Journal of University of Science and Technology Beijing
Volume 15, Number 3, June 2008, Page 352
Materials
Corresponding author: Jianguo Cao, E-mail: geocao@me.ustb.edu.cn Also available online at www.sciencedirect.com
© 2008 University of Science and Technology Beijing. All rights reserved.
Work roll thermal contour prediction model of nonoriented
electrical steel sheets in hot strip mills
Ningtao Zhao
1)
, Jianguo Cao
1)
, Jie Zhang
1)
, Yi Su
2)
, Tanli Yan
2)
, and Kefeng Rao
2)
1) School of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083, China
2) Wuhan Iron and Steel Company, Wuhan 430083, China
(Received 2007-05-12)
Abstract: The demands for profile and flatness of nonoriented electrical steels are becoming more and more severe. The temperature
field and thermal contour of work rolls are the key factors that affect the profile and flatness control in the finishing trains of the hot
rolling. A theoretic mathematical model was built by a two-dimensional finite difference to calculate the temperature field and ther-
mal contour at any time within the entire rolling campaign in the hot rolling process. To improve the calculating speed and precision,
some special solutions were introduced, including the development of this model, the simplification of boundary conditions, the
computation of heat transfer coefficient, and the narrower mesh along the edge of the strip. The effects of rolling pace and work roll
shifting on the temperature field and thermal contour of work rolls in the hot rolling process were demonstrated. The calculated re-
sults of the prediction model are in good agreement with the measured ones and can be applied to guiding profile and flatness control
of nonoriented electrical steel sheets in hot strip mills.
© 2008 University of Science and Technology Beijing. All rights reserved.
Key words: hot rolling; rolls; temperature distribution; mathematical model; finite difference method
1. Introduction
Low grade nonoriented electrical steel is an excel-
lent soft magnetism functional material that has the
biggest production and wide application in the elec-
trical steel production area. With the electrical steel
company improving the automatization level and
market competition becoming furious, the demands
for profile and flatness of nonoriented electrical steel
sheets are becoming more and more severe. Through
systemic tracking tests and theory investigation, it has
been found that hot rolling is a key procedure for pro-
file and flatness control of cold-rolled nonoriented
electrical steel [1-2]. The temperature field and ther-
mal contour of work rolls are key factors that affect
the profile and flatness control in finishing trains of
hot rolling [3]. Therefore, it is important to develop a
work roll thermal contour prediction model and study
the thermal behavior properties of the work roll in the
nonoriented electrical steel hot rolling process and to
finally instruct profile and flatness control of electrical
steel.
2. Temperature field and thermal contour
model
For calculating the thermal contour of a work roll,
the temperature field must be solved first. Generally, a
1-dimension, 2-dimension or 3-dimension model
could be developed, to solve the temperature variety
separately or synchronously along the radial, axial or
circumferential orientation. Investigations show that
although the temperature in 2-3 mm depth of roll sur-
face changes drastically, inside it is mostly axis sym-
metric and the heat conduction along the circumferen-
tial orientation can be ignored [4-5]. The demands for
profile and flatness of electrical steel are very strict
and the rolling campaign has 60-80 coils, generally 50
pieces less than that of common steel sheets. For
meeting the high precision, a 2-dimension axis sym-
metrical model was developed by using the finite dif-
ference method. In this way, the model can not only
simplify the problem and meet the real applying pre-
cision, but also improve the calculating speed, to make
it possible to be applied to the real online process con-