Techforum 1 2008 En

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ThyssenKrupp

techforum Issue 1|2008

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ERRATUM

Other than stated, the cover picture of Issue 2/2007 shows the end stage of a steam turbine in the low pressure

downstream section.

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

Cover

The cover picture shows a fully mobile crushing plant operating in an

open-pit coal mine located in China. This new plant was developed

by ThyssenKrupp Frdertechnik as part of a priority research and

development project and has been in operation under difficult climatic

conditions in inner Mongolia since the end of 2007. The coal is loaded

by an excavator directly into the crushing plants feed hopper and a

crusher then reduces the ROM ore to a size suitable for transport by

belt conveyor. The key innovations lie with the unique functionality and

mobility of the machine while the very high capacity of up to 10,000 t/h

makes it an ideal crushing plant for large open pit mines worldwide.

The use of fully mobile crushing plants completely dispenses with theneed for truck transportation and offers, enabling potential reductions

in CO2emissions of up to 100,000 t per year for each system installed

in the mine.

Cross-segment cooperation with ThyssenKrupp Steel resulted in

the use of high-strength steel and liners with special wear properties

to provide adequate protection from the abrasive nature of the ore.

The fully mobile crushing plant was awarded 1st prize in the 2008

ThyssenKrupp Innovation Contest.

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ThyssenKrupp techforum 1 | 2008

Foreword |3

Dear readers,

An invention itself does not represent an innovation; not until the idea has been translated into market-

able products and services does it earn this status. Successfully implemented ideas were once again

rewarded in this years 9th ThyssenKrupp Innovation Contest. The award ceremony, to which all the

Groups executives and all participants in the final round of the contest were invited, took place on May 17,

2008 as part of the ThyssenKrupp Management Forum at the Ideas Park in Stuttgart.

First prize in this years contest went to a cross-segment innovation in the area of materials handling.

A German-Canadian team from ThyssenKrupp Frdertechnik and ThyssenKrupp Steel developed a new,

fully mobile crushing plant with downstream belt conveyors direct from the face for use in large open-pit

mining operations. Dispensing with the need for truck transportation significantly reduces operating

costs and at the same time substantially lowers CO2emissions, thus contributing to climate protectionand delivering clear economic benefits to operators. A first system of this type has been operating

successfully since 2007 in an open-pit coal mine in China under extreme production conditions. There is

market potential for these fully mobile crushers in all open-pit mining operations where large volumes

need to be moved, e.g. also in oil sands mining in Canada.

Second prize was awarded to a team from ThyssenKrupp Nirosta for the development of the new

material NIROSTA 4640. This innovative stainless steel is alloyed with a new combination of chromium,

nickel, manganese, copper and nitrogen and displays the same good properties as the long-established

NIROSTA 4301. By reducing the amount of cost-intensive nickel, the new material which is used e.g.

in white goods, household appliances, kitchen equipment and in the capital goods industry offers a

low-cost alternative which is already enjoying a high level of market acceptance.

Third prize went to a team from ThyssenKrupp Steel and the DOC Dortmund Surface Engineering Center

for the development of a process which for the first time allows the high-quality hot-dip coating of multi-

phase steels. Consecutive oxidation and reduction processes avoid the undesirable formation of oxides

on the surface caused by the increased alloy content of these steels. Multiphase steels coated by this

new process have great potential for automotive lightweighting, not least because they help reduce CO2

emissions from motor vehicles.

The other articles in this issue also underline the high level of entries to our Innovation Contest

and thus the innovative capacities of our Group.

Yours,

Dr.-Ing. Ekkehard D. Schulz,

Chairman of the Executive Board of ThyssenKrupp AG

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4| Contents

10| Innovative process for innovative steel concepts hot-dip galvanized multiphase steels

DIPL.-ING. MARTIN NORDEN Project Engineer Metallic and Inorganic Coatings | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DR.-ING. WILHELM WARNECKETeam Coordinator Metallic and Inorganic Coatings | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DIPL.-ING. GERNOT NOTHACKERSpecialist Coordinator Production FBA 8 | ThyssenKrupp Steel AG, DortmundDIPL.-ING. NORBERT SCHAFFRATHSpecialist Coordinator Electrical Maintenance FBA 8 | ThyssenKrupp Steel AG, Dortmund

A new and innovative process for the hot-dip galvanizing of multiphase steels has been developed by the DOC

surface engineering center (Dortmunder OberflchenCentrum) in collaboration with ThyssenKrupp Steel for indirectly

heated radiant tube furnaces and implemented for the first time in the state-of-the-art hot-dip galvanizing line FBA 8

at ThyssenKrupp Steel in Dortmund. The so-called oxidation/reduction technology creates the preconditions for

high-quality hot-dip coating of high-strength multiphase steels in a continuous strip coating process. This enables

ThyssenKrupp to develop the existing market potential of the multiphase steels. This technology is suitable for adaptation

for further hot-dip galvanizing lines and can expand the Groups existing production capacity for multiphase steels.

16| ZMg EcoProtect new coating for high-end corrosion protection

DIPL.-ING. OLIVER BENDICK Project Engineer Interface Chemistry and Electrochemistry | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DIPL.-ING. MICHAEL KELLER Team Leader Hot-dip Galvanizing Line 5, Industry Division | ThyssenKrupp Steel AG, Eichen

MANFRED MEURERTeam Leader Hot-dip Coating | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DR. RER. NAT. ERICH NABBEFELD-ARNOLD Head of Techn./Strategic Marketing, Competence Center C/C, Industry Division | Thyssen Krupp Steel AG, Eichen

DIPL.-ING. SABINE ZEIZINGERTeam Leader Hot-dip Galvanizing Line 8, Auto Division | ThyssenKrupp Steel AG, Dortmund

A new process has been developed for the manufacture of magnesium-bearing zinc coatings containing approximately

1% magnesium. Using this new process enables the coating to be produced in existing hot-dip galvanizing lines. The

high corrosion resistance of this coating makes it possible to halve the coating thickness while retaining the same

protective effect. The new coating thus makes an exceptional contribution to the conservation of resources. The new

flat steel product ZMg EcoProtect possesses improved resistance to cut-edge and cut-face corrosion. It is also a very

good substrate for organic coil-coated products. Trials as part of development partnerships have commenced withselected customers from the construction, garage door, domestic appliance, vehicle and automotive industries.

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28|

22|

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Contents I5

22| EcoSpace cockpit optimum interaction between plastic and steel in the vehicle interior

DIPL.-ING. MARTIN HINZ Manger Process Innovation, Sales/Engineering | ThyssenKrupp Steel AG, Dortmund

DIPL.-ING. PETER SEYFRIED Manager Technology Management, Sales/Engineering | ThyssenKrupp Steel AG, Dortmund

In cooperation with Johnson Controls, ThyssenKrupp has developed a cockpit support structure known as EcoSpace

that is an economical lightweight hybrid composite structure of steel and plastic, with a steel frame located only on

the drivers side. The new construction has a crash performance comparable to that of conventional cockpit support

structures while featuring 18% greater stiffness and a weight reduction of more than 20%.

28| Tailored blanks in hot stamping

DIPL.-ING. JRG MAASHead of Sales/Senior Manager Sales | ThyssenKrupp Tailored Blanks GmbH, Duisburg

WERNER STAUDINGEREngineering | ThyssenKrupp Tailored Blanks GmbH, Duisburg

In collaboration with Audi, ThyssenKrupp Tailored Blanks has successfully developed and integrated into production

processes a new manufacturing technology for tailored blanks for use in hot stamping. The work was carried out

within one year. The new technology represents the worlds first application of the product tailored blanks in hot

stamping along with plant engineering that is currently unique. These tailored blanks offer users all the advantages

of the previous areas of application and maximum process reliability. Different steel grades and sheet thicknesses

can be welded together. In this way, the new product supports the customer in achieving lightweight construction

and thus also in attaining environmental objectives. At the same time, the automakers production costs can be

significantly reduced.

32| Multi-purpose tailgate MPT a flexible tailgate module with integrated rack system

DIPL.-ING. RALF SNKEL Teamleader Product Innovation/Projects, Sales/Engineering | ThyssenKrupp Steel AG, Duisburg

The needs of customers play a decisive role in creating innovative product solutions for future generations of auto-

mobiles. Following customer surveys, ThyssenKrupp Steel, ThyssenKrupp Metal Forming and Webasto worked together

closely to develop the multi-purpose tailgate. The design of the flexible tailgate module implemented in the physical

prototype features maximum ease-of-use, the highest degree of functionality and flexibility and optimal use of thematerials involved.

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6| Contents

38| PLADUR M (Metal-Look) an elegant product made of coil-coated steel

BEATE FUGMANNMarket and Innovation Team, Industry Division, Color Profit Center | ThyssenKrupp Steel AG, Kreuztal

DIPL. WIRT.-ING. AXEL POHL Head of Sales-Market and Innovation Team, Industry Division, Color Profit Center | ThyssenKrupp Steel AG, Kreuztal

The Market and Innovation Team at ThyssenKrupp Steels Color Profit Center correctly identified customers wishes

for organic coil-coated products with a metal look at an early stage. The team then developed a suitable response in

the form of PLADUR M. Thanks to its elegant and appealing appearance, its good technological characteristics and

its attractive price, PLADUR M has been successful with customers from an extremely wide range of sectors and has

established itself alongside prepainted products for use in many different applications.

42| NIROSTA 4640 as a low-cost alternative to NIROSTA 4301 offering equivalent properties

DIPL.-ING. ARAZ ARDEHALI BARANI Materials Engineer | ThyssenKrupp Nirosta GmbH, Dsseldorf

DR.-ING. GABRIELE BRCKNER Head of Materials Technology | ThyssenKrupp Nirosta GmbH, Dsseldorf

DIPL.-ING. MANFRED BUCKEL Head of Materials Technology | ThyssenKrupp Nirosta GmbH, Krefeld

DIPL.-ING. GERT WEIHead of Product Service | ThyssenKrupp Nirosta GmbH, Krefeld

DIPL.-ING. ALFRED WELTER Technical Customer Consulting | ThyssenKrupp Nirosta GmbH, Krefeld

Austenitic chromium-nickel steels find a wide range of applications thanks to their universal properties. In response

to the development of prices of alloy components, ThyssenKrupp Nirosta has developed the new steel grade

NIROSTA 4640, which demonstrates the same good properties as the widely used material NIROSTA 4301. The

alloy concept utilizes a new combination of the elements copper, nitrogen and manganese to lower the nickel content.NIROSTA 4640 is especially suitable for the area of white goods, e.g. dishwashers, and for sinks and similar products.

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Contents |7

46| Mixed construction using work-hardened NIROSTA steel and flat-rolled carbon steel

with tailored blanks and tailored strips

DIPL.-ING. STEFAN SCHUBERTH Head of Applications Technology | ThyssenKrupp Nirosta GmbH, Krefeld


Mixed construction using galvanized flat-rolled carbon steels and hardened, austenitic stainless steels is particularly

difficult due to the differing physical properties and levels of strength. Embrittlement in the weld seam can lead to

failure during subsequent forming. Exact process control of the laser welding in the manufacture of the tailored blanks

has now made it possible to produce blanks with ductile seams and large changes in thickness that measure up to

the demands of the subsequent forming process. The combination of work-hardened, stainless austenitic steel and

carbon steel yields weight savings without disadvantages in terms of properties. Possible applications include crash-

relevant components in vehicle manufacture.

50| Nickel W14 substrates for high-temperature superconductors

DR.-ING. ANGELIKA KOLB-TELIEPSHead of Knowledge and Innovation Management | ThyssenKrupp VDM GmbH, Altena

DR. RER. NAT. BODO GEHRMANN Project Manager Super Alloys and Physical Materials | ThyssenKrupp VDM GmbH, Altena

High-temperature superconductivity is on the threshold of market launch. Starting from the results of a research

project, ThyssenKrupp VDM has successfully developed an industrial-scale production process for nickel W14, which

is used as substrate strip in superconductors destined for applications such as generators for wind turbines. The

deoxidation of the melt presented a particular challenge. On the one hand, this is required in order to avoid fractures

during the hot forming, on the other, the usual deoxidation elements have negative effects on the nanoscale texture

and surface roughness needed for the substrate strip.

56| Alloy for heating elements with reduced nickel content

DR. RER. NAT. HEIKE HATTENDORF Project Manager Research & Development | ThyssenKrupp VDM GmbH, Altena

DIPL.-ING. JRGEN WEBELSIEPManager Quality Assurance Wire Division | ThyssenKrupp VDM GmbH, Werdohl

For the open heating elements of appliances such as clothes driers and in-room heaters, American manufacturers in

particular like to employ heating element wires made of the alloy Cronifer II. Heating element wires have to meet tough

requirements in such applications. For example, the wire coil may not sag or burn through at high temperatures.

As a result of its high nickel content (approx. 60%), the material known as Cronifer II that was previously used is

expensive and therefore no longer competitive for this application. By increasing the chromium content and precisely

matching the various elements to one another, the developers have created an alloy that contains just 37.5% nickelwhile still meeting the demanding technical requirements.

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8| Contents

60| Increasing energy efficiency and reducing investment costs in cement production

DIPL.-ING. FRANZ-JOSEF ZURHOVESpecialist Department Research & Development, Head of Grinding & Crushing Technology | Polysius AG, Neubeckum

The POLYCOM high-pressure grinding roll and the newly developed SEPOL HR separator have established new

benchmarks for energy efficiency in the grinding of raw materials for cement manufacturing. Previous use of the high-

pressure grinding roll for this process was limited to niche applications featuring, for example, low levels of moisture

and abrasion and lower throughput rates. With the successful commissioning of two grinding plants with POLYCOM

and SEPOL HR, Polysius is setting a new benchmark for efficiency, quiet running and reliability. The attractive

investment costs are a welcome complement to the low operating costs.

66| Fully mobile crushing plant for large open-pit mines

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

DIPL.-ING. FRANK SEEHFERSenior Manager Projects | ThyssenKrupp Frdertechnik GmbH, Essen

DIPL.-ING. MARTINA SHEHATA M.SC, P.ENG. Vice President Engineering & Project Management | Krupp Canada Inc., Calgary/Canada

STEPHEN HARRINGTON, B.ENG, P.ENG.Vice President Sales | Krupp Canada Inc., Calgary/Canada

DR. RER. NAT. HANS-JRGEN KAISER Head of Technical Marketing, Heavy Plate Profit Center | ThyssenKrupp Steel AG, Duisburg

As part of a priority research and development project launched in 2006, engineers at ThyssenKrupp Frdertechnik

developed the concept for a fully mobile crushing plant to enhance mining operations in large open pit mines. The

key innovations lie with the unique functionality and mobility of the machine which allow it to work along side the

mining shovel at the mine face. The crushing plant feeds a dedicated belt conveyor system and the need for large

haul trucks is eliminated. The use of continuous mining technology not only brings economic benefits in the form

of higher production performance with reduced capital cost (particularly when compared to a discontinuous system

using trucks), it is also more environmentally friendly because it reduces CO2emissions. In a cross-segment coop-

eration with ThyssenKrupp Steel, the developers investigated the use of high strength steel and utilized liners withspecial wear properties to provide adequate protection from the abrasive nature of the ore.

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Contents |9

74| Combined end-of-line test stand for NVH analysis and determining

the balancing quality of rear axles

DIPL.-ING. JRG TIETJENVice President Test/Measurement Technology | ThyssenKrupp EGM GmbH, Langenhagen

DIPL.-ING. JOAKIM KHL Development Test Technology | ThyssenKrupp EGM GmbH, Langenhagen

Todays vehicles have to meet high standards with regard to ride comfort, making balancing the drive train and noise

testing of many components essential. ThyssenKrupp EGM, an internationally leading supplier of comprehensive

solutions for transmission test stands, has eliminated the traditional distinction between balancing machines and

NVH test stands. It has done so by developing, testing and realizing as a product a new test stand concept that unites

both technologies in a single machine. Key arguments in favor of the new system, for which a patent has been applied,

are its huge cost advantages and the reduced amount of space it requires.

80| Using electro-permanent magnets to lift loads in modern logistics networks

DIPL.-PHYS. WILHELM CASSING Sales Manager, Authorized Officer | ThyssenKrupp Schulte GmbH, Gelsenkirchen

DIPL.-ING. THOMAS POHLTechnical Manager, Authorized Officer | ThyssenKrupp Anlagenservice GmbH, OberhausenDIPL.-ING. FALK STEGER Sales Magnet System| ThyssenKrupp Schulte GmbH, Gelsenkirchen

Because of the need to quickly load and unload steel slabs, a new technological concept had to be developed for

lifting loads. Given the same requirements, such as being able to unload 36-ton slabs, electropermanent magnets

offer a number of advantages over conventional electromagnets and chains. These include the fact that they do not

require either environmentally damaging backup batteries or the use of dunnage in an integrated logistic chain. And

thanks to savings in weight, the magnets can significantly reduce crane costs. Other, non-monetary benefits affect

occupational safety and environmental protection.

86| Sustainable energy generation with combined-cycle power plants (GuD)

JRGEN STIRNHead of Technology | ThyssenKrupp Xervon Energy GmbH, Duisburg

DIPL.-ING. WILFRIED RUTHMANN Project Manager Technology | ThyssenKrupp Xervon Energy GmbH, Duisburg

DIPL.-ING. MARTIN HBLER Construction Planning | ThyssenKrupp Xervon Energy GmbH, Duisburg

DIPL.-ING. GERHARD SCHIWIETZ Sales | ThyssenKrupp Xervon Energy GmbH, Duisburg

PETER DIEKMANNPublic Relations | ThyssenKrupp Services AG, Dsseldorf

Combined-cycle power plants have a number of virtues. They are not only profitable but also very environmentally

friendly, simple in design and suitable for a broad range of applications. Following deregulation of the electricity market,

this technology offers many municipal utilities an economically viable means of modernizing their old cogeneration

power plants. In Wrzburg, for example, successful cooperation between ThyssenKrupp Xervon Energy and Heizkraft-

werk Wrzburg GmbH has recently seen the completion of the first phase in a project to upgrade a coal-fired power

plant to a combined-cycle facility. On this basis, an innovative concept has been devised to build a second combined-

cycle generating unit on the same site. This modernization project combines the benefits of low-emission fuel utilizationwith efficient combined-cycle technology for the cogeneration of heat and power.

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10|

|Hot-dip galvanized rolled sheet in the hot-dip galvanizing line FBA 8 in Dortmund

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|11

Innovative process for innovativesteel concepts hot-dip galvanizedmultiphase steels

A new and innovative process for the hot-dip galvanizing of multiphase steels has been developed

by the DOC surface engineering center (Dortmunder OberflchenCentrum) in collaboration with

ThyssenKrupp Steel for indirectly heated radiant tube furnaces and implemented for the first

time in the state-of-the-art hot-dip galvanizing line FBA 8 at ThyssenKrupp Steel in Dortmund.

The so-called oxidation/reduction technology creates the preconditions for high-quality hot-dip

coating of high-strength multiphase steels in a continuous strip coating process. This enables

ThyssenKrupp to develop the existing market potential of the multiphase steels. This technology

is suitable for adaptation for further hot-dip galvanizing lines and can expand the Groups existingproduction capacity for multiphase steels.

DIPL.-ING. MARTIN NORDENProject Engineer Metallic and Inorganic Coatings | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DR.-ING. WILHELM WARNECKETeam Coordinator Metallic and Inorganic Coatings | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DIPL.-ING. GERNOT NOTHACKERSpecialist Coordinator Production FBA 8 | ThyssenKrupp Steel AG, Dortmund

DIPL.-ING. NORBERT SCHAFFRATHSpecialist Coordinator Electrical Maintenance FBA 8 | ThyssenKrupp Steel AG, Dortmund


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12 | Innovative process for innovative steel concepts hot-dip galvanized multiphase steels

Lightweight construction using multiphase steels

The increasing demands on occupant protection in modern motor

vehicles and their CO2emissions require both the automotive and the

materials industries to apply innovative methods of reducing weight

while simultaneously increasing the rigidity of the vehicle bodywork.

The replacement of conventional steels by multiphase steels provides

an important element in the basis of the weight reduction and the

improved crash strength of the bodywork and so makes a significant

contribution to achieving these objectives.

New lightweight designs can only be achieved by the use of corre-

spondingly innovative materials that measure up to the customershigh requirements. Multiphase steels from ThyssenKrupp Steel offer

a wide range of capabilities with respect to formability and strength

and are available in various surface qualities. Due to the increasing

demand, ThyssenKrupp Steel is continually expanding its range of

multiphase steels by the continuous further development of new

steel concepts through to production maturity I Fig. 1 I.

A surface coating that effectively protects the component against

corrosion over its entire life cycle is essential for the application of

new, innovative steel concepts for structural elements in automotive

manufacture. Multiphase steels are normally galvanized by hot-dip or

electrolytic galvanizing in a continuous strip coating process. Due to

its ecological and economic efficiency, continuous hot-dip galvanizing

plays an important role here.

Challenges for hot dip galvanizing

Recrystallizing annealing represents a decisive process step in the

hot-dip galvanizing process with respect to the technological prop-

erties of the multiphase steel. Alloying elements such as aluminum,

boron, chromium, manganese, niobium, phosphorus, silicon, tita-

nium and vanadium are added in controlled amounts to produce the

mechanical/technological properties. In the classical recrystallizing

annealing process, these alloying elements form stabile oxides that

cannot be reduced despite a hydrogen-bearing shield gas atmosphere.

This makes the development of a new process technology essential

and requires a fundamental understanding of the mechanisms of

the reactions that are taking place.

The laws of thermodynamics describe chemical reactions in

general. They can be used to derive an understanding of the mech-

anisms and to predict the progress of the reactions. The Gibbs free

energy of reaction (RG) provides information as to whether a chemical

reaction will occur spontaneously or not. Reactions which run in the

direction of the reaction products have a free energy of RG < 0, whichmeans that the reaction runs of its own accord. Reactions that do

not run spontaneously have a free energy of R

G > 0, i.e. the reaction

does not take place or must be forced to occur by the input of energy.

The spontaneously occurring reactions of metals with oxygen can,

for example, be described by the following chemical equation:

The result of the reaction of iron and oxygen is to convert the

pure iron into iron oxide. The shield gas atmosphere in the annealing

furnace of a hot-dip galvanizing line is intended to prevent oxidation

of the surface of the steel strip during annealing and to reduce any

surface oxides that may be present by reacting them with hydrogenaccording to the following mechanism:

The objective is to prepare a purely iron-bearing surface for the hot-

dip coating process. The reduction results in the addition of water

vapor (H2O) to the annealing gas atmosphere. The water vapor

content of the annealing gas atmosphere is given as a dew point,

an old meteorological unit commonly used for measuring humidity.

Due to the high temperatures of the annealing gas atmosphere, some

dissociation of the vapor-phase water resulting in the presence of

traces of oxygen is unavoidable:

For this reason, the dew point is taken to be a measure of the oxygen

content of an annealing gas atmosphere. At high temperatures, the

free oxygen formed as a result of this reaction can oxidize the alloying

components of the steel.

Both processes, the oxidation and the reduction of the steel strip

surface, achieve an equilibrium in the annealing gas atmosphere.

Considering the free energy of reaction is extremely useful when

discussing the possible reactions in the annealing gas atmosphere

and is addressed in detail in the so-called Richardson-Ellingham

diagram. This diagram can be used to estimate whether an alloy

component of a steel will be present as an oxide or as the element

taking into account the temperature, the hydrogen content and the

water vapor content. In contrast to iron oxide, the oxides of alloying

elements with very negative free energies such as silicon, man-

ganese, chromium and aluminum cannot be reduced under the

conditions of the annealing gas atmosphere in hot-dip galvanizing

lines. Should these oxides of the alloying components be present in

higher concentrations on the strip surface, they could hinder the

reaction of the molten zinc with the iron and lead to inadequatewetting and adhesion.

2Fe + 02 2Fe0

Fe0 + H2Fe + H

20

2H20 0

2+ 2H

20

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|13

This observation makes it clear that the temperature and the partial

pressure of oxygen in the annealing gas atmosphere are two factors

in a complex reaction chain subject to influence by a large number

of factors. The high proportion of non-reducible alloy components in

multiphase steels makes a systematic investigation of the reaction

processes on the strip surface essential. The experience gained must

be used to develop a process that enables and ensures the wetting of

highly alloyed multiphase steels by the molten zinc. Reduction of the

alloying elements with very high affinities for oxygen is not possible

under the existing conditions. Varying the partial pressure of oxygen

in the annealing gas atmosphere offers an alternative approach by

means of which the location of the oxidation of the alloying compo-

nents can be changed. This approach is clearly illustrated by theexample shown in I Fig. 2 I. If a multiphase steel is annealed in an

oxygen-poor atmosphere as in the example, this results in an oxide

skin which covers the surface and can inhibit the formation of the

Fe2Al5inhibition layer in the subsequent galvanization step. The

alloying elements are thus externally oxidized. Increasing the partial

pressure of oxygen, in contrast, leads to an increase in the iron con-

tent at the surface, along with a simultaneous reduction in the oxide

proportion of the alloying elements. Increased oxygen diffusion along

the grain boundaries into the structure of the surface leads to the

oxidation of the alloying elements with a high affinity for oxygen

located below the surface. So-called internal oxidation occurs. This

leads to the proportion of interfering oxides on the surface being

minimized. The iron-rich surface achieved in this way is well-suited

to the optimal formation of a Fe2Al5inhibition layer in the hot-dipgalvanizing process.

Fig. 1| Strength classes and properties of conventional and multiphase steels

Fig. 2| Dependence of the surface composition on the dew point of the annealing gas atmosphere taking as an example TRIP 700, left: iron-rich surface due to internal oxidation;right: strongly oxide-coated surface due to external oxidation

* FE-SEM (Field Emission-Scanning Electron Microscope) analysis laboratory annealing: 800 C; 60 s, 95% N2, 5% H2

Dew point -15 C*

3 m

Dew point -30 C* Dew point -45 C*

3 m 3 m

Oxide

Fe

Oxide

Fe

Oxide

Fe

DC, DX

RA-K

HX HSZ

BHZ

WHZ

X-IP

RA-K development

DP-K development

CP-K developmentCP-KDP-K

*MBW-K

MHZ **MBW-K

70

60

50

40

30

20

10

0200 300 400 500 600 700 800 900 1.000 1 .100 1 .200 1 .300 1 .400 1.500 1.600 1.700

DC/DX Deep-drawing steels

HX High-strength IF steels

BHZ Bake-hardening steels

HSZ High-strength stretch-

forming steels

WHZ Work-hardening steels

MHZ Microalloyed steels

DP-K Dual-phase steels

RA-K Residual-austenite steelsCP-K Complex-phase steels

MBW-K Manganese-boron steels

for hot stamping

X-IP eXtreme strength and

formability through

nduced Plasticity

* as-delivered

** hot-stamped

Elongation

A80[%]

Tensile strength Rm[MPa]


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14| Innovative process for innovative steel concepts hot-dip galvanized multiphase steels

Due to the physical dimensions of the annealing furnace of a hot-

dip galvanizing line, it is not possible to influence the thermodynamics

of the atmosphere. As the oxidation of the high oxygen affinity elements

withdraws more water vapor from the annealing gas atmosphere than

is formed by the reduction of iron oxide, the dew point of the furnace

atmosphere during the production of multiphase steels tends to be very

low. The shift of the reaction equilibrium to low dew points has the

consequence that the oxides of the alloying elements form externally.

A thin oxide film is formed. This inhibits the classic Fe2Al5inhibition

layer reaction during hot-dip galvanizing and results in macroscopic

quality problems with respect to zinc wetting and adhesion.

Oxidation/reduction technology

It has been demonstrated that the humidification of the furnace

gas to force the desired internal oxidation is less effective and cost

intensive. Oxidation/reduction technology presents a more effective

approach for the hot-dip galvanizing of multiphase steels as shown

in I Fig. 3 I. Targeted oxidation of the entire steel strip surface in an

oxygen-bearing atmosphere causes the formation of iron oxide on

the surface.

Step 1: OxidationI Fig. 3, left I:

A defined external iron oxide layer of 150-200 nm thickness be created

using minimal quantities of oxygen approx. 0.2% at temperatures

above 700 C. This layer inhibits further, unwanted external oxidationof the alloying elements with a high affinity for oxygen. As iron oxide

can, in contrast to the other oxides of the alloying elements of multi-

phase steels, be reduced in the subsequent annealing process, a

sponge structure of pure iron is formed on the surface.

Step 2: ReductionI Fig. 3, middle I:

This iron-rich surface is advantageous for the reactions in the

molten zinc bath I Fig. 3, right I. Furthermore, the water vapor pro-

duced by the reduction of iron oxide supports the internal oxidation

of the alloying elements and stabilizes the dew point of the furnace

atmosphere. This effectively prevents a decrease in the dew point of

the annealing gas atmosphere. The enrichment of the surface with

iron by means of the oxidation/reduction step and the support for

internal oxidation by the water vapor formed combine to create the

conditions for a significant improvement of the Fe2Al5inhibition layer

in multiphase steels, thus ensuring the adhesion of and wetting by

the zinc.

If DFF (Direct Fired Furnace) technology is utilized in the pre-

heating zone of a hot-dip galvanizing line, a targeted oxidation of the

steel strip surface can be caused by adjusting the preheater burner

gas. The atmospheric conditions can be changed from oxidizing to

reducing by adjusting the air-fuel ratio of the burner gas. The oxidation

of the steel strip surface prior to its entering the reducing furnace

can be specifically controlled in this way.

On the other hand, installing oxidation/reduction technology in

hot-dip galvanizing lines with vertical RTFs (Radiant Tube Furnaces)poses a special challenge. This task was accomplished in a collab-

Fig. 3| The process of oxidation and reduction

Oxidation

Steel

Iron oxide

Reduction

Steel

Iron

Galvanized

Steel

Iron Fe2Al5

MnO, Al2O3....

2 m 2 m 2 m

MnO, Al2O3.... MnO, Al2O3....

Fe + O2 FeO2

1

FeO + H2 Fe + H

2O

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Innovative process for innovative steel concepts hot-dip galvanized multiphase steels |15

oration between the DOC surface engineering center (Dortmunder

OberflchenCentrum) and ThyssenKrupp Steel with the help of a

new, innovative process technology. The industrial scale technical

implementation of a closed oxidation chamber for targeted oxidation

of the steel strip surface was first installed in the annealing furnace

of the hot-dip galvanizing line FBA 8 I Fig. 4 I. in Dortmund. This

process makes it possible to carry out a corresponding conditioning

of the surface of the steel strip during the annealing process in existing

hot-dip galvanizing lines independent of the remaining furnace

atmosphere. The construction of a closed chamber permits targeted

oxidation in the closed reducing atmosphere of the furnace and pre-

vents unwanted mixing of the reactive gases oxygen and hydrogen.

After the steel strip surface has been oxidized, it is reduced in the

remaining section of the annealing line. This technology is used in

the continuous RTF to create a steel strip surface of multiphase steels

that has a positive effect on the hot-dip galvanizing and guaranteesthe wetting and adhesion of the zinc coating.

Conclusion and outlook

Innovative, weight-reducing steel concepts offer great potential in

lightweight automotive construction and lead to a sustainable reduc-

tion in CO2emissions. Oxidation/reduction technology is an innovative

process for guaranteeing the suitability of the new multiphase steels

for hot-dip galvanizing and sustainably improves surface quality. The

implementation of the technology in additional existing lines is possible

and is currently in progress. This innovative technology represents a

fundamental component in the planning of new hot-dip galvanizing

lines and expands the production capacity of existing facilities. By

ensuring zinc wetting and adhesion, oxidation/reduction technology

is making a decisive contribution to developing the market potential

of multiphase steels in automotive manufacturing.

Fig. 4| Schematic structure of FBA 8, Dortmund

Chemcoaterwith exit store

Onlinesurface inspection

Online

roughnessinspection

Zinc thicknessmeasurement

Intermediate storeSurfaceinspection

Skin pass mill

Galvanizing tower

Zinc pot andair knives

Annealing furnace

Cleaning Entry store

Laser weldingmachine

Entry

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16|

|Coating a hot-rolled sheet in a zinc bath

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Introduction

ThyssenKrupp Steel and the DOC surface engineering center (Dort-

munder OberflchenCentrum) have succeeded with a new develop-

ment in hot-dip coating the innovative coating ZMg EcoProtect.

Its implementation in numerous manufacturing operations at two

ThyssenKrupp Steel hot-dip galvanizing lines (FBA) was started

as early as 2006 I Fig. 1 I.

In principle, magnesium alloy additives in zinc improve the corro-

sion properties of the coating. However, currently known products

also include relatively high aluminum contents in addition to the

magnesium, which leads to limited forming, joining and painting

properties. As a result, these products are limited in application. They

are mainly used in the construction sector, in particular in environ-

ments with a maritime climate.

ThyssenKrupp Steel has therefore developed a zinc-magnesium

coating which possesses a balanced application spectrum. Alongsidesignificantly increased corrosion resistance compared to zinc coatings,

the new material has application properties at least comparable

with those of conventional zinc coatings. As a result, it has possible

applications in the construction, garage door, domestic appliance,

vehicle and automotive industries. Among other uses, the coating

ZMg EcoProtect is also an outstanding substrate for coil coating

applications.

The switch from laboratory scale to commercial production began

with a first trial run in March 2006. The material produced was char-

acterized in detail using a wide range of test procedures and tested

in application-specific experiments.

ZMg coating

A hypoeutectic composition with primary precipitated zinc-rich solid

solutions (Zn-Mk) and a eutectic of Zn-Mk with the intermetallic phase

Mg2Zn11, which forms peritectically, arise in a zinc melt with approxi-

mately 1% magnesium. The eutectic composition of 92.2 atom-% zincsolidifies under equilibrium conditions at 364 C. A magnesium content

|17

ZMg EcoProtect new coating forhigh-end corrosion protection

A new process has been developed for the manufacture of magnesium-bearing zinc coatings containing

approximately 1% magnesium. Using this new process enables the coating to be produced in existing

hot-dip galvanizing lines. The high corrosion resistance of this coating makes it possible to halve the

coating thickness while retaining the same protective effect. The new coating thus makes an exceptional

contribution to the conservation of resources. The new flat steel product ZMg EcoProtect possesses

improved resistance to cut-edge and cut-face corrosion. It is also a very good substrate for organic coil-

coated products. Trials as part of development partnerships have commenced with selected customers

from the construction, garage door, domestic appliance, vehicle and automotive industries.

DIPL.-ING. OLIVER BENDICKProject Engineer Interface Chemistry and Electrochemistry | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DIPL.-ING. MICHAEL KELLERTeam Leader Hot-dip Galvanizing Line 5, Industry Division | ThyssenKrupp Steel AG, Eichen

MANFRED MEURERTeam Leader Hot-dip Coating | DOC Dortmunder Oberflchencentrum GmbH, Dortmund

DR. RER. NAT. ERICH NABBEFELD-ARNOLDHead of Techn./Strategic Marketing, Competence Center C/C, Industry Division | Thyssen Krupp Steel AG, Eichen

DIPL.-ING. SABINE ZEIZINGERTeam Leader Hot-dip Galvanizing Line 8, Auto Division | ThyssenKrupp Steel AG, Dortmund

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18|

of 1% results in a liquidus temperature of approximately 405 C. The

formation of the intermetallic phase Mg2Zn11 is suppressed by rapid

cooling, and a metastable eutectic structure of Zn-Mk and MgZn2is

formed. This structure has also been determined in the applied

coatings I Fig. 2 I.

Corrosion mechanism of ZMg coatings

The protective effect of the ZMg EcoProtect coating is characterized

by the interaction of several mechanisms:

ZMg is at least as effective as conventional zinc coatings in providing

cathodic protection of steel, as demonstrated by various studies.

Extremely dense, compact and ordered top layers are formed

during the blank corrosion of ZMg EcoProtect. These layers have

a significantly better barrier effect and thus a greater degree of

protection against corrosive attack than conventional zinc and zinc

alloy layers I Fig. 3 I. The higher degree of order and the morpho

logy of the resulting top layers lead to slower dissolution of the

zinc and thus to an extension of the protective effect.

ZMg is also seen to provide significantly better protection at un-

protected cut edges, exposed iron surfaces or damage sites. This

improved corrosion behavior is, according to the current stateof knowledge, also due to the formation of a top layer on the free

iron surface. Hydroxyl ions react with zinc and magnesium ions

in a chemical precipitation reaction to form a top layer which is

precipitated on the open cut edge I Fig. 4 I. The top layer deposited

in this way displays a dense, ordered structure and causes a delay

in cathodic oxygen reduction on the iron, which in turn results in a

minimization of the anodic reaction step the dissolution of the

zinc. As a result, a protective effect that is at least the equivalent

of that of todays established products is achieved, even with sig-

nificantly lower zinc coating weights I Fig. 5 I.

Product ZMg EcoProtect

Numerous production campaigns have shown that ZMg EcoProtect

can be reproducibly manufactured with high quality. The new product

can be supplied in strip thicknesses from 0.4 to 3.0 mm and widths

from 600 to 1,650 mm, though not all combinations of thickness and

width are available. The available coating weights are between 60

and 350 g/m in the case of surface finishes A (standard surface)

and B (improved surface) and between 60 and 255 g/m in the case

of the finish C (best surface) as well as structural steel and deep-

drawing grades. The new flat steel product is also available in an

oiled version.

Fig. 1| Galvanizing a hot-rolled sheet in FBA 8 in Dortmund Fig. 3| Corrosion protection of ZMg EcoProtect in comparison with other metallic-coated

sheet steels in salt spray testing

Fig. 2| Coating formation of ZMg EcoProtect

Testing

timetofirstredrust[h]

Coating thickness[m]

1.000

800

600

400

200

0

0 5 10 15 20 25

AZ

ZA

Z

ZMg EcoProtect

10 m


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ZMg EcoProtect can also be provided with chemical passivation

or sealing to further improve the corrosion characteristics. These sur-

face treatments are also a good foundation for subsequent painting.

ZMg EcoProtect has been tested in a range of forming experi-

ments; it can be processed without problems and can be regarded

as equivalent to hot-dip galvanized coatings (Z). The suitability for

welding of ZMg EcoProtect is also comparable with that of con-

ventional zinc materials.

Automotive applications

ZMg EcoProtect is suitable for internal components in corrosion-

threatened areas of the vehicle bodywork, such as the floor structureor doors and hatches. The coating weight can be reduced or main-

tained in order to improve corrosion protection. At higher coating

weights, it is even possible to substitute todays conventional batch

galvanizing, especially for chassis components without weld seams,

which in turn produces substantial cost savings for the customer.

Further development is taking place with the objective of making ZMg

EcoProtect suitable for outer skin applications.

In the meantime, in addition to general abrasion and friction

tests, numerous real components have been manufactured to test

the forming characteristics. To date, the forming operations have

been successful. I Fig. 6 I shows a comparison of the abrasion values

for various coating variants typical of the automotive industry. The

very good forming behavior of ZMg EcoProtect can clearly be seen.

The electrode life determined for ZMg in resistance spot weldingcorresponds to that of conventional zinc materials.

ZMg EcoProtect new coating for high-end corrosion protection |19

Fig. 5| Corrosion characteristics in salt spray testing according to DIN EN ISO 9227 of ZMg EcoProtect

and Galfan

ZA each with Cr(VI)-free pretreatment, universal primerand polyester painting, nominal coating thickness 25 m

Fig. 4| Schematic corrosion reactions of painted, hot-dip galvanized and hot-dip alloy galvanized sheet steel

ZA 185 g/m2 ZMgEcoProtect 60 g/m2

Creep after 720 h salt spray testing

Paint

Zinc

Steel

Red rust

Zn

Zn2+

e-

OH-

Fe Fe2+

O2

Stable surface layer

Zn, Mge-

OH- O2

Paint

ZMg

Steel

Zn2+, Mg2+

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20 | ZMg EcoProtect new coating for high-end corrosion protection

Industrial applications

ZMg EcoProtect can also have interesting application possibilities

for profiles, such as garage door accessories, cable ducts, profiles

for windows and interiors, scaffolding planks, plant supports and

doorframes. The new product can also be used for the manufacture

of housings for small motors. The application example of a trailer

fender I Fig. 7 I shows the special protective effect of the ZMg Eco-

Protect coating and a Cr(VI)-free seal. Despite the significantly lower

coating thickness of ZMg EcoProtect, it results in a significantly

improved corrosion behavior in comparison to hot-dip galvanized

sheet steel.

Coil-coating application

ZMg EcoProtect is an excellent substrate for organic coil-coated flat

steel grades. The positive properties with respect to corrosion resist-

ance are substantially reinforced by the additional organic coating.

The known coating materials such as polyester and polyvinylidene

fluoride (PVDF) can be used almost without reservation. It is notable

that especially good results were achieved using Cr(VI)-free materials.

Even in the case of reduced coating thicknesses as compared to

conventional substrates, the corrosion resistance is better I Fig. 8 I.

Paint creep at cut edges and at points where the coating is damaged

is significantly reduced, particularly in the case of long-term corrosive

stresses. The effects of a corrosive stress on cut surfaces is also

less I Fig. 9 I. In addition to the special corrosion characteristics, the

coil-coating material also possesses good forming properties. This

made it possible to sustainably extend the spectrum of organic coil-

coated PLADUR flat steel grades. The good properties of this pro-

duct on the basis of ZMg EcoProtect with a reduced coating weight

of 130 g/m in comparison with e.g. hot-dip galvanized sheet steel

Abrasionra

tein[g/m]

KB ZE ZEP ZMg Z ZF

2,5

2

1,5

1

0,5

0

Abrasion

Fig. 6| Forming characteristics of ZMg EcoProtect and other typical coatings; abrasion in strip drawing tests

KB: ungalvanized sheet steel,ZE: electrolytically galvanized sheet steelZEP: electrolytically galvanized and

prephosphatized sheet steel

ZMg: hot-dip coated zinc-magnesiumsheet steel ZMg EcoProtect

Z: hot-dip galvanized sheet steelZF: galvannealed sheet steel

Fig. 7| Trailer fender in salt spray testing according to DIN EN ISO 9227 (test duration: 264 h): ZMg EcoProtect, 130 g/m, in sealed surface finish,Cr(VI)-free (left), hot-dip galvanized sheet, 280 g/m, in sealed surface finish, Cr(VI)-bearing (right), sheet thicknesses 1 mm

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ZMg EcoProtect new coating for high-end corrosion protection |21

Fig. 8| Relative corrosion characteristics of ZMg EcoProtect (ZMg) in comparison with conventional,metallic-coated sheet steel (Z and ZA) respectively with a polyester coating, nominal coating thickness

25 m, after 360 h in salt spray testing according to DIN EN ISO 9227

ZMg 130 + PVDF 25Relativecorros

ionresistance

(cutedgesa

ndscoring)

ZMg 130

AZ 185

ZA 255

Z 275

Without polyester painting SPTest duration: 1,000 h

ZMg: Zn-Mg hot-dip galvanized, AZ: Galvalume, ZA: Galfan, Z: hot-dip galvanized

with a coating weight of 275 g/m have been confirmed in an expert

opinion from the University of Karlsruhe. The material was rated in the

highest corrosion protection class according to DIN 55928-8. The

Deutsche Institut fr Bautechnik in Berlin (DIBt) has granted general

building code approval for use of the organic coil-coated flat steel

grade on the basis of the substrate ZMg EcoProtect with a coating

weight of 130 g/m in the manufacture of thin-walled components.

Summary and outlook

ZMg EcoProtect creates substantial customer benefit thanks to

improved corrosion protection, also in the area of cut edges. The

advantages are clearly apparent in the case of long-term, repetitive

corrosive stresses. The reduction in paint creep and the improved

resistance in the flange areas of automobile bodywork offer exem-

plary evidence of the good corrosion characteristics. In comparison

with previous zinc coatings, ZMg EcoProtect offers at least com-

parable processing properties when forming and joining and is well

suited for subsequent coil-coating applications. Typical automotive

painting is also possible.

ZMg EcoProtect is a high-quality, economically attractive product

and an alternative for highly effective corrosion protection in various

applications. The product has now been manufactured in large volumes

on a number of production lines and is being used in production in

addition to being tested in development partnerships with customers.

Test duration

ZA 255 + PVDF 25

Z 275 + PVDF 25

Without polyester painting SPTest duration: 384 h

ZMg 130 + SP 25

AZ 185 + SP 25

ZA 255 + SP 25

Z 275 + SP 25

Fig. 9| Cut-face corrosion after a salt spray testing (DIN EN ISO 9227) of sheet steel (thickness approx. 0.6 mm)

Coatings Coatings

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22|

|EcoSpace cockpit support structure

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State of development

Initially, it may have sounded unusual that a specialist plastic pro-

cessor and a steel company would join forces to develop a cockpit

support structure which would differ fundamentally from all existing

designs. However, this ambitious plan paid off for everyone involved,

as the resulting cockpit is a top performer that is also lighter, less

expensive and more flexible than conventional production solutions.

In addition, all of the project partners benefited from the balance of

the material mix and value added. A prototype of the jointly developed

structure was first unveiled at the 2007 IAA International Motor Show

in Frankfurt, after which it was also presented to the various auto-

makers on site. It has been clearly demonstrated that the cockpit is

suited for production use, and the first bilateral development projects

for production implementation are ramping up.

Successful multi-company cooperation

The cooperation partners complement one another optimally. While

ThyssenKrupp Steel has expertise in steel materials and their use in

automobiles, ThyssenKrupp Presta is a system supplier for steering

columns, and Johnson Controls has extensive experience in plastics

and vehicle interiors as a system partner for instrument panels and

cockpits. The projects success is the result of the partners joint

recognition of the fundamental principle that the right material be used

for each functional requirement without losing sight of the systems

total cost and weight. The companies have developed an open,

trusting and productive partnership that can serve as a best practice

example for future cooperative ventures among multiple companies.

Low-cost lightweight construction using steel

The EcoSpace cockpit weighs 20% less than conventional structures.

In addition, prime costs can be reduced by up to 15%. Thanks to

the structures natural frequency of 46 Hz, the cockpits stiffness

comfort is considerably higher than that of conventional systems with

a frequency of 39 Hz. Sophisticated simulations of the complete

cockpit structure show that the optimized composite of plastic and

metal is so homogenous in its structure that the new cockpit passes

all international safety and crash tests with flying colors. Regardless

of whether a collision occurs on the side containing more steel or

plastic, the EcoSpace cockpits crash behavior is the same on both

the driver and the front passenger sides.

Multiple interface development

By considering the system as a whole, the interior, body structure

and steering systems experts were better able to meet the single

cockpit components requirements as well as the overall performance.

The aim of these efforts was to jointly develop an integrated concept

for the cockpit structure that would set new standards by combining

the benefits of the various conventional solutions.

In the 1970s, the automotive industry began using so-called cross

car beams, which were meant to enable the companies to completely

preassemble all cockpit assemblies and thereby reduce manufac-

turing costs. As the development of automobiles progressed further,

automakers focused increasingly on meeting the rising demand for

more comfort. The manufacturers are therefore increasingly concen-

trating their efforts on creating noticeable comfort features whichhave a big impact on customers purchasing decisions. Besides design

|23

EcoSpace cockpit optimum interactionbetween plastic and steel in the vehicle interior

In cooperation with Johnson Controls, ThyssenKrupp has developed a cockpit support structure known

as EcoSpace that is an economical lightweight hybrid composite structure of steel and plastic, with a

steel frame located only on the drivers side. The new construction has a crash performance comparable

to that of conventional cockpit support structures while featuring 18% greater stiffness and a weightreduction of more than 20%.

DIPL.-ING. MARTIN HINZ Manager Process Innovation, Sales/Engineering | ThyssenKrupp Steel AG, Dortmund

DIPL.-ING. PETER SEYFRIEDManager Technology Management, Sales/Engineering | ThyssenKrupp Steel AG, Dortmund

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aspects such as the easy reachability of the controls, these features

include comfortable steering. This refers to low-vibration or vibration-

free steering that can be achieved through the high dynamic stiffness

(first natural frequency of an oscillating system) of the steering column

and the cockpit support structure. To achieve a high level of steering

comfort, the cockpit support structures first natural frequency should

be substantially higher than that of the engine-transmission unit.

Todays cockpits are filled with numerous assemblies that are

designed to enhance comfort. Air conditioning and navigation systems

are now considered standard equipment for many vehicles. And since

Germans spend an average of one-and-half hours in their vehicles

every day, infotainment systems are becoming increasingly importantin automobiles as well. As a result, a cockpit can weigh between 60

and 120 kg, depending on the vehicle segment and the equipment

the cockpit contains. Prompted by the current debate concerning CO 2

emissions, automakers are now checking the potential for reducing

weight within the cockpit. A study has shown that the cockpit support

structure plays a significant role in this regard, as it accounts for

about 25% of the cockpits total weight. Because many components,

such as air inlet ducts, have been optimized over a period of many

years and therefore no longer offer any significant potential for further

weight savings, the question arises as to how much of the cockpit

should consist of structural components. The analysis showed that

the cockpit needs a high level of dynamic stiffness primarily in the

area of the steering column. But if structural considerations do not

require the cross car beam to extend across the entire width of the

cockpit, this component can be reduced by more than half.

Technical highlights

The EcoSpace cockpits structure is extremely innovative. A total of

four new patents I Fig. 1 I have been registered for this development,

for which the patented T profiling technology (cf. ThyssenKrupp

techforum, Issue 1/2007) is also used.

Patented hybrid of plastic and steel

While the innovative steel structure on the drivers side is primarily

responsible for mounting the steering column, the plastic structure

that extends across the entire cockpit integrates the air ducts for the

defroster and the air conditioning, as well as the connection to the

front passenger airbag and the back of the glove compartment. An

essential requirement for high-quality hybrid designs is that they

meet all of the demands that a plastic-metal composite can face.

These include the high mechanical strength of the joints as well as the

use of proven technologies for industrial manufacturing processes.A two-stage process is used to create the high-strength, rigid hybrid

connection of the plastic structure and the steel frame. In the first

step, plastic is injection moulded around steel inserts. Because of the

nature of the material used, the metal layer is subsequently joined to

the steel structure using a method that is free of thermal distortion

such as laser welding.

Patented expansion element optimizes crash properties

Side impacts give rise to very high peak loads that are passed into

the cockpit structure through the bolt points on the vehicle body.

As a result, the connection plate between the steel frame and the

plastic structure was designed in such a way that peak loads could

be cushioned by an elastic expansion element, yet would neverthelessensure a sufficiently high buckling load level in the event of a crash.

Steel T crossbeam optimized in terms of stiffness and package

A key feature of the EcoSpace cockpit is the T crossbeam I Fig. 2 I,

which serves as the interface to the steering column and the vertical

strut. To meet the demand for high comfort, high dynamic stiffness

is required at points where masses are focused, such as the steering

column connections. Stiffness is significantly increased by using a

linear weld between the crossbeam and the outside edges of the

vertical strut. The engineers took all stiffness-related factors such the

material, shape, production technologies and sheet thickness into

account while designing the crossbeam in line with the needs of

the overall package. They created a stress-optimized T crossbeam

that has a cylindrical shape where it connects to the A-pillar. After

expanding into a cone, the crossbeam has a rectangular cross-

section at the point where the steering column is mounted in order

to make assembly easier.

Patented optimized steering column connection

The EcoSpace cockpits steering column is bolted directly to the T

crossbeam I Fig. 3 I. The crossbeams cross-section is stabilized by

two sleeves, making it possible to achieve a tightening torque of

approximately 18 Nm. Whereas the benchmark design requires a

total of seven parts to mount the steering column, the EcoSpace

cockpits patented concept makes assembly much easier, since it

only needs two bolts and a single assembly direction. Not only does

this save costs, it considerably reduces the possible fault rate.

Tripod concept with patented vertical strut

The EcoSpaces design is brilliantly simple and therefore much more

flexible than all existing concepts. The steel support structure consists

primarily of the T crossbeam already described. On the drivers side,the crossbeam is connected to the A-pillar. In the vehicles center it

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Arrangement for connecting the steering column

of a motor vehicle (steering column connection)


EcoSpace cockpit optimum interaction between plastic and steel in the vehicle interior |25

Fig. 1| Degree of innovation in the EcoSpace cockpit

Vehicle components with hybrid structure

(steel-plastic composite structure)

Support element for a cockpit crossbeam

(single-piece vertical strut)

Hybrid crossbeam

(expansion element with

position in the cockpit)

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is connected to a vertical strut, which in turn is bolted onto the cowl

and the center tunnel. Via these three connection points, the structure

forms a so-called tripod. In addition, the vertical strut that extends

from the cowl to the center tunnel ensures a harmonious flow of forces

that enables the systems lightweight construction potential to be

fully exploited.

Design flexibility

The elimination of the usually complex conventional steering column

connection creates additional packaging space for occupant protec-

tion systems on the drivers side, Moreover, the innovative cockpit

structure opens up completely new possibilities on the passengerside for automakers I Fig. 4 I, as the absence of the cockpit support

structure opens up completely new design opportunities in this area.

Practically the only limits placed on the imaginations of vehicle interior

designers are technical considerations such as the fact that large parts

of the front passenger area are today used for functional elements

like asymmetrical air-conditioning units. However, the increasing in-

tegration of functions, for which the EcoSpace cockpit is predestined,

will increase design freedom in the future. Savings can be made in

all areas except safety. The revolutionary EcoSpace cockpit is as safe

as any conventional system, despite the fact that its crossbeam does

not link the A-pillars across the full width of the vehicle, as is the case

with other alternative cockpits currently on the market.

Economical solution with high customer value

One of the main goals of the cockpits developers was to create

a pioneering lightweight solution that would be economical and

customer friendly, which is why they put great store on integrating

functions and processes. Two approaches were used to integrate

functions: firstly by incorporating several connections into the

plastic support structure, and secondly by developing a one-piece

vertical strut.

As an alternative, the newly developed cockpit crossbeam can

also be manufactured by means of hydroforming. Starting from

a conical tube, this would involve strains of up to 38%. After pre-

forming, the tube must therefore undergo intermediate annealing

before it can be formed to its final shape. Hydroforming requires

a total of seven process steps. In T profiling technology, a shaped

blank is formed into a hollow section and the profile edges are then

laser welded without the need for filler materials, i.e. only two process

steps are required to complete the crossbeam. Due to the extensive

process integration achieved by this technology, the cockpit crossbeam

can be manufactured at a much lower cost than it would be the casewith hydroforming.

Fig. 3| Steering column connection concept for optimized assembly and flow of forces

Fig. 2| Crossbeam with perforated plates

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EcoSpace cockpit optimum interaction between plastic and steel in the vehicle interior |27

increased from 1.4 mm to 1.8 mm for the stamped and welded cross-

beam. A cost comparison revealed that a T cockpit crossbeam can

be manufactured more economically than a comparable stamped and

welded crossbeam if annual sales exceed a certain level.

Outlook

Future cockpits will look different to those of today. They will be

differentiated even more strongly into separate modules for the

driver, front passenger and center areas. All of the key functions

needed to operate an automobile will be integrated into the drivers

side of the cockpit, while all of the comfort-enhancing elements,

such as air-conditioning and entertainment systems, will be concen-trated in the central module. In the future, the new design freedom

that the EcoSpace cockpit creates particularly in the front passenger

area will allow automakers to produce completely new offerings. It

will be possible to set up comfortable workstations in front of the

front passenger seat or install large-format infotainment screens to

provide passengers with relaxing entertainment. In addition to in-

corporating special functional elements for athletic or handicapped

users, designers will also be able to include features for various

professions or different age groups. Whether used for new, easily

accessible stowage areas of previously inconceivable dimensions,

safe transport areas for one or even two child seats, or a built-in

refrigerator to feed an entire family while on the road the EcoSpace

cockpit has the space, designers just have to come up with the ideas.

In addition, the number of parts was halved compared to the

benchmark design, while the total weld length was reduced by as

much as 60%. Besides the aforementioned factors relating to manu-

facturing costs, the evaluation of customer value is also greatly

impacted by the systems lightweight construction performance

(weight reduction multiplied by performance value). Any improve-

ments in this regard lead to performance values >1, while any

deterioration reduces the value to

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|Robot handling at the worlds first laser decoating plant for metallic coatings at ThyssenKrupp Tailored Blanks

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Tailored blanks in hot stamping

In collaboration with Audi, ThyssenKrupp Tailored Blanks has successfully developed and integrated

into production processes a new manufacturing technology for tailored blanks for use in hot stamping.

The work was carried out within one year. The new technology represents the worlds first application

of the product tailored blanks in hot stamping along with plant engineering that is currently unique.

These tailored blanks offer users all the advantages of the previous areas of application and maximumprocess reliability. Different steel grades and sheet thicknesses can be welded together. In this way, the

new product supports the customer in achieving lightweight construction and thus also in attaining envi-

ronmental objectives. At the same time, the automakers production costs can be significantly reduced.

DIPL.-ING. JRG MAASHead of Sales/Senior Manager Sales | ThyssenKrupp Tailored Blanks GmbH, Duisburg


Tailored products

Tailored products have been successfully used in the area of body-

work technology by all automakers worldwide for years. Tailored blanks

are steel sheets of different steel grades and sheet thicknesses that

have been laser-welded together before forming. European automobile

manufacturers alone accepted delivery of approximately one million

tons of tailored blanks in 2007.

The increasing requirements in terms of crash behavior and the

associated application of ultrahigh-strength steel grades and new

manufacturing techniques have led ThyssenKrupp Tailored Blanks,

along with the customer Audi in Ingolstadt, to jointly investigate and

implement the use of tailored blanks in hot stamping as part of the

project Audi B8.

Application in hot stamping

Hot stamping bodywork components involves heating steel sheets

to a temperature of 880 C to 950 C. The sheets are than formed

in a cooled forming die and cooled at a rate of 27 C/s. An extremely

strong martensite structure develops in the steel. This technology can

be used to increase the strength of manganese-boron steels from the

starting level of approximately 500 MPa to around 1,500 MPa. These

extremely high strengths cannot be attained with the steel grades used

to date in conventional deep drawing. The process of hot stamping

and the temperature changes are shown in I Figs 1 and 2 I.

The first internal studies for tailored blanks in this area initiallylooked at un-coated manganese-boron steel (MBW 1500). The back-

ground to the initial experiments were suggestions for optimization

of material utilization at the customers. The objective of the initial

experiments was to demonstrate that the weld achieved at least the

same strength after hot stamping as the base material used, in this

case the steel grade MBW 1500. To this end, sample components

were welded together before being subjected to the heat treatment

normally used in hot stamping. I Fig. 3 I shows the hardness profile

in the cross-section of the sample component before and after hot

stamping. It can clearly be seen that there is no reduction in hard-

ness in the region of the weld. This demonstration reinforced the

development team in their intention to continue promoting the pro-

duct for application in hot stamping.

In the further course of the studies, Audi in Ingolstadt expressed

the desire to use tailored blanks for hot stamping. The main reason

for this was the requirement to make use of two different steel grades

for crash-relevant components such as the B-pillar or the rear side

member. The combination of different steel grades is a classic appli-

cation for tailored blanks. To date, exclusively manganese-boron steel

has been used for hot stamping. The combination of MBW 1500

with another steel grade is unprecedented. The development depart-

ments requirements for the two steel grades were: elongation A80 >

15% and tensile strength > 500 MPa. This requirement describes a

steel that behaves in a more ductile fashion in the event of a side or

rear-end impact.

Comprehensive experiments were carried out in collaboration withthe Applications Technology department at ThyssenKrupp Steel. As

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30 | Tailored blanks in hot stamping

A characteristic cross-section is shown in I Fig. 4 I. In particular,

the inclusions in the weld seam represent weakenings. The first

approach to a solution involved carrying out welding experiments in

which the coating of the tailored blanks was mechanically removed

along the weld edges. The weld samples were then hot stamped in the

Dortmund test facility and analyzed in the Metallography department

of ThyssenKrupp Steel. The cross-sections showed the expected result

I Fig. 5 I. No coating fragments (white inclusions) are to be seen in

the weld seam. There is also no coating in a small area < 0.2 mm

on the upper and lower sides adjacent to the weld. No anomalies

resulting from melted coating could be determined. Working together

with the customer, it was determined that the coating in the area of

the weld seam is to be removed in the future. A maximum removal

width of 1.0 mm was specified.

part of this work, it proved possible to model the customers process

using the hot stamping test facility in Dortmund. The customer decided

on the single-step hot stamping process I Fig. 1 I. This process requires

the steel to have a hot-dip aluminized coating which protects against

scale formation and corrosion. At the conclusion of the studies, the

steel grade H 340 LAD showed the desired properties.

Once the steel grades to be used had been jointly determined,

further experiments were carried out with respect to forming charac-

teristics, weldability and strength after hot stamping. These exper-

iments showed that the hot-dip aluminized coating layer had melted

during the laser welding process. A mixture of iron, aluminum and

silicon had solidified in the weld after laser welding. Solid solutions

were forming in the weld and an intermetallic phase on the cover

and root passes.

Fig. 2| Temperature changes during hot stamping

Fig. 1| Schematic representation of hot stamping

Cold forming Heating to 850- 950 C

under an inert gas atmosphere

Die quenching

in the cold die

Cutting component using

cutting tool and/or laser

Sandblasting

Austenitizing

950 C

830 C

730 C

150 C

240 s 240 s 10 s 20 s 330 s

1 Heating to target temperature

2 Aloying of the surface

3 Transfer + die closing

4 Hardening in the die

(cooling rate > 27 C/s)

5 Cooling to room temperature

outside the die

Die closed

Removal from furnace / Furnace temperature

Removal from die/ die temperature

Room temperature

1 2 3 54

Heating to 850 - 950 C

innert gas atmosphere

Die quenching

in the cooled tool

Cutting component using

cutting tool and/or laser

Indirect hot stamping/MBW (two-stage)

Direct hot stamping/MBW + AS150 (single-stage)

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Tailored blanks in hot stamping |31

Following from this work, a manufacturing process was to be

developed for mass production and its suitability demonstrated.

To accomplish this, a total of three processes using mechanical

methods two using lasers, and one using inductive heating were

reviewed. The time available from the first idea to the start of volume

production was one year.

With regard to reproducability and suitability for volume production,

the process using Q switched lasers proved to be the economic and

technical optimum. All processes were tested in the test facility and

Metallography department and finally approved by the customer.

The Q switched solid-state laser is a diode-pumped Nd-YAG laser.

The Q-switching is carried out with a frequency of up to 15 kHz. The

laser has a power of 500 W.

A new line concept appropriate to the power of the laser was

developed. This includes a conveying concept which enables thepower of the laser to be fully used. I Fig. 6 I illustrates the line con-

Area with removeed coating

No inclusions

in the weld

Solid solutions

Cover pass with intermetallic phase

Root pass with intermetallic phase

Fig. 6| Layout of the worlds first laser decoating plant: passage of the starting blanks

Fig. 4|Cross-section with coating

HV

0.1

Distance [mm]

Fig. 3| Hardness profile before and after hot stamping

600

500

400

300

200

100

0

0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

Hardness

Hardness profile through laser welding

Area with removed coating

before hot stamping after hot stamping

Weld seam

Fig. 5| Cross-section with removed coating

cept. The blanks are guided through the line in a continuous process.

The coating is removed from the weld edges of the tailored blanks

by the laser at speeds of approximately 8 m/min. To guarantee

quality, a new sensor has also been developed for online quality

control of the process.

Outlook

Automakers will make increasing use of tailored blanks for hot stamp-

ing in the area of crash-relevant structural components in the coming

years. Thanks to the newly developed technology from ThyssenKrupp

Tailored Blanks, they can now be used independently of the diverse

coating types. A rapid increase is already apparent. In the last two

years, the volume has risen to a total of 20,000 t with strongly in-

creasing demand on the customer side. Further applications will

follow in the area of side panel and door inner assemblies.

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|MPT Multi-purpose tailgate

32|

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|33

Background

The desire to go for a relaxing ride on the bike after a tough day at

the office is often dampened by the fact that stowing the bike in the

vehicle can be extremely arduous and is sometimes not even possible.

Nevertheless, if the difficulties are overcome and the bike ride is

accomplished, in some cases on dirt trails, the bicycle is often grimy

and has to be stowed in the vehicle again in that condition. This can

quickly diminish any interest in more cycling.

The new multi-purpose tailgate (MPT) provides a remedy; it gets

the enthusiastic cyclist ready to go in only two minutes. The bicycle

rack system swings out of the innovative tailgate, and the bicycles

are loaded onto it with very little effort. Simple opening and

loading options on vehicles are essential these days because of the

wide variety of ways they are used in professional and leisure activities.

These considerations formed the basis for an intensive exchange ofideas with partner Webasto, which brought to the topic its experience

with door- and roof-opening systems. Over 20 ideas were discussed,

and the idea that appeared most reasonable was initially simulated

on a computer and later implemented in a real vehicle. Production

scenarios were then calculated, and potential prices were determined.

The result is impressive: a tailgate module with an integrated rack

system accommodating a variety of cargo, e.g., bicycles, snow-

boards, skis or a luggage box, optionally available with a rear window

opened separately or with a keyless open feature. A prototype of

the jointly developed tailgate solution was integrated into a VW Passat

and exhibited for the first time at the International Motor Show IAA

2007. The feedback from the auto manufacturers was extremely

positive. Following initial customer presentations at the manufacturers,

the implementations are now being carried out on their respective

vehicles with the aim of supplying customers with the tailgate module

in the future.

The needs of customers play a decisive role in creating innovative product solutions for future generations

of automobiles. Following customer surveys, ThyssenKrupp Steel, ThyssenKrupp Metal Forming and Webasto

worked together closely to develop the multi-purpose tailgate. The design of the flexible tailgate module

implemented in the physical prototype features maximum ease-of-use, the highest degree of functionality

and flexibility and optimal use of the materials involved.

DIPL.-ING. RALF SNKELTeamleader Product Innovation/Projects, Sales/Engineering | ThyssenKrupp Steel AG, Duisburg

Multi-purpose tailgate MPT a flexibletailgate module with integrated rack system

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34| Multi-purpose tailgate MPT a flexible tailgate module with integrated rack system

needed. A second license plate is also integrated into the multi-

purpose tailgate, in addition to a theft-protection mechanism, the

obligatory extra lights and the bicycle racks. Little effort is required

for loading; no tools are needed.

Other uses of the MPT

The new multi-purpose tailgate is more than just a new type of tail-

gate with an integrated bicycle rack. Because the development team

of Webasto and ThyssenKrupp Steel created a modular design, the

automakers can integrate a tailgate suitable for upgrade to the MPTinto their normal production line without changes to the body-in-white

and modify this tailgate according to customer preferences with little

effort. The basic version of the MPT is no more expensive than a

standard tailgate and is designed in such a way that the extra parts

and reinforcing elements needed can be included in the body-in-white

phase with only minor added costs.

The diverse selection of attractive special accessories, which can

be combined in almost any way desired, includes a rear window that

folds out separately, an integrated rack system for bicycles, snow-

boards or a luggage box; an automatic opening mechanism for the

tailgate, also available in an optional keyless version; and an inte-

grated anti-trap function I Fig. 2 I.

End customer as a driver of innovation

Manufacturers who want to offer their customers the new functional

extensions as special accessories will profit from a two-year head

start in know-how and the certainty that there is a real demand for

all these optimal features. This is evident from the results of a large-

scale survey of end customers which was carried out at the start of

the development project. The survey asked owners of station wagons,

compact-class vehicles and vans to vote on 20 different ideas for

innovations regarding the topic tailgate. The following results were

tied as the innovations most desired by customers:

Integrated cargo rack, especially for bicycles,

easier opening and closing (e.g. electric), ideally when

approaching the vehicle,

rear window that is opened separately as well as

ability to open the tailgate when cargo is loaded.

In addition to the evaluation of the technical contents, an accepted

target price lev

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