Welcome To Members' Area Of The EABS Website
We hope that our visitors will decide to become Members when they see the support available. If they do so, in common with all our Members their nominated representative will be given a personal password that will give direct access to the folders in which technical articles are stored. They may then select and download the documents they wish to read. In the meantime, and as mentioned on the Visitors Page, EABS is happy to e-mail any one of our documents to a non-member. This can be arranged by your visiting the Contacts page, entering your details in the registration details boxes, stating the number of the document that you would like to have in the comments box, and submitting it us.
Folders will be updated regularly with further documents. Many will be unobtainable from other sources.
We expect that many who enter this part of the site will find documents that are relevant to their brazing interests. Suggestions for additions and improvements are always welcome: simply send an email via the Contacts page. We can't promise to respond to all requests but we shall take notice of what you say and ensure it receives careful appraisal. Not all such matters are likely to have ready-made answers and we may wish to suggest other ways of tackling issues. For example EABS also provides on-site brazing consultancy and staff training courses. We shall always get back to people who make the effort to let us have their suggestions.
The EABS Technical Library
The library is currently comprised of one General Area and five main subject areas. These are as follows:
Area 1: Technical Articles that do not easily fall into any of the Categories covered in the other areas.
Area 2: Low-temperature silver brazing.
Area 3: High-temperature furnace brazing.
Area 4: Brazing Aluminium.
Area 5: Brazing in air
Area 6: Technical Notes
Further areas will be added as the need arises.
The titles of the documents to be found in each of these Areas, together with a short description of the matters covered in each document, are set out below:
AREA 1: Technical articles of a 'general' nature
A method of determining the % level of filling of a brazed joint
This short article describes a suitable inspection method for determining the percentage degree of joint-filling that has been achieved during a brazing process.
Document size: 41.0 KB, 427 words on two A4 pages
Problem solving in brazing
This summary article outlines the principles of Process Analysis and concludes with a practical example of the use of the analysis method described.
Document size: 80KB, 4100 words on eight A4 pages
The process analysis route to problem solving in brazing
The 'Holy Grail' of Production Engineers who employ brazing as their joining method is to have a process that is as close as possible to having an efficiency level of 100%.
This Paper shows how a rapid, yet detailed, appraisal of the six fundamental rules for successful brazing can be used to determine the overall efficiency of a given brazing process. With the process efficiency established, and by separating the overall process into nine clearly defined steps, the Paper discusses how a simple and systematic approach to the process being considered will establish the 'best practice' solution to it! The solution derived may not make the process 100% efficient, but it is certain that if the solution is adopted a marked improvement in efficiency will result!
A practical example of the use of the process analysis procedure is described in fine detail.
Document size: 145KB, 4150 words on eight A4 pages
Brazing parameters - a small change in requirements can mean a major
change in the production process!
This document describes how the requirement to effect what appeared to be a quite modest change in the quality of the finished brazed part actually required the manufacturing process to be changed from flame-brazing in air with oxy-acetylene incorporating gas-flux to one of reducing atmosphere furnace brazing.
Document size: 1.02MB, 2880 words on five A4 pages
Brazing cemented tungsten carbide
This document might best be described as a tutorial on the brazing of tungsten carbide. The document begins by detailing the four criteria that must be satisfied when tungsten carbide is to be brazed to a backing piece. The main part of the paper details the six fundamental criteria that have to be taken into account when developing the 'best practice' process for this material. Problems that might be encountered when brazing tungsten carbide are discussed, and ways of overcoming them suggested.
Document size: 139KB, 8450 words on eighteen A4 pages
The development of a flexible wear-resistant coating system
This document traces the development of 'Brazecoat'®, explains how it is used, and describes a practical application of its use in the construction industry.
Brazecoat® is a registered Trademark of Innobraze GMBH, Esslingen, Germany
Document size: 1.02MB, 2580 words on six A4 pages
Jigs and Fixtures - Part 1
This document provides a general introduction to the 'best-practice' principles of Jig and Fixture design. The four types of fixtures used in furnace brazing are described.
Document size 47KB, 3095 words on six A4 pages
Jigs and Fixtures - Part 2
This document is so large since it contains 13 illustrations. Two case studies dealing with the successful use of 'hot jigs' are detailed. One is concerned with the CAB brazing of automotive radiators fabricated from aluminium, the other deals with the brazing of compact stainless steel heat exchangers. The means of providing 'self-fixturing components by the judicious use of tack-welding and mechanical deformation are described. The paper concludes by describing two cases where over-enthusiastic design of the fixture resulted in the production of unsatisfactory parts.
Document size: 5.06MB, 1920 words on seven A4 pages
Brazing in antiquity - Part 1: Setting the scene
The brazing process has been used for at least 5000 years and is, therefore, one of the oldest metal joining techniques known to Man. This Paper reviews the historical background to the process, and explains why the development of the technique in Sumeria and Ancient Egypt followed different paths until about 2000 BC.
Modern understanding of the brazing techniques used in antiquity was, to some extent, clouded by the fact that some early archaeologists used the terms 'Melting' and 'Smelting' indiscriminately. However when brazing engineers with metallurgical expertise examined the problem, and established what the ancient craftsmen had at their disposal, and then compared this to the requirements of modern-day brazing technology, it became clear just how technically sophisticated the early metal workers were in regard to their brazing processes.
Document size: 332KB, 1800 words on four A4 pages
Brazing in antiquity - Part 2:
In order to come to grips with the detail of the materials and procedures used some 5000 year ago it is necessary to refer to early written references related to the brazing process. For obvious reasons these are few and far between; this Paper does, however, provide some details of the written records of brazing produced by Pliny the Elder in 60 AD as well as those of Theophilus writing in the 11th Century. Both writers make detailed reference to methods of brazing gold, and it is interesting to see how the methods they report upon are different yet, and as might be expected, the underlying technology upon which the methods are based are the same. The fact that the methods they report were effective is demonstrated by the use of colour pictures of a number of gold artefacts, (which are between 3300 and 4500 year old), used as illustrations in this document.
Document size: 862KB, 2775 words on six A4 pages
Documents 1.11 to 1.15:
This is a series of five articles about the most practical, and yet perhaps the most fundamental, aspect of brazing. The majority of 'serious brazers' rely on capillary force to either fill our joints, or at least to ensure that foil or clad filler metal that is sandwiched in the joint is retained there when the filler metal melts. We learn very quickly that unless our brazing gaps are correct both for the filler material and the process to be used, there is no guarantee that proper filling will inevitably result! The five Papers in this series discuss the more important considerations of this aspect of brazing technology.
The Brazing Gap - Part 1: Introduction
Document size: 27KB, 920 words on two A4 pages
The Brazing Gap - Part 2: Joints needing flux
Document size: 217KB, 4560 words on ten A4 pages
The Brazing Gap - Part 3: Joints for furnace brazing
Document size: 69KB, 2095 words on four A4 pages
The Brazing Gap - Part 4: 'Sandwich joints'
Document size: 217KB, 1820 words on five A4 pages
The Brazing Gap - Part 5: Filler material preplacement
Document size: 82KB, 1385 words on three A4 pages
Process analysis- The brazing of two different lengths of AA3003 tube into machined AA6063 blocks
This Paper presents the detailed solution to an aluminium-brazing problem that was being faced by a sub-contract manufacturer of components that are used in the water-cooling systems of passenger cars. In order to establish the ‘best practice’ solution to the problems being encountered the case study follows the well-defined Process Analysis route described in Documents 1.2 and 1.3 in this Area. It was found that in order to meet the customers specification it was necessary to make 10 changes in the overall process. The changes made, and the reasons for them, are described in detail.
Document size: 69KB, 3732 words on eight A4 pages
|Document 1.17:||A very brief history of brazing!
This document is a very brief appraisal of the development of the brazing process from its beginnings over 5000 years ago up to the present day. For further information on the brazing techniques used by the earliest practitioners of the technology see Documents 1.9 and 1.10 on this website.
Document size: 177KB, 2040 words on five A4 pages
|Document 1.18:||An introduction to Induction heating technology
Since it might be the case that the reader of this paper is unfamiliar with the technology of Induction heating this document approaches the fundamental technical aspects of induction heating for brazing from the standpoint of ‘first principles’.
It is important to accept that Induction heating is not, (as some would claim!), a heating method that will solve all production brazing heating problems! However, for brazing parts where the components to be heated are:
Document Size: 746KB, 6170 words on fifteen A4 pages
AREA 2: Low-temperature silver brazing
The first seven documents in this Area cover the more important aspects of brazing with silver-containing brazing alloys. The original series was written by Philip Roberts between 1995 and 1997, and was published in Welding and Metal Fabrication, an excellent journal that is, unfortunately, no longer being published. All seven articles have been revised and up-dated and, in consequence, we believe that they are an improvement on the originals! A further advantage is that we are not restricted for space, and so it has been possible to expand some areas of the original versions to make the subject matter being covered more detailed and so easier to understand. We hope that you like the series, and that you will find them helpful in your day-to-day work.
The fundamentals of low-temperature silver brazing Part 1: Principles and Definitions
Document size: 152 KB, 2222 words on seven A4 pages
The fundamentals of low-temperature silver brazing Part 2: Joint design
Document size: 313KB, 2525 words on seven A4 pages
The fundamentals of low-temperature silver brazing Part 3: Brazing material selection
Document size: 1.1MB, 3270 words on eight A4 pages
The fundamentals of low-temperature silver brazing Part 4: Heat patterns, over-heating & flame heating
Document size: 60KB, 2160 words on five A4 pages
The fundamentals of low-temperature silver brazing Part 5: Induction and Resistance Brazing
Document size: 1.01MB, 2395 words on seven pages of A4
The fundamentals of low-temperature silver brazing Part 6: Health and Safety in Brazing
Document size: 57KB, 2495 words on five pages of A4
The fundamentals of low-temperature silver brazing Part 7: Trouble shooting
Document size: 45KB, 2085 words on four A4 pages
Time for brazing to go Cadmium-Free
This very balanced article, available as an 8-page A4 leaflet, explains the compelling arguments why now is the right time for users of silver-brazing alloys to go Cadmium-free.
The potential problems that can arise in regard to the health of the brazing operators when they are using cadmium-bearing alloys are highlighted, and attention is also specifically drawn to the fact that a principle consideration of the EU Chemical Agents Directive, and related national regulations such as UK COSHH, is that the substitution of hazardous materials where safer alternatives exist is an overriding consideration. It discusses why the presence of cadmium in a brazing filler material can be a problem and, more particularly what these problems are. Towards the end of the article the Environmental reasons for eliminating cadmium are explained, as are the implications of making the change. The article contains a number of
Tables that show how the fact that a range of cadmium-free alloys is readily available makes it relatively easy for Industry to make this very desirable change in the brazing filler materials that they use.
The article is freely available as a pdf file to Members and Non-members alike in any one of the four languages: English, French, German or Spanish.
Interfacial corrosion of joints brazed in stainless steels
with low-temperature silver brazing alloys
In several of the documents that are to be found in Area 3: of Members Area of the EABS Website the theory and practice of the protective atmosphere brazing of stainless steels is covered in fine detail. For the sake of completeness, and because article we will consider aspects of the interfacial corrosion of brazed stainless steels joints, a failure mode that is relatively common, yet one that is not widely understood in the brazing Industry.
This short paper considers aspects of the interfacial corrosion failure of joints brazed in stainless steels with silver containing low-temperature brazing filler materials. This is a failure mode that is relatively common, yet even though this problem has been recognised since the mid-1960’s, experience from industry clearly demonstrates that this form of corrosion is neither understood nor, in the main, even considered as a possible cause of the joint failures that have occurred in brazed stainless steel assemblies. This may well be because detailed written information on the phenomenon is almost non-existent: this short Paper attempts to rectify this situation!
Document size: 211 KB, 2815 words on six A4 pages
AREA 3: High-temperature furnace brazing
Reducing atmosphere furnace brazing - Theory
This document could be described as a tutorial on the theory of reducing atmosphere furnace brazing. It examines how the reducing atmosphere removes the surface oxides from the mating surfaces of the joint; discusses at length how dew-point and temperature inter-relate in regard to oxide removal; explains why it is very easy to braze mild steel under reducing atmosphere and why stainless steel is substantially more difficult to braze; and explains why the volume and composition of the gas fed to the furnace needs to be controlled to ensure success. The costs of various reducing atmospheres are compared.
The Paper concludes with a brief discussion of inert and reducing atmosphere criteria.
Document size: 0.99MB, 6785 words on fourteen A4 pages
Reducing atmosphere furnace brazing - Practice
This Paper is the 'sister' to Document 3.1; it discusses the use of the two-types of continuous-conveyor furnaces, (horizontal-, and the 'Hump-back' type), that are widely used for brazing. 'Copper brazing' is described and the advantages of arranging for the gas-flow in the furnace to be 'zoned' so that parts do not have to pass-through a flame-curtain are discussed.
Furnace calibration, heat-pattern development, and the significance of belt speed are covered in fine detail.
The Paper concludes with a Section that covers the selection criteria for the filler metal pastes used for brazing under a reducing atmosphere.
Document size: 1.98MB, 6750 words on thirteen A4 pages
An introduction to vacuum brazing
As the title suggests, this Paper provides a brief introduction to vacuum brazing technology. The meaning of 'vacuum' is described, and the degrees of vacuum that are commonplace in vacuum technology are provided. Then follows a consideration of the various possibilities of the actual mechanism of surface oxide removal that occurs in vacuum. The fields of use of vacuum brazing, vacuum furnace criteria, and filler material considerations for vacuum brazing are discussed. The Paper concludes with a brief introduction to the types of furnaces in use, and concludes with a brief discussion of the process cycle for a typical vacuum brazing operation.
Document size: 1.05MB, 5025 words on eleven A4 pages
Furnace temperature surveys in vacuum brazing
This Paper is concerned with the 'best-practice' method of undertaking a furnace temperature survey in a vacuum furnace. It first explains why one should bother with such things and goes on discuss the effect of an actual furnace load and how the Approach rate can affect the overall success of the brazing being undertaken. It goes on to deal with the load temperature survey, explaining what it is and what to do if the survey indicates that problems exist. It concludes by stressing the need to ensure that effective Planning is undertaken and results kept on file!
Document size: 120KB 1830 words on four A4 pages
Units of Vacuum - Conversion data
The document contains a series of Tables which provide Conversion values between MmHg, torr, mbar, Pa, and microns Hg for a range of pressures between 1.0mmHg to 1 x 10-4 mmHg.
Document size: One A4 page
Hydrogen for Brazing
As the volumes of stainless steel assemblies rise to meet the demands of the automotive industry brazing them in continuous atmosphere furnaces is becoming increasingly popular. To obtain a bright, well-brazed, product all the components of the brazing system must be chosen with care. One of the more important components of that system is the furnace atmosphere. Nickel alloy brazing of stainless steel, depending upon the nickel filler material used, is carried out at temperatures in the range 930°C to 1200°C. In this case, the critical element with regard to the atmosphere requirements is the chromium in the stainless steel. Even when brazing at 1000°C, and using 100% hydrogen, a dew point of -37°C is required to suppress oxidation of chromium. However, experience has shown that to produce good joints in practice, dew points better than -50°C are required to reduce fully the chromium oxides present during the process cycle. This paper considers these aspects in some depth, touches upon the type of continuous brazing furnaces in common use and provides information concerning the generation and storage methods that are available.
Document size: 508KB, 1362 words on four A4 pages
Brazing Refractory Metals
This document provides some pointers to the problems that face engineers who are required to braze one of the refractory metals aluminium, beryllium, molybdenum, niobium, tantalum, tungsten, and zirconium.
Perhaps the most important property of these metals, and most certainly the one that poses the greatest problem to people who are required to braze them, is the fact that they have a strong affinity for oxygen and rapidly develop a strongly adherent layer of surface oxide that is not only generally very hard, but is also a 'nightmare' to remove, and then being prevented from re-forming, during the brazing operation! This technical note comments on these matters, and suggests brazing procedures and filler materials that some workers in the field have found acceptable.
Document size: 300KB, 2492 words on six A4 pages
An Introduction to the Brazing of Ceramics
This document discusses the fundamental considerations in cases where it is required to braze a ceramic either to itself, another ceramic, or a metal. The background to the development of ‘active’ brazing alloys is described together with some pointers regarding the selection of a filler material for such applications.
Document size: 409KB, 2335 words on six A4 pages
AREA 4: Brazing Aluminium
An introduction to the brazing of aluminium
In the last twenty years there have been some dramatic changes in the application of 'brazing' as an industrial joining process, and nowhere have these changes been greater than in the joining of aluminium. This paper investigates why this is so, and what has occurred in the development of aluminium brazing during this period.
Pre-1980 almost all aluminium brazing was undertaken in salt-baths, but this is an environmentally 'unfriendly' and potentially hazardous procedure, and an alternative method had to be found. Vacuum brazing worked, but was very expensive and so not suited to mass-production brazing. However, when in the early 1980's the automotive industry began to seek ways and means of reducing the weight of their vehicles, an obvious solution was to use as much 'light metal' in their construction as possible: and this meant using aluminium! Consequently it was then clear that the demand for mass-production brazing of aluminium assemblies was beginning to grow, this provided the impetus to develop the continuous conveyor furnace brazing of aluminium in conjunction with a non-corrosive flux under an atmosphere of nitrogen, the world-renowned NOCOLOK® process . This was one of the most significant advances seen in brazing technology in the second half of the 20th Century.
The paper, describes how and why the brazing of aluminium is 'different' to that of other metals, and comments on certain of the more commonly encountered metallurgical problems that are faced by practitioners of the process, and how these can be overcome. It considers both flame- brazing and the fine detail of continuous-conveyor furnace brazing of aluminium under nitrogen, highlighting the pit-falls that can trap the unwary, and how they can be recognised, (and avoided)! Furnace design criteria are touched upon, as is the vacuum brazing of aluminium.
NOCOLOK® is a registered Trademark of Solvay Fluor GmbH & Co. K.G., Hanover, Germany
Document size: 1.05MB, 6575 words on twelve A4 pages
Value-added considerations for Aluminium-brazing Atmospheres
It is an established fact that there are in excess of 600 controlled atmosphere brazing furnaces in use throughout the world that are brazing aluminium in association with non-corrosive fluxes under a nitrogen atmosphere. Consequently it is important for reasons of operating cost, quality, and consistency that the optimal condition of the atmosphere be maintained. The introduction of Nitrogen and the regulation of the subsequent flow patterns are fundamental to achieving the desired results. This Paper, originally presented at the AFC-Holcroft 7th Annual Aluminium Brazing Seminar in Indianapolis in 2002, not only considers the interactions that can occur between the fluxes and the atmosphere, but also includes suggestions for the use of real-time atmosphere-based control systems as well as the use of on-site nitrogen generation. All of these factors play an integral part in ensuring that the end-results are in line with requirements.
Document size: 137KB, 3700 words on eleven A4 pages
AREA 5: Brazing in air
Section 5.1: Flame Brazing
The fundamental parameters of flame brazing
The document gives the reasons why flame brazing is so popular and so satisfies more brazing applications than any other heating method. It goes on to discuss Flame process relationships, heating and flames, the difference between heat-energy and temperature in relation to flame brazing, and heat transfer mechanisms. It concludes with a brief discussion on the need for, and the production of, uniform heating of parts that are to be joined by brazing.
Document size: 64.5KB, 2085 words on five A4 pages
Gases and Gas Mixtures
This document discusses the meaning of calorific value, temperature, burning velocity of the gas, and fuel-gas composition and how these parameters affect heat transfer. The paper gives a short a description of the effect that either flame-lift or flame light-back will have on flame-brazing processes and concludes with a discussion of the capability of different fuel-gas mixtures to transfer heat.
Document size: 855KB, 3010 words on eight A4 pages
Burner design and operational parameters
The size of this document is due to the presence of colour illustrations! The paper Stresses the importance of understanding that it is the flame that heat the work, and that as a result the term 'torch heating' is incorrect! It goes on to describe the vital importance of pilotage in the design of burners. Such burners ensure that parts can be heated evenly to brazing temperature using gas mixtures of high calorific values at a mixture velocity that would, in the absence of pilotage, lead to the flame being extinguished due to the effect of 'flame-lift.
Document size: 875KB, 910 words on three A4 pages
Manual flame brazing
This document is the basic instruction manual for the technique of manual flame brazing. It opens with a brief discussion of torches and the flame settings necessary to avoid the potential to produce small gas blisters in the fillets of filler material and goes on to consider the avoidance of hydrogen embrittlement occurring in cases where 'tough-pitch' copper is being brazed. This is followed by six detailed sections relating to Cleaning prior to brazing; Fluxing; Assembling the parts; Heating; Post-braze cooling and, finally, flux residue removal. The Paper concludes by listing the Ten Golden rules for Manual Flame Brazing.
Document size: 419KB, 4240 words on eight A4 pages
An introduction to automated flame brazing
The document opens with a short discussion related to the classification of the various types of automated flame brazing machines and where they fit in the overall hierarchy of Process Complexity. It goes on to draw a comparison between an operator and a machine, demonstrating that the attributes possessed by an operator are superior to a machine in all but the ability to fix, and then adhere to, the time taken to complete a brazing operation. It concludes with a brief summary of the types of machines that are used in the automation of flame brazing processes.
Document size: 44KB, 1715 words on three A4 pages
Trolley- and continuous conveyor machines
The document opens with a brief summary of Flame brazing Process Complexity and moves on to describe the three basic types of trolley machines and their mode of operation. It is pointed out that as process complexity increases the innate flexibility of the production system reduces. The paper then turns to a discussion of the two-types of machines that have a continuously moving work track, and describes their advantages and disadvantages.
Document size: 504KB, 2100 words on six A4 pages
Rotary indexing machines
This document is devoted to the consideration of the two basic forms of rotary indexing flame brazing machines and provides details of the advantages and disadvantages of both types. It is pointed out that the ultimate in process efficiency is likely to be achieved when a mechanically indexing system is employed. The paper goes on to discuss the theory associated with the design of such systems, and discusses the importance of heat-pattern, the number of machine stations, typical time parameters of an operational machine, and ancillary automation devices to permit automatic loading, the application of fluxes and filler materials, post-braze cooling, and component unloading. The paper concludes with a detailed discussion of the parameters that have to be taken into account when selecting a suitable machine for a given production requirement.
Document size: 313KB, 6385 words on thirteen A4 pages
Automated flame brazing with filler metal pastes
When using filler metal pastes on rotary indexing flame brazing machines the heat pattern that has to be developed in the component is substantially different to that employed where filler metal preforms are used.
This paper examines a specific flame-brazing application and shows the typical heat pattern development for both a filler metal preform and a filler metal paste. In the latter case it will be seen how and why the heat pattern at each of the four heating stations on the particular machine differ, and why it has to be specific to each station in order to produce the desired flow of the filler metal paste, and satisfactory joint filling, at the final brazing station.
Document size: 436KB, 1695 words on five A4 pages
Section 5.2: Induction Brazing
The fundamentals of Induction heating for brazing
This is the first of three papers that are concerned with the general application of induction as a heat-source for brazing applications. The companion papers are Docs 5.2.2 and 5.2.3. In order to obtain a realistic overview of the subject it is recommended that all three documents should be read.
The paper opens by pointing out that induction heating is nowhere near as universally applicable as flame brazing, but that it has attributes that make it highly attractive and the preferred heat-source for a moderately large number of applications.. It goes on to explain the basic principles of the process, outlining the advantages and disadvantages that attend its use, and concludes with a section related to what the process offers in the technology of brazing.
Document Size: 63.5KB, 1900 words on four A4 pages
Induction heating practice
This is the second paper in series. It opens with a discussion of the types and designs of inductors and explains where, in the vicinity of an inductor, the assembly will experience both the maximum and minimum efficiency of heating. It goes on to point out that in addition to the electrical resistance of the materials to be brazed by induction heating there are five further vital parameters that have to be considered. These are defined and discussed over a number of consecutive pages. Then follows a discussion of the need to pay close attention to the joint gaps size, and the ideal approach to applications to be adopted where dissimilar materials are required to be brazed by induction. The paper concludes with a look at the criteria that need to be taken into account when choosing an induction machine for a particular application.
Document Size: 501KB, 4765 words on eleven A4 pages
Automated Induction brazing
This is the third paper in the series. It opens by explaining why it is that mechanised brazing where induction is used as the heat-source is relatively rare. It goes on to point out that the first steps in automated induction brazing is where a number of assemblies are brazed in a single operation using specially designed inductors, and stresses the vital importance of ensuring that each assembly being brazed in this manner is located so that it is axially central within the inductor. The paper then turns to a description of two relatively complex rotary indexing brazing machines, brazing tungsten carbide to steel. One machine is devoted to the manufacture of brazed carbide-tipped burs, and is available in four different levels of complexity, the other is employed for the brazing of formed tungsten-carbide plates to the faces of diesel engine rocker arms. Both machines provide an excellent example of the attention to detail that has been necessary to develop the systems from the concept to the realisation stage of complex automation projects.
Document Size: 890 KB, 3465 words on eight A4 pages
AREA 6: Technical Notes
Section 6.1: Criteria for Brazing in a Vacuum Furnace
|Document TNV 1:||
Introduction, with an Index to the series
1.1 Vacuum brazing furnaces
A typical cycle
1.2 Workpiece and charge characteristics
Brief introduction to some charge features
1.3 Temperature uniformity
Different types of uniformity, and Approach rates
1.4 Vacuum quality
Introduction to in-leakage and bake-out Users should be prepared to find own standards
1.5 Operating standards
Users should maintain their furnaces to achieve standards of temperature control and vacuum quality suitable for the work undertaken
1.6 The influence of joint type
Vacuum must also protect filler metals. These vary in the degree of protection required
1.7 The influence of filler metal type on protection needs
Glossary of terms
Document size: 101 KB. 4300 words on 10 pages of A4 paper
|Document TNV 2:||
Targets for temperature control
2.1 Thermocouple calibration
Some indications of t/c ageing performance
2.2 Methods of in-furnace re-calibration
2.3 Temperature distribution within the charge and charge space
TUS: (Empty) Temperature Uniformity Survey ChTS: ChargeTemperature Survey
2.4 Furnaces with trimmed heater zones
2.5 Approach rate
Approach rate is often neglected. Why such neglect may be of particular importance in high temperature brazing
(Pointers to the need for the up-rating of temperature control)
Document size: 89 KB. 3150 words on 9 pages of A4 paper
|Document TNV 3:||
Targets for vacuum quality
3.1 Vacuum gauging and vacuum quality
The 'one micron fallacy. The importance of controlling in-leakage. Typical gauge types and a source of confusion Suggested practical approach to maintenance and calibration of gauges
3.2 Practical tests of vacuum braze quality
Routine NDT, plus limited destructive inspection to the extent required by an application Spreading tests and ‘T’ tests and visual checking
3.3 Benefits of baking-out and how to give a ready-made quick demonstration
Practical benefits Programming and recording (see also App. A)
3.4 Leak testing of vacuum furnaces
Pressure rise rate testing after bake-out Examples of test results and variation with size of furnace tank Proposed two-level actions to repair leaks
3.5 Leak location and repair
Difference between overall in-leakage rate and leak location for repairs
Appendix A: Proforma programming and report sheet for in-leakage testing
Appendix B: Notes on leak testing large vacuum plant
B.1 General requirements
B.2 How is leak tightness measured
B.3 What precautions must be taken when measuring Leak tightness
B.6 Leak-testing criteria
Document size: 227 KB. 13500 words on 27 pages of A4 paper
|Document TNV 4:||
Problem solving in vacuum furnace brazing: a new tool
Vacuum furnace brazing is increasingly being used for brazing workpieces with many multiple brazes, particularly to serve high volume markets such as the automotive feeder industries. By reporting Braze Defect Rate, in addition to a Yield Rate, much more information can be revealed about the success of a brazing operation without compromising commercial or technical confidentiality. It is simply not sufficient to ask “Why can’t we be as good as Company A Ltd which is brazing with a yield around 98%?”.
The Braze Defect Rate is a guide to both braze complexity and also to the degree of success. A yield percentage of good workpieces by itself doesn’t convey this information because some may have only one brazed joint and others many hundreds! But the addition of a Braze Defect Rate goes a long way toward filling this information gap and allowing viable comparisons to be made.
There are two parameters:
Braze Yield % = No. of good workpieces x 100 / Total no. of all workpieces
Braze Defect Rate % = No. of defect joints in a batch x 100 / Total joints in the batch (Case A)
Further, No. of workpieces with defective brazes x 100 / Total joints in all workpieces (for batch, day, month etc) Or: / Total workpieces x no. of brazed joints in each (Case B)
This document shows that that Case B is valid most of the time, at least for yields down to 85% because, under production conditions it is often not possible to determine the precise number of faulty brazes that are present on a workpiece, but merely that one or more is present. This document indicates that almost certainly there will be only one random defect per workpiece at relatively high yields - thus we can substitute the simple number of workpieces found defective at a post braze test instead of the (unchecked) number of defective brazes. No specific further action is needed at the time of inspection.
The method of analysis is given in detail for those who may wish to verify it in their own circumstances. The underlying reason is that at the higher end of yield, the chance is vanishing small of having more than one random defect per workpiece.
Document size: 465KB, 7000 words on 19 pages of A4 paper