PWL#070 - Seismic Welding Procedures and Filler Metals, Mig or Stick?, Centrifugal Casting, Forge Welding, Brazing Beryllium, Qualification of 2.25Cr-1Mo Filler Metal and more...

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1 - Introduction

2 - Article - Seismic Welding Procedures

3 - How to do it well: Mig or Stick?

4 - Filler Metals for Seismic Resistant Structures

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article - Centrifugal Casting

8 - Site Updating: Forge Welding, Brazing Beryllium

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Issues with 2.25Cr-1Mo Filler Metals

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board

1 - Introduction

This 70th Issue of Practical Welding Letter opens with the big problem of Structural Engineers: How to build Safe Structures in Geographic Areas prone to Seismic Events.

The subject has much significance also for Welding Engineers who should study the concerns relative to design, construction, inspection and performance of welds, in order to be able to advise and support the designers.

Fortunately in the last decade much work was done in fundamental research and in publishing information and standards. The brief note indicates a few of the sources that can be consulted to learn the basics.

Also filler metals for seismic resistant constructions must be selected and qualified according to the principles regulating the matter. The note in section 4 addresses the relevant concerns.

In section 3, answering a specific question, I point to a recurring problem: the bad habit of (the missing) management to leave on the shoulders of skilled welders responsibilities that should not concern them, like the selection of the welding process for a given production.

Welders may be proud of the confidence granted to them, but they should be aware that it is a murky and unfair situation. In case of failure they may be left alone and unsupported to face charges that pertain to management.

Next article in section 7 presents a few facts about centrifugal casting, that takes a big share of all castings and has peculiar qualities and advantages.

The pages of this Month, added to the website, are about Forge Welding, a traditional method applied since very old times, and about Brazing Beryllium, an important joining process for this light and special material finding use in nuclear and aerospace applications.

Finally there is a case history report of the practical way conducted to perform the selection of a specific filler metal out of three, nominally with the same designation, for meeting the requirements of an important repair job.

Other regular departments can be found at their usual place. If you want to send us your Contributions from your own experience you are welcome. Enjoy your reading.

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2 - Article - Seismic Welding Procedures

In the aftermath of the 1994 earthquake in the Los Angeles area, known as the Northridge, California event, that caused wide damage in welded steel frame buildings, investigation efforts were initiated by the Federal Emergency Management Agency (FEMA) with the purpose to assess the damages, to determine their causes and to define improved rules capable of limiting their renewed occurrence in the future.

As a consequence of this extended work, several new documents were published that pointed to the weak points in previous design and realizations, and addressed the subject of improved practices to be employed in future to contain damages.

In 2001 FEMA published design guidelines applicable to moment frame buildings in the US in the form of recommendations FEMA 350, 351, 352 and 353, and identified the need to update existing building Standards.

Independent institutions, AWS (American Welding Society) and AISC (American Institute of Steel Construction), accepted to follow through, and agreed by concerted action to translate the recommendation into binding codes.

AISC took charge of issues of "what" and "where", culminating in the publication of
AISC 343, Seismic Provisions for Steel Buildings, and additional documents
while AWS addressed those of "how" and "who" by issuing its
AWS D1.8 - Seismic Supplement to the D1.1 Structural Welding Code - Steel.

The Lincoln Electric Company (www.lincolnelectric.com), was involved with both institutions through its Manager of Engineering Services Duane K. Miller, Sc.D, P.E., who chaired the AWS D1.8 Committee and the AISC Seismic Provisions Committee.

As a service to their customers, the Company published the following:

D1.8 Seismic Supplement Welding Manual (48 pages)
A General Overview of AWS D1.8 Structural Welding Code
http://content.lincolnelectric.com/pdfs/products/literature/D1.8_Supplement.pdf

and also

FEMA 353 - Welding Manual (36 pages) http://content.lincolnelectric.com/pdfs/products/literature/c160.pdf

The purpose it to assist whoever needs to understand the AWS D1.8 seismic welding guidelines and to comply with its requirements. Additionally it is also meant to introduce Lincoln consumables designed and tested to meet those requirements.

See also the following publications:

A Policy Guide to Steel Moment-Frame Construction (31 pages) http://www.nehrp.nist.gov/pdf/fema354.pdf

Order for Earthquake Resistance in the Court http://www.thefabricator.com/Consumables/Consumables_Article.cfm?ID=860

Additional information from the International Institute of Welding can be seen at
Welding Provisions for Seismically Loaded Structures in the USA
http://www.iiw-iis.org/iiw/extranet/static/MS/C-XV/XV-1203-05.pdf

Download AISC Specifications and Codes from:
http://www.aisc.org/content.aspx?id=2884

All the above is instructive documentation that we recommend to all our readers, even if not actively engaged in welding steel frame buildings.

3 - How to do it well: Mig or Stick?

Q - I am a welder that welds with a lot of different processes.
My question is this. We are welding up a fabrication table to build a container box that will weigh 50,000 lbs.

I was told that it should be SMAW welded with E-7018 and not to weld it with Mig. The mig wire we use is ER-70.
What is the difference in the two processes?
Aren't both electrodes classified as being good for 70,000 psi?
Should I make this structural weld with the Mig or Stick?

A - Thank you for your question.

I feel from it that you are a good, experienced and conscientious welder.
I am sure you will obtain good welds with both processes.
Keep up the good work as you please and it will be OK.
[It is true that inadequately skilled welders may produce low quality welds with any process.]

One of the disadvantages attributed to Mig (GMAW) when performed outdoors is the possible loss of shielding gas due to the wind: this is perhaps the concern of those who "told" you to avoid Mig.
It depends upon the circumstances, if effective wind shields can or cannot be set up.

It is accepted that self shielded Flux Cored Arc Welding (FCAW) is less prone to the loss of shielding atmosphere while providing the continuous electrode advantage as Mig does. However breathing FCAW fumes is more dangerous to the welder's health.

As far as strength and stability are concerned the design has to be adequate but there are no differences between the two processes that should bother you as long as sound welds are produced.

There may be quite a remarkable difference in the cost of welding though, but this is up to the management to decide and be responsible for.

What bothers me is that you are made to work in a vacuum of responsibility.

About a year ago I wrote an article titled
"Where is the Welding Management?" that you can find at
http://www.thefabricator.com/CEOs/CEOs_Article.cfm?ID=1939

As long as your work is good, you will grudgingly get moderate praise
(Not too much, lest you may think you are worth a pay raise).
But should one of your construction collapse or get damaged you will get all of the blame and of the consequences.

If at all possible, you should request from your management precise, written instructions in the form of clear, signed Drawings and Welding Procedure Specifications (WPS).

You are not supposed to be "told" anything, you should get only written instructions. Those who give you welding work must take full responsibility in writing for whatever you are requested to perform at the best of your ability, but not any more than that, including process selection.

4 - Filler Metals for Seismic Resistant Structures

Following up on the subject of the article published above in Section 2,
I would like to recommend that readers take up the General Overview document indicated there, and see at pages 18 and following the discussion relative to requirements of AWS D1.8.

Note: - Although the information is provided by a commercial company, the discussion is conducted there in general terms. No endorsement of particular products is intended within this article.

The quoted Manual explains the requirements of the said Supplement for Filler Metals used for work done under AWS D1.8, in particular minimum CVN requirements and maximum diffusible hydrogen content.

Special test requirements applicable to Demand Critical Welds are explained.

FCAW electrodes having the new supplemental designator "-D" as defined in AWS A5.20:2005 are required to be tested at a prescribed high and low heat input level as well as tested according to standard A5 classification test. This is an optional approach to determine the suitability of the filler metal to AWS D1.8 requirements. (pages 19-20)

Welding Inspectors have definite responsibilities regarding Filler Metals, see there at page 23.

In page 24 and following the Company promotes their own consumables. Even those willing to consider alternative suppliers could profit from the discussion presented and from the examples of Certificates of specific products.

From the same Company additional information can be obtained at
http://www.lincolnelectric.com/D1.8.asp

In particular a Welding Guide can be downloaded, which is tailored to the Company's consumables, but its general recommendations are appropriate for suitable products from any supplier.

See also:
Learning How to Purchase Consumables and Weld Under FEMA 353 Guidelines for Steel Moment-Frame Construction Seismic Applications
http://www.lincolnelectric.com/knowledge/articles/content/fema.asp

From other suppliers see:

Fabshield XLR-8 - Datasheet http://www.hobartbrothers.com/pdf/datasheets/FabshieldXLR-8.pdf

and

Seismic Certifications from ESAB
http://www.esabna.com/us/en/support/seismic-certifications.cfm

5 - Online Press: recent Welding related Articles

Sizing up seismic-friendly Filler Metals
http://www.thefabricator.com/Consumables/Consumables_Article.cfm?ID=2143

Laser Technology Focus - ALAW 2009
http://www.thefabricator-digital.com/thefabricator/ALAW2009/

Connect - Issue 160 May/June 2009 - The magazine of TWI
http://www.twi.co.uk/content/conmay09.pdf

A Primer on Infrared Thermography
http://files.aws.org/itrends/2009/04/it200904/it0409-16.pdf

Welding Inspection and Quality Control (14 Lessons Series)
from www.asminternational.org
Home > Education & Training > Self-Study Courses > Welding

6 - Terms and Definitions Reminder

Adhesive Bonding is a materials joining process in which an adhesive placed between faying surfaces of different materials solidifies developing attractive forces characteristic of this kind of polymeric materials.

Bonding Force is that which holds two atoms together, resulting from a decrease in energy as two atoms are brought closer to one another.

Elongated Porosity is a form of cavity discontinuity whose length is greater than its width and whose long axis is approximately parallel to the weld axis.

Gas Metal Arc Welding (GMAW) (also knows as Mig - Metal Inert Gas) is a welding process where an electric arc is struck between the tip of a continuous wire electrode (being fed into the welding joint) and the work, under the cover of an externally supplied shielding gas.

Open Circuit Voltage is measured between the output terminals of the power source when no current is flowing through them.

Plasma Arc Welding uses a constricted arc between a nonconsumable electrode and the weld pool (transferred arc) or between the electrode and the constricting nozzle (nontransferred arc). Shielding is provided by the ionized gas from the torch supplemented by an additional source of shielding gas.

Resistance Welding Electrode, is the element of the resistance welding machine through which welding current and compressive force are applied to the workpiece.

Test Coupon is an assembly, welded brazed or soldered, intended to be tested as required for procedure or performance qualification.

7 - Article - Centrifugal Casting

Centrifugal Casting is a method of shaping hollow items by casting molten metal into a rotating mold. All castable metals can be used this way, but also non metals, like ceramics, glasses, plastics and any other material that can be made as liquid or pourable slurry. A derivation of this process is used for the production of ceramic lined steel pipes.

For special applications like the production of jewelry, the centrifugal force is used to fill a mold, not necessarily for producing hollow castings.

The process is economical for mass production with regard to casting yield, cleaning and mold cost. Therefore it is estimated that about 15% of the casting output by weight are produced using the centrifugal force.

Although the process needs to use special machinery to rotate the molds, the elimination or minimization of gates and risers makes molds simpler and more economic.

The high pressure developing in the molten metal contributes to its feeding with better separation from nonmetallic inclusions and evolved gases. These tend to concentrate toward the inner surface of the hollow casting wherefrom they can be easily removed.

Therefore castings of high quality and integrity due to their high density can be produced even for thinner sections, relative to gravity processes. Centrifugal casting produces finer grains that improve mechanical properties and provide good weldability.

Casting machines can have their spinning axis horizontal, vertical or inclined. Horizontal axis machines are used for simple shape long items, relative to their hollow diameter. Vertical machines are suitable for shorter bodies, even for conical sections, and for non symmetrical or non cylindrical castings.

Centrifugal casting of parts difficult to produce by gravity feeding improves mold cavity filling, improves yield and eliminates voids and porosity.

Centrifugal methods for mold or die casting, and sometimes even for investment casting, use the centrifugal force to fill molds arranged around the center axis of rotation of a feeding system.

8 - Site Updating: Forge Welding, Brazing Beryllium

The Pages of this Month added to our Website refer to two processes, the first of which has mostly historic interest. It is about Forge Welding, the ancient method used for centuries by blacksmiths, until the development of new and practical processes.

The page can be found at Forge Welding.

The second page, on Brazing Beryllium provides basic information on the method that is the most used for joining this special metal, because of its advantages relative to other processes which are less successful and more problematic.

Check for new pages in the 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 may need, 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.

9 - Short Items

Constraint is any restriction that limits the transversal contraction normally associated with a longitudinal extension. Constraint hence causes a secondary tension in the transverse direction: usually described in connection with welding.

Lapping is a finishing operation performed lightly on the whole surface using fine abrasive grits loaded into a lapping material such as cast iron. Lapping provides major refinements in the workpiece including extreme accuracy of dimension, correction of minor imperfections of shape, refinement of surface finish, and close fit between mating surfaces.

Restraint is any external mechanical force that prevents a part from moving to accommodate changes in dimension due to thermal expansion or contraction. Often applied to weldments made while clamped in a fixture. Restraint may limit deformation by locking residual stresses in the weldment.

Spheroidizing includes various techniques of heating and cooling to produce a modified microstructure consisting of spheroidal or globular form of carbide in steel.

Stiffness is an expression of the rate of stress with respect to strain; the greater the stress required to produce a given strain, the stiffer the material is said to be. It is also the ability of a material or shape to resist elastic deflection. For identical shapes, the stiffness is proportional to the modulus of elasticity. For a given material, the stiffness increases with increasing moment of inertia, which is computed from cross-sectional dimensions.

Toughness is the ability of a material to absorb energy and deform plastically before fracturing. Toughness is proportional to the area under the stress-strain curve (obtained from a standard tensile test) from the origin to the breaking point. In metals, toughness is usually measured by the energy absorbed in a notch impact test.

10 - Explorations: beyond the Welder

Lunar Reconnaissance Orbiter
http://www.nasa.gov/mission_pages/LRO/main/index.html

Constellation (Nasa Video)
NASA Video.

Great Designs in Steel 2009
Autosteel.

Racetrack Memory: The Future Third Dimension of Data Storage (5 pages)
Scientific American.

The Power of Belief (video)(download from down the page)
http://www.skeptic.com/

11 - Contributions: Issues with 2.25Cr-1Mo Filler Metals

Case histories are always interesting. In the current June 2009 issue of the Welding Journal, at page 56, an article titled "Evaluating SMAW Electrodes for Coke Drum Construction" addresses some problems that may interest a large audience.

During a major repair program of two large coke drum vessels made of 2.25Cr-1Mo Steel, the original conical sections were removed and new ones were manufactured out of explosion clad stainless type 410 upon low alloy steel base plate.

The qualification of suitable welding procedures required the evaluation of three commercially available matching covered electrode of type E90XX-B3.

Two special Toughness and Temper Embrittlement susceptibility requirements were imposed over and above the usual ones of
ASME Code, Section IX.
Temper Embrittlement (TE) is the loss of ductility subsequent to prolonged heating in the range 700-1000 ⁰F (370-538 ⁰C).

To control the TE susceptibility of the SMAW of the specific material concerned (2.25Cr-1Mo Steel), the researchers established the currently max limit of 15 for the X-bar or the Bruscato factor which is calculated as follows:

X-bar = (10P + 5Sb + 4Sn + As)/100 where the elements content is given in ppm (parts per million).

Suitable welding parameters were established for each one of the three electrodes and the test coupons were tested per Section IX of the ASME Code.
Regarding hardness, impact and chemical analysis (for X-bar determination), considerable differences were found in the results from the different electrodes.

The suppliers were not ready to accommodate the special requirements of the investigators. Several details, most importantly chemistry, were found to influence weld metal properties, together with other factors.

The article intends to stress the fact that in order to meet stringent requirements as spelled out in API 934-A document one must be aware of performance limitations and availability issues of 2.25Cr-1Mo filler metals.

Interested readers are urged to seek the complete article indicated above.

12 - Testimonials

Eli Minoff (e-mail address removed for security)
Date: 14 May 2009, 01:50:18 AM
Subject: Re: PWL#069B - Resources on Welding Books

Excellent and useful bulletin.
Many thanks,
Eli Minoff

On Wed May 06 14:09:25 2009, the following results were submitted from the "Form 5" on welding-advisers.com:

First Name: John
Last Name: Christopher
E-mail Address: (removed for security)
Country: India
Introduce Your Organization: Blackcat Construction, Qatar.
Describe Your Responsibility: supervisor in construction company at Qatar, I am responsible for fabrication of steel structures & piping and welding, q.c. activities like welder approval, wps, ndt.

Questions and Feedback : [...]

Your web page is very useful for working and studying personnel.

13 - Correspondence: a few Comments

13.1 - As the 70th Issue of Practical Welding Letter is now reached, a lot of material is by now available both in the website and in the collection of this Newsletter. It is not surprising therefore, that I myself can have difficulty in locating a page, an article, a comment, a reference that I wrote long ago.

That is why I use and recommend to readers to use the Google Search Box that appears in almost all pages of the Website
(www.welding-advisers.com).

Very often I answer to inquiries just by indicating where to find on the website the presentation of the subject involved. Readers could find directly what they look for by using the same facility, as I suggest in the Contact Us page.

13.2 - A reader asks what he should drink after welding, to counter the effects of having inhaled welding fumes. Unfortunately the fumes may affect the lungs. It is better to provide ventilation or aspiration and avoid breathing fumes. Drinking may be good and healthy but will no protect from fumes.

13.3 - Another reader has a surplus ultrasonic welding equipment for sale.
Unfortunately our readership is probably too limited to find a buyer here. I will gladly provide the contact if anyone is interested.

13.4 - It is still amazing to find people who would like to get a mig welder and start welding having never tried before. A school is needed first, especially to know the dangers. Don't skip learning and training.

13.5 - Laser cutting for outdoors ship scrapping? Has anyone heard of such an application? I would like to know.

14 - Bulletin Board

14.1 - 6th Annual Charting the Course in Welding:
U.S. Shipyards Conference
June 16-17, 2009 - Sheraton Metairie Hotel, New Orleans, La, USA
www.aws.org

14.2 - Int'l Metallographic Society Annual Convention
July 26-30, 2009 - Richmond Va. USA
http://mm2009.microscopy.org/

14.3 - SBI! Home Page (buildit)
The complete site about SBI!, this page starts the process by explaining the "It!" in Site Build It!, then leads the visitor through Case Studies, process, proof, and so forth
http://buildit.sitesell.com/Quark.html

BUILT BY:

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