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PWL #032-WPS, Welding thin stainless, FCAW Resources, Corrosion, FCA Welding Tips, Success of FSW April 01, 2006 |
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| We hope you will find this Letter interesting and useful. Let us know what you think of it. Welding Procedure Specifications, Welding thin Stainless Sheets, Flux Cored Arc Welding Resources, Corrosion of Weldments, Flux Cored Arc Welding Tips, Success of Friction Stir Welding and more...
This publication brings to the readers practical answers to welding problems in an informal setting designed to be helpful and informative. We actively seek feedback to make it ever more useful and up to date. We encourage you to comment and to contribute your experience, if you think it may be useful to your fellow readers.
You are urged to pass-along this publication to your friends, if you like it, and if you want to help them.
1 - Introduction 2 - Article: Welding Procedure Specifications 3 - How to do it well: Welding thin Stainless Sheets 4 - Filler Metal FCAW Electrodes Commercial Suppliers Resources 5 - Online Press: recent Welding related Articles 6 - Terms and Definitions Reminder 7 - Article: Corrosion of Weldments 8 - Site Updating: FCA Welding Tips 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contribution: FSW 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board
1 - Introduction Welcome to this 32th issue of Practical Welding Letter, the first Spring issue of this year. It has been a busy first Quarter with new initiatives and interests. Among the initiatives we count the launch of our Blog as an RSS Feed, designed to bring the news from our site to the attention of our readers at their request. If you do not know what we are talking about, it is a plain page like those of our Website, simply listing the Titles of our new or edited pages as they are published, the last ones appearing at the Top, with a short Description of their content. Interested Readers can easily see the information by clicking on the links. From the readers point of view it is all in their hand, with no need to send out their e-mail. To start being advised of new content one has only to subscribe to the Blog, easily done by clicking on the orange buttons, under the NavBar on the left of every page in the site (www.welding-advisers.com). Yahoo!, Google and MSN offer to include the notice in a personalized page ("My Page") where the RSS feed can be easily added. We urge everyone to play with it and enjoy! Our first article deals with WPS (Welding Procedure Specifications). We detected some interest in the subject from our readers, in the Correspondence we receive, and we are glad to supply the information requested. Next, also per a reader's request, we present some tips for welding thin stainless steel sheets. We hope this will be useful to a larger audience. In the Filler Metal Department we present the website Resources of a few commercial suppliers of electrodes for Flux Cored Arc Welding. This is done to let our readers obtain specific information if needed in their daily practice. An article on Corrosion in Weldments follows, with information on causes and effects. It appears that, in spite of widely available information of the effects of welding on stainless steels, users are time and again surprised by the poor performance of the expensive materials they contributed to spoil by careless decisions. For the Site Updating we present our Page of the Month, dealing this time with Flux Cored Arc Welding Tips. It is generally agreed that this successful process could contribute to increased productivity with expanded use where appropriate. In the Contribution we present a summary of successful applications of a process described as the most significant welding innovation in the last fifty years. We refer to Friction Stir Welding, now reaching out new and different industries. Other departments are included as usual, to fill curiosity and needs of whoever is interested. We ask our readers to let us know how can we provide needed information to help them in achieving practical results. Write us by e-mail. Click to send us Your Questions and Feedback.
2 - Article: Welding Procedure Specifications The subject of this article was previously exposed briefly in our page on
Welding Procedures (Opens a new page) that gives an overview of the matter. We would like to add here useful details and links to provide interested readers with further know how and information. A Welding Procedure Specification is a detailed document that specifies the required welding conditions, including variables and parameters involved, for a given application, for the purpose of assuring consistency of operation in welding. It is required to make sure that the process and technique employed will:
All accepted welding processes are covered by codes or specifications. The Welding Procedure Specifications represent the detailed instructions that workers must observe when realizing the specific welding operation for the given structure. The adequacy of such a procedure to meet certain minimum requirements of safety and stability is demonstrated by its qualification, consisting in verifying that the welded joints produced according to the procedure, meet in fact the prescribed requirements. The formal document recording the welding conditions (per WPS) and the results of the qualification tests is called a Procedure Qualification Record (PQR). Both documents must be signed by authorized employees, dated and made available when required to those in need to know. Although it is recommended that any shop prepare WPS for every job, to control internally the quality of weldments and the performance of different welders, in most cases the establishment of such a document is a requirement of the regulating authority for approval and endorsement of many types of welded construction. In general the applicable Code is spelled out in the Purchase Order. Different Codes, covering welded constructions in one of a number of application types (like boilers, bridges, buildings, cranes, piping and pressure vessels), are issued by various originators (voluntary professional associations, technical societies, trade associations and governmental agencies) but are then made binding by law and enforced by appointed authorities in charge of the well being of people and enterprises. The Codes represent a distillation of common knowledge and engineering expertise accumulated over the years and believed to be a proper guarantee against human errors and fabrication deficiencies. As such the Codes are frequently updated according to recently acquired insight and technological progress. Different or International Codes for the same broadly described application, may stress variously their test requirements. Generally however a procedure approved for a Code will be easily qualified for another one by supplementing the testing as required by the new one. A first type of WPS will include broad and general indications that apply to all welding of a given kind on certain metals. Such a document provides the manufacturer with flexibility to change selected parameters within established limits and still meet code requirements. The other type is much more descriptive and provides details of specific base metal, thickness and joint design. It is used to control repetitive welding operations. The amount of detail required from WPS is essentially established by Code requirements but also high quality work may suggest the good practice of writing detailed procedures for documentation and control. At a minimum the document should include in sufficient detail the description of the welding process with its parameters ranges and a sketch illustrating the joint design and the welding technique to be used. The variables to be specified in the document are requested by the applicable code. Some codes distinguish between essential or qualification variables, strictly constrained within given limits, and other parameters whose values can be varied as convenient. Among the first are:
Nonessential variables can be left undefined, unless changes of any of them might require adjustment of essential ones outside their approved range. In that case nonessential variables must be specified and maintained. In case electrode size (sometimes described as nonessential variable) is changed, electrical parameters are going to change: if the authorized range is exceeded then the substitution cannot take place. Certain Codes, like AWS D1.1 - Structural Welding Code - Steel, accept the use of prequalified joint welding procedures. This is based on reliability record established with certain proven procedures. The application of these does not relieve the manufacturer from writing the proper documents and from using sound judgement in their application. AWS Structural Welding Code - Steel A complete presentation of this subject is available in Chapter 15 on "Qualification and Certification" of the AWS Welding Handbook, ninth edition, Volume 1 from page 638 to 681. Sample Forms of the proposed documents are presented. AWS Welding Handbook Whenever the properties demanded from a welded construction cannot be met with an existing and available WPS, a new and improved one has to be developed and its qualification must be secured before proceeding with the welding job. All welders engaged in work with WPS must have passed required Welder Tests to demonstrate performance qualification, and obtained Certification for the processes involved, by an Independent Agency or Accredited Test Facility. If you look for specific WPS as examples to copy or adapt, you could browse the LANL Welding Procedure Specifications archive at A number of Standard Welding Procedure Specifications, covering different materials, thickness ranges and processes were developed by the American Welding Society (AWS) and the Welding Research Council (WCR). They are available to interested manufacturers and can be used as an outline to prepare different documents in case they do not cover exactly the procedures sought. The list of AWS Standard Welding Procedures Specifications can be seen online at page 22 and 23 of the AWS 2006 Catalog, downloadable from
3 - How to do it well: Welding thin Stainless Sheets Q: Gas Tungsten Arc Welding thin sheets of austenitic stainless steel type 304L results in unacceptable distortion. What can be done to improve results? A: Compared to carbon steels, austenitic stainless steels have higher thermal expansion and lower thermal conductivity: these are the main reasons contributing to unacceptable distortion. GTAW is a proper process to weld such jobs but, due to the low current employed, manual operation may be difficult to control. Better results could be obtained by mechanized welding. Other precautions include proper fixturing, pulsed current if possible and step welding. Good cleaning and preparation are always important. Constant current, non pulsed power supplies of drooping-voltage characteristic are used with direct current straight polarity, electrode negative. Pulsed current may provide better weld control to avoid burn through. Most widely used nonconsumable tungsten electrode type is that with 2% Thoria (EWTh-2). High frequency should be used to start welding and to avoid contamination due to electrode contact with the weld pool. Argon is used as the shielding gas. The conical electrode tip can be ground with different apex angles. A narrow angle of about 15 to 30 degrees tends to produce a relatively wide bead with shallow penetration. A larger angle of 60 to 75 degrees would give a narrow bead with increased penetration. Thin gage stainless steel sheet should be properly clamped and aligned to avoid buckling. Fixturing of the abutting edges, with no gap for thickness up to about 1 mm (0.040"), is done with copper chill bars, usually nickel plated. The backside chill bar includes a groove, placed under the joint, where argon can be provided to prevent backside oxidation. The two front side chill bars should be beveled to make room for the torch. Good contact between stainless and copper bars helps in removing excessive heat. If the clamp down bars are very close to the line of welding and held with considerable pressure, a compressive force will act on the seam while welding, as lateral expansion is prevented. The upsetting force will reduce shrinkage stresses and distortion. Tack welding should be provided at close intervals but with a proper sequence that will maintain alignment. Pulsed current if available may be advantageous in reducing heat input. Current is pulsed at regular intervals between a background level and a peak level. A stable arc is more easily maintained. In case of long seams, short welding stretches should be performed, at relatively far locations, taking care to let the joint cool down between welds. The start and stop of each weld and the tack welds should be ground to eliminate possible flaws in those places. Implementing most of the above precautions should result in weldments of reduced and acceptable deformation.
4 - Filler Metal: FCAW Commercial Supplier Resources A short article on Selection of Electrodes for GMAW and FCAW was presented in Practical Welding Letter issue No. 6 for February 2004. Click on PWL#06 (Opens a new page). A short note on FCAW Electrodes was presented in Practical Welding Letter issue No. 18 for February 2005. Click on PWL#018 (Opens a new page) for seeing it. As remarked elsewhere, in our page on Flux Cored Arc Welding Tips (Opens a new page), the complexity of the FCAW AWS Electrode Classification makes the selection difficult, except maybe for the simplest cases. Furthermore differences in performance among manufacturers and slow progress providing better results from newer products, suggest to contact manufacturers before starting an important job. The purpose of this note is to provide addresses for getting, from electrode manufacturers, detailed recommendations on the best selections, suggested parameters and techniques, and the opportunity to test practical applications. Testing is the best way to evaluate the suitability of the proposal and to judge such items as weldability, fume level, welders comfort, arc stability, final weld appearance, ease of slag removal, weld quality and weld deposition rate. We are only presenting here those manufacturers that we could easily locate through a short search on the Internet. We apologize, knowing that many more, including important ones, are missing from this list. We are ready to update the list if qualified manufacturers will provide us with relevant links. But we urge our interested readers to deepen their own search with other suppliers they know and trust, and to compare the service level they can get. The documents viewed can generally be explored in depth by use of the proposed links, from one page to the next, depending on the specific interests of the reader. The longer addresses should be copied and pasted in the browser in a single line without spaces (and ENTER).
5 - Online Press: recent Welding related Articles From the Fabricator: Guidelines for tungsten electrodes From The Welding Institute: From the Welding Technology Institute of Australia: From Plastic Technologies:
6 - Terms and Definitions Reminder Age Hardening represents a microstructural modification due to precipitation of constituents (phases) occurring naturally at room temperature with time or artificially under controlled heating for shorter times at temperature. It generally results in hardness increase and ductility decrease. Hardening by aging occurs usually after rapid cooling (quenching) from solutioning temperature or cold working. Anion is a negatively-charged ion, which has more electrons in its electron shells than it has protons in its nuclei. It is attracted to anodes and migrates through the electrolyte toward the anode (positive terminal) under the influence of a potential gradient. Base Metal is commonly referred to the metal to be brazed, cut, soldered, or welded. It is the material of the element to be joined or dismantled by the selected process. After welding, that part of the metal that was not melted. Buildup is a weld or thermal spray surfacing variation in which surfacing metal is deposited to restore the worn out or mismachined dimensions to the original or required value. Cold Cracking is a type of weld cracking that usually occurs after solidification is complete. Cracking may occur during or after cooling to room temperature, sometimes with a considerable time delay. Exhaust Booth is a partially enclosed volume with mechanical aspiration designed to remove fumes, gases and particles from the space where welding is performed. Melt-through represents the complete joint penetration for a joint welded from one side. It is also an unacceptable defect if a hole is left in the weld root because of inadequate welding technique. Slag is a nonmetallic product resulting from the mutual dissolution of flux and nonmetallic impurities in certain welding operations. It protects the weld bead from air contamination and is designed generally to be easily removed after cooling down.
7 - Article: Corrosion of Weldments It is known that corrosion phenomena can originate from differences or heterogeneity of composition that occur within various scale ranges. While wrought materials display a high degree of uniformity, fusion welding introduces regions with modified or different microstructures. The fusion zone represents a region where the chemical composition is a complex result of different proportions of base metal and filler materials mixed together. Compositional difference causes a galvanic couple that can influence corrosion processes near the weld. At a more subtle level one may find microstructural segregation occurring during solidification. At the boundary of the fusion zone two regions have been described. One is called the partially melted zone, next to the chilled, unmixed zone of material fused and promptly solidified without compositional modification. The heat affected zone (HAZ) represents a space where each location underwent a unique cycle characterized by maximum temperature and a definite cooling rate. The results of microstructural transformations depend on base metal composition and characteristics of thermal cycle. All the rates of change can be referred to as gradients even at microscopic level, and may influence corrosion susceptibility depending on their importance and on the local environmental conditions. The specific forms of corrosion that can occur in weldments include galvanic corrosion, pitting, stress corrosion, intergranular attack (IGA) and hydrogen assisted cracking. Good welding design should consider ways and means to control and limit development of corrosion in weldments. In most aluminum alloys, weld metal and HAZ become more noble in relation to the base metal, and are therefore immune from corrosion in the weld in salt water environment. Other alloys, typically 7005 and 7039, form narrow anodic regions in the HAZ, and are consequently prone to localized attack. The common practice of field repairing heavy machinery elements made of high strength low alloy steels with austenitic stainless steels, mainly because of their ductility and resistance to cracking, leaves a cathodic stainless steel in contact with the steel. If the environment is corrosive, hydrogen can develop at the cathodic boundary and cause stress corrosion cracking in the high strength steel, especially in presence of a high residual stress field due to the welding. Stainless steels are often perceived as being immune from corrosion in any and every environment and condition. Unfortunately it is not so, especially if welding or other thermal processes are undertaken without proper precautions. An explanation of basic facts pertaining to austenitic stainless steel behavior is presented in our page on Stainless Steel Welding. Sensitization due to welding, also called weld decay, represents the destructive process of the corrosion resistant properties originally present in certain austenitic stainless alloys like type 304. Heating of these materials in a temperature range between 650 to 900 0C (1200 to 1650 0F), if the carbon content is not extremely low and if the time at temperature is sufficient, will affect two strips of metal from both sides of a weld bead, causing the formation of chromium carbides along grain boundaries. The consequence is the formation of localized galvanic cells, active in the initiation and progression of the corrosive process. The chromium content results depleted (impoverished) in the volume affected, because the amount sequestered by carbon to form carbides is no more available to provide the protective chromium oxide layer to the metal. When the available chromium content drops below about 12 weight percent level, responsible for the original passive and corrosion protective qualities of the material, the regions affected are now prone to intergranular attack (IGA), they are no more corrosion resistant. To avoid the weld decay one should stay clear of regular stainless steels like type 304 (if welding is considered) and one should instead either select:
One could also perform a new solution treatment of the weldments at a sufficiently high temperature to put again the carbides into solution, followed by rapid cooling (quenching). Unfortunately this solution is seldom practical because of heavy scaling (in an air furnace) and of the unacceptable deformations occurring in the process, except possibly in case of very small welded parts. Austenitic stainless steels are known to be prone to the formation of hot cracking if a sufficient proportion of ferrite (delta ferrite) is not included in the weld metal. It is generally agreed that optimal ferrite content in austenitic stainless steel should range between 3 and 8% of volume in the weld deposit. Ferrite control is usually achieved by adjustment of composition, depending on the filler metal used and on its mixing proportions with the base metal, according to specially prepared diagrams that give the amount of ferrite present as a function of the Nickel equivalent vs. the Chromium equivalent. The concept of equivalence was proposed to take into account the influence of austenite-forming elements (like Nickel) as opposed to that of ferrite-forming constituents (like Chromium), but considerable disagreement is still apparent among researchers. Nevertheless this approach has practical usefulness. These diagrams originated from Schaeffler's first attempts (1949) to predict weld microstructure from composition, were later refined by DeLong (1973) and further improved by the Welding Research Council (WRC) in 1988 and 1992. The actual ferrite content can be also evaluated by experimental procedures. Pitting is a form of localized corrosion due to breakdown of the thin passive chromium oxide layer. While pits can develop in weld affected areas or with non homogeneous concentration of attacking solution, its appearance is more often the result of damaging particles, due to manufacturing operations, not removed from the surface. Passivation is a good practice that contributes to clean the surface and to form the protective oxide film necessary to avoid pitting. It should always follow other manufacturing operations. Stress Corrosion Cracking (SCC) can develop in weldments due to corrosive conditions, susceptible microstructure and residual tensile stresses. Any precaution (low heat input) or post weld treatment capable of reducing residual stresses will substantially decrease the danger of this form of failure. Modification of the environment to lower chloride and oxygen content will also contribute to reduce SCC. The observation that the presence of about 50% ferrite gives optimum stress corrosion resistance, brought to the development of Duplex stainless steels whose mixed microstructures were designed to minimize SCC. Hydrogen damage may develop due to its presence together with applied or residual stresses. The combination of fracture sensitive microstructures like brittle martensite and elevated hydrogen content may lead to failure. Precautions must be applied to avoid the introduction of hydrogen into the weld. This is done by thorough cleaning of the surfaces to be welded, by suitable dry storing conditions for consumables capable of absorbing moisture (or by drying them if suspect) and by post weld heat treatment intended to ease the natural diffusion of absorbed hydrogen to the outside. Among other advice usually to be considered to minimize corrosion, besides cleanliness, dry conditions, post weld treatments and suitable materials one should consider weld design and practice to avoid underbead gaps or crevices that trap harmful solutions. The weld surface finish should be smooth, clean and, if stainless, passivated for best corrosion resistance.
8 - Site Updating: Flux Cored Arc Welding Tips The Page of this Month is devoted to the above process, known for being potentially one of the most cost effective means capable of exceptionally high weld deposition rate. This is the fourth of the "Tips" pages: at least two other of these pages are planned at present. As such the said process should be considered whenever its application could provide increased productivity, reducing manufacturing costs. The new page includes fundamentals of the process, along with information that may help in optimizing selection of electrode types and of parameters. To read the page click on Flux Cored Arc Welding Tips (Opens a new page). You could also look through our Site Map (Opens a new page) to find the subjects you wish to read about. An easy way to find out which are the most recent web updates is to look up in the Site Blog page from the button on the NavBar. The last update is the topmost, other (older) items follow in succession. As already advised elsewhere you can also subscribe to this RSS Feed, to have the new titles presented to you as they appear, by clicking on the orange button in every site page under the NavBar. Send us by e-mail Your Questions and Feedback.
9 - Short Items 9.1 - Confocal Microscopy, or more exactly Confocal Laser Scanning Microscopy permits high resolution blur-free imaging of thick biologic or living samples in their whole volume. Images are scanned point by point and then reconstructed by a computer. The reflected light from the sample is passed through a pinhole that effectively blocks all light originating out of the focal plane, however slightly. Therefore the images are much sharper than those obtained from usual microscopy. By moving the focal plane to different positions it is possible to assemble optical slices, later reconstructed by computer in a composite 3D image. 9.2 - Indentation Hardness is the usual type of hardness test used in applied metallurgy, in which a pointed or rounded indenter is pressed into a surface under a substantially static load. Numerical values used to express indentation hardness are not absolute physical quantities, but depend on the method, the indenter and the hardness scale used to express hardness. 9.3 - Mechanical Metallurgy is the science and technology dealing with the behavior of metals when subjected to applied forces or loads. It deals with resistance, deformation and failure of metallic materials. 9.4 - Net Shape, as referred to castings, forgings or powder metallurgy parts, is the manufactured shape with special provisions to conform closely to specified dimensions. Ideally such parts require minimal secondary machining or none at all. 9.5 - The Peltier effect is the reverse of the Seebeck effect: the creation of a heat difference from an electric voltage. It occurs when a current is passed through two dissimilar metals or semiconductors (n-type and p-type) that are connected to each other at two junctions (Peltier junctions). The current drives a transfer of heat from one junction to the other: one junction cools off while the other heats up. The effect is often used for thermoelectric cooling. 9.6 - Spheroidal Graphite acquires the spheroidal shape with a polycrystalline radial structure by adding cerium or magnesium to the melt. The transformation is promoted to obtain ductile or nodular cast iron with improved properties relative to gray cast iron displaying graphite flakes.
10 - Explorations: beyond the Welder Pollution for export? Is there a decent Way to break up Ships? Toxic warship Clemenceau turned back The Fatal Legacy: Waste and Contamination New Jersey Artificial Reefs Overview
11 - Contribution: The amazing Success of Friction Stir Welding A remarkable Success Story on Welding is outlined in three articles in the March 2006 issue of the AWS Welding Journal. It is a tribute to the efforts and ingenuity of all those that dedicated imagination and hard work to the development of this all important process. FSW is an innovative solid state welding process, different from whatever had been known in the past and used for decades. In only fifteen years it made the transition from a Laboratory curiosity to the preferred way of joining Space Structures with valuable spin off developments in many manufacturing industries. A short description can be found in TWI article The first article outlines developments and achievements. The process was invented in 1991 by The Welding Institute (TWI) and is claimed as the most significant recent development in joining. Much Research and Development work was invested as the potential of the innovation was recognized early. Time and again it was proven not only that joint properties and performance were much improved relative to competing processes, but also that production costs were reduced, and welding speed increased substantially. Most of its remarkable properties stem from FSW being a form of solid state joining process, realized without melting, on many different materials. Higher strength, increased fatigue life, lower distortion, less residual stress, less sensitivity to corrosion, and essentially defect-free joints compared to fusion welding are among its important advantages. It has been estimated that huge savings in energy and in emitted pollutants could be achieved if only a fraction of present day arc welding could be converted to FSW, together with remarkable economic benefit to industries and countries. Restraints to wider implementation of FSW in additional industries seems due to lack of industry accepted standards and specifications, lack of design guidelines and allowable stresses, lack of informed professionals and high cost of equipment, but progress is anticipated for the near future. Many research programs are currently running in several academic institutions, with or without governmental assistance, to extend the knowledge base and to prepare for more diffused applications. Much research and testing is devoted to develop special shapes and materials for tools for special applications. Both robotic multi functional systems and lower cost single purpose equipment are being designed. Hybrid systems are investigated with additional energy introduced as heat by electric resistance or laser application to improve results. Production is ongoing on various projects in automotive, aerospace, naval and industrial applications, different forms of spot welding have been introduced. Joining of plastics is performed successfully by Friction Stir Joining. Surface conditioning and repair of castings, removal of surface defects in weldments, application of wear resistant ceramics to aluminum or cast iron surfaces are successfully implemented by Friction Stir Processing. The outlook is bright for further innovations and application of FSW and derived technologies in all areas of industrial manufacturing. The second article outlines the remarkable aluminum FSW advantages vs. fusion welding. In particular quality is outstanding as already pointed out above. Furthermore this process allows welding of aluminum alloys (2xxx and 7xxx series) considered unweldable by regular methods involving melting (except resistance welding), with acceptable corrosion resistance results. Costs of FSW are lower than competing processes for long continuous welds or for high production applications. FSW permits high welding speed, and thick welds are performed in a single pass or with dual head setups from opposite sides simultaneously. Equipment and fixture costs may still be high but, if suitable production applications are selected, the overall expenses are less than for the alternatives. The advantage even grows when saved accessory expenses are taken into account, like preparation, that is simple and rapid, absence of consumables, reduced or absent deformations and limited if any finishing work. It has also been proved that the process permits welding of aluminum with dissimilar materials. The third and last article reports on initial introduction of FSW at NASA, and on current development activity with technical details, applications and results. The use of an innovation, the self-reacting tool, is presented, with a discussion of its advantages. Repetitivity of weld properties is assured once optimized parameters have been established. Nondestructive testing techniques of higher sensitivity are being researched and developed to detect ever smaller flaws, and mathematical simulation tools are investigated to better describe and understand the phenomena involved in the process and to design more reliable tools. New space vehicles to be built for moon exploration and beyond are now on the drawing boards, with welding engineers expert in FSW, planning their part in the Integrated Product Team. Further developments now studied include preparing the manually held means to perform construction and repair in space, using of course FSW. Ultrasonic Stir Welding and Thermal Stir Welding are yet other new concepts being now researched at NASA for possible future applications. NASA is said to encourage partnership with private enterprises for the joint development of technologies. To keep abreast of welding technology advancements, interested readers are urged to read in full the articles, summarized above, in the March 2006 issue of the Welding Journal.
12 - Testimonials From: "M/s.Hyma Plates & Vessels" (e-mail address withheld for security) Thank you very much for your valuable information on welding.
On Thu Mar 02 08:59:26 2006, the following results were submitted from the
"Form 5" on welding-advisers.com: Mary Miani
Thanks,
13 - Correspondence: a few Comments A reader sent us two related questions, giving two different e-mail addresses. Unfortunately our answer bounced back from both, as the addresses were for some reason incorrect. We have no other mean to reach him, it is not our fault. As it happens correspondents sometimes thank for the information received. They are welcome. I would much appreciate if I could get their comments on the results they obtained by applying my advice. This is however asking for too much, it seems. Readers are asking for free resources and books on welding. I am going to put together a page, listing a few addresses of the material available at no cost from the Internet. When it is ready you will be advised in these pages.
14 - Bulletin Board 14.1 - First Int'l Congress on Ceramics 14.2 - 11th Beijing Essen Welding & Cutting Fair 14.3 - We recommend that you stay tuned to the constant updates offered by our Website Host SiteSell.com. It is quite simple to do that. Go first to their Home Page by clicking on Site Sell. (Opens a new page). Once there, before even browsing down the page, click on the orange button in the top left corner. That will give you a chance to subscribe at no cost to one or more of their RSS Feeds in total security, without giving out your e-mail address. All of the updates will then be easily reachable to you at your convenience according to your preferences. We are confident you will find interesting matter for your thoughts and actions. Just try, you can always unsubscribe later. Good luck. See you next time... Copyright (c) 2006 by Elia E. Levi and welding-advisers.com, all rights reserved
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