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PWL#114 - Welding Wrought Austenitic PH Stainless, Dissimilar Friction Stud Welding, Filler Metal January 31, 2013 |
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| We hope you will find this Letter interesting and useful. Let us know what you think of it. PWL#114
Welding Wrought Austenitic Precipitation Hardening Stainless, Dissimilar Friction Stud Welding, Filler Metal for Austenitic Precipitation Hardening Stainless, Steam Turbine new Materials, Oxidation and Exfoliation in boiler tubes, Brazing Magnesium (R), Brazing Steel (R) and much more...
February 2013 - Practical Welding Letter - Issue No.114
The Mid January Issue of Practical Welding Letter, Bulletin 81, dealing with Resources on Magnetic Pulse Welding was not distributed by e-mail but it is available at Bulletin 81 and from the Welding Resources Page.
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1 - Introduction 2 - Article - Welding Wrought Precipitation Hardening Stainless Steels - III 3 - How to do it well: Friction Stud Welding Dissimilar Metals 4 - Filler Metal for Austenitic PH Stainless Steels 5 - Online Press: recent Welding related Articles 6 - Terms and Definitions Reminder 7 - Article: New Materials for Steam Turbines 8 - Site Updating: Brazing Magnesium (R), Brazing Steel (R) 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contributions: Steam-Side Oxidation and Exfoliation in Boiler Tubes 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board (Sponsored Links) 1 - Introduction This 114th Issue of Practical Welding Letter opens with the third and last installment on the subject of Welding Precipitation Hardening Stainless Steels. Readers having interesting work experiences with these materials are invited to share them here by sending us a short note. Then there is the description of a research conducted on the suitability of friction stud welding for joining dissimilar materials, in this case steel to aluminum. It is interesting to remark that, while the research was based on the use of sophisticated equipment and means, the welds were done with a standard milling machine, without any effort to improve its friction welding performance. In section 4, dedicated to filler metals, some details are added on welding materials for those base metals described in section 2. Some guidelines remind how to select suitable fillers, depending on properties and requirements to be exhibited by the final fabricated objects. Then to two very important subjects are introduced, although possibly not necessarily of immediate interest for many readers, but nevertheless likely to enlarge the perspectives to understand mainstream trends. In this particular case, further to summaries of original articles reported in sections 7 and 11, the available direct links to the sources should be appreciated by curious readers. Profit from the uncommon chance to get glimpse of the work of researchers involved in the making of new things and of solving crucial problems hindering a speedier progress. The first article (7) introduces new materials allowing higher operating temperatures to steam turbines. The second one (11) describes a common deterioration process affecting boiler tubes. This problem is so complex that modeling the process through a rational description of the main contributing factors is still a difficult challenge. The Pages of this Month are revised and updated versions on Brazing of Magnesium and of Steel. Readers confronting problems on these and other subjects are invited to inquire if Welding Advisers can help them to find suitable solutions. This could bring up a subject and start a short note with useful information. The other usual sections can be found where expected. You can always use the Search function from almost every Welding Advisers page. You can also browse the Site Map or the Index Page to find references to the subjects you may look for. Titles of Articles from Practical Welding Letters can be found in the Welding Topics page. Links to the PWL complete list are available from the Index of Past Issues of PWL. The subjects treated in the Mid Month Bulletins are listed in the Please use the Contact Us form to send your comments, feedback or questions.
2 - Article - Welding Wrought Precipitation Hardening Stainless Steels:
This is the third article in the series. Austenitic Precipitation Hardening Stainless Steels include types A-286 and JBK-75. It should be noted that the first material was defined, in the past, an age-hardening iron base superalloy (not a steel), remarked for its high strength at elevated temperature, but the new definition (calling it a steel) is adopted by ASM Handbook Volume 6. A-286 is a high nickel alloy that solidifies from the molten state in the austenitic microstructure. Therefore it is prone to hot cracking upon welding also in the Heat affected zone (HAZ). Most of the use of this material is probably for non welded items. Welding grades of this material (AMS 5858 and AMS 5895) should be prescribed when this process is called for. Welding grades base metals differ from regular grades because of lower limits for sulfur and phosphorus content as well as for manganese and silicon. Best results without cracks are obtained with welding grade material in the solution treated condition, with low heat input and without restraint. Thin sheets can be welded by Gas Tungsten Arc process without filler metal. Thick material requires filler metal, which is available as regular grade, similar in composition to base metal but with lower limits for sulfur and phosphorus. Low heat input, low speed Electron Beam Welding (EBW) is successful on A-286 low restraint joints without filler metal, both on solution treated or hardened base metal. Resistance to hot cracking though, is higher for base metal in solution treated condition. JBK-75 is a modified version of welding grade A-286 with higher nickel percentage, that provides higher hot cracking resistance, especially in thicker sections. SAE AMS 5858D SAE AMS 5895E Filler metals for these materials are described further down this page in section 4. 3 - How to do it well: Friction Stud Welding of Dissimilar Metals A study was performed to explore the suitability of friction welding a steel stud to an aluminum plate. This research is reported at page 54 in the January 2013 issue of the Welding Journal. A regular milling machine was used for the program. It was used without a brake to stop the stud rotation. A 10 mm diameter medium carbon steel bar was used as stud. The 1060 Aluminum plate was 2.8 mm thick. Upsetting was done by manually raising the table with the machine crank. Notwithstanding the simple welding set up, the analysis of results was performed with proper testing instrumentation to measure upsetting load and joint separating force. Fracture and microstructure were studied by Scanning Electron Microscope with Backscattered electron image analysis system, and the interdiffusion behavior at the interface was examined by energy-dispersive X-ray spectroscopy (EDS). The force needed to pull out the welded stud was determined. Friction welded studs with upsetting, where mixed materials were extruded out of the joint, showed that the force needed at fracture was three times that without upsetting. The research examined and explained the appearance of a crack in the aluminum welded without upsetting. Such a crack was absent when upsetting was applied. Voids were absent and intermetallic compounds were minimal in the upset samples. This research, remarkably performed with a standard machine tool, demonstrated that stud friction welding of dissimilar materials can be a viable solution when required. Readers are urged to seek the original article referred to above. A similar unrelated research was performed elsewhere. The abstract of the article is reported hereafter. Investigation on Joining of Aluminum and Mild Steel by Friction Stud Welding 4 - Filler Metals for Austenitic PH Stainless Steels When needed, the following filler metals can be used to weld A 286 material (see above, section 2). Filler metals can be procured from regular grades (AMS 5804), with lower S and P but similar to base metal, or from premium quality filler metal wires (AMS 5805), to be preferred for critical welds. These, besides lower S and P are lower also in carbon, manganese, silicon and boron content, and have stricter limits on oxygen, nitrogen and hydrogen level. They are produced from vacuum induction melts by wire rolling instead of by drawing, and provide purer deposits less prone to hot cracking. Thick joints should be done with stringer beads. Alternatively, when maximum mechanical properties are not required, if only resistance to hot cracking is sought, a dissimilar filler metal like any one of the following:
Post weld heat treatment of A-286 should include solution treating for 2 hours at 1080 °C (1976 °F) followed by aging for 16 hours at 725 °C SAE AMS 5804G SAE AMS 5805H
5 - Online Press: recent Welding related Articles 5-axis waterjet cutting Structural steel automation at the end of the line Hybrid Laser-arc Welding Takes on Heavy Transportation Welding Fume Exposures and Controls: Do We Know Enough? IIW White Paper - Improving Global Quality of Life (183 pages) Note: - Interested readers may wish to download and see also the articles referred to in section 7 and 11 of this publication. 6 - Terms and Definitions Reminder Absorptive lens is a filter glass intended to reduce the effects of glare from dazzling light sources. Bevel radius is that of the rounded edge between the groove face and the root face of a bevel joint. Composite is a material consisting of two or more different materials solidly assembled together where each one retains its physical identity. Dip soldering is a soldering process where items are dipped in a bath of molten solder to get heating and solder filler metal in the process. Economics of welding operations consists in calculating or estimating accurately all the expenses, to be able to bid successfully and to set competitive prices. Face feed is the application of filler metal to the heated joint. Indication is the visual clue of a possible discontinuity, detected by a non destructive examination, which has to be further inspected. It may be an artifact to be dismissed as not reflecting a real flaw. Or it may be caused by a real discontinuity, in which case it must be interpreted, to decide if it meets or fails the limits for acceptance, established in the engineering requirements. Medium Vacuum Electron Beam Welding is a process variation where welding is conducted at a pressure between 10-1 to 3x103 Pascal (about 10-3 to 25 torr). 7 - Article: New Materials for Steam Turbines The development of new materials is a long and painful process. It requires substantial resources, provided by various national institutions, dedicated teams of highly qualified researchers, and a strong economic incentive. In the power generation industry the incentive is provided by the efficiency gains available from power turbines operating at higher metal temperatures. An article published in the January 2013 issue of Advanced Materials and Processes, an ASM International publication, at page 18, provides insight for interested readers not involved in actual application of the knowledge that is being accumulating on the subject. The next generation of advanced ultrasupercritical (A-USC) steam turbines, seems to offer the unprecedented opportunity of a very substantial thermal efficiency improvement, due to recent availability of new materials with higher properties. The improvement will translate in a reduction of 20% in emissions and fuel costs relative to the best presently available equipment, raised to 40% relative to older coal fired equipment. A number of new improved nickel base superalloys will allow inlet steam temperatures up to 760 °C = 1400 °F. The article indicates two proprietary alloys, Inconel 740 and Nimonic 105 of Special Metals Corporation, and one, Haynes 282, of Haynes International Inc. The article reports a number of references describing various aspects of the development phases and typical results from specific tests. No special problems are foreseen in producibility of the main turbine parts, mainly turbine discs and blades. Material properties of the new alloys were found to be stable in time, with the slow degradation taken into account by reference to the results of creep and creep-rupture tests. Low cycle fatigue properties are adequate for the intended use. Triple melted material ingots are evaluated for uniformity of microstructure and of properties. Interestingly, the article informs that the first implementations of A-USC technology using the new materials are expected to take place in India and China by 2020. Readers are urged to download and see the original article, See also: and:
8 - Site Updating: Brazing Magnesium (R), Brazing Steel (R) The Pages of this Month are revised and updated versions of short treatments of the subjects. The first one, on Brazing Magnesium should give sufficient information for permitting orientation on the subject and guide further queries on more specialized aspects. The second one, on Brazing Steel might help in identifying problems and the direction of possible solutions. Readers are urged to probe in depth this website and to ask us when in need of explanations. What hinders the formulation of a complete answers is generally the lack of sufficient data, but one or more rounds of asking details may be all that is needed to understand the problem. For any other subject on can always perform a search, by typing the requested terms in the box that appears in almost every page of the Welding Advisers website: that will include also the articles of the Practical Welding Letter, now at this 114th issue. Questions, comments and feedback are always welcomed. 9 - Short Items 9.1 - Metastable is said of a material not truly stable with respect to some transition, conversion, or reaction but stabilized kinetically either by rapid cooling or by some molecular characteristics as, for example, by the extremely high viscosity of polymers. Also of a material possessing a state of pseudo-equilibrium that has a free energy higher than that of the true equilibrium state. 9.2 - Neutron Embrittlement results from bombardment with neutrons, usually in metals that have been exposed to a neutron flux in the core of the nuclear reactor. In steels, it is evidenced by a rise in the ductile-to-brittle transition temperature. 9.3 - Oxidation is a corrosion reaction in which the corroded metal forms an oxide; usually applied to reaction with a gas containing elemental oxygen, such as air. Elevated temperatures increase the rate of oxidation. Also a chemical reaction in which one substance is changed to another by oxygen combining with the substance. Much of the dross from holding and melting furnaces is the result of oxidation of the alloy held in the air furnace. 9.4 - pH is the negative logarithm of the hydrogen-ion activity. 9.5 - Rockwell hardness number designates a value obtained by performing a Rockwell hardness test. 9.6 - Salt Fog (or Spray) Test (ASTM B117) is an accelerated corrosion test in which specimens are exposed to a fine mist of a solution usually containing sodium chloride, but sometimes modified with other chemicals. 10 - Explorations: beyond the Welder Hard Up: Nanomaterial Rivals Hardness of Diamond Right Again, Einstein! New Study Supports "Cosmological Constant" Chipmaker Races to Save Stephen Hawking’s Speech as His Condition Deteriorates Lithium-Ion Battery Fires Could Turn Boeing 787 Dreamliner into a Nightmare Apple Shouldn’t Make Software Look Like Real Objects 11 - Contributions: Steam-Side Oxidation and Exfoliation in Boiler Tubes The oxidation and exfoliation of scale on the inside of tubing carrying hot steam is a most critical problem in modern supercritical and ultrasupercritical power generation plants based on coal combustion. An article describing the effects of material deterioration during operation of power plants, and summarizing the efforts to understand and minimize the destructive consequences, was published in the January 2013 issue of Advanced Materials and Processes, an ASM International publication, at page 23. Steam temperatures are in the range 580 to 620 °C (1076 to 1150 °F) and pressures are up to 28 MPa (4000 psi). In advanced systems these values will soon reach 760 °C (1400 °F) and 35 MPa (5000 psi). Any material deterioration generating corrosion and erosion products can have a significant impact on plant operations. Exfoliation-related damage may include tube blockage and failures, erosion of drain lines, reduced steam turbine performance and increased maintenance of valve components. The National Physical Laboratory (NPL) and the Electric Power Research Institute (EPRI) held in 2012 a joint workshop calling together all people having an interest in managing and containing the damage. The purpose was to gather field experience, and to improve understanding of the phenomena for elaborating models suggesting better approaches. Production and modeling of oxide layers and of scale are being described in detail. The differences in coefficient of thermal expansion (CTE) among layers if oxide and base metal are the main drivers for exfoliation. The workshop findings are perplexing in that the complexity of the observations cannot be easily reduced to a few understandable factors. Much research is still needed. Readers are urged to download and see the original article,
12 - Testimonials From: David Westcott Just a quick note to say [...]. I enjoy welding yet many years have passed since last I applied those skills. [...] Thank you for your time and consideration. Keep up the good work! Respectfully Yours, Dave Westcott
Date: 14 Jan 2013, 04:39:37 AM On Mon Jan 14 04:34:40 2013, the following results were submitted from the
"Form 5" on welding-advisers.com: Name: Christophe Delaere I wish you the best for this year too! Christophe D. 13 - Correspondence: a few Comments I had recently an unusual experience with a new correspondent. He presented a situation where some uncertified old material was available and considered for use in a certain job. He gave a limited chemical analysis results and asked only if that material could be considered weldable. As I answered that the problem should be investigated in some more depth, he was confused by my response and confirmed that he was simply looking for the answer to what should be a simple question. He could not imagine that the problem was more complex than he figured out, and that additional information should have been provided before a responsible answer could be given to the original question. If you go to the doctor with the complaint of a disturbing symptom, you are not surprised if he sends you to a few additional tests or checks before prescribing a treatment, are you? So, what is so confusing in the request of more information? 14 - Bulletin Board 14.1 - WEMCO/RWMA Co-Located Annual Meeting. 14.2 - ASQ Lean and Six Sigma Conf. 14.3 - Weld Cracking Conf. 14.4 - Shelly Out Of The Shell?
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