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PWL#098 & 098B - LENS®, Wailing Structures, Pyromet®, Managing Welding Costs, Leak Testing October 03, 2011 |
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We hope you will find this Letter interesting and useful. Let us know what you think of it. Laser Engineered Net Shaping (LENS®), Wailing Structures, Pyromet® X-23, Managing Welding Costs, Leak Testing, Jewelry Artwork, Weldability of Cast Nickel Superalloys, Kroll Process, Liquid Nitriding, Magnetostriction and much more...
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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.
1 - Introduction 2 - Article - Laser Engineered Net Shaping® 3 - How to do it well: Wailing Structures 4 - Filler Metal Pyromet® X-23 5 - Online Press: recent Welding related Articles
6 - Terms and Definitions Reminder 7 - Article - Managing Welding Costs 8 - Site Updating: Leak Testing, Jewelry Artwork 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contributions: Weldability of Cast Nickel Superalloys 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board
1 - Introduction Hello everyone! This 98th issue of Practical Welding Letter opens with a review of point to point fusion technologies employed for creating automatically from a drawing any three dimensional body. It is quite amazing that what started as a repair procedure for damaged and useless expensive parts ready to be scrapped, evolved in time to a mature technology used to add elements or features to semifinished parts, or to build parts from scratch. Then I answer to an interesting question of someone who does not know how to get rid of disturbing sounds he gets from his construction. He is not aware that those sounds are part of the solution of his problem! Follows an introduction to a specially developed stainless steel of exceptional properties, and by the way also on its weldability and filler metals that can be used to join it.
Next comes a reminder of ways to manage welding costs in a shop or welding department by paying attention to important factors whose influence risks of being undetected in the day to day operations. And yet they may have far reaching effects which should be acted upon. The pages of this Month are briefly introduced, one on Leak Testing, a necessary quality check for new production and for maintenance, the other on Jewelry Artwork, that can become a rewarding hobby for talented people. Some considerations are outlined on the limited weldability of cast nickel base superalloys, essentially for alerting hopeful tinkers that it is no job for them. All other departments can be found where they should be. Let us have your comment and feedback. Don't use Reply. Use the Contact Us form to reach us.
Readers are again reminded that we are soon to reach our 100th Issue, and that I would be delighted to publish in that occasion reports on practical lessons learned by anyone who found solution he would be proud to share with this audience. 2 - Article - Laser Engineered Net Shaping® A promising technology described in the open literature uses laser assisted local fusion of metallic powders for building solid engineering bodies or for repair. It was first introduced in this publication (Practical Welding Letter) in Issue 37B of Mid September 2006, where an article from The Welding Journal was referred to.
The title of the article is In that article a team of research and industry specially formed for this purpose is introduced, which was responsible for the process development and its remarkable achievements. The basic technology is described and typical results are presented showing how freeforms were generated without any tooling, and how expensive parts were repaired at a fraction of the new part cost. In the Conclusions the important factors and the economic advantages are stressed, with the observation that new creative drive is needed to try new applications and to test their limitations, using thorough qualification programs to achieve industrial acceptance. Then in Issue 43 of our Practical Welding Letter the case of expensive items salvaged by this technique was stressed again as one of the most useful processes capable to give new lease of life to damaged parts.
In the September 2011 Issue of the Welding Journal, Welding Research Supplement, a new article is published at page 172-s with the title Laser Engineered Net Shaping® for Repair and Hydrogen Compatibility. The equipment used in the specific experimental work is described in its main components. Then a set of trials are described, to repair overbored reclamation weld bases and sample bottle surface flaws. A set of Hydrogen Compatibility tests were performed to assess the effect of hydrogen on LENS repaired components of austenitic stainless steel, type 304L. The results are exposed in detail and discussed. After declaring that the results reported demonstrate the successful repair of the test items, the article concludes that the LENS repair is highly suited for the repair of overbored reclamation type materials. However, for the weld repair of notched gas sample vessels, the article invokes additional development work that should include joint preparation in addition to thermal inputs and translation rates. Before scrapping expensive items requiring reconditioning, interested readers should consider LENS® repair and salvaging procedures. The above article is available at: http://www.aws.org/wj/supplement/wj201109_s171.pdf Quite coincidentally an article titled Mechanical Properties of Parts Formed by Laser Additive Manufacturing was published at page 26 of the September 2011 issue of Advanced Materials and Processes, a publication by ASM International. The article introduces research to be presented at MS&T2011, October 17 through 20 (see details at 14.2 further down this page) in two separate symposia. The "Mechanical Properties of Additive Manufactured Materials and Components" and the "Laser Applications in Materials Technology (II)" comprising six sessions. Readers interested in achievements and limitations of this advanced technology are urged to become informed because it will "provide an immediate impact on the suitability, affordability, and availability of critical components throughout industry, as well as enabling the exploitation of innovative designs and materials not possible using traditional manufacturing methods".
3 - How to do it well: Wailing Structures. Q - We manufacture hydraulic press machines. We fabricate a top and bottom block which we hold together with two pillars of about 9.5" (240 mm) diameter. The top and bottom blocks are hollow box girders. The vertical section is 70mm and the horizontal section is 50mm. These structures are stress relieved and then machined. My problem is that when we assemble the machine and we put pressure on the structures, a crackling sound comes. We thought this sound should not be there because we have stress relieved it after welding, but it is still there. How can I get rid of the sound? A - Thank you for your question. On the contrary, you should listen carefully to the crackling sound. The structure is wailing, signaling to you that it is in distress. In fact a crack is propagating and the elastic energy liberated by the crack progress is heard as sound. If at any time the sound seems to stop it can be due to loading to a lower stress level. To get sounds you need to exceed the last maximum load.
You should search Universities or Metallurgical Laboratories to find a provider of Acoustic Emission Analysis services. They will come with their instruments and place a few sensors (microphones) in strategic locations on the structure to test. When the sensors are in place you should load sufficiently the structure again so as to repeat the sounds. Then the emission point will be found by triangulation. Acoustic Emission Analysis may point you in the right direction as to the reason of failure and let you avoid defective materials or marginal welding practice. A thorough and correct metallurgical investigation, will solve the problem for all your future production. An introduction to Acoustic Emission was published (2) in Issue 62 of Practical Welding Letter for October 2008. Several links to additional information are offered there.
Assuming this is standard production I would think it advisable to find the reason and to avoid liabilities for the future even if the test costs money. Most probably, using Magnetic Particles Inspection, you will find at that place a small crack. Then you will have to develop a repair procedure. You will get rid of the sound after the repair is done. You should then inquire why the crack appeared in the first place. Is that the material at fault? Is it an inadequate procedure? Was the preheat correct? Were the electrodes dry and moisture free? Assuming the plates are of mild steel, it is not the composition that matters most as the absence of internal defects like laminations, that cannot be found except by ultrasonic testing. If defective areas are detected on heavy plates by a knowledgeable inspector with suitable equipment and experience in Ultrasonic Inspection, they can be scrapped, before welding them in stressed structures.
The quality improvement will be remarkable and valuable, and the Crackling Sounds will be eliminated. A list of useful Links on the subject of Acoustic Emission, as an extension of the content of this Article, is provided further down in the Resources, presented in our Mid October Bulletin #066, published as PWL#098B and attached at the end of this regular publication. Please scroll down! Don't miss it!
4 - Filler Metal Pyromet® X-23 A relatively new precipitation hardenable stainless steel whose commercial designation is Custom 465®, from Carpenter Technology Corporation is being described in their publication titled Advanced Stainless Offers High Strength, Toughness and Corrosion Resistance Wherever Needed, found at
Is is also presented in a different publication with more technical data at The highest properties, like excellent notch tensile strength and fracture toughness in any of the suggested conditions, are developed through precise heat treatment to form defined microstructures. As such the material is not primarily intended for welding, except that the properties can be restored after welding by full solution annealing with cold treatment and aging. The data relative to the Weldability of this alloy can be found in another publication, Technical Datasheet,
GTA and GMA welding are recommended, using suggested indicated matching commercial filler metals. Oxyacetylene welding is not recommended and preheating is not required. Interested readers are urged to seek the quoted publications for additional informations. 5 - Online Press: recent Welding related Articles Strategies for Improving Automotive Welding Operations Handling, installing, and maintaining GMAW consumables Application of underwater welding processes for subsea pipelines
Arc Welding the Un-Weldable Welding of cast iron
6 - Terms and
Definitions Reminder Double-Flare-Bevel-Groove Weld is the one in grooves formed by a member with a curved surface in contact with a planar member Fillet Weld Break Test is the test where a fillet test specimen is loaded so that the weld root is in tension, meaning that the two elements are bent one toward the other Groove Radius is that used to form the shape of a J- or U-groove weld
Horizontal Rolled Position is used to describe the position of a pipe joint where the axis of the pipe is approximately horizontal, and welding is performed in the flat position by rotating the pipe Infrared Soldering is a process where the heat for soldering is provided by infrared radiation J-Groove Weld is a type of joint where one or both faces are machined to a shape reminiscing of the letter J, from the top side or from top and bottom sides Oxygen Cutting is a group of cutting processes for severing or removing metal by means of the chemical reaction between oxygen and the base metal at elevated temperatures Pulse Time in resistance welding indicates the duration of time during which electric current is applied through the welding circuit 7 - Article - Managing Welding Costs All weld shop owners and foremen should be eagerly interested in tips intended to show them where it is possible to save on wastes and how could they improve their bottom line with some attention to important details. One such timely reminder was published in the August 2011 issue of the Welding Journal at page 42. It is an excerpt from the Welding Handbook Ninth Edition, Volume 1, that should be present on the shelf of all persons having an interest in welding. See our page on Welding Books. The article concentrates on Manageable Costs which include factors such as joint design, weldment design, mistake proofing layouts and fitups, process selection, eliminating operations, production planning, welding procedures, supporting activities and field welding. Even those without effective responsibility on the financial soundness of the welding operation they are connected to, but who take at heart the prosperity of their work place, could contribute to financial improvements in their surroundings just by paying attention to important details and by calling the attention of management to ways to implement the suggestions.
Changing the joint design is probably beyond the faculty of welders, but they could call the attention of whoever is responsible, if a simple change can decrease excess weld material by reducing the joint cross sectional area. The introduction of computer controlled cutting centers that produce complex geometries inexpensively should be made by redesigning the older manual layout, to take advantage of increased quality that permits increased weld speed. One way to control consistent root opening is to design standoffs in the workpieces to reduce setup time. Weld locating features reduce the cost of layout, inspection and overwelding. The same is achieved by incorporating mistake proof features, to reduce scrap. An article on Design for Error Proof Assembly was published (2) in PWL#040. See also Where is the Welding Management? Process selections should be investigated. The problem is that to compare different processes one should be able to know the real costs incurred per unit length of weld or deposited weight for any given welding procedure. This entails some accounting work that most shops prefer to avoid. The article lists and explains the influence of factors like welding procedures, supporting activities, field welding, unforeseen costs and quality. Constant attention to the daily practice will reduce waste and improve the financial performance of any welding operation. It pays to make the effort. Interested readers feeling that their costs are not under control, should explore and take seriously into account the important details listed and discussed in the quoted article.
8 - Site Updating: Leak Testing, Jewelry Artwork The Pages of this Month cover some new items that were not yet addressed satisfactorily up to now. The first page deals with Leak Testing, a universally necessary proof of the quality of whatever fluid container is manufactured or repaired. Specialized techniques for detecting minor leaks with high sensitivity are not covered though, but the page hereafter can give a general orientation for the subject. See
Leak Testing The other page deals with Jewelry Artwork, a subject likely to interest readers with creative minds and good hands, thinking of trying and improving their talents with specific activities
Jewelry Artwork The updates are regularly announced in our Welding Blog, that can be searched at any time by clicking on this link. It can be seen also by subscribing to the RSS service, as explained under the NavBar in every page. New pages are also included in the Site Map and in the Index Page
You may suggest subjects for new pages and let us have your feedback or comments by using the form in the Contact Us page. 9 - Short Items 9.1 - Alpha Case in Titanium is the oxygen-enriched phase that occurs when the metal is exposed to heated air or oxygen. Alpha case is hard and brittle, and tends to create a series of microcracks which will reduce the metal's performance and its fatigue properties. Its fragility makes it undesirable for aerospace applications. 9.2 - Kroll Process is a pyrometallurgical industrial process used to produce metallic titanium by the reduction of titanium tetrachloride with a more active metal, such as magnesium or sodium. The sponge is further processed to granules or powder. 9.3 - Liquid Nitriding (nitriding in a molten salt bath) employs the same temperature range as gas nitriding, that is, 510 to 580 °C (950 to 1075 °F). The case-hardening medium is a molten, nitrogen-bearing, fused-salt bath containing either cyanides or cyanates (WARNING: These are Poisonous salts!). Unlike liquid carburizing and cyaniding, which employ baths of similar compositions, liquid nitriding is a subcritical (that is, below the critical transformation temperature) case-hardening process; thus, processing of finished parts is possible because dimensional stability can be maintained.
9.4 - Magnetostriction is a property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of material's magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value. 9.5 - Oxygen Lance is a length of pipe used to distribute oxygen either beneath or on top of the melt in a steelmaking furnace through molten pig iron to lower the carbon content of the alloy and change it into low-carbon steel, or to the point of cutting in oxygen lance cutting. 9.6 - X-Ray Maps usually corresponding to an image, are collected using raw counts from the elemental peaks of interest, and the intensity of the reproduced color in any area is proportional to the concentration of a specific element in that area. 10 - Explorations: beyond the Welder Particles Found to Travel Faster than Speed of
Light Witness Unreliability Casts Doubt on Death Penalty Rulings Financial Speculation on Commodities Fuels Global Insecurity Infections You Can Get From Drinking Unclean Water Do You Turn Your Head When You Hear A Loud Noise?
11 - Contributions: Weldability of Cast Nickel Superalloys. Heat Resistant Nickel-base Superalloys include quite a number of different materials used in most demanding aerospace applications. These materials can be grouped in categories by the base material and by the type of technology used to provide strength and heat resistance. The class considered here includes the nickel base alloys that harden by a complex thermal treatment including a solution treatment and then reheating at controlled temperatures for definite periods of time for obtaining precipitation of the hardening phases of the required size and distribution. The common problems encountered in the fusion welding of superalloys are hot cracking and post-weld heat treatment (PWHT) cracking, which is also called strain age cracking or delayed cracking. Postweld strain age cracking occurs in precipitation hardenable alloys when weld induced residual stresses, and the stress imparted by aging, exceed the yield strength and available ductility of the material. The result is instantaneous catastrophic failure by cracking. In addition the degradation of mechanical properties of welds is another issue, even if by using special precautions, cracking is avoided. Superalloy welds are sometimes designed with the joints region thicker to reduce the stresses at the weld, to achieve a practical, usable welded structure. Therefore for practical purposes these superalloys must be considered unweldable. Complex welding processes of superalloys can be afforded, when needed, only by large organizations who dedicate to the task Research and Development facilities, if the purpose is worthy the investment. In that case the use of very low heat input is imperative, and buttering or overlaying the surfaces with ductile alloys may be helpful. Local repair of damaged cast blade tips or edges is performed satisfactorily, notwithstanding the difficulties, with the laser techniques described above in section 2, or with the analogue version that makes use of electron beam equipment and local material supply. 12 - Testimonials To: welding-advisers
From: Richard Chwa Hello, I really enjoy and learn
a lot from Practical Welding Letter and I appreciate you educate the people by online email. Thanks, 13 - Correspondence: a few Comments 13.1 - Q - Is it possible to receive your news letter mailed to my work? 13.2 - Q - Undefined repair question 13.3 - Invitation - This monthly publication, which will soon reach its 100th issue, strives to provide correct and useful information on metallurgy and welding. As mentioned above, Readers may occasionally have been helped if they decided to follow the suggestions and if their problem was solved. If this was indeed the case, I would appreciate being informed. Learning of positive outcomes is highly rewarding, demonstrating that there is a need for this kind of contribution and that the results are worth the efforts invested in publishing. I would love to be able to publish in the 100th issue, due out in two months, short reports written by readers who feel they enjoyed some benefit by being exposed to the information presented here. 14 - Bulletin Board 14.1 - Canadian Manufacturing Technology Show 14.2 - MS&T 2011 - Materials Science & Technology 2011 Conference & Exhibition 14.3 - International Congress on Advances in Welding Science and Technology 14.4 - The International Congress on Applications of Lasers & Electro-Optics (ICALEO) 14.5 - FABTECH 2011 14.6 - Download the latest AWS catalog at 14.7 - How could SBI! help you? Watch the following video and you wil know...
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Please continue to browse down hereafter for the Mid October Bulletin. Copyright (©) 2011, by Elia E. Levi and
Mid Month Bulletin 66 - PWL#098B October 2011 PWL#098B - Resources on Acoustic Emission Benefits, Inspection, Testing, Monitoring, Introduction, Publications, Standards, Procedures, Basics, Terminology, Fatigue and Fracture Materials Research,Warning Sounds from Materials, Fundamentals, Equipment, Data Analysis, Technology and much more...
Mid October BulletinOctober 2011 - Resources on Acoustic Emission - Bulletin #66
However well informed and
expert you may be, you could certainly benefit from a vast repository of online authoritative welding information. The following may be just what you need... Important AnnouncementFor assembling at no cost your own Encyclopedia Online, Order now! at Metals Knowledge. Introduction This Mid October Bulletin #066 is now integral with and appended to the regular PWL#098 publication. The subject of this Bulletin is a collection of Online Resources on Acoustic Emission as an extension to our Article on Wailing Structures, published above in Section 3.
We dealt briefly before with the said subject: 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). If you prefer not to subscribe, you may also click periodically on the Welding Blog button in the NavBar to see Updates.
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.
Resources Acoustic Emission McGraw-Hill Science & Technology Encyclopedia: Acoustic Emission TWI Knowledge Summary: Acoustic Emission Cardiff University - Acoustic Emission Introduction (Links) Cardiff University - Acoustic Emission Publications (List) Introduction to Acoustic Emission Testing (Links) Using Acoustic Emission in Fatigue and Fracture Materials Research Acoustic Emission: Heeding the Warning Sounds from Materials Acoustic Emission Standards Acoustic Emission Standards and Procedures Acoustic Emission Standard Terminology ASTM E1316-05 Acoustic Emission Basics by Boris Muravin Acoustic Emission Testing Benefits Journal of Acoustic Emission (JAE) Acoustic Emission (AE) - NACE Resource Center NASA Acoustic Emission Search (Links)
Advanced Acoustic Emission for On-stream Inspection of Petrochemical Vessels (12 pages) Quantitative Acoustic
Emission Non Destructive Inspection Inspection of Power Plant Headers Utilizing Acoustic Emission Monitoring (8 pages) Acoustic Emission Inspection of Spherical Metallic Pressure Vessels (10 pages) Acoustic Emission Inspection of Buried Pipelines (Abstract) Evaluating the Structural and Mechanical Integrity of Pressure Vessels and Components by AET (10 Pages) Acoustic Emission Testing (Presentation - 24 slides) Acoustic Emission for Non-Destructive Testing of Bridges (14 pages) Acoustic Emission Technique Application to Pressure Vessel Testing (8 pages) Combined Application of Ultrasonic Inspection and Acoustic Emission Monitoring
for evaluation of fracture critical members in railway bridges (16 pages) Damage Assessment and Improved Inspection Systems Probabilistic Structural Health Monitoring Using Acoustic Emission Composite materials characterization by acoustic emission technique (Abstract - 2 pages) Early Detection of Steel Rebar Corrosion by Acoustic Emission Monitoring (9 pages) Non-intrusive Inspection of above ground Storage Tanks (presentation - 39 slides) Note: The following commercial links are proposed to the Readers for the information value they may have. No endorsement or recommendation is intended. Physical Acoustics - Structural Integrity and Acoustic Emission Monitoring Solutions (Commercial) AE Testing - Fundamentals, Equipment, Data Analysis (Commercial) (7 pages) Testing Coatings using Acoustic Emission Technology (Commercial) Real-Time Acoustic Emission Monitoring (Commercial) If you think that this page might be useful, you are invited to forward it to a Friend.
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