EFFECT OF BOTTOM STIRRING ON BASIC OXYGEN STEELMAKING A THESIS SUBMITTED TO THE GRADUATE SCHOOL OF NATURAL AND APPLIED SCIENCES OF MIDDLE EAST TECHNICAL UNIVERSITY BY ÇAĞRI DOĞAN BİLGİÇ IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE IN METALLURGICAL AND MATERIALS ENGINEERING MAY 2016 Approval of the thesis: EFFECT OF BOTTOM STIRRING ON BASIC OXYGEN STEELMAKING submitted by ÇAĞRI DOĞAN BİLGİÇ in partial fulfillment of the requirements for the degree of Master of Science in Metallurgical and Materials Engineering Department, Middle East Technical University by, Prof. Dr. Gülbin Dural Ünver ________________ Dean, Graduate School of Natural and Applied Sciences Prof. Dr. C. Hakan Gür _________________ Head of Department, Metallurgical and Materials Eng. Prof. Dr. Naci Sevinç _________________ Supervisor, Metallurgical and Materials Eng. Dept., METU Examining Committee Members: Prof. Dr. İshak Karakaya _________________ Metallurgical and Materials Engineering Dept., METU Prof. Dr. Naci Sevinç _________________ Metallurgical and Materials Engineering Dept., METU Prof. Dr. C. Hakan Gür _________________ Metallurgical and Materials Engineering Dept., METU Prof. Dr. Abdullah Öztürk _________________ Metallurgical and Materials Engineering Dept., METU Ass. Professor. Kazım Tur _________________ Metallurgical and Materials Engineering Dept., Atılım University Date: 04.05.2016 I hereby declare that all information in this document has been obtained and presented in accordance with academic rules and ethical conduct. I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work. Name, Last name : ÇAĞRI DOĞAN BİLGİÇ Signature iv ABSTRACT EFFECT OF BOTTOM STIRRING ON BASIC OXYGEN STEELMAKING Bilgiç, Çağrı Doğan M.S., Department of Metallurgical and Materials Engineering Supervisor: Prof. Dr. Naci Sevinç May 2016, 64 pages ERDEMİR Steel Plant produces wide range of alloy steel for various industries. Main demand of industries for steel is high quality end product with lower prices. One of the criterion affecting not only the steel cleanliness and also price of the product is bottom stirring in basic oxygen steelmaking. The objective of this study is to investigate effects of bottom stirring on basic oxygen steelmaking. With this objective, process parameters, analysis of produced heats were investigated to determine effects of stirring and optimum stirring program. For the current study, overall and individual analyses carried out using the turndown slag, the metal composition and the input materials data for many heats in terms of the amounts of oxygen, carbon, manganese, nitrogen, sulphur, and phosphorus at the end of blow. v The results indicated the advantages of bottom stirring since it enables the steel production with lower amounts of oxygen, carbon, sulphur and phosphorus while it makes high manganese containing steel production possible. Additionally, by the help of bottom stirring higher iron yield is possible. The efficient removal of impurities comes along with a cleaner and high quality end product. Moreover, it is possible to have economic savings due to low requirements of deoxidizer and ferromanganese during the production. Keywords: Steel, basic oxygen steelmaking, bottom stirring vi ÖZ ALTTAN KARIŞTIRMANIN BAZİK OKSİJEN ÇELİK ÜRETİMİNDEKİ ETKİSİ Bilgiç, Çağrı Doğan Yüksek Lisans, Metalurji ve Malzeme Mühendisliği Bölümü Tez Yöneticisi: Prof. Dr. Naci Sevinç Mayıs 2016, 64 sayfa ERDEMİR Çelik Fabrikaları çeşitli sanayiiler için geniş türde çelikler üretir. Yüksek kaliteli düşük fiyatlı çelikler müşterilerin ana talebidir. Bazik oksijen çelik üretiminde alttan karıştırma hem çelik temizliğini hem de ürün fiyatı etkileyen önemli kriterlerden biridir. Bu çalışmanın amacı bazik oksijen çelik üretiminde alttan karıştırmanın etkisini araştırmaktır. Bu amaçla, proses parametreleri ve döküm analizleri alttan karıştırmanın etkilerini ve optimum karıştırma programını bulmak amacıyla gözden geçirilmiştir. Bu çalışmada, birçok döküm için cüruf, metal kompozisyonu ve giriş malzemeleri verisi kullanılarak üfleme sonundaki oksijen, karbon, manganez, azot, kükürt ve fosfor genel ve ayrı analizleri gerçekleştirildi. Sonuçlar alttan karıştırmanın avantajları olarak düşük oksijen, karbon, sülfür ve fosforlu çelik üretimine olanak sağladığını, yüksek manganlı çelik üretimini mümkün kıldığını göstermiştir. İlaveten, yüksek demir verimi alttan karıştırma yardımıyla mümkün olmaktadır. Empüritelerin daha etkili giderilmesi daha temiz ve yüksek kaliteli ürün ortaya çıkarmaktadır. Bununla beraber, üretim esnasındaki vii düşük oksijen giderici ve ferro manganez ihtiyacı sebebiyle ekonomik kazanç mümkün olmaktadır. Anahtar kelimeler: Çelik, bazik oksijen çelik üretimi, alttan karıştırma viii ACKNOWLEDGEMENTS I would like to express my deep gratitude first and foremost to my supervisor, Prof. Dr. Naci Sevinç for his irreplaceable support, guidance and patience throughout this research. I would like to thank to managers, chiefs and colleagues from Steelmaking Department of Erdemir and especially Ural Durusu, Davut Çelik, Taner Tüylüoğlu, Yılmaz Tetik and İsa Keskin for their contributions to this study. I am and I will be thankful eternally to my family for their support on me and my decisions all the time. Lastly, I owe a lot to my friends Berkay Gümüş, Onur Dinçer, Mustafa Burak Coşar, Hazar Çakmakçı, Uğur Can, Yunus Emre Sözer, Savaş Şenkal, Tolga Balcı, Okan Aykan, Cüneyt Onat, Serdat Söğüt, Serhat Bozkurt, Özgür Tanıdır and Said Alşan and Ömer Bozoğlu for being with and helping me during hard times. ix To Bergay Gümüş x TABLE OF CONTENTS ABSTRACT .......................................................................................................... v ÖZ ........................................................................................................................ vii ACKNOWLEDGEMENTS ................................................................................ ix TABLE OF CONTENTS .................................................................................... xi LIST OF FIGURES ........................................................................................... xiii LIST OF TABLES .............................................................................................. xv CHAPTERS .......................................................................................................... 1 1. INTRODUCTION .......................................................................................... 1 2. LITERATURE REVIEW .............................................................................. 3 2.1 Process Description ...................................................................................... 3 2.2. Mass and Energy Balances .......................................................................... 5 2.3 Process Reactions ......................................................................................... 7 2.3.1 Refining Reactions in BOF Steelmaking ................................................... 7 2.3.1.1 Carbon Oxidation .............................................................................. 10 2.3.1.2 Silicon Oxidation .............................................................................. 12 2.3.1.3 Manganese Oxidation ....................................................................... 13 2.3.1.4 Phosphorus Oxidation ....................................................................... 13 2.3.1.5 Sulphur Reaction ............................................................................... 14 2.3.2 Slag Formation in BOF Steelmaking ....................................................... 15 2.4 Bottom Stirring ........................................................................................... 16 2.4.1 Selection of Stirring Gases ...................................................................... 17 xi 2.4.2 Nitrogen and Hydrogen Control .............................................................. 18 3. EXPERIMENTAL WORKS ....................................................................... 21 3.1 Steel Production at ERDEMİR Steel Plant ................................................. 21 3.2 Steel Production Process with BOF ............................................................ 22 3.2.1 BOF General Information ........................................................................ 22 3.2.2 BOF Process ............................................................................................ 24 3.2.3 BOF Blowing Process and Regimes ........................................................ 28 3.2.4 BOF Stirring Process and Regimes ......................................................... 30 3.3 Experimental Procedure .............................................................................. 34 4. RESULTS AND DISCUSSION ................................................................... 36 4.1 Introduction ................................................................................................. 36 4.2 The Analyses of Overall Production History of BOF ................................ 37 4.3 The Comparison of Specific Cases ............................................................. 40 4.3.1 Carbon and Oxygen Comparison ............................................................. 40 4.3.2. Manganese Comparison .......................................................................... 42 4.3.3 Phosphorus Comparison