Refractory in steel ladle application

Refractory in steel ladle application

1. Refractory in steel ladle application Department of Ceramic Engineering NATIONAL INSTITUTE OF TECHNOLOGY ROURKELA Seminar and Technical Writing (Autumn 2021) Course Instructor: Prof. Debasish Sarkar Presented by Satyam kumar Roll no. 519CR1004

2. Content Introduction Function of Steel ladle Classification of steel ladle Important ladle Refractories Requirement of refractory in steel ladle lining summary

3. Introduction Ladles in steel plant are generally used to transfer molten steel from the melting unit to the casting unit . It is a basic tool extensively used in the continuous casting operation and it has capability to resist heat. Structure of ladle is made multi-layered strong and heat insulated. Inner face of ladle is made up of special kinds of refractory bricks. These brick can withstand with high temperature and also heat resistant allowing them to hold molten metal . Figure 1.Image source: http ://www.wonlf.com/Products1?product_id=5

4. Function of ladle Transportation of molten steel tapped from basic oxygen furnace or an electric arc furnace between 1500-1700 ℃ to the continuous casting or ingot casting process. To improve the quality of molten steel acts as a secondary refining reactor. Supply of molten steel to a tundish or an ingot mould, with the flow rate controlled in a variable manner.

5. Classification of steel ladle 1.Casting ladle : It is used to pour hot molten metal for casting . Figure 2. Casting ladle [1] 2 Transfer Ladle: This type of ladle is used typically to transfer hot liquid molten metal from melting unit to casting unit or an auto pouring unit like in steel mills, the ladle can be transported on wheels, in a specially designed ladle transfer car, or hung from an overhead crane and tilted using another overhead lifting mechanism. Figure 3. Transfer ladle [1]

6. Treatment Ladle A ladle that is used to change some aspect of the molten metal by a process that takes place within the ladle. Continue .. Figure 4. Treatment ladle [1]

7. Important ladle refractories Magnesia refractories : M ajor source ; brine and sea water magnesia Advantages : Chemical stability very high High strength Good corrosion resistance In steel ladle lining less pure magnesia with 87% MgO ,2 wt.% CaO and 6 wt.% SiO 2 is used.

8. Continue.. Dolomite refractories : High temperature firing can transform natural double carbonate dolomite (CaCO 3 MgCO 3 ) into refractory dolomite ( CaO+MgO ). Dolomite with a high purity content of more than 97 percent CaO + MgO and 0.5 – 3 % impurities is known as high purity dolomite. Interaction with steel or steelmaking slags, dolomite exhibits exceptional refractoriness and is very thermodynamically stable It is used in steel ladle application with pitch bonded doloma with 60% CaO and 40 % MgO content. These kind of refractories with graphite composition and resin bonding is also used in wear areas in steel ladle application such as impact pad, slag lines etc

9. Zircon/Zirconia –Excellent refractory material with very high specific gravity (4.5 - 4.6 gm/cm 3 ) Advantages: Continue .. High melting point chemical inertness E xcellent mechanical strength and H igh thermal stability Excellent thermal spalling resistance Application:- steel ladle as a nozzle for pouring molten steel Zirconia Refractory: Natural source- Badeleyite Application: Slide gate plates in steel ladle Application

10. Carbon Group : Carbon is a conductive in nature that makes it different from any other group of refractories Bulk density 1.5-1.8 g/cm 3 , Apparent porosity = 12-25% A dvantages : High thermal stability Poor wettability High thermal conductivity Low thermal expansion coefficients Excellent thermal spalling resistance It is applicable where the presence of oxygen is minimum otherwise oxidation will take place and it will support the burning of carbon Continue ..

11. Spinel Refractories : Magnesium aluminate spinel exhibits unique combination of properties such as high melting point, excellent resistance to chemical attack, High strength at elevated temperature, excellent thermal shock resistance etc. makes a special class of refractory material General formula of this group is AB 2 O 4 Stoichiometric spinel contains 71.67 wt.% Al 2 O 3 and 28.33 wt.% MgO and has a molar ratio of 1 MgO to 1 Al 2 O 3 Continue ..

12. Crystal structure of spinel : Figure 5 cubic crystal structure of spinel [9]

13. Thermophysical properties of Spinel, Alumina and Magnesium oxide Properties Spinel Magnesium oxide Alumina Melting point (℃) 2135 2852 2054 Thermal expansion (10 -6 /℃)       100 ℃ 5.6 10-12 5.6 500 ℃ 7.6 11-13 7.3-8.0 1000 ℃ 8.4 13-15 8.7-9.3 1500 ℃ 10.2 15-19 9.3-9.9 Thermal conductivity (W/mK)       25 15 40 38 100 13 38 36 500 8 16 11 1000 5 7 7 Density ( gm/cm 3 ) 3.58 3.65 3.99 Table 1 [9-11]:

14. Spinel formation mechanism: Solid state reaction route Al 2 O 3 4MgO -3Mg 2+ +2Al +3 MgAl 2 O 4 MgAl 2 O 4 MgO 4Al 2 O 3 - 2Al +3 +3Mg 2 + 3MgAl 2 O 4 3Mg 2+ 2Al +3 Figure 6. Spinel formation through counter diffusion mechanism [12] Al 2 O 3

15. Requirements of refractory in steel ladle lining : Very high thermal stability High corrosion and slag penetration resistance High erosion resistance Very high thermal shock resistance

16. S teel ladle lining Zone Steel ladle is basically divided into various zone like slag line, sidewall, tuyere and impact pad Slag zone : In slag zone Magnesia carbon brick is employed . Advantages of Magnesia carbon Brick in slag region: Very high refractoriness so that no low melting eutectic temperature occurs between magnesium oxide and carbon. Graphite is the source of carbon which has very low thermal expansion coefficient value. Thermal spalling resistance of magnesia carbon refractories is very high. H igh thermal conductivity. Very high corrosion resistance.

17. Flow diagram of magnesia carbon refractory is shown in Figure below Continue.. Figure 7. Flow Diagram of magnesia carbon Refractory [4]

18. Continue.. Side wall In side wall portion of the ladle refractory based castables are used after 1990’s [13] for production of high purity steel and ultralow carbon steel. The benefit of this type of system it increases the durability of the product . The densification effect of magnesia based castable is very good and it also helps in expansion . Bottom portion Monolithic based refractory castable alumina spinel is used in the bottom portion of the ladle lining . . Lining life is increased considerably with superior corrosion resistant and thermal shock resistance compared to conventional brick used in ladle lining.

19. Advantages of refractory base castable bottom portion of ladle : High mechanical strength High thermal spalling resistance High corrosion resistance High erosion resistance High volumetric stability Continue..

20. Summary : Steel ladle plays an important role in steel making process. Production of steel is directly dependent on the performance of the ladle. Understanding the concept of ladle lining is very much important because it is made up with different kinds of refractory material and their requirement is different in different zone, no single material can full fill all these requirements .Thus a comprehensive study has been done with different kind of refractory material applied in steel ladle lining starting from the slag line to bottom portion of the ladle

21. Refrences : [1] Mahamure , N. (2013). Review of ladle furnace. Proceedings of the 7th ICECSME-2013, Pune, India, 65-70. [2] Nandi, D. N. (1987). Handbook on refractories. Tata McGraw-Hill Publishing Company Limited. [3] Matsui, T., & Taki , N. (2020). Refractory technology of ladle. Nippon Steel Technical Report, (415), 52-55. [4] Sarkar, R. (2016). Refractory technology: Fundamentals and applications. CRC Press. [5] Kathait , D. S. (2016). Ladle furnace refractory lining: A review. Department of Mechanical Engineering, SOET, HNB Garhwal University, Srinagar ( Garhwal ), Uttarakhand (India). [6] Sarkar, R. (2010). Refractory applications of magnesium aluminate spinel.  Interceram : Refractories Manual, 1, 11-14. [7] Braulio, M. A. L., Rigaud , M., Buhr , A., Parr, C., & Pandolfelli , V. C. (2011). Spinel-containing alumina-based refractory castables .  Ceramics International ,  37 (6), 1705-1724. [8] Bradt , R. C. (2004). Mg-Al SPINEL: IS IT THE MULLITE OF THE 21 ST CENTURY?. Refractories Applications & News, 9(4), 8-10. [9] Kingery , W. D., Bowen, H. K., & Uhlmann , D. R. (1976). Introduction to ceramics (Vol. 17). John wiley & sons. [10] Rethwisch , W. D. (2010). Callister , Materials Science and Engineering. [11] Rigaud , M. A., & Landy , R. A. (1996). Pneumatic Steelmaking.: Refractories. Iron and Steel Society. [12] Nakagawa, Z., Enomoto , N., I-S, Y., & Asano, K. (1995, November). Effect of corundum/ periclase sizes on expansion behaviour during synthesis of spinel. In UNITECR'95 Congress. Proc. Unified Int. Tech. Conf. on Refractories (Vol. 4). [13] Schnabel, M., Buhr , A., Exenberger , R., & Rampitsch , C. (2010). SPINEL: IN-SITU VERSUS PREFORMED- CLEARING THE MYTH. Refractory World forum, 2(2), 87-93.

22. Thankyou