Silver Brazing Research Articles

Effects of Different Fluxes on the Spreadability of Zn-20Sn Solders

The spreadability of Zn-20Sn solders on Cu substrate was researched by using self-made flux, silver brazing 102 and medium activity rosin (RMA), and the characteristics of intermetallic compounds the appearance of solder joints were compared and analyzed at soldering joints. Results indicated that Zn-20Sn solders exhibited excellent spreadability by using self-made flux. A shoot IMC layer was closed to the solder while a flat IMC layer was presenting adjacent to the Cu substrate and the middle layer. Moreover, the characteristics of IMC and the appearances of soldered joints varied by using different fluxes.

Evaluation of heavy metal exposure in blood and urine of workers performing silver brazing

ObjectivesSilver brazing activities expose workers to metal fumes of which the health effects are not well studied yet. The aim of this study was to assess a number of biochemical...

Component analyses of silver brazing filler metals by inductively coupled plasma atomic emission spectrometry: a collaborative study for standardization

A collaborative determination of the major components of silver brazing filler metals (Ag–Cu–Zn–Cd, Ag–Cu–Zn–Ni, and Ag–Cu–Zn–Sn alloys) by inductively coupled plasma atomic emission spectrometry (ICP-AES) was conducted. The classical wet methods of gravimetry and titrimetry were also investigated for comparison, most of which are provided by Japanese Industrial Standards (JIS). Results of instrumental and classical analyses using a simple dissolution procedure with nitric acid showed excellent trueness and precision amongst all laboratories and for all alloys except those containing tin. The tin-containing alloy had to be dissolved, suppressing precipitation of the sparingly soluble hydrous tin(IV) oxide. Dissolution with mixtures of nitric and sulfuric acid gave the most satisfactory results without precipitation, thus enabling an accurate determination that favourably compared to the classical wet results. Finally we have evaluated the ICP-AES method and a hybrid method with gravimetry and ICP-AES according to the precision required, and found them to be suitable for standardization.

Investigation of gap filling ability of Ag–Cu–In brazing filler metals

In an attempt to develop cadmium-free silver brazing filler metals, the ternary Ag–Cu–In alloys were investigated. The effect of varying indium content on melting temperatures and brazeability of Ag–Cu–In alloys on copper was ascertained in this article. Additionally, microstructures, hardness, and shear strength of the brazed joints were investigated. Investigation of brazeability was carried out using a varying gap test piece method adapted from ISO 5179-1983. With this method, the capillary rise height at different joint gaps was used as a quantitative measure for brazeability. The results from differential thermal analysis showed that with the increase of indium content in Ag–Cu–In, the solidus and liquidus temperatures of the filler metals decreased. However, the increase of indium contents showed no significant improvement to the capillary rise height. The limits of capillary rise height of each filler metal corresponding to the joint gaps of 50 and 100 μm were approximately 45 and 28 mm, respectively. Increasing of indium content led to the increase of an intermetallic phase in the brazed layer which subsequently increased the joint hardness. However, this slightly reduced joint shear strength. The average shear strength of the joint brazed with 60Ag–15Cu–25In filler metal was about 11% lower than that brazed with 60Ag–35Cu–5In filler metal.

Eye protection practices and symptoms among welders in the Limpopo Province of South Africa+

Welding is associated with several ocular and systemic hazards especially where adequate protective measures are not taken. The purpose of this project was to study the eye protection practices and symptoms among welders in the Capricorn District of Limpopo Province, South Africa. Questionnaires designed to investigate eye protection practices and symptoms experienced were completed byone hundred and fifty (150) welders. The types of welding done were shielded metal arc (84%), oxyacetylene gas (4%) and silver brazing (12%). The number of years spent in the welding industry ranged from one to 10 years with a mean of 5 ± 3.1 years and the number of hours of welding per day ranged from one to 10 hours with a mean of 6 ± 2.1 hours. A large percentage of the welders (89%) reported wearing protective devices when welding and the most common protective devices used by the welders were: helmets (57%), goggles(22%), and face shields (15%). Six percent used inefficient protective devices such as sunglasses. Sixty one percent reported occasional exposure to welding flashes when not wearing any eye protection. Welding-related eye symptoms reported included foreign body sensation (18%), persistent after-images (31%), and watery eyes (50%). Al-though the majority of the welders wore protective devices while welding, a few did not always use such devices while others used sunglasses for protection. Moreover, many of the welders were occasionally, and only a few were always, exposed to welding flashes when protective devices were not used. Therefore, we concluded that eye protectionpractices amongst the welders appeared to be inadequate to avoid hazards associated with welding. It is recommended that an eye protection educational campaign for welders should form part of the SouthAfrican Government’s workplace safety program.

Development of JSNS target vessel diagnosis system using laser Doppler method

When an intense pulsed proton beam with a power of 1 MW is irradiated to a mercury target, a pressure wave caused by the proton beam gives a vibration on the target vessel. Pitting damage also occurs on the target vessel, especially incident beam area, resulting in shortening of a life-time. It is very important to monitor the vibration of the target vessel from the view point of the life-time estimation. We developed the target vessel diagnosis system using laser Doppler method and successfully installed it in an actual pulsed spallation source. The diagnosis system consists of retro-reflecting corner-cube mirror (reflective mirror) on the target, mirror assembly in a reflector plug and laser source-detector. The newly developed reflective mirror, made by nickel, was installed by vacuum silver brazing on the target vessel to detect the target vibration. In order to pass the laser beam to the target vessel, a mirror assembly was installed inside the reflector plug. It is replaceable using a remote handling machine during a maintenance period. Nd-YAG laser beam (wave length: 533 nm) with the power of 50 mW was adopted to detect the target vibration. The first proton beam to the target in the spallation neutron source (JSNS) was provided on 30 May 2008. The first signal related to the target vibration was also detected by using this target vessel diagnosis system.

Interfacial Microstructures and Bonding Strength between Aluminum Nitride and Silver Brazing Filler Metals Containing Various Active Elements

Effect of active element on interfacial microstructures and bonding strength of brazed AlN/AlN joints has been investigated and compared with the case of brazed Si3N4/Si3N4 joints. Brazing was carried out at 1173 to 1473 K for 3.6 ks in a vacuum using Ag-Cu filler metals containing Ti, Zr, V and Nb as an active element. The obtained joint had no defects such as un-bonded areas, regardless of active element and bonding temperature. Four kinds of active elements were divided into two groups by shear tests and microstructural observations. One was Ti and Zr, and the other was V and Nb. The bonding strength of the former was higher than that of the latter. In particular, the joint with Ti addition showed an excellent strength of about 200 MPa. Main fracture position in the joints with Ti and Zr additions was within the AlN, while most joints with V and Nb additions broke at the interface between the active filler metal and the AlN. In the former, TiN and ZrN layers consisting of fine grains were observed adjacent to the AlN. On the other hand, the joint with Nb addition had roundish grains of Nb2N in similar locations. It was considered that the existence of fine grains contributed to the enhancement of bonding strength due to the increase of contact area and to the formation of complicated interface. These tendencies were essentially consistent with those of the brazed Si3N4/Si3N4 joints.

Production of iron-disilicide thermoelectric devices and thermoelectric module by the slip casting method

FeSi 2 thermoelectric devices and thermoelectric modules were produced by the slip casting method, and their thermoelectric properties were evaluated. The starting materials were Fe 0.91Mn 0.09Si 2 ( p-type) and Fe 0.98Co 0.02Si 2 ( n-type). The powder concentration was 77 mass%, and the hydrogen exponents of p- and n-type were 8.5 and 7, respectively. The p- and n-type slips were simultaneously poured into a mold. The green body was demolded in approximately 10 min, then dried at 353 K for about 3 h in air. It was then sintered at 1443 K for 3 h, and annealed at 1123 K for 14 h. Both the sintering and annealing were performed in a vacuum of 10 −2 Pa. The p– n junctions were formed within the range of 10 mm from the edge of the hot junction. The electrode was formed by silver brazing. Reliable electrodes can be obtained by adding ε-phase powder or nickel powder. They formed ohmic contacts with β-FeSi 2. The open circuit voltage, the internal resistance and the maximum power output of the thermoelectric module consisting of 20 devices were 5.25 V, 15.2 Ω and 0.45 W, respectively, for the maximum temperature difference (=572 K).

ELKONITE 2110, 2150

Abstract ELKONITE 2110, 2150 tungsten-silver alloys are made by the press-sinter-repress method for attachment to backings by silver brazing. Tungsten has the highest strength and the highest melting temperature of the refractory metals. This is the principal factor in determining the resistance of a contact to arc erosion and mechanical wear. The strength, erosion, and weld resistance characteristics of the contact increase with increasing tungsten content; the electrical and thermal characteristics decrease. This datasheet provides information on composition and physical properties. Filing Code: W-24. Producer or source: CMW Inc.

グロー放電質量分析法による銀ろうおよびパラジウムろう分析

グロー放電質量分析法による銀ろうおよびパラジウムろう分析

Corrosion behaviour of silver brazing alloys in different environments

Corrosion data of the widely used silver brazing alloys (BAg‐1 and BAg‐3) of the American Welding Society’s (AWS) specification are scant in literature. Deals with the study of the corrosion behaviour of these alloys in different environments with particular emphasis on the industrial and marine atmospheres.

Mapping of the residual stress distribution in a brazed zirconia-iron joint

Neutron diffraction was used to study the residual strain (stress) distribution in a zirconia iron joint. The cylindrical specimen was obtained by brazing partially stabilized zirconia and cast iron disks sandwiched with a silver brazing alloy. The experimental data show that near the interface, the cast iron is mostly in tension while the zirconia is in compression, consistent with the thermal expansion mismatch between the two materials. At a given radius, the measured strains vary rapidly as a function of distance from the interface. Along the radial direction, however, the strains are almost constant over half of the radius. The experimentally determined residual strain distribution was compared with the results of a finite element analysis incorporating the effects of plastic deformation. The favorable agreement between the experimental data and the finite element calculations indicates that the residual stress distribution in brazed ceramic-metal joints can be reasonably understood within the framework of an elastic plastic finite element model.

An indigenous technology for a silver brazing alloy

This paper deals with the development of an indigenous technology for a widely used silver brazing alloy (BAg-1). Melting, alloying, casting and processing along with the heat treatment schedules, have been dealt with. Particular emphasis has been laid on the corrosion behaviour of this alloy.

Characteristics of an amorphous magnetic alloy layer prepared by laser quenching, and its application to a torque sensor

To fabricate an amorphous magnetic alloy layer, an Fe 78B 13Si 9 crystalline layer firmly fixed on a stainless steel substrate by silver brazing was melt quenched by laser irradiation. The laser-quenched layer consisted mainly of the amorphous single phase with an orderly striped pattern, divided by the heat-affected zones. The vibrating sample magnetometry measurements indicated that the laser-quenched layer had the magnetic easy direction along the direction of the laser scan. Taking into account the magnetic anisotropy, the laser-quenched layer was utilized to construct a non-contact-type static torque sensor. It was found that the sensitivity and the linearity were very good when the laser beam was scanned parallel to the direction of maximum stress induced on the shaft surface by the applied torque.

Fatal fluoride toxicity from silver brazing flux ingestion

ABSTRACTAim:To describe a case of fluoride poisoning due to ingestion of silver brazing flux and review the pathophysiology and treatment of such ingestions.Introduction:The dominant hazardous constituent of silver brazing flux is KHF2 (potassium hydrogen fluoride). This compound is toxic, corrosive and rapidly absorbed from the gastrointestinal tract to produce systemic fluoride toxicity.Case report:A woman ingested an unknown amount of silver brazing flux and was brought to the Emergency Department hypotensive and obtunded. Despite vigorous resuscitation and electrolyte replacement she developed refractory ventricular fibrillation and died eight hours later in intensive care.Discussion:Hydrogen fluoride and its salts are widely used in industrial and domestic products but poisoning by these agents is uncommon. Rapid absorption produces systemic fluoride toxicity. This generates hypocalcaemia, hypomagnesaemia and hyperkalaemia with death resulting from refractory ventricular arrhythmias. These chemicals are corrosive and may cause haemorrhage or perforation of the gastrointestinal tract.Conclusion:Survival from such ingestions is rare. Early recognition and appropriate treatment are essential to optimise outcome.

Construction and preliminary testing of perforated-plate heat exchangers for use in helium IIrefrigerators

Heat exchangers in cryogenic refrigerators must meet conflicting requirements for high thermal efficiency and low frictional pressure drops. This is particularly true in helium II refrigerators where the gas stream leaves the cold source at 15 mbar. Perforated-plate heat exchangers are likely to offer better overall performances for that application than the widely used plate-fin heat exchangers. Through their design they combine a high thermal conductance in transverse direction with a low thermal conductance in axial direction. The present paper reports on the initial stage of development of a fabrication method using photochemical milling of copper plates and stainless steel spacers, and silver brazing for bonding. Comparison of preliminary test measurements and calculations in the 80 to 300 K temperature range with flow rates between 1 and 5 g/s has confirmed that predictable results can be obtained for the thermal efficiency and the pressure drop with an accuracy of a few percent.

Comparison of thick ETP and OF copper joints produced by electron beam, high‐power laser and traditional silver brazing

Synopsis As part of an extensive range of tests carried out by Ansaldo Ricerche to develop fabrication technology for a nuclear fusion reactor, some specific work has been done on the welding of thick copper electrical conductors. This has been done in order to offer the electrical engineering industry some valid alternatives to the traditional silver brazing system which is often employed, even although there are sometimes limits to its use. In these investigations, after a series of setting‐up tests, some joints were made by electron beam and high‐power laser welding of two types of 10 mm thick copper: ETP (electrolytic tough pitch) and OF (oxygen‐free). These joints were compared, by means of mechanical tests, electrical measurements, non‐destructive testing and metallographic examination, with similar joints welded by traditional silver brazing. The results show that the joints welded by electron beam and laser guarantee better mechanical strength properties and quality.

CERAMETiL FILLER METALS 616, 716, 721

Abstract CERAMETiL 616, 716, 721 are silver brazing filler metals with a titanium-bearing coating to facilitate brazing to ceramics and other hard-to-wet materials without the need for prior metallizing procedures. This datasheet provides information on composition and physical properties. It also includes information on joining. Filing Code: AG-12. Producer or source: Lucas-Milhaupt Inc.

多層セラミックス基板の銀ろう付信頼性に関する研究

The effects of the W metallizing condition and silver brazing condition on the bonding reliability of the nail head lead pins of the multilayer ceramic substrates manufactured by co-firing was examined. High bonding strength by the silver brazing to the W metallized layer was obtained when the W metallizing layer was 23 μm thick or thicker and the quantity of the silver solder used was 0.24-0.38 mg/mm2 and the silver brazing temperature was 820-840°C. The bonding strength by the silver brazing was decreased after the brazed parts were heat-treated at 900°C. The cause of the degradation of the bonding strength was that the silver solder permeates into the W metallized layer and destroys the network of the W in that layer.

Corrosion and fracture of a silver tracheostomy tube

A sterling silver tracheostomy tube broke in use resulting in the death of a child. The nature of the fracture in the brazed joint is described, and corrosion identified as the mechanism of degradation of the joint. The corrosion is due either to exposure to body fluids over a long period, or to the use of hypochlorite solutions for cleaning and disinfection. The silver braze used had inferior corrosion resistance. It is recommended that appropriate grades of silver brazing alloy be used in the future, and that the mechanical integrity of medical devices joined with silver braze be regularly checked to anticipate failure in use.