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PWL#093 & 093B - Virtual Welding Training, Stress Relieving Test, New Chromium Free Filler Metal May 02, 2011 |
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| We hope you will find this Letter interesting and useful. Let us know what you think of it. Virtual Welding Training, Stress Relieving Test, New Chromium Free Filler Metal for Joining Austenitic Stainless, Testing of Thermal Sprayed Coatings, Problems with Alloy 20 Overlays, Abrasive Blast Cleaning, Bend Testing and much more...
and Mid May Bulletin
DON'T USE REPLY to send us your messages! Use Contact Us instead. Please be advised that the Mid Month Bulletin is now integral with the regular PWL publication. You will find it further down, past the end of this Practical Welding Letter. Important AnnouncementFor assembling at no cost your own Encyclopedia Online,
1 - Introduction 2 - Article - Virtual Welding Training 3 - How to do it well: Stress Relieving Test 4 - New Chromium Free Filler Metal for Joining Austenitic Stainless. 5 - Online Press: recent Welding related Articles 6 - Terms and Definitions Reminder 7 - Article - Testing of Thermal Sprayed Coatings 8 - Site Updating: Abrasive Blast Cleaning, Bend Testing 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contributions: Problems with Alloy 20 Overlays 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board (Sponsored Links)
1 - Introduction This 93rd issue of Practical Welding Letter for May 2011 opens with a review of independent developments of virtual reality welding training equipment. The variety of the proposed solutions testifies to the spreading belief that better and more economic training can be provided to trainees by virtual rather than real training. Despite the enthusiasm of the developers it seems that the prevailing opinion among users be more equilibrated, recognizing a place to the new technology. It is admitted that reducing the amount of time to be dedicated to a full course could provide a sizeable economy. But true traditional training cannot be skipped at all. Repeated requests asked for information on stress relieving tests. Tests of this type do not exist, except that experimental stress analysis can always be conducted if needed. In normal industrial settings, it is probably sufficient, to satisfy quality requirements, to keep track of the stress relieving operations performed. Then a study is reported on research conducted to provide a suitable Chromium free filler metal to be used for welding austenitic stainless steel of Type 304L. The effort was in response to the concern for welders' health, if breathing fumes generated when welding stainless steels. Although the research provided an acceptable filler metal based on Ni-Cu system, it remains to be determined if this is the best and most economic way to meet the new law requirements dealing with permitted fume level in welding shops. Possible different solutions are mentioned. Readers are invited to express their opinion on the matter. Routine Testing of Thermal Sprayed Coatings in production follows strict procedures that were developed as a proven way of assuring meeting accepted requirements. A short review provides the essential points. The last contribution published in this issue was provided by a longtime friend and experienced welding engineer, who chose to report on a questionable production failure whose reason could not be determined with any confidence. The author asks our readers to provide their best suggestions as to the presumable cause of the reported mishap they may think of. I would like to strongly encourage whoever may have a hint, to let us know it. I also publish the kind comments on the subject from an expert whose opinion I sought. The pages of the month, reported as expected in section 8, refer to Abrasive Blast Cleaning, a quite common set of processes of various energy and capability, designed to remove usual contamination found in industrial metal manufacturing, and to Bend Testing, a most useful class of simple and effective methods capable of separating good welds from questionable ones. The other departments can be readily found at their regular place. Enjoy your reading and let us have your feedback and comments using the Contact Us Form. The references to online resources, assembled in this issue for the Mid Month Bulletin, that follows the regular issue, are devoted to Thermal Spraying. They should be quite informative.
2 - Article - Virtual Welding Training Training to acquire manual skills like those required for arc welding takes time and costs substantial money. It also consumes energy and produces scrap and fumes in a dangerous environment. However, given the already felt pinch in skilled workforce needed the world over in the near future, there is a strong incentive in trying to find economic ways to provide the required experience while limiting time and expenses. One successful way to achieve just that includes the development of virtual reality trainers, capable of giving to trainees actual hands-on experience of manual dexterity without striking an arc. This at least is the theory. The origins can be related to electronic games and to NASA development of Flight Simulators. The purpose of virtual reality welding trainers is to recreate the welding experience without actual welding. It employs the manipulation of an adapted torch, it measures the actual movements and distances, it simulates the physics of welding and reproduces visual scene and actual sounds. It is believed that virtual training provides valuable experience to trainees and that it helps to reduce the actual training required. Many safety, economic and ecologic advantages are attributed to virtual training. It is out of question that virtual training cannot be substituted for traditional hands on training, but it may reduce time and costs up to certification. It will probably spread to more schools as price continues to decrease and as more experience is gained. A still lacking independent comparative evaluation of the different solutions proposed until now, could contribute to clarify current issues and establish development goals to increase usability. Simulators were built by: 1 - VRSims for EWI (Edison Welding Institute)(www.ewi.org/). 2 - Lincoln Electric offers VRTEXTM 360 The VRTEX 360 will be on display, for hands-on use, at a few welding conferences in 2011. 3 - Fronius Virtual Welding Training Simulator 4 - CS WAVE 5 - Virtual welding equipment on the Internet A Technical Conference "Welding Trainer 2010 and the Future of Education" was held on 8-9 September 2010 in Duisburg, Germany, organized by GSI (German Welding Institute). A Presentation, including 17 frames on Virtual Welding Trainers, is
an interesting exposition of Barriers in Developing. Readers having actual experience with welding training simulators are invited to kindly share their comments with this readership.
3 - How to do it well: Stress Relieving Test Recent queries addressed stress relieving test. As the specific conditions referring to the cases confronting the inquirers are not known in any details, the answer here refers to general cases. There is no practical mechanical test capable to determine, by measuring a given property (like hardness), if the process was applied or not. Therefore in case of doubt if the process was applied or not, the only resort would be to make it again. Whenever stress relieving procedures (see Stress Relieving) are specified in engineering requirements, there must be an established record keeping method that certifies for every workpiece submitted to this procedure, that the process was indeed done as prescribed. The record, normally written and signed by an authorized inspector, must define the item, by serial number if necessary, the facility used, the parameters (date, time, temperature), the operator, and include furnace graphs if available. Special remarks like interruptions, must also be included. As sometimes stress relieving operations may cause deformations, dimensional checks should be performed to make sure that the items are still acceptable. Normally hardness test are not required except in special cases. If stress analysis is required for development programs, it is not generally a routine inspection, and will be performed on experimental basis. Steel parts undergoing stress relieving at elevated temperature may develop a surface scale that should be removed before applying paint, by such a process as specified in engineering drawings.
4 - New Chromium Free Filler Metal for Joining Austenitic Stainless. The dangers of hexavalent chrome in welding fumes produced by welding austenitic stainless steels were briefly summarized in the article published (7) in Issue 88 of Practical Welding Letter for December 2010. Click on PWL#088 to see it. Following studies that addressed the dangers of carcinogenic products like Cr(VI) present in stainless welding fumes, the permissible exposure limit (PEL) was drastically reduced by law in the USA. The Welding Research article published at page 63-s of the April 2011 issue of the Welding Journal, reports on a study toward the development of a new chrome-free filler metal that was initiated to provide a possible solution likely to meet the new required limits. The study reports, among other facts, that the contribution of chromium evolving from base metal is four times less than that produced by consumable filler metal. The research started considering, as possible replacement, materials derived from the family of alloys of nickel and copper (known as Monel). Several iterations were performed to develop filler metals of improved properties until an acceptable composition was finalized for performing all required testing. The proposed CuNi chrome-free filler metal, developed to reduce Cr(VI) in the welding fumes generated while welding austenitic stainless steel of Type 304L, was evaluated by assessing the following characteristics:
Only strain to fracture testing revealed threshold strain significantly lower than that of type 304L. It will probably take more time to see if this new composition will be accepted in the industry for welding austenitic stainless steels. Interested readers are urged to seek the original article indicated above. The developments pursued in this study were successful in achieving the goals established in advance and have progressed knowledge and understanding of welding austenitic stainless steels. It is interesting that no initiative is reported considering the feasibility to insulate completely the welders from the fumes by either performing welding within a separate enclosure or by enveloping the welder into an insulating garment. Both applications already exist for underwater welding. Cost assessment exercises could prove if solutions of this kind might be worth of being promoted. Furthermore the development of enclosed welding robotic cells for manufacturing stainless welded structures, might possibly reduce the urgency of costly initiatives devoted to the development of special chromium free consumables. Readers comments are welcome.
5 - Online Press: recent Welding related Articles Melting point depression of nanostructured filler metals for brazing applications Advanced A-TIG Welding The Future Of Welding In Manufacturing The Investigation of Laser Lap Welding Process on High-Strength Galvanized Steel Sheets Connect March/April 2011
6 - Terms and Definitions Reminder Edge Weld Size is the weld metal thickness measured from the weld root. Flowability is the ability of molten filler metal to flow or spread on a metal surface. Groove Weld Size is the sum of the joint penetration in a groove weld, from both sides. Hand Shield is a hand held protective device, to shield eyes through a filter plate, face, neck. When replaced by a welding helmet worn on the head, the hand is available for additional work like filler metal feeding etc. Induction Welding is a class of welding processes where the heat for welding is provided by the resistance to the flow of high frequency electric currents induced in the joint by suitable primary coils, with or without pressure application. Linear discontinuity has one dimension, the length, substantially greater than its width. Perceived as more dangerous than discontinuity of other forms. Metal Transfer Mode denotes the way the metal is transferred from the continuous filler metal supplied by the torch to the weld pool, in Gas Metal Arc Welding. May be short circuit transfer, globular or spray transfer, depending on welding parameters. Nonsynchronous Initiation is the closure of a resistance welding contactor disregarding the voltage value at that instant.
7 - Article - Testing of Thermal Sprayed Coatings The routine tests employed to determine the acceptability of industrial production lots of thermally applied spray coatings are used essentially as process control devices. By performing the specified tests, the laboratory only assures that the inspected lot meets the required production criteria. The adequacy of the said criteria to guarantee that the application will perform satisfactorily in service as needed, was separately demonstrated empirically during the development work as the functionality and the endurance of the coating in the development item were found to meet the design requirements. This is because there is no practical way to correlate the properties tested on the samples, to the actual conditions occurring in service, which may be quite different. The purpose is to verify that the single lot inspected displays essentially the same characteristics as those that provided acceptable service. The aim is to provide quantitative data readily comparable with the established requirements. Therefore the procedure normally employed needs equipment qualification, according to specific requirements established from previous history of satisfactory performance. The operators must be certified by examining their qualifications, to demonstrate adequate understanding of the process and of equipment operation. Materials used must meet specification requirements. Finally the process has to be qualified by showing that it meets consistently the required properties. The operating parameters used, become then fixed and are recorded. These will be the operating parameters for all future production until authorized changes will be introduced as necessary. The standard tests employed for production lots approval are specified in suitable documents and include one or more of the following:
Additional testing may be required like bend testing, to demonstrate adherence and cracking performance, or Almen testing to measure the amount of residual tensile stresses of the coating on a given standard specimen. Tensile testing should be performed per the following standards or as prescribed: ASTM C633-01 (2008) ASTM D4541-09e1 Apart from the above standard testing, to test the actual adhesion of a thermal sprayed coating to its substrate, there is no better test than grinding, if required. Coatings of poor adhesion will not stand the grinding test. See on related subjects: This Mid Month Bulletin 61, attached to and integral with this publication, is dedicated to Resources on Thermal Spray, available through Links to Internet Sites that provide information likely to interest our readership. The link here above is just an example of what can be found in the Bulletin. Please be reminded that basic information is also available in my page on Thermal Spray. 8 - Site Updating: Abrasive Blast Cleaning, Bend Testing The first Page of the Month reviews Abrasive Blast Cleaning, a whole class of different processes having in common the forceful removal of contaminants by the use of an accelerated flow of abrasive particles directed on the surface of items in need of being prepared for finishing operations. Various types of equipment permit to perform just that, with a long range of abrasive materials, from hard to soft, and with the most appropriate size of particles depending on the application. Although quite straightforward, correct and economic application requires, as always, knowledge and experience. See this page by clicking on Abrasive Blast Cleaning. The second page, on Bend Testing, explains what the test is and what it accomplishes. The proof of its success is that it is probably the only type of test that, while simple in concept and practice, is so powerful and reliable that is being adopted by all codes to qualify procedures and welders. As it is so convincing it should be employed, in my opinion, whenever feasible, as a didactic tool, to give students a practical way to assess by themselves their progress, with an objective pass/fail answer to their doubts and struggles. The page is found by clicking on Bend Testing. To stay updated as new pages are regularly added to the website, please subscribe to the RSS (follow instructions under the NavBar in each page), look at the Site Map, examine the Index Page or review periodically the Welding Blog. You are urged
to inform your friends of this website: they may benefit from the quite extensive information freely available to all readers and they will be able to ask questions that may help them.
9 - Short Items 9.1 - Ferrite is a solid solution of one or more elements in body-centered cubic iron. The solute is generally assumed to be carbon. On some Iron-Carbon equilibrium diagrams, two ferrite regions, (the lower, alpha ferrite, the upper, delta ferrite) separated by an austenite area. An essentially almost carbon-free solid solution in which iron is the solvent, characterized by a body-centered cubic crystal structure. Fully ferritic steels are only obtained when the carbon content is quite low. The most obvious microstructural features in such metals are the ferrite grain boundaries. 9.2 - Grain Boundary, in metal or ceramic, is the narrow zone of transition from one crystallographic orientation to another. Separating one grain from another, the atoms being arranged in different orderly patterns of preferred lattice positions in each grain. 9.3 - High-Cycle Fatigue occurs at relatively large numbers of cycles. Arbitrarily, high-cycle fatigue is considered that occurring at more than 105 cycles to fracture. The dominant component of the strain imposed during cyclic loading in high cycle fatigue is elastic, depending on the properties of the metal and on the magnitude of the nominal stress. 9.4 - Intercept Method is a quantitative metallographic technique in which the desired quantity, such as grain size or inclusion content, is expressed by the number of times per unit length, that a straight line drawn on a metallographic image, crosses boundaries of the feature being measured. 9.5 - Low-Cycle Fatigue occurs at less than 104 cycles to fracture. May be accompanied by some plastic, or permanent, deformation. 9.6 - Nucleus, in the description of atoms, is the heavy central core, in which most of the mass and the total positive electric charge are concentrated. In metallographic descriptions nucleus is the first structurally stable particle possessing an interface with the parent metallic matrix. It is capable of initiating structural change like recrystallization of a phase or growth of a new phase.
10 - Explorations: beyond the Welder The Dead Sea Is Disappearing, but Could Be Saved [Slide Show] How Science Stopped BP's Gulf of Mexico Oil Spill
(4 pages) Fukushima Meltdown May Mean Tighter Rules for Spent Nuclear Fuel in U.S. Watching Climate Change Through a Farmer's Eyes Scientists Urge Greater Protection for Arctic as Ice Recedes
11 - Contributions: Problems with Alloy 20 Overlays 31 Mar 2011 Hello Elia, Over the years I have been happy to share some of our welding success stories. We recently worked with a customer who asked us to provide a weld overlay consisting of UNSO8022(Alloy 20) overlaid on 4.75" thick SA516-70 flanges. The requirement was to weld an overlay that would be finish machined to a height of .188". Unfortunately the overlays did not pass liquid penetrant inspection after we machined the welded surface to the required dimension. As happens occasionally in manufacturing, we were faced with deadline pressure and the decision was taken to produce the overlays at our facility. Our original proposal to our customer was to place a "barrier" layer of ER309L on the steel with the SAW process utilizing Lincoln ST-100 flux. Our customer referred us to an API spec. that directed us to apply the Alloy 20 directly to the steel with no barrier. The customer also suggested we use a Soudokay CrNiW flux. We were also following ASME IX guidelines which require us to have side bends tested and a chemical analysis performed to verify we have indeed achieved an Alloy 20 chemistry. Our first sample failed the chemical analysis. Our spec. required 19.0% minimum Chromium in the final layer. We achieved 19.02% which was much too close for comfort during production welding. Again we achieved a 19.02% Chromium value while we believed 20.0% would be required to give us a safety margin that could absorb the vagaries of
production welding. We used 3/32" diameter ER320LR (Low residual) filler wire, Soudokay IN flux. Kindest regards, Paul Ipolito Note: - Readers are kindly urged to contribute from their knowledge and experience, proposing their own comments. Any answer will be forwarded by me to Paul and published in the next PWL issue.
Note: I publish hereafter the answer, kindly sent to me
by Elia, Special Metals does not manufacture any of the products involved in this work so I can only comment in general terms. The alloy 20 compositions (e.g., 20Cb-3 and 320SS) are known to be sensitive to hot cracking when used as welding products. As a result, alloy 20 and similar materials such as INCOLOY alloy 825 are normally joined by over-matching composition welding products such as INCONEL filler metals 625, 622 and 686CPT. If an alloy 20 welding product were used to overlay a steel component, dilution of the weld with iron from the steel substrate would increase the weldment’s tendency to crack. Thus, the LP indications encountered are not totally unexpected. I am not acquainted with the fluxes you describe. You may want to confirm with the manufacturers that those fluxes are suitable for welding with alloy 20-type filler metals. If a clear LPI of the overlay is required, you may want to consider one of the higher nickel alloy filler metals mentioned above. Filler Metal 625 is commonly used for submerged-arc welding and overlay. Visit www.specialmetalswelding.com for procedures and flux recommendations. If the alloy 20-type filler metal must be used, I would expect better results with a nickel barrier layer (e.g. Nickel filler metal 61) as compared to the 309SS used. Regards, Lew Shoemaker Research & Technology
12 - Testimonials From: Donald Ferguson Thank you very much for your articles. We refer to them often. Don L. Ferguson President
Date: 31 Mar 2011, 04:21:36 PM Enjoy the Newsletter immensely. [...] Tony Rangus
13 - Correspondence: a few Comments 13.1 - Tony Rangus from Bechtel (see above) sent the following comment: "Concerning the article on "Advancements in Flux Cored Filled Metals" [in the last PWL Issue], take note that there are a significant number of operating companies (oil, gas processing, LNG, chemical) that severely restrict the use of FCAW for their Projects and operating facilities. There are some that forbid its use based on one or two bad experiences and others who are stuck in the 1970(s) when FCAW weld filler material manufacturing had significant quality control problems (lack of flux in sections of the wire, poor flux quality). Once you go beyond carbon steels, a lot of folks shy away from FCAW. In addition, fume control is a significant problem, especially in the larger diameter wires when welding with high current densities (> 30 volts with > 350 amps). Gas Shielded FCAW is an excellent process, but convincing some people of that is a real battle." Note: - Readers wishing to add their own notes or comments are urged to do so now by sending an email to Contact Us. 13.2 - Bora Canal from Germany sent new photos of artworks, visible in the page on Welding Art, under the name "100% Stainless Steel".
14 - Bulletin Board 14.1 - JOM-16
and ICEW-7 14.2 - The Prevention of Weld Failures 14.3 - Materials and Processes for Medical Devices (MPMD) Conference and Exposition 2011 14.4 - Conference & Exhibition 14.5 - The SBI! 2.0 Video Tour 14.6 - Visit SiteSell Facebook right now and see for yourself.
Mid Month Bulletin 61 - PWL#093B May 2011 keywords: Thermal Spraying, Molten Metal Flame Spray, Plasma spray, Arc Spray, HVOF
PWL#093B - Resources on Thermal Spray, Molten Metal Flame Spray, Powder Flame Spray, Wire Flame Spraying, Ceramic Rod Flame Spraying, Detonation Flame Spraying, High Velocity Oxygen-Fuel Spraying (HVOF), Cold Spray, Nontransferred Plasma Arc Spraying, Arc Spraying, RF Plasma Spraying, Airborne Toxic Emission Control, Protecting Workers and much more....
Mid May BulletinMay 2011 - Resources on Thermal Spray - Bulletin 61
Important AnnouncementFor assembling at no cost your own Encyclopedia Online, Introduction This Mid May Bulletin #61 is now integral with and appended to the regular PWL#093 publication. The subject of this Bulletin is a collection of Online Resources on Thermal Spray in addition to the website page reachable by clicking on Thermal Spray. Links to the Mid Month Bulletin Pages are listed in the regularly updated page on Welding Resources (Opens a new Window). We urge our readers to Bookmark this page and to subscribe to our Welding Site Blog by clicking on the orange buttons under the NavBar in each Website page.(www.welding-advisers.com) To see Updates, you may also click periodically on the Welding Blog button in the NavBar. The addresses reported hereafter were live and correct at the time of their publication. There is no guarantee that they will always be so, because they are administered by the sources themselves and are under their control. Note: References to articles or other documents are given here in one of two forms. If the links are "live" (usually underlined or otherwise highlighted) they are operated with a click of the mouse. If they are URL's (Uniform Resource Locator), which is the analogue of an address, they begin with "http://..." or "www.". These are not live and must be copied and pasted entirely into the browser (after having selected them with the mouse or otherwise). If they are long they may be displayed in two or more lines. In that case one has to care that the URL be copied completely in a single line without any space, and Enter. If the information is important to you as we hope, you may save the selected pages in a suitable folder on your Computer for easy reference. You are welcome to forward this page to those of your friends who may profit of this information. Note: Disclaimer - The Sources listed hereafter were selected for the information provided. Attention was exerted to refrain from promoting commercial companies. If however occasionally a commercial firm is mentioned, no endorsement or recommendation is intended, only the fact that the information provided might be interesting. Readers are urged to conduct their own search separately and check that the offers meet their requirements. Resources Thermal spraying Plasma transferred wire arc thermal spraying Thermal Spray: Past, Present and Future - A Look at Canons and Nanosplats Some History of the Development of Thermal Spray Thermal-Spray for unique technical and
economic benefits Thermal Spray Coatings (Presentation 31 Frames) The International Thermal Spray Association What is Thermal Spray? (11 pages) High-Performance Laser Coatings for Manufacturing and Maintenance Thermal spraying Surface Finishing Coatings - Thermal Spraying The ABCs of Thermal
Spraying Thermal Spray Basics Introduction to Thermal Spray Processing (12 pages) International Thermal Spray 2012 Conference and Exposition Surface Engineering at TWI (Links) Thermal spraying processes - a guide to best practice Thermal Spray Coating Inspection and Testing (9 pages) Thermal Spray Coatings [See above Disclaimer] Sulzer Metco - Thermal Spraying (24 pages) [See above
Disclaimer] Thermal Spray Special-Purpose Automated Product Inspection Systems Sample of the Specifications (5 pages) Operators Certified Thermal Spray Operator Program Thermal Spray Jobs Health and Safety How to protect workers while thermal metal spraying (4 pages)(Safety Links) Thermal Spraying ATCM - AIRBORNE TOXIC CONTROL MEASURE to Reduce Emissions Thermal spray safety and OSHA compliance (2 pages) Thermal Spraying Safety (3 pages) Accessory Equipment, Products and Services Thermal Spray Cooling Technology [See above Disclaimer] Dust Collectors for Thermal Spray [See above Disclaimer] Acoustical Enclosure [See above Disclaimer] Tapes for Thermal Spray [See above Disclaimer] Thermal Spray Robot Programming [See above Disclaimer] Thermal Spray Coatings Booth Equivalency Unit
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