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PWL#092 & 092B - Comparing Welding Processes, Hard Facing AMS, Flux Cored Filled Metals, RP EB Weld. March 31, 2011 |
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| We hope you will find this Letter interesting and useful. Let us know what you think of it. Comparing Welding Processes, Hard Facing of Austenitic Manganese Steel, Advancements in Flux Cored Filled Metals, Welding Helmet Protection, Vapor Degreasing, Fire Prevention and much more...
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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 - Comparing Welding Processes 3 - How to do it well: Hard Facing of Austenitic Manganese Steel 4 - Advancements in Flux Cored Filled Metals 5 - Online Press: recent Welding related Articles 6 - Terms and Definitions Reminder 7 - Article - EB Welding at Reduced Pressure 8 - Site Updating: Vapor Degreasing, Fire Prevention 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contributions: Welding Helmet Protection 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board (Sponsored Links) 1 - Introduction This issue, the 92nd of Practical Welding Letter, opens hereafter with a short note of comments about how to compare welding processes to find out which one should be chosen for any given application. The hints proposed may give some ideas for further investigation. Then we have a reminder of a few important rules to apply when hard facing austenitic manganese steel implements, for repairing and reconditioning them if severely worn out. The section that follows summarizes an article introducing advancements in flux cored electrodes to be used as filler metals to improve quality and economics of welding important projects like pressure vessels, offshore platforms and other applications. When a large investment in time and labor is required, it usually pays to study attentively the alternatives. The right filler metal for an expensive application may improve productivity and bottom line. Some testing may be all that is needed to demonstrate the achievable advantages of suitable selections. Another article summarizes the development work performed by TWI for adapting Reduced Pressure Electron Beam Welding to large fabrications made of thick components. By providing local vacuum only at the point of welding, the development circumvents one of the most disturbing hindrances of the process, namely the need to enclose the whole structure in a vacuum chamber. This requirement simply cannot be satisfied economically for large constructions. A kind contributor sent a nice article on welding helmets protection. A fresh point of view that may help in adopting protective measures as a constant habit to be followed at all times. The Pages of this Month deal with two subjects. One, on Vapor Degreasing, should be reviewed urgently by anyone operating such units, because of new compulsory requirements being enacted. The other, on Fire Prevention in Welding and Cutting Operations, should be reviewed from time to time to ascertain compliance with all rules. References to online Resources on this subject are appended to this PWL publication as Mid April Bulletin #60. Make sure to see them by scrolling down, beyond the end of the regular part of this issue. The other departments can be found at their usual place. Readers are invited to send their feedback, and possibly also contributions, short notes on real stories that can interest this audience. Let us have your comments using the Contact Us Form. 2 - Article - Comparing Welding Processes The selection of the most suitable Welding Process, for any given application, starts with a thorough review of Engineering drawings and of Quality requirements. That is why I always look with suspect at some of the inquiries I receive, where it seems as the process is already selected, without proper investigation of all the aspects of the problem. In principle the best process (although I strongly object to the use of this qualifier, lest it be misinterpreted) in any given circumstance, is that which provides all the engineering and quality requirements at the least possible cost. There are however other considerations, like urgency or expediency, that may override the principle, provided the responsible person is aware of the consequences of the decision. I would say that one of the following two cases may present itself. The most common occurs when one needs with urgency (and when are not we in this condition?) a suitable solution for solving one specific problem only once. It may be for an urgent repair or for an urgent implement needed for a short time. The other case is when a complete production line has to be set up to work satisfactorily for a long time. Obviously in the first case the importance of the immediate execution takes precedence of any cost considerations, provided the solution is adequate (otherwise it is not a solution). In the second case, once the quality requirements are assured, the cost per weld unit is the main worry. Here not only a thorough study has to be completed, but practical evaluation through testing may be required, to verify the assumptions and to collect actual data. One such study performed as an exercise can be found in the following online publication: It may be interesting to go through this example to get an idea of the alternatives considered and of the criteria used for comparing performance. When dealing with a repair situation it is important to study the case in depth before actual welding. This is because, if the material or the condition of the item are not known with certainty, there is a serious chance not only not to repair it, but even to damage it more to the point it is completely destroyed beyond repair. See on this subject, our page on Repair Welding. In any case when attempting to select suitable welding processes, one should always start from the beginning, that is from the most complete knowledge of the materials involved. It is not enough to know it is steel or aluminum, because the important characteristic is here the weldability. It should be known to whoever takes the responsibility of welding something that certain materials are difficult or impossible to weld: in short, unweldable. There is possibly a shortcut to find out the suitable process for a given application. One can ask Requests for Quotation (RFQ) from a number of reliable sources and then investigate by which process they intend to perform the job. The ensuing discussions can be most informative. For example someone may offer to perform Electron Beam Welding instead of some other traditional process. Even if not absolutely required because of compelling reasons, in certain situations it may give economical advantage, to be further investigated. The fact that something was always done in a certain way is not a guarantee that it is the best process. New ways should always be considered, but before scrapping the older facilities one should be sure that the new ones supply comfortably what is needed. 3 - How to do it well: Hard Facing of Austenitic Manganese Steel Austenitic Manganese Steel contains 1-1.4 %C and 10-14 %Mn. This composition stabilizes the austenitic structure that is maintained even upon rapid quenching from high temperature. However, upon reheating to a moderate temperature, the material is embrittled by a partial transformation of austenite. Manganese steel, obtainable in cast or wrought form, is a low-strength, high-ductility material. This material is tough and wear resistant, with the capability to work-harden from an initial hardness of 240 BHN (Brinell Hardness Number) (23 Rc = Rockwell C) to well over 500 BHN (51 Rc). Work hardening occurs naturally as this steel is subjected to impact conditions under normal work in demanding applications such as primary rock crushing. This process increases the hardness of the affected metal and its abrasion resistance. If cracking of the work hardened layer occurs, crack propagation is quickly arrested and prevented by the tougher original (not work hardened) core. As this material is selected primarily for impact and wear resistance, it is not uncommon that working surfaces of various implements wear out in time to the point where rebuilding become imperative. This is normally achieved by hard facing using arc welding to deposit new wear resistant layers. To avoid the embrittlement of the base metal, welding and hard facing require procedures that result in minimum heat buildup. Severely worn or cracked material is first removed and replaced by welding using electrodes of austenitic manganese steel. Small parallel stringer beads are usually recommended, with thorough cooling between them. When much material must be added, round or square section bars of austenitic manganese steel can be embedded within the welded build up material. Heat building should be minimized by skip welding, or moving from a weld area to another one relatively far away, before coming back to continue welding in the previous place. The same procedure is followed when applying, on the top, wear resistant alloys. A huge selection of materials is available, to be selected with the help of experts or manufacturers and according to previous experience. In all welding operations base metal temperature should not exceed 260 0C (500 0F). Limiting the temperature reduces metal shrinkage, stress buildup, distortion and surface cracking of deposits. Preferably two or more hard facing layers are applied to minimize dilution effects of base material on the working surfaces. Accurate bookkeeping of time to wear out and of costs both for the original implements and for repairs can help in improving the economic performance and in maintaining tools and assemblies in working condition. 4 - Advancements in Flux Cored Filled Metals Advancements, small or large, are constantly developed, mainly under market pressure for improving weld quality and productivity. Except that those of us following this most interesting art and science called Welding without the day to day struggle with its various problems and constraints, need always prompting from a knowledgeable source. I find such a never disappointing source in the AWS Welding Journal, the long time witness of welding progress and innovation, where I often gather interesting updated information. Presuming that not all the readers of this publication have or need ready access to the Journal, I am confident they could enjoy a quick summary of the subjects catching my attention. I would be glad to hear readers' comments on this. I would recommend to everyone interested in welding to become an AWS Member, and to get online access to the WJ virtual edition easily and economically. In the WJ March 2011 issue, at page 36 one can find the Article titled "What is new in Cored Filler Metals?" written by Keith Packard, sales and marketing manager of the Low Alloy Products Tubular Wire Division of the Hobart Brothers Co. Construction of Boiler or Pressure Vessels, offshore platforms for oil prospecting and extracting, and process piping are some of the hot areas requiring skilled manual welding labor which weighs much in the overall production costs. Any small increase of productivity in these areas can have significant impact on the economy of fabrication. Recognizing the superior productivity achievable by Flux Cored wires as opposed to shielded metal arc electrodes, special attention was devoted to improve fluxes permitting welding in all positions. For this, a delicate balance must be struck between the flux melting point and its fluidity to assure complete coverage and shielding of the weld while using additional mixed shielding gases. Welcome properties of fluxes for out of flat position welding provide fast freeze slag. The issues addressed by developers of filler metals used on chrome-molybdenum steels for the applications listed above, include meeting yield strength and corrosion resistance of base metals and also resistance to temper embrittlement, besides adequate low temperature toughness. The temper embrittlement problem is generated by slow cooling through temperatures in the range 450-600 0C (850-1100 0F). The common way to deal with it is to care to get a low value for the so called X-factor, calculated using a special formula, which is taken into account in the development work. Furthermore also diffusible Hydrogen levels are kept low to reduce crack susceptibility. In conclusion a few new flux cored filler metal wires are now available for advanced requirements, to be confirmed through qualification of suitable procedures, that permit all position welding, guarantee quality and improve productivity. Readers interested in reviewing the specific materials proposed are urged to seek the original source whose details are displayed above. 5 - Online Press: recent Welding related Articles Special High-Temp Alloys Spark Interest in EDM Enhance Weld Consistency with new Solutions from SWAGELOK IVAM Product Market "Micro, Nano and Materials" Answers to 6 FAQs about FCAW-SS Connect January/February 2011 6 - Terms and Definitions Reminder Brittle Failures are broadly classified as those that occur in a brittle manner, at load levels below the design strength, because the material toughness decreases as the rate of load increases, or the applied stress is multiaxial, or the metal temperature is low. Cross Wire Welding is a common variation of resistance projection welding where the localization of the welding current is determined by the intersection contact of wires and results in remarkable embedding of the wires in one another. Dissimilar Metal Welding presents a set of problems (difference of melting temperature, difference of expansion coefficient, intersolubility, precipitation of brittle intermetallic compounds) that must be addressed and solved if possible. If not, the dissimilar combination is considered unweldable. Face Shield is a device to be held in front of the eyes and covering all or part of the welder's face for protection from welding light radiation, sparks and spatter. Laser Beam Welding is a fusion process that produces coalescence by the heat of a laser beam impinging on the joint. Oxyfuel Gas Welding is a group of fusion welding processes that produces coalescence of the joint by the heat of an oxyfuel gas flame. Powder Feed Rate is the quantity of process powder fed to a thermal spray torch or a cutting torch in unit time. Resistance Spot Welding is a process that produces a weld at the faying surfaces of an overlapping joint by the heat from the resistance to the passage of an electric current through electrodes that provide welding current and pressure. 7 - Article - EB welding at Reduced Pressure Electron Beam Welding (EBW) is a highly successful high energy process where a beam of electrons is made to impinge at high speed upon a metal joint to generate high quality seams. The basic process is presented in our pages on High Energy Welding Processes and Electron Beam Welding Tips. The beam is generated in a high vacuum space by accelerating the electrons emitted by an incandescent cathode, through a voltage drop of tens of kV (kilo Volt), and concentrated using electromagnetic lenses. Welding by electron beam is normally performed in vacuum chambers. Electron beam welding cannot be performed usefully in air at normal pressure because air scatters the beam electrons, reducing their energy and spreading them in a much larger area. The need of vacuum in the path of the electron beam around the items to be welded severely limits the applicability of the method to the size of practical welding chambers. The pumping down time is also a factor that limits economic applicability, besides the energy requirements for operating the pumps and the floor space for accommodating the equipment needed. Different methods were tried along the years to find ways to overcome the limitation. For specific applications successful techniques were applied from time to time to solve acceptably definite configurations, generally involving mass production and relatively low quality requirements obtained with low power EB guns. One method that looked promising a few years ago, called Plasma Window, was presented in these pages in issue 19 of Practical Welding Letter for March 2005. Click on PWL#019 to see it. Unfortunately the technical difficulties proved more complex than was anticipated and probably the research funds available were limited. Therefore it seems that the original effort was abandoned although it was resumed in a different academic environment (Southern Methodist University http://www.smu.edu/), but I could not get a reliable update. The Welding Institute in the UK is always involved in research in several different welding fields. Among other projects they also addressed efforts to find a way to perform, outside of vacuum chambers, electron beam welding of thick materials. The rewards for such a system look great because the speed of welding cannot be beaten by traditional methods, and moreover there is no need for filler metal. They first developed a special electron beam gun [quote] "which allowed operation of a high-power electron gun with the work piece at a pressure in the range 0.1-10mbar or so-called 'Reduced Pressure'. In this system, the electron gun electrode geometry was carefully designed to permit a beam of 0-100kW power to be transmitted through a differentially-pumped, beam transfer column in which each pumped stage was separated by a small diameter orifice allowing passage of the beam whilst restricting the flow of gas up the column". Later they developed local seals and local vacuum pumping. The TWI system employs steel brushes as the primary seal, and with two differential pumping stages a pressure level of less than 1 mbar can be achieved reliably on plate with a typical hot rolled surface finish. Current applications being developed include Reduced Pressure Electron Beam Welding of thick tubular structures like those required for offshore wind turbine foundations, with mobile vacuum seals. Read more on these applications in:
8 - Site Updating: Vapor Degreasing, Fire Prevention The new Website Pages of the Month deal with an old and known cleaning process, Vapor Degreasing, almost ubiquitous, recently called in question because of the demonstrated destruction of the ozone layer in the stratosphere caused by the use of Chlorofluorocarbons (CFCs). The dangers were taken seriously, to the point of issuing new safety rules and of launching initiatives to develop new acceptable materials. It is the responsibility of any company using the old version of vapor degreasers to learn the new rules, and to modify their procedures in order to meet the more stringent requirements. Compliance is needed to avoid the heavy sanctions that the authorities in charge of protecting the environment are ready to inflict upon those not adapting to the new rules. See this new page by clicking on Vapor Degreasing. The other page reviews the requirements that must be followed to assure Fire Prevention wherever welding is performed. It is not only a good idea to protect people from being injured and assets from being squandered, it is the law. Apathy on this subject may exact a heavy toll in case of accidents. On the contrary a good organization, alert to the dangers, improves the safety and the satisfaction of all involved, besides providing a more relaxed work environment. For a review of the subject click on Fire Prevention. Furthermore a list of resources on this subject is now made available to all readers in our Mid April Bulletin, published further down this publication, after this regular issue of PWL. Readers are urged to see the Bulletin and possibly to bookmark it for later reference. The updates are announced in our Welding Blog also available at a service (RSS) to which
readers may subscribe to stay informed. See instructions below the Navigation Bar at the top left of each website page. Updates can also be found in our pages Site Map and Index Page built to let readers find easily what they may be looking for. You are invited to inform your friends of this website: they may benefit from the quite extensive information available to all readers and they can ask questions to obtain answers likely to help them. 9 - Short Items 9.1 - Precipitation Hardening is obtained in supersaturated solid solution metals by the precipitation of a constituent. 9.2 - Quench Hardening of ferrous alloys, by austenitizing and then cooling at a rate such that a substantial amount of austenite transforms to martensite. 9.3 - Roll Forming is a metalforming process using power-driven rolls whose contour determines the shape of the product. Used to form metal strips into tubes or structural shapes 9.4 - Sulfur Print is a macrographic method of examining for distribution of sulfide inclusions by placing a sheet of wet acidified photographic paper in contact with the polished sheet surface to be examined. [Somewhat of a lost art...] See: 9.5 - Torsion is a twisting deformation about an axis, where lines that were parallel to the axis become helices. It is also a twisting action resulting in shear stresses and strains. 9.6 - Vacuum Furnace has a chamber using low atmospheric pressure for heating materials in the rarefacted protective atmosphere. 10 - Explorations: beyond the Welder Antimatter of Fact: Collider Generates Most Massive Antinucleus Yet From One Physicist to Another: Lawrence Krauss Reflects on the Life and Work of Richard Feynman Chernobyl’s legacy Missing the Mark - Why is it so hard to find a test to predict cancer? http://www.nature.com/news/2011/110323/pdf/471428a.pdf Together forever - Chang and Eng gave the world "Siamese twins" 11 - Contributions: Welding Helmet Protection You work with tools because handling them, creating and finishing projects with them, means something to you. But a person's most essential and creatively-apt tool, the brain, is at significant risk for injury without the proper protective equipment. According to the Family Caregiver Alliance (FCA), nearly 2 million people suffer head injuries each year in the United States, and almost 100,000 result in brain injuries so traumatic that it causes long-term or permanent disability. When it comes to welding, people often handle tools and components far more dangerous than the standard nail and hammer, which means anyone who welds needs to enhance their protective gear. Even minor injuries, such as slamming your head into the underside of your car, can result in a concussion, which can take you out of commission for days. Mechanics, hobbyists, enthusiasts, and others who work with welding equipment on the regular are substantially increasing their risk of a serious head injury, and as the FCA points out, over a third of injury-related deaths each year are those related to the head or brain. Welding helmets have come a long way since the old days, meaning that they're not only safer, but can be more stylish and sleek than before. There's no reason to be embarrassed wearing one, as what's less manly: wearing a welding helmet or being a brain-dead potato in a hospital bed? I think we all know the answer to that. Welding helmets double as protection for your eyes, as most helmet selection provide clear, durable coverage over the part of your head where your eyes rest. Nearly as vital as protecting your brain, shielding your eyes from serious damage can prevent loss of sight, blindness, or other side effects resulting from exposure to intense heat impact or other injury. Without working eyes, it would be much harder (and far more dangerous) to weld, so keeping that in mind is a fantastic way to motivate you to put your helmet on every time. A task as fast and easy as putting your welding helmet on should also make it a fast and easy choice when deciding to wear it or not.
Brett Scuiletti Note: - I am grateful to Mr. Brett Scuiletti who kindly contributed this article. E.L. 12 - Testimonials On Sun Mar 13 07:39:51 2011, the following results were submitted from the "Form 5" on welding-advisers.com: Name: Bindeshwari Pal
On Wed Mar 16 05:01:10 2011, the following results were submitted from the "Form 5" on welding-advisers.com: Name: Wim Hart 13 - Correspondence: a few Comments 13.1 - Although this is a common occurrence, I am always taken back anew. The following question is typical. "We are seeking a machine to weld thin aluminum sheets at an industrial scale. The material is 0.5mm thick (about 0.02 in.). The sheet is rolled into the form of a cone [Dimensions are given]. The weld must be very clean. Can you recommend suitable TIG equipment for this application?" I can only regret the missing details standing between the exposition of the problem and the search for the most suitable solution. I must also try to explain that the question is ill formulated. 13.2 - In my Contact Us page, I suggest to my readers that, before sending me a query, they search in my website. Along the years quite a sizeable amount of knowledge has accumulated. Even if you don't find the answer you seek, the mere search will clarify to yourself your request, and possibly show you the details you need to supply in order to get a meaningful answer. With reference to the above query, why should the inquirer assume that TIG is the recommended process? 13.3 - A new contributor sent photos of his artistic welded works, which already got favorable comments. Find them under My Works in https://www.welding-advisers.com/Welding-Art.html 13.4 - Readers interested in used friction welding machines can write to get details and contact of someone who has surplus to dispose of. 14 - Bulletin Board 14.1 - Conference on Welding in
Shipbuilding 14.2 - AWS National Robotic Arc Welding Conference and Exhibition 14.3 - AeroMat 2011 14.4 - Conference on Preventing Weld Failures 14.5 - Follow SiteSell to discover new avenues. SiteSell Facebook SiteSell Twitter On SiteSell Twitter, visitors will learn who SiteSell is, through each person delivering personal insights into SiteSell... his news, his interests and perspectives. They can interact with each "SiteSeller" too, asking questions of programmers, coaches or anyone else. SiteSell YouTube SiteSell Blog Case Studies Retirees Jump Start Your New Initiative: Removing the last Barrier to Indecision: The 90 Day Guarantee: See: Order NOW!
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Bulletin 60 - PWL#092 keywords: Fire Precautions, Welding Fire Prevention, Fire Safety, Permit Requirements, Chapter 26 PWL#092B - Resources on Fire Precautions for Welding, Welding Fire Prevention and Suppression Procedures, Fire Safety, Fire Marshal Permit Requirements, Virginia Statewide Fire Prevention Code - Chapter 26, Sample Written Plan, Fire Prevention Field Guide, Articles and much more...
Important AnnouncementFor assembling at no cost your own Encyclopedia Online,
Introduction This Mid April Bulletin #60 is now integral with and appended to the regular PWL#092 publication. The subject of this Bulletin is a collection of Online Resources on Fire Prevention in addition to the new website page with the same Title announced in Section 8 above. A previous Mid Month Bulletin already provided some interesting information presented by different sources on Welding Safety in general. Click on PWL#050B to see the Bulletin 18 issued on October 2007. 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) 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 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. Resources Fire Precautions for Welding (5 pages) Fire Prevention Program (8 pages) Fire Prevention Update of Welding Fire Prevention and Suppression Procedures Welding 1910 Subpart Q (Presentation 66 Frames) Welding and Cutting Part 1926 Subpart J (presentation 73 Frames) Welding, Cutting and Brazing (Presentation 66 Frames) Welding, Cutting, and Brazing Welding & Cutting Safety - Hot Work (Draft) Fire Prevention Plan Sample Written Program - Fire Prevention Plan Fire Marshal Permit Requirements Welding and Other Hot Work (4 pages) Welding, Burning, and Cutting Program Fire Prevention Arc Welding Safety Fire Prevention Program Welding, Cutting, and Brazing For General Industry and Construction Industrial Operations Fire Prevention Field Guide Guidance Document for Fire Prevention During Cutting and "Hot Works" Operations Safety Bulletin Index - Welding, Cutting, Brazing & Heating Welding, Cutting, and Brazing Safety Program (8 pages) Fire Prevention Measures What special fire prevention precautions must be taken? A Guide to Safety while Arc Welding (Presentation 16 Frames) Fire Prevention Plan - Fire Safety Training Welding and Cutting Safety Program Boston Fire Prevention Code (127 pages) Fire Prevention Guidelines and Practices (42 pages) Hot Work Fire Prevention Welding Data General Safety Precautions Preventing torch fires in welding and cutting
operations Preventing welding-related fires
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