Production of Grey Cast iron from Red Mud and Laterite Nickel ore

1. Production of Grey Cast iron from Red Mud and Laterite Nickel ore J.M Zeng, Z.M Tan, J.C Wang, A.P He Guangxi University May 7-10 2018. Athens

2. CONTENTS • Introduction • Experimental • Application • Summary

3. INTRODUCTION More than 10，000，000 Tons of Bayer red mud is generated every year in Baise district, Guangxi . China Red mud in Gaungxi

4. Red mud disposal site occupies a lot of farmland Red mud pool enclosed by hills Red mud dam River pollution caused by leaking in 2010 Red mud flow in 2016 (dam break)

5. Metal elements in the red mud can be recoveredby following carbothermic reactions in Electric Arc Furnace (EAF), by melting reduction. Where, Me: metal element M: reductant The final product is called “pig iron”

6. The Pig iron recovered will probably contains Si, Mn, Ti, Cr, V, ….... Fe Cr Ti Mn V Si However, such elements as Ti, Cr, V are Whitening elements. The recovered pig iron is white cast iron, which is a super hard and brittle materials and can’t be used for metal castings except for wear-resistant material.

7. White cast iron is like this in the microstructure Grey cast iron is like this in the microstructure Nickel In this case, We introduce Nickel to promote graphitizing, changing the alloy from white cast iron to grey cast iron. Nickel can also refines the pearlite and graphite structure, improves toughness.

8. EXPERIMENTS Chemical composition of raw materials (wt. %)

9. Process flow chart Coke powder Laterite nickel Bayer red mud pelletizing Production of cast Cast iron Melting Reduction in EAF for construction materials Slag

10. Electric Arc Furnace 1-Top graphite electrode; 2- Feeder port; 3- Iron and slag outlet; 4- Graphite crucible cum electrode 5- Bubble alumina; 6- Steel shell; 7- Water quenching tank; 8- Water cooling facility; 9-Viewing port 10-Supporting structure; 11- Main control cabinet; 12- Transformer; 13-Top electrode elevator system 1 is the high voltage bus 2 is the oil breaker, 3 is the trans- former 4 and 5 are high and low voltage coils respectively 6 is the iron core, 7 is the copper bar, 8 is the soft cables, 9 is the copper conducting tube 10 is the copper tile, 11 is the electrode, which was arranged in a vertical configuration, 12 and 13 are furnace liner and metal pool, respectively Melting reduction in electric arc furnace (EAF)

11. We control melting temperature under 1600C (measured by thermal imager)

12. a. white iron (Cementite） b. Cementite + ledeburite c. Graphite + ledeburite d. Grey iron (graphite +pearlite) Microstructure of cast iron in different Ni contents (a): 0.3%, (b):0.6%, (c):0.9% and (d):1.2%

13. The microstructure of the grey cast iron consists of graphite + pearlite (ferrite +cementite), which can greatly improve mechanical properties of the cast iron. Graphite pearlite

14. Typical chemical Composition of cast iron recovered from the Bayer red mud * the chemical compositions could be varied for each melt in our experiments, because of inaccurate temperature control.

15. Impact work (J) Total work Crack forming Crack propagation Specimen of the impact test Impact tester Ni addition (%) :Ni content and impact work Curves of oscillography impact

16. Nickel addition (%) :Nickel addition and hardness

17. UTS (MPa) :Nickel addition and UTS

18. APPLICATION Usually the cast iron reduced by carbothermic melting reduction can not be directly used for castings, it should be re-treated (including: adjusting composition, inoculation, Vermicular and spheroidizing treatments, etc.) as requested by customers. The following is an example

19. Application It was used for grey iron castings with higher mechanical properties, such as cylinder blocks in automobiles, components in diesel engines.

20. we wish to increase Ni, Si contents and decrease Cr and Ti contents as far as possible.

21. left: HT250 grey cast iron; right: RM250 produced from red mud + laterite nickel Comparison in microstructure between HT250 and RM250

22. left: RT380 grey cast iron; right: RM380 produced from red mud + laterite nickel Comparison in microstructure between RT380 and RM380

23. left: QT450 cast iron; right: RM450 produced from red mud + laterite nickel Comparison in microstructure between QT450 and RM450

24. RM450 UTS 650.29MPa EL 21.13% RM450 UTS 650MPa EL 21.13% Increased by 44% in UTS Load KN RM380 UTS 498MPa, EL 4.79% Increased by 31% in UTS RM250 UTS 286MPa, EL 2.9% Increased by 14% in UTS elongation (mm)

25. SUMMARY 1. By carbothermic reduction in EAF, Grey cast iron can be produced from Bayer red mud and laterite nickel through Electric arc furnace The test castings have been successfully manufactured, showing that it may be of significant in industry and worth of further investigation. 2. Niis the key element which make the cast iron to transfer from “white” to “grey”. The Ni content should be higher than 0.9%. 3. Compared with traditional grey cast iron, the RM grey cast iron provides better mechanical properties (due to small quantity of Ni, Ti, Cr, V).

26. Thanyoufor listening