Issue 163 November/December 2009

The Knowledge Transfer Network (KTN) enjoyed a highly successful launch at Innovate 09 on 13 October. For the KTN the launch started with the main Stage panel session on Growth Opportunities in Energy Generation and Supply and featured David Kidney, Parliamentary Under Secretary of State, Department of Energy and Climate Change; Henri Winand, Chief Executive, Intelligent Energy Plc; David Grant, Vice-Chancellor of Cardiff University and Governing Board Member of the Technology Strategy Board and Nick Winser, CEO, National Grid.Following the panel session Dr Brian Cane, Director of the EG&S KTN, hosted a workshop on Supporting and Enabling Innovation in Energy. The session, which also featured a presentation from Trevor Raggat from the Department of Energy and Climate Change included representation

from the Technology Strategy Board, the Energy Technology Institute, the Research

Councils and The Carbon Trust, and attracted over 100 people leading to a ‘standing room only’ event.

To see Dr Cane explaining more about the KTN please go to http://www.innovate09.co.uk/video15.aspx

To find out more, please contact: enquiry@energyktn.innovateuk.org or brian.cane@twi.co.uk

Diary events

November 2009

Seminar Don’t go bust: understand the metallurgy! Thu 12 Middlesbrough

Annual Dinner Tue 24 London

December 2009Technical Group Meeting – Structural Integrity Recent developments in structural integrity methods Thu 10 Great Abington

January 2010

Joint Technical Group meeting – Offshore Oil and Gas and Welding Processes Date tbc Aberdeen

March 2010

Technical Group Meeting – Advanced Structures The Milau Viaduct Thu 25 Great Abington

April 2010

Technical Group Meeting – Welding Processes Title: tbc Thu 1 Venue: tbc

SkillWeld competition finals Tue 6 – Fri 9 Great Abington

TAGSI Seminar Structural integrity challenges to new build Tue 20 Great Abington

May 2010

International meeting 8th Friction Stir Welding Symposium Tue 18 – Thu 20 Germany

Workshops and seminars are recognised Continuous

Professional Development events

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

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Successful launch of the Energy Generation and Supply KTN

Better Connect-ed

Starting in January 2010, Connect will be published and distributed electronically, making it available from your PC, PDA or mobile phone, in the office or on the move!

In response to the results of a recent readers’ survey, Connect will be delivered to you via e-mail every two months. Already available on the TWI website at http://www.twi.co.uk/content/connect_index.html Connect will continue to be accessible here as a downloadable pdf file as well as by links to the individual articles.

To ensure that you are able to make full use of the new service, please forward all changes to your contact details, including your current e-mail address, to marketing@twi.co.uk

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November/December 2009

Connect November /December 2009 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

Aberdeen is the latest location to offer training and examination

services. This new venture has been established in order to serve the offshore industry. The facility is located at Unit 20 Spires Business Park, Mugiemoss Road about four miles south of Dyce Airport and three miles west of the railway station. With three classrooms and two practical areas, multiple on-site courses will be available as the programme develops.

From 2010 it will offer a full training programme including manual and encoded phased array ultrasonic testing, phased array data

interpretation and, potentially, the new digital radiography course.

Additional courses such as visual weld inspection, plant inspection, painting and coating, general inspection of offshore facilities, and underwater

inspection programmes will complement the NDT training, as well as bespoke training designed to meet specific client requirements.

To contact our Aberdeen office, go to www.twitraining.com

TWI in Scotland

Aero Engine Controls UK Global supplier of airframe, engine and electronic systems

AM srl Italy Shut off valves, components for gas boilers

Avure Technologies AB Sweden Manufacturer of high pressure presses

BAE Systems Land Systems UK Defence equipment and materiel

BIS O’Hare Limited UK Engineering services to UK process industries

Bridon International Ltd UK Manufacture of wire and wire rope solutions

Bytest srl Italy NDT services

C4 Carbides Ltd UK Tool manufacture

ConocoPhillips Company USA Oil and gas company

CRC-Evans Automatic Welding USA Pipeline welding

Deva Manufacturing Services Ltd UK Manufacturer of nuclear waste containers and products

Elliott Company USA Design, manufacture and service of rotating equipment

Emerson Electric – Europe UK Manufacturer of electrical products

Fluor USA Oil and gas contractors

Hi-Tech Fabrication Ltd UK Specialist fabricators serving the petrochemical industry

Holloway White Allom Ltd UK Construction

Hyder Consulting UK Ltd UK Engineering advice and design

INTECSEA (UK) Ltd UK Offshore field development and pipeline projects for the oil and gas industry

KE-TEC GmbH Germany Automotive prototype manufacturer

Marathon International Petroleum (GB) Limited – Upstream UK Oil and gas exploration and production

Nishinippon Plant Engineering and Construction Co Ltd Japan Engineering, construction and maintenance for power plant and economical facility plant

Poole Process Equipment Limited UK Manufacture of heat exchangers and pressure vessels

Power Weld Sdn Bhd Malaysia Manufacture and distribution of welding consumables

Rakon UK Limited UK Manufacturer of quartz crystals for electronics

Royal & Sun Alliance Engineering UK Third party inspection and notified body services

Sirte Oil Company Libya Production and manufacturing oil and gas

Specialised Machine Services UK Precision engineering

Thoni Alutec Sp z o o Poland Metal component manufacturer

New Members of TWITWI is pleased to welcome the following as Industrial Members.

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November/December 2009

3

TWI is a partner in a new Framework 7 project

which began recently. The project is led by Leicester University and 11 partners are involved from seven EU countries.

The work will establish the capability to design and engineer welding processes with a multi-scale, multi-physics computational modelling approach. An integrated suite of modelling software will be developed

and validated which will be able to describe the key phenomena of the welding process at all relevant length scales. Special emphasis will be given to: evolution of the solid-liquid interface, including the description of macro-scale mass flow and thermal profiles; meso-scale solid/liquid interface motion; micro/nano-scale grain boundary and morphology evolution; mechanical integrity; and service life performance of the welded product.

This project aims to deliver an accurate, predictive and cost-effective tool that will find widespread application in a range of European industries in order to provide a new capability for intelligent design of high performance welded systems and interfaces. This will enable novel markets of high economic and strategic importance to be penetrated by European companies.

The European Commission will contribute €3.55m to this €4.8m four-year project. TWI will:

• Provide other team members with up to date information on the most pressing industry needs regarding dissimilar metal welding and define relevant testing methodologies under representative in-service conditions

• Characterise dissimilar metal interface microstructures and diffusion during PWHT

both experimentally and via thermodynamic simulation

• Conduct environmental mechanical testing to validate the model generated by the modelling teams

• Disseminate and exploit the knowledge and tool package developed through the project within its Industrial Membership network

For more information, contact mcs@twi.co.uk

Modelling of Interface Evolution in Advanced Welding (MintWeld) - new Framework 7 project

Metallography of heat-affectedzones in carbon-manganesesteelsQuality assurance in weldedfabricationVisual inspection of weldedjointsIntroduction to welding processes - 1 & 2Safe working with arc weldingSafe working with gas cuttingand welding

More to become available throughout 2009

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£15 each or £90 for the full set of 7 (exc VAT and P&P)Colour, 840 x 596mm (A1), laminated

TWI Technical Posters now sold on-line

TWI Training & Examination ServicesTel: +44 (0)1223 899500

E-mail: trainexam@twi.co.ukwww.twitraining.com

Partners include:

Corus

Delft University of Technology

Ecole Polytechnique Federale de Lausanne

Institute of Welding, Poland

Norwegian University of Science and Technology

KTH Royal Institute of Technology

TWI Ltd

University College Dublin

University of Leicester

University of Oxford

Zaklad Produkcji Urzadzec Dzwigowych Frenzak Sp. Zoo

Partners attending the first project meeting at the University of Leicester

QAJoinIT

register now www.twi.co.uk

What are the problems with laser cutting of aluminium and how do I overcome them?

What is orbital welding of thermoplastics?

Can friction welding be carried out in hostile environments?

Connect November /December 2009 w w w . t w i . c o . u k e - m a i l : t w i @ t w i . c o . u k4

Technology Transfer

There are a number of different types of steels that may be referred to as ‘stainless’; previous articles have considered ferritic and precipitation hardening steels for example. It is therefore advisable to be specific and to refer to the group to which the steel belongs in order to avoid confusion. Although commonly referred to as ‘stainless steel’, the steels covered in this article should be more correctly referred to as austenitic, 18/8 or chromium-nickel stainless steels.

As with the other types of stainless steels, the austenitic stainless steels are corrosion and oxidation resistant due to the presence of chromium that forms a self-healing protective film on the surface of the steel. They also have very good toughness at extremely low temperatures so are used extensively in cryogenic applications. They can be hardened and their strength increased by cold working but not by heat treatment. They are the most easily weldable of the stainless steel family and can be welded by all welding processes, the main problems being avoidance of hot cracking and the preservation of corrosion resistance.

A convenient and commonly used shorthand identifying the individual alloy within the austenitic stainless steel group is the ASTM system. This uses a three digit number ‘3XX’ the ‘3’, identifying the steel as an austenitic stainless, and with additional letters to identify the composition and certain characteristics of the alloy eg type 304H, type 316L etc; this ASTM method will be

used in this article.

Typical compositions of some of the alloys are given in Table 1. The type 304 grade may be regarded as the archetypal austenitic stainless steel from which the other grades are derived. Changes in composition away from that of type 304 result in a change in the identification number and are highlighted in red.

The 3XX may be followed by a letter that gives more information about the specific alloy as shown in the table. ‘L’ is for a low carbon austenitic stainless steel for use in an aggressive corrosive environment ; ‘H’ for a high carbon steel with improved high temperature strength for use in creep applications; ‘N’ for a nitrogen bearing steel where a higher tensile strength than a conventional steel is required. These suffixes are used with most of the alloy designations eg type 316L, type 316LN, type 347H, where the composition has been modified from that of the base alloy.

Austenitic stainless steels are metalurgically simple alloys. They are either 100% austenite or austenite with a small amount of ferrite (see Table 1). This is not the ferrite to be found in carbon steel but a high temperature form known as delta

(δ) -ferrite. Unlike carbon and low alloy steels the austenitic stainless steels undergo no phase changes as they cool from high temperatures. They cannot therefore be quench hardened to form martensite and their mechanical properties to a great extent are unaffected by welding. Cold (hydrogen induced) cracking (Job Knowledge No. 45) is therefore not a problem and preheat is not necessary irrespective of component thickness.

Alloying elements in an austenitic stainless steel can be divided into two groups; those that promote the formation of austenite and those that favour the formation of ferrite. The main austenite formers are nickel, carbon, manganese and nitrogen; the important ferrite formers are chromium, silicon, molybdenum and niobium. By varying the amounts of these elements, the steel can be made to be fully austenitic or can be designed to contain a small amount of ferrite; the importance of this will be discussed later.

In 1949 Anton Schaeffler published a constitutional or phase diagram that illustrates the effects of composition on the microstructure. In the diagram Schaeffler assigned a factor to the various elements, the factor reflecting

Job Knowledge103 Welding of austenitic

stainless steel.

Table 1 Typical compositions of some austenitic stainless steel alloys

ASTM No.(type)

Composition wt% Microstructure

C (max) Si (max)

Mn (max)

Cr Ni Mo Others Austenite –A Ferrite - F

304 0.08 0.75 2.0 18/20 8/11 - - A+2/8%F

304L 0.035 0.75 2.0 18/20 8/11 - - A + 2/8%F

304H 0.04 – 0.10 0.75 2.0 18/20 8/11 - - A + 2/8%F

304N 0.08 0.75 2.0 18/20 8/11 - 0.1/0.16N A + 2/8%F

316 0.08 0.75 2.0 16/18 11/14 2/3 - A + 3/10%F

347 0.08 0.75 2.0 17/20 9/13 - Nb : 10xC A + 4/12%F

321 0.08 0.75 2.0 17/19 9/12 - Ti: 5xC A + 4/12%F

310 0.15 0.75 2.0 24/26 19/22 - - 100% A

309 0.08 1.0 2.0 22/24 12/15 - - A + 8/15%F

308L (generally filler metal only)

0.03 1.0 2.0 19/21 10/12 A + 4/12%F

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Technology Transfer

5

the strength of the effect on the formation of ferrite or austenite; these factors can be seen in the diagram. The elements are then combined into two groups to give chromium and nickel ‘equivalents’. These form the x and y axes of the diagram and, knowing the composition of an austenitic stainless steel, enables the proportions of the phases to be determined.

Typical positions of some of the commoner alloys are given in Fig. 1. Also superimposed on this diagram are coloured areas identifying some of the fabrication problems that may be encountered with austenitic stainless steels.

Although all the austenitic stainless steels are sensitive to hot cracking (Job Knowledge No.44), the fully austenitic steels falling within the blue area in Fig.1 such as type 310 are particularly sensitive.

The main culprits are sulphur and phosphorus. To this end, these tramp elements have been progressively reduced such that steels with less than 0.010% sulphur and phosphorus less than 0.020% are now readily available. Ideally a type 310 or type 317 alloy should have sulphur and phosphorus levels below some 0.003%. Cleanliness is also most important and thorough degreasing must be carried out immediately prior to welding.

The steels such as type 304, type 316, type 347 that fall within, or close to, the small uncoloured region in the centre of the diagram contain a small amount of delta-ferrite and, whilst not being immune to hot cracking, have improved resistance to the formation of sulphur-containing liquid films. The reasons for this are that a) ferrite can dissolve more sulphur and phosphorus than austenite so they are retained in solution rather than being available to form liquid films along the grain boundaries and b) the presence of quite a small amount of ferrite increases the grain boundary area such that any liquid films must spread over a greater area and can no longer

form a continuous liquid film. The 100% austenitic steels do not have this advantage.

One problem that has arisen with very low sulphur steels is a phenomenon known as ‘cast to cast variation’ or ‘variable penetration’. The weld pool in a low sulphur steel (<0.005%) tends to be wide with shallow penetration; a steel with sulphur over some 0.010% has a narrower, more deeply penetrating weld bead.

This is generally only a problem with the use of the fully automated TIG welding process, a manual welder being capable of coping with the variations in penetration due to the differences in sulphur content in different casts of steel. However, automated TIG welding procedures developed on a ‘high’ sulphur steel, when used to weld a low sulphur steel may result in lack of penetration type defects; the reverse situation may result in excessive penetration.

Changes to the procedure that have mitigated, but never eliminated, this problem have included slow travel speed, pulsed current, use of Ar/H2 shield gas mixtures. Other methods include specifying a minimum sulphur of, say, 0.010% or segregating the steels into batches with known penetration characteristics and developing welding procedures to suit. The A-TIG activated flux process has also been found to be of benefit.

The problems of welding the fully ferritic steels that fall into the pink area, where grain growth and embrittlement is a problem, have already been dealt with in Job Knowledge No.101.

The austenitic stainless steels falling into the yellow area will also embrittle but this is as a result of the formation of hard brittle phases called ‘sigma’

(σ) and ‘chi’ (χ). This embrittlement takes place in the temperature range of approximately 500 to 900°C. It is a sluggish process and is not a problem during welding of the austenitic stainless steels but can occur in in elevated temperature service or if the welded component is stress relieved.

Formation of these phases is promoted by high chromium and molybdenum (ferrite forming elements) so that steels such as type 310 and type 316 are particularly sensitive and may show a substantial loss of ductility after stress relief. Delta ferrite also transforms more rapidly than austenite so those alloys containing large amounts of this phase will degrade faster than austenitic steels with only a small percentage of ferrite; hence the problems with duplex and super duplex stainless steels.

When it is necessary to stress relieve a fabrication then the loss of ductility must be accounted for. In those steels containing delta-ferrite this phase should be held to a minimum, consistent with minimising the risk of hot cracking, by control of the ferrite forming elements and/or by requiring typically 2% to 5% delta ferrite.

The next Job Knowledge article will look at weld filler metal selection, some of the service problems of the austenitic stainless steels and how these may be mitigated.

This article was written by Gene Mathers.

Fig 1. Shaeffler diagram (A-austenite; M – martensite; F – ferrite)

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Connect November /December 2009 w w w . t w i . c o . u k e - m a i l : t w i @ t w i . c o . u k6

November/December 2009

A large open access innovation and technical support facility for the low carbon energy manufacturing sector is set to increase the turnover of small and medium sized regional companies by over £6m, creating and safeguarding nearly 350 jobs in the process. TWI’s Technology Centre in Middlesbrough has secured £1.67m of funding from One North East to extend the Renewable Energy Manufacturing Technology (REMTEC) initiative. The project is improving the technical capabilities and business competitiveness of North East engineering and manufacturing companies.

Manufacturers for the energy and other related sectors will be able to tap into intensive business support, with assistance ranging from access to specialist support staff to research, development and testing facilities. This will include state-of-the-art specialist techniques such as Reduced Pressure Electron Beam Welding which can halve production costs and increase production speeds by 5 to 10 times.

It will also concentrate on identified areas of opportunity including advanced fabrication of wind towers and foundations, composite

fabrication for large wind turbine blades, combustion component coatings for biomass and dual-fired plants, solar energy systems, and anti-fouling coating development.

The project is being part financed by £1m from the European Regional Development Fund 2017-13, matching the £670,000 from One North East’s Single Programme, part of Solutions for Business, the Government’s portfolio of publicly funded business support to help companies start and grow. Contributions from participating SMEs make up the remainder of the £2m initiative.

‘We will give regional businesses access to TWI’s world class and leading edge fabrication technologies to enable them to adopt new design and manufacturing methods for the low carbon energy sector, particularly in areas such as off-shore wind power,’ explained Terry O’Neill, Associate Director at TWI.

‘We have a waiting list of SMEs looking for TWI technology transfer assistance. TWI experts will help these companies with product and process reviews to identify opportunities, exploit innovation and resolve technical problems.

‘Companies using this service will benefit from sound technical assistance, effective testing and reports from the accepted world

leading authority in the area of materials joining technology – none of which would normally be readily available to them.’

With ERDF funding, the project is set to create 90 new jobs and safeguard 246 others in regional SMEs. It will also generate £6.24m in new turnover and protect existing sector turnover up to £16.4m. Beneficiaries will also have access to equipment and technologies in TWI’s centre, for use across established and emerging industry sectors.

One company already to benefit from the project is Cottam Brush, which worked with TWI to explore alternative manufacturing processes for steel wire brushes used in magnetic flux leakage pipeline inspection applications. The objective was to reduce costs and implement new production methods which could be used in product development.

For further information about the REMTEC project, call TWI on 01642 216 320.

EU funding for low carbon energy manufacturing

The REMTEC initiative helps the likes of Alan Crook from Cottam Brush to reduce costs and access new markets.

November/December 2009

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News in brief

The Richard Dolby – Rolls-Royce prize This is an award presented biennially by the WJS Younger Members Committee (YMC). The first award was made in 2007, and the presentation final for the 2009 award took place at TWI on 10th September. The cash prize of £1,000, generously donated by Rolls-Royce, is awarded to a young person with no more than five years experience after completing full time education. The award is not solely given for technical success and candidates’ commitment and enthusiasm for the subject of welding, joining and/or materials engineering form a significant part of the judging criteria.

Five presentations were made to the judging panel, which included several regional members of the

YMC, Richard Dolby and Steve Jones from Rolls-Royce. The quality of the candidates was extremely high, and the committee would like to convey their thanks to the finalists who presented on high productivity welding of titanium alloys (Simon Pike, TWI), non destructive evaluation of diffusion bonds in TiMMC discs (Katy Milne, Imperial College/RR), development of weldment fatigue procedures for the assessment of submarine nuclear vessel mounts (Matthew Massingham, Rolls-Royce) and the development of an endovascular device (Arvind Patil, Vascutek/TWI). However, after a very close final and extensive deliberation the winner was Dr Ruth Hammond of TWI for her work on the development of a high pressure hydrogen mechanical testing facility.

Ruth will receive her award from Richard Dolby and a senior figure from Rolls-Royce at the TWI Annual Dinner in London on 24th November.

TWI’s aerospace week Twenty aerospace companies from the USA, Brazil, Japan, Germany, France, The Netherlands, Norway and the UK gathered at TWI for a week of meetings dedicated to the aerospace industry. Five Group Sponsored Project (GSP) meetings and the Aerospace Industry Panel meeting were held between 15-17 September 2009.

The next Aerospace Industry Panel meeting and series of GSP meetings will take place between16-18 March 2010 divided between the TWI Yorkshire and TWI Cambridge sites. More details about these meetings will be sent out in the near future.

For many years there has been a strong relationship and technology

partnership between Brunel University and TWI. Building on this, a decision was taken to establish, in Autumn 2009, a new research centre known as the Brunel Innovation Centre (BIC) based here at TWI Cambridge.

BIC will operate as a long-term strategic partnership with the aim of developing a financially sustainable research facility, drawing on Brunel’s existing strengths, to complement and underpin the applied research and development activities of TWI. The centre will report to the steering committee consisting of the Pro-Vice Chancellor and Research Director of Brunel University and Associate

and Technical Directors of TWI Ltd. The Centre has appointed Dr Tat-Hean Gan of TWI as the Director of the Brunel Innovation Centre and also the Chair for Acoustic Waves Technologies. While acting as the Director of BIC, Tat-Hean will also act as the Head of the Business Development for the NDT Group.

The objectives of BIC are to:

• create a shared research and technology facility

• undertake joint research programmes

• secure a portfolio of research funding from external sponsors

• build a mutual understanding of future research challenges and

opportunities

• develop the next generation of technologies and engineers

For more information on the new Centre, contact tat-hean.gan@twi.co.uk

The Brunel Innovation Centre

8

Connect is the bi-monthly magazine of TWI

Editor: Penny Edmundson

Photography: Simon Condie,

Production: Penny Edmundson, John Dadson

© Copyright TWI Ltd 2009

Articles may be reprinted with 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.

Designed by: Jenny May

Printed by: Fisherprint Ltd Tel: 01733 341444

Published by: TWI Ltd, Granta Park, Great Abington, Cambridge CB21 6AL, UK Tel: +44 (0)1223 899000 Fax: +44 (0)1223 892588 E-mail: twi@twi.co.uk 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 Technology Centre (Wales) Tel: +44 (0)1639 873 100 Fax: +44 (0)1639 864 679

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Issue 163 November/December 2009

TWI has a total of seven resonance

testing machines for full-scale fatigue testing of pipe joints accommodating diameters in the range 4 to 36” (100 to 914mm).

A rotating bending moment of constant amplitude is applied at the resonant frequency of the pipe, typically 25 to 30Hz, allowing high-cycle testing of riser girth welds to be carried out rapidly. In response to requests from clients, a method of reproducing the narrow band variable amplitude loading experienced by risers in deep water, has now been developed as shown in the diagram.

New control systems and software developed in-house, allow the required loading spectrum to be reproduced reliably at the resonant frequency of the full-scale pipe sample. This unique system is now being used for extreme high-cycle variable amplitude tests, up to 200 million cycles, on 16” (406mm) diameter pipe in a current

Group Sponsored Project: Further study of fatigue damage to girth welds from low stresses in the loading spectrum.

Other components such as pipe to forging joints, threaded pipe connectors or even solid components such as drive shafts can also be accommodated. Three of the machines have now been equipped for variable amplitude loading and are available for use by TWI Member companies.

For further information, please contact structuralintegrity@twi.co.uk

Variable amplitude fatigue testing of full-scale pipe joints

TWI’s resonance fatigue testing laboratory

Typical section of variable amplitude stress sequence for a riser

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