TRANSACTION PAPER

 

The effects of hot rolling process and the nitrogen and sulphur content on the microstructural development of aluminium killed hot rolled low carbon strip steel

 

 

C.W. Siyasiya; W.E. Stumpf

Department of Materials Science and Metallurgical Engineering of the University of Pretoria, South Africa

 

 

---

SYNOPSIS

Process and steel chemistry differences in hot rolled Al-killed low carbon strip steel between the hot charge route (HCR) as practiced in a compact strip production (CSP) plant and the conventional cold charge route (CCR) have been studied. This was done with reference to differences in reheating practice, hot rolling practice and steel chemistry through emphasis on the effects of solubility and reprecipitation of AlN in the two process/product combinations and its effect on ferrite grain size development. An earlier modeling study on the evolution of the austenite grain size in both of the above hot rolling processes has also now been extended to include an estimate of the possible effects of retained strain after the last finishing pass on the ferrite grain size. As part of this study the equilibrium solubility trends of AlN in a number of boron-free low carbon Al-killed strip steels with low and high sulphur content from the two respective processes was investigated by the thermoelectric power (TEP) technique and differences in the effects through the derived solubility equation of Log[Al][N]=2.6-9710/T at typical slab reheating temperatures was demonstrated. Ferrite grain size modelling using the significantly lower Ar3 transformation temperatures generally found in hot rolled low carbon strip steel produced in the CSP plant using the HCR compared well to the larger grain size produced in the conventional CCR strip rolling plant.

Keywords: austenite grain size modelling; thermoelectric power (TEP); compact strip production (CSP); cold charge route (CCR); ferrite grain size

---

 

 

“Full text available only in PDF format”

 

 

References

1. STUMPF, W.E. Journ SA Inst Min and Met., vol. 103, no. 10, 2003. pp. 617-631.         [ Links ]

2. STUMPF, W.E. Journ. SA Inst. Min. and Met., vol. 104, no. 11, 2004. pp. 643-652.         [ Links ]

3. SIYASIYA C.W. and STUMPF, W.E. The effect of sulphur content on the recrystallisation behaviour of cold worked low carbon aluminium-killed strip steels (in the press with Materials Science and Engineering A).         [ Links ]

4. SIYASIYA, C.W. PhD Thesis, University of Pretoria, March 2007.         [ Links ]

5. VERDOORN, F.A. and STUMPF, W.E. Witwatersrand Metallurgy Conf. 11 and 12 October 2004        [ Links ]

6. PERDIX, C.H. Characteristics of Plastic Deformation of Metals during Hot Working, Report CECA No. 7210 EA/311, 1987, Saint Germain-en-Laye (France), Inst. de Recherches de la Siderurgie Francaise (IRSID).         [ Links ]

7. HODGSON, R.D. and GIBBS, R.K. ISIJ, vol. 32, no. 12, 1992, pp. 1329-1338.         [ Links ]

8. WILSON, F.G. and GLADMAN, T. International Materials Review, vol. 33, 1988. pp. 221.         [ Links ]

9. BEEGHLY, H.F. Anal. Chem., vol. 21, no. 12, 1949. pp. 1513-1519.         [ Links ]

10. YU, H., KANG, Y.L., DONG, H.B., LIU, D.L. and FU, J. Acta Metallurgica Sinica vol. 15, 2002. pp. 375.         [ Links ]

11. BLATT, F.J., SHROEDER, P A., FOILES, C.L. and GREIG, D. Thermoelectric Power of Metals, Publ. Plenum Press, New York and London.         [ Links ]

12. NORDHEIM, L. and GORTER, C.J. Physica 2, 1935. 383.         [ Links ]

13. BORRELLY, R. and BENKIRAT, D. Acta Metall. vol. 33, 1985, pp. 855-866.         [ Links ]

14. BIRON, I., BORRELLY, R., DELANUAE, P. and THOMAS, P.J. Mém. Sci. Rev. Mét., vol. 11, 1991, pp. 725-733.         [ Links ]

15. BRAHMI, A. and BORRELLY, R. Acta Mater. vol. 45, no. 5, 1997, pp. 1889-1897.         [ Links ]

16. LESLEI, W.C., RICKETT, R.L., DOTSON, C.L. and WATSON C.S. Trans. ASM, vol. 46, 1954. pp. 1470-1497.         [ Links ]

17. BLATT, F.J. Proc. Phys. Soc. vol. 83, 1964, pp. 1065.         [ Links ]

18. RAYNE, J.A. and CHANDRASEKHAR, B.S., Physical Rev. vol. 122, no. 6, 1961.         [ Links ]

19. DARKEN, L.S., SMITH, R.P. and FILER, E.W. Trans. AIME, vol. 191, 1951. pp. 1174.         [ Links ]

20. PICKERING, F.B. in Proc. Conf. Philadelphia, PA. Oct. 1983, ASM.         [ Links ]

21. ANDREWS, K.W. JISI, vol. 184, 1956, pp. 414        [ Links ]

22. USHIODA, H., SUZUKI, H.G., KOMATSU, H. and ESAKA K. Nihon Kinzoku Gakkai shi, J. Japan Inst. Metals, vol. 59, no. 4, 1995, pp. 373-380.         [ Links ]

23. ENGEL, B. and DREWES, E.J. Technology of Continuously Annealed Cold Rolled Sheet Steel, R. Pradhan, (ed). Proc. Symp. The Metallurgy Society of AIME, Michigan, 1984, pp. 123-138.         [ Links ]

24. UMEMOTO, M., OHTSUKA, H. and TAMURA, I. Structure and properties of HSLA steels, 1984, pp. 96.         [ Links ]

25. LANGE, W.F. III, ENOMOTO, M. and AARONSON, H. I., Met. Trans. A, vol. 19A, 1988, pp. 427-440.         [ Links ]

26. KAUFMAN, L., RADCLIFFE, S.V. and COHEN, M. Decomposition of austenite by diffusional process, V. H. Zackay and H. I. Aaronson (eds.), 1962, pp. 313-352.         [ Links ]

27. Yokota, T., GARCIA MATEO, C. and BHADESHIA, H.K.D.H. Scripta Materialia, vol. 51, 2004, pp. 767-770.         [ Links ]

28. TAMURA, I., OUCHI, C., TANAKA, T. and SEKINE, H., Thermomechanical Processing of High Strength Low Alloy Steels, Butterworths. 1988, p. 29.         [ Links ]