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PWL#116 - Welding Cast Stainless, Underwater Work, Repairing 304H, Additive Manufacturing Advances
April 01, 2013
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PWL#116
Practical Welding Letter No. 116
April 2013

Welding Cast Stainless Steels, Underwater Inspection and Welding, Filler Metal for Repair Welding 304H, Advances in Additive Manufacturing, Spot Weld Quality for Automotive Industry, Cold Welding (R), Creep Resistant Steels(R) and much more...


April 2013 - Practical Welding Letter - Issue No.116


Special Announcement

Spring Survey

The Spring Survey announced here was intended to take place during the month of April 2013. It was cancelled after that time.

Readers wanting to comment on the usefulness (or lack of it) of our publication Practical Welding Letter are invited to do so at any time using the Contact Us Form whose link is given hereafter.


Important Notice

The Mid March Issue of Practical Welding Letter, Bulletin 83, dealing with Resources on Adaptive Welding Process Control was not distributed by e-mail but it is available at Bulletin 83 and from the Welding Resources Page.


DON'T USE REPLY to send your messages! Use the Contact Us form instead.

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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TABLE of CONTENTS

1 - Introduction

2 - Article - Welding Cast Stainless Steels

3 - How to do it well: Underwater Inspection and Welding

4 - Filler Metal for repair welding 304H

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article: Advances in Additive Manufacturing

8 - Site Updating: Cold Welding (R), Creep Resistant Steels(R)

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Spot Weld Quality for Autos

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board


(Sponsored links)

1 - Introduction

This new issue of Practical Welding Letter, the 116th, opens with a call to all readers to kindly devote a few minutes to answer to our Spring Survey.

We hope to get lots of responses, especially from those who appreciate our efforts, because the study of the reactions will help us see what needs improvement. Thanks.

The first article introduces a short review of Cast Stainless Steels and on how to weld them.

As always, one should start with the complete knowledge of composition and characteristics of the Cast Stainless to be welded.

Then, having selected a process, one should look around to pick up the most suitable filler metal for the job.

Much depends on the service conditions of the part involved.
That is why one cannot find a simple table with the suggestion of one filler for each base metal.

Then we report some hints on what a career in underwater welding may look like, from someone deeply involved in teaching and training new candidates.

A practical approach is suggested, by a renowned world expert, for those evaluating the use of stainless filler metal for welding nickel base alloys: be warned of the dangers.

Those who like keeping track of innovations should mark Additive Manufacturing as a promising revolutionary manufacturing technology being promoted by most serious and costly efforts.

In the next future, successful results will change many industries in fundamental ways.

Spot welding is still most used in the automotive industry. Looking after the quality of scores of individual welds in constructions built for safety is not an easy job.

It requires understanding of requirements and skill in applying them in practice, seriously and constantly.

Rewritten, edited and updated website pages should help readers reach those levels of welding knowledge that best satisfy their needs. In this issue the revised pages deal with Cold Welding and Creep Resistant Steels. Feedback is most welcomed to meet readers expectations.

The other sections are published as usual, you know where to expect what.
It is hoped that most of readers will find some useful information also in 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 is available from the
Index of Past Issues of PWL.

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

Please enjoy reading, and use the Contact Us form to send your comments, feedback or questions.


2 - Article - Welding Cast Stainless Steels

Cast stainless steels are usually broadly divided into two main categories.

One, indicated by the letter C, groups corrosion resistant alloys designed for service in aqueous vapors at temperature up to 315 °C (600 °F). The other, designated by the letter H, indicates heat resistant alloys for service at temperatures exceeding 650 °C (1200 °F).

Welding may be required for repairing castings defects (after thoroughly removing them to obtain clean and sound metal) or for joining other elements to cast parts. Arc welding is commonly used, as well as high energy processes.

A wide choice of filler metals is available for most purposes. For welding together similar alloys, matching compositions are suggested.
For welding low nickel corrosion resistant cast alloys 308L or 316L can be used if matching alloys are not found.

For higher nickel C and H alloys, consumables such as 20Cb-3, and nickel alloys as C-276, 625, Inconel 82, 92, or 182 can be used.

Microstructures of cast alloys do not reflect those of wrought alloys.

During dendrite solidification, segregation causes local changes in composition and in structure.

Mixed and duplex structures are common, with ferrite islands in matrix of austenite or martensite.

A few of the C alloys displaying martensitic microstructure may be negatively affected by welding.

To avoid quench cracking and mechanical properties degradation, preheating in the range 200 to 315 °C (390 to 600 °F) is required.

Post weld heat treatment (PWHT), as stress relieving, is done at 590 to 620 °C (1095 to 1148 °F), to restore ductility somewhat.

For age hardenable alloys, aging or precipitation hardening follows solution annealing.

Regarding welding, major risks involve hot cracking either during solidification of the fusion zone or in the heat affected zone.

Austenitic cast stainless steels are more at risk than those with ferritic mixed to austenitic structure.

Alloys whose welds solidify as primary delta ferrite are more crack resistant than those solidifying as primary gamma austenite, except if charged with higher levels of sulfur and phosphorus.

Some alloys, typically HK-40 (a 25Cr/20Ni alloy) solidify as primary austenitic, but the last phase to solidify is a eutectic-like Cr7C3 carbide constituent.

At certain relatively high carbon levels, this constituent remains liquid for a longer time and this contributes to "healing" of hot cracks, but ductility may be too low to be useful in practical applications.

Welding of corrosion resistant cast stainless steels may cause sensitization, as it happens in wrought stainless.

This modification, as explained in our page on Stainless Steel Welding, may produce areas of material prone to corrosion.

Sensitization consists in the depletion of Chromium by precipitation of chromium carbides, when the base metal is heated in the range of 400 to 900 °C (750 to 1650 °F). The obvious cure, where applicable, is to use low carbon versions of base materials.

General precautions invoke use of the lowest heat input possible, without any preheating. Post weld heat treatment should be used as stress relieving or as solution and aging where applicable.

For alloys highly sensitive to hot cracking, buttering the edge with ductile metal before welding may be the solution.


3 - How to do it well: Underwater Inspection and Welding

For young people considering a welding career, it may be important to get updated evaluations on what their profession will look like, in the long term. One such introduction to underwater welding trade was recently published in the March 2013 issue of the Welding Journal at page 76.

Written by a person familiar with the training of scores of candidates, the article may offer new perspectives to be taken into account before coming to such a fateful decision.

As the contact address of the author is given there, the opportunity to inquire on other aspects not fully clear to the reader, may be a much needed incentive to dig deeper in this fascinating subject.

The article describes a number of scenarios where a welder diver may find him/her/self while working on assignments in the water. These look somewhat scaring to the unprepared, but quite routine for experienced workers.

Inspecting possible damages on structures subjected to storms or hurricanes may be part of the work. Oil rigs, pipelines and partly submerged bridges are among constructions in need of inspection and possible repair.

Proper education and certification are part of the necessary preparation that lasts between five and nine months. Special techniques must be acquired by welders working underwater, to cope with the unusual conditions.

Readers looking for an informed introduction to this kind of work are urged to look for the original article whose details are shown above.

Quite by chance, in the same Journal issue, at page 20, a welder recounts his own experience. At age 54, after a successful dry welding career that lasted more than 30 years, he took the plunge.
He became first a commercial diver, and then learned underwater welding.

He describes his development as one of his most challenging and rewarding career moves. He describes his expanded career as exciting and rewarding.

Here are his closing remarks: "You accomplish something unique in the welding world; most people can only imagine what it is like working or welding underwater. I know I did until five years ago."

Prospective students are urged to seek this welder-diver's note as indicated above.


4 - Filler Metal for repair welding 304H with E308H-16 electrodes.

The most informative Q&A column of Damian J. Kotecki, a world renowned expert on Stainless Steels, published in the last issue of the Welding Journal for March 2013 at page 14, addresses as usual a practical problem.

A reader was inquiring if the repair welding of old 304H steam line tubing was risking dangers.

Originally the tubing had been welded with ENiCrFe-3 electrodes. Now the proposed replacement would have used stainless E308H-16 electrodes (less expensive) rather than nickel alloy electrodes.

The Author, referring to the WRC-1992 Diagram, locates the positions of the old weld metal and of the new tubing base metal. He notes that both the nickel filler metal electrode and the old weld metal mixture fall outside the diagram because of their high nickel equivalent.

He then remarks that any new stainless filler electrode deposited on old weld metal, would be, because of dilution, in the austenitic primary solidification area, which is at high risk of solidification cracking.

He then suggest two ways out of the quandary. The first would be to eliminate all occurrences of old weld metal by cutting out as much as necessary of the old pipe welds: in this case the proposed stainless consumable would be usable without danger of solidification cracking.

The second way would be to continue to use the old nickel base filler metal (more expensive) even for the new welds, for the case that locations of old weld metal mixed with nickel alloy are hit.

The bring home lesson is that welding stainless on top of nickel base alloy should always be avoided.


5 - Online Press: recent Welding related Articles

Welding Quality Systems To Support The Medical Device Industry
Manufacturing.

5 tips for successful aluminum GTAW
Fabricator.

The Value of Comfort
Metal Forming.

Welding Inspector: Become a Welding Inspector in 5 Steps
Degree Directory.

Quality inspection for remote laser applications
Industrial Lasers.


6 - Terms and Definitions Reminder

Abrasion Soldering is a variant where the base metal faying surfaces are mechanically abraded in the process.

Bond Specimen is a special test piece on which was applied a thermal spray deposit, to determine the deposit strength and the bond strength of the deposit on the substrate.

Ceramic Rod Flame Spraying is a thermal spray process variation in which the surfacing material is in the form of a ceramic rod.

Doped Solder contains a small amount of an additional element used to provide retention of base metal characteristics.

Excessive Sheet Separation is the unacceptable distance between faying sheet surfaces, adjacent to the weld, after spot, seam or projection welding.

Final Current, in resistance welding, is the current after downslope time but before current shut off.

High-frequency Upset Welding is a variation in which high-frequency welding current is supplied to the abutting workpieces through electrodes.

Intermediate Soldering Flux leaves a residue that generally does not attack the base metal, although the original composition may be corrosive.


7 - Article: Advances in Additive Manufacturing

We reported previously on Additive Manufacturing. An article on this subject was published (2) in Issue 106 of Practical Welding Letter (PWL) for June 2012.
Click on PWL#106 to see it.

Earlier we reported in our Mid March 2012 Bulletin 71 on Direct Manufacturing, by publishing a list of Links to online Sources introducing various aspects of this subject.
Click on PWL#103B to see it.

A recent publication, an article on Out of Bounds Additive Manufacturing was published in the Advanced Materials & Processes Magazine, an ASM International publication, March 2013 issue, at page 15.

It illustrates the efforts of a joint initiative by Lockheed Martin and Oak Ridge National Laboratory (ORNL) to set up a Big Area Additive Manufacturing System (BAAM) with the potential to be not limited by the size of the manufactured parts.

They will work with the recently established U.S. Department of Energy's (DOE) Manufacturing Demonstration Facility (MDF).

The system is designed to single out the problems of integrating multiple materials within single components.

Many of the process-optimization tasks involved are still being defined. The system is designed to grow with application of lessons learned while developing applications.

President Obama recently cited Additive Manufacturing as the next revolution in manufacturing with the potential to change the way we make almost everything.

The trend towards unbounded Additive Manufacturing will be highlighted in the
Technical Sessions of Aeromat - Conference and Exhibition,
April 02 - 05, 2013 - Bellevue, WA - Meydenbauer Center.

AeroMat supports this initiative with a series of sessions that will include presentations covering the state-of-the-art in additive manufacturing (AM) including main stream and novel AM.

Processes, design practices, applications as well as quantification of benefits.

http://www.asminternational.org/content/Events/aeromat/technical.jsp

In the words of Ed Kubel, AM&P Senior Editor:

"The technical program at this year's AeroMat Conference and Expo gives a clue about the growing interest in this technology in the aerospace area. No less than five sessions are devoted to AM in the areas of high-temperature alloys and coatings, alternative manufacturing approaches, processing and microstructure modeling, and titanium alloy-parts fabrication."

For more information readers are invited to see the above indicated article.


8 - Site Updating: Cold Welding (R), Creep Resistant Steels(R)

The reviewed and updated Pages of this Month deal with unrelated subjects. Their importance stems from the fact that the processes grouped under the first title, Cold Welding, may neatly solve application problems where no other solution is available.

Click on Cold Welding to reach the page grouping the characteristics of the processes included, and then to be addressed to single, more specific technologies.

The second title, Creep Resistant Steels, has applicability in wide fields like power generation, refineries and chemical plants whose economic significance is enormous.

See the second page by clicking on Creep Resistant Steels to learn on current challenges in the struggle to produce and use materials capable of demanding properties at ever more difficult service conditions.

These two thin pages cannot be expected to provide all of the knowledge needed to give answers, but only to show an overview of the issues and to point out ways to obtain more deep information about the present state of the art in their different domains.

To find the pages covering any other welding related argument, see the Site Map or type your query in the search window appearing in almost every page of this website.

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


9 - Short Items

9.1 - Binary Alloy is formed by only two alloyed elements.

9.2 - Camber is the greatest deviation of the edge from a straight line and also the tendency of sheared sheet material to bend away from the sheet in the same plane.

9.3 - Dead Soft indicates the condition of minimum hardness and tensile strength produced by full annealing, referred to nonferrous alloys and some ferrous alloys.

9.4 - Electropolishing is a process in which the metal object is made the anode in an electrolytic cell where preferential dissolution at high points produces a highly reflective surface.

9.5 - Fiber Metallurgy is the powder technology of producing solid bodies from compacted fibers or chopped filaments, with or without a metal matrix. The fibers may consist of nonmetals as graphite or aluminum oxide, or of metals as tungsten or boron.

9.6 - Grain is an individual crystal in a polycrystalline material, that may or may not contain subregions of different crystal orientation.


10 - Explorations: beyond the Welder

Why Total Reporting of Genetic Results Is a Bad Idea
SA1.

What the President Can and Should Do About Climate Change
SA2.

A moral paradox
SA3.

Roads could help rather than harm the environment
CAM.

Welcome to the 'Jobless' U.S. Manufacturing Boom
Sorry! Not available any more
Fiscal Times choosed to change the link or to cancel the page.


11 - Contributions: Spot Weld Quality for Autos

At page 22, in the March 2013 issue of the Welding Journal, answering to a query from a reader, a note was published, explaining the metallographic information requirements of
AWS D8.1M:2007
Specification for Automotive Weld Quality
Resistance Spot Welding of Steel
.

Although this Spec. deals specifically with products for the automotive industry, it may clarify issues also for other general applications.

The note remarks that the methods and inspection criteria listed in the document may be used to evaluate welding equipment capability and schedules but also to characterize the weldability of a particular steel.

Furthermore, regarding Acceptance Criteria, it is noted that it is up to the customer to establish the quality requirements for every product: not all inspection methods must be applied to determine weld quality.

The author reminds that, in this document, steels are divided in four classes depending on their ultimate strength. The classification does not influence the metallographic examination requirements.

It should be known, however, for performing nondestructive surface examinations and other destructive inspections.

The article explains in detail how to prepare a metallographic specimen for destructive examination and how to measure the important features affecting spot weld quality. In particular nugget size, width and penetration, indentation, porosity and internal cracks.

Interested readers are urged to refer to the original article indicated above.

For those looking for a more general and complete treatise on Spot Welding Quality, the following publication is warmly recommended.

Evaluation and Quality Control of Resistance-Welded Joints
Document Download - File Size: 1 MB
Price $30.00 - Member Price $24.00
From: ASM Handbook, Volume 6A, Welding Fundamentals and Processes (ASM International)
Published: Nov 2011 - Pages: 486-503 (18 pages)
ASM.


12 - Testimonials

Date: 05 Mar 2013, 12:42:07 AM
Subject: RE: cracks

Hi Elia,

My apologies for my late reply. I have been on the road most of the time since I first wrote.
Thank you very much for your reply. [...]

Thank you,
Dan Militaru


On Thu 22 Mar 2013, 05:59:10 AM 2013, the following results were submitted from the "Form 5" on Welding Advisers

Name: Brett Wagner
E-mail Address: removed for security
Country: United States
Organization: Independent welder
Your Task: Joining type 304 stainless to sa387 class 1

Hi Elia,
Thanks for the quick response.[...]
The help is greatly appreciated.
Regards,
Brett


13 - Correspondence: a few Comments

13.1 - An interesting communication was received by Practical Welding Letter. It is reported again here as it was published in our Bulletin 83.

Note: Unfortunately the gain that was possible at the time of that publication is now partially lost. Nevertheless the opportunity may still be important to interested readers.

The National Center for Welding Education and Training (Weld-Ed)
was founded in 2007 through a $5 million grant from the National Science Foundation.

It is a national partnership between the welding and materials joining industry and technical colleges and universities.

It is dedicated to expanding the role of welding technicians in the industry.

Readers are urged to explore the following offer which may provide tangible benefits and gains to the professional development of Welding Educators.

Those eligible for inclusion in the circle of Participants will enjoy a mind opening experience likely to establish their Professional Advancement on a promising new base.

Weld-Ed Announces
Professional Development Workshops for Welding Educators.

Press Release:
www.bit.ly/weldedrelease

Online Registration for the five-day courses:
www.bit.ly/welded2013

Newsletter:
www.bit.ly/weldednewsletter

13.2 - A reader tried to purchase our advertised Encyclopedia Online, a rich source of Online invaluable technical information. Unfortunately he did not read attentively the instructions given in the page popping up upon performing the payment.

Had he read, he would have seen that to get download instructions he should have written us. The reason is that in the past, immediate download instructions found their way into a Google results page, enabling anyone to get the books at no cost. Therefore the new procedure was required to avoid unauthorized downloads.

Instead, suspecting a mischievous trick, the reader hastened to request refund from ClickBank, and later did not answer to my request to understand his real intentions. Too bad. Sorry for the bother.

Now a proper Announcement is printed also in the Metals Knowledge page, offering the books for purchase.

Interested readers should be assured that, if they purchase the books, they will get them in a few days.


14 - Bulletin Board

14.1 - AWS Weldmex Show, FABTECH Mexico, METALFORM Mexico.
May 7–9. Cintermex, Monterrey, Mexico.
www.aws.org/show/weldmex2013.html.

14.2 - Electric Power 2013
May 14-16, 2013. Donald E. Stephens Convention Center
Rosemont, IL - USA
http://www.electricpowerexpo.com/register-now/

14.3 - Pipeline Conference
June 4-5. Houston, Tex.
Sponsored by the American Welding Society
www.aws.org/conferences


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