| Advanced technology and suitable equipment are employed for Skin Pass rebuilding inl450 hot strip mill of Panzhihua iron&steel (Group)Co. The rebuilt Skin Pass can be used to unknit carbon steel and alloy steel strip in normal temperature, and can enhance the strip surface quality, ensure expectant strip shape and increase mechanical characteristics of the strip. The machine can also be used for shear striping.An electro-hydraulic servo system can provide control power for press and bend-roller equipments of Skin Pass. The electro-hydraulic servo system consists of pump groups, accumulators, control valves, hydraulic cylinders, various sensors and relays, pipelines and so on. The advanced technology and suitable equipment are integrated in the item of Skin Press rebuilt, that include automatic control, automatic sensing and detecting, strip shape control, extension rate automatic control. Position control is used for the adjustment of gap between two rollers in the Skin Pass while machine is demarcated or the steel trip is pulled in, so that, the gap between two rollers can be closed and opened according to the control demand. It can also ensure the synchronizing motion of two hydraulic cylinders in both side of the Skin Press. Pressure control is used for rolling press force control and bend-roller force control. The controls are used to eliminate the accessory clearances and odd contact of Skin Pass. Constant press force control is employed to supply uniform pressure in whole strip wide in order to obtain uniform strip thick in whole press operation. Bend-roller force control can be positive or negative, so that it can compensate gap changes between two rollers due to the pressure variety, and can rectify the errors of middle-wave and double wave in press operation. Extension rate control of the strip is obtained by pressure control, and the rate control can mend the strip surface quality, and can also increase the strip mechanical characteristics.The hydraulic press operation of the Skin Pass is driven by hydraulic cylinders controlled by hydraulic valve. Whole system performance is rests withthe dynamic characteristics which relate to hydraulic valves, hydraulic cylinders and loads. In system analysis, the system is considered as a concentrating parameter one, and the loads mainly consist of mass force, spring force and damping force. While the control system works, all the control errors taken place between the variables and its steady state values are relative tiny, so that, classical control theory can be used to solve the actual control problem of Skin Pass operation. |
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