasive bonding strength. Here, a novel UVAIB device was developed, and the geometric designation parameters were optimized using a finite element simulating method. In addition, the performance of UVAIB device was tested in terms of the impedance and amplitude. Subsequently, the comparative experiment trials were performed with the brazed abrasive tools under the CIB and UVAIB method. Results show that the ultrasonic energy loss of UVAIB device can be reduced, and then, the amplification value and vibration uniformity reach 8 and 92%, respectively. In addition, a large number of pores and macro-cracks inside tool’s metallic matrix for CIB can be observed, whereas the number of pores is reduced by 75%, and only fewer and smaller micro-cracks are found for UVAIB. Furthermore, compared with the grains’ intergranular fracture for CIB, UVAIB exhibits the transgranular fracture mode due to its higher bonding strength after adopting the ultrasonic vibrating method.

The microstructure and wear properties of diamond composite coatings on TC4 made by induction brazing

In this work, diamond and diamond/graphite composite coatings were obtained on the surfaces of TC4 (Ti-6Al-4V) alloy by high-frequency induction heating the preplaced powders in argon. The microstructures of the composite coatings were studied by scanning electron microscope, energy dispersive spectrometer and X-ray diffractometer, and the wear resistance of coatings was assessed by rubber wheel abrasion test. The results showed that the composite coatings had good metallurgical bonding with the substrates. TiC and ZrC particles in-situ generated in diamond/graphite composite coating improved the wear resistance of alloy matrix, but the free graphite weakened the wear-resistant structure of the coating. In the wear tests, abrasive wear was the main wear mechanism for diamond composite coating and diamond/graphite composite coating. Beside the elements of brazing alloy, carbon, aluminum and oxygen were the main elements detected at the surfaces of the two coatings.

Analysis of approaches for creating pipe connections in oil and gas equipment

The article deals with the problem of connecting pipelines in the oil and gas industry. One of the connection methods is resistance welding. Often, the use of this approach shows muted efficiency as it depends on the qualifications of the welder. A technique for creating flange (plane) connections with a pipe in the oil and gas industry is considered. The necessary equipment and types of welds within the considered area are considered. Thus, it is necessary to conduct a literature-patent review to find an alternative method for creating welded joints in oil and gas pipelines in order to increase the reliability of such joints and reduce the cost of production. The analysis of the subject area and the search for possible solutions to the problem posed were carried out. Various welding methods (manual electric arc, automatic submerged-arc welding, induction brazing, etc.) are considered and a comparison of the main welding methods is given, as well as the rationale for the use of electron beam welding to create such pipe joints.