SSAB-The Steel Book 2002

The Steel Book.The Steel Book.

Production: Information Office, SSAB Tunnplåt AB, Luleå

Text: Vidén information AB

Translation: Ewa Hjelm

Proof-reading: Mark Wilcox

Design: Formidabel

Illustrations: Mediagrafik & illustration

Photo: Lars Vaksjö, Karin Larsson/SSAB Tunnplåt AB, Per K Olsson, Volvo’s picture library

Print: Luleå grafiska, 2002

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Steel for tough demands.

DicksonPSC

Tibnor

SSABSvenskt Stål AB

Plannja

SSABTunnplåt

Luleå, Borlänge

SSABOxelösund

Foreignsales

companies

STEEL OPERATIONS

FURTHERPROCESSING TRADE

SSAB Tunnplåt is part of the SSAB Group.SSAB Tunnplåt is the largest manufacturer of strip steel

in the Nordic region and one of Europe’s leading developersof high-strength strip steels.

SSAB Tunnplåt has ore-based steel production in Luleåand strip steel manufacture in Borlänge.

This brochure focus on the production in Luleå.

SSABHardTech

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Steel is the most useful metal in the world. No othermaterial can meet such a great variety of require-ments. Steel is one of the basic ingredients in thedevelopment of industry and the whole of society. We come in contact with it everyday – in transpor-tation, sports and leisure, in the kitchen, in schools,hospitals – everywhere.

The world’s most widelyused structural material.

Steel has to have different properties for different applica-tions. Cars need strip steel with a good formability and an attractive surface finish. Auto components, such as side impact beams and built-in children’s safety-seats,require high-strength steels that enable the manufactureof strong, yet thin and light constructions. Washingmachines need a light, durable steel sheet that stands upto wear. Microwave ovens require sheet with special coatings.

The ice blade on a snow plough must be hard and wear-resistant. Steel sheet that is to be bent into varioussections for roofing and facing sheet must be ductile, so that it does not crack when it is bent. Just look around.You’re sure to find many more applications, with diffe-rent demands, in which steel is used.

The addition of carbon is required to make hot metalfrom iron ore. In that process carbon dioxide, one of thegreenhouse gases, is formed. Iron and steel productionalso results in other emissions to the air, water and soil.Reducing emissions and limiting environmental impactare important tasks for SSAB Tunnplåt in Luleå.

Since 1980 emissions of dust have been halved and theemission of sulphur has been reduced by 85%. During thesame period ammonia and phosphate emissions werereduced by between 80 and 90%.

SSAB’s main environmental objective during the1990s has been to reduce emissions to the air and water.Other important aspects of the environmental effort havebeen source separation, increased recycling of residualproducts, life-cycle analyses (LCA), environmental pro-duct specifications, environmental management andrestricting the use of harmful chemicals.

Future efforts will involve further development of raw materials, processes and products. The environment is a central aspect of all new capital expenditures.

SSAB regularly carries out environmental inspectionsin the open, investigating, for example, mosses, plants,fish and other aquatic life, leaks from waste deposits, noiseand dust content in the air. Certain tests are conducted ona weekly basis, others at intervals of some years. All resultsare reported to the environmental protection authorities.

An environmental management system is being intro-duced to systematize the environmental effort and meetcustomer requirements. The environmental managementsystem includes procedures and documentation that facili-tate survey and control over environmental work.

Extract from SSAB Tunnplåt’s Environmental Policy:”Within the Group, all operations shall be conducted ina resource-effective and efficient manner in respect ofthe use of raw materials, energy and other naturalresources. The commercial operations are based onenvironmental work which contributes to permanentand sustainable development of the use of steel insociety.”

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Making steel with concernfor the environment.All industrial manufacture has an impact on the environment. As long as society develops, steel will be needed. Steel that is scrapped is recycled – a practice followed since the Iron Age. However, society’s demand for steel cannot be met by recyclingalone. New steel must be produced from iron ore.

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The metallurgical processes of iron and steelmak

Coking plant

Coal is imported andtransported to Luleå frome.g. Australia, the USA andCanada. The coal is stock-piled in a storage area the size of twelve football fields.

Blastfurnace

Transportation to the steel plant

BOF converter

Scrap

IRON ORE BECOMESHOT METAL

RAW MATERIALS HOT METAL BECOMESSTEEL WHEN SULPHUR

AND CARBON AREREMOVED

Coal is heatedup for 18 hours,25% becomes gas and the restbecomes coke.

Pellets are produced from iron ore by themining company LKAB in Malmberget andKiruna. Every twenty-four hours, three trainloads of iron ore pellets are transported to SSAB Tunnplåt in Luleå.

Iron ore pellets, coke and limestoneare continuously charged into the blast furnace.

Hot metal is regularly tapped from the hearth of the blast furnace.The hot metal is transportedto the steel plant in a torpedocar. Slag is tapped into slagladles.

Desulphurizationis assisted by theinjection of calciumcarbide into the hotmetal.

Hot metal and scrap aremixed in the BOF converter,where oxygen is used to reducethe carbon content.

Oxygen

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king.

Oxygen

Argon gas

Alloys

RH

THE STEEL IS FURTHER PROCESSED

In the RH plant the steel is treatedunder vacuum toremove impurities.Extremely low carboncontents and a highdegree of purity areachieved.

At the CAS-OB station(ladle metallurgy) alloys are added and the temperature is adjusted.

Liquid steel is tapped into a tundishand then further down into themould, without interruption. The steelstrand is cooled and solidifies as it ispulled down into the strand guide sys-tem for subsequent cutting and marking.

The slabs are cooledand loaded onto a trainbound for Borlänge.

Alloys

Mould

Slabs are carried by rail to the hot strip mill inBorlänge for further pro-cessing. 3 or 4 trains leavefor Borlänge every day.

CAS-OB

LIQUID STEEL IS CASTINTO STEEL SEMIS

(SLABS)

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25% of the coal becomes gas which is carriedoff, cooled and cleaned. When the gas is cleaned,several compounds are removed. These are recove-red and then used as raw materials in the chemicalindustry for making products as different as perfumeand asphalt.

The coke battery consists of 54 coke ovens in a long row. Coal is heated in the narrow, closedovens. Volatile compounds and gases are distilledfrom the coal after about 18 hours of heating. Thetemperature is then over 1000°C and the coal hasbeen converted into coke.

Black coal becomes coke.

The finished coke is pushed out onto the quenchercar and is cooled with water. The large white cloudswhich can be seen in the sky above the SSAB plant every 15 minutes consist of steam from quenching.

Gas holder

Coke is required in the blast furnace to get iron from the iron ore. Coke is harder than coal. The coke lumps must be hard and porous,even at high temperatures, to allow reducing gases to pass up throughthe blast furnace. To ensure a supply of the right quality of coke andhigh-energy coke oven gas, SSAB Tunnplåt has its own coking plant.

Cleanedcoke-ovengas

Cleaned coke-oven gas is returnedfor heating coke ovens.

150o C

2 200o Ccoke burns

1 500o Chot metal is tapped out

1 400 - 1 800o Cthe ore melts

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Iron ore becomes hot metal.

Ore pellets and coke are continuouslycharged in layers into the top of theblast furnace. Here, limestone, variousadditives and residual products con-taining iron, such as dust, flue dust,etc. are also supplied. All this is re-quired, to get a hot metal with theright quality and a slag with the rightproperties. The slag binds impuritiesfrom the hot metal.

The layers of ore pellets are slowly pre-heated and reduced to metallic iron whichdescends slowly through the blast furnace.The temperature increases further down inthe furnace and the iron melts and dripsdown onto the blast furnace hearth.

Hot blast is heated air with extra oxygenwhich is blown into the blast furnace inlarge quantities to heat and reduce theore. The air is heated in brick towers (hot stoves) serving as heat exchangers. To heat the hot stoves cleaned gas from the blast-furnace and coking plant processes is used.

When the iron at the furnace hearth has reached a certain level, it is tapped into so-called torpedo cars. Liquid hot metal is tapped from a blast furnace about ten times every twenty-four hours.Hot metal is brittle and fragile and therefore unsuit-able for making products, since it can-not be forged. The hot metal mustbe further processed into steel.

The gas from the blast-furnace process is ledaway and cleaned and then used in the processes.

Coal powder isinjected togetherwith oxygen-enrichedair into the lower partof the blast furnace to add carbon andoxygen.

Blast air

The coke lumps are hard, even in the hottest part of the blast furnace. Gas is formed when oxygen leaves the ore. The gas passes up through the coke lumps.

To convert iron ore into iron, the oxygen content must belowered (the ore is reduced). This is achieved by heating,whereby the carbon atoms from coke and coal powder are combined with the oxygen atoms of the ore in a gasflowing up through the blast furnace.

Blast air

The interior of the blast furnace

Air intake

High-energygas

Torpedo car

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Hot metal andscrap becomesteel.

The hot metal arrives at the steel plant from the blast furnace in a torpedo car and is tapped into a hot metal ladle. The volume of hot metal which goes into a hot metal ladle is called a heat.

First, the hot metal is desulphurized.Calcium carbide is injected through a lancewhich is dipped deep down into the melt. A chemical reaction is thereby started in whichthe sulphur reacts with calcium and the com-pound is bound in a slag on the surface of themelt. At this stage, for each heat, operatorsknow the sulphur level that must be reached inorder to match the customer’s specificationsfor the finished steel.

After desulphurization theslag is drawn off the surface.

Hot metal becomes steel when the carbon content isreduced below 2%. The addition of alloys gives the steelexactly the composition and the properties desired by thecustomer. Steel for refrigerators must have different pro-perties than steel that is used for making bridge piers.

The slag is a residual productwhich is partly recycled.

Calcium carbide

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The desulphurized hot metal is pouredinto a BOF converter (Basic OxygenFurnace) together with scrap and the carboncontent is reduced, i.e., the iron is decarbu-rized into steel.

Other impurities, such as phosphorus andvanadium, are bound in a slag on the surface.The steel is tapped into a ladle and the slagremains in the BOF converter. At the same timeas the steel is tapped into a steel ladle, the prelimi-nary addition of alloys (different metals), as specifi-ed in the order, is made. The slag is poured overinto special slag ladles and most of it is re-used as raw material in the blast-furnace process.

Oxygen is required to lower the carboncontent.Gaseous pure oxygen is blownunder high pressure on the surface of themolten metal and the carbon content is re-duced to below 2%. The hot metal thenbecomes steel. The carbon content of thesteel is reduced to the right level to matchthe customer’s specifications. The carboncontent of most steel produced at SSABTunnplåt in Luleå is below 0.1%.

OxygenScrap

Alloys

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Ladle metallurgy.At this stage the steel in the ladle has to be further processed to satisfy demands on material properties inthe end product. There are hundreds of different steel grades. Steel grades are given their special properties in two different processes, called CAS-OB and RH. The analysis (the exact composition of different ingre-dients) and the temperature are finely adjusted.

In the RH plant a very clean steel with extremelylow carbon or hydrogen content is produced. The steel bath circulates under vacuum. Carbon reactswith oxygen and the compound, carbon monoxide isremoved. Hydrogen from the steel is also removed tothe gas phase. The values are carefully measured andare reduced to the levels specified by the customer.Steel grades with the lowest carbon content are extre-mely soft and are used for advanced pressing of partsfor cars, etc.

In the CAS-OB process a ceramic bell is lowered into the ladle.Argon gas is added from the bottom to stirthe steel bath and protect the steel from the oxygen in the air. To reach the desiredspecification of the heat, alloys are added in the form of metal pieces, or by using a long metal wire which is fed down into the liquid steel.

Here, 200 to 300 different steel grades are manufactured, all according to the requirements of different customers and fields of application.

Alloys

Alloys

Alloys

Vacuum valve

Argon gas

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Continuous casting into slabs.

The solidified steel strand is cut into 11-meterlengths, slabs, as it leaves the casting machine. Each slab has an identification number and is manu-factured for a certain customer and a certain purpo-se. The slabs are allowed to cool and then inspected.If required, surface cracks can be removed.

The steel is cooled and solidifiesslightly against the surface of themould and is pulled down into thestrand guide system. There, the steel isfurther cooled with water and solidifiessuccessively.

The slabs are loaded onto railway carsand transported to SSAB Tunnplåt’s rollingmills in Borlänge. Three or four trainloads ofslabs leave Luleå every day. The time fromorder to delivery of finished strip product tothe customer is 16 to18 days.

Ladle after ladle of molten steel is cast without interruption. This ispossible because the steel runs from the ladles into an intermediatereservoir, the tundish. From there, the steel is tapped into a mouldthrough a submerged nozzle at a regular speed. Great care is taken to register the steel grade being tapped into the tundish, so as to enable identification of each steel slab manufactured.

Ready-treated molten steel runs in a uniform flow via the tundish

down into the conti-nuous casting machine,which consists of a mould – a rectangularfunnel with adjustablesides – followed by astrand guide system.

Mould

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The coking plant produces raw materials of different kindsIn the coking plant 75% of the coal becomes coke and25% evaporates as gas. When the coke-oven gas is cleaned,a number of products are recovered which are then sold asraw materials for use in other manufacturing processes.Sulphur, for example, can be used to make sulphuric acidfor paper mills; tar is used for making pitch, tar oils, etc.,and crude benzene is used in plastics manufacture.

Recovery of iron in residual productsResidual products from the different process steps containferrous material. This iron is subjected to magnetic separa-tion and reintroduced into blast furnaces or converters.Dry dust and small iron fragments become briquettes in a briquetting plant. The briquettes, together with iron orepellets, coke and limestone, are part of the burden in theblast furnace.

Fewer and safer landfillsTo landfill waste means to deposit it in a controlled out-door ground site, once known as a dump.

The volume of landfilled waste per tonne of produced

steel at SSAB Tunnplåt continues to decrease. An evergreater amount of the residual products containing iron isreintroduced into the manufacture of hot metal and steel.Other material, which cannot become iron, is for exampleslag from the blastfurnace process. That slag can be soldand used as a filling material in road construction.

However, some waste must be landfilled. SSABTunnplåt has its own controlled landfill sites for thiswaste.

The material in the landfills is sorted to the greatestpossible extent for possible future recovery.

LegislationPublic authorities have issued about 50 environmentalconditions with which steel producers must comply.Various environmental tests and analyses are done everyday to ensure that these conditions are satisfied. They are made both by SSAB Tunnplåt’s own environmentallaboratory and by external companies and agencies.

Material cycle.At SSAB Tunnplåt in Luleå 4.5 million tonnes of iron orepellets, coal, scrap, limestone and alloys are used annually.Most of the solid material becomes steel. Only four percentbecomes residual products which are dumped. The rest isre-used in the process or is sold externally.

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About 20,000 households and a number of industriesand office premises in Luleå are heated by surplus gasfrom SSAB. District heating is also supplied to the hos-pital in Sunderbyn. In addition to the production ofpower and district heating, approximately 35 millionkilowatt-hours of steam are produced and delivered toSSAB Tunnplåt for use in the steelmaking process.Development and investments, for example in a coolantsupply line from the Lule River, mean that more andmore gas can be utilized instead of being burnt in theflare.

Energy flows.In the processes at SSAB Tunnplåt in Luleå large volumesof gas are formed. After cleaning, the gas is reused in themanufacture of coke, iron and steel. Excess gas is deliveredto LuleKraft – a combined power and district-heating plant – via a long gas pipe. LuleKraft uses the gas to produce district heating and electric powers.

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PeoplePlants and technical equipment need maintenance. Peoplealso need a certain ‘maintenance’. In order for co-workersto experience job satisfaction and develop in the work-place, there must be room both for commitment andchange. Individual discussions take place with all em-ployees at regular intervals and form the basis of personaldevelopment plans.

The Company Health Service works with, for example,exercise and medical check-ups as a preventive measure.SSAB Tunnplåt’s sports centre is open to all employeesand has a bowling-alley, weight training and many otherfacilities.

The Company Health Service also treats any medicalconditions that may have resulted from work.

The plantMaintenance includes all activities that are routinely carried out to keep the equipment in operation over time,as well as incidental repair or replacement of parts that aptto break down sometimes. Not only do small spare partsneed to be replaced. A single valve can weigh as much asfour tonnes.

About a third of all employees at SSAB Tunnplåt inLuleå work with maintenance.

Maintenance of machines and plant is both preventiveand planned, i.e. for example, cleaning and lubricationmust be done at regular intervals to ensure proper func-tion of equipment and parts must be replaced accordingto schedule, before they break down. The aim is for steelproduction to proceed without disturbances and stand-stills. Maintenance means keeping a step ahead at alltimes. All production facilities at SSAB Tunnplåt in Luleåare regularly inspected according to different schedules.Repairs due to an unplanned shutdown cost 100 to 1000times more than preventing or remedying the fault at anearly stage.

An efficient and preventive maintenance programmerequires knowledge and the commitment of all em-ployees.

• Operators may discover minor changes, such as an oil leak or a noise, and report it.

• Maintenance personnel who work close to the opera-tion measure, analyse and remedy faults.

• The personnel working with common maintenance do major work, such as replacing parts or doing repairs in a workshop.

• Purchasing and store personnel see to it that proper tools and spare parts are available.

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Man and machines.

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Europe’s leadingmanufacturer of high-strength steels.SSAB Tunnplåt Luleå is a relatively small steel plant. This enables us to develop special steel grades for the customer and to quickly adapt production, so thateven small quantities of a steel grade can be producedprofitably. The focus is on high-strength steels.

In Luleå we are good at producing steel with higher andhigher yield strength. This makes it possible to manufactu-re thinner and lighter designs. Since the steel plant inLuleå is small compared to those of competitors aroundthe world, special steel grades can be made in small quan-tities for customers with special requirements.

Example:A company in Barcelona in Spain sells turnkey warehou-se solutions, including buildings, shelves, automatic lifttrucks and computer systems. They wanted to offer theircustomers more efficient warehousing that occupies lessspace and requires fewer trucks. To achieve this, they had to build taller structures that would accommodate thesame volume of stored goods in a smaller area. The pro-blem was that the steel used for the shelving did not meettheir requirements, so they contacted SSAB Tunnplåt.

People from the marketing department in Borlängeand the steel plant in Luleå met with the customer todiscuss needs and demands. SSAB provided the solu-tion: a high-strength steel with the required width. Thiswas a steel grade with exactly the right carbon contentand exactly the right mix of alloys: a vanadium-alloyed,high-strength steel.

Now the company in Barcelona can build all of itswarehouses with high, strong shelf systems that are slender and space-saving.

CompetitivenessSmall-scale production, short delivery times and peoplewho are experienced in working with many special steelgrades are competitive advantages for SSAB Tunnplåt.Our customers appreciate short delivery times and highquality. In future we will be even more renowned for ourclose co-operation with customers. By producing new andunique steel grades we will be helping our customers toimprove their products even more.

About 800 million tonnes of steel are produced in theworld annually, of which just over 2 million tonnes areproduced at SSAB Tunnplåt’s plant in Luleå. Strong customer relations are important for future competitive-ness. The home market of Swedish steel is usually con-sidered to be within the radius of daily railway traffic.Northern Italy, for example, is an important export market for steel from SSAB Tunnplåt.

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High-tech production.Steelmaking is a high-tech business that is based on bothscience and experience. Certain data cannot be measured,because measuring devices cannot withstand the hightemperatures. To be able to understand what is happeningin the liquid iron or steel you have to combine a lot of inputand output data in complicated computer models that arebuilt up around calculations and practical knowledge. As one of the researchers at SSAB Tunnplåt in Luleå says,”It is easier to measure the composition of the surface ofthe moon than to measure the composition inside theblast furnace”.

Research and development (R&D) are conducted byresearchers and development engineers who work withvarious short-term and long-term projects within theproduction units. Sometimes it is a question of solvingeveryday problems, sometimes of coming up with entirelynew methods to make processes more efficient.

To solve a problem, development engineers can co-operate with works operators and the pellet supplier,LKAB, or with the customer who uses the steel. Often,we co-operate with researchers from universities inSweden and abroad, or with other steel producers via thebranch association Jernkontoret (the Swedish SteelProducers’ Association). Another partner in developmentis Mefos, a research institute with pilot scale facilities inLuleå.

R&D are carried out in the following areas:• Product development – to produce new steel grades

corresponding to market demands.• Operating stability – to avoid interruptions and quality

deviations.• Process development – to produce as much steel as

possible with the minimum consumption of energy, alloys, etc.

• Environmental development – to minimize environ-mental impact.

• Training/education of personnel – to improve com-petence throughout the organization.

Example:An example of an R&D project is the injection of slagformers directly into the blast furnace as a complement to adding slag formers from the top. If the composition of the slag needs to be adjusted and changes are onlymade from the top, it takes at least eight hours before thechange is noticeable in the hot metal tapped from theblast furnace. However, if slag formers could be injectedinto the blast furnace in the same way as coal powder,the change would be noticed much faster.

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Objectives and skills.To achieve continuous improvement SSAB Tunnplåt applies management by objectives. All employees areactively involved in discussing various targets and results are compared with objectives each month.

It is difficult to navigate the course ahead merely bylooking in the rear-view mirror. Having future targetsto aim at encourages employee commitment and parti-cipation. Targets are set for each unit, department, andcrew. One overall target is to improve production effici-ency. The success ratio can be measured, for example,by the amount of hot metal produced per man-hourand year. One man-hour is equal to one worked hourper employee, distributed equally over all occupationalgroups. As production efficiency increases, so does theamount of hot metal/man-hour. The target is to achie-ve uniform operation without disturbances. This can bemeasured in number of heats per twenty-four hours inthe steel plant. A heat is the quantity of hot metal/steelwhich a steel ladle can hold, i.e. 114 tonnes. The moreuniform the operation, the more heats per twenty-fourhours.

Skills developmentIt is important for each individual to learn new thingsand to develop. Not only do the people at SSABTunnplåt in Luleå set output targets, they also set targets for their own personal development. To somepeople the target can be an upper secondary schooleducation, to others a thesis for a doctorate. There are a lot of possibilities and opportunities for study in a number of basic subject areas, such as mathematics,English, physics and computer science. Some use dis-tance tuition, while others attend separate coursesduring their leisure hours. The form is adapted to suitthe work and family situation.

An important strategy for all development whichtakes place in the production units is that everyoneshould learn more about the company as a whole. Each person learns how his or her own tasks are relatedto preceding and subsequent production steps. Thisgives everyone a better understanding of how theirown work affects the work of others.

SSAB Tunnplåt AB, SE-971 88 Luleå, Telephone +46 (0)920 920 00, Telefax +46 (0)920 927 14, www.ssabtunnplat.com, www.ssab.se