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Issue 2 I 2007techforumThyssenKrupp

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ThyssenKrupp techforum 2 | 2007

Cover

The title picture shows a steam turbine for the high pressure (HP)

stage of a nuclear power plant after the blade assembly. This

turbine, installed in a new nuclear power plant off the west coast of

Finland, on the island of Olkiluoto, was designed and manufactured

by Siemens Power Generation. The turbine section has a tandem

compound design and consists of a double-flow high-pressure

turbine and a six-flow low-pressure (LP) turbine, solidly coupled to

a three-phase synchronous power generator. The efforts to achieve

superior steam conditions, larger turbines and advanced technology

contributes to increase the efficiency and reduce the environmental

emissions from large thermal power plants. The power generationplant of Olkiluoto outputs approximately 1,600 MW with a net effi-

ciency of about 37%.

For this project of the world largest steam turbine, the Italy based

Societ delle Fucine, a company of ThyssenKrupp Acciai Speciali

Terni, has forged and delivered a mono-block forged high-pressure

rotor shaft. Societ delle Fucine was recognized by Siemens Power

Generation as a key supplier for this kind of components and in

August 2007 was awarded the Supplier Prize Pioneer in Manu-

facturing of forged components for the world largest steam turbine.

PUBLISHER

ThyssenKrupp AG, Corporate Technology, August-Thyssen-Str. 1, 40211 Dsseldorf, Germany,

Telephone: +49 (0)211/824-36291, Fax: +49 (0)211/824-36285

ThyssenKrupp techforum appears once or twice a year in German and English. Reprints with the permission of the publisher only.

Photomechanical reproduction of individual papers is permitted. ThyssenKrupp techforum is distributed according to an address

file maintained using an automated data processing system.ISSN 1612-2771

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Foreword |3

Dear Readers,

Energy is an indispensable part of our business and daily lives. We need primary energy sources, for

example to provide heat and mobility. Today, most of our energy is generated from fossil fuels such as

coal, oil, gas as well as uranium. But reserves are finite and resource conservation is an increasingly

important issue. Global climate change is affecting all of us and means that we must rethink our energy

policies and convert and use energy more efficiently. Industry is called upon to develop innovative

solutions which reduce CO2 emissions and conserve dwindling resources in the interests of sustainable

environmental protection.

This issue of ThyssenKrupp techforum presents some of the many answers to these problems available

within our Group.

On the materials side we report about stainless steels with outstanding properties which are used infacilities to convert seawater into drinking water and for lightweight automotive construction. New nickel

alloys and low-alloy steel grades are used in the steam turbines of high-performance power plants. The

use of high-strength steels in innovative car cross members helps reduce weight and thus emissions.

Emissions can also be lowered by suitable measures in the production of white cement, in waste incin-

eration and in more energy-efficient continuous strip lines use in the production of steel sheet. In the

area of transportation, energy-efficient magnetic levitation trains such as the Transrapid help reduce

noise and pollutant emissions. Eco-friendly technologies and processes are also applied in open-pit mining

and civil engineering projects. A knowledge database has been developed to analyze the relevance for

the environment of products and waste materials. In the increasingly important area of renewable energy

sources, one contribution from ThyssenKrupp comes in the form of slewing bearings, which are used in

wind turbines. And by reference to a cupola furnace project, we show how companies can adapt their

production processes to new environmental regulations.

ThyssenKrupp is aware of its social responsibility for sustainable environmental protection through

emissions reductions and energy efficiency and acts accordingly, as we hope will be made clear by the

articles in this issue. I wish you an enjoyable read.

Yours,

Dr.-Ing. Ekkehard D. Schulz,

Chairman of the Executive Board of ThyssenKrupp AG

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4 | Contents

10 | DFI Oxyfuel process for saving energy and improving the performance

and quality of continuous strip lines

DR.-ING. HERBERT EICHELKRAUT Senior Vice President Bruckhausen site | ThyssenKrupp Steel AG, Duisburg

DIPL.-ING. HANS-JOACHIM HEILER Team Coordinator | ThyssenKrupp Steel AG, Finnentrop

DIPL.-ING. HANS PETER DOMELS Team Leader Energy and Plant Management | ThyssenKrupp Steel AG, Duisburg

WERNER HGNER Specialist Coordinator Energy and Plant Management | ThyssenKrupp Steel AG, Duisburg

The development of the Direct Flame Impingement (DFI)-Oxyfuel process in which an oxyfuel (oxygen-fuel) flame

impinges directly on the material to be heated represents a further development of furnace technology for continuous

strip lines. With assistance from the cooperation partner Linde, the process was used on a hot-dip galvanizing line for

the first time at ThyssenKrupp Steels Finnentrop plant. Right from the start it produced outstanding results in terms

of increased throughput, product quality, plant quality and energy efficiency and thus also a reduction in direct CO 2

emissions. In the meantime, this technology also is being used at an additional strip galvanizing and aluminizing facility

in the Duisburg-Bruckhausen plant.

16 | Development of a knowledge database for assessing the environmental relevance

of products, byproducts and waste materials

DR. RER. NAT. ALFONS ESSING Project Coordinator, Materials Center of Excellence | ThyssenKrupp Steel AG, Duisburg

DIPL.-INFORM. AXEL TEICHMANN Team Leader Information Technology, Materials Center of Excellence | ThyssenKrupp Steel AG, Duisburg

Many and various legislative requirements, combined with customer specifications that result from them, lead to

increased demands on the environmentally compatible manufacture, use and disposal of ThyssenKrupp Steel products.

In order to focus the large number of requirements and offer fast, unambiguous assistance with decisions, a knowledge

database for the assessment of the environmental relevance of products, byproducts, and waste materials is being

built up. All relevant product-specific information, including recycling capability, information on contents and the hazard

potential of individual materials, is being collected and made available in a fast and informative manner. Logical

coupling of the stored product data with the directives, standards and customer-specific requirements also storedmakes rapid analysis for conformity possible.

10 | 16 |

24 |

20 |

28 |

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Contents I 5

20 | SLC the innovative, low-cost lightweight construction solution for passenger car subframes

DIPL.-ING. PETER SEYFRIED Head of Lightweight Construction & Innovation Center Auto (LIZA) | ThyssenKrupp Steel AG, Dortmund

DIPL.-ING. ULF SUDOWE Head of R&D and Prototype Construction Chassis Operating Group | ThyssenKrupp Umformtechnik GmbH, Bielefeld

The innovative subframe is only half as expensive as the benchmark, an aluminum luxury class production solution and

is just 5% heavier. The SLC is a result of close collaboration between ThyssenKrupp Steel, ThyssenKrupp Umformtechnik

and ThyssenKrupp Automotive Systems. The concepts main features are its optimal mixture of materials expertise,

tooling and systems know-how.

24 | Stainless steels for seawater desalination plants

DR.-ING. GEORG UHLIG Technical Product Manager | ThyssenKrupp Nirosta GmbH, Krefeld

Seawater desalination plants can be used to produce drinking water with low chloride concentrations. Stainless steels

are an elementary component of the various process technologies in such plants. Due to growing demand for drinking

water especially in the Arabian states, but also in southern Europe seawater desalination plants represent a very

interesting area of application with increasing economic importance for stainless steels.

28 | High-performance and environment-friendly advanced high-strength stainless steels

in automotive applications

ING. ANDREA BRUNO Product Manager | ThyssenKrupp Acciai Speciali Terni SpA, Terni/Italy

Although mainly known for their corrosion-resistance properties, stainless steels, especially the new class of austenitic

N-Mn grades, also possess outstanding mechanical properties. In the transport industry, especially for the automotive

sector, it has proved possible to exploit these features, especially in the design of vehicles that are not only environ-mentally friendly but also offer high performance and thus great market appeal.

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6 | Contents

34 | Large forged shafts for power generation

DIPL.-ING. STEFANO NERI Quality Management | Societ delle Fucine S.r.l., Terni/Italy

DIPL.-ING. DANIELE MARSILI Metallurgy | Societ delle Fucine S.r.l., Terni/Italy

DR. RER. OEC. GIOVANNI SANSONE Sales Management Power Generation | Societ delle Fucine S.r.l., Terni/Italy

Continuing efforts to increase efficiency and reduce emissions from large thermal power plants have seen a corre-

sponding trend toward ever higher steam temperatures and pressures as well as advanced turbine technology. In this

context the Italian-based Societ delle Fucine (SdF), a company of ThyssenKrupp Acciai Speciali Terni, manufactured

and supplied the high-pressure (HP) rotor shaft of the biggest steam turbine in the world to Siemens AG. The power

plant, denominated Olkiluoto 3, is located in the heart of the countryside in Finland. To produce this HP rotor shaft,

SdF used a special low-alloy steel ingot of approx. 230 metric tons.

40 | Nickel alloys for tomorrows power plants

DR.-ING. JUTTA KLWER Senior Vice President Research and Development | ThyssenKrupp VDM, Werdohl

DR. RER. NAT. BODO GEHRMANN Project Manager Super Alloys, Research & Development | ThyssenKrupp VDM, Werdohl

Increases in the efficiency of fossil fuel-fired power plants are increasingly leading to higher temperatures and pressures,

thus making the use of nickel alloys essential. Nickel-based superalloys are already routinely used in gas turbines of

combined cycle power plants. With the development of the 700 C technology for coal-fired power plants, nickel alloys

are now also being used in boilers and steam turbines in the next generation of power plants. Together with power

plant operators and manufacturers of boilers for power plants, ThyssenKrupp VDM has developed alloy variant

Nicrofer 5520CoB - alloy 617B, a material that has already demonstrated its suitability for the 700 C power plant ina pilot facility.

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54 | 60 |

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Contents | 7

48 | Energy-efficient, environmentally friendly white cement production

using state-of-the-art technology

DIPL.-ING. LUIS LAGAR-GARCA Specialist Department R&D, Head of Heat and Environmental Technology | Polysius AG, Neubeckum

DR.-ING. DIETMAR SCHULZ Head of Research and Development | Polysius AG, Neubeckum

The manufacture of cement is an energy-intensive process, as the raw materials used must be burned at a temper-

ature of more than 1,400 C. The potential for lowering emissions is therefore large, particularly in the case of old

plants. The example of a white cement plant demonstrates that the application of state-of-the-art technology can

make significant reductions in emissions possible, without compromising the economic viability of the plant.

54 | Emissions reduction by means of continuous open pit mining technology

DR.-ING. VIKTOR RAAZ Project Manager R&D, Business Development dept. | ThyssenKrupp Frdertechnik GmbH, Essen

DIPL.-ING. BERGBAU ULRICH MENTGES Senior Manager Mine Planning & Sales | ThyssenKrupp Frdertechnik GmbH, Essen

A change of system in open pit mining worldwide to continuous open pit mining technology not only leads to a

reduction in running operating costs, but in particular to potential savings in CO2 emissions as well. These savings

are being studied in a current research project. In the growing market for raw materials, the combination of newly

designed, fully mobile crushing plants with innovative belt conveyor system technology in particular can achieve

reductions in CO2 emissions of the order of up to 150,000 tons per year and per installed system for raw materials

extraction, compared to conventional truck transport.

60 | Cupola project response to new MACT emission standard

WILLIAM POWELL (B.S. MET. E.) Director of Melting and Casting Technologies | ThyssenKrupp Waupaca, Inc., Waupaca, Wisconsin/USA

JEFFREY LOEFFLER (B.S. CH. E.) Environmental Coordinator | ThyssenKrupp Waupaca, Inc., Waupaca, Wisconsin/USA

Plant 1 of ThyssenKrupp Waupaca began operation of a new cupola iron melting system in January 2007. This major

project was undertaken in response to new environmental regulations directed at the United States foundry industryand offered an opportunity to concurrently increase production at the facility.

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8 | Contents

66 | CO2-free energy conversion thanks to Rothe Erde slewing bearings

DR.-ING. UWE BREUCKER Senior Manager Quality Management, Research and Development | Rothe Erde GmbH, Lippstadt

Wind technology, which converts the kinetic energy of the wind into electrical energy, is one form of CO2-free energy

conversion. Rothe Erde has accompanied this technology since the early days of its development. The supply program

for wind turbines incorporates important components such as pitch bearings, yaw bearings and rotor bearings.

Technical solutions for requirements such as minimizing false brinelling, optimizing lubricants, sealing and providing

a high degree of corrosion protection were developed in the Research and Development Center of Rothe Erde. The

dimensioning of the slewing bearings is carried out using finite element method analysis software developed inhouse.

Slewing bearings from Rothe Erde have also found application in other areas of CO2-free power generation such as

tidal flow and solar technology.

74 | Transrapid the transportation technology for environmentally friendly mobility

DR.-ING. FRIEDRICH LSER Management Board | ThyssenKrupp Transrapid GmbH | Mnchen

DR. RER. NAT. QINGHUA ZHENG Head of Systems Technology | ThyssenKrupp Transrapid GmbH | Mnchen

The implementation agreement between the Free State of Bavaria, the German railroad company Deutsche Bahn AG

and the consortium of the system and construction industries for the Transrapid project to link Munich Central Station

to Munich Airport fulfils an essential precondition to allow the advantages of Transrapid technology to also be demon-

strated in Germany. The essential factors determining the projects environmental friendliness sound and pollutantemissions and energy efficiency are explained and the new TR09 prototype vehicle is presented.

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90 |

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82 | Water-cooled moving grate for low-residue waste incinerationDIPL.-ING. WERNER AUEL Head of Combustion Technology | ThyssenKrupp Xervon Energy GmbH, Duisburg

PETER DIEKMANN Public Relations | ThyssenKrupp Services AG, Dsseldorf

The new firing concept from ThyssenKrupp Xervon Energy guarantees more efficient combustion, lower emissions, and

substantially lower operating and maintenance costs. The heart of the system is the moving grate with patented

water cooling. It ensures a higher throughput and better burnout. Its main feature, however, is that it allows fuels with

high calorific values to be burned. The energy turnover of the fuel determines the amount of cooling required by the

grate layer. The water cooling is important for the service life and the variability of the combustion air distribution.

The possibilities for integrating the heat flow that is decoupled by the grate layer into the energy process have an

effect on the plant efficiency.indung des ber

den Rostbelag ausgekoppelten Wrmestromes in den Energieprozess haben einen Einfluss auf den Anlagenwirkungsgrad.

90 | Pioneering construction processes protect the environment

DR.-ING. BERND BERGSCHNEIDER Managing Director Sales and Technology | ThyssenKrupp Bauservice GmbH, Hckelhoven

Products and services from Emunds+Staudinger, a business unit of ThyssenKrupp Bauservice GmbH, contribute to

rational, safe, and economically successful construction processes in many underground civil engineering projects

both in Germany and abroad. The company offers made-to-measure solutions for its partners in the construction

business. These include service appropriate to construction sites, consultation at a high level, comprehensive project

management, and on-time delivery of the systems selected for the respective construction measures. Together with

medium-sized and large companies, Emunds+Staudinger develops convincing concepts that pay off. The products

and processes used are tailored to the respective construction measures and ensure smooth construction processes.

The company also takes account of the stringent requirements of environmental protection for example, with the

development and application of environmentally oriented technologies and processes such as the Terra-Star recyclerfor soil preparation, mobile site road systems, or so-called deep linear shoring.

Contents | 9

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10 |


| Burner arrangement of DFI booster (top), DFI envelope flame (below)

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12 | DFI Oxyfuel process for saving energy and improving the performance and quality of continuous strip lines

necessary to undertake a very costly extension of the furnace length

and to increase firing power. Alternatively, performance improvements

were achieved at some plants by preheating the strip as necessary

using an upstream, electrically operated induction booster.

New possibilities for improving performance were opened up by the

development of the Direct Flame Impingement Oxyfuel technology and

its adaptation to the requirements of the strip coating line. Together

with the company Linde, which has already acquired experience with

this kind of heating technology at stainless steel annealing plants in

Scandinavia, ThyssenKrupp Steel has further developed the process

and applied it for the first time to the heating of flat carbon steel on

an industrial scale on hot-dip galvanizing line FBA 3, without the needto change the overall furnace length.

Energetic advantage of DFI Oxyfuel technology

The firing of heating furnaces using Oxyfuel technology has long been

known as a means of improving performance and saving energy at

the highest process temperatures. As a simple introduction to utilizing

the Oxyfuel technology, combustion air can be enriched with additional

oxygen in special firings. The advantage of this measure lies in the

reduction of the amount of nitrogen, which must also be raised to

process temperature in the firing as ballast while contributing only

minimally to the heating of the material being processed. The higher

the degree of oxygen enrichment, the less noticeable is the disad-

vantageous effect of the inert nitrogen. The heat loss that occurs due

to extraction of the hot combustion gases at the end of the heating

process is thus further minimized. The so-called thermal efficiency

a quantitative measurement for evaluating a furnace quality rises

by the same amount.

Enrichment of combustion air in firings can be extended to the use

of pure oxygen as the oxidizing agent. In the past only special appli-

cations for using pure oxygen have reached an economic basis for

the reason of high costs for this media mostly only in connection with

performance improvements for example, on the ladle heaters in the

meltshop. When natural gas is burned with pure oxygen, the resulting

combustion gas is ideally composed solely of the components water

vapor and carbon dioxide. Compared to nitrogen, both of these gases

possess excellent radiation properties for the transfer of heat. The

high flame temperatures that can be achieved have made it possible

to realize significantly improved heat transfer to the materials being

heated than would have been possible using conventional combustion

with air I Fig. 2 I.

New possibilities for the oxygen-natural gas flame are opened up

when the technology is combined with that of Direct Flame Impinge-ment, i.e. the direct application of a flame to the material to be heated

as a high-efficient method to improve heat transfer. Compared with a

conventional firing (in which heat transfer is mostly via radiation, and

convection plays only a subsidiary role), the heat transfer coefficient

as a measure of the transfer increases by a factor of about ten. As

Oxyfuel burners only generate short, compact flames in comparison

with gas-air combustion, application of the DFI Oxyfuel technology

requires that a large number of small burners be assembled together

in a single unit, the so-called burner ramp I Fig. 3 I. Multiple ramps

on the upper and lower side of the material to be heated form a so-

called booster unit. With its compact form and high power density,

this unit is relatively simple to integrate at the end of the front section

of existing continuous strip lines or alone as a complete furnace.

Use of DFI Oxyfuel on existing furnaces

The fundamentals for use of DFI Oxyfuel technology on a heating

furnace line for strip were determined from laboratory experiments

at a test facility in Sweden belonging to the company Linde. The

result was the concept for a DFI Oxyfuel booster unit only two meters

long and consisting of four burner ramps with a total of 120 Oxyfuel

flames, representing a maximum burner power of 5,000 kW. Uniform

surface treatment was achieved by broadening the individual flames

to form an envelope flame completely covering the material. Space

was also planned for two further burner ramps that could provide an

additional 2,500 kW of heating power.

This compact design made it possible to integrate the booster

as the first stage of heating directly at the furnace entry, without

extending the furnace. As a result, major rebuilding measures on the

overall line were avoided. Were the DFI Oxyfuel booster not used, it

would have been necessary to extend the existing furnace of FBA 3 in

Finnentrop by approximately 10 m in the preheater section in order

to achieve the same performance increase.

Planning showed that to install this booster on FBA 3, downtimes

could be limited to 12 days. The conventional rebuilding with extension

of the preheater furnace and the concomitant repositioning of the in-

take rollers at the start of the furnace would have required considerably

longer downtimes.

Effects on furnace operation

The operating results achieved that it has been possible to increase

furnace line capacity by 30%. This was possible because the thermal

efficiency of the booster is about 85% and thus significantly higher

than the efficiency of conventional heating technology and inductive

booster lines. The rated capacity of galvanizing line FBA 3 prior to

the rebuilding was 82 t/h. This capacity was boosted to a maximumof 109 t/h by the DFI Oxyfuel booster. The initial measurements and

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BoosterHorizontal furnace

Strip entry

Preheater furnace convective

Preheater heatedReduction furnaceCooling section

Zinc bath


DFI Oxyfuel process for saving energy and improving the performance and quality of continuous strip lines | 13

Vertical furnace

Zinc bath

Strip entry

Preheater furnace convective

Reduction furnace

Cooling section

Fig. 1 | Types of furnace for continuous strip lines

Booster

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14 | DFI Oxyfuel process for saving energy and improving the performance and quality of continuous strip lines

observations indicate that the targeted adjustment of the Oxyfuel

burners operated to the respective current strip widths resulted in more

uniform heating across the width of the strip, which led to improved

annealing properties.

The technology also represents a simple way of achieving controlled

pre-oxidation of the strip. This is required to an increasing extent in

the manufacture of specific grades in strip galvanizing plants.

Advantages for strip cleaning

Preliminary laboratory tests produced a surprising result: the DFI

Oxyfuel technology demonstrated an additional substantial advantage

when used on strip galvanizing lines. The direct contact of the flame

with the strip material purges the strip surface of unwanted foreign

materials such as emulsions, oils, lubricants and particles from the

cold-rolling process. Expectations raised by the preliminary experiments

have meanwhile been borne out in operation of FBA 3, which means

the requirements for a high-quality metal coating will be reliably met.

In addition to the improved performance, this made it possib le toeliminate conventional mechanical and electrolytic strip cleaning

from the manufacturing process and to clean the strip simply using

the DFI Oxyfuel booster.

Due to the higher efficiency, this measure for improving per-

formance simultaneously contributed to a reduction in specific fuel

gas consumption by the line. The results of operations to date (over

a period of several months) have shown that application of the DFI

Oxyfuel booster has made it possible to reduce specific fuel gas con-

sumption by 5.2%. This adds up to almost 450,000 m3 of natural gas

saved per year on a typical galvanizing line producing 36,000 t/month.

This quantity would be sufficient to heat approximately 500 modern

single-family houses for an entire year.

The reduced gas consumption also lowers carbon dioxide emis-

sions by approximately 95 t/month. Burning natural gas with pure

oxygen means that despite the high process temperatures, almost

no nitrous oxides are formed due to the absence of nitrogen. Thanks

to the booster component, the remaining NOX emissions of the over-

all line (the largest share of these originate from the gas of the

unchanged section of the furnace which still uses natural gas-aircombustion) were reduced by 20% relative to the total heat output.

Air-Fuel

1,200

1,100

1,000

900

800

700

600

500

400

300

200

100

0

Oxyfuel DFI-Oxyfuel

Fig. 2 | Improved heat transfer due to DFI Oxyfuel flames

Relativeheatfluxdensity[%]

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Outlook

In the meantime, as a result of the successful application of the

Oxyfuel booster with DFI technology, the horizontal line FBA 1 in the

Duisburg-Bruckhausen plant has also been equipped with this tech-

nology. This new system went into operation in September 2007.

The feasibility of this kind of furnace extension is currently being

determined for further continuous strip lines.

Application of a DFI Oxyfuel booster on vertical galvanizing lines,

which have a different technical layout, is also currently under consid-

eration. Here, however, integration into existing lines is more difficult

for technological reasons.

DFI Oxyfuel process for saving energy and improving the performance and quality of continuous strip lines | 15

Discussions with plant engineers regarding construction of four

modern vertical galvanizing lines for the new plant to be built in

Alabama, USA, have already begun. The more compact plant struc-

ture made possible by using DFI Oxyfuel boosters and the resulting

saving of up to 40 jet tubes and a strip cleaning unit also could offer

advantages for this project.

Further potential areas of application for the DFI Oxyfuel booster

are continuous strip annealing and heating plants, CSP (Compact

Strip Production) and continuous furnaces for heavy plate. Technical

and economic studies on these areas are also being carried out

at present.

Fig. 3 | Installation of the DFI Oxyfuel booster on FBA 3

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| Representation of the result in the knowledge database, with reference to steel mill slag

16 |

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| 17

Requirements for the knowledge database

The requirements that products must satisfy in terms of environ-

mentally compatible production, use and disposal are constantly

growing, not least due to environmental legislation. Customers have

reacted with corresponding conformity inquiries and their own,

spe-cific requirements, and they will continue to do so in the future.

A very wide range of information is relevant, depending on the

products intended uses. The creation of a knowledge database offers

a method of focusing the available comprehensive knowledge on this

topic, which is, however, spread among many employees. To this end,the following user profile has been defined:

The knowledge database is understood as a collection of knowledge

and facts, connected with a clear structuring of all information.

The implementation of user-friendly search and evaluation func-

tionalities should represent a comfortable and, most important,

effective way of making the stored knowledge available to many

authorized persons.

Logical linking of the stored product data to the directives, stand-

ards, and customer-specific requirements also stored enables fast

conformity analysis.

The focus is on the needs and requirements of customers.

Many and various legislative requirements, combined with customer specifications that result from them, leadto increased demands on the environmentally compatible manufacture, use and disposal of ThyssenKrupp

Steel products. In order to focus the large number of requirements and offer fast, unambiguous assistance

with decisions, a knowledge database for the assessment of the environmental relevance of products, by-

products, and waste materials is being built up. All relevant product-specific information, including recycling

capability, information on contents and the hazard potential of individual materials, is being collected and

made available in a fast and informative manner. Logical coupling of the stored product data with the direc-

tives, standards and customer-specific requirements also stored makes rapid analysis for conformity possible.

DR. RER. NAT. ALFONS ESSING Project Coordinator, Materials Center of Excellence | ThyssenKrupp Steel AG, Duisburg

DIPL.-INFORM. AXEL TEICHMANN Team Leader Information Technology, Materials Center of Excellence | ThyssenKrupp Steel AG, Duisburg

Development of a knowledge database forassessing the environmental relevance ofproducts, byproducts and waste materials

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18 | Development of a knowledge database for assessing the environmental relevance of products, byproducts and waste materials

and the legislative and customer-specific requirements. In addition,

the database contains the available company-internal safety data

sheets, chemical analyses on the selected products and external

information on individual materials from various toxicology and eco-logy data-bases. After preparation in the knowledge database, the

comparison of this data follows, with the focus on the assessment

output corresponding to the products area of application takes

priority, from a legal perspective and, in particular, from the customers

specific point of view. The results of the data comparison are sum-

marized in short and clear form so that all essential information on the

hazard potential of the product is included and is rapidly available to

the user I see title picture of the report I. A traffic light representation

has been selected:

Green

The product corresponds to all requirements and directives.

Yellow

Parameter contents must be declared, or the assessment cannot

be conducted due to missing product data.

Red

Limit values exceeded, thus resulting in exclusion of the selected

area of application for the product.

The safety data sheets and the chemical analyses for individual pro-

ducts can also be output from the knowledge database in tabular form,

and supplier and conformity declarations can be created. In addition to

application-related assessment of the individual products, a directive-

dependent assessment of the products is also possible I Fig. 2 I.

Outlook

In order to promote in-house application of the knowledge data-

base and to allow its cross-segment use, the second project phase,

which is currently starting, will involve the transfer of the existing

prototype knowledge database into a web-based productive system.

At the same time, the knowledge database will be completed with

respect to the materials and directives. Special attention will be paid

here to an open system architecture which, over time, will make it

possible to easily adapt to new legislative, operational, and customer-oriented requirements.

To guarantee a high degree of practical relevance, all potential

users in areas ranging from distribution of main products and sale

of byproducts to disposal operations were integrated in a project

team from the start. Acquired as external partners were the Institut frEnergie- und Umwelttechnik IUTA e.V., Duisburg, and for the program-

ming of the database structure, science + computing ag, Tbingen.

From idea to prototype

In the first project phase, the initial, abstract idea was developed

into a concrete software application. The fundamental structure of

the knowledge database was developed on the basis of the following

typical products from ThyssenKrupp Steel:

soft-alloyed steel, electrolytically galvanized, thin-film coated,

mill scale, oil-bearing and

steel mill slag.

This selection of very different products, which was agreed on by

the team, required a broad design for the database structure as early

as the initial project phase. Soft-alloyed steel sheet is manufactured

to customer order for the automotive industry. It is a steel according

to EN 10152, electrolytically galvanized and subsequently receiving

an organic thin-film coating. Mill scale sludge is produced as a by-

product of the hot rolling process. Mill scale consists of more than

60% iron oxide, and the major share of it is recycled within the plant;

i.e. it is used for steel production in the shaft furnace. Steel mill

slag is a byproduct of steel production and consists of a mixture of

various calcium silicates with a substantial component of free lime

and further metal oxides. Depending on the grain size classification,

different recycling paths are relevant for slag: fertilizer, road and

waterway construction.

The entire project team was involved in compiling the required

characteristics on the basis of customer-specific and legislative

requirements. This ensured that the essential specialist knowledge

and the requirements of the potential users were incorporated into

the database profile. I Fig. 1 I shows the fundamental procedure in

developing the profile.

Starting with the material under consideration, the knowledge data-base requires development of a profile defining the area of application

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Profile development

Application areas

Legislative requirements

Customer-specific specifications


Development of a knowledge database for assessing the environmental relevance of products, byproducts and waste materials | 19

Fig. 1 | Profile development for the knowledge database

Fig. 2 | Legislative regulations and customer-specific requirements in the knowledge database (selection)

Legislative regulations and customer-specific requirements

Federal soil protection and inherited liability law incl. information sheets

for the execution of the LABO (Federal/State soil protection working group)

TLW Technical conditions for armor stone

LAGA Federal/State waste working group

(explanatory note 20/Slags Z1, Z2)

Fertilizer ordinance

TA (technical instruction) Waste, TA Municipal waste

Landfill ordinance

End-of-life vehicle ordinance

GADSL Global Automotive Declarable Substance List (2007)

Analytical values of

the three materials

Material

Product

Byproduct

Waste material

Internal data research

Safety data sheet

Analysis data

Physical data

User query

External data resarch

Toxicological/

ecological data

Safety relevant data

Representation of the results

Database

Comparison Assessment Evaluation

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20 |

| Virtually developed prototype

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SLC a collaborative project

In previous years the steel industry has successfully developed new

steel grades with improved mechanical properties and, on this basis,

lightweight construction solutions for automotive bodies. The high-

strength steel grades used here are also suitable for use in other

vehicle areas. The SLC illustrates the potential of the new steel mate-

rials, of engineering designs making intensive use of profiles and

of innovative joining technologies, for example in chassis appli-

cations. The rear subframe was developed by ThyssenKrupp Steel,

ThyssenKrupp Umformtechnik and ThyssenKrupp Automotive Systems

in a collaborative cross-segment project. The benchmark for the

innovative steel solution is a modern subframe structure of aluminum

which is currently used in a premium-segment production vehicle.

The newly developed steel rear subframe I Fig. 1 I is around 40%

more economical than the benchmark assembly and offers the same

performance in terms of rigidity and durability with only a small

weight increase.

Ambitious benchmark competitive steel solution

The series-production rear subframe selected as the reference struc-

ture may be viewed as an exceptionally demanding benchmark. The

assembly incorporates a series of cast aluminum parts whose im-

plementation in stamped steel components places extremely high

demands on component design and forming technology. At the sametime, the steel structure must demonstrate equivalent corrosion pro-

tection to that of aluminum. The use of thinner sheets of high-strength

steel represents a special challenge here. In order to fulfill the com-

plex connection requirements to the control arms, supports etc.

without negatively impacting the weight of the assembly, new man-

ufacturing methods had to be applied both in the production of the

components and in their assembly. Due to the projects requirement

that the result be suitable for production use, the virtually developed

model was tested in practice by means of a small series of prototypes

I Fig. 2 I, which were finally subjected to a dynamic component test.

| 21

SLC the innovative, low-costlightweight construction solution forpassenger car subframes

The innovative subframe is only half as expensive as the benchmark, an aluminum luxury class production

solution and is just 5% heavier. The SLC is a result of close collaboration between ThyssenKrupp Steel,

ThyssenKrupp Umformtechnik and ThyssenKrupp Automotive Systems. The concepts main features are

its optimal mixture of materials expertise, tooling and systems know-how.

DIPL.-ING. PETER SEYFRIED Head of Lightweight Construction & Innovation Center Auto (LIZA) | ThyssenKrupp Steel AG, Dortmund

DIPL.-ING. ULF SUDOWE Head of R&D and Prototype Construction Chassis Operating Group | ThyssenKrupp Umformtechnik GmbH, Bielefeld

Fig. 1 | Tailor-made solution for a complex installation situation: SLC

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22 |


Holistic development

The interdisciplinary composition of the project team provided an

optimal combination of materials, product and process know-how

throughout the entire project. The aim of the project was to offer

automakers a solution suitable for production use. During the vali-

dation of the SLC concept, the finished rear subframes are tested

for operational stability according to industry standards on a multi-

axis simulation test rig. Strain gauges on the components to be

tested ensure that the actual measured strains on the component

under test are fed back into the component simulation. This makes

further optimization possible and allows knowledge to be derived forfuture development.

Fig. 3 | Flangeless lightweight construction profiles for half-shell technology:

Even the most complex geometries can be reliably produced with the high-strength

complex-phase steel CP-W 800.

Fig. 2 | Reliable weldability was demonstrated with real prototype components.

The hot-rolled complex-phase steel CP-W 800 is one of the mate-

rials used in the lightweight construction steel chassis. It has a yield

strength of 680 MPa, making it significantly stronger than the steels

currently used for most chassis production, which have yield strengths

between 355 and 420 MPa. It thus makes it possible to realize designs

with correspondingly thinner walls while, however, also presenting

higher demands on the forming technology capabilities of its pro-

cessors. Corresponding experience is required, particularly in the

design of the tooling methods and selection of the correct coating

for the tools. CP-W 800 offers advantages with respect to corrosion

protection, in particular du to its microstructure and resulting insen-

sitivity to heat input. For example, it is possible to achieve the corro-sion resistance required by means of batch galvanizing. Depending

on the stresses (stone impacts and corrosion) to which the beam

is subjected, the high-strength complex-phase steels can be coated

prior to use or post-treated by means of the commonly used pro-

cesses with no significant loss of strength.

Technical highlights

With the SLC, the project team has succeeded in extending the

area of application of high-strength steel grades to more complex

geometries that require greater forming technology capabilities.

The CP-W 800 is used for the side members I Fig. 3 I and the rear

cross member of the rear subframe, which are manufactured from

sheets of less than 2 mm thickness I Fig. 4 I. The materials previously

used for this application would require a sheet thickness of approxi-

mately 2.5 mm.

Additional weight saving is achieved by using ThyssenKrupp

tailored blanks, made from individual CP-W 800 blanks of different

thicknesses. Furthermore, the joining technology used also has an

effect on the component weight, which consists of two half shells

welded together using a square butt joint. The process does not

require the conventional welding flanges which can account for up

to 5% of the component weight. Moreover, components welded

without a flange make much more effective use of the available

packaging space.

Design flexibility with respect to costs and weight

Thanks to the flexible use of tailored blanks, it has also been possible

to represent a modular solution within the specified geometry. This

made it possible to create stress-matched variants by replacing the

side members or cross members designed as tailored blanks with

stamped components featuring the same geometry but with constant

sheet thickness. This approach also makes it possible to minimizeweight or to achieve a balanced mixture of cost and weight advan-

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tages, depending on customer preference. Expressed in numbers, this

means cost can be reduced by approximately 40% relative to the

benchmark with only a minimal weight increase of 5%. For a cost-

driven variant, a design with a cost reduction of approximately 50%

can be achieved for an acceptable increase in weight of 10%.

CO2 balance

According to a current study carried out on behalf of the IISI (Inter-

national Iron and Steel Institute) by the University of California, Santa

Barbara (UCSB), which is recognized in the field of international

environmental protection, the following conclusions can be drawn:

Based on a comparative life cycle assessment and taking intoaccount the currently known fundamental data, it was determined

that compared with body concepts using high-strength steels such

as ULSAB-AVC, aluminum body concepts do not make any overall

savings in greenhouse gas emissions. Considered over the complete

product lifecycle within the normal vehicle service life, the greenhouse

gas emissions are on a roughly comparable level. This is mainly due

to the production phase of the aluminum material, which causes

comparatively high greenhouse gas emissions prior to the metals

use phase. It is almost impossible to offset these production-related

SLC the innovative, low-cost lightweight construction solution for passenger car subframes | 23

PAS 460 t = 1.5 mm

PAS 460 t = 2.15 mm

PAS 460 t = 2.15 mm

CP-K t = 1.3 mm

CP-W 800 t = 1.5 mm

CP-W 800 t = 1.5 mm

CP-W 800 t = 1 .8 mm

CP-W 800 t = 1.5 mm

Fig. 4 | Low weight thanks to the use of thickness-optimized tailored blanks and the high-strength complex-phase steel CP-W 800

emissions by means of savings from supposed weight advantages

of the aluminum solution during its use phase.

Taking this into account in the chassis scenario means that the

slight weight advantage of the aluminum structure is offset by the

increased CO2 emissions during aluminum production.

Outlook

ThyssenKrupp Steel is currently developing innovative zinc-magnesium

coatings that can be used to specifically improve the corrosion pro-

tection concept for the SLC. This can, for example, lead to further,

significant cost advantages through the use of ZMg precoated sheet

in combination with a post-treatment of the welding seams and sub-sequent coating by means of cathodic dip painting.

A further element in the reduction of weight and costs is provided

by high-strength steel grades with high formability, which allow more

complex geometries and an associated increase in functional integra-

tion. The integrated approach to future developments also incorporates

further development of the joining processes. Cold joining processes

(e.g. riveting, adhesive bonding) and hot joining processes alike offer

significant potential in this area.

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24 |

| Heat exchanger tube bundle for seawater desalination plants

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| 25

Stainless steels for seawater

desalination plants

Seawater desalination plants can be used to produce drinking water with low chloride concentrations.

Stainless steels are an elementary component of the various process technologies in such plants.

Due to growing demand for drinking water especially in the Arabian states, but also in southern

Europe seawater desalination plants represent a very interesting area of application with increasing

economic importance for stainless steels.

DR.-ING. GEORG UHLIG Technical Product Manager | ThyssenKrupp Nirosta GmbH, Krefeld

Global drinking water requirements

In many countries in the Middle East, in North Africa and in certain

regions of southern Europe, supplying drinking water to the popula-

tions represents one of the most important tasks. There is increased

demand, especially in countries with strong population growth, where

natural sources of drinking water are no longer always adequate.

Furthermore, available drinking water reserves may shrink due to

climatic changes, causing the water table to fall or surface water

used to date, for example in coastal regions, to become brackish.

The limited availability of natural drinking water reserves therefore

makes it necessary in many countries to produce additional quanti-

ties. Seawater desalination is one possible process that can be used.

Processes for seawater desalination

Using seawater desalination plants, it is possible to reduce the chloride

content of seawater I Fig. 1 I to a low concentration corresponding to

the respective national regulations and guidelines for drinking water.

In Germany, for example, the maximum permitted chloride concen-

tration in drinking water is 250 mg/l. In practice, the normal chlorideconcentrations in tap water are usually well under 100 mg/l.

In terms of process technology, there are three different possi-

bilities available in principle for the desalination of seawater:

the MSF (Multi Stage Flash) process,

the MED (Multiple Effect Distillation) process and

the RO (Reverse Osmosis) process

The first two processes are based on the evaporation of seawater

and extraction of the desalinated condensate, while the reverse

osmosis process involves using high pressure to force the seawater

through a semi-permeable membrane I Fig. 2 I. This membrane is

permeable to the water but retains the salt component.

Salt contents of seawater

normal: 35,000 ppm

locally from: 7,000 ppm (Baltic Sea)

up to: 50,000 ppm (Persian Gulf)

Brackish water: 1,000 -10,000 ppm

Fig. 1 | Salt contents of seawater

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26 | Stainless steels for seawater desalination plants

Due to the growing demand for drinking water, a great deal of new

capacity has been created within the last ten years. Worldwide,

around 25 new plants using the thermal processes MSF and MED

alone are being built per year. At the same time, plant capacity is

continually being increased. About 68% of the seawater desalination

plants in operation today function using the MSF process, with approx-

imately 14% using the MED technology. The remaining 18% work

on the reverse osmosis principle (RO process). The MED and RO

processes in particular have been showing disproportionately high

growth rates recently.

Corrosion-resistant materials are elementary components of

the plants, particularly of those using the thermal processes. The

factors determining selection of materials for such plants are the local

chloride load and the effective temperatures. The MSF process

essentially consists of a number of evaporation chambers arranged

one behind the other, in which the seawater is evaporated at succes-

sively lower temperatures and pressures. The evaporated seawater

subsequently condenses on bundles of tubes arranged in the steam

space of the chambers. The tubes are cooled from inside by seawa-

ter that is heated in the process and subsequently fed to the evapo-

ration chambers I Fig. 3 I.

In principle, various materials are suitable for the evaporationchambers. In practice, carbon steel lined with the material 1.4404

or epoxy coated is normally used. Recently, the use of stainless duplex

steels (1.4462) for this purpose has been increasing. The tube bundles

in the evaporation chambers are subject to extreme corrosive loads,

especially in the first evaporation stages I see title picture of the

report I. The temperature in the first stage can be as high as 120 C

at pressures of around 1.3 bar. Copper-based and titanium alloys

are mostly used for these tube bundles. The base plates of the tube

bundles, in contrast, consist mostly of the material 1.4404. Stainless

steels such as 1.4404 and 1.4539 are also used for additional plant

components including pumps, containers and pipework.

The corrosion requirements presented by the MED process are

generally lower than those of the MSF process, due to the different

process control. In this process, which takes place in several stages,

the seawater is sprayed onto bundles of tubes and vaporized. The

vapor is then led into the tubes, where it condenses as desalinated

water. In this process technology, the evaporation chambers and tanks

for the distillate are usually made from the stainless steels 1.4404

or 1.4462. At a maximum of 70 C, the thermal stress to which the

tube bundles are subjected is lower in the MED process than in the

MSF process. For this reason, highly alloyed stainless steels of type

1.4565 are among the materials suitable for manufacturing bundles

of tubes with minimal wall thicknesses I Fig. 4 I. Alternative materialsfor these plant components would be titanium or copper-based alloys.

Fig. 2 | Principles of seawater desalination

Sea water

Flowdirection

Desalinated

water

Cooling

Heating

Condensate

Sea water

Water vapor

Fig. 3 | Principle of the MSF process

Evaporatorchamber

Desalinatedcondensate

Sea water

Heat exchangertube bundle

Water vapor

Thermal process Membrane process

Membrane

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Stainless steels for seawater desalination plants | 27

Fig. 4 | Heat exchanger tube bundle made of NIROSTA 4565

Furthermore, stainless steels of the types 1.4404 and 1.4462 are

also used in the MED process for other applications, including trans-

portation and storage of the raw water and the distillate.

Modern plants using the MED process have capacities of approx-

imately 250,000 m3/d. This type of plant requires several thousand

tons of stainless steel in the form of hot and cold rolled sheet, strip

and tubes I Figs 5 and 6 I.

Summary

In line with the forecast for future demand for drinking water, seawater

desalination plants offer a very interesting area of application for

stainless steels, one that will continue to grow in importance during

the coming years.

Fig. 5 | Demi Water Plant for desalination of brackish water in Rotterdam, Netherlands Fig. 6 | Seawater desalination plant, Al Hidd, Bahrain

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28 |


| Spaceframe body of the Nido (Nest) prototype from Pininfarina a lightweight structure of austenitic stainless steel

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| 29

High-performance andenvironment-friendly advancedhigh-strength stainless steelsin automotive applications

Although mainly known for their corrosion-resistance properties, stainless

steels, especially the new class of austenitic N-Mn grades, also possess

outstanding mechanical properties. In the transport industry, especially

for the automotive sector, it has proved possible to exploit these features,

especially in the design of vehicles that are not only environmentally friendly

but also offer high performance and thus great market appeal.

ING. ANDREA BRUNO Product Manager | ThyssenKrupp Acciai Speciali Terni SpA, Terni/Italy


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Tensile strength Rm [MPa]

60

50

40

30

20

10

0

Conventional steels STR18

DPRA

CP

MS-WFB-W

200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300 1,400 1,500

ElongationA

80

[%]

FB-W: Ferrite-bainite-phase steels (hot rolled)

DP: Dual-phase-steels

RA: Retained-austenite steels (TRIP)

CP: Complex-phase steels

MS-W: Martensitic-phase steel (hot rolled)

Stainless steels

Since their invention, stainless steels defined as any Fe-Cr alloy

containing at least 10.5% chromium have been well known for their

specific properties of resistance to oxidation and high temperatures.

Chromium forms a compact protective oxide layer (Cr2O3) which

adheres firmly to the metal surface and prevents further oxidation of

the metal substrate (similarly to what happens naturally with titanium

and, to a lesser extent, aluminum alloys), thus protecting the steel.

The aforementioned properties make this class of steels suitable for

applications in a wide range of aggressive environments. What is

not so widely known, however, is that stainless steel possesses out-

standing mechanical properties and good workability. All in all, theseproperties make stainless steel a valid alternative to structural carbon

steel and in some cases also to aluminum alloys. Though the initial

material costs are higher, they allow significant cost savings in terms

of overall lifecycle cost and environmental benefits, for example lower

fuel consumption. Within the framework described here, a new class of

structural stainless steels, namely austenitic N-Mn grades, is attracting

more and more interest due to their combined properties of corrosion

resistance and high strength. Italian-based ThyssenKrupp Acciai

Speciali Terni is without doubt a leader with regard to research, devel-

opment and industrialization of this class of materials, which opens

up new perspectives in terms of efficiency and performance.

General properties of advanced high-strength stainless steels

Austenitic N-Mn stainless steels display a unique combination of

mechanical strength, ductility I Fig. 1 I and, of course, corrosion resist-

ance. STR18, recently launched by ThyssenKrupp Acciai Speciali Terni,

represents the worlds latest development in this class of steel. It is

a fully austenitic N-Mn stainless steel with 18% Cr content. This

steel is characterized by high mechanical strength levels as well as

excellent formability/workability thanks to the exploitation of TWIP/TRIP

(Twinning Induced Plasticity/Transformation Induced Plasticity) effects.

Generally speaking, its typical properties are:

high strength: Rp >420 MPa; Rm >750 MPa;

outstanding formability, especially given the mechanical strengthlevels: A% >45%

good weldability and corrosion resistance (substantially equivalent

to AISI 304/ EN 1.4301).

Moreover, austenitic microstructures in general and grades with

high N-Mn content in particular display a higher strain hardening

coefficient. As a consequence, mechanical characteristics are im-

proved dramatically by cold deformation, although this also results in

de-creased formability I Figs 2 and 3 I. This gives material designers

the freedom to customize material properties by cold rolling in line

with the intended application.


Fig. 1 | Characteristics of STR18 in comparison with main classes of high-strength steel

30 | High-performance and environment-friendly advanced high-strength stainless steels in automotive applications

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48

44

40

36

32

28

24

20

16

12

8

4

0


Fig. 3 | Variation of mechanical properties of STR18 as a function of pre-strain (cold rolling)

Cold reduction ratio [%]

ElongationA[%]

0 5 10 15 20 25 30 35 40 45 50 55 60 65

Stress

,R

p0

,2,

Rm

[MPa]

1,600

1,500

1,400

1,300

1,200

1,100

1,000

900

800

700

600

500

400

True stress

AISI 304 ann

AISI 304 3/4H AISI 304 1/2H

1,500

1,000

500

0

0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4

Truestrain[MPa]

Fig. 2 | Stress-strain curves of STR18, at various pre-strain levels, compared with stress-strain curves of typical carbon and stainless steel grades

High-performance and environment-friendly advanced high-strength stainless steels in automotive applications | 31

Rm

Rp0,2

A

STR 18

AISI 304 1/4H

AISI 301 1/4H

AISI 420 ann

DP 1000

DP 800

DP 600

220 BHFePO4

DP 500380TM

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32 | High-performance and environment-friendly advanced high-strength stainless steels in automotive applications

Mechanical characteristics also depend on the strain rate value;

the higher the load application rate, the greater the material resist-

ance. Stainless steels, especially austenitic grades, have a substan-tial advantage over light alloys or carbon steels in terms of their

greater sensitivity to strain rate. This property is particularly bene-

ficial when it comes to passive safety (crash safety): it allows the

realization of components with equivalent performance but much

lower weight than conventional components.

Advanced high-strength stainless steel in automotive applications

The properties described provide designers with a wide range of

options for weight reduction. Their effects are particularly noticeable

in the automotive sector where they lead to both improved vehicle

handling and reduced fuel consumption. The automotive sector holds

an important strategic position both due to its high sales volumes

and because it exerts a greater influence on research and develop-

ment strategies than other sectors. Examples include the develop-

ment of new technologies, products, production processes, quality

assurance methods and partnerships as well as new concepts for

distribution, organization and logistics. Car makers have repeatedly

pointed out the importance of using steels of ever higher perfor-

ance to meet the following needs:

higher structural stiffness while at the same time saving weight

in order to improve vehicle handling.

higher performance in terms of passive safety (crashworthiness);

this issue is also important in terms of the quality perceived by

end users,

weight saving in order to reduce fuel consumption and thus meet

emissions standards.

The latter point is particularly important in relation to environmental

aspects, as lower weight is a key factor in lowering fuel consumption.

Extensive studies carried out by carmakers show that weight and tire

rolling resistance are surpassed only by aerodynamics in terms of

their influence on fuel consumption. Hence it is clear that choosing

the right material, such as special steel, is a very effective meansof improving vehicle fuel efficiency. On the other hand, the intro-

duction of more and more optional accessories such as multimedia

devices, parking sensors, driving assistance devices (e.g. automatic

gearbox) requested by customers even in entry level cars is increasingvehicle mass and thus fuel consumption.

The use of high-strength stainless steel can therefore be an

effective way of reducing fuel consumption. An extensive analysis

recently carried out by Ford came to the conclusion that by using

stainless steel it is possible to save up to 25% in weight compared

with the use of conventional structural steels. Values observed in this

respect closely match those determined in recent years by several

internal workgroups assigned by ThyssenKrupp Acciai Speciali Terni

to Italys largest commercial vehicle company. The aim of these

studies was the application of advanced materials for parts involved

in passive safety. In this study different materials were compared

with a reference solution of carbon steel. The findings have been

validated by the research center of the aforementioned company.

The STR18 solution was the one with the highest weight saving

with respect to the reference solution and also proved to be slightly

better than aluminum. Although the specific density of aluminum is

only about one third of that of steel, its modulus of elasticity and

yield strength are also only about a third as high as those of high-

strength steels I Fig. 4 I.

Another important advantage of stainless steel is its corrosion

resistance, allowing end users to avoid expensive and potentially

harmful anti-corrosion treatments. This is especially beneficial for

safety-relevant parts, as they can be installed without the need for

treatment which helps save costs. Very interesting results have been

achieved in this area, as passive safety elements are usually manu-

factured separately from the car body and installed later, allowing

the anti-corrosion properties to be exploited in full.

Another very positive aspect is the fact that stainless steel can be

recycled, given that every year, end-of-life vehicles in the European

Union generate between 8 and 9 million tons of scrap. In order to

make the dismantling and recycling of this scrap mountain more

environmentally friendly, in 1997 the European Commission adoptedthe so-called End of Life Vehicle Directive10. This regulation imposes

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High-performance and environment-friendly advanced high-strength stainless steels in automotive applications | 33

Conclusion

The use of advanced high-strength stainless steels in modern vehicles

can make a significant contribution to reducing weight and thus to

lowering fuel consumption. At the same time, the outstanding me-

chanical properties of these materials contribute to an improvement

in passive safety (crash performance). As a result, stainless steel

serves to protect both the environment and vehicle occupants.

Fig. 4 | Comparison of mechanical properties of high-strength steels and aluminum alloys

Material Duplex STR18 Structural 6061 Carbon High

Stainless Steel Austenitic Stainless Steel Aluminium Alloy Strength Steel (HSLA)

Annealed CR 6 CR 9 CR 12 CR 15 T4 T6

State (1) (2) (3) (4) (5) (6) (7)

Density [g/cm3] 7.80 7.90 7.90 7.90 7.90 7.90 2.70 2.70 7.83

Density relative to steel 1.00 1.00 1.00 1.00 1.00 1.00 0.35 0.35 1.00

Yield strength Rp0,2 [N/mm2] 640 450 533 647 690 813 145 275 410

Tensile strength Rm [N/mm2] 850 750 762 833 861 944 240 310 480

Specific strength Rp/ [N/mm2/g/cm3) 82.1 57.0 67.5 81.9 87.3 102.9 53.7 101.9 52.4

Specific strength rel. to HSLA Steel 1.57 1.09 1.29 1.56 1.67 1.97 1.03 1.95 1.00

Elongation [%] 35.00 45.00 39.00 33.00 29.4 20 15.00 8.00 22.00

Elongation with respect to HSS 1.59 2.05 1.77 1.50 1.34 0.91 0.68 0.36 1.00

Youngs modulus E [kN/mm2] 200 200 200 200 200 200 70 70 200

Spezific stiffness E/ 26 25 25 25 25 25 26 26 26

(1): in the solution annealed condition

(2): in the cold worked condition with a 6% cold reduction ratio




(6): the T4 temper is solution heat treated at 503 C and then water quenched

(7): the T6 temper is precipitation heat treated at 160 C for 18 hours, or is heated at 180 C for 8 hours and then air cooled

minimum requirements on auto manufacturers for the use of recyclable

materials from 75% in 2006 to 95% in 2015.

Unlike many other engineering materials such as polymers/plastics,

stainless steels properties make it 100% recyclable without any

degradation. Currently, stainless steel parts comprise 60% recycled

material (25% originating from other end-of-life products and 35%

from relatively new products of the same type). The main reason why

recycled material input is not higher is that stainless steel demand iscontinuously growing.

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34 |

| Forged shaft produced by Societ delle Fucine at the Siemens Power Generation (PG) plant

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| 35

Large forged shaftsfor power generation

Continuing efforts to increase efficiency and reduce emissions from

large thermal power plants have seen a corresponding trend toward

ever higher steam temperatures and pressures as well as advanced

turbine technology. In this context the Italian-based Societ delle

Fucine (SdF), a company of ThyssenKrupp Acciai Speciali Terni,

manufactured and supplied the high-pressure (HP) rotor shaft of the

biggest steam turbine in the world to Siemens AG. The power plant,

denominated Olkiluoto 3, is located in the heart of the countryside in

Finland. To produce this HP rotor shaft, SdF used a special low-alloy

steel ingot of approx. 230 metric tons.

DIPL.-ING. STEFANO NERI Quality Management | Societ delle Fucine S.r.l., Terni/Italy

DIPL.-ING. DANIELE MARSILI Metallurgy | Societ delle Fucine S.r.l., Terni/Italy

DR. RER. OEC. GIOVANNI SANSONE Sales Management Power Generation | Societ delle

Fucine S.r.l., Terni/Italy

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36 | Large forged shafts for power generation

Fig. 1 | Steam turbine shaft with blades

Steam turbine for a nuclear power plant in Finland

The nuclear power plant near the west coast of Finland on the island

of Olkiluoto (municipality of Eurajoki) is being built for the economical

generation of base-load power. Environmental conditions in Olkiluoto

are monitored in compliance with approved programs. The extensive

measurement and observation system had already been set up before

the first plant unit started operation. The environmental impact of the

nuclear power plant is reduced by following the principle of prevention

and continuous improvement.

The conventional steam turbine for Olkiluoto 3 was manufactured

by Siemens Power Generation (PG). The turbine section also includes

the HP stage which is of the double-flow type and features a double-shell design with horizontally split outer and inner casings. The rotor

of the HP turbine consists of a forged, mono-block shaft with forged-

on coupling flanges; the moving blades are held in slots. The rigid

HP rotor has operational advantages over flexible rotors in that it

maintains relatively small clearances, suffers no instability due to

resonance zones during start-up, has no power limitation due to

steam turbulence, and finally no self-created oil film vibration can

occur. The blading is of a variable reaction type. All the moving and

stationary blades are integrally shrouded and tightly locked together

I see title picture of the report and Fig. 1 I.

The steam turbine for the new nuclear plant in Finland was

designed to have a net output of approximately 1,600 MW and a net

efficiency of about 37%. The turbine section is of a tandem compound

design and consists of a double-flow high-pressure (HP) turbine and

a six-flow low-pressure (LP) turbine solidly coupled to a three-phase

synchronous generator with a directly connected exciter. Societdelle Fucine, supplied the mono-block forged shaft for the HP stage

of the steam turbine on the basis of drawings from Siemens Power

Generation (PG).

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Large forged shafts for power generation | 37

Manufacturing the steam turbine

Ingot making

The steelmaking process for the Olkiluoto rotor was as follows:

Electric Arc Furnace (EAF) treatment

Melting of selected scrap, dephosphorization phase, deslagging and

renewal of slag, heating to reach tapping temperature; tapping into

the ladle and steel killing by silicon addition.

Refining treatment

The refining treatment of the liquid steel was performed in the plant

from Asea Brown Boveri Ltd., following deslagging and addition

of new slag formers, short vacuum treatment to obtain steel-slag

deoxidation, heating and alloying, vacuum degassing, argon rinsing.

Ingot pouring

A vacuum process was used to pour the 230 t ingot. Prior to this,

the ingot solidification model and carbon macrosegregation were

studied by the use of FE modeling I Fig. 2 I. Accurate analyses were

performed by means of thermovision I Fig. 3 I to optimize the ingot

weight and hot top insulation.

Shaft forging

After stripping, the ingot was forged in the 12,600 ton forging press.In this phase, the ingot was hot deformed in several steps starting

Fig. 2 | FE (finite element) analysis with the carbon

macrosegregation map at the end of solidification

Fig. 3 | Ingot hot top insulation checked by Thermovision

from a temperature of 1,200 C. During this process the workpiece

was forged several times close to the minimum temperature allowed

and then reheated in the furnace so as to ensure the correct defor-

mation of the steel. The forging operation continued for several hours

until the pre-defined shape was obtained; the final weight at this

stage was 138 t.

Such forging operations have to be extremely accurate, even

for ingots as heavy as 230 tons and even using a press as powerful

as 12,600 t I Fig. 4 I. This forging operation is without doubt the

most critical step in the production process, as it is here that the

desired microstructure (uniform tempered bainite) and fine grain

size are obtained.

Quality heat treatment

After the completion of the forging work a series of preliminary heat

treatments (normalizing, tempering) and quality heat treatments

(hardening, tempering) were performed in accordance with a specific

profile with the purpose of realizing and obtaining the desired mechan-

ical properties. The hardening treatment consists of a liquid quenching

to produce uniform characteristics. The shaft is then quenched until

the temperature in the center of the rotor body is less than 100 C.

The tempering temperature is selected to achieve the prescribed

0.2% yield strength and the best possible toughness. The duration

of tempering as well as the controlled cooling rate are chosen toobtain minimum residual stresses and are measured by a specially

293.6

200

150

100

50

Temperature [C]

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38 |

Fig. 4 | Forging operations on the 12,600 ton forging press

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Large forged shafts for power generation | 39

Final machining and magnetic particle inspection

Following the positive result of the ultrasonic test examination, final

machining was performed on a horizontal lathe to obtain the final

shape as per client drawing I Fig. 5 I. The delivery weight was 96 t

with a diameter of 1,830 mm and a total length of 7,698 mm. Only

after completion of machining was the outside surface of the rotor

shaft tested by means of magnetic particle inspection.

Conclusions

The realization of such an important forging is in line with the highest

quality levels required in the power generation sector. Societ delle

Fucine has been recognized by Siemens Power Generation (PG) as akey supplier of such components and in August 2007 was awarded

with the supplier prize Pioneer in manufacturing of forged compo-

nents for the worlds largest steam turbine.

On the basis of this success, Societ delle Fucine will continue to

develop such components and equipment which are subject to top

quality standards.

developed and qualified method (e.g. the ring core method of Kraft-

werkunion KWU). It was specified that the residual compressive

stresses should not exceed 60 MPa.

Mechanical testing

A series of mechanical tests, such as tensile and Charpy V-notch

testing, were performed upon completion of the heat treatment to

verify the obtained mechanical properties. Sampling was executed

according to Siemens specifications. The tensile and impact speci-

mens were removed at a distance of 40 mm from the heat-treated

surfaces. The mechanical characteristics achieved at room temper-

ature were:0.2% yield strength: 580-680 MPa

Tensile strength: 16%

Reduction of area: >50%

Impact strength: >100 J

Skin cut and ultrasonic examination

Having obtained and verified the mechanical properties, the piece

was machined to provide it with a surface shape and quality allowing

ultrasonic testing (UT) to be performed according to the Siemens

procedure. The soundness of all parts of the rotor shaft was checked

to very stringent requirements; the maximum acceptable axial defect

was 3 mm equivalent diameter.

Fig. 5 | Final machining of the rotor shaft

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40 |

| Tubes of Nicrofer 5520CoB - alloy 617B in the component test facility in the Scholven power plant, COMTES 700

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| 41

Nickel alloys for tomorrowspower plants

Increases in the efficiency of fossil fuel-fired power plants are increasingly

leading to higher temperatures and pressures, thus making the use of nickel

alloys essential. Nickel-based superalloys are already routinely used in gas

turbines of combined cycle power plants. With the development of the 700 C

technology for coal-fired power plants, nickel alloys are now also being used

in boilers and steam turbines in the next generation of power plants. Together

with power plant operators and manufacturers of boilers for power plants,

ThyssenKrupp VDM has developed alloy variant Nicrofer 5520CoB- alloy 617B,

a material that has already demonstrated its suitability for the 700 C power

plant in a pilot facility.

DR.-ING. JUTTA KLWER Senior Vice President Research and Development | ThyssenKrupp VDM, Werdohl

DR. RER. NAT. BODO GEHRMANN Project Manager Super Alloys, R&D | ThyssenKrupp VDM, Werdohl

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Nickel alloys for tomorrows power plants | 43


loading, to high temperature corrosion and to high temperature creep.

Good formability and good weldability are important for the manu-

facture of complicated combustion chamber components. There

are few materials that fulfill these requirements. I Fig. 4 I shows the

composition of typical gas turbine materials from ThyssenKrupp

VDMs portfolio. Nickel in combination with molybdenum, cobalt

and tungsten ensures the required creep rupture, creep and fatigue

strength. A chromium component of the order of approximately 20%

ensures the resistance to high temperature corrosion. Aluminum and

titanium also increase the creep rupture strength by precipitating

strength-increasing intermetallic NiX(Al,Ti)y phases at the operating

temperature. These elements must, however, be extremely carefully

dosed, as too high a concentration of intermetallic phases leads to a

brittle, no longer formable and non-weldable material. ThyssenKrupp

VDM possesses know-how in this area that has been acquired overmany years.

Further developments of materials primarily affect the working

properties of the sheet materials used. High precision analyses and

the use of modern remelting technologies ensure that the structure

of the sheet materials is free of oxidic inclusions. This is a precon-

dition which must be fulfilled if the material is to be workable using

modern forming processes and capable of being welded using high-

performance welding processes.

Nickel alloys in the boilers of 700 C power plants

Until now, high temperature structural steels or martensitic steels of

type P91 or P92 have been used in the boilers of coal-fired power

plants. These boiler steels demonstrate good strengths at steam

temperatures of up to 600 C. At boiler temperatures of 700 C and

steam pressures of 350 bar, conventional boiler steels are, however,

no longer suitable. This is because they demonstrate almost noremaining thermal stability at these temperatures as I Fig. 5 I shows

Gas/Oil

Air

Cooling water

Hydrogen-rich gas

CombustionChamber

Condensator

Steam turbine

Exhaust-

gas

Electricity

Head recovery

steam generator

Gas turbine

Steam turbinegenerator

Gas turbine

generator

Fig. 2 | Combined cycle technology flowchart

Electricity

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44 |

using the example of the 100,000 hours creep rupture strength for the

martensitic boiler steel P91. Standard stainless steels can be used

at up to higher temperatures, the required minimum creep rupture

strength of 100 MPa at 700 C is, however, currently not achieved by

any stainless steel.

Because of this, the gas turbine material Nicrofer 5520Co alloy

617 mat. no. 24663 was selected for the boiler of the first coal-

fired power plant in 700 C technology, following extensive testing. The

selection was made by a team consisting of power plant operators

and boiler, component, pipe and materials manufacturers. Many

years of experience with this material in gas turbine manufacture, the

materials creep rupture strength of more than 100 MPa at 700 C

and the good working properties and weldability led to the selection

of this material. Furthermore, Nicrofer 5520Co is approved for pres-

sure tank construction for working temperatures of up to 1,050 C.

In order to realize designs with the thinnest possible walls, the

special variant Nicrofer 5520CoB alloy 617B was manufactured for

use in power plant boilers. A further increase of 20% in the special

variants permissible mechanical loads was achieved by alloying with

boron and the use of exactly measured additives of the strength-enhancing elements aluminum, titanium, cobalt and carbon. I Fig. 6 I

shows the chemical composition of the special variant in comparison

with the standard variant. I Fig. 7 I shows the 100,000 hours creep

rupture strength of the modified variant in comparison with the

standard variant, according to individual expert opinions from the

TV Rheinland technical inspectorate.

The suitability of the material for application at 700 C has already

been successfully demonstrated. Pilgered and forged tubes and com-

ponents of Nicrofer 5520CoB are already in use in the test facility

COMTES (COMponent TESt Facility) at an E.ON power plant location

in Scholven, North Rhine-Westphalia, Germany I see title picture of

the report I. The thin-walled tubes were manufactured in the cold

pilger process and the thick-walled reheater tubes (up to 60 mm)

were bored from solid blanks.

The start of construction for the first 700 C power plant from

E.ON in Wilhelmshaven is scheduled for the year 2010. The process

is now entering the second phase for the materials and component

manufacturers. Here, the focus will be on economic standard pro-

duction of tubes and components from nickel alloys, taking into

account the extremely high quality requirements of the energy supply

utilities with respect to boiler materials.

Fig. 3 | Gas turbine

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Nickel alloys for tomorrows power plants | 45

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