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PWL#106 - Direct Manufacturing State of the Art,SAW of Superaustenitic, Preventing SCC in Al alloys,
June 01, 2012
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Practical Welding Letter No. 106
June 2012

PWL#106 - Review of Direct Manufacturing State of the Art, Submerged Arc Welding of Superaustenitic alloy AL6XN, limited Mg in filler metal for 5... series Al alloys to prevent SCC, Keyhole Tig, Titanium Welding Workshop, Arc Welding, Resistance Welding Equipment and much more...

June 2012 - Practical Welding Letter - Issue No.106

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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 - Additive Manufacturing

3 - How to do it well: SAW of AL6XN

4 - Aluminum Filler Metals for Resistance to SCC

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article - Keyhole GTAW

8 - Site Updating: Arc Welding, Resistance Welding Equipment (R)

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Titanium Workshop and Conference

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board

1 - Introduction

This 106th issue opens with an article that recommends again to the attention of our readers the problems affecting the development of Additive or Direct Manufacturing, a technology considered promising for a vast range of applications.

A substantial market size is anticipated, but essential improvements must be introduced. That will be possible once the financial restraints are overcome by clarifying the needs and by reducing costs.

Then in Section 3 the very practical problem of centerline cracks in Submerged Arc Welding is addressed for a specific case solved some time ago by Damian J. Kotecki. Only the exceptional knowledge and experience of this author could solve this expensive hindrance.

Readers confronting similar difficulties are invited to let us know. Those who found practical solutions are urged to spread their information to fellow readers.

All know of the importance of correct filler metal selection. In certain cases the selection should follow non obvious strategies. Fortunately useful advice is available and quoted for the benefit of readers who may have met Stress Corrosion Cracking in aluminum alloys similar to those explained in the reference. Section 4 reports on such a case.

Section 7 reports on a development advertised by a commercial company. No endorsement or recommendation is intended, but interested readers are expected to be able to decide on their own if the said development may have definite advantages for their operations.

Therefore the known information is presented, with the suggestion that the new process could be compared for specific applications at least with two other known and successful processes. The benefits may be in the details. Shrewd readers will find what best fits them.

Reminder: Those interested to participate in a Workshop on Titanium Welding can still join the event announced in the last issue. See details in section 11. A Titanium Conference and Exhibition will open later in October. Those active in the field may well mark their Calendar.

Website update includes a new page on Arc Welding and a deeply revised old page on Resistance Welding Equipment (R). Your feedback could help in finding out what really interests you.

Other departments show the regular information at the usual place. Send us your welcome Contributions from your own experience. Enjoy your reading.

Use the Contact Us form to let us have your comments and feedback. Don't use Replay.

2 - Article - Additive Manufacturing

It appears that our Mid March Bulleting No.71 (of Practical Welding Letter) on Direct Manufacturing, is a case in point. Several resources are indicated there, presenting a set of processes dedicated to build material bodies using direct manufacturing procedures.

These methods deposit single drops of material according to precise plans implemented under computer control. The fact that these processes command increasing attention in the manufacturing community is demonstrated in a recently published review, written by Ian D. Harris of the Edison Welding Institute (EWI).

The May 2012 issue of Advanced Materials & Processes (AM&P), a magazine of ASM International, reports at page 25 on the state of the art, starting with a short history of developments. Among other interesting information, we read the ASTM F2792-10 definition of Additive Manufacturing (AM) as "The process of joining materials to make objects from 3-D model data, usually layer upon layer, as opposed to subtractive manufacturing technologies."

Casting and Forging are left out. The article mentions the high cost of the processes that limit (for the time being) the interest to expensive materials and structures, while the time saved (in comparison to traditional methods) may be one of the important considerations.

The article explains that "The industry is on the threshold of a transition from a rapid-prototyping heritage to one requiring robust manufacturing production for eventual widespread commercial exploitation", and goes on reminding the hurdles that have to be overcome.

The various processes used are listed in brief. Follows an appraisal of the global market value, and a presentation of Teams established to advance these emerging technologies.

Economy forecasts are quoted for industry segments as aerospace. Three years ago a workshop was held in the US to establish a roadmap for research for 10 to 12 years.

Then it is reported that EWI organized a Consortium, grouping more than 30 industries, government agencies and academic institutions (listed in the article), with the purpose to advance the manufacturing readiness of AM technologies. In parallel also science has to be developed, to understand the basic facts of each particular AM process.

The article ends with a list of tasks to be worked upon, dealing with different aspects of the general development program. It seems that progress along these lines will occur for sure, while the time frame and the speed will depend on the urgency of requirements and on the capital expenditure that will be dedicated to advancement of Additive Manufacturing.

Readers are urged to seek the original article and to take active part in the race.

3 - How to do it well: SAW of AL6XN

Submerged arc welding (SAW) of superaustenitic stainless steel AL6XN plates 0.325" (9.5 mm) thick, with electrode ERNiCrMo-3 (also called Alloy 625) resulted in frequent appearance of centerline cracking in the root pass. However the same filler metal as covered electrode (ENiCrMo-3) in manual SMAW produced sound welds.

Damian J. Kotecki deals with this query in his note published on page 20 of the Welding Journal of July 2008.

He observes that the above material, whose composition is given by UNS (Unified Numbering System) N08367 where N is the prefix for nickel base alloys, although iron (Fe) is its main component.

He then agrees that the filler metal selected follows common experience that, to avoid pitting corrosion, Ni overmatching must be assured, as provided by the selected filler.

The observed cracks are probably occurring during solidification from the extended temperature range where liquid film is still present while the weld is contracting.

He discusses the roles of dilution and of Niobium (Nb) content. Regarding resistance to solidification cracking, intermediate levels of niobium are dangerous. ERNiCrMo-3 contains 3.15-4.15 %Nb.

According to the author, dangerous niobium levels are more likely to appear with the extensive dilution caused by SAW than with the more limited dilution of SMAW. A similar problem is likely to occur also with 9%Ni steels.

As techniques to reduce dilution (by reducing current) risk to affect productivity adversely, he suggests to switch to other filler metals devoid of niobium, like ERNiCrMo-10 (Alloy 22 0r Ni 6022) or ERNiCrNi-4 (Alloy 276 or Ni6276).

Interested readers are referred to the original article mentioned above.

4 - Aluminum Filler Metals for Resistance to SCC

Stress Corrosion Cracking (SCC) appears rapidly in susceptible microstructures subjected to tensile stresses, either residual or under load, in presence of a corrosive agent.

In aluminum alloys, susceptible microstructures can form in series 2... (Al-Cu-Mg) and 7... (Al-Zn-Mg-Cu) which are among the strongest. In series 5... (Al-Mg), only in those alloys containing 3% or more Mg.

These last alloys, especially in work hardened condition, are prone to grain boundary precipitation, that is to SCC susceptible microstructure, when exposed to moderate temperatures of 66 to 180°C (150 to 350°F) for relatively extended periods of time.

To avoid SCC in aluminum magnesium alloys of series 5... with magnesium content higher than 3% one should care to prevent exposure to temperature in the above range.

The maximum limit of 3% magnesium content should be observed not only for base metals of series 5..., but also for filler metals used to weld them. Suitable filler metals for the above material are ER4043 (no Mg) and ER5554 (2.4-3%Mg).

Based on a Q&A note by Tony Anderson published at page 20 of the Welding Journal, June 2008.

5 - Online Press: recent Welding related Articles

How Metal-Cored Wires Reduce Hidden Welding Costs

Underwater laser welding for nuke plants coming to US

To Seam or not to Seam: Polyzen Creates a Robust Seam in RF Welding of Ultra Thin Films
Sorry! The link was removed by the source.

CSB: DuPont Overlooked Hazards in Fatal Welding Explosion

Laser-based 3D nozzle quality test from Fraunhofer ILT
improves laser material deposition


6 - Terms and Definitions Reminder

Back cap is a cover mounted on a Gas Tungsten Arc Torch, providing sealing, to prevent air from entering from the back side of the torch.

Constant Voltage Power Source is characterized by a typically flat volt-ampere curve. A negative slope of 1 to 5 V per 100 A is common. A small arc voltage change brings a large welding current change.

Dovetailing is roughening of a surface by angular undercutting to cause mechanical interlocking to assure adherence of sprayed layers in thermal spraying.

Electrogas Welding is an arc welding method between a continuous electrode and the molten metal pool, contained in the vertical joint by moving shoes. Welding progression is vertical from the bottom up. Shielding can be provided by a gas or by flux cored wire. See Electrogas Welding

Filler Metal Start Delay Time is the interval between arc initiation and start of filler metal feeding.

Heat Flow transfers heat from the arc source to electrode and workpiece, establishing peak temperature, shape and size of molten pool and heat affected zone, and cooling rates. These characteristics depend on heat input, its distribution and weld travel speed.

Inspection Symbols provide a means for specifying the method of examination to be used, the extent of the area to be examined and the acceptance standards.

Multiple Impulse Welding is a resistance process where one welding cycle is performed with more than one impulse.

7 - Article - Keyhole GTAW

This article introduces a relatively new technology marketed by a commercial company, (, owner of patents on the system, that cannot probably be purchased from alternative suppliers.

No recommendations or endorsement are intended by this publication. The reason is to provide information on a new or less known process which might show advantages in specific applications.

Interested readers should check on their own if it might offer them economic benefits.

A variant of the well known and trusted GTAW (Tig) process was developed in Australia at the end of the 1990s by the Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia's national science agency, through its Manufacturing and Infrastructure Technology (CMIT).

It is offered as a complete system including a special torch, constant current power supply with output of 300-700A (and up to 1000A at 100% duty cycle) and integrated controller.

The main advantage is high productivity for:

  • Suitable applications presenting good joint fit-up, typically pipes
  • Materials: Stainless, Titanium, Zirconium, 3 mm thick up to 20 mm
  • Single pass process with simple square butt joint
  • Full penetration with no filler metal
  • Automated production lines welding in flat or horizontal position
A note on page 12 of the May 2012 issue of the Welding Journal informs that a new demonstration unity was recently installed by the manufacturer in their Salisbury, Australia offices.

As this k-tig welding technology is based on keyhole formation in the joint, it is readily comparable to plasma welding equipment, and to friction stir welding, by taking into account all the elements of any specific production line.

8 - Site Updating: Arc Welding, Resistance Welding Equipment (R)

What are the Pages of This Month? The first is a new page on Arc Welding, including basic information on the physics of the electric arc for welding purposes. How the heat developed by the arc is partitioned between the electrode and the workpiece is explained in some detail.

Then the principal characteristics of the main arc welding processes are presented in brief, with links to other more detailed pages. To see this page click on Arc Welding.

The other page is a revised an rewritten one on Resistance Welding equipment. It should give some orientation on the main characteristics to be defined when shopping for new equipment.

Being informed of the fundamentals should make it easier to discuss the details with manufacturers' representatives. To see the page click on Resistance Welding Equipment.

Check for new pages in the Site Map or subscribe to the RSS feed using the instructions given in every page ( under the Navigation Bar.

Write your comments and feedback in the Contact Us form, and send it.

9 - Short Items

9.1 - Degassing is a procedure used to remove gases from molten metal. It can result from a compound added to molten metal, from gases bubbled up through the metal or from exposure to a vacuum atmosphere in a furnace.

9.2 - Hardness is a measure of the resistance of a material body to surface indentation. It is a function of the stress required to produce some specified type of surface deformation. To express hardness quantitatively, each type of test has its own scale of arbitrarily defined hardness. Indentation hardness can be measured by Brinell, Rockwell, Vickers, Knoop, and Scleroscope hardness tests. See further down how to download the book on Hardness Testing Made Simple.

9.3 - Instrumented Impact Test is such that the load on the specimen is continually recorded as a function of time and/or specimen deflection prior to fracture.

9.4 - Laser Surface Processing is used to modify the metallurgical structure of a surface and to tailor the surface properties to special requirements without adversely affecting the bulk properties. Transformation hardening: a surface is heated so that thermal diffusion and solid-state transformations can take place. Surface melting: results in a refinement of the structure due to the rapid quenching from the melt. Surface (laser) alloying: alloying elements are added to the melt pool to change the surface composition.

9.5 - Magnetizing Force is a force field that produces magnetic induction. It results from the flow of electric currents or from magnetized bodies.

9.6 - Pancake Forging is a rough forged shape, usually flat, that can be obtained quickly with minimal tooling. Can be used for further forging or rolling or for testing purposes. If a specific part is needed, to attain the finished shape and size, considerable machining is still required.

10 - Explorations: beyond the Welder

Ecologists Enlist Drones in Fight Against Illegal Logging

Our Sun Moves More Slowly Than Thought

How Much Water Do Nations Consume?

Apocalypse Soon: Has Civilization Passed the Environmental Point of No Return?
SA4 .

Shadow Fire: 10 Fantastic Photos of Sunday's Annular Solar Eclipse

11 - Contributions: International Titanium Association

REMINDER: in last Issue #105 an Invitation to a Titanium Welding Workshop to be held on June 26, 2012 was published in section 11. Interested readers who did not yet register may still hurry to do so. See details in PWL#105.

MAY 8, 2012
ITA seeks nominations for $20,000 Titanium Applications Development Award

The International Titanium Association, Denver, Colo., is seeking nominations for its sixth annual Titanium Development Award, which features a top prize of $20,000. The award winner will be recognized at TITANIUM 2012, the 28th annual Conference and Exhibition, which will be held October 7-10th at the Hilton Atlanta.

Note: - Unfortunately the deadline to submit nominations was May 21st.

The award is open to ITA members and non-members alike. Nominations are sought for individuals, teams or organizations from the global titanium industry or academic community that demonstrate significant achievement towards improving and expanding the use of titanium.

Brett Paddock, president and chief executive officer of Titanium Industries Inc., Rockaway, NJ, is the committee chair for the ITA's Applications Development Award. Jennifer Simpson, executive director of the ITA, said the Applications Development Award represents the continuing efforts of the ITA to support and inspire its members (more than 200 organizations and over 1,500 individuals) as well as promote new global business initiatives for the use of titanium.

An online version of the nomination form may be downloaded (in a PDF format) directly from the ITA's Web site at

12 - Testimonials

On Tue May 01 11:46:25 2012, the following results were submitted from the "Form 5" on
Name: Marcel Bauer
E-mail Address: removed for security
Country: Canada

Question or Feedback: Thanks for the article - "Improving GMAW performance".
Very good info.

Name: Habib Ur Rehman Siddiqui
Country: Pakistan
Date: 10 May 2012, 04:29:46 AM
Subject: Re: sealing
Dear respected Sir,
Thanks a lot and real appreciation from my side for sharing valuable info. [...]

13 - Correspondence: a few Comments

The Contact Us Form that had been modified to include additional details pertaining to the query in cause, revealed itself too cumbersome. It is now again simplified to be more user-friendly. It is hoped that this version will be more accepted and used.

Readers should be aware that the more details are provided to describe the case for which advice is sought, the clearer the question will be. It will be therefore easier to give a useful and complete answer.

14 - Bulletin Board

14.1 - 65th Annual Assembly & International Conference
of the International Institute of Welding
July 8-13, 2012 - Hyatt Regency Denver at the Denver Colorado Convention Center.

14.2 - GAWDA Annual Convention.
Sept. 9–12. The Broadmoor, Colorado Springs, Colo.

14.3 - 15th Annual Aluminum Welding Conf.
Sept. 18, 19, Seattle, Wash.

14.4 - TITANIUM 2012, the 28th annual Conference and Exhibition
October 7-10th at the Hilton Atlanta

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