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PWL#127 - SAW Flux, Etching Brazed Sections, Resistance Spot Brazing, Scarce Material Supplies
March 03, 2014
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Practical Welding Letter No.127
March 2014

Submerged Arc Welding Fluxes - A Primer (Part 2), Etching Brazed Sections for Optical Miscroscopy, Filler metal for Resistance Spot Brazing, Warning from a Study on Scarce Material Supplies, New pages on Service-failures and Accident-investigations, New Mid Month Bulletin 93, Review of Articles on Positioners, Regular Sections and much more...

March 2014 - Practical Welding Letter - Issue No.127

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This publication brings to the readers practical answers to welding problems in an informal setting designed to be helpful and informative. We actively seek feedback to make it ever more useful and up to date. We encourage you to comment and to contribute your experience, if you think it may be useful to your fellow readers.
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1 - Introduction

2 - Article - Submerged Arc Welding Fluxes - A Primer (Part2)

3 - How to do it well: Etching Sections of Brazed Joints

4 - A Filler Metal used for Resistance Spot Brazing

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article: Scarce Material Supplies

8 - Site Updating: Service-failures (New), Accident-investigation (New), Bulletin_93

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Positioners

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board

1 - Introduction

Hello Readers, you are welcome to this 127th Issue of Practical Welding Letter, that opens with the second part of the Primer on Submerged Arc Welding Fluxes. Thanks again to our contributor, Naddir M. Patel, who generously offers his teachings to this audience.

Readers are reminded that the recently published Mid Month Bulletin 93 provides a rich list of Resources on Submerged Arc Welding Flux, offering additional information on this important subject.

Then we report from a recent issue of the Welding Journal on practical advice for etching and examining sections of brazed joints by optical microscopy.

Further down we summarize, from another, older issue of the same journal, an unusual test performed on a dissimilar material joint, by a seldom heard of process, namely resistance spot brazing.

While the practical applications of such a combination may be limited, the curiosity of attentive readers might be caught by the unaccustomed circumstances described in this research.

The next major article, which refers to a Yale University search, that can be found online, admonishes that severe constraints might limit future further technological progress.

This if suitable substitutes for critical rare material are not developed in time and if more rational utilization of nonrenewable resources is not implemented as needed.

Three new pages enrich our website as shown further down in Section 8: readers are invited to browse through them, for the case that useful hints to their usual interests could be gleaned from them. Service-failures and Accident-investigations are approached in two new pages, as success is sometimes broken by unexpected occurrences.

On a different subject additional useful information can be obtained from the new Mid Month Bulletin already quoted above.

The use of Welding Positioners could be critical to achieve acceptable production efficiency.

Their proper selection may be quite difficult however, especially as production plans may change unexpectedly.

Some help may be welcome in the process of deciding which types would be most useful in given situations.

The short note in Section 7 points to two descriptive articles from the Welding Journal that explain some of the reasons that may be helpful to reach thought out decisions toward procuring suitable auxiliary equipment.

The other usual sections can be found where expected. It is hoped that the majority of readers will find some useful information at least in part of this publication.

You can always use the Search function from almost every Welding Advisers page. You can also browse the Site Map or the Index Page to find references to the subjects you may look for.

Titles of Articles from Practical Welding Letters can be found in the Welding Topics page.

Links to the PWL complete list are available from the Index of Past Issues of PWL.

The subjects treated in the Mid Month Bulletins are listed in the Welding Resources page, updated regularly.

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2 - Article -

Submerged Arc Welding Fluxes -
A Primer (Part 2)

by Naddir M. Patel

[Note: Part 1 of this Article is available at PWA#126 (2).]

Tandem SA Welding

Tandem Submerged Arc Welding

[From: Improving productivity with submerged arc welding

Based on composition, SAW fluxes are also described as Acidic, Neutral and Basic types.

A factor called 'basicity index' (BI), which is a measure of the amount of oxygen transferable to the weld metal, is used to classify them.

The BI is based on a formula containing the amount percentage of each of the ingredients in any given flux. It needs not bother us, except that its value should be known in any specific case.

The importance of this index derives from the correlation between the oxygen content of the weld metal and microstructure/properties, as oxygen reduces both strength and toughness.

  • Acid fluxes generally have a basicity index varying
    from 0.5 to 0.8.
  • Neutral fluxes vary from 0.8 to 1.2;
  • Basic fluxes vary from 1.2 to 2.5 and
  • Highly basic fluxes vary from 2.5 to 4.0

Notes from ASM HANDBOOK Vol. 6A page 338:

  • Fluxes with low Basicity Index (less than 1) are generally used where high impact toughness is not a requirement.
  • Fluxes with medium Basicity Index (1 to 2) generally produce weld metal with higher toughness in single pass or two-run welds.
  • Fluxes with high Basicity Index (>2) generally produce weld metals with higher toughness properties in multiple-pass welds.

Table 2
Basicity Index Effects

Flux Type Advantages Disadvantages Applications
Acid Quick peeling of slag
Good bead profile,
Increases Si,
Decreases C
in weld metal.
Weld metals with
High O content.
Low notch toughness.
Lower heat input.
Water pipelines,
gas cylinders,
Spiral welding of pipes.
Neutral Less O in welds, higher welding speeds. Moderate impact values. Same as Acid but allowing higher speeds.
Basic Least O in welds, High notch toughness values. Lower welding speeds, Strict heating protocols.
S reduction possible. Most efficient with alloy wires.
Pressure Vessels, High notch toughness requirements.

An acidic flux will also increase the weld metal oxygen content (and oxide inclusions) leading to a drop in impact (CVN) values.
[Note: CVN stands for Charpy V-notch Number (Charpy Energy), the output of a Charpy impact test]

On the other hand highly basic fluxes, while ensuring higher weld toughness (CVN), are most susceptible to moisture.

By using acidic (high SiO2) fluxes, the C content can be reduced, while the S and P can be addressed by using wires with extremely low values of these elements to ensure the required material balance.

On the operational side, weld metal oxygen content increases with welding current and decreases with increased welding speeds.

A good practice, therefore would be to employ a LSO (long stick out) or increased EE (electrode extension) process, using a flux which has a fast freezing slag.

The increased electrode extension ensures a higher wire feed rate, translating to a higher current, which in turn has to be adjusted by a higher welding speed.

While an increased EE slightly reduces weld penetration (less than 10%), it generates a softer (cooler) arc and has been proved to be more tolerant to poor joint fit-up.

Each category has its own applications. For example, in steels susceptible to solidification cracking, the problem is aggravated in the presence
of S, P and C.

SAW fluxes are also described in terms of reactivity of their components during welding.

Thus active fluxes are those that add or remove elements from the weld zone; whereas an inactive flux does not participate in any reactions.
C, Mn and Si are the main participants.

Generally if flux components do not decompose during welding, the flux is deemed as inactive.

Table 3
Activity Effects

Flux Type Advantages Disadvantages
Inactive or Neutral Fluxes
(No modif. of Chem.Analysis)
Lower O content in weld metal. Multiple (recycled) applications.  

Active (Custom Mixtures) for high-speed single-pass weld. Adds alloying elements
Mn and/or Si.
Single applications. Cannot be recycled.

These criteria (Method of manufacture, Basicity Index and Chemical activity) are not absolute and usually form subsets with one another.

For example a MnSiO3 flux can be fused, acidic and active. It will add Mn and Si to the weld metal while removing C.

However, in the market there is a lot of confusion associated with this term.

Many sales representatives confuse neutral (basicity) with in-activity of the flux.

If, based on the dilution occurring in the weld, the welding engineer prefers to channel all the alloys into the weld metal through the wire, then he/she must insist on a non-active flux.

The basicity of the flux has minimal influence on this.

Weld metal hydrogen, due to moisture in flux has been established as a major cause of chevron cracking.

Present as transverse cracks at a 45° angle to the weld surface, these weld metal cracks are difficult to locate unless special UT (Ultrasonic testing) methods are used.

This parameter, critical to quality, can only be addressed through a customized baking temperature and residence time of the flux in the oven, a factor often not strictly adhered to.

Fluxes are sometimes classified in terms of the diffusible hydrogen of weld metal.
Some fluxes must be dried prior to use to produce low weld metal hydrogen values. Consult manufacturers.

Unlike the stick electrode used in SMAW, where the flux is extruded to the rod in fixed proportions, leading to a generally uniform melting rate, the SAW flux proportions are user determined and have an effect not only on its consumption patterns, but also on the quality of the weld produced.

Too shallow a flux layer can result in air infiltration causing porosity and in extreme cases arc flash. Too deep a flux layer can result in a poor and uneven weld profile.

Recirculation of the flux is also an issue. Whereas the principle of re-heating a flux to optimum temperature prior to use is good practice, factors to consider are whether the flux being used is simply too brittle.

Generation of fines during the pneumatic conveying may change the composition of the flux resulting in uneven weld bead and non-uniform weld chemistry.

There are of course other related issues in flux recirculation systems, such as the possibility of slag and iron oxides not being sieved out efficiently but that is digressing from this topic of optimizing the methodology of choosing a submerged arc welding flux.

In summary, it is critical for the welding engineer to gain an understanding of the nature of submerged arc welding flux, and prescribe those requirements on a data sheet.

Each flux offers unique operational and performance characteristics. Again, the onus is on the welding engineer to select the one that is most optimal for the application.

[Note: The selection of the general class of flux required can be based on the considerations exposed above.
Readers may wish to refer to the Flowsheet link, offering a summary of the reasons for selection].

This will ensure a first time right welding procedure qualification and the generation of work instructions that will ensure that welds of good quality are repeatable across different shifts and welders.

A logic path that can be proposed to a conscientious engineer is to set up a data sheet based on the parameters of the WPS and the ground situation on the shop floor.

[Note: A Sample of such a document is available at the Datasheet link.
Specific data should be adjusted for the actual situation on hand].

This data sheet must include the wire chemistry being used and the expected weld metal chemistry and mechanical properties.

Once completed, it should then be submitted to manufacturers/vendors.

Keep in mind that the manufacturers supply data sourced from their laboratory and their welder is an expert with lots of experience.

As such, field conditions are never factored in, and the field conditions in each manufacturing/fabrication facility are unique.

It is up to the welding engineer to develop a middle ground to ensure a good weld that is repeatable across all his welders, not just the experts.

Unfortunately the welding engineer, who ignores the make up of the flux and the influence of its various ingredients, is at loss when required to customize the flux-wire combination to the job on hand.

If possible he/she should try to enlist the help of the manufacturers' experts.

An example of such a customization is given in an article by Naddir M. Patel published (7) in PWL#074 for October 2009.

Online References available for further study of the subjects of this article can be found in the Mid February Bulletin 93.

Tandem Twin SA Welding

Tandem Twin SA Welding

[From: Improving productivity with submerged arc welding

3 - How to do it well: Etching Sections of Brazed Joints

WJ CoverFeb_14

The Q&A Brazing column of the February 2014 issue of the Welding Journal offers, at page 26, useful hints on materials and procedures for metallographic preparation and etching of sections of brazed joints for optical microscopy.

It is recognized that many laboratories prefer nowadays to use scanning electron beam microscopy (SEM) that does not need etching, to perform regular quality assurance tasks on brazed joints.

But for those who cannot use such inspection because the cost of equipment is not justified by their present workload, optical metallography of polished and etched brazed joints is still a valid inspection technique.

Practical information and etchants composition are presented there for several brazing filler metal alloys and different base metals, along with application instructions.

Readers facing this kind of problems are urged to seek the original column in the said issue of the Journal.

4 - A Filler Metal used for Resistance Spot Brazing
WJ CoverMay_10

The May 2010 issue of the Welding Journal reports, on page 101-s, on an experimental study that used a modified Silver Copper eutectic alloy to spot braze together nickel and titanium, a dissimilar materials joint.

Interested readers are referred to the quoted article at

This setup is unusual in that it uses resistance heating to melt the brazing alloy and to perform a brazement.

It is interesting, as the successful application of uncommon combinations of materials and processes might suggest that even in unheard of circumstances, exploring uncharted spaces might solve difficult problems.

The article describes materials, setup, current and time pulses. For comparison, also regular spot welding was performed on the same base metals joint, without brazing alloy.

Tensile strength results for those welds that were performed at higher current values were higher for brazed joints (including filler metal) than for those of welded joints (without filler metal).

The authors attribute the better results also to the action of the minor additive element in the brazing alloy (1% Mg, vs. 71% Ag and 28% Cu), that apparently improved the wettability of the filler metal, thus resulting in good wetting and homogenous diffusion of base metal and hence produced a joint free from porosity at the interface of Ti and Ni.

As a result, the strength of the spot brazed joint was improved significantly.

5 - Online Press: recent Welding related Articles

Soft metal weld makes for stronger infrastructure

Can Google's robots build a new future for US manufacturing?

European Space Agency Chooses Microfabrication Company Primoceler for Engineering of New Optoelectronics Package

The art of bevel cutting

Connect+ Nov/Dec 2013 (8 pages)

6 - Terms and Definitions Reminder

Procedure Qualification is the demonstration that welds made by a specific procedure can meet prescribed standards.

Resistance Welding Voltage is measured through the workpieces, between the resistance welding electrodes.

Split Pipe Backing is a pipe segment used as a backing for welding butt joints in round bars.

Twin-wire Submerged Arc Welding process is recognized by the American Welding Society (AWS) as parallel wire that uses two relatively small-diameter wires but only a single power source and typically a single contact tip.

Uphill welding means welding with an upward progression.

Vertical Welding Position is that in which the weld axis, at the point of welding, is approximately vertical, and the weld face lies in an approximately vertical plane.

Wax Pattern for Thermite Welding is wax, molded around the workpieces, to the form desired for the completed weld.

Weld axis is a line through the length of the weld, perpendicular to its cross section, and passing at its geometric center.

7 - Article: Scarce Material Supplies

Materials are essential to current and future civilization. Like with so many other resources, human behavior has always been directed to maximize immediate profit, without much thought of future needs.

Now a global study, performed by Yale University, titled On the materials basis of modern society, points out the possible future scarcity of some of the elements as their use increases.

The study concerned substitution potential for 62 different metals, and found that alternatives are inadequate or not existent.

Performance improvements of many technological applications are dependent on development of materials with improved properties, which take time and efforts to reach practical gains.

However temporary or permanent scarcity of crucial elements might hinder progress and limit achievements.

The conclusion of the study is reported hereafter:

"It thus appears that society will need to pay more attention, to the acquisition and maintenance of nonrenewable resources, than has been the case in the past.

Growing populations, growing affluence and the materials diversity of modern technologies are straining the resource capacities on which we draw.

The situation need not inspire panic, but should instead stimulate more diligent and more comprehensive approaches to the balance between supply and demand across the entire periodic table."

Download the entire Document (6 pages) from

Periodic Table of Substitute Performance

The Periodic Table of Substitute Performance

[From On the materials basis of modern society

8 - Site Updating: Service-failures (New), Accident-investigation (New), Bulletin_93

The Pages of this Month are new. To find new pages easily, readers can subscribe to the RSS service (See instructions in every page below the left column (Nav Bar).

Or they could browse regularly the Welding Blog, besides checking regularly the Site Map, or the Index Welding Page.

The Service Failures page provides first information on how to manage an accident, by taking care not to obliterate the most important cues that will help experienced investigators to get to the root cause.

All should be instructed not to touch the broken parts nor to put them together again (Humpty Dumpty...) because this simple action can delete the very signs pointing to the failure origin and causes.

Then utmost care should be engaged in describing and reporting the succession of events culminating in the failure.

This brings us to the next stage, that of conducting the Accident Investigation, preferably to be performed by someone with knowledge and experience in this kind of work.

The assistance of well equipped and staffed laboratories may be essential to the success of the endeavor, the main problem being to determine the real consistence and state of the materials involved and their suitability to sustain the service condition actually operating on the equipment in cause.

The last new page of the current updating is the current Mid Month Bulletin 93, presenting online Resources on Submerged Arc Welding Flux.

This auxiliary page intends to help in extracting the maximum information from the article published above in section 2 (Part 2) and from Part 1, published in the last issue of this publication. See PWL#126.

We hope that the subjects treated in the above mentioned pages might interest at least a part of our readers, who may be called to take pertinent action in certain circumstances.

Questions, comments and feedback are always welcomed. Don't use Reply, use the Contact Us form instead.

9 - Short Items

Do you know...

  • to avoid weld cracking?
    See Weld Cracking.

  • ...the Global Welding Market?
    [Sorry, removed by the source]

  • to weld supersize structures for heavy-hauling?
    See Belta.

  • ...the % of Manual vs Automated welding?
    Sorry! Link disconnected

  • to join the race for AWS Awards?
    See Sys.Con.

9.1 - Pusher Furnace is a type of continuous furnace in which parts to be heated are periodically charged into the furnace in containers, which are pushed along the hearth against a line of previously charged containers thus advancing the containers toward the discharge end of the furnace, where they are removed.

9.2 - Run-out is the unintentional escape of molten metal from a mold, crucible, or furnace. Also an imperfection in a casting caused by the escape of metal from the mold.

9.3 - Superplastic Forming (SPF) is a strain rate sensitive sheet metal forming process that uses characteristics of materials exhibiting high tensile elongation. During superplastic forming, gas pressure is imposed on a superplastic sheet, causing the material to form into the die configuration.

9.4 - Tolerance is the specified permissible deviation from a specified nominal dimension, or the permissible variation in size or other quality characteristic of a part.

9.5 - Uniform Elongation is that measured at maximum load and immediately preceding the onset of necking in a tensile test.

9.6 - Vent is a small opening in a foundry mold for the escape of gases.

10 - Explorations: beyond the Welder

A Natural Gas Power Plant with Carbon Constraints-- and an Expiration Date

Cosmic Mismatch Hints at the Existence of a "Sterile" Neutrino

Solar-Powered Cars Inch toward the Mainstream

Prions Are Key to Preserving Long-Term Memories

New Evidence Suggests That Neandertals Buried Their Dead

11 - Contributions: Positioners

WJ CoverFeb_14

On this subject one can see our website page on Welding Positioners.

Furthermore, the recent Welding Journal February 2014 issue, offers two articles reviewing Positioners and their use.

The main point of using positioners to perform welding operations is to improve efficiency, by presenting any weld in the easiest and most reachable standing for the welder to work on it.

The problem is that each positioner is designed to move in certain ways bodies of given weight. So that only certain types or classes of parts are best suited for given positioners.

Given the substantial investment in such specialized type of equipment, not only the advantage of its use must be measurable but, to justify its cost, it should be applicable to a vast range of common production parts.

Positioners are essential to manipulate heavy weights, as common in many industrial implements.

Before deciding which positioner they should procure, Users should seek as many examples as possible of available equipment, to study which type and size would be suitable for their most significant operations. The reported articles may be a good starting point.

The first article, at page 34, offers Tips for Selecting a Positioner, based on several factors, like sequence of operations, welding process, accessibility, safety and more. It is suggested that advantages and disadvantages may coexist in given equipment suitable for certain applications.

Determining the best solution may depend upon understanding final expectations and process limitations. A review of the main types of Positioners follows, described as tilt-rotate, head-and-tailstock, tilting models of turning rolls, and turntables.

The article concludes that the actual positioner design required to accomplish the job will become apparent once the sequence of operation, process, accessibility issues, and safety concerns have been identified and addressed.

That would permit to establish an acceptable machine design.

The capacity of the selected positioner model will be determined by considering part and fixture weight and location of center of gravity.

The second article, at page 42, asks "What Can a Welding Positioner Do for You?" and answers by emphasizing the advantages of easing welding jobs and increasing safety, especially for heavy machinery.

They may even permit the work of less proficient welders, by placing weldments at optimum angle for comfort and accessibility.

Positioners may permit further benefits by allowing automation of certain welding operations, because automated welding improves quality and increases overall output.

The review lists less common types like Ferris-wheel-type positioners, Five-axis and drop center, L-hook positioners and dual trunnion turntable, each of which suitable to handle special or uncommon geometries.

The article concludes that Weld positioners have proven to be a productive investment for any company seeking more efficient routes in their welding practices.

Interested readers are urged to seek the original articles in the issue of WJ pointed out above.

12 - Testimonials

From: "Todd Sprentall"
To: welding-advisers
E-Mail Address: removed for security
Date: 03 Feb 2014, 07:39:36 AM
Subject: RE: PWL#126 - SAW Flux, Fitting Alignment, ...

[...]I very much enjoy enhancing my welding knowledge level by reading your monthly publication.

Best Regards,

Todd Sprentall, B.Eng

Date: 03 Feb 2014, 09:19:32 AM
Subject: Submission from

On Mon Feb 03 09:08:05 2014, the following results were submitted from the "Form 5" on

Name: Ronald Morrison
E-Mail Address: removed for security
Country: Chile
Organization: independiente
Your Task: todas
Details: Gracias.
Gracias por su informacion, es y ha sido muy interesante para mi. Felicitaciones y exito en todo

[Translation: Thanks for your information, it is and has been very interesting for me.
Congratulations and success in all

Febrero 3 de 2014
Hola Elia,
Reitero mis agradecimientos por tu pagina
muy educativa y con un basto numero de temas.
siempre atento a tu correo
Saluda atte.
Ronald Morrison

[Translation: I reiterate my thanks for your site
very educational with a vast number of topics.
always attentive to your email.
Ronald Morrison]

13 - Correspondence: a few Comments

I receive from time to time requests for information on sources where-from to download standards and other documents.
Although it is possible that unauthorized sources make available for download copyrighted documents, it should be understood that such information is generally for purchase.

As such they should be purchased either from the legitimate originators or from authorized distributors.
Schools or academic libraries may have special arrangements for discounted prices.

Sorry, we cannot help. That said, readers should be aware of the fact that huge repositories of information, including professional courses from distinguished Universities are now made available to all at no cost.

Such bounty can be tapped instantly and globally. We could consider compiling a list of major sources providing lessons on subjects relevant to our main field of interest.

Curious readers are invited to comment and to share their experience. Feedback will be appreciated.

14 - Bulletin Board

14.1 - Stainless Steel Conference.
March 25, 26. Loews Philadelphia Hotel, Philadelphia, Pa.

14.2 - FABTECH India colocated with Weld India.
April 10–12. Pragati Maidan Exhibition Complex, New Delhi, India.

14.3 - Weld Cracking Conference.
April 15, 16. Hilton Garden Inn Denver Downtown, Denver, Colo.

14.4 - Aluminum Conference.
April 28–30. Hotel Monteleone, New Orleans, La.

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