The shape of the plate is one of the important quality indicators of the plate and strip products. Therefore, the profile control in the production process is a crucial issue. With the HC six-high mill, the birth of the VC-convexity rolling mill and the development of the plate shape control technology, the high degree of automatic control of the plate shape has been achieved, and the accuracy of the plate shape has been improved. However, the investment of these rolling mills is relatively large. For ordinary rolling mills, reasonable adjustments must be made to the process parameters to achieve effective control. The technical personnel of our company have gradually summed up a series of effective methods through many years of actual production experience. The following mainly discusses several factors that control the shape of the cast blank in the Ф380/Ф1050×1800 four-roll irreversible rolling mill.
A number of factors that affect the shape of cast slab
1. Influence of cast roll type. The continuous cooling water in the casting roll removes the heat that is released when the aluminum liquid solidifies. At present, most of the domestic continuous casting and rolling mills use open cooling circulation systems. The water quality does not reach the softening requirements or mechanical impurities in the water may block the cooling channels of the roller core, resulting in uneven cooling strength on the cross section of the casting roller, which affects the casting. Rolling blanks horizontal difference (as shown in Figure 1). Therefore, in the production of casting and rolling, while guaranteeing the accuracy of assembly of the casting roll and accuracy of grinding, it is necessary to adopt a closed softened cooling water system as far as possible so as to avoid clogging of the roll core and affecting the plate shape.
2. The matching gap between the casting roll sleeve and the roll core is not uniform. The low precision of machining or the core corrosion during use will cause the gap to be uneven, so that the cooling is not uniform. In this case, the core of the welding roller must be removed.
3. Casting roller bearing clearance should be moderate, generally controlled in the 0.3 mm - 0.35 mm, if the gap is too small, affecting the bearing life, if the gap is too large will affect the longitudinal blanking of the casting blank.
4. The mouth opening and lip thickness of the casting nozzle should be as uniform as possible. For horizontal type continuous casting and rolling mills, the pressure force of the pressure plate should be uniform when installing the casting nozzle
5. Maintain a certain amount of prestress before the riser to eliminate the elastic deformation of the arch. The setting of prestress is generally two-thirds of the rated rolling pressure.
6. Drive side and operating side rolling pressures. Through a certain range of pressure adjustment, the horizontal thickness difference of the cast slab can be controlled within the specified range, so as to ensure the favorable control of the plate shape. For different rolling mills and different grades of products, the rolling pressure is proportional to the cast slab. The thickness effects are different.
7. Tension. The proper tension can flatten the tension of the plate to a certain extent, reduce sticking and improve the plate shape.
So the shape of the plate depends on whether or not the strips extend in the width direction. This condition is determined by the uniformity of the cross-sectional thickness of the blank prior to rolling and the shape of the roll or actual roll gap opening. In the production process, it is necessary to control the shape of the cast blank, and at the same time, it is necessary to properly match the original crown of the work roll, the amount of reduction, the positive and negative bending rolls, the rolling speed, the tension and the cooling strength according to the conditions of the equipment in the cold rolling process. And other process parameters.