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PWL#059 - Welding Inspection Duties, Welder Qualification, Filler Metal Characteristics,Pipe Welding
July 01, 2008
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PWL#059 - Welding Inspection Duties, Welder Qualification, Filler Metal Characteristics, Pipe Welding Update, Thread Hole Repair, New Website Pages on Abrasive Waterjet Cutting and on Repair Welding and more...

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July 2008 - Practical Welding Letter - Issue No. 59


TABLE of CONTENTS

1 - Introduction

2 - Article - Inspection Duties

3 - How to do it well: Welder Qualification

4 - Brazing Filler Metals Characteristics

5 - Online Press: recent Welding related Articles and Video

6 - Terms and Definitions Reminder

7 - Pipe Welding Update

8 - Site Updating: Abrasive Waterjet Cutting, Repair Welding

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Thread Hole Repair

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board


1 - Introduction

This 59th Issue of PracticaL Welding Letter opens with a note on the Duties of Welding Inspectors, as this subject was raised by a few readers' Searches into our Website. Welding Management should be always alert to Inspectors' difficult choices and provide adequate assistance and support.

To answer a very specific Code interpretation question, we preferred to pass on the inquiry to a helpful engineering forum that hosts excellent professionals always willing and ready to help the general public. The answers we got are reported further down in this page.

A short note follows on certain characteristics of brazing filler metals. One is probably not aware of such properties until they interfere with successful applications. It is a subject to keep in mind.

We report on useful articles from the Welding Journal on Pipe Welding. Interested readers are referred to the source.

For the section on updates to our website we report on two new pages likely to fill specific information needs in Abrasive Waterjet Cutting and in Repair Welding.

Readers are invited to let us know which subjects they would like to see dealt with. One such argument concerned repair procedures for damaged threads on hole surfaces. We suggest a few hints to possible solutions, as a general answer valid in every case is unavailable.

The other regular columns appear at their usual place. Readers wishing to send us their comments or feedback are invited to use the form available at Contact Us. Please don't use Reply because there is no need to send back the whole newsletter.


2 - Article: Inspection Duties

AWS QC1:2007 - Standard for AWS Certification of Welding Inspectors
is the document establishing requirements and program for the American Welding Society to certify welding inspectors.

Certification is granted to individuals with the required knowledge and experience who also pass the examination and who provide a proof of visual acuity.

The examination tests the applicant’s knowledge of welding processes, welding procedures, destructive tests, terms, definitions, symbols, reports, safety, and responsibilities.

However thorough, the certification process cannot endow, by itself, the experience gained by years of practical work. Therefore management should never assign difficult inspection duties beyond the capabilities of individuals.

The question of the Inspector's duties should be reconsidered from time to time. Besides the loyalty every person owes to the employer, the integrity of the Welding Inspector is required because of the larger responsibility towards preserving the health and well being of the public.

Welding Inspectors are called to perform their job in a conscientious and impartial manner to the full extent of their moral and civic responsibility and qualification.

Inspectors may be fully aware of the financial implications connected with their approval or their rejection of any welding production, but they should stand firmly behind their own professional decisions, reached by exerting their best professional judgement.

They may need consultation with more expert inspectors than themselves, like Senior Certified Welding Inspectors (SCWI), because developing the required experience needs time, and management should be responsive to their request, a sign of honesty and thoroughness.

In any case inspectors should remain unmoved by bribes or by threats, and obtain management's backing, however hard that may be. Acceptance of substandard production should be approved by and under the responsibility of the design engineer in charge of the project.

Inspection Trends (ISSN 1523-7168) is published quarterly by the American Welding Society. This publication is visible online to AWS Members.
It is a recommended source of information for readers interested in Welding Inspection issues. See:
http://www.aws.org/itrends/2008/04/

Specific Welding Inspector's Duties are spelled out in the following Resources:

SPECIFIC REQUIREMENTS (15 pages)
The British Institute of Non-Destructive Testing
http://www.bindt.org/downloads/PCNWI.pdf

CSWIP-WI-1-91 (7 pages) RULES OF PROFESSIONAL CONDUCT (Appendix 1)
http://www.cswip.com/pdfs/8th_EDITION_REGISTRATION_VWI_WI_AND_SWI.pdf

Structural Welding Inspection - IR 17-3 - Revised 01-02-08 (3 pages)
http://www.documents.dgs.ca.gov/dsa/pubs/IR_17-3_rev01-02-08.pdf

SHOP WELDING INSPECTION (11 pages) Iowa Department of Transportation
http://www.erl.dot.state.ia.us/Oct_2007/IM/content/561.pdf

Certification of Welding Inspection Organizations -
CSA Standard W178.1-02 (2 pages).


3 - How to do it well: Welder Qualification

Q: - I have a query related to welder qualification criteria addressed as below:

Background: A welder has deposited E 7018 (F4) electrode on a 6" X Sch 40 test coupon with backing. According to QW-452.1(b), this welder is qualified to use F4 electrodes up to 14.22mm with backing. According to QW-433, this welder is also qualified to use F1, F2 & F3 with backing.

Question: If a production joint having 14.22 mm thickness with backing strip is to be deposited using E7024 (F1), E6013 (F2) & E6010 (F3) electrodes, do we have to re-qualify the above welder in all the three "F" numbers individually?

A: -

1) - 17 Jun 08 13:49
As you point out, per QW 433, F4 qualifies for F1- F4

2) - "do we have to re-qualify ...?"
17 Jun 08 14:05
No. See QW-353 in Article 2 and QW-404.15 in Article IV in the 2007 Edition of ASME B&PV Code, Section IX.

3) - 20 Jun 08 18:36
The only case in which the electrodes do NOT qualify for the lower F Number is in cases in which there is NO backing. F4 open roots qualify for F4 open roots only and F1,2,3 with backing.
See QW-433

Note: The above question from a reader was submitted by us to:
http://www.eng-tips.com/index.cfm
whose Contributors provided the above answers which are gratefully acknowledged.


4 - Brazing Filler Metals Characteristics

Brazing Filler Metal Characteristics are part of the factors that contribute to the success of brazing operations. They should therefore be addressed whenever examining specific materials for their suitability of use in definite applications.

Fluidity at brazing temperature is the property that assures running of the molten filler to spread and flow in the capillary gaps of the joint.

Viscosity is a measure of internal resistance to flow. Low viscosity promotes spread to longer distance. Brazing alloys with narrow melting range have generally lower viscosity.

Wetting ability of brazing filler relative to the base metal permits to a molten layer to adhere to the base metal surface.

Low volatility of alloying elements at brazing temperature is preferred, to avoid change of melting temperature.

The ability of the filler to alloy with the base metal is welcome, if it raises the melting temperature of the joint when reheated.

Erosion or attack of base metal at grain boundaries by brazing filler metal should be limited to acceptable levels.

While the composition of the brazing filler metal is assumed to remain constant during brazing, interactions are known to be possible as follows:

  • Alloy formation between base metal and molten brazing alloy
  • Diffusion of the base metal into the molten brazing alloy
  • Intergranular penetration of brazing alloy into base metal
  • Formation of intermetallic compounds.

This last occurrence is generally to be avoided due to the brittle nature of such compounds that impairs joint strength.

It should be remarked that brazed joint strength does not depend directly from any of the above characteristics but from complex relations among many process parameters besides the composition of the metals involved.


5 - Online Press: recent Welding related Articles and Video

Filler Metal Product Approvals
http://www.thefabricator.com/Consumables/Consumables_Article.cfm?ID=1936

From Miller Welds:
RMD™ Process Overcomes Short Circuit Mig Limitations
http://www.millerwelds.com/about/news_releases/2004_archive/articles82.html
Welding & Heating Chromium Molybdenum (P91) Pipe
http://www.millerwelds.com/education/articles/articles51.html

Advances in Pipe Welding Technique (presentation of Videos)
http://www.millerwelds.com/education/articles/article125.html

Pipe - Friction Stir Welding (Video)
http://www.msm.cam.ac.uk/phase-trans/2004/megastir.html


6 - Terms and Definitions Reminder

Drum is a cylindrical container of consumable wound welding filler metal wire ready for use in one of several welding processes.

Getter is a highly oxidizable material (like lithium, titanium, zirconium) used to remove oxygen traces and other contaminants from any protective atmosphere employed for performing heat processes likely to be degraded by their unhindered presence.

Oscillation is intentional alternating movement imparted to the tip of a consumable welding electrode or thermal spray torch to obtain favorable distribution of deposited metal.

Recycled Flux is that portion of unmelted granular flux recovered after a pass of Submerged Arc Welding and used again.

Squeeze Time is that part of a resistance spot welding cycle between initiation and application of current.

Standard Welding Procedure Specification is a commonly available document developed by AWS, specifying given parameters for performing definite welding operations without requiring qualification tests.

Tungsten Electrode is a non consumable electrode made mainly of tungsten, used for Gas Tungsten Arc Welding (GMAW) and for Plasma Arc Welding, Spraying or Cutting.

Welding Operator is a worker charged with the responsibility of conducting a semi-automatic welding operation using non manual equipment.


7 - Pipe Welding Update

The June 2008 edition of the Welding Journal dedicates a few articles to Pipe Welding.

On page 44 a New Socket Weld Repair Method is reported, describing a study aimed at validating a method of welding overlays upon fatigue cracks in socket welds, to eliminate leaks without shutting down nuclear plants.

It appears that the Case N-666 of ASME Boiler and Pressure Vessel Code permits the use of this overlay repair technology. However the only currently code-acceptable repair method consists in removing and replacing the leaking joint, with consequent downtime of entire plants.

The Electric Power Research Institute (EPRI) undertook studies to prove that the repair method could stop leaks and withstand further vibration induced fatigue cracking. Tests and related finite elements modeling studies supported the conclusion that the correctly applied above method provides an acceptable solution to leaks.

Another article starting at page 52 explains the comparative properties of Welded, Welded and Drawn, and Seamless Tubing to help in selecting the most suitable type for the application.

Purchasers are invited to understand and specify those properties (like strength or corrosion tests required) or dimensional limits that are meaningful to their further processing. Otherwise they might erroneously mention an insignificant tube processing attribute.

Critical examples of qualities and consideration of severity of leakage or failure are proposed to the readers' attention, together with additional characteristics to be taken into account.

The third article, at page 62, describes a complex operation, Mechanized Weld Buildup Repair performed on a very large tower to restore 0.5 inches of thickness lost to corrosion over several years.

Welding was performed using modified mechanized Flux Cored Arc Welding equipment operated by specially trained welders. Part of the success and of the record short time to completion of the difficult work was reached by using the services of an expert consultant who assisted the contractor in selecting the equipment and in training the workforce.

Readers interested in the above subjects are urged to seek the original articles.

We would like to remind that in our page on Pipe and Tube Welding general informaton is provided.

The reader may find some additional tips on position welding in the following References:

Supplemental Information 2 - Pipe Welding
http://deltaschooloftrades.com/supplemental_information_2.htm

Pipe Welding (from a Navy Manual).

Welders are advised that, to reach an acceptable manual welding skill there is no substitute to a good school providing training. See:

The Lincolnwelding School - Pipewelding
Welding School.

or

The Welding Skill Training Programs
http://www.welding.org/skill/programs.html


8 - Site Updating: Abrasive Waterjet Cutting, Repair Welding

Note: When you follow the links to new pages, if you want to keep the current page on your screen you should use the right click of the mouse and select "Open in a new Window".

The Pages of this Month added to our Website are:

Abrasive Water Jet Cutting

and

Repair Welding.

To be advised of new pages when they are published you can subscribe to an RSS by following instructions at the bottom of the NavBar in every page of our Website (www.welding-advisers.com) or see the WeldSite Blog at your convenience.

You can also explore the Site Map.


9 - Short Items

9.1 - Honing is a low-speed and pressure finish machining process used to produce uniform high dimensional accuracy and fine surface finish, on the inside of cylindrical surfaces. In honing, very thin layers of material are removed by simultaneously rotating and reciprocating a bonded abrasive stone pressed against the surface being honed. Used to improve the surface finish obtained by grinding.

9.2 - Leidenfrost phenomenon is the formation of a hot vapor envelope that surrounds a part being quenched from elevated temperature in a liquid medium such as water. The gaseous vapor acts as an insulator that slows down the cooling rate.

9.3 - Stretch Forming is the shaping of a metal sheet of uniform cross section by applying tension or stretch while wrapping it around a die of the required shape.

9.4 - Tint Etching is obtained by immersing metallographic specimens in specially formulated chemical etchants to produce definite different films on the various phases of specimen surface to be viewed under an optical microscope. The various phases in the alloy are then identified based on the film characteristic color. Known also as color etching.

9.5 - Vacuum Induction Melting (VIM) is a process for remelting and refining metals. The metal is melted by induction heating in a crucible held inside a vacuum chamber and it is then poured into a mold.

9.6 - Yield Strength is the stress at which a material exhibits a specified deviation from proportionality of stress and strain. It can be defined by conventional agreement as the stress level that causes an inelastic deformation (offset) of 0.2% as used for many materials, particularly metals.


10 - Explorations: beyond the Welder

Nevada first in regional concrete canoe competition
http://www.unr.edu/nvnews/detail.aspx?id=2655

Nanomaterials Show Unexpected Strength Under Stress
http://www.nist.gov/public_affairs/techbeat/tbx2008_0312_ductile.htm

Azipod® Propulsion
http://www.imionline.no/imidocs/90580P005%20Azipod%20Propulsion.pdf
ABB Azipod Propulsion (Video)
http://www.youtube.com/watch?v=skMd8Yi6th8

No-Till Farming
http://researchnews.osu.edu/archive/notill.htm


11 - Contributions: Threaded Hole Repair

Readers called our attention to their need to repair damaged or badly worn out threads inside holes.

While a common cure for this type of damage cannot be of general character, because each case depends on the materials involved and on the application, it is possible to hint to a few solutions that must be studied in depth to check their applicability to the prevailing service conditions.

Welding should not be considered as the first and foremost solution. On the contrary, it should be appreciated that usual fusion welding introduces much heat, with consequent development of considerable stresses and deformations.

Furthermore one should have complete knowledge on materials and condition, otherwise the part to be restored might be damaged beyond repair, so that welding should be avoided whenever possible.

Some investigation should be devoted to understand the causes of failure, which may be due to galvanic corrosion, to wear from long use or from vibration, and every effort should be applied to avoid the occurrence of the same failure again.

Apart from the obvious application of oversize bolts, which may fit oversize holes with new threads, one could possibly consider the application of HeliCoil which are commercially available Screw Thread Inserts. See:
http://www.emhart.com/products/helicoil.asp

In our page on Welding FAQ, under the title: EBW Repair of a rejected Casting we reported on a case that could have some similarity with the problems addressed in this section.

Depending on application and service conditions a new threaded sleeve might be fixed in place by suitable adhesive bonding instead of EBW.


12 - Testimonials

Name: John Diehl
E-mail Address: removed for security
Country: United States
Introduce Your Organization: DP
Describe Your Responsibility: Owner
Questions and Feedback : In this issue your links under aluminum welding from Miller Welds fail when clicked on. [...]

Your material is absolutely great! many thanks for what has to be a great effort.

{Note: the faulty links were corrected in http://www.welding-advisers.com/PRACTICAL_WELDING_LETTER-PracticalWeldingLetterNo58A.html}

Date: 05 Jun 2008, 09:52:39 AM
[...] Really appreciate all the great info I find on your site.

Date: 05 Jun 2008, 12:51:19 PM
Subject: RE: unsubscription

Indeed I did see the correction.
Of course I subscribed again, wouldn't miss this site for the world.


Date: 17 Jun 2008, 07:42:51 PM
Name: Randy Hough
E-mail Address: removed for security
Country: United States
Introduce Your Organization: Product Development
Describe Your Responsibility: CEO, webmaster
Questions and Feedback : Hi,
I found your great site by googleing micro welding.
As a mold maker, I love our welder! [...]


13 - Correspondence: a few Comments

13.1 - Although we already addressed the difficulty in finding equivalent Standards that could be substituted for those requested, readers continue to ask from time to time for our answers to such questions. Sorry, most of times they are not to be found.

13.2 - Reders are invited to think beforehand if their questions are complete. A question relative to a filler metal is not complete if the base metal is not specified, even if the application is vaguely referred to.

13.3 - I don't understand those readers who ask a question, probably because it is needed, but then they do not provide the details when requested. So why was the question asked in the first place?

13.4 - Basic lack of understanding surfaces from time to time, as clarified by questions which are completely out. Special cases should be checked to determine if welding is an acceptable solution to begin with.

13.5 - The appreciations expressed by several readers on the usefulness of our Website are gratefully acknowledged.


14 - Bulletin Board

14.1 - International Metallographic Society Convention (IMS 2008)
& Microscopy and Microanalysis 2008 (M&M - 2008)
August 3-7, Albuquerque, N.M., USA
http://www.asminternational.org & http://mm2008.microscopy.org

14.2 - Stainless Steel Word America 2008 Conf. & Expo
September 9-10, Houston, Texas, USA
http://www.stainless-steel-world.net


Important Announcement

See our New Page on Metals Knowledge for assembling at no cost an Encyclopedia Online, a rich collection of valuable information on Metals, from expert Internet sources.


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