PWL#081 - Move to Robotics, Welding Stainless to Nickel, Spot Brazing, Titanium Surface Treatments, EBW Tips, Outsourcing, Duplex Spot Welding, Cutting Economy, Precommissioning and more...

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1 - Introduction

2 - Article - Transition to Robotics

3 - How to do it well: welding Stainless to Nickel alloy 600

4 - Filler Metal for Spot Brazing Titanium to Nickel

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article - Surface Treatments for Titanium

8 - Site Updating: EBW Tips, Outsource Welding

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Spot Welding Duplex Stainless

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board

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1 - Introduction

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This 81th issue of Practical Welding Letter opens with a reality warning against unwarranted excessive optimism towards the introduction of robotics in a working shop. This does not mean that the move is reckless, only that it must be prepared cautiously and thoroughly leaning on a strong in-house welding engineering presence.

A few queries addressed the problem of welding Stainless to Nickel alloy 600. Although the details of the applications sought are not known, some general recommendations are given in section 3.

The research reported in section 4 can be an eyes opener for similar situations where unconstrained ingenuity may suggest trying new ways to obtain acceptable joining results.

Looking for suitable advanced surface treatments for titanium parts may be difficult. Here a few proprietary processes are reported from an article describing remarkable results.

The Pages of the Month are dedicated to two quite different subjects. For those just approaching Electron Beam Welding a few Tips are indicated, involving recommendations likely to be of some interest.

For welding shops caught in a surge in orders and hampered by limited capacity, Outsourcing can be a way out of the difficulties. As usual with many other temporary solutions, benefits must be checked and balanced against liabilities.

Important facts about resistance spot welding of Duplex stainless steel, gleaned from a most informative and reliable source, are reported for interested readers in section 11.

The usual other columns can be found where expected.

Information available on the site is now quite large and some effort may be required to find it out. But the Site Map, the page on Welding Topics, the page of Weld FAQ, the page of Welding Resources should be of help.

Finally one can always use the search facility provided by Google on every website page.

If nothing else helps, readers can use the Contact Us form to let us have their questions, comments and feedback. (Don't use Replay).

2 - Article - Transition to Robotics.

The transition of a welding shop from manual operation to robotics performed production need not be a traumatic and painful experience. It is however a fact that, if management has inadequate understanding of the special requirements, the achievements fall often short of the programmed plans.

A recent article stresses the main point, already raised in different occasions, that the essential difference between failure and success consists in the absence or the presence of a strong welding engineering force within the manufacturing shop introducing robotic facilities.

See:
Turnkey Illusions – How to Avoid Pitfalls When Outsourcing Welding Automation
http://weldsparks.wordpress.com/2010/04/06/turnkey-illusions-avoid-pitfalls-when-outsourcing-welding-automation/

The needed equipment is selected, put together and organized by an Integrator, an outside supplier partner.

According to the writer, Brian Dobben, it is a faulty myth for the welding shop management to believe that the integrator is the expert and that the purchase of high-performance welding automation could be obtained as a turnkey solution without critical input from their in house experts. Furthermore they may deceive themselves that robotics would relieve them from bothering with daily welding problems.

If they lack such professional welding expertise, a cautious management should recognize that, and build a strong one before attempting the robotics transition.

The main point of the above article, and a refreshing one for a retired welding engineer like me, is a correct appraisal of the function, capability and responsibility of such a Smart Welding Engineer, that is the only one qualified to work with the integrator for specifying and accepting the next welding robot.

In addition to management misconceptions, it is disappointing and utterly misleading, on the part of respected suppliers, to pretend that their robots will work continuously, much more than their human counterparts, because unscheduled stops are the main cause of limited profitability of robotic cells. Such hindrances may be due to so many factors that only the strong presence and expertise of highly qualified professionals can mitigate and reduce.

To see our page introducing this subject click on Robotic Arc Welding. For our Resources page providing several useful links, click on PWL#060B.

3 - How to do it well: welding stainless to nickel alloy 600

Some recent queries asked for information on welding stainless to nickel.
As the queries did not specify the request in more detail, given the rich variety of stainless steels and also the different types of nickel base alloys available, this note will refer to austenitic stainless steels and to nickel base alloy 600.

The following indications may provide some orientation but one should keep in mind the service conditions and check if the proposed filler metal selection is suitable to the applications considered.

You may wish to see also our page on Welding Nickel that includes two tables of Filler Metal chemical compositions, and also a short note on Filler Metals for Welding Nickel published (4) in the Practical Welding Letter PWL#062.

For the dissimilar welding of austenitic stainless steel to nickel alloy 600 the following filler metals are recommended.

Welding Electrodes per AWS A5.11:
ENiCrFe-2, ENiCrMo-3, ENiCrCoMo-1, ENiCrFe-3

Welding bare rods per AWS A5.14:
ERNiCr-3, ERNiCrFe-7, ERNiCrMo-3

4 - Filler Metal for Spot Brazing Titanium to Nickel

Welding Titanium to Nickel can be challenging because of the different properties and characteristics of these commercial pure metals of such dissimilar joints. Results of a research were recently released, reporting on the combination of resistance spot brazing for lap joints of such sheet metals and the use of an interposed brazing alloy.

The brazing filler metal used in this study was 71Ag-28Cu-1Mg, (a modified Ag72-28Cu eutectic), as a foil of 0.1 mm, while the base metal sheets were 0.5 mm.
The joint strength was tested in shear as usual for spot welded lap joints and acceptable values were found, higher than those obtained without filler metal.

Correlation was sought between current/spot-size and shear strength. The use of the brazing filler metal permitted to obtain sound nuggets without porosity.
The interesting combination of spot welding technique with the use of a brazing alloy may allow useful solutions also with different materials.

Interested readers can find the report at page 101-s of the Supplement to the Welding Journal of the May 2010 issue.

5 - Online Press: recent Welding related Articles

Connect - March/April 2010
http://www.twi.co.uk/content/conmar10.pdf

Think before you Integrate (in robotic welding)
http://www.thefabricator.com/article/automationrobotics/think-before-you-integrate-in-robotic-welding

Pulsed GTAW for Stainless Steel
http://www.thefabricator.com/article/arcwelding/pulsed-gtaw-for-stainless-steel

Remote Visual Inspection Basics
http://files.aws.org/itrends/2010/01/it201001/it0110-17.pdf

TIG IT: How a TIG Welder Works and When to TIG Weld
http://www.millerwelds.com/resources/articles/TIG-GTAW-welding-with-Sleepy-Gomez-aluminum-chrome-moly-motorsports/

6 - Terms and Definitions Reminder

Arc Stud Welding is a process generating heat by an arc between a stud and a workpiece, and using pressure to drive together the parts as soon as sufficiently heated.

Bonded Flux used for Submerged Arc Welding, is a granulated mixture of powdered ingredients and a bonding agent, obtained by baking without melting and processing to the right size.

Complete Joint Penetration Weld extends through the joint thickness in a groove weld.

Deposited Metal is in general filler metal added to the joint.

Fitup is the condition of parts prepared for being welded together.

Gradated Thermal Spray Deposit is formed by layers of progressively changing proportions of mixed powders from the substrate to the surface.

Outgassing is the natural evolution of gas absorbed in a metal when heated under vacuum.

Overwelding results from excessive metal deposition causing unnecessary extra costs.

7 - Article - Surface Treatments for Titanium

Titanium alloys are light weight materials displaying remarkable mechanical properties and superior corrosion resistance. However, due to their low hardness, they are subject to excessive wear and erosion if used without surface protection, and can develop cold welding in contact with other metal surfaces.

Patented thermal processes in presence of specially formulated liquids develop diffusion protective layer with superior hardness (65-70 HRC), surface wear and friction resistance on Titanium components of almost any geometry and size, enabling wider use of Titanium in various applications.

The exposition of such promising results is published in the article published in the May-June 2009 issue of Heat Treating Progress, an ASM International magazine, freely downloadable to all from the ASM Site.

In these processes the metal components are subjected to intense direct inductive or resistive heating and subsequent cooling while a specially formulated cold liquid is sprayed in the working chamber.

The essence of the patented method is the dissociation of the special liquid mixture, providing a gaseous phase, containing a large amount of atomized performance-enhancing, highly active alloying element(s), in intimate contact with the hot surface being treated.

Heating is generally provided by controlled duration and temperature: the alloying elements are rapidly absorbed and diffused into the metal surface to the desired depth, creating a protective surface layer with superior hardness, strength, wear, erosion and corrosion resistance.

The products of the liquid medium dissociation also insulate and protect the treated component from oxidation and contamination by the environment.

Interested readers are urged to seek the original article indicated above.
http://asmcommunity.asminternational.org/portal/site/hts/AsmStore/ProductDetails/?vgnextoid=a96c28c1efc01210VgnVCM100000621e010aRCRD

8 - Site Updating: EBW Tips, Outsource Welding

The Pages of this Month are dedicated to two quite different subjects. For those just approaching for the first time Electron Beam Welding a few Tips are indicated, involving recommendations likely to be of some interest.

Click on Electron Beam Welding Tips to see this page.

Even if demand is dwindling, for welding shops caught of a sudden in a surge in orders and hampered by limited capability, Outsourcing can be a way out of the difficulties. However caution must be used. As usual with many other temporary solutions, benefits must be checked and balanced against liabilities to avoid losses.

Click on Outsource Welding to find this page.

Check regularly for new pages in the Web Site Map or subscribe to the RSS feed using the instructions given in every page (www.welding-advisers.com) under the Navigation Bar.

For finding what you look for, you may use the Google Search Box which appears in almost every page of the website. More often that not there is some reference to your subject either in the website or in the collection of Practical Welding Letters.

And if you do not find what you need you can always Contact Us using the usual form.

9 - Short Items

9.1 - Electrolytic Cell is the complex of a container with electrolyte, electrodes and a power source, suitable for performing electrolysis.

9.2 - Emissivity of a material is the relative ability of its surface to emit energy by radiation. It is the ratio of energy radiated by the unit area of a particular material to energy radiated by a black body at the same temperature.

9.3 - Grain Flow is the pattern of fiber lines on polished and etched sections of forgings caused by orientation of the constituents of the metal in the direction of working during forging. Suitable grain flow produced by proper die design can improve mechanical properties of forgings.

9.4 - Lubricant is a substance at the interface between two surfaces in relative motion for the purpose of reducing friction and wear between them. Also a material applied to metalworking tools like dies, molds, plungers, or work pieces that promotes the flow of metal, reduces friction and wear, and aids in the release of the finished part.

9.5 - Microhardness Test is made by forcing a diamond indenter of specific geometry, under a test load of 1 to 1000 gram-force, into the surface of the test material and by measuring optically the dimensions of the resulting microindentation.

9.6 - Necking Down is the localized reduction in cross section area of a specimen during tensile deformation.

10 - Explorations: beyond the Welder

Thinking Outside of the Toy Box:
4 Children's Gizmos That Inspired Scientific Breakthroughs [Slide Show]
http://www.scientificamerican.com/slideshow.cfm?id=toy-box-tech&photo_id=8D266841-D998-314A-FC64BA5165EA5F6A

The Ethical Dog
http://www.scientificamerican.com/article.cfm?id=the-ethical-dog

The Human Genome at Ten
http://www.nature.com/nature/journal/v464/n7289/full/464649a.html

Video of a Solar Prominence (Video)
http://science.nasa.gov/media/medialibrary/2010/04/21/30mar10_prom_304_quicktime.mov

Failure to Yield - Evaluating the Performance of Genetically Engineered Crops
http://ucsusa.org/food_and_agriculture/science_and_impacts/science/failure-to-yield.html

11 - Contributions: Spot Welding Duplex Stainless

A very important clarifying contribution was published by Damian J. Kotecki in the Stainless Q&A Section of the May 2010 issue of Welding Journal, at page 24.

Duplex Stainless Steels depend on microstructures for displaying the properties and characteristics sought for. As resistance spot welding produces generally microstructures corresponding to very rapid cooling rate, users employing Duplex alloys should carefully evaluate if the spot welds obtained in their operations are suitable for the intended applications.

In particular the cooling rate may be so high that the microstructure becomes almost completely ferritic, with practically no austenite present. This situation would show brittle spot welds. Furthermore, as nitrogen has no time to diffuse into austenite and to stabilize it, the precipitation of chromium nitrides would deprive the metal of chromium, damaging the corrosion resistance.

Experimenting with Post Weld Heat Treatment, produced with the repeated application of additional low current cycles in the same spot weld setup, can increase the proportion of austenite and reduce that of ferrite, with favorable results relative to performance in service conditions.

In principle it should be possible to experiment also with preheating with low current cycles, as this treatment too would decrease the cooling rate. In any case testing is essential for ascertaining an acceptable outcome.

Interested readers are urged to seek the original publication indicated above.

12 - Testimonials

On Thu Apr 01 09:07:56 2010, the following results were submitted from the "Form 5" on welding-advisers.com:

Name: Paul Ipolito
E-mail Address: removed for security
Country: United States
Introduce Your Organization: SPX Flow Technology
Describe Your Responsibility: Profit Enabler
Re: PWL#080
Questions and Feedback : Another great issue!!

Paul

On Fri Apr 16 10:41:28 2010, the following results were submitted from the "Form 5" on welding-advisers.com:

Name: Marcel Bauer
E-mail Address: removed for security
Country: Canada
Introduce Your Organization: MCBCM (Marcel Charles Bauer Custom Metalwork)
Describe Your Responsibility: Fabricator/welder
Questions and Feedback : Hi!

Just a note thanking you for the information in your Practical Welding Letters.

I always learn something new and I really appreciate what you do!

Thank you very much,

Marcel Bauer

13 - Correspondence: a few Comments

13.1 - A correspondent asked:

"Sir, My question is directly related to cutting of steel plate.
My project is the dismantling of military vehicles for the end result of selling the material as scrap.
Some of the material can be in 11-15 in. thickness and I would appreciate your input in what would be the most cost effective way of cutting this thickness of material."

A meaningful answer cannot be given with only this input.

The cost effectiveness should take into account many parameters.
See the following article:
http://www.thefabricator.com/article/tc/making-sense-of-metal-cutting-technologies

A commercial provider (http://www.teskolaser.com/index.html) gives the following answers:

Deciding which metal-cutting system is best.

There are so many variables to be considered when making a decision on the right cutting system to use, it is often a difficult analysis. The metal processor and, to some degree the end-user of the material, must consider at least some of the following issues:

• Cutting speed (the higher the better)
• Capital investment (depends on solution)
• Operating costs (to be determined)

• Size of heat affected zone
• Access to secondary machining processes
• Edge cleanliness
• Degree of tolerance required
• Number and types of metal to be cut

There is no one overall answer to the question "Which metal cutting system is best?" The factors that are important to one metal processor will be different from those of another depending on their customers’ needs. The "best" metal cutting process depends on the material to be cut and the final application of the material. No one cutting system is superior to another in all major comparison categories.

The following article may dispel some doubts:

Plasma Cutting: Determining if it's Right for You and What to Look for in a Machine
http://www.lincolnelectric.com/knowledge/articles/content/plasma.asp

13.2 - Another correspondent asked:

"What is the list of required documents at mechanical completion book before precommissioning for storage tank after full construction? If any references exist, please conduct me. Best regards."

My answer:
The requirements should be spelled out in the procurement document, in the relevant code or in any additional document referring specifically to precommissioning of storage tanks.

That may vary depending on the location (on land or at sea) and purpose of the tanks (gravity loaded or under pressure) and on the fluid they are designed to contain.

Specifically referring to welding the list should include, besides the Company Quality Manual and Qualification by Regulating Authorities:
Welding Procedure Specifications (WPS)
Procedure Qualification Records (PQR)
Welder Qualification Test Records.

Readers capable and willing to expand on these issues are invited to kindly provide more complete answers.

14 - Bulletin Board

14.1 - SME Annual Conf. - Bridging the Gaps
June 6-8, 2010 - Sheraton Music City, Nashville, Tenn. USA
www.sme.org/conference

14.2 - New Welding Technologies Conf., The Key to Higher Productivity
June 15-16, 2010 - Fort Lauderdale, Fla. USA
www.aws.org

14.3 - LOET 2010, 9th int'l Conf. on Brazing, High-Temp. Brazing & Diff. Bonding
June 15-17, 2010 - Aachen, Germany,
http://www.dvs-ev.de/loet2010/

14.4 - Make Your Knowledge Sell! (Free Download)
http://myks.sitesell.com/Quark.html

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