Po. Aiyedun et al., TEMPERATURE-CHANGES IN HOT FLAT ROLLING OF STEELS AT LOW STRAIN RATESAND LOW REDUCTION, Proceedings of the Institution of Mechanical Engineers. Part B, Journal of engineering manufacture, 211(4), 1997, pp. 261-284
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 (simi
lar to 10 per cent) for a hot flat rolled slab both during air cooling
and during roll contact has been used in conjunction with experimenta
lly measured temperatures through specimen thickness during roll conta
ct after reheating to temperatures in the range 1000-1200 degrees C fo
r mild steel, low carbon SS316 and high carbon SS316 (with Nb, V and T
i). At high strain rates (similar to 1.5 s(-1)) a steep temperature gr
adient was produced in the specimen near the surface whereas for low s
train rates (similar to 0.08 s(-1)) this temperature gradient penetrat
ed deep into the thickness, leading to a large drop in the mean rollin
g temperature. Roll chilling, leading to higher values of the Zener-Ho
lloman parameter, Z, resulted from a decrease in the mean rolling temp
erature and the large temperature gradient during roll contact. Temper
ature changes due to material composition, reheating temperature, cont
act time and rolling conditions led to precipitation strengthening and
roll chilling effects which have accounted for the excess load and to
rque observed experimentally and industrially.