Connect - Selection of welding

7/29/2019 Connect - Selection of welding

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Schematic of canister repository

Issue 168 September/October 2010

Diary events

November 2010

Joint TWI/DVS Conference

Latest developments in

joining plastics in mass

production and fabrication

Tue 2

Dsseldorf

FESI Seminar

Structural integrity of

welded structures

what have we learnt?

Wed 3

Great Abington

Pressure and Process Plant

Technical Group Meeting

Nuclear new build in the

UK

Thu 4

Great Abington

TWI Annual Dinner

Tue 9London

Structural Integrity Technical

Group Meeting

Strain based fracture

assessment

Tue 23

Great Abington

December

18th IoRW Technical Seminar

Developments in railinspection

Wed 1

Great Abington

WJS Seminar

Standards for offshore

power and low carbon

energy

Wed 8

Middlesbrough

Workshops and seminars

are recognised

Continuous ProfessionalDevelopment events

T h e m a g a z i n e o f T W I

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The safe and effective storage

and disposal of high level waste

(HLW) and spent fuel (SF) arising

from nuclear power generation is a

global issue, posing major technical

challenges. When TWI was asked

by Nagra to advise on suitable

welding technologies for hot cell

encapsulation of HLW and SF,TWI was able to establish a multi-

disciplinary team to investigate the

best choice of welding processes.

Nagra is the Swiss national co-operative

for the disposal of radioactive waste and is

responsible for final disposal of all types of

radioactive waste produced in Switzerland.

TWI was selected for the project due to

significant experience with other long term

dry cask and repository storage projects

for the global nuclear industry such asthe successful development of friction stir

welded copper canisters for SKB and the

hot cell welding procedures for closure

of the canisters to be stored in Yucca

Mountain.

From the outset it was clear that the Nagra

approach to encapsulation would pose

entirely new challenges to the welding

processes. The chosen material for the

canister construction was to be carbonsteel, 190mm thickness with a minimum

lifetime of 1000 years. The timescale for

development also added challenges. With

the weld production not scheduled until

2035, all processes had to be considered.

After brainstorming, literature reviews

and preliminary investigations TWI

engineers reduced the list of potentially

viable welding processes from over thirty

to two: electron beam welding (EBW)

and narrow gap tungsten inert gas (NG-

TIG) welding. These processes were then

researched and investigated extensively

and all details of advantages, disadvantages

and the technology readiness level were

reported. This included in-depth analysis of

potential metallurgical and residual stress

issues arising from each of the potential

techniques. In addition to the welding

process technology, methods of non

destructively testing the welds in a hot

Selection of welding

processes for high level

nuclear waste encapsulation

continued on p. 2


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2

September/October 2010

C on ne ct S ep te mb er /O ct ob er 2 01 0 w w w . t w i . c o . u k e - m a i l : t w i @ t w i . c o . u k

Aker Solutions(Drilling Risers)USAOil and gas engineering

Cytec Industries UK LtdUKCoatings and composites

Fotolec Technologies LtdUKShatterproof coatingsapplication to standardlamps

ILVA SpAItalySteel production of flatproducts and weldedpipe

ITER Organisation -Magnet DivisionFranceDevelopment of magnet

technology for the ITER

programme

Johnson & Starley LtdUKManufacturer of heatingand ventilation products

Swagelining LimitedUKProvision of integratedlining systems

TATA Steel LtdIndia

Design, manufacture andsupply of plant equipmentand cranes

Woodside Energy LtdAustraliaOil and gas exploration,production anddevelopment

Welding Alloys LtdUK

Welding consumables,machines and service

New Membersof TWI

TWI is pleased to welcome the

following as Industrial Members

Aerospace Industry Panel

TWI held its 35th

Aerospace Panel Meeting

on 15 September 2010,

with attendees from the UK,

Japan, USA, Brazil, Germany,

France and Sweden.

There were TWI

presentations on microwave

curing of composites, cold

spray forming for additive

manufacture, developments

in high brightness laser

processing and EB welding

of crack sensitive

materials.

This was supplemented by

excellent presentations from

MTU, GKN Aerospace andBAE Systems.

Two Group

Sponsored

Meetings took

place the previous

day and there were

several meetings

between Industrial

Members and TWIstaff during the

week.

The next

Aerospace

Panel Meeting is

scheduled for

16 March 2011, with two

Group Sponsored Project

Meetings due to take place

on 15 March and a linearfriction welding seminar

planned for 17 March.

Details will follow in

due course and more

information can be obtained

by contacting Richard

Freeman, the Aerospace

Industry Sector Manager [email protected]

cell environment were alsoinvestigated and reported.

The results of TWIs work

were published in a Nagra

report and presented at

a meeting in Wettinngen,

Switzerland. TWIs repor t

was subsequently issued

publicly along with apreviously published material

selection repor t. This work

formed a precursor for a

multi-year study to develop

designs for carbon steel

canisters, which was issued

as an open tender in March

2010.

TWI (with Hitachi

Zosen Corporation as a

subcontractor) successfully

bid for this competitive

tender. Nagra evaluatedthe offers received on

the basis of the financial

offer, qualification and

experience of the bidder,

qualification and experience

of the experts, proposed

project work plan and an

oral presentation made to

Nagra. For more information

about this project and TWIs

services to the nuclearindustry please contact:

[email protected],

[email protected]

[email protected]

or

[email protected]

Cross-section of hot wire, narrow gap gas tunsten arc welding in180mm

P91 steel

Single pass, fully penetrating electron beam weld in 280mm thickness C-Mn

steel

continued from p.1


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3

The TSB collaborative project

Advanced Design Partitioning and

Test for System in Package electronics

(ADEPT-SiP) has now come to a close.

Partners within the project were:

TWI: lead partner, assembly,

reliability, environmental research

Filtronic Broadband:

RF communications end-user

Zarlink Semiconductor:

medical modules end-user

Zuken: design flow, partitioning,

supply chain management

AWR: RF design flow, ProcessDesign Kits (PDKs)

Leeds University: RF simulation,

models, PDKs

Mentor Graphics: thermal design

QuantumCAD: design rules, layout

Wurth Elektronik: process

architectures, manufacture

The partners formed a complete

supply chain for production of a SiP

module.

The objective of the ADEPT-

SiP project was to develop and

demonstrate a rigorous, right-first-time

design and supply chain management

methodology for novel SiP electronics.

The ADEPT-SiP module architecture

involved a high density interconnect

(HDI) printed circuit board with

integrated passive components.

One face of the HDI substrate wasallocated for RF functions and the

other for digital functions. Active

devices were mounted by wire

bonding or flip chip bonding on both

the upper and lower faces of the

module substrate.

A design kit has been successfully

produced that can select which

passives to integrate according to

cost and other priorities. Models

have been integrated into the designkit, to show RF performance of the

passive components and interconnect.

Resistors, capacitors and inductors

have been successfully printed onto a

HDI substrate and achieved close to

design values. Thermal cycling, humidity

testing and highly accelerated stress

testing has been used to test the

reliability of the embedded passives.

Demonstration medical and RF

modules were produced, showing

promising results for commercial

products.

For further information, please contact

[email protected].

ADEPT at System in Package

collaborative project draws to a

successful close

Active devices

ADEPT-

SiP moduleHDI substrate

Mother board

Encapsulation


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Techn olog y Trans fer

In Part 1 the importance of cleanliness,

particularly the removal of all

sulphur containing compounds, was

mentioned. With respect to defect

free welding of nickel and its alloys this

cannot be over-emphasised.

As well as sulphur, however, there

are several other substances that can

lead to embrittlement of the nickelalloys when they are exposed to high

temperatures. Amongst these are lead,

phosphorus, boron and bismuth.

These may be present in oils, grease,

cutting fluids, paints, marker pen

inks, temperature indicating crayons,

etc; it may not be possible to avoid

using these during fabrication so it

is essential that these are removed

if the component is to be welded,

heat treated or is to enter hightemperature service.

Fuel gases frequently contain sulphur

and it may be necessary to use radiant

gas heaters or electrical elements for

local heating or in heat treatment

furnaces.

Nickel alloys can be welded using

all the conventional arc welding

and power beam processes, the

commonest processes being TIG orMIG with pure argon, argon/hydrogen

or argon/helium mixtures as shield

gases and MMA where basic flux

coatings provide the best properties.

However, if argon/helium mixes are

used it is only when there is more

than 40% helium that any significant

benefits with respect to penetration

and improved fusion will be noticed.

Submerged arc welding is restricted towelding solid solution alloys using basic

fluxes. Matching welding consumables

are available for most of the nickel

alloys. See Job Knowledge 22 for

recommendations for a range of alloys.

Slag from MMA welding and

particularly submerged arc welding

can be difficult to remove from the

nickel alloys and often needs to be

ground between runs to remove it

completely. It is also often necessary

to grind the surface of each run

when welding with the gas shielded

processes to remove oxide scabbing,wire brushing simply polishing these

oxides.

Failure to remove slag or oxide scabs

will result not only in weld metal

inclusions but also reduce corrosion

resistance if left on exposed surfaces.

Total welding times can therefore

be substantially longer than the

equivalent joint in stainless or carbon

steel and welders need to be fullyacquainted with these differences

when converting from welding steels

to nickel alloys.

Comments regarding the

recommended weld preparations

were included in Part 1. Although

the weld preparations are similar

to those used for steel it is worth

considering the use of double V or U

type preparations at thicknesses less

than would be considered with steels.The additional cost of the preparation

is offset by savings in consumable costs

(nickel being an expensive metal) and

welding time.

The majority of nickel alloys are best

welded in the annealed or solution

treated condition, particularly if

the alloys have been cold worked.

As mentioned in Part 1, preheat

is not required except to removecondensation or if the ambient

temperature is below about 5OC

when a moderate preheat of 40-50OC

is recommended.

Interpass temperature should not be

allowed to rise above 250OC although

some alloy suppliers recommend an

interpass as low as 100OC for certain

alloys such as Alloy C276.

Remember the potential hot crack

problems if thermal crayons are

used to measure this temperature!

For most alloys heat input should be

controlled to moderate levels (say

2kJ/mm maximum) to limit grain

growth and HAZ size although for

some Alloys 718, C22, and C276 for

example, a maximum heat input of

1kJ/mm is recommended.

Conversely if too fast a travel speed

is used in an attempt to maintain a

low heat input this can result in a

narrow weld bead sensitive to centre

line cracking. Adequate testing duringwelding procedure development

should be used to optimise the range

of acceptable welding parameters.

The solid solution alloys such as Alloy

200 or 625 do not require post weld

heat treatment to maintain corrosion

resistance but may be subject to

PWHT either to reduce the risk of

stress corrosion cracking if the alloy is

to be used in caustic soda service or

in contact with fluoro-silicates or to

provide dimensional stability.

A typical stress relief treatment would

be 700OC for an hour for Alloy 200;

790OC for four hours for the higher

chromium content alloys such as Alloy

600 or 625.

The nickel-molybdenum alloys are

identified with the prefix B eg B1,

B2, etc. and are used in reducing

environments, such as hydrogen

Job Knowledge108 Welding of nickel alloys

Part 2


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Techn olog y Trans fer

5

chloride gas and sulphuric, acetic

and phosphoric acids. Alloy B2 is

the most frequently encountered

alloy and matching filler metals

are available. Unlike Alloy B1, Alloy

B2 does not form grain boundary

carbide precipitates in the weld

heataffected zone, so it may be used

in most applications in the as-welded

condition.

Alloy 400, a 70Ni-30Cu alloy, has good

corrosion resistance when exposed

to hydrofluoric acid, strong alkalinesolutions and sea water.

A matching filler metal, Alloy 190, is

available but this can become anodic

in salt solutions, leading to galvanic

corrosion and it is recommended

that one of the Ni-Cr alloy fillers such

as Alloy 600 or 625 is used in this

environment.

The age hardened alloy K-500 does

not have a matching filler metal and isgenerally welded using the Alloy 190

filler, the reduction in strength being

taken into account during the design

phase.

Precipitation hardened alloys are

best welded in the solution treated

condition; welding these alloys in the

age hardened condition is likely to

result in HAZ cracking.

The ageing process in the alloysis sufficiently sluggish that the

components can be welded in the

solution treated condition and then

aged at around 750OC without the

mechanical properties being degraded.

A solution treatment of the welded

item followed by ageing will provide

the highest tensile strength.

The sensitivity of the age hardened

alloy to cracking causes problemswhen attempts are made to repair

items, particularly when these have

been in high temperature service and

additional precipitation on the grain

boundaries has occurred.

Little can be done to overcome this

problem apart from a full solution heat

treatment but this is often not possiblewith a fully fabricated component. If

repair is to be attempted, small weld

beads and controlled low heat input

welds are recommended.

If the design permits, a low strength

filler metal, eg Alloy 200 or 600,

may be used to reduce the risk.

Buttering the faces of the repair weld

preparation, sometimes combined

with a peening operation, has been

successful.

Many of the nickel alloy filler metals

have been used for making dissimilar

metal joints with excellent results;

dilution when welding joints between

ferritic, stainless and duplex steels

being less important than when using

a type 309 stainless steel filler.

Nickel also has a coefficient of thermal

expansion between that of ferritic and

austenitic steels and therefore suffersless from thermal fatigue when high

temperature plant is thermally cycled.

Alloy 625 has been a popular choice,

the weld tensile strength matching or

exceeding that of the parent metal.

There are limitations to this approach,

and caution needs to be exercised

when selecting a suitable filler.For example, Alloy 625 has been

extensively used for welding dissimilar

joints in austenitic and duplex steels.

Use of this filler metal has resulted

in the formation of niobium rich

precipitates adjacent to the fusion line

and has been discontinued. Alloy 59 or

C22 filler metals has replaced

Alloy 625 as the filler of choice.

The moral of this is, if there is anyuncertainty, ask an exper t!

This article was written byGene Mathers

Erratum:

In the table included in Job Knowledge

107, the percentage of Fe in Alloy 825should read 28% and not 38%.


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In-service inspection

In general terms, inspection

may be applied to three

main sectors of industry:

manufacturing, fabrication and

in-service.

The manufacturing and fabrication

sectors have developed inspectionregimes specific to their products.

These products are in many ways

repetitive, predictable and inspection

procedures have been proven to be

effective when applied by competent

inspection personnel.

In-service has not been subject to

the same level of development and

scrutiny.

With ageing assets and capitalinvestment at a premium, it is

necessary to try and develop non-

invasive inspection

techniques to locate

and quantify failure

mechanisms at an

early stage in order to

manage and control the

possible interruption to

production and possibly

safety and revenue.

By identifying the defined

possible failure modes

and mechanisms in a

timely manner, it is then

possible to re-schedule

planned maintenance

shutdown of plant to

accommodate repair and

if necessary replacement

of components.

TWI recognises the

importance of this

sector of industry and

has the necessary

knowledge,

resources and

experience to assist

in the management,

control and development

of relevant and appropriate

inspection processes andprocedures.

These include:

Integrity management

Appropriate research and

development facilities

NDT Validation Centre

Appropriate and relevant

personnel training and

certication, including

Employer Specic Schemes

in accordance with

BS EN 473 and ISO 9712.

Recent developments include:

Specific training and certification in

corrosion monitoring using manual

ultrasonic techniques

Training and CSWIP certification

scheme for personnel inspecting

drillstem components (rotary tool

and drillpipe).

For more information, please contact:

[email protected]

QAJoinITregister now

www.twi.co.uk

Why is preheat used whenarc welding steel and how is itapplied?

Are duplex and superduplexsteels fit for purpose underconditions of cathodic

protection?Are there any standard tests forplastics welds?


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WJS/DVS Conference

on Joining Plastics

International Conference on the

latest developments in joining plastics

in mass production and fabrication

2 November 2010

Handwerkskammer, Dsseldorf,

GermanyThis event, which will be conducted

in English, is organised jointly by the

WJS of The Welding Institute and the

German Welding Society (DVS).

Twenty papers will be presented in

two parallel sessions. Areas covered

will include new developments in laser

welding, infrared welding, ultrasonic

welding and adhesive bonding;

welding of thermoplastic tanks and

pipes; joining of composites; testing

of welded joints; and qualification ofplastics welders.

For further information please contact

[email protected] or visit

www.dvs-ev.de/joiningplastics2010.

Advanced manufacturing and

engineering in the US Midwest and

Indiana. New opportunities for the

UK businesses.

Joint event organised by UK Trade

& Investment East and the State of

Indiana

Thursday 11 November 2010

9:00-14:00 TWI, Granta Park,Great Abington, Cambridge

The United States is the worldslargest manufacturing economy,

employing nearly 12 million Americansand producing manufacturedproducts worth up to $1.6 trillion.The US market represents 18%of theworlds manufactured goods, largely

due to Midwestern manufacturingcompanies that have a strongorientation toward knowledge-

intensive manufacturing.

The state of Indiana and the UK Trade& Investment East would like to ex-

tend an invitation to join UK

specialists and an Indiana businessdelegation and explore new

opportunities in the Midwestadvanced manufacturing andengineering sector.

For the full programme or to bookyour place at this FREE event,please call 01707398382 or [email protected]

Appointment of new TWI Directors

With the signicant growth in TWIsresearch and technology business

during recent years, we have

strengthened the executive team

to lead this key area into the future.

Separate Research and Technology

functions have therefore been

established. Dr Paul Woollin has been

appointed Director, Research to focus

on research strategy and quality to

ensure the maintenance and

enhancement of TWIs technicalreputation and Professor Aamir Khalid

has taken up the post of Director,

Technology to concentrate on

commercial technology development

to drive protable business growth.

News in brief

Over the last sixty years TWI

has been pioneering welding

and associated engineering

technologies.

TWI Services North America was

founded to extend the services

the TWI Group could offer to

engineering companies, from a local

base, within the North American

region.

The new office in Houston primarily

supplies advanced engineering

services to the oil, gas, chemical and

power generation sectors.

The services supplied range

from complex structural integrity

studies to manufacturing and

fabrication support.

If you are based in the North

American region, you can now

find out about the local news

and events via our new website:

www.twinorthamerica.com

Dont forget to add it to yourfavourites.

TWI North America


8/8

For further information on TWI, visit thewebsite at

www.twi.co.uk

8

Connect is thebi-monthly magazine

of TWIEditor:

Penny EdmundsonPhotography:Simon CondieProduction:Penny Edmundson

Copyright TWI Ltd 2010

Articles may be reprintedwith permission from

TWI. Storage in electronic

media is not permitted.

Articles in this publication

are for information only.

TWI does not accept

responsibility for the

consequences of actions

taken by others after

reading this information.

This publication is also

available in alternativeformats. Please [email protected] to

request a copy.

Published byTWI Ltd, Granta Park,

Great Abington,

Cambridge CB21 6AL, UK

Tel: +44 (0)1223 899000

Fax: +44 (0)1223 892588

E-mail: [email protected]

www.twi.co.uk

TWI Technology Centre(North East)

Tel: +44 (0)1642 216 320

Fax: +44 (0)1642 252 218

TWI Technology Centre

(Yorkshire)

Tel: +44 (0)114 269 9046

Fax: +44 (0)114 269 9781

TWI NDT Validation

Centre (Wales)

Tel: +44 (0)1639 873 100

Fax: +44 (0)1639 864 679

TWI AberdeenTel: + 44(0)1224 691222

w w w . t w i . c o . u k e - m a i l : t w i @ t w i . c o . u k

Issue 168 September/October 2010

The first CSWIP Welding Quality

Control Co-ordinator course took

place in Great Abington, UK on

23 August. At the end of this five-

day course, candidates were invited

to a cake cutting ceremony to

celebrate the official launch of this

new programme!

People holding CSWIP welding inspection

certification with several years experience

often asked us about the next logical stepon their career ladder.

In addition, the modern

inspectors roles have

changed in the last few years

and often the title of QC

Engineer is thrust upon them

or they are expected to be

equally proficient in several

disciplines.

The Welding QC Co-ordinator programme is

designed to bridge the

knowledge gap between welding inspection

and quality control.

A highly subscribed second course hasbeen held in Middlesbrough and will be

followed by a furthercourse in Great

Abington starting on 22 November.

Further courses will be available in 2011

This new scheme is proving to be very

popular so dont delay enrolling!

For further information, please

visit www.twitraining.com

call +44(0)1223 899500 or

[email protected]

CSWIP Welding QC Co-ordinator

a popular new scheme

Connect - Selection of welding

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