Intelligent Process Control, Welding Unknown Metals, Undermatched Weld Metal, Digital Imaging - A Powerful Quality Tool, Advances in Thermal Spray, Weld Porosity, Steel Finishing 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.
Don't miss it!

1 - Introduction

2 - Article - Intelligent Process Controls

3 - How to do it well: Welding unknown metals

4 - Filler Metals: Undermatched Weld Metal

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article - Digital Imaging: A Powerful Quality Tool

8 - Site Updating: Weld Porosity, Steel Finishing

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Advances in Thermal Spray

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board

(Sponsored Links)

1 - Introduction

Hello Everybody! This 91th issue of Practical Welding Letter opens with a review of a most interesting article that shows recent applications of laser used for tracking seams but also for keeping quality under control. Other uses are explained, albeit not in complete detail, but there is enough for curious readers to go and find out if there may be any benefit for them.

The answer to a question on how to weld unknown materials appears to be self evident, but somehow it did not dawn on the inquirer. It may be useful to think of it.

Undermatching should not be a mysterious concept. It may be the key to difficult to weld high strength steels prone to cracking, but the proposed solutions must be tested and qualified.

Then there is some information on Quantitative Metallography including sources of more details. It can be used as a powerful quality control tool. Recent developments simplify and automate the tasks of keeping production under control and enhance reliability.

Advances in Thermal Spray start obviously in the lab, and it takes time until new ideas are translated in practical applications, nevertheless it should be important to have some ideas on what is going on.

Finally the Pages of this Month: one is a general presentation of Weld Porosity, its main sources when welding, and what can be done about, the other is a short review of the many processes available for Steel Finishing. Designers not particularly knowledgeable with these subjects should find pertinent information for all their productions, they simply cannot leave the issues undecided.

Finally the usual departments can be found at their usual place. Readers are invited to send their feedback, and possibly also contributions, short notes on their experience: real stories can be really interesting. Let us have your feedback and comments using the Contact Us Form.

The references to online resources, assembled in this issue for the Mid Month Bulletin, that follows the regular issue, are devoted to Metallography and Quantitative Metallography, subjects likely to be relevant to those who need in depth understanding of features or flaws in their production.

2 - Article - Intelligent Process Controls

An Article published on page 46 of the February 2011 issue of the Welding Journal presents interesting and potentially advantageous developments in automated welding solutions. The Author, Jeffrey Noruk, describes the use of laser vision sensors for joint finding, joint tracking and automated weld inspection for shipyard construction.

The use of those sensors permits to deploy flexible, adaptive welding systems, capable of avoiding the biggest causes for poor welding productivity, namely excessive variability in parts and fixturing. Laser vision permits to compensate for large variability by controlling the automated process as needed. The same system if properly programmed, may not weld if the preparation is out of tolerance.

Another development involves a hand held laser scanning inspection system, designed to perform visual inspection, consisting in objective weld feature measurements for Pass/Fail decisions and Statistical Process Control (SPC) for analysis and improvement.

The same system helps to reduce overwelding and therefore limits distortion and saves the cost of not needed consumables. The automatically issued report provides the requested evidence for eliminating redundant overinspection.

Such a GMAW (Mig) system with adaptive controls uses a laser vision joint tracker for checking that the weld joint is within tolerances, tracking it in real time, and controls the weld process optimizing weld quality at maximum travel speed.

A similar system developed for Laser Hybrid Welding Closed Loop Control measures the weld bead shape just after solidification and feeds information back to give continuous corrections. The article relates that "the travel speed and the laser or GMAW parameters can be adjusted automatically as needed".

This simple conclusion depicts such an ideal situation that seems too good to be real. To be capable of simultaneous correlated control of so many independent parameters the system should have an enormous capability of adaptive control and it should represents a major achievement in Artificial Intelligence (AI).

I must say that I was somewhat disturbed by the assertion above. Therefore I wrote to the author asking for details. He was so kind to answer me immediately, putting the whole thing in proportion.

Here is his relevant sentence:
"What I describe in this article is something done by only a couple of our customers where they measure the finished weld in real time and then look at the results to determine if the weld is the right size and quality and then if not, adjust the welding parameters based on predetermined weld schedules that have been developed for this condition. Therefore it is not really an Expert system but more of a look up table that is deployed."

I am grateful to Mr. Noruk for having dispelled the doubt. Nevertheless it is a great achievement that could be transferred to many other applications. This progress is worth of attentive follow up.

The last innovation presented is a mobile welding robot that can be brought by the welder to the component and put to work automatically. It is also worth mentioning. The actual operation of this mobile system is not described in any detail in the article but a more complete presentation can be found at:
http://www.servorobot.com/uploads/media/Newsletter_October_2009_MWR-350.pdf

It is affirmed that it allows the welder to concentrate on the process and fine tune parameters. This too should be followed up.

Interested readers are urged to seek the original Welding Journal article as indicated above.

3 - How to do it well: Welding unknown materials

Q: I am attempting to tig weld together two apparently dissimilar aluminum alloys.
Also, one of them has a 3mm wall thickness and the other one a 10mm thickness.
Neither piece is cast, but both are billet machined.
I cannot start an arc pool on the thicker material, do I need to preheat the part, and how do I avoid oxidation during the pre-heating process?
I am worried about using higher current flows because I do not want to destroy the more delicate piece.

A: Why would not you try the right way to do welding?
You have unknown materials. Please identify them. Only then, once you know what materials they really are, can you look for a suitable welding method.
See my page:
https://www.welding-advisers.com/Material-identification.html

I recommend that you try to locate a source of x-ray fluorescence analysis (qualitative), and that you request also hardness test for both parts.

P.S. - It is known and should be always remembered that certain aluminum alloys are not fusion weldable, although they may be welded by resistance welding or by other methods. Typical examples are the alloys 2024 and 7075 that should never be fusion welded. See Aluminum Welding.

4 - Filler Metals: Undermatched Weld Metal

An instructive explanation of this expression and a guide to its application is available in an AWS Q&A document available at
http://www.aws.org/wj/dec02/feature1.html

In short it is the use of consumables producing welds with lower Yield Strength than that of the base metal. Such welds are typically more resistant to cracking in fabrication.

This concept was also briefly addressed in Issue 69 of Practical Welding Letter for May 2009, in section 4. Click on PWL#069 to see it.

Considered application of these principles was applied in a thorough and advanced development program for the production and testing of a new steel, essentially an improved version of HSLA-100 called HSLA-115, developed at the request of the US Navy.

HSLA means High Strength Low Alloy and the number indicates the minimum Yield Strength of the materials expressed in ksi (1000 pounds per square inch). The concurrent requirement was that the same ductility and notch toughness as obtained in HSLA-100 (Comp. 3) be maintained.

An extensive article relating the efforts dedicated to this major project, based on a paper presented at the last FABTECH the past November 2010, was published at page 34 of the February issue of the Welding Journal.

The base material development consisted in refining the special processing with more stringent requirements, otherwise maintaining the same chemical composition already developed for HSLA-100. The special processing included continuous cast slabs, low reheating temperature, double austenitizing and lower temperature aging.

The specified characteristics were achieved and demonstrated by thorough testing. In January 2009 the Navy authority (NAVSEA) approved HSLA-115 for use in plate production.

Then fabrication capabilities and weldability had to be verified. The requirements were defined, but the welding procedures adopted in the test were those already approved for HSA-100.

For testing dynamic fracture performance, weldment explosion testing were used of two types: crack starter and bulge. These tests were performed on specimens welded by three different processes, with the undermatching consumables, but specifying a high heat input (worst case conditions) to verify weldability in difficult situations.

The tests performed, verified the suitability of using approved undermatching consumables and procedures for welding the new steel HSLA-115, thus meeting the goals established for the development program.

Interested readers are urged to seek the above article for understanding the development process and the reasons informing the decisions adopted.

5 - Online Press: recent Welding related Articles

Steel nanotechnology can reduce the weight of our cars
Autoblog.

Superalloys
ASM.

Engel integrates welding into the moulding cycle
European Plastics.

Ask for your free copy of the Orbital Welding Handbook!
Polysoude.

Laser additive manufacturing enables next generation parts
Opto IQ.

6 - Terms and Definitions Reminder

Composite Thermal Spray Deposit is made by forming layers from two or more different sprayed materials.

Diffusion Aid is a different solid filler metal applied between faying surfaces to assist in diffusion welding.

Emissive Electrode is a filler metal electrode, simple or composite, with a very light coating of emissive material for promoting a stable arc.

Filter Plate is an optical protective material intended to defend the eyes from excessive light radiation in the ultraviolet, visible and infrared part of the spectrum.

Meltback Time is the interval, at the end of crater filling time to arc outage during which electrode feed is stopped.

Noncorrosive Flux for soldering, nor any residual thereof, has any corrosive action on the base metal.

Rough Threading (thermal spraying) is a method of surface roughening by cutting threads and then jagging and tearing their sides and tops.

Split Layer Technique deposits more than one bead per layer.

7 - Article - Digital Imaging: A Powerful Quality Tool

A short introduction to Quantitative Metallography was presented (9.4) in Issue 25 of Practical Welding Letter for September 2005. Click on PWL#025 to see it.

Digital imaging of metallographic pictures captured from a microscope permits rapid automatic and precise quantitative metallography, that up to a few years ago had to be performed manually, slowly and with low repeatability.

Comparison of microstructures, measurement of features even along multiple successive exposures, composite pictures assembled from different ones focused a different depths, checking of shape and size of phases, are only a sample of the various data that can be extracted from suitable photos.

Distribution of pore sizes, porosity level, identification of object of interest, automated image analysis, evaluation of duplex grain distribution, boundary definition and manual interactive (software assisted) evaluation.

Measurements requiring calibration are used for determination of depth of features (surface roughness, decarburization or carburization, layers, diffusion, corrosion), intercept count (according to standards), grain size determination, cleanliness, banding, hardness testing, second phase distribution, weld penetration.

Quality control requires compliance to standards in the determination of different features.

Benefits of imaging: enhanced image capture, efficient qualitative and quantitative analysis, international standards compliance, reliability, secure database storage, rapid report generation.

A webinar on the above subject is available online from the ASM website. From the page
http://www.asminternational.org/portal/site/www/news/webinars/
Click on the title above to reach this interesting presentation or any other that might interest you.

An article with the same title above (Digital Imaging: A Powerful Quality Tool for Materials Analysis) was published in the last (February) issue of Advanced Materials and Processes, an ASM International publication, at page 19. See it at
ASM.

See a collection of Resources on Metallography and Quantitative Metallography in the Mid March Bulletin No. 59 appended as PWL#091B after the end of this publication and reachable by scrolling down.

8 - Site Updating: Weld Porosity, Steel Finishing

The Pages of this Month refer to two unrelated subjects, although if you look really hard you can almost always find a connection.

The first originated from a Query, suggesting that a basic exposition of types and remedies for porosity generated while welding could find a place in the reference files of some readers. This page can be read now by clicking on Weld Porosity.

The second page summarizes the various finishing processes that are used to protect steel items from rust and corrosion once they are manufactured and ready for shipment or for use. Depending on application and service conditions various solutions are available. Finding the most suitable and the most economic that meets requirements may be more difficult than imagined.

Therefore new designers still not much familiar with the subject, are urged to ask, to seek advice or to obtain information from dependable sources. The relevant page is found at Steel Finishing.

Generally the updates are announced in our Welding Blog also available at a service to which any reader may subscribe to stay updated. See instructions below the Navigation Bar at the top left of each page from our website.

Updates can also be found in our pages Site Map and Index Page built to let readers find easily what they may be looking for. Except that these days the Site Map is undergoing a major revision because of a few errors that were remarked. It should be up again in a few more days.

You are urged to inform your friends of this website: they may benefit from the quite extensive information available to all readers and can ask questions that may help them.
Let us have your comments on the form of the Contact Us page.

9 - Short Items

9.1 - Low Alloy Steels is a class of ferrous materials with mechanical properties, obtainable through suitable heat treatments, superior to plain carbon steels as the result of additions of such alloying elements as nickel, chromium, and molybdenum. Total alloy content can range from 2% up to about 10%.

9.2 - Plate is a flat rolled metal product of some arbitrary dimensions, thickness above 6 and up to 300 mm (0.25 and 12 in.), and width from 200 to 2000 mm (8 to 80 in.), used as semifinished material for fabricating metallic structures.

9.3 - Roll Forging is a continuous process of shaping stock in preforms or finished parts, by passing a heated bar between a set of rolls, rotating in opposite direction, having one or more matching sets of grooves or forming cavities on their rim.

9.4 - Shrinkage Cracks form in molten metal as a result of pulling apart of grains by contraction stresses before complete solidification.

9.5 - Thermal Inspection is a nondestructive test method in which heat-sensors measure temperature variations in components, structures, systems, or physical processes. Can be useful in the detection of subsurface flaws or voids, if the flaw depth is not large compared to its diameter.

9.6 - Ultrasonic Beam is a coherent sound burst of acoustic energy at a frequency higher than the range of audible sounds, above about 20 kHz.

10 - Explorations: beyond the Welder

NASAs First Orion Capsule Ships for Crucial Deep Space Tests
NASA.

Twisted Light Could Enable Black Hole Detection
SA1.

Spacecraft Riding the Solar Wind
SA2.

Global solar observatory flares into life
SA3.

Spray-on Solar Panels
NSF.

11 - Contributions: Advances in Thermal Spray

If you think that Thermal Spray is by now a well mature technology, unlikely to reserve surprises for those having some familiarity with its applications, you might possibly reconsider your opinion.

In fact, being driven by important interests in many of the big industries, it is continuously evolving, producing new materials, new techniques and new applications.

A limited glimpse of what is happening can be caught by reviewing the publications devoted to these subjects. One in particular, the last issue 1, Volume 6, for February 2011 of the International Thermal Spray & Surface Engineering, the official Newsletter of the ASM Thermal Spray Society, provides an interesting Overview of recent advances.

This newsletter is published quarterly by ASM International and is included as a part of Advanced Materials & Processes, the monthly ASM Magazine.

The Development of Nano-Structured Coatings for Enhanced Corrosion Performance is the first article of this publication. It reports on the "superior resistance of metallic glasses and/or nanocrystalline materials to electrochemical attack, due to the difficulty of the system to set up specific anodic and cathodic sites, as the microstructural scale is reduced". It is explained that, while thermal spray can only produce microscale sized of individual splats due to rapid solidification, nanoscale deposits can only be achieved by processing glass forming compositions, resisting nucleation and growth.

Specific alloy compositions can be designed having critical cooling rates lower than that of application processes. Special NanoSteel alloy called SAM2X5 permits to achieve amorphous, glassy structure in HVOF (High Velocity Oxygen Fuel) spray coatings.

Another alloy, called SHS8000, deposited by arc-spray, could achieve high corrosion and erosion resistance in boiler application. As deposited the coating layer if fully amorphous, except that it will divitrify (recrystallize) completely in time, at high temperature.

Further developments along these lines might bring in future, economic and durable corrosion resistant coatings for demanding applications.

Materials Testing for use in Strong H₂S Acidizing Environments is another article in the publication, describing laboratory work to evaluate the corrosion resistance of various alloys under acidizing conditions.

To conduct the testing, a special autoclave was built, with all exposed surfaces of either solid tantalum or of tantalum covered stainless. The tantalum surfacing alloy proprietary process used, involves the production of a gaseous atmosphere of tantalum that grows the metal onto and into the substrate.

On the substrate of 316L stainless, an interface called Tantaline^TM Surface Alloy is grown, onto which Tantalum metal forms, providing the chemical and corrosion resistance properties of pure Ta. This process occurs at nanoscale dimensions and at high temperatures creating a metallurgically bonded layer superior in durability to traditional coatings or electroplating.

The tests showed that at high temperature and pressure in Strong H₂S Acidizing Environments, only tantalum resists corrosion, its usage being restricted by high cost, unless effective tantalum surfacing techniques, like the one demonstrated in the study, can be applied.

Another article introduces a new Corrosion Resistant, Non-slip Thermal Spray Coating for Harsh Industrial Environments. This Thermal Spray coating can be applied with a rough texture having excellent non-slip properties, and is extremely hard and resistant to wear. The new proprietary coating provides:

• A suitable level of grip, to avoid personal slips or industrial skidding
• Comparable corrosion protection to that of aluminum used in aggressive environments
• Easy application by a well known process.

The coatings were tested for non-slip and durability using a pendulum coefficient of friction tester, in accordance with independent British Standards and UK Health and Safety Executive (HSE) guidelines.

Finally the publication reports the summary of two articles from the Journal of Thermal Spray Technology dealing with cold spray coatings, one on copper on aluminum nitride substrate, the other on mechanical properties of titanium splats deposited at increasing velocities.

Interested readers are urged to seek the referred publication.

12 - Testimonials

From: Leon Scoggins
To: Welding Advisers
Date: 01 Feb 2011, 10:49:17 AM

The reason I unsubscribed was I had 2 e-mail addresses and now I have only one. I enjoy your website VERY MUCH and look forward to receiving it. Your welding tips and information has been a big help to me. Please keep up the good work.

Thanks

Leon Scoggins

From: Mac
Date: 16 Feb 2011, 07:21:01 AM
Subject: PRACTICAL WELDING LETTER Unsubscribed
Hi Elia,
it is very interesting, but just a matter of information overflow/not enough time to read.
I've kept your website name, for future reference.

Kind regards,
Mac

13 - Correspondence: a few Comments

13.1 - Normally the mail I receive contains questions. What should I understand from a message containing only a number, possibly a phone number but without the Country Code?

13.2 - A correspondent from the US was displeased with a short caption in the title of one of my website pages. Therefore, as a feedback he wrote two question marks (??). No comment.

13.3 - A correspondent, supplier of consumables, asked for the reasons for porosity, found by RT in welds of one of his customers. He gave the parameters (Current Voltage and Travel speed) for Root pass, Hot Pass, Fill up and Capping, but still had no clue of what caused unacceptable porosity.

This prompted me to write a website page on Weld Porosity, as reported in section 8 above.

14 - Bulletin Board

14.1 - Lincoln Electric Automation will host a one day laser welding and cutting technology seminar
at the Automation Center of Excellence on March 24, 2011.
The seminar will include a brief review of the history of lasers, an introduction to laser materials processing benefits and hands-on demonstrations of the technology.

Lincoln Electric.

14.2 - An International Conference Showcasing the End User Laser Applications
April 13 & 14, 2011 - Hilton Hotel, Hartford, Connecticut
http://clientportal.ccat.us/sala2011

14.3 - The SBI! Small Business Locator and Idea Finder
http://find.sitesell.com/Quark.html

14.4 - Case Studies
http://case-studies.sitesell.com/Quark.html

BUILT BY:

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Please continue to browse down hereafter for the Mid March Bulletin.

Copyright (©) 2011, by Elia E. Levi and
www.welding-advisers.com
All Rights Reserved

Bulletin 59 - PWL#091B
March 2011

Keywords: Metallography, Quantitative Metallography, Digital Image Analysis, Microstructure, Photomicrography,

Bulletin 59 PWL#091B - Resources on Metallography and Quantitative Metallography, Digital Image Analysis, Microstructure, Photomicrography, Frequently Asked Questions, Standards, References, Color Metallography, grain size determination, grain distribution, boundary definition, surface roughness, depth of decarburization or carburization, layers, diffusion, corrosion, intercept count, cleanliness, banding, hardness testing, second phase distribution, weld penetration and much more...

Mid March Bulletin

Introduction

This Mid March Bulletin # 59 is now integral with and appended to the regular PWL#091 publication.

The subject of this Bulletin is a collection of Online Resources on Metallography and Quantitative Metallography published as additional information to the Article published in Section 7 above.

We add also the reference to some of the suppliers of materials, equipment and services, not intending any recommendations but rather as a source of further knowledge that may be useful to solve practical problems.

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)
You may also click periodically on the Welding Blog button in the NavBar.

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

Image analysis
http://en.wikipedia.org/wiki/Image_analysis

Metallography
http://en.wikipedia.org/wiki/Metallography

Microstructure
http://en.wikipedia.org/wiki/Microstructure

Metallography Explained
http://everything.explained.at/metallography/

Disclaimer: Some of the following Sources are Commercial Companies involved in the production of equipment for Metallography. No endorsement or recommendations are intended in the links below. However the discerning reader can read informative articles likely to enrich his/her experience and knowledge, independent of the equipment used or advertised.

LECO - Application Notes - Metallography Resources
LECO.

Olympus - Extensions for digital metallography
http://www.lri.se/pdf/olympus/Stream_Extensions.pdf

Digital Materials Analysis
http://www.microscopy.olympus.eu/microscopes/images/MS_DM_1.pdf

Monitoring Superconductors Via Digital Image Analysis
Olympus.

Microscopy Resource Center - Site Navigation [Explore in Depth] http://www.olympusmicro.com/index.html

Microscopy Resource Center - Photomicrography
http://www.olympusmicro.com/primer/photomicrography/index.html

Buehler - Frequently Asked Questions
http://www.metallography.com/experts/faq.html

Buehler - References
Buehler1.

Introduction to Quantitative Metallography (6 pages)
Buehler2.

Color Metallography (4 pages)
Buehler3.

ASTM Metallography Standards and other Standards (5 pages)
Buehler4.

Struers - Application Notes (13 Dowloadable PDFs)
Struers1.

Struers - Literature about Metallography
Struers2.

Metallography Downloads
http://www.pdfqueen.com/metallography

Digital Image Analysis of Materials
http://www.pgt.com/Library/Papers/Digital_Image.pdf

Metallography
http://www.uom.ac.mu/faculties/foe/mped/Students_Corner/Practical.pdf

Quantitative Metallography Technical Publications
Hoeganes.

Quantitative Metallography of Titanium Alloys
Clemex.

Image Analyzers (For Quantitative Metallography)
AM&P Directory.

Metallographic Study
http://www.mee-inc.com/metal.html

Books for sale

ASM Handbook Volume 9: Metallography and Microstructures
ASM International / 01-Jan-2004 / 1184 pages
Click to Order.

ASTM - STP839
Practical Applications of Quantitative Metallography

ASTM / Manuals, Monographs and Data Series / MNL46-EB / MNL11197M
Quantitative Metallography/Materialography - An Introduction
http://www.astm.org/DIGITAL_LIBRARY/MNL/PAGES/MNL11197M.htm

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