Papers by Keyword: Work Roll

Abstract: Next generation rolls such as super-cermet rolls and all-ceramic rolls can be manufactured using only sleeve assembly type rolls, which have the advantage of being able to reuse the shaft by replacing the damaged sleeves. However, in some cases, failures with unknown causes may occur such as circumferential slippage, shaft pull-out or residual bending deformation at the shrink-fit interface. Such slipping failures cannot be prevented by conventional design concept. This is because even if the resistant torque is greater than the motor torque, the circumferential slippage will occur. Through numerical simulation and miniature roll experiment, the following results are obtained. 1) Even under free rolling condition without motor torque, the circumferential slippage occurs. 2) The slippage is caused by the accumulation of irreversible slip during the roll rotation. 3) The motor torque accelerates the sip amount significantly. 4) The geometry of slippage defect can be identified experimentally. 5) The fatigue strength of sleeve assembly rolling rolls can be evaluated by using √area parameter characterizing the identified slip defects. 6) By preventing the slip damage, the fatigue strength of sleeve rolls can be nearly equal to that of conventional solid rolls without shrink-fit.

Abstract: The microstructure and mechanical properties of the work roll grade acicular nodular cast iron supplied by two different manufacturers were studied and compared. These rolls have different chemical compositions, namely work roll A and work roll B, respectively. This work aims to evaluate the two different work rolls with different chemistry and the effect on the microstructure and hardness. The microstructure was observed by the optical microscope and image analyzer, and the hardness value was measured using a Rockwell hardness machine. The results showed that the work roll A presented more carbides and graphite nodules than B. Carbide area fraction and nodularity level of work roll A are found much higher than B; therefore, it provided a higher hardness. It seems a higher percentage of carbon and proper amount of magnesium as a nodulizer contributed to produce more carbides and nodules on the cast iron of work roll A compared to B.

Abstract: Hot strip rolling process is one of the most promising industrial processes to fabricate finished or semi-finished bulk products. Numerical analysis on the temperature and thermal stress distributions in a high speed steel work roll during hot rolling has been conducted based on a transient thermo-mechanical model. Influence of initial work roll body temperature on temperature and thermal stress has been discussed in detail by assuming different rolling stages. Compared to the work roll surface, stress is much smaller at depth of 2.1 mm and 5.0 mm, respectively. Results showed similar maximum circumferential thermal stress at both depths of 2.1 mm and 5.0 mm when the roll has initial temperature of 25 °C and 100 °C, but they are about 3 times and 8 times larger than at depth of 2.1 mm and 5.0 mm, respectively, when the initial temperature is 200 °C.

Abstract: Based on nonlinear damping and stiffness consideration between not only work rolls but also back-up roll and body frame, five times frequency flutter model of rolling mill was built according to actual structure of rolling mill, which followed by simulation analysis. Some theoretical guidance can be provided for practical engineering application.

Abstract: It was analysed that the causes for the poor wear resistance of roller, fracture of roller and the surface of the roller flaking off were researched. Introducing CSP plant carried through technical and improved works about work roll material and using system in order to improve strip quality and decrease producing costs. It’s effective to resolve wear and breakage and spalling of the work roll and improve profile control and so on.

Abstract: Computational models of deformation and friction work were established by dividing contact arc between strip and work roll into two sliding regions, two braking regions and one stagnating region. A two dimensional temperature field model of work roll was established by finite difference method according to practical boundary conditions. Simulation results show that with the increase of rolling pass, deformation work reduced while friction work increased, except that deformation and friction works at the last pass were the least. The computed rolling forces and work roll surface temperatures agree well with measured values collected from a hot strip mill.

Abstract: This paper focuses on a new type of 8-roll cold rolling mill with the back-up bearing roll. Compared to the traditional 6-roll cold rolling mill, a thick-walled bearing roll is used to multi-support the intermediate roll. By the rack, the fan-shaped gears, the eccentric core shaft and the servo-cylinder, the work roll can be pushed down by this screw down device on the top of the mill; By contrast with the 4(6)-roll mill, this type of mill has some characteristics, such as: the small size of rolls, lighter weight, the fast response for the screw down. The bearing roll is fixed by the supporting blocks placed on the rolling-mill housing. So this mill has large traverse rigidity, and this is propitious to the flatness control. By different means of strip flatness adjustments, such as the intermediate roll shifting, the roll bending and the bearing roll adjusting, the strip flatness can be well controlled. The oil-gas lubrication is used in the bearings of the bearing rolls, and the changing rolls equipment is designed for this type of mill too. A series of this type of mills (as 450, 800, 1250, 1450 series) have been produced since it was developed in 1997. The mills for 1250 and 1450 series have been applied in five-stand cold rolling mill and single stand reversing mill, a rolling speed of 800m/min has been achieved.

Abstract: A roll barrel breakdown accident took place on CSP mill. After investigating of the accident scene and the roll service condition, analysing the barrel fracture and sampling tests, proved that main cause for the roll breakdown was unusual and there appeared a strip-like crack on the boundary layer resulting from the initial flaws extending along the roll circle direction; furthermore, the flaws caused fatigue breakage along the roll inner cross section, which resulted in the barrel breakdown.

Abstract: In the unsteady state, work roll temperature distribution and thermal expansion have an enormous effect on the process of hot rolling. The rolling speed in the finish rolling as an important rolling parameter plays a crucial role of obtaining the optimum temperature distribution and thermal expansion. Using the finite element method, it solves the regularity of temperature distribution and thermal expansion with thermal-structural coupling analysis, which provide theoretic proof of optimizing gauge and profile control.

Abstract: SmartCrown work roll contour has been brought in China for several years, but the research of crown control characteristics of SmartCrown work roll is lacking, especially the relationship and difference between SmartCrown and CVC work rolls. The paper researched the principle and design method of SmartCrown work roll contour first, and then the relation and difference between the SmartCrown and CVC work roll contours were pointed out, the crown control ability of different strip width was discussed too. From the analysis and research, it can be concluded that the contour angle of SmartCrown work roll contour is the most key factor for its crown control characteristics.