Induction Brazing Process Research Articles

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.

Algorithms for selecting the operating mode of the technological process of waveguide paths induction brazing

The article presents the development of a method for selecting the operating mode of the induction brazing process based on intelligent methods. The use of intelligent methods is due to the presence of uncertain conditions caused by the complexity of the initial setting of the technological parameters of the induction brazing process, the error of measuring instruments, and the human factor. The use of smart methods will make it possible to reduce the impact of negative factors, remove uncertainty, and adequately perform the initial set of technological parameters for the induction brazing process. Artificial neural networks, the fuzzy controller and the neural fuzzy controller have been chosen as the smart methods in this work. The article gives a brief overview of the above methods, provides a rationale for the choice of intelligent methods, and also compares their effectiveness. Based on the results of the experimental efficiency check, the most suitable method for determining the choice of induction brazing process operation is proposed.

Constant current induction brazing process optimization of AgCdO15-Cu electrical contact

The current waveform of the heating phase, the holding current and holding time of the holding phase were optimized in this study to solve the problems of low brazing ratio and poor quality stability of constant current induction brazing. Pulse current was used to replace constant current in the heating phase to improve the uniformity of the radial temperature distribution of electrical contact. The simulation results showed that the uniformity of the radial temperature field of pulse current heating is better than constant current heating. The experiment was conducted with constant and pulse induction brazing separately. Compared with constant current induction brazing, pulsed current induction brazing has a higher brazing ratio and a wider process window for brazing time. The maximum brazing ratio of constant induction brazing is 87.62 %, and pulse induction brazing is 96.61 %. Besides, the shear strength of brazing joint can be improved by extending hold time. Different from the effect of holding time, the shear strength increases first and then decreases with the increase of holding current, and it should be selected according to the actual situation.

Comparison of simplified techniques for solving selected coupled electroheat problems

Purpose The purpose of this paper is to compare different reduced-order models for models of control of induction brazing process. In the presented application, the problem is to reconstruct temperature at the points of interests (hot spots) from information measured at accessible places. Design/methodology/approach The paper describes the process of induction brazing. It presents the full field model and evaluates the possibilities for obtaining reduced models for temperature estimation. The primary attention is paid to the model based on proper orthogonal decomposition (POD). Findings The paper shows that for the given application, it is possible to find low-order estimator. In the examined linear case, the best estimator was created using POD reduced model together with the linear Kalman filter. Research limitations/implications The authors are aware of two main limitations of the presented study: material properties are considered linear, which is not a completely realistic assumption. However, if strong coupling and nonlinear material parameters are considered, the model becomes unsolvable. The process and measurement uncertainties are not considered. Originality/value The paper deals with POD of multi-physics 3 D application of induction brazing. The paper compares 11 different methods for temperature estimator design.

Residual stresses of polycrystalline CBN abrasive grits brazed with a high-frequency induction heating technique

Residual stresses produced in polycrystalline CBN abrasive grits during a high-frequency induction brazing process are calculated by using finite element analysis, with a consideration of the nonuniform temperature distribution in the induction brazing model. The influences of induction brazing parameters on the residual stresses of polycrystalline CBN abrasive grits have been analyzed, including the embedding depth, grit side length, etc. Results obtained show that the tensile stress with a 40% embedding depth is 292 MPa, which is the minimum on the bonding interface compared with other embedding depths. Meanwhile, the maximum tensile stress is 575 MPa, with an increase of 59% compared with that of a grit side length of 50 mm. Finally, the simulation results of the brazing residual stress of polycrystalline CBN abrasive grits have been confirmed valid based on the residual stress measurement of the brazed monocrystalline CBN grit.

Investigation on heating temperature characteristics during rotating induction brazing of monolayer CBN grinding wheels: Numerical simulation and experimental verification

This article mainly carries out the numerical simulation and experimental verification of heating temperature characteristics during fabrication of monolayer brazed cubic boron nitride (CBN) grinding wheels using the rotating induction brazing technique. Effects of the critical heating factors in t he rotating induction brazing process, such as induction current, current frequency, heating gap and scanning speed are analyzed, respectively. It was found that, the maximum value of heating temperature increases nonlinearly with the increasing induction current and current frequency, and with decreasing of the heating gap and scanning speed. The empirical formula of heating temperature is established, and the rotating induction heating parameters are accordingly optimized to control the brazing temperature range of 880-940°C, which has been confirmed valid during the rotating induction brazing operation of monolayer CBN grinding wheels.

Induction brazing BaCo0.7Fe0.2Nb0.1O3-δ membrane tubes to steel supports with Ag-based filler in air

An induction brazing process has been developed to seal BaCo0.7Fe0.2Nb0.1O3-δ (BCFN) membrane tubes to metal supports using Ag-Cu alloy in air. The closed-one-end BCFN membrane tubes with an outer diameter of 16mm and a length of 560mm were prepared by slip casting. The thermal expansion behaviors of the BCFNO membrane, Ag braze and 310S stainless steel were characterized. A sleeve joint was optimized to reduce the stresses caused by the mismatching in thermal expansions. Ag-1mol%Cu braze was chosen as brazing filler duo to its good wettability for both the membranes and the metal substrates and thin and continuous reaction layers. Based on the characteristics of the BCFN membrane, a temperature schedule was exploited to successfully achieve the induction brazing of the BCFN membrane tubes to the 310S supports using Ag-1mol%Cu in air. The entire time needed is about 80min. The brazed assemble subjected to 15 thermal cycles still exhibits no degradation in joint hermeticity and stable oxygen permeation flux. The result indicates that induction brazing can efficiently join large membrane tubes with high thermal expansion to their metal supports.

In situ synthesis of high strength Ag brazing filler metals during induction brazing process

In this study, a high Zn content AgCuZn alloy with poor forming property is in-situ synthesized using AgCu/ZnCu/AgCu sandwich sheet during the induction brazing process. The results reveal that the AgCu and ZnCu alloys can fuse comprehensively after they melt and been held for a short time, forming a brazing seam with uniform composition and superior metallurgical bonding with the 316LN substrate. The strength of the obtained brazed joints is much higher than the joints brazed using common AgCuZn alloy.

Mechanical and microstructural analysis of ultrasonically assisted induction-brazed TiAl6V4 joints

This paper focuses on the process of ultrasonically assisted induction brazing with regard to titanium brazing. The titanium alloy TiAl6V4 was brazed using an aluminum-based filler alloy (AlMg2.5Cr0.3). It was apparent that the layer thickness of the brazing foil as well as the brazing temperature and the intensity of the ultrasound are significant influencing factors of the combined brazing process and microstructure. It is the aim of this paper to draw conclusions from the microstructural and mechanical investigations of the brazed joint about the process parameters, which are crucial for the properties and quality of the joint. The evaluation of the microstructure of the joint was conducted by means of metallographic investigations and results obtained by means of scanning electron microscopy. Besides mechanical microhardness measurements, strength investigations were conducted in order to evaluate the quality of the joint. Furthermore, the results of conventional vacuum brazing processes were correlated in order to be able to better facilitate and understand the adapted induction brazing process.

Development of laser welded appendages to Zircaloy-4 fuel tubing (sheath/cladding)

Laser welding is a potential alternative to the induction brazing process commonly used for appendage attachment in CANDU® fuel fabrication that uses toxic Be as a filler metal, and creates multiple large heat affected zones in the sheath. For this work, several appendages were laser welded to tubing using different laser heat input settings and then examined with a variety of techniques: visual examination, metallography, shear strength testing, impact testing, and fracture surface analysis. Where possible, the examination results are contrasted against production induction brazed joints. The work to date looks promising for laser welded appendages. Further work on joint optimization, corrosion testing, irradiation testing, and post-irradiation examination will be performed in the future.

Numerical simulation and optimization of WC-SS420 induction brazing process

Tungsten carbide (WC) is a very hard, brittle, and relatively expensive cermet. It is often joined to more economical material, such as martensitic 420 stainless steel (SS420), to form a hybrid cutting tool stock. This article summarizes a study on the optimization of an induction brazing process joining these two materials using BAg-22 as filler metal. This study uses an integrated approach consisting of finite element analysis (FEA) modeling and experimental verifications. The thermal behaviors and the metallurgical transitions during the brazing cycles of WC-BAg22-SS420 joints are studied. This study investigated process and metallurgical issues due to mismatches in thermal expansion coefficient, thermal conductivity, and electromagnetic permeability. Using the optimum process parameters derived from simulation, joint strengths exceeding 370 ± 40 MPa for shear were obtained. The hardness of WC was unaffected by the brazing heat. However, softening in the SS420 next to the fusion interface was constantly observed in the experiments. The FEA modeling results demonstrated that using a controlled heating and cooling process schedule was effective in mitigating this softening phenomenon. Experimental verification of this mitigation method is currently under study.

Study on Soft Zone of Type 420 Stainless Steel Weldment during the Induction Brazing Process

Tungsten carbide (WC) is often induction welded to tougher and economical material, such as martensitic type 420 stainless steels (SS 420), to form a hybrid cutting tool stock. However, undesired softening in the SS 420 next to the fusion interface usually occurs. This softening is due to localized carbide precipitation in SS 420 matrix arising from heating during the induction brazing process. The aim of the present work is to investigate the soft zone of the SS 420 weldment by controlling the heat input during induction brazing. The result showed that cooling rate has a great effect on softening of the SS 420 weldment during induction brazing.

Development of Anode-Supported Flat-Tube Solid Oxide Fuel Cell (SOFC) Stack with High Power Density

An anode-supported flat tubular SOFC stack for intermediate temperature (700~800oC) operation was fabricated and operated in this study. For this purpose, we fabricated anode-supported flat tubular cells by optimization of the current collecting method and the induction brazing process. After that, we designed a compact fuel and air manifold by adopting a simulation technique to uniformly supply fuel and air gas into the stack and a unique seal and insulation method to make a more compact stack. To assemble the stack, the prepared anode-supported flat tubular cells with an effective electrode area of 90 cm2 were connected in series to 30 bundles, in which one unit bundle consists of two flat tubular cells connected in parallel. The performance of the stack in 3 % humidified H2 and air at 750oC showed a maximum electrical power of 921 W.

Fabrication and operation of a 1 kW class anode-supported flat tubular SOFC stack

A 1 kW class anode-supported flat tubular SOFC stack for intermediate temperature (700–800 °C) operation was fabricated and operated in this study. For this purpose, we fabricated anode-supported flat tubular cells by optimization of the current collecting method and the induction brazing process. After that, we designed a compact fuel and air manifold by adopting a simulation technique to uniformly supply fuel and air gas into the stack and a unique seal and insulation method to make a more compact stack. To assemble the stack, the prepared anode-supported flat tubular cells with an effective electrode area of 90 cm 2 were connected in series to 30 bundles, in which one unit bundle consists of two flat tubular cells connected in parallel. The performance of the stack in 3% humidified H 2 and air at 750 °C showed a maximum electrical power of 921 W (fuel utilization ratio = 25.2%).

Induction brazing for gas sealing of anode-supported tubular solid oxide fuel cells using the nickel based brazing alloy modified by TiH 2

The nickel based brazing alloys (BNi 2, BNi 4) modified by reactive TiH 2 have been studied for their gas sealing properties of anode-supported tubular SOFCs to ferritic stainless steel by induction brazing process. BNi 2 and BNi 4 are not wetted on YSZ electrolyte, but the brazing alloy with TiH 2 showed good wettability with YSZ electrolytes due to a formation of TiO x layer. Among the tested brazing alloys (BNi 2, BNi 4, modified BNi 2, modified BNi 4), all except modified BNi 4 did not join with YSZ. The modified BNi 4 showed the lowest gas leak rate. The gas tightness of a brazed cell was confirmed by open circuit voltage, which was nearly the same as a theoretical value. Based on these experimental results, it is concluded that the BNi 4 modified by TiH 2 is suitable as a sealing material in SOFCs operating at 750 °C.

Induction Brazing for Gas Sealing and Joint Properties of Anode Supported Solid Oxide Fuel Cells

The nickel based brazing alloys (BNi 2, BNi 4) modified by reactive TiH2 have been studied for gas sealing properties of anode-supported tubular SOFCs to ferritic stainless steel by induction brazing process. BNi 2 and BNi 4 is not wetted in YSZ electrolyte, but the brazing alloy with added TiH2 showed good wettability with YSZ electrolyte due to formation of TiOx layer which has lower interfacial energy () than interfacial energy of Ni and YSZ. Among the tested brazing alloys (BNi 2, BNi 4, modified BNi 2, modified BNi 4), the others except for modified BNi 4 were not joined with YSZ. The modified BNi 4 showed the average value of 19 MPa and also the lowest gas leak rate of 8.0 × 10-7 L•cm-2sec-1 at pressure difference of 3 atm measured with He gas.

Joining of Metallic Cap and Anode-Supported Tubular Solid Oxide Fuel Cell by Induction Brazing Process

The anode-supported tubular solid oxide fuel cells were fabricated and joined onto the metal cap (SUS430) for current collecting and sealing by using the induction brazing process. Among five filler materials used in the induction brazing, Ni-based BNi2 has shown the lowest gas permeability of 1×10−6 l cm−2 s−1 at a differential pressure of 3 atm measured with He gas. The electrical conductivity of anode support brazed with BNi2 showed 450 S cm−1 at 750°C and stable value even at the long-term and thermal cycle tests. The brazed anode-supported tubular cell at operating temperature of 750°C produced 210 mW/cm2 at 0.7 V. The gas-tightness was confirmed by open circuit voltage (OCV) value similar to theoretical value. The cell showed a stable performance and OCV for 200 h.

연료극 지지체식 평관형 고체산화물 연료전지 단위 번들의 제조 및 성능

한국에너지기술연구원에서는 중온 (<TEX>$700{\sim}800^{\circ}C$</TEX>) 작동용 연료극 지지체 평관형 SOFC 스택을 구성하는 단위 번들을 개발했다. 연료극 지지체 평관형 셀은 Ni/YSZ 서밋 연료극 지지체 튜브, 8몰% <TEX>$Y_2O_3$</TEX> stabilized <TEX>$ZrO_2$</TEX> (YSZ) 전해질, <TEX>$LaSrMnO_3$</TEX> (LSM)과 LSM-YSZ composite 및 <TEX>$LaSrCoFeO_3(LSCF)$</TEX>로 구성된 다중층 공기극으로 구성됐다. 제조된 연료극지지체 평관형 셀은 유도 브레이징 법에 의해 페리틱 (ferritic) 금속 캡에 접합됐고, 공기극의 전류집전을 위해 공기극 외부에 Ag 선 및 <TEX>$La_{0.6}Sr_{0.4}CoO_3(LSCo)$</TEX> paste를 이용했으며, 연료극의 전류집전은 Ni felt, wire, 그리고 paste를 이용했다. 단위 번들을 만들기 위한 연료극 지지체 평관형 셀의 반응 면적은 셀 당 <TEX>$90\;cm^2$</TEX> 이었으며, 2개의 셀이 병렬로 연결되어 1개의 단위 번들이 됐고, 총 12개의 단위 번들이 직렬로 연결되어 스택을 구성한다. 공기 및 3%의 가습된 수소를 산화제 및 연료로 사용한 단위 번들의 운전 결과 최대 성능은 <TEX>$800^{\circ}C$</TEX>에서 <TEX>$0.39\;W/cm^2$</TEX>의 출력이 나타났다. 본 연구를 통해 연료극 지지체 평관형 SOFC 셀의 기본 기술과 KIER 만의 독특한 연료극 지지체 평관형 SOFC 스택을 구성하는 단위 번들의 개념을 확립할 수 있었다. KIER has been developing the anode-supported flat tubular solid oxide fuel cell unit bundle for the intermediate temperature(<TEX>$700{\sim}800^{\circ}C$</TEX>) operation. Anode-supported flat tubular cells have Ni/YSZ cermet anode support, 8 moi.% <TEX>$Y_2O_3$</TEX> stabilized <TEX>$ZrO_2(YSZ)$</TEX> thin electrolyte, and cathode multi-layer composed of Sr-doped <TEX>$LaSrMnO_3(LSM)$</TEX>, LSM-YSZ composite, and <TEX>$LaSrCoFeO_3(LSCF)$</TEX>. The prepared anode-supported flat tubular cell was joined with ferritic stainless steel cap by induction brazing process. Current collection for the cathode was achieved by winding Ag wire and <TEX>$La_{0.6}Sr_{0.4}CoO_3(LSCo)$</TEX> paste, while current collection for the anode was achieved by using Ni wire and felt. For making stack, the prepared anode-supported flat tubular cells with effective electrode area of <TEX>$90\;cm^2$</TEX> connected in series with 12 unit bundles, in which unit bundle consists of two cells connected in parallel. The performance of unit bundle in 3% humidified <TEX>$H_2$</TEX> and air at <TEX>$800^{\circ}C$</TEX> shows maximum power density of <TEX>$0.39\;W/cm^2$</TEX> (@ 0.7V). Through these experiments, we obtained basic technology of the anode-supported flat tubular cell and established the proprietary concept of the anode-supported flat tubular cell unit bundle.

Operating Characteristics of Advanced 500W Class Anode-supported Flat Tubular SOFC stack in KIER

KIER has been developing the anode supported flat tubular SOFC stack for the intermediate temperature (700~800oC) operation. For this purpose, we have first fabricated anode supported flat tubular cells by the optimization between the current collecting method and the induction brazing process. After that we designed the compact fuel & air manifold by adopting the simulation technique to uniformly supply fuel & air gas and the unique seal & insulation method to make the more compact stack. For making stack, the prepared anode-supported flat tubular cells with effective electrode area of 90 cm2 connected in series with 12 modules, in which one module consists of two cells connected in parallel. The performance of stack in 3 % humidified H2 and air at 800 oC shows maximum power of 507 W. Through these experiments, we obtained basic & advanced technology of the anode-supported flat tubular cell and established the proprietary concept of the anode-supported flat tubular SOFC stack in KIER

Application of cast gamma TiAl for automobiles

Studies of cast gamma TiAl applied for engine valves and turbocharger confirmed excellent performances. The durability of TiAl valves was also proven. Two cast gamma TiAl alloys were developed for the engine valves and the turbine wheels of turbochargers. New precision casting process of LEVICAST and induction brazing process of the gamma TiAl and alloy steels were proposed as advanced processing technologies.