1 Recent Developments in Refractories & Clean Steel Making Technology Andreas Buhr, Almatis, Frankfurt, Germany Ralf Bruckhaus, AG der Dillinger Hüttenwerke, Dillingen, Germany Reinhard Fandrich, Stahlinstitut VDEh, Düsseldorf, Germany International Conference on Advances in Refractories and Clean Steel Making, June 26 – 28, 2013, Isphat Bhawan, SAIL, Ranchi, India Page 2 Content Trends in steel making technology Requirements on high purity resp. high quality (HQ) steel grades Focus on secondary metallurgy Impact of refractories and trends Interaction between steel and refractories Refractories as tools for clean steel making Economics in refractory usage Conclusion & Literature
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Recent Developments in Refractories & Clean Steel Making Technology
Andreas Buhr, Almatis, Frankfurt, GermanyRalf Bruckhaus, AG der Dillinger Hüttenwerke, Dillingen, GermanyReinhard Fandrich, Stahlinstitut VDEh, Düsseldorf, Germany
International Conference on Advances in Refractories and Clean Steel Making, June 26 – 28, 2013, Isphat Bhawan, SAIL, Ranchi, India
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Content
�Trends in steel making technology�Requirements on high purity resp. high quality (HQ)
steel grades�Focus on secondary metallurgy
�Impact of refractories and trends� Interaction between steel and refractories�Refractories as tools for clean steel making�Economics in refractory usage
�Conclusion & Literature
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Page
� Ongoing development of new steel grades with tailore d properties for various very different applications
� High purity steel grades with tight specifications for undesired impurities and alloying elements
� Extended processing of liquid steel in secondary me tallurgy� Zero error strategies with max. productivity and fl exibility� Near net-shape casting technologies in order to red uce the energy
consumption (e.g. thin slab vs. conventional CC -50 %)� Share between oxygen and electrical steel making de pending on
maturity of steel market (availability of scrap) in a region:� Americas, Europe, Japan 40-50% EAF� China <10% EAF� India 60% EAF; limited scrap but HBI/DRI instead
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General trends in steel making technology
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Requirements on HQ steel grades: impurity content
Achievable contents after secondary metallurgical treat ment between 1960 and 2010
Elements:C, S, O, N, H
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Page
Red = Min.
Target
Blue = Max.
Target
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Requirements on HQ steel grades: alloying agents an d relevant aggregates for ladle treatment
Page 6Source: A. Viertauer, Siemens VAI Metals Technologie GmbH, VDEh refractory seminar April 2012
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PageSteel treatment in the ladle defines quality of the steel grades
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Secondary metallurgy for BOF and EAF process routes
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� Scheduling in a steel shop more and more important� Reliable availability of the equipment mandatory (incl. R efractories!)
power outages a challenge in India� Re-heating of steel required due to extended processing ti me 8
Secondary metallurgical process routes – flexibility and d iversity
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PageAbout 350 VD units and 200 RH units in operation ww 2010
� Special requirements on steel oxide cleanliness for thin slab casting to avoid clogging
� relatively high share of thin slab in Indian produc tion 10
Technological evaluation of continuous casting processe s
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The steel ladle as a metallurgical reactor
Source: H. Lachmund, AG der Dillinger Hüttenwerke, VDEh steel ladle lining seminar September 2012
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Purging plugs (or lances) as functional refractorie s essential for treatmentWear resistance of sliding gate plates for automate d flow control or Ca-treated steel(thin-slab casting)
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Refractories and clean steel making in secondary metallu rgy
Slag resistance against metallurgical reactive slag composition
Thermodynamic stability of refractory oxides to avoid re-oxidation of steel
Lower carbon content to avoid or limit C-pick up after vacuum treatment
Insulation layer in ladle lining to reduce heat losses during extended treatment times
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Slag resistance of ladle refractories
�Metallurgically reactive top slag, low melting & viscosity
�More aggressive forrefractory linings
�Use of higher qualityrefractories in ladles
Source: A. Viertauer, Siemens VAI Metals Technologie GmbH, VDEh refractory seminar April 2012
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Slag line:� MgO/C bricks based on fused magnesia and higher car bon
content (incl. graphite)� Often bottleneck for balanced lining life, no compr omise on
quality
�Side wall and bottom:� High alumina materials changed from andalusite or b auxite to
higher purity synthetic alumina based materials (ta bular alumina, spinel)
� Doloma replaced by MgO/C in order to achieve higher lining lifein some steel works, but still in use elsewhere
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Slag resistance of ladle refractories
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Slag resistance of high alumina ladle refractories
�Dortmund steelworks (1995):CaO ≈ 30%, C/A = 0.6 OK for andalusiteC/A ≈ 1 andalusite 50 heats (SiO 2!) vs. bauxite 130 heats
� IJmuiden steelworks (2001):direct strip plant (DSP = near net-shape casting)Ca treatment & C/A ratio of slagandalusite bricks -70% lifetime at 20% DSP heats
-90-95% at 100% DSPreplaced by high purity fired spinel bricks
�Today, andalusite and bauxite in back lining but not wear lining
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Decreasing stability with:- increasing temperature- decreasing P O2
- decreasing CO 2/CO- decreasing H 2O/H2
4/3 Al + O4/3 Al + O4/3 Al + O4/3 Al + O2222 = 2/3 Al= 2/3 Al= 2/3 Al= 2/3 Al2222OOOO3333
Si + OSi + OSi + OSi + O2222 = SiO= SiO= SiO= SiO2222
Economic aspects� Refractory related operational costs beyond purchas e price &
installation:���� Production losses due to unavailability of vessels (relining, lack of
reliability, unexpected failure – or even worse, inc idents)���� Effect on steel quality���� Energy losses���� Yield���� Environmental, Health & Safety���� etc
� Refractory related operational cost ≈≈≈≈ directly spend refractory cost
� Flexibility in secondary metallurgy process routes requires performance reserves of refractories
� “Refractory is a tool to produce steel” (Rinus Siebring, TATA, VDEh Refractory Seminar part 2)
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�Secondary metallurgy is the key area in clean steel making technology
�Production routes are becoming increasingly complex in order to achieve the metallurgical targets
�Flexibility of the metallurgical equipment is neede d to achieve the desired quality of steel and the performance of refractories is a contributing factor here
�Re-heating of the steel is often required due to lo ng process times
�Higher purity refractories are used for clean steel making and synthetic materials replace natural ones for high a lumina refractories
�Energy and resource efficiency is becoming even mor e important and thermal insulation contributes here 28
Conclusion
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� R. Fandrich, B. Kleimt, H. Liebig, T. Pieper, F. Tr eppschuh und W. Urban: Stand der Pfannenmetallurgie und aktuelle Trends (Status of secondary metallurgy and present trends), stahl und eisen 131 (2011) Nr. 6/7, 75-89
� R. Bruckhaus, R. Fandrich: Trends in Metallurgy 201 2, 55th International Colloquium on Refractories, Aachen, Germany, 19-20 September 2012
� R. Bruckhaus, R. Fandrich: Ist Indiens Stahlindustrie auf dem Sprung? (Indian steel industry leaping forward?), stahl und eisen 133 (2013), Nr. 1, 33-38
� A. Buhr, M. Spreij, J. Dutton: Technical and Econom ic Review of High Alumina Raw Materials for Steel Refractories, IREFCON 2010, Kolkata
� H. Lachmund: Demands on refractory material for sec ondary metallurgy, 7 th
international symposium steel ladle lining, Steel A cademy VDEh, Hannover, Germany, September 2012
� A. Viertauer: Ladle Metallurgical Treatments & Refr actory Stress for a Steel Teeming Ladle, Refractory seminar Steel Academy VDE h, Cologne, Germany, April 2012