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PWL#164, Updating Resist. Welding, SS Flame straightening, Soldered Joints Reliability, CWI Career April 03, 2017 |
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PWL#164
PWL#164, Updating on Resistance Welding, Using Flame to Straighten Distortions in Stainless Steel Constructions, Reliability of Soldered Joints, Promoting a Career as Certified Welding Inspector, Updating website page on Welding Duplex Stainless Steel, Keeping a Welding Logbook and much more...
April 2017 - Practical Welding Letter - Issue No.164
DON'T USE REPLY to send your messages! Use the Contact Us form instead. This publication brings to the readers practical answers to welding problems in an informal setting designed to be helpful and informative. You are urged to pass-along this publication to your friends, if you like it, and if you think they may enjoy it. The addresses reported hereafter were live and correct at the time of their publication. Note: References to articles or other documents are given here in one of two forms. If they are URL's (Uniform Resource Locator), which is the analogue of an address, they begin with "http://..." or "www.". 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.
1 - Introduction 2 - Article - Updating on Resistance Welding 3 - How to do it well: Using flame to redress distortions in stainless 4 - Filler Metal Reliability of Solder Joints 5 - Online Press: recent Welding related Articles 6 - Terms and Definitions Reminder 7 - Article: A Career as Welding Inspector 8 - Site Updating: Welding-duplex 9 - Short Items 10 - Explorations: beyond the Welder 11 - Contributions: Welding Log Book 12 - Testimonials 13 - Correspondence: a few Comments 14 - Bulletin Board
2 - Article - Updating on Resistance Welding
The Editorial, published at page 6 in the March 2017 issue of the Welding Journal, is a short reminder to everyone interested, of the huge progress that this process, invented more than 125 years ago, enjoyed all this time. It is still being actively researched, especially for new automotive applications using very thin steel or new aluminum alloys. From our point of view, we can testify to current continuing activity, by remarking that about ten articles related to resistance welding were referred to in these pages in a little more than one year. The Editorial briefly reminds Mid-frequency direct current (MFDC) resistance welding power supplies that replaced older transformers, and the new reversing DC mid-frequency transformer technology that improves spot welding electrode life. Also Capacitor discharge (CD) resistance welding power supplies are reminded as being offered now in much larger ratings than before: when equipping high force machines, they are often ideal for projection welding of large nuts, studs and rings. Favorable comments follow, regarding the progress reached in improving controls that, due to faster processing speeds, now have the ability to monitor several variables, such as nugget expansion, and compensate for variances on the fly. New copper alloys were introduced, capable to extend the time between electrode face redressing, especially when welding coated steel and aluminum. The Author concludes by reminding the importance of learning on the continuing progress of this important welding technology using all the available opportunities from AWS and RWMA, also for the new Certified Resistance Welding Technician (CRWT) examination due to be introduced by AWS within the next year.
3 - How to do it well: Using flame to redress distortions in Stainless Steels
The most useful Stainless Q&A Column written at page 20 by Damien J. Kotecki in the March Issue of the Welding Journal, reminds essential information one should keep in mind when tackling practical jobs to counteract distortion found in stainless fabrications after welding. The Author remarks that AWS published C4.4/C4.4M:2007, Recommended Practices for Heat Shaping and Straightening with Oxyfuel Gas Heating Torches. This standard provides guidance for any metal that can be welded, but it is meant mainly for carbon and low alloy steels. Locally heating a metal to perform flame straightening produces compressive stresses, resisted by the surrounding cold material, causing the heated material to upset. Upon cooling the now shortened material is shrinking, redressing curled or bulged areas. The above standard advises that regular stainless should not to be heated in excess of 800°F (427°C) surface temperature, because of the danger of sensitization (See https://www.welding-advisers.com/Welding-stainless.html). Remains the fact that if the material was indeed regular, and not of low carbon type, the welding of the distorted structure would have already compromised the corrosion resistance qualities of the material, because at least two strips surrounding the weld beads (heated in the dangerous temperature interval) would be sensitized and prone to corrosion. For the low carbon grades of austenitic stainless steel, the Author suggests not to exceed 1100°F (590°C) when using a flame to repair distortion. For martensitic and precipitation-hardenable types it is recommended to remain at least at 100°F (55°C) below tempering or aging temperature. The Author suggests to avoid flame straightening at all in case of ferritic or duplex stainless steels. He further reminds that any discoloration should be removed by chemical or mechanical means. Interested readers are urged to seek the original column as indicated above.
4 - Filler Metal Reliability of Solder Joints
Part 1 — Filler Metal Properties and the Soldering Process Part 2 — Reliability Performance The research opens with the observation that miniaturization and increased functionality of electronics made extraordinary progress in the past half century both for consumer use in portable devices and for advanced military hardware. In all case reliability must be assured as required by the application. Mechanical strength and conductivity are of foremost importance. Bulk properties of filler metals often affect reliability but configuration of the joint, clearance and surfaces determine flowability and fillet development, also essential to satisfactory performance. Reliability is also affected by the soldering process used to form the joint. Additional factors include base material dissolution, local changes to the molten solder composition and formation of interface reaction layers. The article reviews the most common soldering alloys, their fusion temperatures and their wetting properties at brazing temperature. The mechanical properties of the solder filler metal are critical factors in the overall performance and reliability of the joint. Due to the relative low solidus temperatures, creep and dynamic recrystallization readily occur even at room temperature. Although the bulk mechanical properties of the filler metal have a significant role in the strength of the solder joint, they are not always the only controlling factors: one has to consider the system including the base materials, the filler metal, and the reaction layers. The study thoroughly tested strength changes following additions of single metals in various amounts and proved that in certain cases solid solution with precipitation hardening occurs. Various outcomes relative to reliability result from different phenomena occurring during the process itself, like base metal dissolution, changes to filler alloy composition or formation of interface reaction layer. This part is summarized by remarking that the solder composition is selected to have the optimum mechanical properties for the application while reminding that the soldering process itself affects joint reliability. The flux and heating profile support wetting and spreading of the molten filler metal. However base material and surface finish dissolution can alter solder composition, which together with the interface reactions, will directly impact the long-term mechanical performance of the solder joint. In the second part, the study concentrated on factors that affect soldered joint reliability, like fatigue damage and growth of intermetallic compound reaction layers. One main factor affecting reliability is the growth of an intermetallic compound reaction layer at the solder/base material interface. In terms of mechanical response by the solder joint, for longterm performance fatigue remains the foremost concern. Thermal mechanical fatigue (TMF), a form of low cycle fatigue (LCF), occurs when temperature cycling is combined with mismatched values of the coefficient of thermal expansion (CTE) between materials of the solder joint system. Vibration environments give rise to high cycle fatigue (HCF) degradation. It nearly impossible to assess long-term solder joint performance based entirely on experimental measurements. Therefore, computational modeling has gained more favor replacing accelerated aging tests for predicting solder performance in the long run. Part 1 report can be downloaded from: Part 2 report can be downloaded from: Interested readers are urged to read the original articles, full of experimental details and discussion of results.
5 - Online Press: recent Welding related Articles New insights into solidification cracking during steel welding process Fiber laser welding technique joins challenging metals Connect - The magazine of TWI - Issue 01 2017 - Download from page: Experimental investigation of aluminium–copper wire crimping with electromagnetic process: Welding Equipment and Supplies: The Global Market
6 - Terms and Definitions Reminder Indentation, in a few resistance welding, is the depression left by the pressure of electrodes on the external surface of the workpieces. Joint is the junction of members or of their edges either before or after having been joined by welding, brazing or adhesive joining. Keyhole is a technique of welding in which a concentrated heat source penetrates completely through a work-piece forming a hole at the leading edge of the molten weld metal. As the heat source progresses, the molten metal fills in behind the hole to form the weld bead. Liquidus is the lowest temperature at which a metal or an alloy is completely liquid. Macroetch Test is done by examining with no magnification or by using low magnification, a specimen that is prepared with a fine surface finish and etched. Non sparking hand tools are forged from Beryllium Copper or Aluminium Bronze Alloy, physically tough and nonmagnetic, and can be safely used in environments where there are explosive vapors and gases. Orifice gas is that which is directed into the plasma arc torch or thermal spraying gun to surround the electrode. It becomes ionized in the arc to form the arc plasma and issues from the constricting orifice of the nozzle as a plasma jet. Pilot arc is a low current arc between the electrode and a constricting nozzle of the plasma arc torch used to ionize the gas and facilitate the start of the plasma jet.
7 - Article: A Career as a Welding Inspector
Deciding if and when embracing Welding Inspection as a new career may be challenging, as indicated in a short article published at page 36 in the March 2017 issue of the Welding Journal. Nevertheless it could be a welcome new stage for welders in good standing, wishing to improve their lot by enlarging their field of notions, the scope of their occupation, the amount of responsibility they are willing to accept and the take home pay. From time to time welders should check if their history up to that point makes them good candidates to become a Certified Welding Inspectors (CWI). If not yet, there are many ways a determined person can plan to improve preparation up to the point of taking the exam. One of the best is possibly looking for opportunities to talk with experienced inspectors and ask how did they reach their own certification, and what gains did the achievement provide. If you consider to check your own preparation on the Body of Knowledge, you may wish to download the page from aws.org/library/doclib/bodyofknowledge.pdf The practical experience a welder learns and gains by long years of work are an invaluable asset assuring a better comprehension to the body of knowledge the candidate must demonstrate to possess by passing the Certified Welding Inspector (CWI) examination. But of course the individual must be ready to undergo preparation and a three part examination needed to assess the degree of knowledge and understanding and the other qualities that make a good inspector, where work experience supplements qualifying education. The article recommends the materials that the American Welding Society (AWS) offers for preparation of candidates, from the online CWI Pre-Seminar to be found in the Education section in the www.aws.org website, to the seminars and additional learning aids built as helpful items for passing the exams. A welder's job should never be regarded as the final stage in a career, but instead as a preparation for a wider and more demanding occupation, likely to provide satisfaction for the higher responsibilities the inspector takes on, by approving any given operation, or by requesting repair of demonstrated flaws. Interested readers are urged to read the above mentioned article, and to contact the author if that would help them take the right decision.
8 - Site Updating: Welding-duplex We currently update our website pages as we include new articles, published in current or past issues of this publication (PWL) reviewing special aspects relative to arguments treated in existing pages. Our hope is that readers, who look for answers to their pressing problems, find new and interesting information on what they are curious about. But sometimes the hint is not obvious, unless it is stressed clearly in words. That is why the present note is written. In the note published above (3) the author of the referred article suggests to avoid flame straightening at all in case of ferritic or duplex stainless steels. This recommendation risks not to be heeded as almost invisible. Therefore we plan to add a clear note in the above page on Welding-duplex stainless steel, once this PWL page is published. Readers finding similar hidden recommendations in other pages are invited to call our attention to such situations, in order to help us make our website more useful.
9.1 - Gibs are Guides or shoes that ensure the proper parallelism, squareness, and sliding fit between metalforming press components such as the slide and the frame. Usually adjustable to compensate for wear and to establish operating clearance. 9.2 - Hard Drawn is an imprecise term applied to drawn products, such as wire and tubing, that indicates substantial cold reduction without subsequent annealing. 9.3 - Immersed-electrode Furnace is one used for liquid carburizing of parts by heating molten salt baths with the use of electrodes immersed in the liquid. 9.4 - Joint Clearance is the distance between the faying surfaces of a joint. In brazing, this distance is referred to as that which is present before brazing (controlling capillarity action) at the brazing temperature, or after brazing is completed. 9.5 - Kiln is a large furnace used for baking, drying, or burning firebrick or refractories, or for calcining ores or other substance. 9.6 - Lath Martensite is that formed partly in steels containing less than approximately 1.0% C and solely in steels containing less than approximately 0.5% C as parallel arrays of packets of lath-shape units 0.1 to 0.3 mm thick.
10 - Explorations: beyond the Welder One reason young people don’t go into science? We don’t fail well NASA Satellite Catches Star's Death by Black Hole What Rural Alaska Can Teach the World about Renewable Energy Food for Thought: Do We Owe Our Large Primate Brains to a Passion for Fruit? California Forges Ahead with Clean Cars Rules 11 - Contributions: Welding Log Book by George Boykin Let me introduce myself, my name is George Boykin and I currently live in the beautiful state of Alaska. I love to hunt, fish, camp, hike and do all the other wonderful things one might think of doing in such an amazing state. However, I’m a southern boy at heart. Born and raised in Arkansas, I left for the Navy at the ripe age of 21 and got to travel the world a little bit. I served as an aviation structural mechanic on various aircraft platforms. A lot of the work I performed on the aircrafts were hydraulics and pneumatics. However, I was extensively taught and trained in aluminum fabrication. After separating from the military I went to a trade school and went through a structural welding program and a pipe welding program. Before I even graduated I got hired on by one of Alaska’s major contracting companies. For the past number of years, I’ve become a seasoned journeyman pipe welder in the oilfields of North Slope Alaska. I’ve worked for big name oil companies and thought to myself, "I should start keeping track of the various welds I make" just for continuity within the company in which I work. According to AWS D1.1 the welder must keep documentation of welds made in order to keep their certifications current (continuity). They shall not go longer than 6 months without a record of that specific procedural weld in which they are certified. Simply put, it's a log book. Similar to a truck drivers log book or a security guard log book. I noticed the lack of welding log books on the market that were available for the public to purchase. [Therefore the Author decided to write one - Note of the Editor] Not only is the book perfect for continuity, it can be a great "portfolio" for prospective employers to show them what the welder has actually worked on over the years or what procedures in which they have been certified. The book is 100 pages in length and should last for a while, especially if only logging for continuity. When you open to the first page of the log document you will find a place for you to put that date, probably one of the most important aspects to a welding log. Next, you will find a place to put the company, contractor, employer or a local union. It will have a place for the address of whichever you will be using. Now to the meat and potatoes, so to speak. The next bit of information you can record includes: • The welding process (GTAW, GMAW, SMAW, etc). • The position of the weld (1-4G, 1-4F, etc.). • The joint design (flare groove, double bevel, single bevel, etc.). • The electrode/filler metal (7018, 6010, ER 80S-Ni1, etc.). Then comes the verification from a qualified person(s). There’s a place for you to record your welder stencil or ID number and dates in which you worked at that establishment or job as well as a place for the qualifying individual to sign off certifying that the information contained is to be true and correct. A certified welding inspector (CWI), inspector or supervisor can sign for as a qualifying individual. Lastly, the bottom section of the page has a place for notes. You can put helpful reminders such as amps, volts or special techniques used for that particular weld. Or if the qualifying individual needs to make a note he/she can do so. The book can be purchased on Amazon and is prime eligible. The cost is relatively low, considering how long the book will last. Check for it at Amazon's Books, Welding Log -------------- Note: I believe this is a good example of thinking, taking initiative and then accomplishing the task.
Everyone should be encouraged to think and to take initiative.
I am grateful to George who gave us the opportunity to share it with our public. Congratulations!
I would like to spur other people who took on something new, to share it here with our readers, to give ideas of new endeavors.
Logbook Sample Page
12 - Testimonials Name: Jetha Zuher Details: Hello,
13 - Correspondence: a few Comments For those who may have some observation or experience to share here with our readers, we invite them to contribute by sending us short notes to be considered for publication. Also comments or feedback on what appears in theese pages are welcome interventions. An example can be seen above (11), and everyone is invited to join.
14 - Bulletin Board
14.1 - 2nd Codes and Standards Conference (API, ASME, AWS, NACE) 14.2 - 10th Shipbuilding Conference 14.3 - National Robotic Arc Welding Conference.
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