Silver Brazing Research Articles

Research on the physical properties and film removal mechanism of silver brazing flux by micro morphology analysis and X-Ray Diffraction

The effect of KHF2 addition on silver brazing flux was studied in this paper. Results showed that the melting temperature of brazing flux would sustainably decrease with the increasing content of KHF2. KF could not be completely replaced by KHF2 in the brazing flux because it could restrain excessive spreadability, which was resulted from KHF2. F element in the flux replaced O element to form Fe2F5.

Optimization for Reduction in Defects of Brazing of Shock Loop Tube to Resonator

Abstract: Rejection Y variable shows the rejection percentage and optimization phase done with the help of Minitab software. Various design parameters have been selected to identify for the optimization like heating time, the weight of silver brazing wire, and power rating of the equipment extra. Improve phase revealed that the Weight 0.311 Gms, Heating time 11 Sec, Power rating 5 KW is good in the better condition as compared with the current condition. In the end, the conclusion shows that the bulk supplies of 0.3mm silver ring received and started in the production line and the work standard has been established. By doing daily routine activity checks, after one month there is a drop in the rejection and the cost regarding this has also been achieved. Keywords: Reduction in Defects of Brazing, Shock Loop Tube, Resonator, DMAIC approach, Resonator Optimization

Complementary methods for characterization of the corrosion products on the surface of Ag60Cu26Zn14 and Ag58.5Cu31.5Pd10 brazing alloys

AbstractCorrosion products formed on the surface of two silver brazing alloys after the potentiostatic polarization in 3.5% sodium chloride solution were characterized by the standard methods such as, the X-ray diffraction, micro-Raman spectroscopy, and scanning electron microscopy with energy-dispersive spectroscopy. This paper presents the results of a laser desorption/ionization mass spectrometry (LDI MS) analysis as a new approach to the characterization of corrosion products. The potential of the anodic polarization was 0.5 V versus saturated calomel electrode, and the process duration was 300 s. The corrosion layers on both investigated alloys were similar in composition with cuprous chloride and silver chloride as the main components and had strong indications of cuprous oxide formation. The major difference between these two layers was the existence of zinc hydroxychloride as the corrosion product of Ag-Cu-Zn alloy. Palladium compounds were not found in the case of Ag-Cu-Pd alloy. The results of different methods have shown a good consistency. Complementarity between the used methods was useful in the interpretation of the results for each used method. This study has demonstrated that LDI MS can be used as an efficient additional method together with the traditional ones.

Clip-brazing for the design and fabrication of micronewton-resolution millimeter-scale force sensors

We present clip-brazing as a new method to construct millimeter-to-centimeter-scale metal structures with micron-scale precision that is fast, scalable and extremely low-cost. Small structures with demanding requirements on both dimensional tolerances and dynamic force responses to time-varying loads are difficult to fabricate and expensive to iteratively prototype. The technique introduced here enables precise placement of strong metallic brazed bonds to create 3D structures with micrometric accuracy, which in this work is exemplified through the design and construction of a broadband micronewton-resolution force-sensing device. The fabrication method uses tensioned clips made from a silver brazing alloy wire to accurately place and control the volume of the metal that joins and supports the pieces that compose the micro-structures. The use of clips also allows the simultaneous fusion of all the connections in the structure during a single heating sequence, reducing tolerance stack-up. To analyze the quality and strength of the brazes, we employed scanning electron microscopy (SEM) on cross-sections and tensile testing on dogbone-shaped sample pieces, respectively. After proper calibration, the functionality of the constructed micro-force-sensing system was analyzed and demonstrated using constant a priori known weights and the vertical periodic forces produced by an 83 mg flapping-wing microrobot (including a 3 mg attachment truss). The static tests, in combination with solid-mechanics analyses and simulations based on finite-element analysis (FEA), provide compelling evidence of the high accuracy and precision of the force sensing system for frequencies below 167.5 Hz. Furthermore, the shape characteristics and average values of the measured periodic signals are compared to computational fluid dynamics (CFD) simulations and validated for two sets of flapping angles across the frequency range from 55 to 100 Hz. These results validate the proposed approach as a viable tool for microrobotic design and fabrication.

Magnetohydrodynamics approach for active decay heat removal system in future generation IV reactor

In this work, a helical-type magnetohydrodynamics transportation system for active decay-heat-removal system in a prototype fourth-generation sodium fast reactor was numerically analysed considering operational conditions of atmospheric pressure, for liquid sodium transportation in a loop. The prototype fourth-generation sodium fast reactor is a reactor with high uranium utilisation and an electric power output of 150 MWe, subjected to a developed pressure of 10 kPa and flowrate of 0.005 m3/s under a temperature condition of 468.75 K for the active decay-heat-removal system. A helical-type magnetohydrodynamics transportation system was used to develop pressure in such a loop to reduce the current compared with that in a rectangular-type one; this could overcome the principal limitation of the requirement of a high current in a magnetohydrodynamics transportation system. The main parameters of the considered helical-type magnetohydrodynamics transportation system were the inner diameter, silver brazing, number of turns, and radius of pump, which affect the current, magnetic-flux density, and its velocity. The parameters were analysed in relation to the minimisation of the pump current while maximising the pressure. The specifications of the optimised helical-type magnetohydrodynamics transportation system—current of 352 A and magnetic-flux density of 0.466 T—were derived to satisfy the conditions of the active decay-heat-removal system.

Study on a novel Sn-electroplated silver brazing filler metal

Novel Sn-electroplated Ag brazing filler metal with a high tin content was prepared by combining the plating and thermal diffusion method. The BAg45CuZn alloy was used as a base filler metal, and a Sn layer was electroplated on it. Then the H62 brass was brazed with the Sn-plated brazing filler metal containing 6.2 wt% of Sn. The results showed that the microstructure of the brazed joints with the Sn-plated filler mainly consisted of the Ag phase, Cu phase, CuZn phase and Cu5Zn8 phase. The tensile strength of the joints brazed with the Sn-plated filler metal was 326 MPa, which was higher than that of the joints with the base filler metal. Fracture analysis showed that the fractures of the joints brazed by the Sn-plated filler metal was mainly ductile fracture mixed with a small quantity of brittle fracture.

Reactive-Element-Free, Silver-Based Brazes for SOFC Applications

The current go-to braze for SOFC applications is the Ag-CuO reactive air braze (RAB). As with other RAB brazes, the ability to use this braze with ceramic materials (such as yttria stabilized zirconia (YSZ) and oxide-protected stainless steel (SS)) is enabled by a braze component (in this case Cu) reacting with the brazing atmosphere to form a surface oxide that facilitates wetting. [1-3]. Although Ag-CuO provides an easy way to join YSZ and SS for SOFC applications, the insufficient ~45° wetting angle of the conventional Ag-4 wt.% Cu braze [1, 2] often leads to braze joint manufacturing defects (Type I pores). Further, the reduction of CuO during dual atmosphere (H2/O2) SOFC operation results in porosity (Type II pores) that: i) mechanically weaken the braze/SS and braze/YSZ interfaces and ii) facilitates H2invasion into the center of the braze, which in turn, hastens the development of gaseous water pockets within the braze (Type III pores) caused by dissolved oxygen and hydrogen meeting. This poster will present a new method for silver brazing YSZ and SS without the need for reactive air elements. As shown in Figure 1, this procedure (which is performed under SOFC electrode compatible oxygen partial pressures ≥ 1x10-10atm) produces a braze that wets both the YSZ and SS. In addition, this procedure also produces Ag-YSZ bonding which has been shown by Kuhn et. al [4] to have a fracture energy two times higher than conventional Ag-CuO braze joints. It is expected that the elimination of Type I and Type II pores enabled by this new brazing method will increase SOFC braze joint lifetimes.

Brazing of Titanium with Aluminium Alloys

Abstract This study presents results of vacuum diffusion brazing of Grade 2 titanium with 6082 (AlMg1Si0.6Cu0.3) aluminium alloy using B-Ag72Cu-780 (Ag72Cu28) grade silver brazing metal as an interlayer. Brazed joints underwent shear tests, light-microscopy-based metallographic examinations and structural examinations using scanning electron microscopy (SEM) and X-ray energy dispersive spectrometry (EDS). The highest quality and shear strength of 20 MPa was characteristic of joints brazed at 530°C with a 30-minute hold. The structural examinations revealed that in diffusion zone near the boundary with titanium the braze contained solid solutions based on hard and brittle Ti-Al type intermetallic phases determining the strength of the joints.

ПАЙКА БЕРИЛЛИЕВОГО ОКНА В МЕДНУЮ РАМУ СЕРЕБРЯНЫМ ПРИПОЕМ

ПАЙКА БЕРИЛЛИЕВОГО ОКНА В МЕДНУЮ РАМУ СЕРЕБРЯНЫМ ПРИПОЕМ

Pool boiling with high heat flux enabled by a porous artery structure

A porous artery structure utilizing the concept of “phase separation and modulation” is proposed to enhance the critical heat flux of pool boiling. A series of experiments were conducted on a range of test articles in which multiple rectangular arteries were machined directly into the top surface of a 10.0 mm diameter copper rod. The arteries were then covered by a 2.0 mm thickness microporous copper plate through silver brazing. The pool wall was fabricated from transparent Pyrex glass to allow a visualization study, and water was used as the working fluid. Experimental results confirmed that the porous artery structure provided individual flow paths for the liquid supply and vapor venting, and avoided the detrimental effects of the liquid/vapor counter flow. As a result, a maximum heat flux of 610 W/cm2 over a heating area of 0.78 cm2 was achieved with no indication of dryout, prior to reaching the heater design temperature limit. Following the experimental tests, the mechanisms responsible for the boiling critical heat flux and performance enhancement of the porous artery structure were analyzed.

2D Finite Element Computer Analysis of Strength for Brazed Joint of Cemented Carbide and Silver Brazing Filler Metal

2D Finite Element Computer Analysis of Strength for Brazed Joint of Cemented Carbide and Silver Brazing Filler Metal

Crack repair welding by CMT brazing using low melting point filler wire for long-term used steam turbine cases of Cr-Mo-V cast steels

Surface melting by gas tungsten arc (GTA) welding and overlaying by cold metal transfer (CMT) brazing using low melting point filler wire were investigated to develop a repair process for cracks in worn cast steel of steam turbine cases. Cr-Mo-V cast steel, operated for 188,500h at 566°C, was used as the base material. Silver and gold brazing filler wires were used as overlaying materials to decrease the heat input into the base metal and the peak temperature during the welding thermal cycle. Microstructural analysis revealed that the worn cast steel test samples contained ferrite phases with intragranular precipitates of Cr7C3, Mo2C, and CrSi2 and grain boundary precipitates of Cr23C6 and Mo2C.CMT brazing using low melting point filler wire was found to decrease the heat input and peak temperature during the thermal cycle of the process compared with those during GTA surface melting. Thus, the process helped to inhibit the formation of hardened phases such as intermetallics and martensite in the heat affected zone (HAZ). Additionally, in the case of CMT brazing using BAg-8, the change in the hardness of the HAZ was negligible even though other processes such as GTA surface melting cause significant changes. The creep-fatigue properties of weldments produced by CMT brazing with BAg-8 were the highest, and nearly the same as those of the base metal owing to the prevention of hardened phase formation. The number of fracture cycles using GTA surface melting and CMT brazing with BAu-4 was also quite small.Therefore, CMT brazing using low melting point filler wire such as BAg-8 is a promising candidate method for repairing steam turbine cases. However, it is necessary to take alloy segregation during turbine operation into account to design a suitable filler wire for practical use.

Research in the Field of Manufacturing of Layered Brazing Materials

The results of research into manufacturing of layered brazing materials with silver brazing alloy BAg22 content and copper obtained in pressing at elevated temperature and rolling process for use in cutting tools working in harsh conditions were presented. Mechanical and dimensional properties of the constituent materials of the layered strips with 50 and 75% volume fraction of copper as the inner layer were selected, i.e. the BAg22 alloy strip and the copper strip, for the preliminary join operation in pressing process. Cladding process conditions of the set BAg22/Cu/BAg22 of the original thickness of 32mm for the ratio of layer thicknesses as 1:2:1 and 24mm of the original thickness for the ratio of layer thicknesses as 1:6:1 including the method of semi products surface preparation and range of forces and temperature parameters were specified. Plastic working conditions of pressed composite ingot in hot and cold rolling to the final thickness with the intermediate and final heat treatment parameters were developed.

Research and Preparation of Silver Free Amorphous Active Brazing Alloy

A silver free amorphous Cu-35Ti-12Ni active brazing alloy was successfully prepared in this work. The crystallinity, microstructure, and chemical composition were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive spectrometry (EDS), respectively. A typical characteristic peak of amorphous material was observed in the XRD pattern. The microstructures and chemical compositions of the silver free amorphous alloy were uniform. Differential scanning calorimetry (DSC) result shows that the amorphous silver free brazing alloy has higher melting temperature than commercial silver brazing alloy (Ag-26.5Cu-1.5Ti). Wetting contact angle and spreading area on Si3N4 ceramic substrate were used to evaluate the wetting ability of brazing alloy. The wetting angle was smaller than 5o, and the spreading area was 141.6 mm2 at 1100°C. The bending strength of silver free brazing alloy/Si3N4 was also carried out. The mechanical test shows that the amorphous Cu-35Ti-12Ni/Si3N4 has higher joint strength (304.7MPa) than the crystal Cu-35Ti-12Ni/Si3N4 (294.7MPa) at room temperature.

Brazeability and mechanical properties of Ag–Cu–Sn brazing filler metals on copper-brazed joint

This paper describes an investigation of cadmium-free silver brazing filler metals, the ternary Ag–Cu–Sn alloys. The influences of tin content on solidus and liquidus temperatures and gap filling ability of Ag–Cu–Sn alloys on copper were investigated. Microstructures of the joint and the shear strength were examined. Investigation on gap filling ability test procedure was performed according to ISO 5179-1983. The result from differential thermal analysis showed that the solidus and liquidus temperatures of the filler metals decreased with the increment of tin content in Ag–Cu–Sn. The results from the shear test showed that the brazed joint exhibited the highest strength at 10 wt-% tin content in the filler metal. The joint gaps of less than 0·10 mm were proposed when designing the brazed joint for Ag–Cu–Sn filler metals.

The Application of Vacuum Power for Drill Automatic Welding Device

In this paper, a vacuum suction cup robot is introduced, which is used in drill bolt welding machine to add silver brazing sheets. This paper briefly discusses the application of vacuum power on the device. Then through the selection of the degree of vacuum and a vacuum generator, the selection and calculation of the chuck size specify the design process of the vacuum power system. Finally, through the working process of the manipulator and the structural design of the silver brazing box briefly introduce the movement of the vacuum suction manipulator.

Model of the physical–chemical interaction of EP202 alloy with a copper–silver brazing alloy and the strength of the bond at the interface

A model of the interaction of a complexly alloyed alloy based on Ni–Cr with a copper–silver brazing alloy is developed and used for estimating the selective affinity of the individual elements of the alloy, in particular Ni, with the elements of the brazing alloy on the atomic level.

Impact of Tin and Nickel on the Brazing Properties of Silver Filler Metals and on the Strength of Brazed Joints Made of Stainless Steels

Abstract The research involved vacuum tests of brazing properties of silver filler metals, containing tin as well as tin and nickel, and used in brazing of chromium X6Cr17 and chromium-nickel X6CrNiTi18-10 stainless steels. The research also involved testing the strength and structural properties of brazed joints made of these steels. The tests were conducted on filler metals (silver brazing alloys) B-Ag68CuSn-730/755 (Ag68Cu28Sn4) and B-Ag65CuSnNi-740/767 (Ag65Cu28Sn5Ni2) and also, for comparative purposes, on the filler metal B-Ag72Cu-780 (Ag 272 according to PN-EN ISO 17672), most commonly applied in the vacuum brazing of high alloyed stainless steels. The brazing properties of the filler metals were tested by determining their wettability by means of the spreadability method. The strength of brazed joints made of the stainless steels was examined in a shear test. Research-related structural tests involved light and electron microscopy with an energy dispersive spectrometer (EDS). The comparative analysis of the properties of the filler metals revealed the positive impact of tin and nickel on the spreadability and wettability of the silver brazing alloys as well as on the quality and the shear strength of brazed joints.

First high-power model of the annular-ring coupled structure for use in the Japan Proton Accelerator Research Complex linac

A prototype cavity for the annular-ring coupled structure (ACS) for use in the Japan Proton Accelerator Research Complex (J-PARC) linac has been developed to confirm the feasibility of achieving the required performance. This prototype cavity is a buncher module, which includes ten accelerating cells in total. The ACS cavity is formed by the silver brazing of ACS half-cell pieces stacked in a vacuum furnace. The accelerating cell of the ACS is surrounded by a coupling cell. We, therefore, tuned the frequencies of the accelerating and coupling cells by an ultraprecision lathe before brazing, taking into account the frequency shift due to brazing. The prototype buncher module was successfully conditioned up to 600 kW, which corresponds to an accelerating field that is higher than the designed field of $4.1\text{ }\text{ }\mathrm{MV}/\mathrm{m}$ by 30%. We describe the frequency-tuning results for the prototype buncher module and its high-power conditioning.

Corrosion in Haas expanders with and without use of an antimicrobial agent: an in situ study

ObjectivesThe purpose of this study was to evaluate in situ the occurrence of corrosion in the soldering point areas between the wire, silver brazing and band in Haas expanders. Material and MethodsThirty-four 7-12-year-old patients who needed maxillary expansion with a Haas expander were randomly assigned to two groups of 17 individuals each, according to the oral hygiene protocol adopted during the orthodontic treatment: Group I (control), toothbrushing with a fluoride dentifrice and Group II (experimental), toothbrushing with the same dentifrice plus 0.12% chlorhexidine gluconate (Periogard®) mouthrinses twice a week. The appliances were removed after approximately 4 months. Fragments of the appliances containing a metallic band with a soldered wire were sectioned at random for examination by stereomicroscopy, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Data were analyzed statistically by Fisher's test at 5% significance level. ResultsThe analysis by optical microscopy revealed areas with color change suggestive of corrosion in the soldering point areas joining the band and the wire in all specimens of both groups, with no statistically significant difference between the groups (p=1). The peaks of chemical elements (Ni, Fe, Cr, O, C and P) revealed by EDS were also similar in both groups. Conclusion: Color changes and peaks of chemical elements suggestive of corrosion were observed in the soldering point areas between the wire, silver brazing and band in both control and experimental groups, which indicate that the 0.12% chlorhexidine gluconate mouthrinses did not influence the occurrence of corrosion in situ.