Journal of University of Science and Technology Beijing
Volume 14, Number 6, December 2007, Page 1
Corresponding author: Jiangbo Dai, E-mail: zhang_qd@me.ustb.edu.cn Also available online at www.sciencedirect.com
Materials
FEM analysis of strip large thermo-deflection being processed
in continuous annealing furnace
Jiangbo Dai, Qingdong Zhang, and Tiezhu Chang
Mechanical Engineering School, University of Science and Technology Beijing, Beijing 100083, China
(Received 2006-12-11)
Abstract: No matter what the flatness of strip isflat or defective at an annealing furnace entrance, strip can not keep its original
shape and a remarkable large deflection took place at the annealing furnace exit. By investigating this phenomenon at 2030, conti-
nuous annealing line which belonged to Baosteel, the Finite Element Model of strip thermodynamics behaviors in continuous an-
nealing furnace were established, the mechanism of flatness changing and the contributing factors were researched by the popular fi-
nite element software—ANSYS. Conclusions were achieved from the study, and they proved to be instructive in decreasing strip
heat-buckling on the 2030 continuous annealing processing line and hot galvanizing line.
Key words: annealing furnace; thermo-deflection; finite element simulation; strip
1. Introduction
Large deflection of strips happens easily and comes
into being a new strip profile that is obvious when it is
heated up and refrigerated on the strip continuous an-
nealing production line (CAPL) or strip continuous
galvanizing production line (CGL). Tables 1 and 2 are
the actual measured values of coils produced in Baos-
teel 2030 Cold Mill CAPL and CGL in July and Au-
gust, 2004, they were the statistical results of strip
profile changings when the strip traversed from the
annealing furnace entrance to the annealing furnace
exit, the tables show the remarkable transformations
of strip shape. The strip often happened due to the
phenomenon of “heating-buckling”, in the worst case,
it was ruptured in the annealing furnace. These phe-
nomena influenced the product quality, output, and
stability of the production process. The problems were
the great technical problems in many such production
lines at present. In order to explore the mechanical
mechanisms and seek the solutions about the problems,
the thermodynamic investigations of strips were de-
veloped in the annealing furnace based on the Baos-
teel 2030 continuous annealing and galvanizing set in
this article.
The researches indicate that the strip deflection in
the annealing furnace mostly lies on its temperature,
tension, deflector roll profile, strip original shape, of
course, as well as the strip specification and the capa-
bility of the material. The strip speed was almost
steady in the continuous annealing furnace, so in this
article the speed that exerted an influence on strip
buckle was not considered.
Table 1. Measured profile shape corresponding probability
at the entrance and exit of the annealing furnace on the
2030 CGL
2. Distribution of the strip temperature and
tension in a continuous annealing furnace
2.1. Distribution of the strip tension
The strip tension was obtained from the speed ad-
justments of bridle rolls. There were few measuring
points of tension in a continuous annealing furnace.
On the basis of the research of Ref. [1], the distribu-
tion of the strip tension is shown in Fig. 1, and the
strip tension is the smallest at the entrance of furnace.
The longer the strip traveled in the furnace, the larger
the strip tension would be. The strip tension is the
largest at the exit of the furnace.
Table 2 Measured profile shape corresponding probability at
the entrance and exit of the annealing furnace on the 2030
CAPL
Fig. 1. Strip tension rule in the annealing furnace
[1]
Fig. 2. Distribution of the strip transverse temperature at
each pass in the heat chamber
[2]