Mold Powders for Bottom Pouring By Chris Camino and John Neal

1. Mold Powders for Bottom PouringBy Chris Camino and John Neal Ingot Metallurgy Forum October 25, 2016 Burnham PA

2. Overview • Introduction to Vesuvius and Metallurgica • Functions and Properties of Bottom Pour Fluxes • Types of Bottom Pour Powders • Raw Materials / Fly Ashes • Packaging and Application • Summary • References

3. Vesuvius • Global 11000 employees • 100 years • Publicly owned • Innovation in molten metal flow • Acquisitions in mold powder Foseco 2007 Metallurgica 2012

4. Metallurgica History • 1958 : Hans Eitel first fly ash / soda ash powder for ingots. • 1963 : Builds plant in Mulheim Germany • 1964 : Produces first continuous casting powder • 1965 : Metallurgica is founded • 1984 : Builds first spray dryer at Metallurgica • 1990 : H. Eitel awarded PhD for spray drying granules for mold flux industry. • 1996 : H. Eitel passes away, Metallurgica remains a family business. • 1999 : Fourth spray tower is commissioned in order to supply global demand. • 2012 : Vesuvius acquires Metallurgica.

5. The Mold Powder Plant in Mulheim Germany

6. Metallurgica • Mulheim plant produces mold fluxes for slab, CSP, billet, bloom, ingot. • Four separate spray towers • Supply ingot fluxes to over 100 customers on 5 continents • Produce over 50,000 tonnes of mold flux per year • Laboratory facility analyses over 6000 samples per year

7. Functions & Properties

8. Functions of Bottom Pour Mold Powder

9. Functions of Bottom Pour Mold Powder • Insulate liquid metal • Flux Carbon Content • Melt Rate • Flowability • Density

10. Functions of Bottom Pour Mold Powder • Insulates liquid metal • Protects from reoxidation • Melt Rate • Viscosity

11. Functions of Bottom Pour Mold Powder • Insulates liquid metal • Protects from reoxidation • Traps/absorbs non metallics • Slag chemistry • Melt Rate

12. Functions of Bottom Pour Mold Powder • Insulates liquid metal • Protects from reoxidation • Traps/absorbs non metallics • Helps with ingot stripping • Melt Rate • Viscosity • Flowability

13. Functions of Bottom Pour Mold Powder • Insulates liquid metal • Protects from reoxidation • Traps/absorbs non metallics • Helps with ingot stripping • Ingot quality • Viscosity • Slag Chemistry • Flowability

14. Properties : Melting Point • Melting to a controlled amount of liquid is important for reoxidation protection and insulation. Note : Melt point always lower than liquidus. Free carbon content and ingot teeming parameters are key, but melt point temperature allows versatility for achieving an optimum liquid pool depth.

15. Properties : Melting Rate, Free Carbon, & Carbonates • The rate at which a powder melts is critical and must be controlled • Free carbon controls rate of liquid formation during teeming. • Fly Ash Coke • Metallurgical Coke • Carbon Black • Graphites • Amount of carbon in mold powder can vary from 0 to 35%. • Carbonates are typically from soda ash which help with melting and the gas evolution helps with flowability for low density powders. • What happens on heating a powder?

16. What Happens on Heating by DSC 110oC 650oC 850oC

17. Melting Rate Test in Lab Furnace at 1400 oC • 30% carbon fly ash melt time was 22 minutes • 16% carbon synthetic melt time was 15.5 minutes 30% carbon FA 30% carbon FA 16% carbon Syn.

18. Properties : Flowability • Bottom pour powders must flow and cover all of the meniscus well throughout the teeming time • Fluxes are designed and controlled for flowabilty Apparatus for measuring flowability

19. Density • Comparison of density continuous cast and bottom pour mold powders Bottom pour powders are generally lower in density.

20. Chemistry, Basicity, & Glassiness • CaO / SiO2 Ratio • Carbon steel mold powders both fly ash and synthetic tend to be low basicity, high in viscosity, high in free carbon, and solidify glassy. • Stainless steel mold powders tend to be synthetic, higher in basicity, lower in viscosity, lower in free carbon, and solidify crystalline • Head end mold powder slag has been analyzed showing dilution by as much as 40% from trapped non metallics.

21. Low Basicity Mold Powder for Carbon Steels • CaO/SiO2 ratio is typically around 0.10 with SiO2 and Al2O3 as major constituents • Melting behavior is controlled by the Na2O content usually coming from soda ash up to 10% in the recipe • So a look at phase diagrams may be useful

22. Na2O Fluxes SiO2 Sodium oxide is a powerful flux to silica.

23. Na2O fluxes SiO2 and Al2O3 Fly ash powder for C steel is in the albite region. Synthetic powder is in the nepheline region

24. High Basicity Powders for Stainless and Alloys • CaO/SiO2 ratios are around 0.60 to 1.20 with SiO2 and CaO as major constituents. • Melting behavior may be controlled by flux additions of Na20 and/or F although some do not contain flux additions. Those are higher in melting point and lower in free carbon. • These powders are considered more effective for dissolving inclusions • The binary phase diagram for CaO and SiO2 follows:

25. CaO and SiO2 Powders for stainless, nickel, and monels usually have CaO and SiO2 contents in the low liquidus region above

26. Property : Viscosity • Viscosity is a measure of a fluid’s resistance to flow when subjected to an external force. Usually measured by a rotating viscometer at various temperatures. Typically reported at 1300oC. • IRSID calculation from chemistry. • Wide range of IRSID values in bottom pour. Viscosity is very critical for continuous casting but not so much for bottom pouring.

27. Types of Bottom Pour Powders

28. Types of Bottom Pour Powders • Fly Ash • Synthetic • Granulated

29. Types of Bottom Pour Powders • Fly Ash • Synthetic • Granulated • A mechanical blend of fine raw materials which includes fly ash • Pros • Versatile for most applications • Good source of carbon • Spreadabilty • Affordable • Cons • Perception of inconsistency • Perception of availability

30. Types of Bottom Pour Powders • Fly Ash • Synthetic • Granulated • A mechanical blend of fine raw materials which includes not containing fly ash • Pros • Tighter Chemistry Control • Potentially Lower Gas Off-take (lower flaming & gas combustion) Different sources of Na2O • Cons • Higher costs

31. Control of Fly Ash in Powders for Carbon Steel Fly Ash Synthetic Note the tight control of sodium and free carbon in the fly ash powder compared to the synthetic

32. Types of Bottom Pour Powders • Fly Ash • Synthetic • Granulated • A blend of fine raw materials converted into spherical granules by pulping into water and then spray drying. • Pros • Highly consistent • Premium flowability • Environmentally superior • Cons • Cost

33. Spray Dried Mold Powder

34. Magnified View of a Spray Dried Granule Individual raw materials can be seen. Spray dried mold powder is available for bottom pour but not widely used.

35. Raw Materials

36. Raw Materials in Mold Powders Raw material selection is fixed with the recipe

37. Wollastonite • Chemistry • CaO 42.1% • MgO 1.5% • Na2O 0.3% • Al2O3 1.8% • SiO2 51.9% • Where • New York • China • Comments • Crushed into fibrous, needle shaped particles • May inhibit flowability

38. Soda Ash

39. Expanded Perlite Top photo is crude perlite. Bottom photo is microspheres expanded from fine perlite

40. Fluorspar

41. Fly Ash • The major by product from the combustion of pulverized coal in power plants. Fly ash is the portion carried away by the flue gas stream and captured by precipitators • Chemistry represents clay minerals ,pyrite, and calcite with some residual carbon • Form is generally glassy, spherical, and less than 45 microns • Can be variable so selectivity and blending is important

42. Chemistry of Some Ruhr Fly Ashes

43. Cenospheres in German Fly Ashes Much of the carbon is in the form of cenospheres

44. Cenospheres and Carbon in German Fly Ashes Microscopic assessment of low carbon and high carbon fly ashes at Mulheim

45. Plant Features for Processing/Controlling Fly Ashes • Sourcing 4 Ruhr area fly ashes for many years • Silo trucks deliver 25 mt which are sampled/analyzed for chemistry and density prior to unloading • Processed through huge storage silos (235m3) through blending silos (125m3). Met coke added if needed • Powder mixer is pharmaceutical type- 4 mt per batch • First batch is sampled tested for carbon and flowability. Correction is made if needed while still in the mixer and to subsequent batches • Composite sample for the charge is analyzed for acceptance and certificate of analysis • Typical fly ash use is around 6500 tons/year. Some is used in powders for continuous casting The mold powder product is more consistent in quality than the individual fly ashes

46. Long Term Outlook Supply of German Fly Ashes • No issues are perceived for the long term • Synthetic powders are backup • Very few customers in Europe are interested in replacing German based fly ash powders with synthetic

47. Packaging & Application

48. Packaging Options • 1.5 kg plastic • 2.5 kg plastic • 5.0 kg paper/plastic • 5.0 kg paper/plastic with eyelets • 5.0 kg paper/plastic with handles • 10.0 kg paper/plastic with eyelets • Others

49. Bags for Hanging Bag with aluminum eyelet. Bag with built in handle

50. Techniques for Placement • Hang the bags • Open bags/pour powder to bottom • Place bags in bottom • Pour powder during teeming