The Design of Rolling Bearing Mountings

Work rolls for the finishing section of a105 four-high hot wide strip millWork roll bearings are often exposed to large amountsof water or roll coolant. In addition, considerableamounts of dirt have to be accommodated in hot rollingmills. Therefore, the bearings must be efficientlysealed. As a rule, they are lubricated with grease, whichimproves sealing efficiency. Operators of modern rollingmills endeavour to reduce grease consumption anddamage to the environment caused by escaping greasewateremulsion.Operating dataRoll body diameter 736 mm; roll body length2,235 mm; rolling speed 3.5...15 m/s.Bearing selection, dimensioningFour-row tapered roller bearings have proved to be agood choice for work rolls. They accommodate notonly high radial loads but also thrust loads, and theyrequire only little mounting space. The bearings have asliding fit on the roll neck, allowing rapid roll changes.In the example shown, sealed four-row tapered rollerbearings FAG 563681A (dimensions 482.6 x 615.95x 330.2 mm) are used.The service life of work roll bearings is mainly dictatedby the loads, rolling speed, lubrication and cleanliness.Open bearings, as a rule, do not reach their nominalrating life due to adverse lubricating and cleanlinessconditions. On the other hand, the modified life calculationfor sealed bearings usually yields a 23 factors > 1,i. e. the attainable life exceeds the nominal rating life.In spite of the lower load rating, the value is generallyhigher than that reached by an open bearing of thesame size.Lubrication, sealingThe bearings are filled with relatively small amounts ofhigh-quality rolling bearing grease. On each side theyfeature a double-lip rubbing seal. The inner lip preventsgrease escape from the bearing; the outer lip protectsthe bearing from moisture that might have penetratedinto the chock. No relubrication is required duringrolling operation and roll change. The amount ofgrease provided during assembly usually suffices for theduration of one chock regrinding cycle, i. e. for1,000...1,200 hours of operation. The chocks are fittedwith the conventional external seals (collar seals).These are filled with a moderately priced, environmentallycompatible sealing grease.105: Work roll mounting for the finishing section of a four-high hot wide strip millFAG 148