Analysis of Slab Temperature Change and Rolling Mill dine Length in Quasi Continuous Hot Strip Mill Equipped with Two Roughing Mills and Six Finishing Mills

Abstract

SynopsisThe length of the rolling mill line and the slab temperature change are theoretically compared between the quasi continuous type equipped with 3 rougher mills, of which the first one is reversible, and 6 finisher mills and the quasi continuous 4 passes type equipped with 2 rougher mills, of which the first is reversible, and 6 finisher mills for a mathematical model that a slab is rolled from the initial thickness 230 mm to the final thickness 2.5 mm.In the quasi continuous 4 passes type, the total length in the roughing process can be shortened to about 60% compared with the case of the quasi continuous type. For a given reheating temperature, the slab temperature at the entrance of the first finisher remains much higher in the quasi continuous 4 passes type so that the reheating temperature can be reduced over 100°C. Finally, one conclusion is that the quasi continuous 4 passes type is much profitable not only for the shortness of the rolling mill line but also for the energy saving in the rolling process.

Thermo-mechanical modeling of two phase rolling and microstructure evolution in the hot strip mill

“…Devadas and Samarasekera [9] used this relation and obtained a value 21 kW/m 2 K. They observed that this value matched with data published [20] for high-pressure water sprays whereas Sasaki's relation was based on low pressure water sprays. HTC values used by various investigators [9,15,21,22] lie in the range 1.16-25 kW/m 2 K. Sasaki's relation could not be used in the present study because of insufficient mill data. However a heat transfer coefficient value of 2 kW/m 2 K was found appropriate in simulating plant data.…”

An integrated thermal model of hot rolling

“…As the experimental conditions differ significantly, the results are also very different, e.g., constant heat transfer coefficients in the range from 1162 W/(m 2 K) to 20,920 W/(m 2 K) are reported in [7] and [23], respectively. A dependence of the heat transfer coefficient on the impact pressure is suggested in [24], where different constant values from 2000 W/(m 2 K) to 8000 W/(m 2 K) are used for different levels of spray pressure.…”

“…In some cases, e.g., [4,7,23], the contact problem is solved analytically. However, the analytical solution can only be derived, if some assumptions are made, including that the plate and the work roll are two semi-infinite solids in perfect contact with homogeneous initial temperature profiles.…”

“…This velocity difference increases near the entry (backwards slip) and the exit region (forwards slip) of the roll gap, which causes higher heat fluxes in these regions. To model the shear stress due to friction, three different approaches are used: the Coulomb friction model [2,3,23,24,34], the Tresca friction model [36,46], and the Wanheim-Bay friction model. They are compared in [48,49].…”

“…They are compared in [48,49]. The generated heat is sometimes equally distributed to the work roll and to the plate [5] or mainly allocated to the plate [4,23].…”