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PWL#060 - Weld Silicon Steel, Nuts to a Zinc Alloy, Corrosion Resistant Alum. Brazing, Polymer Coat
July 30, 2008
We hope you will find this Letter interesting and useful.
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PWL#060 - Welding of Silicon Steel, How to Attach Nuts to a Zinc Alloy Hub, Corrosion Resistant Aluminum Brazing Filler Metals, Portable Polymer Powder Coating Technology, Testing Oil Storage Tanks Welding, New Website Pages on Welding Management and on Aluminum Finishing and more...

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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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August 2008 - Practical Welding Letter - Issue No. 60


TABLE of CONTENTS

1 - Introduction

2 - Article - Welding of Silicon Steel

3 - How to do it well: How to Attach Nuts to a Zinc Alloy Hub

4 - Corrosion Resistant Aluminum Brazing Filler Metals

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article - Portable Polymer Powder Coating Technology

8 - Site Updating: Welding Management, Aluminum Finishing

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Testing Oil Storage Tanks Welding

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board


1 - Introduction

This Month we celebrate together the 60th issue of Practical Welding Letter. Slowly but surely the audience is increasing a little each month and we are encouraged by the interest of our faithful public.

We open with an article on welding of Silicon Steel. This and other subjects were suggested to us by Searches performed in our website. If you need information but don't find it, let us know, we will try to provide it.

Attaching nuts to a zinc alloy part was a problem for one of our readers. We suggest a possible solution.

Aluminum brazing sheet used to be available as a standard item. The standard was not good enough for heat exchangers for automotive use because of severe corrosion. Alcoa came to the rescue, developing and patenting a new layered brazing sheet that protects brazing from corrosion.

In the Press Section (5) don't miss the new Guidelines... You can download the booklet at no cost.

In the Site Update we inform you on two new pages: one on Welding Management (a big question in many industries) and on Aluminum Finishing (know which treatments to specify, even if you don't do them in house). You are welcome to look at them and to send us your comments.

Testing Oil Storage Tanks Welding is a complex subject. We try to provide the needed information to those who may use it.

The usual sections can be found at their place. We hope you enjoy the reading. We will appreciate your comments. Please don't use Reply, use Contact Us instead.


2 - Article - Welding of Silicon Steel

Silicon used as a deoxidizer is present in small quantities in almost every kind of steel. As a major alloying element it is used for special purposes.

Silicon steels have from 0.5% to almost 5% silicon with low carbon, sulfur and phosphorous. They are mainly used to make laminations, punched or stamped from sheet or strip, for electrical applications.

Due to their higher permeability and lower hysteresis and eddy current losses, they are preferred to plain carbon steels for use in magnetic circuits laminations for transformers, electric motors and generators.

To hold the stack of laminations together their edges are usually welded by any one of the arc welding processes. Most used are probably Gas Metal Arc Welding (GMAW) and Gas Tungsten Arc Welding (GTAW) while Plasma Arc Welding (PAW) is preferred sometimes for small assemblies.

The laminations should be tightly pressed together before welding after removing most of the residual oil from previous operations, to prevent porosity formation.

For Gas Tungsten Arc Welding and Plasma Arc Welding filler metal is not used as the edges are fused together.

However welded, the size of weld bead should be kept as small as possible, to limit grain growth and eddy current losses within the stack.


3 - How to do it well: How to Attach Nuts to a Zinc Alloy Hub

Question: I am looking to attach some hex nuts to a handwheel hub made from ASTM/ANSI DIN1743 Z410 zinc alloy. Can this material be welded? If so, what material should the nuts be and what type of rod should be used? This is a fairly low-strength application using a 3/8" hex nut being driven with an electric screwdriver. Any help?

Answer: Try any suitable structural adhesive.
See our pages on Adhesive Bonding and on
Joining Lead Tin Zinc.


4 - Corrosion Resistant Aluminum Brazing Filler Metals

Aluminum Brazing sheets consist in a core of structural aluminum clad with a layer of lower melting brazing filler metal. They are used to make parts by stamping, drawing, bending and forming and then by mounting them in self fixturing assemblies ready for dip brazing in a bath of molten flux.

Alcoa has developed and patented multi-layered aluminum brazing sheets where intermediate cladding layers provide improved resistance to corrosion. The composite brazing filler metal sheet is intended for automotive heat exchangers.

Elements like zinc and magnesium in the claddings have specific functions. Furthermore different compositions for the intermediate claddings and the core are designed to establish a galvanic potential between the components.

For assuring corrosion protection the intermediate cladding layer is designed to become anodic to the core. See Multiple Layer Brazing Sheet.


5 - Online Press: recent Welding related Articles

From the Fabricator: See one of my recent articles:
Where is the Welding Management?
http://www.thefabricator.com/CEOs/CEOs_Article.cfm?ID=1939

and

Making Sense of Metal Cutting Technologies
http://www.thefabricator.com/LaserCutting/LaserCutting_Article.cfm?ID=1965

The effect of average powder particle size on deposition efficiency, deposit height and surface roughness in the Direct Metal Laser Deposition process
http://www.twiprofessional.com/content/spcykapr2007.html

A Guide to Troubleshooting the Most Common Self-Shielded FCAW Problems.
Troubleshooting Guide.

Online Sample Request
Volume 21, Issue 12 of Welding International
is available as an online sample issue.
http://www.informaworld.com/smpp/title~content=t778164493~db=all~tab=sample

From ASNT: see the Online
NDT Buyers Guide.

Guidelines for the Use of Personal Protective Equipment in Thermal Spraying (33 pages)
Downloadable from:
http://tss.asminternational.org/portal/site/tss/
In the right Column "What's New" Click on the second item
(Guidelines...)"View Additional Details"
In "Research Collections" Click on "Safety Guidelines"
In the new page "Safety Guidelines" Click on above title
(Guidelines for the Use of Personal Protective Equipment (PPE) in Thermal Spraying)
And that is it: Save the booklet in a suitable Folder.


6 - Terms and Definitions Reminder

Knee is a part of the supporting structure of the bottom arm of a resistance welding machine.

Metal Electrode, either consumable or not, is used to strike an arc for welding or cutting between itself and the workpiece.

Overspray is that part of sprayed deposit that is wasted on other surfaces than the workpiece.

Preheat Time is the length of time during which the preheat current is applied in resistance welding to bring the spot to preheat temperature.

Throat Depth of resistance welding machines (spot, seam or projection) represents the maximum sheet width that the machine can accommodate for performing welds.

Usability is a qualitative appreciation of the relative ease of making a sound weld by using a given welding filler metal.

Work Angle is the acute angle (less than 900) between a perpendicular line to the workpiece and a plane determined by the electrode axis and the weld axis.

Workpiece is the part or assembly that is to be welded, brazed, soldered, cut or sprayed.


7 - Article - Portable Polymer Powder Coating Technology

Disclaimer: Although the following is a commercial announcement, we feel it may interest whoever welds pipelines and needs to apply corrosion protection coatings in the field. The note hereafter is not intended to endorse, recommend or otherwise guarantee the performance or the applicability of the product, just to inform.

Powder Coatings by DuPont, manufacturers of Nap-Gard Fusion Bonded Epoxy (FBE). This DuPont powder is currently utilized to coat and repair carbon steel pipeline coated in traditional baking ovens, using one of the Xiom Guns.

http://www.xiom-corp.com/

Sorry! Link removed.


8 - Site Updating: Welding Management and Aluminum Finishing

Our Pages of the Month this time deal with two quite different subjects.

A competent and up-to-date Welding Management can be a very important asset for the Company. Unfortunately I get occasional letters from welders that are left by their management without support when they would need it most.

If welders are left without guidance and they can weld as they like, because nobody can tell them how they should weld, then there is no management, and it is quite difficult for all to keep going.

Not to mention that precious resources are wasted and important possible savings and gains are not realized, with serious consequences.

See our new page on Welding Management.

The other page on Aluminum Finishing summarizes the most useful treatments applicable to aluminum parts. The advantages are briefly outlined.

The processes may be not simple for those new to them, but fortunately many competent subcontractors are available for outsourcing the work that cannot be performed in house.

To widen our knowledge on both these subjects we would like to hear your own comments coming from your long experience: share what you know and are proud of with your fellow readers and establish meaningful relationships.

See also the Comment recently added by Paul in our page
http://www.welding-advisers.com/Welding-talk.html


9 - Short Items

9.1 - Dimple Rupture is a fractographic term describing ductile fracture occurring when microvoids form and grow together along the fracture path. The fracture surface appears dimpled when observed at high magnification, usually in a scanning electron microscope (SEM). The presence of dimples proves that the fracture is ductile.

9.2 - Exfoliation is a form of corrosion that proceeds along planes parallel to the surface, forming corrosion products that expel metal layers away from the material sheet. Most commonly found in wrought aluminum alloys.

9.3 - Hydrogen Embrittlement results from the presence of atomic hydrogen that causes a decrease in toughness and ductility of a metal. Molten metal absorbs atomic hydrogen and becomes supersaturated after solidification. Solid metal absorbs hydrogen during thermal treatments or during electroplating and a few other conditions. Reduced ductility and formation of internal cracks can follow.

9.4 - Hydrogen Storage addresses ways and means to be employed for keeping the gas available when needed, for propulsion or energy generation. Besides high pressures and cryogenics (for liquefied gas), which are considered non practical for massive use, metal hydrides and other complex liquid and solid media are strongly investigated because the subject is an active goal in the development of a hydrogen economy.

9.5 - Mechanical Alloying (MA) is a method of producing materials of exceptional characteristics by combining two or more species of greatly differing hardness through alternate cold welding and shearing of particles. The operation is carried out in high-intensity ball mills, and is the preferred method of producing oxide-dispersion-strengthened (ODS) materials. The resulting MA material is then laminated by rolling in useful sheet metal forms.

9.6 - Pitting describes the formation of small sharp cavities on a surface by corrosion, wear, or other process. It is also used to indicate localized corrosion of a metal surface in a small area, in the form of open pits.


10 - Explorations: beyond the Welder

Definition of Metric Units from the
EU Metric Directive.

Apple Pie Recipe
http://www.jsward.com/cooking/applepie.shtml

Multi-touch Screens (Video)
http://www.perceptivepixel.com/

Space Based Solar Power
http://www.spacedaily.com/news/ssp-03b.html

Filtering Tap Water?
http://www.pure-water-purifiers.com


11 - Contributions: Testing of Oil Storage Tanks Welding

A question referring to Testing of Oil Storage Tanks Welding was addressed in one of the searches run in our website. We would like to stress that in the maintenance of existing tanks, there is more than routine non destructive testing or looking for cracks and leakage.

The problem is especially severe for older and aging tanks which may be prone to fracture and loss of containment of their charge with consequent damage to the environment.

The following Standards should be known by whoever deals with Oil Storage Tanks:

ASTM E2256-03(2008)
Standard Guide for Hydraulic Integrity of New, Repaired, or Reconstructed Aboveground Storage Tank Bottoms for Petroleum Service
ASTM International, 01-May-2008, 6 pages
Click to Order

API Std 620
Design and Construction of Large, Welded, Low- Pressure Storage Tanks
Edition: 11th
American Petroleum Institute, 01-Feb-2008, 254 pages
Click to Order.

API Std 650
Welded Steel Tanks for Oil Storage
Edition: 11th
American Petroleum Institute, 01-Jun-2007, 376 pages
Click to Order.

Furthermore these Resources may be of interest to some of our readers:

Catastrophic Failure of Storage Tanks (6 pages)
Failure.

Rupture Hazards (5 pages)
http://www.epa.gov/OEM/docs/chem/tanks7.pdf

Brittle Fracture of Old Storage Tanks
http://www.ogj.com/articles/save_screen.cfm?ARTICLE_ID=18442

Major Work Activities for Tank Cleaning Operations
http://www.osha.gov/dcsp/products/topics/storagetank/work_activities.html

Aboveground Oil Storage Tank Guidance Manual
http://www.fs.uiuc.edu/sac/ec/ecsAST.cfm

Recent Developments in API Storage Tank Standards to
Improve Spill Prevention and Leak Detection/Prevention (9 pages)
http://www.epa.gov/oem/docs/oil/fss/fss02/liebpaper.pdf

Standards and Practices for Bulk Storage
http://www.dec.ny.gov/chemical/32252.html

Your Comments to this note will be appreciated.
Use Contact Us.


12 - Testimonials

On Tue Jul 01 09:56:30 2008, the following results were submitted from the "Form 5" on welding-advisers.com:
Name: Uchenna Nwanyanwu
E-mail Address: Removed for security
Country: Nigeria
Introduce Your Organization: Fabrication Company
Describe Your Responsibility: Fabrication Engineer
Questions and Feedback : ...don't really have a question. I just want to appreciate your effort all this years in touching my Engineering life. Keeping in touch like this is not always easy and trust me your articles have really encouraged many and is appreciated greatly in here.
Thanks once more


On Thu Jul 03 14:51:12 2008, the following results were submitted from the "Form 5" on welding-advisers.com:
Name: G.L. Goetzmann
E-mail Address: Removed for security
Country: United States
Introduce Your Organization: SPRUCE CREEK CONSTRUCTORS LLC
Describe Your Responsibility: Principal
Questions and Feedback : Engineer/Inspector working for BHP Billiton @ Pinto Valley Mine.
Always enjoy reading your news letter.

regards,
G.L.G.


13 - Correspondence: a few Comments

13.1 - Welding of Code regulated items is open to interpretation, maybe, but approval is finally requested from those in authority. If going an extra mile will permit procuring the approved component, this is certainly preferable rather than entering in discussions for obtaining waivers on requirements.

13.2 - Process recommendations are frequently looked for. The more details are offered the more meaningful the answer can be. Otherwise the answer may be so wide to be useless. Sometimes people ask for advice, then when invited to provide details they don't come back, they disappear.

13.3 - If the advice was inadequate or not applicable I would like to know. If it was followed with success, I would certainly like to know. So if you learned something useful just tell me, I will appreciate it.


14 - Bulletin Board

14.1 - Welding in Aircraft and Aerospace Conference Sept. 16-17, 2008 - The Broadview, Wichita, Kansas, USA http://www.aws.org/conferences
See the Conference Program (particularly interesting!) at
http://www.aws.org/w/a/conferences/aircraft/

14.2 - Canadian Manufacturing Week - 2008 Weld Expo 2008 - Metal Finishing Expo 2008 Sept. 23-25, 2008 - International Centre Mississauga, Ontario, Canada http://www.sme.org

14.3 - Thermal Spray Society Aerospace Coatings Symp.
Oct. 15-16, 2008 - Hartford, CT. USA
http://www.asminternational.org/TSSaerospace08/default.htm


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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