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PWL#049 - Friction Stir Surfacing, Joining Copper to Steel, Nonstandard Fillers,High Energy Drilling September 03, 2007 |
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| We hope you will find this Letter interesting and useful. Let us know what you think of it. PWL#049 - Friction Stir Surfacing, Joining Copper to Steel, Non Standard Welding Filler Metal, High Energy Drilling, Vertical Welding Tips, Applications of Electroslag 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. If you received this from a friend and if you like what you read, please subscribe free of charge and you will also receive a bonus book on Practical HARDNESS TESTING Made Simple.
1 - Introduction 2 - Article: Friction Stir Surfacing 3 - How to do it well: Joining Copper to Steel 4 - Non Standard Welding Filler Metal 5 - Online Press: recent Welding related Articles 6 - Terms and Definitions Reminder 7 - Article - High Energy Drilling 8 - Site Updating: Vertical Welding Tips 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contribution: Applications of ESW 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board
1 - Introduction After this summer vacation, that we hope you all enjoyed having a good time, we come back to work with the present 49th issue of Practical Welding Letter. We start the present publication with a short review of Friction Stir Surfacing, a novel technique still in development that may be useful for certain material combinations not readily amenable to processes involving melting. We then go on answering a real question asked by a reader with a problem. We hope we were of help, but actually we got no reaction. We would like to involve our readers in a more active role. We will present an Invitation further down the page, in section 14.3. Then we deal with non standard consumables. While it is generally good practice to use filler metals defined by current specifications, it is by no means the only way and actually remarkable benefits may be enjoyed sometimes by using non standard, although controlled, consumables. High Energy Drilling is the title of an article describing the main features of two competing technologies, the supremacy of which one of the two remaining at present undecided. Advanced manufactured items depend on this kind of drilling for their economic manufacture. The Page of this Month newly added to our Website deals with Vertical Welding. Although there is no substitute for actual supervised training, the next best thing that can be done is providing some tips and references: this much is what we have tried to do, while encouraging new welders to try to master welding in this difficult position. The last featured article provides some insight into recent developments and applications on Electroslag Welding, one of the most successful processes used on heavy sections that are to be joined together. Other sections will be found at their usual place. We hope that the subjects presented have some general interest for our readers. We would gratefully acknowledge specific comments of our readers concerning the themes discussed and the depth of treatment. Please accept our Invitation, in the Bulletin Board, section 14.3, down this page.
2 - Article: Friction Stir Surfacing Surfacing by means of Friction Stir technology is actually a spin-off (literally!) of Friction Stir Welding. This quite new technology is one of the most significant welding innovations introduced in the last three decades. A page with general information can be found in our Website by a click on We dealt with FSW in one of our last issues of Practical Welding Letter. Click on PWL#047 to read the article (2). The application of a surfacing material to a substrate is performed, in one of the available variants to the process, by rotating and pressing a suitable shape of the surfacing material upon the material to be covered. The friction heat that develops at the point of contact permits the formation of a local layer of forged material that is deposited and intimately mixed with the substrate while involving only a minimum amount of dilution. The point is that the process does not entail fusion, although calling it a cold technique is probably misleading. Therefore it is suitable for all kinds of sensitive materials that lose their properties when undergoing melting. One of the most interesting applications, possibly still in the development stage, seems to be the application of Metal Matrix Composites (MMC) as surfacing materials applied on top of a vast range of substrates. Find additional information in the following pages: Friction Surfacing What is Friction Surfacing On Friction Stir and on Additional Surfacing Processes
3 - How to do it well: Joining Copper to Steel [This is a real question we got from one of our Correspondents.] Q: - We need to TIG weld 3/8" ODx.035" wall copper (SB-75) tubes to a carbon steel tube sheet. We will use Argon gas for shielding, 2% Thoriated Tungsten, would you recommend a low silver (5%) or a high silver (15%) filler metal or something altogether different. Would this be a Brazing (SB) or would this be a Tig (GTAW) process. A: - Joints designed for welding have a shape different from those suitable for brazing. The selection is based upon the function of the assembly in service and on the ease of joining, strongly dependent upon the facilities available and on production quantities, which influence production costs. Please note that ASME SB-75 includes the following materials:
If the joint design specifies butt welding of tube ends, one can Tig weld the tubes with Filler Metal: If the tubes enter into the tube sheet for a suitable overlapping length, depending on service requirements, with clearance on the diameter of about 0.05-0.13 mm (0.002-005") at brazing temperature, one can select a silver based filler metal and a corresponding flux from quite a large list of available materials. For low production quantities an oxyacetylene flame would be adequate. For mass production furnace brazing in a controlled atmosphere would be probably more economic. Cleanliness is of the utmost importance.
4 - Non Standard Welding Filler Metal It is common practice to specify welding consumables according to current AWS, European or other Specifications. These documents establish a minimum of requirements that manufacturers are bound to meet in all their production, by taking responsibility for the quality of what they sell. There are however situations where different products from various sources, nominally meeting the same Specification, behave in the field in peculiar ways. The user may find significant variation, to the point that one specific product gives practical advantages like ease of manipulation and increased deposition rate, while the nominally identical (per Specification) alternative may leave the welder not satisfied with the performance. Supervision should encourage the unbiased expression of provable preference and encourage selections assuring increased productivity. The perceivable differences stems from the general character of specification requirements and from the different ways used by manufacturers to assure compliance. The reasons for paying attention to the product brand are stresses in a recent article on How to Purchase Consumables by Lincoln Electric, which makes reference to FEMA 353 Guidelines for Steel Moment-Frame Construction Seismic Applications. See: In the official document the recommendation is brought forward to indicate the selected consumable by brand name, and to perform all the required tests with reference to the specific brand selected. Please note the following sentence from the above mentioned article: In a more general context, when developing the requirements for an important project, one should possibly research the consumables to be selected by requiring the cooperation of the development laboratories of reputable manufacturers. In this way also non standard consumables may be proposed for actual welding trials and testing which may offer practical benefits beyond those of the products already standardized. One should not mix up the requirement that a certain filler metal meet a given specification, which means that the composition and properties are well defined, with the request that the product be certified to have been manufactured according to specific quality standards, with full traceability to raw materials used and processes employed. In particular a certain filler metal, designated by its trade name, may be non standard, that is there is no accepted general specification describing its composition and properties other than an internal document of the manufacturer, and still it may be certified by the same manufacturer who testifies that it meets quality requirements relative to traceability, uniformity, consistency etc. On Certifications for Welding Consumables see an article at page 42 in the July 2007 issue of The Welding Journal. 5 - Online Press: recent Welding related Articles From TWI: From The Fabricator: From Miller Electric Mfg. Co.: From ESAB: Frow AWS Inspection Trends: 6 - Terms and Definitions Reminder Back Weld is a weld made on the back side of a single groove joint. Brazing Filler Metal is the joining metal intended to fill the capillary space between the elements. Its melting range is above 450 0C (840 0F) and below the melting point of the base metal. Electroslag Welding (ESW) is a welding process suitable for thick material. It is performed in the vertical position. The one pass molten metal weld bead is contained between the abutting surfaces to join and water cooled shoes that are moved along the joint as welding progresses. Melting of filler metal occurs in a bath of molten flux floating upon the molten metal. Resistive Heat is provided by the passage of an electrical current through the flux which is constantly added to make up for losses. Friction Welding (FRW) is a solid state process obtained when the heat, produced by rubbing under pressure two elements (generally one rotating against one stationary), plastically displaces the materials at the faying surfaces while the pressure welds them together. This process is suitable for dissimilar material welding without fusion. Narrow Gap is a loose term for limited distance between abutting surfaces, indicating a significant progress developed in ESW (see above) in the search for ways to improve weld metal properties. Polarity indicates the mode of connection of a direct current power source to electrode and work. Straight polarity is direct current electrode negative. Reverse polarity is direct current electrode positive. Root Face is the straight portion of the groove face near the root. T-joint indicates two elements, one of which is about perpendicular to the other in the form of the T letter. 7 - Article - High Energy Drilling Drilling of many precise small holes on sheet metal but also on different kinds of nonmetallic materials can be done successfully, if applicable, by one of the technologies based on fully controllable powerful beams. High energy beams employed for practical drilling purposes are usually either electron beams or laser beams. The energy is high because it can be concentrated on a tiny spot in such a way that the material is instantly vaporized where the beam hits. There is no general rule suggesting which beam is better. Both technologies are capable of performing similar feats so that, if the results are acceptable, the only other criterion of selection is economic. The pieces of equipment needed are quite expensive in both cases. Laser beam is transmitted in air. The pointing system which used to be made of mirrors moving along perpendicular lines to cover all the working space are recently being supplanted by optical fibers with considerable simplification and economy of the mechanical equipment. Electron beam is transmitted only in vacuum, so that the working space, enclosed in a sizeable box, must be evacuated by powerful pumps for every charge of parts. The pointing system is much simpler, consisting in magnetic lenses that deflect the beam exactly as needed under computer control. Operators of laser beam must be aware of the dangers to their eyes and skin if hit by the powerful beam. Electron beam operators must be protected by x-rays generated in the machine. Both drilling methods leave a thin layer of recast metal on the internal surface of the holes. For certain applications this layer may be objectionable, and may need to be limited in depth or eliminated by additional operations. An article on laser welding explains basic facts on laser beam formation and characteristics: See hereafter how studies are programmed to research the feasibility of
Laser Drilling of Oil and Gas Wells: The following commercial enterprises offer equipment and services for laser drilling and show examples of actual work performed: http://www.ipgphotonics.com/apps_mat_lab_drilling.htm Examples of laser drilling and micromachining http://www.public.iastate.edu/~weichiat/Lambda%20Psysik%20Gator%20Series.pdf Laser Drilling from commercial sources http://www.gsilumonics.com/laser-drilling-a.htm http://www.laserage.com/drilling.html http://www.cmslaser.com/cdw/ http://www.laserusa.com/services_laser_drilling.asp?section=services&page=laser_drilling http://www.prima-na.com/pages/44_laser_drilling.cfm See the following article on On Electron Beam Drilling see advertised capabilities of commercial sources: http://www.ebdrilling.com/capabilities.htm http://www.pro-beam.de/tic2/Precise-drilling-with-electron-beams_117_1.html
8 - Site Updating: Vertical Welding Tips The Page of this Month deals with Vertical Welding. Like other out-of-position welding, performing successful arc welds in vertical position requires additional knowledge and skills to be acquired by painstaking training, possibly supervised. Our page presents hints and tips to be followed by actual exercise. To see the new page click on Vertical Welding Tips. Look for new Website pages by reviewing periodically the Welding Blog or the Site Map. Let us have your comments and feedback. Click on Contact Us. Or, even better, accept our Invitation down this page, in section 14.3.
9 - Short Items Alkali Metal is a metal (in group IA of the periodic system) namely, lithium, sodium, potassium, rubidium, cesium, and francium. They form strongly alkaline hydroxides, explaining the origin of the name. Bend Test is used for determining relative ductility of metal that is to be formed (usually sheet, strip, plate, or wire) and for determining soundness and toughness of metal (after welding, for example). The specimen is usually bent over a specified diameter through a specified angle for a specified number of cycles depending on the governing requirements. Boss is a relatively short addition protruding from the surface of a forging or casting, often cylindrical in shape. Usually intended for drilling and tapping for holding or for attaching parts. Crimping is the forming of relatively small corrugations in order to lock a fastener in place, to set down and lock a seam, to create an arc in a strip of metal, or to reduce an existing arc or diameter. Matrix is the continuous or principal phase in which another constituent is dispersed Metal-Matrix Composite is a composite material that consists of a nonmetallic reinforcement, such as ceramic fibers or filaments, incorporated into a metallic matrix, to provide selected improved properties.
10 - Explorations: beyond the Welder The Researcher (8 pages) Neon Saturn South Florida: People and Environments (Click on Next in every page) How Hi-Tech Nuclear Science is feeding the Poor Real-World Stories told by a flesh-and-blood Human
11 - Contribution: Applications of ESW A short article introducing the Electro Slag Welding (ESW) was published (2) in Issue 7 of Practical Welding Letter for March 2004. Click on PWL#007 for reading the article. In the United Stated, the application of ESW for bridge tension members was subjected to a temporary prohibition by the Federal Highway Administration (FHWA) following the finding of a crack during a repair procedure. This prohibition spurred intense and active research that brought to the development of a new and improved process, now called Narrow Gap Improved Electroslag Welding (NGI-ESW). The new Specification ANSI/AASHTO/AWS D1.5M/D1.5, Bridge Building Code was written to cover the new requirements also for high performance ESW joints, where specific impact strength requirements are spelled out for different environmental situations. On recent developments and applications of ESW you may wish to review the following information available online: Recent Advances in Field Electro Slag Rail Welding (32 pages) A New Approach to Electroslag Welding Narrow Gap Improved Electroslag Welding for Bridges (11 pages) Narrow Gap Improved Electroslag Welding (NGI-ESW) Procedure (8 pages) State of Art in Transportation Technology (presentation, 27 slides) Kentucky Transportation Center - College of Engineering American Bureau of Shipping TWI Knowledge Summary 12 - Testimonials From: Sunil Kumar (e-mail removed for security) Dear Mr. Elia Levi, [...] I look forward to your advise and thank you in anticipation of your feedback.
From: Larry Williams (e-mail removed for security) Thank you Mr. Levi for the information, you have been very helpful.
13 - Correspondence: a few Comments 13.1 - New Correspondent cannot have learnt from previous discussions. Nonetheless it strikes me always again when I am asked for general formulas to calculate parameters for all sort of welding processes. It is unfortunate that such simplified formulas do not exist. Maybe in the future, if computer expert systems will be developed to deal with complex situations, with tens and hundreds of input data, they might be able to assist the welding engineer and shorten the time that is needed to get at least a starting point. 13.2 - Another Correspondent would like to get a simple method capable of suggesting the Consumables to be selected. It takes a welding engineer or a metallurgist to select welding consumables. It may be inconvenient, we agree.
14 - Bulletin Board 14.1 - Kiev Technical Trade Show 2007 14.2 - 16th Steelmaking Conference and 6th Ironmaking Conference 14.3 - Please accept our Invitation that you will find in our new page reachable by clicking on Welding Talk.
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Click on this Logo NOW! Copyright (©) 2007, by Elia E. Levi and See you next time... |
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