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PWL#058 - New Brazing Handbook, GMAW of Titanium, Cryogenic Processing Part 2, New website pages... June 02, 2008 |
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| We hope you will find this Letter interesting and useful. Let us know what you think of it. PWL#058 - New Brazing Handbook, GMAW of Titanium, Cryogenic Processing Part 2, New website pages on Resistance Welding Tips, Creep Resistant Steels, Brazing Inspection and Joining Galvanized Steels, Welder Certification and more...
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1 - Introduction 2 - New Brazing Handbook 3 - How to do it well: GMAW of Titanium 4 - Filler Metals for Aluminum Welding 5 - Online Press: recent Welding related Articles and Video 6 - Terms and Definitions Reminder 7 - Article - Cryogenic Processing II Correction 8 - Site Updating: Resistance Welding Tips, Creep Resistant Steels, Brazing Inspection and Joining Galvanized Steels 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contribution: Welder Certifications 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board
1 - Introduction This 58th new issue of Practical Welding Letter opens with a presentation of the AWS Brazing Handbook Fifth Edition. It is a rich source of all information needed on Brazing, written by many teams of experts who share their knowledge with the readers. It is a book one must have, to consult and to learn from. It is strongly recommended to anyone having professional interest for industrial work or for hobby applications. We then take up from a question asked by a reader about practical uses of GMAW for Titanium. It is a timely question because, contrary to the opinion that it is a mainstream process, there is still a long way to go until the practice will be considered a piece of cake. It is a subject worked on by many excellent researchers and professionals. In the Filler Metal section we propose quite a few online resources likely to provide many hours of study and many items to ponder. Keeping this information well organized in a special folder will provide a useful reference ready for use at any time. We have a follow up on the subject of Cryogenic Processing. You may remember that in the last issue the transformation of retained austenite into martensite was introduced as the all important mechanism of properties improvement. It appears that our presentation was one-sided and incomplete although not erroneous or malicious. A kind reader who has experience in the field sent us an additional article providing further information. We are glad of this opportunity to correct the previous impression. For the Site Updating we added four more pages readily reachable from here. The new Pages of the Month deal with Resistance Welding Tips, Creep Resistant Steels, Brazing Inspection and Joining Galvanized Steels. See Section 8 further down. Welders Certifications are the passport to progress for any rewarding career. Essential information is offered to those who consider obtaining this recognition from AWS. Elsewhere, other organizations provide similar credentials internationally accepted. The other sections are available as usual. We would like to get feedback and comments. Send us your thoughts by e-mail. Please don't use Reply, use the Contact Us form instead. 2 - New AWS Brazing Handbook The new Fifth Edition of the AWS Brazing Handbook is probably one of the best reference books on Brazing in general. Written by many expert teams the information is organized in 36 Chapters that fill over 700 pages. The Handbook covers all important subjects, from Design, Filler Metals, Fluxes and Atmospheres, to assembly, Corrosion and Inspection of Brazed Joints. Chapters on Codes and Standards and Safety and Health follow with all needed References. Then come Chapters devoted to all the processes used for Brazing, with plenty of detail, illustrations, Tables and Graphs. For those needing still deeper understanding, rich Bibliographies are added to each chapter. Special Chapters, devoted each to a different material or group of materials start with Chapter 20 dedicated to Aluminum. This book represents a wealth of knowledge and long years experience distilled in the minds of those who wrote it. The chapters are easy to read and to understand. It is a pleasant duty to recommend this Handbook to all those in need to know what and how and why Brazing is done. Your professional book shelf will receive an important boost by this addition and your knowledge will expand. In its presentation, AWS informs that the book... "Provides a comprehensive, organized survey of the basics of brazing, processes, and applications. Addresses the fundamentals of brazing, brazement design, brazing filler metals and fluxes, safety and health, and many other topics. Includes new chapters on induction brazing and diamond brazing." A preview of the Index and of the first page of the first Chapter can be seen online and downloaded from AWS BRH
3 - How to do it well: GMAW of Titanium Q: Hi Elia, A: From a quick search I found that Titanium GMAW is done but still somewhat experimentally. Special means have to be employed and the technique has to be developed. The abstract from an article found at: DTIC,
states: "There are initiatives to develop low-cost titanium materials supplies; however, low-cost and high-rate fabrication processes are sorely lacking. Welding and joining technologies enable improved manufactured components by reducing the weight, production time, and cost of joining parts. Improved welding technology increases product lifetimes and makes possible the fabrication of large structures. Gas Metal Arc Welding (GMAW) has the potential to significantly improve the quality, speed, and penetration depth of titanium welds, while reducing the cost per part. However, this result can only be achieved if proper weld parameters are selected and dynamically maintained during the welding process due to the nature of titanium." See also the following: Titanium Welding Technology New Joining Technology for Titanium Pulsed GMAW of Titanium Novel Titanium Wire The problem of the "Wandering Arc" (outlined in the above citations) will be addressed also at the 19th AeroMat Conference and Exposition, to be held
June 23-26, 2008 at the Austin Convention Center, Austin, Texas USA.
4 - Filler Metals Resources on Aluminum Welding Please see hereafter informative resources on Aluminum Filler Metals and Aluminum Welding. May we suggest that you download all of them and save in a special folder you will open for this purpose. From Miller Welds: Pulsed MIG Improves Aluminum Welding Performance. GMAW (MIG) Aluminum Welding Hints. Aluminations(1): Shedding Light on Aluminum Welding Issues. Aluminations (2): Shedding Light on Aluminum Welding Issues. Aluminations (3): Shedding Light on Aluminum Welding Issues. Aluminations (4): Shedding Light on Aluminum Welding Issues. Aluminations (5): Shedding Light on Aluminum Welding Issues.
From Lincoln Electric: Aluminum: Experience in Application. Common Mistakes Made in the Design of Aluminum Weldments. Feeding Issues with Aluminum MIG Wires . Preventing Cracks in Aluminum Welds.
From AlcoTec Wire Corporation: Understanding the Aluminum Alloy Designation System. Understanding the Alloys of Aluminum. Trouble Shooting for Aluminum Welding. 5 - Online Press: recent Welding related Articles and Video Subscribe to ASM professional newsletters
to get the valuable benefits of timely information on the technologies you need for your continuing education: Downloads from AWS: From TWI: From Design News: From Inframat Corporation: (Article Page + Video)
6 - Terms and Definitions Reminder Blind Joint is one lacking any visible part. Brazing Procedure Qualification Record (BPQR) is a document that records all the brazing parameters used to produce an acceptable test piece and the results of nondestructive and destructive tests that were done to qualify a Brazing Procedure Specification. Circular Electrode is one of a pair of discs of a special copper alloy that are used in resistance roll spot or seam welding to join overlapping metal sheets squeezed between them. Dissolution is the alloying of base metal into the molten brazing filler metal. Mushrooming is the deformation of the tips of resistance spot welding electrodes under pressure and heat welding conditions. Nonvacuum EBW is a variation of Electron Beam Welding where the beam emerging from the high vacuum environment is made to produce welds in materials kept in air. Sandwich Brazement is an assembly of dissimilar materials where, besides filler metals, transition materials are present to minimize thermal stresses. Torch Brazing uses the heat of a gas combustion flame to produce brazing. 7 - Article - Cryogenic Processing - Part 2 - A Correction Note - I should have been more cautious, having been advised that the matter of my note on this subject published last month is emotional (PWL#057.) I apologize if my readers were misled by my assertion. As far as I am aware there is nothing incorrect in what I wrote, except perhaps for some missing details in the cooling rate schedule for specific cases. It appears, however, that the picture I outlined was incomplete and I regret this shortcoming. Fortunately for the good name of this publication, and for the purpose of providing reliable information to our audience, one of the readers who happens to be deeply involved in the process, piqued by the partial presentation, after having scolded me for my incomplete exposition, agreed to send us a corrective note that I am glad to be able to show here to anyone interested in having the facts put straight. I believe that the citation quoted last month is still valid as confirmed by a new citation quoted hereafter, and that more definitive research has still to be conducted on the subject while new applications may enjoy definite benefits if selected thoughtfully through trial and error.
The austenite to martensite transformation is only a part of the process. In general, cryogenic processing involves the slow cooling of the part being treated down to –300 0F (-184 0C) followed by a hold at that temperature, and a slow heat up to room temperature. One or more tempering cycles complete the process. Published research and practical experience demonstrate that many metals, some plastics, and other materials respond to cryogenic processing. For instance, NASA published a paper on welded aluminum. (Effects of Cryogenic Treatment on the Residual Stress and Mechanical Properties of an Aerospace Aluminum, Po Chen, Tina Malone, et al, IIT Research Institute and NASA). They found significant improvements in stress corrosion cracking and reduction of residual stresses of 9Ksi in the parent metal, 12ksi in the welds. Another example of the process working is in automotive brakes. The common automotive brake is made of SAE J431 G3000 cast iron. The material is used as cast. The microstructure of automotive brakes is pearlitic. My company has had dozens of tests done on brake rotors by both Greening Labs and by Link Laboratories, two of the most prominent brake testing labs in the USA. The tests were done per Method B of SAE J2707 - Wear Test Procedure on Inertia Dynamometer for Brake Friction Materials. These tests revealed up to four times the life on treated rotors. The use of cryogenic treated rotors is growing rapidly on police and fire vehicles, and the US Postal Service has given its approval of processed brakes based on the tests by Link Laboratories. A third example is the use on thin film magnetic memories. In a process tryout for Honeywell, they stated, "We found that your process had a large impact on the stress of the films that were deposited." Indications were that the process was working at the atom to atom relationships on films that were only several atoms thick. The use of cryogenics on diamond and CBN Plated grinding wheels has shown up to a tenfold increase in life of these wheels in practical industry use. A patent application has been filed on this application. Research has proven other effects of the process. In his paper "Cryogenic Treatment of Tool Steels", published in Advanced Materials and Processes, December, 1998, pages H23 to H29, Dr. David N. Collins showed that cryogenic processing forms very fine carbides in steels. The number of these carbides formed is related to the time the steel is held at –3000F (-184 0C). In a similar manner, Fanju Meng et al talk about the carbide formation in "Role of Eta-carbide Precipitations in the Wear Resistance Improvements of FE-12Cr-MO-V-1.4C Tool Steel by Cryogenic Treatment". Why does cryogenic processing work, especially on non-ferrous metals and plastics? I have some ideas, but don't know precisely. Why is this? Well, the bulk of the research has been done on ferrous metals, and most of that has been done to prove the process works. Many people concluded that the conversion of retained austenite was the answer and just stopped there. But the use of the process in metals and plastics that do not involve retained austenite proves beyond a doubt that more is happening. In the March/April 2008 edition of Heat Treating Progress (the ASM heat treating magazine) the editor states, "While claims of advantages of subzero treatments are fairly abundant, there is much less information in the literature regarding a clear understanding of the mechanisms of property improvements, other than, in the case of steels, the obvious conversion of austenite to martensite." Notice the acknowledgement that there are other mechanisms. My personal observations indicate that the process is working because it refines the atom to atom relationship in the crystal structure. While it would be very nice to know exactly what is going on with cryogenic processing, nothing prevents its use when successful and cost effective. My company cooperates in serious research into the subject. We just completed a project with a team of students at the University of Texas, and are working with a doctoral student at Marquette University. We've been involved with students at Illinois Institute of Technology who have done some very interesting work. No doubt someone will be able to quantify the process in the future. Frederick J. (Rick) Diekman PWL is grateful to Mr. F. J. Diekman for his (slightly edited) interesting contribution. We asked for more information on suggested applications, on costs, advantages and limitations, but at this time we have no more to add. Additional details can be found in
8 - Site Updating: Resistance Welding Tips, Creep Resistant Steels, Brazing Inspection, Joining Galvanized Steels We are glad to be able to inform our readers that the following new Pages of the Month were recently added to our Weldsite as shown here by the clickable Titles with a short Description: Resistance Welding Tips may help in setting up welding schedules or for troubleshooting. Introduction to feedback control for consistent performance. Creep Resistant Steels are designed to perform satisfactorily for long time at high service temperatures. Their composition requires special precautions, notably preheating, for successful welding. Brazing Inspection is the complex of rules and methods applied to determine if all precautions and operations were correctly performed and if the requirements are met in the brazed joints. Joining Galvanized Steels has a long history of successful applications. The special problems are quite understood and suitable solutions are currently applied. Fume extraction and personal masks should be used. We hope that these pages may prove interesting to readers looking for information, at least as the starting point for their query. To find new pages as they are published see periodically the Site Map Visit also our New Page on Metals Knowledge for assembling at no cost your Encyclopedia Online, a rich collection of valuable information on Metals, from expert Internet sources. 9 - Short Items 9.1 - Caustic means a burning or corrosive substance. Examples are hydroxides of a light metal, like sodium hydroxide or potassium hydroxide. 9.2 - Concentration refers to the mass of a substance contained in a unit volume of a liquid sample, expressed in grams per liter or equivalent. 9.3 - Drawing in metal forming operations means the deformation of sheet metal between a punch and a die in a press to produce cup like parts. For long semifinished shapes it means forcible pulling through a die to impart a given shape and definite dimensions. 9.4 - Fatigue is the formation of minute cracks and their progressive growth leading to fracture under repeated or fluctuating stresses of maximum value smaller than the ultimate tensile strength of the material. 9.5 -Inhibitor is a substance that hinders some specific chemical reaction, like metal solution without affecting the removal of scale from steel. 9.6 - Segregation means the nonuniform distribution of alloying elements, impurities, or micro-phases in metals and alloys or the concentration of alloying elements at specific regions, usually resulting from primary crystallization of one phase with the subsequent increased concentration of other elements in the remaining liquid. 10 - Explorations: beyond the Welder The Phoenix Mars Lander. (Video) Phoenix Mars Lander
How Abrasives are Made (Video) Enjoy a free, "inside" look at the Guide that
SBIers actually use. 11 - Contributions: Certifications We briefly addressed the subjects of Quality Assurance in Welding in (7) PWL#017 and of Weld Quality in (2) PWL#034. Now, taking the cue from an Article on AWS Certifications published in the March 2008 Issue of the Welding Journal at page 27 we pause to take a close look at the system of these documents, conceived and administered to provide to their holders the credentials needed to demonstrate knowledge and competence in specific welding procedures. Similar Certifications address the needs of related disciplines. Such demonstrations are increasingly required by contractors and procuring agencies so that they provide a powerful and recognized tool helping those seeking a job or a position in finding the kind of work they look for. The list of Certification Programs from AWS is available at page The official AWS definition is: "Certification. The act of determining, verifying and attesting in writing to the qualification of personnel in accordance with specified requirements". The page shown at The document establishing the requirements for Certified Welders and including the Form-1-783 for
Application for AWS Certified Welder, is Standard AWS QC7-93, downloadable from page Specific Supplements (C and F) govern the requirements for Sheet Metal and for Chemical Plant while Supplement G is generic. All can be downloaded from the above page. A welder wishing to access the AWS Certified Welder (CW) program has to contact an Accredited Test Facility, the list of which is also downloadable from the above pages, and to register for the test. The welder has to prove his/her skill by welding a given joint according to a specific Welding Procedure Specification. The WPS employed must be relevant to the actual work the welder will be called to perform once certified. In Europe the active partners In Training and Certifications are the Welding Institute and the European Welding Federation who implement the directives established by: International Institute of Welding – See also 12 - Testimonials From Frank Fan (e-mail address removed for security) Dear Mr. Elia Levi,
From Kai Kirk Thanks, I really appreciate the advice. Kai 13 - Correspondence: a few Comments Comparison of Standards is a recurring motive that occasionally bothers readers and other people. It is quite infrequent that two different Standards issued in remote regions cover exactly the same details spelled out in them so that they are completely interchangeable. Although serious efforts are invested in trying to simplify and unify Standardization, in view of facilitating global commercial exchanges, it must be recognized that if there is a general similarity, the exceptions must be checked one by one and approval must be obtained from the purchaser before the substitution can be accepted. Even then most people would not want to take responsibility. There is probably no simple way out. However it may be that most of times there is no need to meet contractual obligations, and an approximate equivalence is all that is looked for. For this easier task, compilations of composition and of properties may help if made available in understandable languages. 14 - Bulletin Board 14.1 - Welding in Aircraft and Aerospace Conference 14.2 - FABTECH International & AWS Welding Show
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