Vertical Vibration Analysis Of CSP Hot Strip Mills

At the end of last century, Handan Iron and Steel Group introduced a set of thinstrip continuous casting and rolling production line from the German SMS DemagCompany. The production line utilized the latest production technology in the worldsteel industry (Compact Strip Production, simplified as CSP). The system consists of6finishing mills. Since it was formally put into production at the beginning of thiscentury, vibration often occurred on rolling system. Especially, the vertical vibrationof F3rolling mill is most serious. Once the vibration occurred, it is very necessary toreduce the rolling speed to coercion the vibration stability of the system. This may seta huge impact on the product quality and production.The article analyzed the vibration of F3rolling mill, which has the most seriousproblem on the vertical vibration. The main research includes the following aspects:(1)A simplified vertical vibration model of F3CSP hot strip mill with sixdegrees of freedom was established. Then the model was analyzed with the help ofMATLAB and the analysis result was that the rolls would vibrate at the frequency of124Hz and600Hz and the vibration would cause light and dark chatter marks on thestrip. And the vibration would also cause the self-excited vibration of rolling system.(2)A virtual solid model F3rolls was establish in Pro/E, and was imported intothe ANSYS for modal analysis. Analyzing results revealed that the vibration modeshapes of F3finishing mill was the bent of rolls and the swelling of the roll diameterin the natural frequency of560Hz and130Hz, This deformation would causes thechange of roll gap and then exert chatter marks on the strip.(3)The principle of high-frequency and low-frequency vertical vibration of themill was discussed. Resonance analysis with parameters of F3finishing mill was doneand the result revealed that increase the stiffness, reduced rolling speed, increase thespacing between the rack, reducing the amount of reduction, etc. can improving thestability of the system. Thus high-frequency and low-frequency vertical vibration ofrolling system would be controlled.(4)According to the impact that emulsion exerted on the vibration of finishingmill, the lubrication mechanism of rolling lubrication process was studied. A vibrationmodel of F3finishing mill established with consideration of the state of lubrication, and the influence of emulsion performance, concentration exerted on the stiffness F3finishing mill was analyzed. Through the analysis, we know that the stiffness of F3finishing mill could be increased by selecting a suitable emulsion and change theperformance of the emulsion and then the vibration could be avoided or controlled.