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PWL#138
Practical Welding Letter No. 138
February 2015

PWL#138 - New Hybrid Induction Assisted Arc Welding, Improving Running Welding Operations, Low-Hydrogen Covered Electrodes Filler Metal, Underwater Laser Beam Cutting for Nuclear Decommissioning, Induction Heating Assisted Underwater Wet Welding, Bridge-repair (NEW) and Resources (NEW) on Bridge-repair and much more...

The Mid January 2015 Issue of Practical Welding Letter, Bulletin 104, dealing with online Resources on Bridge Repair (NEW), was not distributed by e-mail but it is available at Bulletin 104 and from the updated Welding Resources Page.

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1 - Introduction

2 - Article - Hybrid Induction Arc Welding

3 - How to do it well: Improving Running Welding Operations

4 - Low-Hydrogen Covered Electrodes Filler Metal

5 - Online Press: recent Welding related Articles

6 - Terms and Definitions Reminder

7 - Article: Underwater Laser Cutting for Nuclear Decommissioning

8 - Site Updating: Bridge-repair (NEW) and Resources (NEW) on Bridge-repair

9 - Short Items

10 - Explorations: beyond the Welder

11 - Contributions: Induction Heating Assisted Underwater Wet Welding

12 - Testimonials

13 - Correspondence: a few Comments

14 - Bulletin Board

1 - Introduction It is not quite common, in our practice, to be able to announce true innovations with the potential to leave a substantial mark in welding technology. This however is exactly what happens, to our amazement in this 138th Issue of Practical Welding Letter. Not just one, but even two different combined processes are introduced here, both based in part on auxiliary induction heating. At this early stage we have no way to assess the economic importance of both developments: but we would certainly be delighted if some of our readers would comment, sending us their view on practical aspects of this matter. So this issue opens with the description of the first innovation, Hybrid Induction Arc Welding as reported from our source. If the claimed advantages are indeed demonstrated for specific applications, it would seem that many industries should be ready to adopt this innovation to exploit its benefits. Then we urge those welding shops that run production lines established long ago, to accept the challenge to check in detail the actual practice: if nobody thought until now how to do it, quite probably these productions conceal waste and losses that can be recovered with a limited effort and a substantial gain. A reminder of why and how to approach the subject of low hydrogen covered electrodes is provided to benefit those who face sudden inexplicable weld cracking. We review the practices of decommissioning obsolete nuclear reactors, not a popular subject probably, but nonetheless important for the society. TWI obtained a contract to develop means and techniques to perform the task, and published the results of their work. The second innovation based on induction heating is an investigation involving underwater wet welding of high strength steels, undertaken to find how to improve the mechanical and metallurgical properties of the materials affected. The website new pages of this month deal with Bridge Repair: the first one reminds the heavy responsibilities affecting those in charge, and reviews the non destructive techniques used for continuous safety monitoring, detecting sudden risks and providing suitable repair procedures. The second page provides resources as a list of links to online sources of specifications and other documents issued by various authorities as means to address the required security. The other regular sections appear in this issue at their expected places. It is hoped that all will easily find those subject likely to feed their curiosity. You may wish to visit the Site Map and the Index Welding Page to find what you need. You can always use the Search function from almost every Welding Advisers page, and use the Contact Us form to send us your correspondence.

2 - Article - Hybrid Induction Arc Welding

Advancements in welding are frequently produced by synergic combinations of different processes.

This latest innovation, of which we got notice from the current issue of Advanced Materials and Processes, an ASM International publication, is described there at page 34.

From the acknowledgment notice one learns that it was a cooperative endeavor of several US National Agencies together with a few welding equipment manufacturers.

The new process is called Hybrid Induction Arc Welding (HIAW) or High Deposition Arc Welding (HiDep). It is affirmed that the hybrid approach helps to reduce or even eliminate weld distortion and greatly increases productivity.

HIAW Schematic Diagram From the quoted article of AM&P, January 2015, page 34

A movable induction coil that operates directly before the welding (GMAW) torch preheats the joint edges at or near the melting temperature. The welding arc heat melts the filler metal.

The major benefits claimed are twice to four times faster speed, relative to conventional arc welding, and substantially reduced weld distortion. Furthermore simple square butt joints are possible, even for thick parts, remarkably simplifying joint preparation.

Relative to other hybrid systems, above all the most popular that employs laser beam and GMAW, induction heating is claimed to be the best auxiliary heating method, for lower initial equipment and operating and maintenance costs.

Water cooling of the induction coil allows heat generation up to 95% efficient, with power levels of 35 to 140 kW, much higher than welding arc heat. The process was used to weld steel plates up to 19 mm (0.75") thick. In higher strength and fracture toughness structural steels, the strength, ductility, and fracture toughness of the weld and heat-affected zone (HAZ) exceeded typical code and standards requirements.

It is claimed that welding distortion is minimized due to induction heating being much more uniformly distributed. It is also claimed that by using an independently controllable heat source, significant flexibility is achieved in the amount and distribution of heat to the weld.
Nearly uniform heating of the joint helps to reduce welding distortion to a minimum.

Numerical modeling of the new process was carried out and verified with test data. Induction Heating Equipment was available from existing systems, while further development for adaptive fill, seam tracking and coil height stand-off control is ongoing.

The purpose is to integrate new systems with robotic or mechanized welding operations. Additional development will address welding of thicker steel plates and adapting the process to other materials. Hybrid induction-plasma cutting is also in development.

Interested readers are urged to seek the quoted article for complete information and references.

Without recommending nor endorsing this innovation, as a service to our interested readers, we would like to address them to the developer, to get additional information:
www.energyntech.com

3 - How to do it well: improving running welding operations

It is common knowledge in the industry that most of the running welding lines, especially the oldest ones, are not optimized. Therefore they present a wide margin of potential improvement, if the problem is dealt with properly, and if some effort is invested in clarifying the issues.

First one should establish the actual costs by recording all expenses. A simple spread sheet listing all the items should be drawn, and someone should be in charge of keeping it updated.
A good starting point might be our page on Welding Cost Estimate.

Waste and losses to be reduced are found by checking the entries in the above spread sheet against the minimum needed for each of the voices in order to perform the production assignment.

In parallel one should keep track of the time actually needed to execute all the elementary operations, to find out why delays happen and what should be done to reduce them.

It is quite probable that the costliest losses come from lost working hours, due to failure to provide smooth production sequences. Examining all recorded occurrences will provide a pattern, suggesting causes and remedies to unsatisfactory results.

Failure to produce the required quality at the first attempt may become another costly issue, to be reduced by finding the reasons for defective work and the means to achieve the goals.

Just following a given operation in detail and recording its daily performance may produce a better response from the workers, if these are associated to the struggle for improvement as a necessary condition for continuing success.

4 - Low-Hydrogen Covered Electrodes Filler Metal

A useful reminder of the reasons for selecting this type of electrodes and of the rules on how to store them before use, is the content of an article published by the January 2015 issue of the Welding Journal at page 28.

When the economics of the job at hand favor the use of manual Shielded Metal Arc Welding (SMAW), which uses covered electrodes as filler metal, one should just check if special requirements should be placed on the hydrogen content of the covering.

There may be a code requirement not subject to individual judgement. But if the base metal is a steel of improved mechanical properties, it tends to have 0.4% or higher Carbon Equivalent (see Alloy Steel Welding).

These steels have increased susceptibility to Hydrogen cracking. Therefore it is quite important to select low hydrogen covered electrodes if welding is performed by the SMAW method. See also Hydrogen Embrittlement.

Low hydrogen electrodes come with different requirements relative to the maximum acceptable level of diffusible hydrogen like H16, H8, H4 or H2 (where the number indicates the maximum value in measured milliliters of hydrogen per 100 g of weld deposit [mL/100g] ).

However it is not sufficient to specify the correct low hydrogen electrodes: once delivered in moisture proof packages, the responsibility to keep them dry rests with the welding shop. It is imperative to use heated rod ovens to store them before usage.

The quoted article reminds that AWS E7018 electrode is the most popular low-hydrogen covered electrode type presently in use, an ideal choice for all position welding, with the exception of downhill welds.

They offer smooth, quiet arc characteristics with low spatter and easy slag removal, making it the electrode preferred by welders of all skill levels.

Several welding codes prescribe the use of specific low-hydrogen electrodes for critical welds.

Readers whose responsibility requires the selection of low-hydrogen electrodes for SMAW, may profit by seeking the original article quoted above.

5 - Online Press: recent Welding related Articles

Technology Strategy Board Study Explores NDT testing
Quality

Virtual welder saves metal, money at CCC
Daily

Welding course filling an industry need
triblive

Robots Fill the Welding Gap
robotics

Guidance for mechanised GMAW of onshore pipelines
Sorry! The link was cancelled.
The title above can be searched in the Magazine's website:
https://www.pipelinesinternational.com/

Workers exposure to electromagnetic fields from welding processes
TWI1

6 - Terms and Definitions Reminder

Plasma Arc Spraying Torch is a device where an electric nontransferred arc is maintained between a tungsten electrode and a constricting nozzle, heating a pressurized inert gas to plasma state. Powder parts injected in the plasma jet are heated and propelled at high speed against a substrate, creating a dense surfacing material layer.

Quality Costs should be identified as additional time, materials and operations necessary to perform the job, and included in cost estimates.

Robotic Arc Welding Systems use gas metal arc welding or flux cored arc welding processes for performing roboting welding using an automatically controlled reprogrammable multipurpose manipulator programmable in three axes or more.

Stationary Shoe is a backing shoe that remains in a fixed position during welding.

Thermal Spray Deposit Tensile Strength is determined by separating in a tensile testing machine a thermal sprayed specimen adhesive bonded to an unsprayed specimen. The minimum strength of the adhesive must be verified to correspond to specification.

Ultrasonic Examination Calibration Test Blocks are used to perform calibration of equipment to verify the detection of the smallest unacceptable defect equivalent.

Visual Standards images or sample weldments, submitted by the fabricator and accepted by the purchaser can be used as guides to acceptable appearance.

Weld Pass Sequence is the order in which weld passes are deposited.

7 - Article: Underwater Laser Cutting for Nuclear Decommissioning

How many welding maintenance contractors are actively engaged in maintenance and decommissioning of nuclear equipment? Probably not many.

But the information relative to what is needed to do the job is open to all interested professionals who could possibly learn new techniques available to perform special tasks.

Maintenance and Decommissioning of nuclear reactors are serious endeavors, to be performed at the right time in order to avoid dangerous outcomes.

Previous systems based on Abrasive Water Jet Cutting generated disposal problems of large amounts of contaminated waste.

Accepting a contract by the UK's Nuclear Decommissioning Authority, TWI developed prototype equipment for cutting of metal pipework and concrete scabbling in environmental acceptable ways.

Laser cutting in air required complex personal protection gear (see the following TWI video:)
Hand-operated laser cutting for nuclear decommissioning
https://www.youtube.com/watch?v=E3YCACZQ72Q

A special underwater process, using a remotely operated high power fibre laser with a concentric air jet to blow away molten material drops, was developed to reduce the environmental impact.

It proved useful both for tube cutting and for removing the contaminated surface of concrete with a device for collecting debris.

For a summary of the program see:
The laser alternative
TWI2

Gas-assisted underwater laser cutting of pressure tube stubs of pressurized heavy water reactor (PHWR)
www.cat.ernet.in/newsletter/NL/nl2014/issue2/pdf/L1.pdf

Photo from Underwater Laser Cutting
http://www.twi-global.com/news-events/news/2011-05-underwater-laser-cutting/

The photographs show the cutting in progress and the resulting cut edge.

.xtend- life.com/img/d/b003.gif" border="0">

8 - Site Updating: Bridge-repair (NEW) and Resources (NEW)

Both Pages of this Month deal with welding repair of metallic construction bridges, than need continuing monitoring and maintenance to remain safe.

The first page on Bridge-repair introduces the routine examinations of the majority of existing metallic bridges done to find premonitory signs of danger requiring urgent repair to avoid catastrophies.

It reviews also continuous automatic monitoring systems designed to deliver signs of distress as soon as the sensors detect suitable signals from the construction they are built to protect.

The second page, Bulletin 104, provides links to online Resources on Bridge Maintenance and Repair, likely to display pertinent information to all interested people in search of such references.

It is hoped that both pages might be useful to all in need to know.

As usual readers already know, large amounts of information are freely available to anyone in the Welding Advisers website. One can review the Site Map and the Index Welding Page to find what one looks for.

One can also perform a search, by typing the requested terms in the box that appears in almost every page of the Welding Advisers website: the Results Page(s) will include also the pertinent articles of all issues of this Practical Welding Letter.

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

9 - Short Items

Do you know... ...how to improve electric motors? See LUT. ...to make roofs from plastic bottles? See POP. ...the mystery of superglue? See NCL. ...how to cool suspended liquid metals? See ESA. ... how to stop condensation on windows? See IST.

9.1 - Argon Oxygen Decarburization (AOD) is a secondary refining process for the controlled oxidation of carbon in a steel melt. In the AOD process, oxygen, argon, and nitrogen are injected into a molten metal bath through submerged, side-mounted tuyeres, to reduce the amount of carbon in the melt.

9.2 - Binder Metal like Cobalt is used as a binder of cemented carbides.

9.3 - Casting Shrinkage is the amount of dimensional change per unit length of the casting as it solidifies in the mold or die and cools to room temperature after removal from the mold or die.

9.4 - Defect ia a discontinuity whose size, shape, orientation, or location makes it detrimental to the useful service of the part in which it occurs and is therefore rejectable.

9.5 - Eutectic is an isothermal reversible reaction in which a liquid solution is converted into two or more intimately mixed solids on cooling, the number of solids formed being the same as the number of components in the system. Also an alloy having the composition indicated by the eutectic point on a phase diagram.

9.6 - Fissure is a small cracklike weld discontinuity with only slight separation (opening displacement) of the fracture surfaces.

10 - Explorations: beyond the Welder

Will Falling Oil Prices Kill Wind and Solar Power?
SA1

China Says Its Gender Imbalance "Most Serious" in the World
SA2

Lost Mars Lander Found in NASA Photos
SA3

Popular Cable-Stay Bridges Rise Across U.S. to Replace Crumbling Spans
SA4

Deep-Fried Graphene Spheres Could Make Good Battery Materials
SA5

11 - Contributions: Induction Heating Assisted Underwater Wet Welding

Induction Heating is described in section 2 above as an essential component of an innovative combined process recently introduced. It is amazing to find it again in a different application where it provides substantial advantages as described further on.

Tinkering with combining different processes seems to be one of the preferred ways used by innovators to come up with interesting suggestions.

Of course it will take time and further toil to sort out the real advantages of the combined process and to assess its economic potential.

But it should be interesting to follow present research in order to get a feeling of active trends, even if it may still be far the day when they mature to actual applications.

The investigation that took our attention was published at page 8-s of the Welding Research Supplement of the Welding Journal, January 2015 issue.

The abstract informs that the addition of induction heating to regular underwater wet welding could reduce the cooling rate of the joint.

Moreover the mechanical properties of the joint were improved through addition of induction heating.

Fracture morphology changed as well, showing characteristic uniform dimples belonging to ductile fracture.

The article opens with a review of current applications in offshore oil drilling structures, affirming that the demand for underwater welding processes that can produce quality wet welds at greater depths, and on a variety of materials, will continue to increase.

The authors explain the main problems facing innovators.

The high carbon equivalent, greater than 0.4%, of High Strength Low Alloy (HSLA) Steels used for offshore structures, and the considerable amounts of diffusible hydrogen, which combine to cause brittle weld microstructure and porosity, due to the high cooling rate in the aqueous environment.

As the usual means to improve the outcome rely on Post Weld Heat Treatment (PWHT) which is difficult to apply in water submerged structures, and does not provide reliable results, the authors investigated how Induction Heating could reduce the cooling rates of the joint in underwater wet welding, by extending the t8/5 (the cooling time range from 800° to 500°C).

The experimental setup placed an induction coil parallel to the weld bead. Several welds were performed after changing parameters to obtain different temperature profiles.
The influence of the coil on the arc was recorded by a high speed camera.

The distance between the axis passing at coil mid length and the flux cored wire torch position was established at 20 mm as that giving the most stable arc.

The study included detailed examination of the relevant microstructures obtained under various conditions, tensile tests and fracture morphology.

Also impact testing and bend testing were employed, and a special y-slit restraint test helped determine cracking susceptibility.

The results support the conclusion that induction heating could reduce the cooling rate of the welded joint in water and improve microstructural and mechanical properties.

Readers are urged to read the original article on
Preliminary Investigation on Real-Time Induction Heating-Assisted Underwater Wet Welding
that can be downloaded from:
http://www.aws.org/wj/supplement/WJ_2015_01_s8.pdf

12 - Testimonials

On Wed Jan 07 08:35:34 2015, the following results were submitted from the "Form 5" on welding-advisers.com:

Name: Dani Cass E-Mail Address: removed for security Country: United Kingdom
[...]
Kind Regards,

Dani

On Wed Jan 21 06:06:02 2015, the following results were submitted from the "Form 5" on welding-advisers.com:

Name: Laxman Gurav E-Mail Address: removed for security Country: India
[...]
Thanks for your support. [...]
Laxman

13 - Correspondence: a few Comments

I understand that readers are busy with their own worries and have little time and patience for activities perceived as nuisance. It is a pity, because with a little attention, readers with experience could contribute interesting pieces to enrich this publication.

They could also express their opinion on this letter, and could steer the arguments treated toward those more interesting to a larger public. Without direct exchange of ideas it is difficult to imagine which opinion readers have of my efforts.

If a few kind readers could take the time to express their comments on what they read, that would provide me the best encouragement to try even harder.

14 - Bulletin Board

14.1 - 2015 North American Iron Workers/IMPACT Labor-Management Conference
Feb.22 - 25, Rio All-Suite Hotel, 3700 W Flamingo Road - Las Vegas, NV 89103
http://www.impact-net.org/forms/meeting/MeetingFormPublic/view?id=4BFE700000426

14.2 - Association of Welding Manufacturers WEMCO 2015 Annual Meeting
Welding Industry Consolidation and Globalization
Feb. 25–27, Vinoy Renaissance Resort & Golf Club
St. Petersburg, Fla.
http://www.aws.org/w/a/wemco/annual.html

14.3 - 9th Shipbuilding Conference
April 7–8, 2015, Sheraton Virginia Beach Oceanfront Hotel Virginia Beach, VA
http://www.aws.org/conferences/2015shipbuildingConf.html

14.4 - 2015 International Brazing & Soldering Conference (IBSC 2015)
April 19–22, 2015, Hilton Long Beach Hotel, Long Beach, CA
http://www.aws.org/conferences/2015ibscConf.html

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