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PWL#080 - Improving Productivity, Hardfacing Nanotechnology, Welding Chrome-Moly Tubing
April 01, 2010
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PWL#080 - Improving Productivity, Welding Copper to Stainless, Nanotechnology for Hardfacing, Welding Chrome-Moly Tubing, Acoustic Micro Imaging, Welding Metallurgy, Residual Stresses and more...

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April 2010 - Practical Welding Letter - Issue No. 80


TABLE of CONTENTS

1 - Introduction

2 - Article - Five Goals for Improving Productivity

3 - How to do it well: Welding Copper to Stainless (C)

4 - Filler Metal: Nanotechnology based Material for Hardfacing

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article - Welding Chrome-Moly Tubing

8 - Site Updating: Welding Metallurgy, Residual Stresses

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Acoustic Micro Imaging

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board


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1 - Introduction

How fast is time running! It seems I just started publishing my Practical Welding Letter and here we are already at Issue No. 80, opening with a reminder of only five goals that could improve the productivity of any welding shop.

It should be quite easy to concentrate the attention on simple tasks. It appears that overlooking the sources of useless waste is quite common everywhere, so that just by taking the initiative and implementing the rules, a welcome improvement of the bottom line is assured. Why should anyone make mighty efforts to gain an extra job, and then neglect to improve the yield of current work?

The recent review of an intriguing article on a costly failure made me aware of the fact that certain recommendations I published relative to the welding of copper to stainless steel might be incorrect or at least incomplete. I asked therefore the opinion of an expert and now I report the warning, to make sure that readers will thoroughly investigate the problem before making questionable decisions.

In the Filler Metal section, a press release is reported without intention to advertise or endorse the products presented. If confirmed, the use of nano structured materials may offer economic solutions to hardfacing applications.

Best practices are probably highly sought useful information especially for popular materials. A recent article is summarized, explaining the correct procedures for welding successfully light and strong 4130 tubing structures.

Acoustic Micro Imaging is a useful nondestructive method that can be used for inspection of metallic and composite materials for detecting defects.

The new website pages deal with Welding Metallurgy and Residual Stresses, basic subjects for solving welding problems and tough applications.

The rest of regular sections can be found at the usual place. The amount of 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 - Five Goals for Improving Productivity

Every welding shop can improve remarkably its productivity simply by concentrating on five goals that, in the normal course of work, risk of being overlooked.

  1. Reducing Weld Metal Volume to fulfill drawing requirements but no more than needed to meet the design intent. Excess weld material is a costly waste. Overwelding does not contribute to stronger or safer weldments: it is a discrepancy that should be contrasted with proper education and discipline.

  2. Reducing Arc Time per weldment means improving the Weld Deposition Rate (WDR) to achieve the required coverage in the minimum possible time. This requires measuring and knowing the actual WDR applied by the current method and parameters. Obviously striving to reach this goal may mean trying different processes and procedures. Given the remarkable rewards that can be gained by reducing arc time to the minimum, it is a well spent effort. The introduction of suitable bonus incentives may contribute to make the bookkeeping more acceptable to the welders.

  3. The third recommendation deals with setting in place a system aimed at reducing waste connected with non conformances, repair work and scrapping unacceptable and irreparable welded items. In order to account for every instance of such cases one has to report them, to investigate their causes and to implement corrective actions designed to avoid their recurrence. Essential elements toward this goal are proper education, training and supervising to monitor the performance.

  4. Much thought should be devoted to employ means and methods capable of Reducing Work Effort on the part of the welder. By studying the actual work being done and by engaging the welders' cooperation one can implement the availability of tools and accessories likely to improve their productivity by reducing their physical effort.

  5. Reducing Motion and Delay helps maximize the useful arc-on time. This means setting up a system for supplying continuously new work to the welders, freeing them from the need to perform unproductive auxiliary actions. This may require reorganizing the layout of the work area and the work flow.

These productivity improvements cannot be implemented unless Management takes a firm stand introducing an integrated approach involving all functions, including, design, purchasing, stores, planning, production and quality assurance. Motivating all involved and measuring all relevant data in view of striving to reach the above goals will help building the base for improving profitability.

These recommendations can be found in a study at
http://files.aws.org/research/weld_sup_trng.pdf


3 - How to do it well: Welding Copper to Stainless (C).

A note in my page on Weld FAQ, based on an article of the ASM Handbook Vol.6 at page 769, gives some indications on the feasibility of the process using suitable filler metals like ERCuAl-A2, ERCu or ERCu-Ni3.

Following the publication of my last PWL#079 (in section 4), of a summary of a Welding Journal article from Feb 2010, pg. 46, that attributes a failure of stainless tubing to Copper Contamination Cracking, I had to reconsider the recommendation and I asked the opinion of Professor Yoni Adonyi (who published articles in the two past issues of this publication).

His answer follows here:
"Copper Contamination Cracking is indeed a serious problem when FUSION welding Stainless Steel on Copper backing bars or similar copper contamination from fixtures that can contaminate the weld. It can also be encountered in overheated spot or seam resistance welds on the SST sheet outside surfaces where localized Cu liquation causes grain boundary penetration and cracking.

However, when using solid state welding such as Friction Welding you mentioned, all liquated material is ejected and should not cause cracking. My immediate reaction to such a question would be using brazing combined with a mechanical interlocking."

Therefore in my page on Weld FAQ, I added a short note (C) (to the question of Welding Copper to Stainless), to the effect that every such application should be tested by performing preliminary trials to avoid the conditions leading to CCC.


4 - Filler Metal: Nanotechnology based Material for Hardfacing

Note: - Although the following press release is based on a commercial publication, it may have informational value of interest to our readers. No endorsement or recommendation are implied in the following. Readers interested in the claimed properties are urged to seek independent confirmation and to verify by testing eventual suitability of the proposed materials to their applications.


Press Release: NanoSteel Launches Weld Overlay Stick Electrode Product Line

PROVIDENCE, R.I. (Thursday, March 4, 2010) - The NanoSteel® Company, a leader in nanostructured steel alloy surface technologies, announces the release of the company’s first stick electrode, SHS 9700E, for weld overlay hardfacing applications.

SHS 9700E, the newest addition to NanoSteel’s patented portfolio of Super Hard Steel® (SHS) alloys, is a premium alloy that features an ultra refined, near nanoscale crystalline microstructure which results in very high hardness, up to 70 HRc, and exceptional resistance to abrasive wear.

The NanoSteel Company, Inc., headquartered in Providence, R.I., designs and sells a patented portfolio of Super Hard Steel iron-based nanostructured alloys applied as thermal spray coatings and weld overlay for hardfacing and wear plate. NanoSteel alloys effectively solve or alleviate many operational challenges faced in critical industries today, including corrosion, erosion and wear in a wide range of complex service environments. NanoSteel coating and overlay solutions are for use in the power generation, mining, concrete/cement and oil/gas industries. For additional information, call toll free 1-877-293-NANO begin_of_the_skype_highlighting              1-877-293-NANO      end_of_the_skype_highlighting or visit www.nanosteelco.com.


5 - Online Press: recent Welding related Articles and Video

Welding Aluminum
http://www.thefabricator.com/article/aluminumwelding/welding-aluminum

Beyond low-carbon steel
http://www.thefabricator.com/article/arcwelding/beyond-low-carbon-steel

Welding costs - continued
http://www.twi.co.uk/content/jk97.html

Submerged arc welding consumables
http://www.twi.co.uk/content/jk87.html

Fronius: Virtual Welding Englisch/English (video)
http://www.youtube.com/watch?v=jbk2Z2KQZ64


6 - Terms and Definitions Reminder

Arc Voltage Control is achieved by a system that calculates the arc length by measuring the arc voltage and then adjusts the arc length to the selected value by an automatic manipulator.

Cost Estimate is a forecast of expenses incurred in the manufacture of products, that helps to define the most economic way to implement the different operations.

Delaminations are discontinuities in the base metal brought about upon weak laminations (a type of discontinuity with separation or weakness generally aligned parallel to the worked surface of a metal) by transverse stresses generated by welding processes.

Free Machining refers to the machining characteristics of an alloy to which one or more ingredients have been introduced to produce small broken chips, lower power consumption, better surface finish, and longer tool life. Among such additions are sulfur or lead to steel, lead to brass, lead and bismuth to aluminum, and sulfur or selenium to stainless steel. All these additions are detrimental to welding.

Groove Face is any surface of a weld groove as appearing before welding.

Hot Tear is a fracture formed in a metal during solidification because of hindered contraction. Also a crack forming in metal as a result of the pulling apart of grains by contraction before solidification is completed.

Longitudinal Shrinkage in steel weldments is estimated as being about one thousandth of the weld length. Formulas are available for calculation.

Transverse Shrinkage is generally much larger than the longitudinal one above. However it is complicated by angular or rotational distortion and non uniform joint restraint.


7 - Article - Welding Chrome-Moly Tubing

A very popular material for building light and strong structures, 4130 is a high strength low alloy (HSLA) steel containing about 1% Chromium and 0.2% Molybdenum, at a nominal Carbon content of 0.30%. This particular composition makes it suitable to develop good mechanical properties that made it the preferred selection for critical applications like engine mounts in old aircraft.

These days the same material is employed successfully for racing cars, motor sport and aerospace applications. The current issue of the Welding Journal for April 2010 summarizes the best practices for welding strong and light weight normalized tubing of 4130.

Manufacturing items with such tubes of limited thickness, up to 0.125" (3.18 mm) by GTA Welding (also known as Tig), provides elevated strength to weight ratio permitting economical use of material.

Perfect fit-up, controlled with tolerance gages, is a common requirement for high quality weldments. Then deburring and thorough cleaning must be performed before welding. The article recommends the use of filler metals capable to provide better ductility than 4130 filler metal. ER 70S-2 is preferred or, for higher strength, ER 80S-D2.

It is suggested to keep a short arc length of 0.125" (3.18 mm) or less to avoid excess heating. The Table published in the original article specifies the correct parameters that guarantee perfect performance and reliability.

Welders who use to weld Crome-Moly tubing are urged to review the recommendations in the article mentioned above.


8 - Site Updating: Welding Metallurgy, Residual Stress

Here are the Pages of this Month. The first page briefly describes what is Welding Metallurgy and what is it good for. It is the scientific base for every weld, and the first resort to any welding problem. It is certainly a benefit to be able to tap these resources.

The page can be read by clicking on Welding Metallurgy.

The second page reviews formation and importance of Residual Stresses, usually generated by welding processes. The methods used to analyze them are briefly reviewed, although generally performed by specialized technicians or investigators. Once available the information is readily interpretable by anyone interested in the results of his/her welding operations.

To find the page click on Residual Stress.

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 - Pin Expansion Test checks the ability of a tube to be expanded or reveals the presence of cracks or other longitudinal weaknesses. It is made by forcing a tapered pin into the open end of the tube.

9.2 - Stretch Forming shapes a metal sheet or part, usually of uniform cross section, by first applying suitable tension or stretch and then wrapping it around a die of the desired shape.

9.3 - Transformation Ranges in steels are ranges of temperature within which austenite forms during heating and transforms during cooling. They are distinct for heating and cooling. Limiting temperatures depend on steel composition and on the rate of temperature change, particularly during cooling.

9.4 - Triple Point is either a point on a phase diagram where three phases of a substance coexist in equilibrium. or the intersection of the boundaries of three adjoining grains, as observed in a metallographic section.

9.5 - Ultrahard Tool Materials are polycrystalline diamond and polycrystalline cubic boron nitride, very hard wear-resistant materials, fabricated into solid or layered cutting tool blanks for machining applications.

9.6 - Wax Pattern is a precise duplicate, allowing for shrinkage, of the casting and required gates, usually formed by pouring or injecting molten wax into a die or mold. These or plastic patterns are used for investment casting.


10 - Explorations: beyond the Welder

Tracking Trash to Turn Waste into Efficiency
http://www.scientificamerican.com/article.cfm?id=turning-waste-into-efficiency

Climate Change Imperils the State of the Planet
http://www.scientificamerican.com/article.cfm?id=climate-change-imperils-state-of-the-planet

The Sheer Delight of Tackling Shear Stress
http://www.nasa.gov/topics/aeronautics/features/shear_stress.html

NASA Ames Researcher Revolutionizes Air Traffic Management
http://www.nasa.gov/topics/people/features/heinz_erzberger.html

Fossil finger points to new human species
http://www.nature.com/news/2010/100324/full/464472a.html


11 - Contributions: Acoustic Micro Imaging

In the March 2010 issue of Advanced Materials and Processes, a periodic publication of ASM International, an article on Acoustic Micro Imaging is published at page 28, outlining the uses of this recent nondestructive testing method to detect and analyze dangerous defects in devices for medical applications.

In one reported example, the ultrasound beam that is pulsed into a manufactured item, in this case an x-ray target made of tungsten, bonded to a copper substrate designed to remove excess heat, is partially reflected by the top surface of the tungsten.

Part of the scanning beam, transmitted through the surface, continues to the tungsten copper interface. There, if the bond is good, a reflected beam of moderate intensity is reflected back and analyzed. But if the bond is defective, the air interface will reflect most of the incoming beam signaling the defective condition, that is promptly recorded in an image. This is made up with false color for better discrimination of the defective (unbonded) areas.

Another example illustrates the research of defects in an item designed for automated blood analysis. It is made of a plastic body where channels are carved, covered with a thin film foil bonded to the surface of the body. Acoustic imaging of this item permits visual inspection to detect open passages in the channel and correct bonding of the foil.

The versatility and simplicity of this nondestructive method should be kept present and investigated as it might provide the perfect solution for tough inspections. Interested readers are urged to seek the original article reported above.


12 - Testimonials

On Mon Mar 01 16:47:34 2010, the following results were submitted from the "Form 5" on welding-advisers.com:

Name: Charlie Guthrie
E-mail Address: removed for security
Country: United States

[...]
Thanks for all of your efforts with this fine news letter, and keep the information coming.
[...]
Once again, I appreciate your efforts with the welding news letter. It has helped me gain a fuller understanding of the many facets of an underappreciated process. So much to learn, so little time.

Best regards,

Charlie Guthrie


On Fri Mar 05 04:05:52 2010, the following results were submitted from the "Form 5" on welding-advisers.com:

Name: Julia Zhu
E-mail Address: removed for security
Country: China
[...]
Hi Elia,
Thanks for your reply.
Wish you good luck.
Best Regards,
Julia


13 - Correspondence: a few Comments

13.1 - Following the recent publication of the Mid March Bulletin 47 on Welding Calculations and Calculators, a kind reader, Jim Galloway, Welding Instructor at the Conestoga College, sent me the following links, developed through the Canadian Welding Association, for the benefit of our readers:

For equipment justifications (ROI)...
http://www.cwa-acs.org/members/journal/CWA_Winter2008GallowayFinCalc.xls

For welding cost analysis...
http://www.cwa-acs.org/members/journal/CWA_Winter2008GallowayCostCalc.xls

For arc welding energy costs...
http://www.cwa-acs.org/members/journal/Energy-ROI.xls

I am adding these links to the above Bulletin, available by clicking on
PWL#079B.

13.2 - I received a letter written in Polish(!), by someone looking for work...
Sorry, I cannot help.

13.3 - The owner of a steel fabrication and welding company writes me:
"need to get welders certified closest to 3824 river road live oak fl. 32060.u.s.a"
If any of the readers is interested, I can give the contact.


14 - Bulletin Board

14.1 - International Thermal Spray Conference and Expo
ITSC 2010 Singapore • May 3-5, 2010
Fairmont Singapore
Raffles City Convention Centre
http://asmcommunity.asminternational.org/content/Events/ITSC/

14.2 - Shape Memory and Superelastic Technologies (SMST)
Asilomar Conference Center - Pacific Grove California
May 16-20, 2010
http://asmcommunity.asminternational.org/content/Events/smst10/default.jsp

14.3 - International Symposium on Surface Hardening of Corrosion Resistant Alloys
May 24-26, 2010
Case Western Reserve University
Cleveland, Ohio


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