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Research Papers

Development of Statically Determinate Plate Rolling Mills That Maintain the Rolls Parallel

[+] Author and Article Information
Guangxian Shen

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208;
National Engineering Research Center for Equipment and Technology of Cold Strip Rolling,
Yanshan University,
Qinhuangdao, Hebei 066004, China
e-mail: sgx35@ysu.edu.cn

Yongjiang Zheng

e-mail: zhengyongjiang123@163.com

Ming Li

e-mail: liming@ysu.edu.cn
National Engineering Research Center for Equipment and Technology of Cold Strip Rolling,
Yanshan University,
Qinhuangdao, Hebei 066004, China

Contributed by the Manufacturing Engineering Division of ASME for publication in the Journal of Manufacturing Science and Engineering. Manuscript received June 29, 2012; final manuscript received March 13, 2013; published online May 24, 2013. Assoc. Editor: Brad L. Kinsey.

J. Manuf. Sci. Eng 135(3), 031014 (May 24, 2013) (8 pages) Paper No: MANU-12-1194; doi: 10.1115/1.4024039 History: Received June 29, 2012; Revised March 13, 2013

The design theory of a statically determinate rolling mill, including the redesign of the statically indeterminate characteristic and hyperstatic characteristic, is proposed in this paper. The statically indeterminate characteristic leading to the nonparallel running state of rolls is revealed based on analysis of three rolling mills, including a 2200 mm aluminum foil four-high mill, a 1580 mm PC four-high mill, and a 650 mm bar two-high rolling mill, etc. The hyperstatic characteristic leading to uneven load performance of four-row roller bearing is caused by redundant constraints in the roll system based on analysis of 17 two- and four-high rolling mills. In contemporary four- or six-high plate rolling mills, regular dynamic cross between the rolls is very common during the whole rolling process. Dynamic cross results in excessive axial forces causing frequent burning losses of the end-thrust bearings and leads to serious deviations in the rolling load on both ends of the backup roll. Hence, rolling mills designed for heavy loads and high speeds have yet to operate at their design load and speed in a safe and stable way. According to the analysis of the degrees of freedom of a spatial mechanism, the cause of dynamic cross lies in the statically indeterminate characteristic of the roll system caused by the small clearance in the system. In this paper, the theoretical analysis and experiments invalidate the accepted method of the offsetting of the mill. Furthermore, it is shown that offsetting causes an asymmetrical cross between the rolls. Therefore, it is proposed that offsetting should be eliminated, and additional jack devices should be introduced to maintain the rolls parallel. In addition, bending deflections of the roll induce hyperstatic characteristics of the roll system due to the existence of redundant constraints in the system. The hyperstatic characteristic of the roll system results in uneven load performance of the radial roller bearings and shortens bearing life. In the newly proposed statically determinate four- or six-high plate rolling mill, which can be operated in a safe and stable way under heavy load and high speed working conditions, this problem can also be solved.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Lower BR system of the 2200 mm aluminum foil four-high mill and its skeletal structure

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Fig. 2

Invalidation of the mechanism of offsetting in the 2200 mm aluminum foil four-high mill

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Fig. 3

Plots of axial force over time in the 2200 mm aluminum foil four-high mill

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Fig. 4

Dynamic cross due to gyroscopic effects

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Fig. 5

Experiment for testing the effect of offset distance in the zero setting of the roll gap to confirm the initial cross: (a) one-twelfth simulator of the rolling mill, (b) simulator diagram, and (c) displacement-load curve of the WR

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Fig. 6

Asymmetric and symmetric cross between the roll axes: (a) ideal position of the roll axes, (b) the first kind of cross state of the roll axes, (c) the second kind of cross state of the roll axes, and (d) symmetric cross between the roll axes without offset distance

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Fig. 7

Hyperstatic structure with microbending deflections of the rolls in the 600 mm UC six-high mill

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Fig. 8

The skeletal structure of the BR system

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Fig. 9

The design of the skeletal structure of the statically determinate BR system: (a) during running at idle and (b) during rolling

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Fig. 10

The roll systems in a four-high mill

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Fig. 11

The roll systems in a six-high mill

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Fig. 12

Worm-screw jack device to prevent cross in a four-high mill

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Fig. 13

Hydraulic jack device to prevent cross in a six-high mill

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Fig. 14

Redesign of the hyperstatic BR system

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Fig. 15

The load distribution in the roller bearing of the BR system: (a) in a hyperstatic structure, (b) in a statically determinate structure, (c) radial load distribution of row 1 of the bearing, and (d) load distribution ratio of each row along the roller bearing axis

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Fig. 16

(a) New transfer mode of the rolling load and (b) the radial load distribution of the roller bearing

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