Structural Optimization Of Roll System For Finishing Mill Group 2050 And Analysis Of Its Stability

CVC mill, launched by German company SMS in 1984, is a new kind of mill which has a continuously variable roll crown and a good shape controlling capability. Founded and put into operation in 1989, Baosteel 2050 unit is a wholesale introduction of SMS technology and equipment of the modern hot continuous rolling strip production line. Hot Rolling Finishing Mill 2050 is a four-high CVC mill with S-shaped curve of the working rolls equipped by axial movable devices. It adjusts the roll gap by changing crown of the working rolls. Four-row roller bearings on the working rolls mainly bear roll-bending force and axial force, while the oil film on the backup roll mainly bear rolling force and most of the bending moment. With the rolling load and rolling speed increasing, effects of the mill's dynamic impact, vibration and wear on the components become increasingly important. It greatly affects the stability of roll system.Making the problems in the 2050CVC roll system of Baosteel Hot Rolling Plant the breakthrough point, and with the purpose of optimizing roll system structure and improving the stability, this paper systematically summarizes applications and technical characteristics of the CVC mill, and raise up some help to improve the stability of roll system based on the practical problems during production, mainly discussed the following:1. This chapter introduces the working principle and structural characteristic of CVC mill; studies the typical structure of roll-bending and axial movable devices; points out that roll axis crossing is the main reason for producing axial force; and proposes the measures of solving a series of failures caused by too large mill axial force.2. This chapter introduces the structural feature and problems of original combined bearing used in 2050CVC finishing mill work roll; proposes using a large cone angle four-row tapered roller bearing as a new bearing design; and checks the life of new bearing. Changing regularity of load on each roller has been obtained by the finite element analysis on work roll bearings and bearing chock using SolidWorks, HyperMesh and MSC.Marc comprehensively. Finally, features of column load distribution of combined bearing and axial force have been obtained by experimental studying on dynamic operation behavior of rolling bearing. It also provides an experimental basis for implementation of the new bearing design.3. This chapter introduces the work roll axial sliding, locking mechanism and hydraulic control system of Baosteel 2050CVC finishing mill; systematically discusses the common mechanical and hydraulic failure of CVC mill, and analysis such common failures using fault tree analysis method. The establishment of fault tree relation model has greatly improved the efficiency of fault diagnosis and maintenance programs mend, saves the repairing down time.4. This chapter introduces the structural features of Baosteel 2050 backup roll unit and the sealing structure of film bearing; Develops relevant technical measures to avoid influent water in oil film bearing, and designs a waterproof cover to avoid direct impact of water on seal device. This technical measure has achieved remarkable effect in the rolling line which can guarantee to determine influent water spots and its causes in a very short period of time. It essentially avoids the occasional phenomenon of influent water caused by intrusion of a large number of water entrained oxide scale.