Temperature changes in hot flat rolling of steels at low strain rates and low reduction

Abstract

A finite difference (two-dimensional) model developed to describe the heat flow at low strain rates (0.08–1.5 s⁻¹) and low reduction (∼10 per cent) for a hot flat rolled slab both during air cooling and during roll contact has been used in conjunction with experimentally measured temperatures through specimen thickness during roll contact after reheating to temperatures in the range 1000–1200°C for mild steel, low carbon SS316 and high carbon SS316 (with Nb, V and Ti).

At high strain rates (∼1.5 s⁻¹) a steep temperature gradient was produced in the specimen near the surface whereas for low strain rates (∼0.08 s⁻¹) this temperature gradient penetrated deep into the thickness, leading to a large drop in the mean rolling temperature.

Roll chilling, leading to higher values of the Zener-Holloman parameter, Z, resulted from a decrease in the mean rolling temperature and the large temperature gradient during roll contact. Temperature changes due to material composition, reheating temperature, contact time and rolling conditions led to precipitation strengthening and roll chilling effects which have accounted for the excess load and torque observed experimentally and industrially.

Keywords

transverse temperature mean rolling temperature total rolling load and torque temperature gradient roll chilling Zener-Holloman parameter precipitation strengthening

References

Barbosa

R. A. N. M.

PhD thesis, Sheffield University, 1983.

Sellars

C. M.

Computer modelling of hot working processes. In Perspectives in Metallurgical Developments, Centenary Conference Proceedings, Department of Metallurgy, University of Sheffield, 1984, pp. 209–217.

Harding

R. A.

PhD thesis, Sheffield University, 1976.

Leduc

L. A.

PhD thesis, Sheffield University, 1980.

Aiyedun

P. O.

PhD thesis, Sheffield University, 1984.

Sellars

C. M.

Sah

J. P.

Beynon

J. H.

Foster

S. R.

Plane strain compression testing at elevated temperatures. Report on research work supported by SRC Grant B/R6/ 1481, 1976.

Foster

S. R.

PhD thesis, University of Sheffield, 1981.

Colas

R. O.

PhD thesis, University of Sheffield, 1983.

Al-Jouni

F. E.

PhD thesis, University of Sheffield, 1983.

10.

Diniz

N. R.

PhD thesis, University of Sheffield, 1984.

11.

Aiyedun

P. O.

Hot flat rolling simulation by use of the Bland and Ford's cold rolling theory for HC SS316 at low reduction and low strain rates. In Proceedings of International ASME Conference on Modelling and Simulation, Williamsburg, Vol. 3, 1986, pp. 14–36.

12.

Beynon

J. H.

PhD thesis, University of Sheffield, 1979.

13.

Jonas

J. J.

McQueen

H. J.

Treatise on Materials Science and Technology, Vol. 6, Plastic Deformation of Materials(Ed. Arsenault ), 1975, p. 395 (Academic Press, New York).

14.

Jonas

J. J.

Luton

M. J.

Advances in Deforming Processes (Eds Burke Weiss ), 1978, p. 215 (Plenum, New York).

15.

Yanagi

Trans. ISIJ, 1976, 16, 11.

16.

Afonja

A. A.

Sansome

D. H.

Int. J. Mech.Sci., 1973, 15, 1.

17.

Arnold

R. R.

Whitton

P. W.

Proc. Instn Mech. Engrs, 1959, 173, 241.

18.

Atkins

A. G.

Weinstein

A. S.

Int. J. Mech. Sci., 1970, 12, 641.

19.

Sparling

L. G. M.

Proc. Instn Mech. Engrs, 1983, 197A, 277.

20.

Arkulis

G. E.

Compound Plastic Deformation of Layers of Different Metals (Translated from Russian by Z. Lerman), 1965 (Israel Progress Science Transactions, Jerusalem).

21.

Zener

Holloman

J. H.

J. Appl. Physics, 1944, 15, 22.

22.

Sellars

C. M.

Laboratory methods of assessment of hot working characteristics. Paper presented at the Twenty-fourth Collogue de Metallurgie, Institut National des Sciences et Nucleaires, Sanclay, 1981, III.

23.

Puchi , 1983.