Steel mill bearings Roll neck bearings for rolling mill Roll neck bearings for rolling mill This catalog has been printed on paper of recycled paper pulp using environmentally friendly soy ink.

Preface In 1943, JTEKT supplied bearings for rolling mills as the rst domestic manufacturer in Japan. Since then, JTEKT has been cultivated advanced technology and technical know-how with customers. To meet with customers’ requests, JTEKT strives for development of more highly precise and reliable bearings for rolling mills while using experience and actual achievement for technical development and research. JTEKT will do a service by customer-oriented “monozukuri” (Japanese way of manufacturing) in the future. Features of JTEKT products 1 High precision JTEKT’s highly precise bearings contribute...

Operating environment of bearings for rolling mill Bearings in every industry are used under various kinds of severe conditions. For instance, bearings used in automobiles, railway stocks, and aircrafts are required to have ultimate reliability, as due to safety reasons, they are never allowed to fail during operation. While bearings used in machine tool spindles are required to have ultra-high rotational speed performance and high running accuracy. In these examples, operating environment is not so severe. Meanwhile, bearings for rolling mills must withstand heavy load and high speed rotation,...

Roll neck bearings for rolling mill and relevant products Four-row tapered roller bearing Four-row cylindrical roller bearing Sealed type These bearings, mainly used for work rolls or intermediate rolls, carry both of radial load and axial load at a time. Adjustment of internal clearance is not required, facilitating handling. Open type is also available. Open type These bearings, used for back-up rolls, have a superior large radial load capacity, and are suitable for high-speed rotation. Rolling accuracy can be improved by applying the tight tting of the inner ring onto the roll journal, and...

Sealed type four-row tapered roller bearing Features 1. Substantial reduction in grease consumption (compared to open type) 2. Extension of overhaul and cleaning intervals 3. Prevention of intrusion of rolling mill oil and/or scale 4. Reduction in harmful effects on working environment [compared to open type (grease lubrication, oil mist lubrication)] A. Seal cover with seal and O-ring B. Seal between inner rings Seal with spring and O-ring prevent intrusion of rolling mill oil and scale causing leak of packed grease in the bearing. Newly-developed compact seal increases the load rating to 1.2...

Features of new products Extended service life of sealed type four-row tapered roller bearing JTEKT has developed the sealed type four-row tapered roller bearing with oil seals integrated for reduction of grease consumption and prevention of intrusion of foreign matters (rolling mill oil or scale) of rolling mill bearings, and contributed to reduction of pollution of surrounding environment due to grease leak and elimination of re-greasing. However, due to the extended overhaul and cleaning intervals, the damage due to their intrusions (wear and/or rust on raceway) has recently occurred. Therefore,...

Long-life, high corrosion-resistant steel When rolling mill oil intrudes into the bearing, intrusion may cause rust between the raceway and the rollers, from which aking is initiated. Also, the breakage of oil lm due to the intrusion of rolling mill oil may cause wear on the rolling surfaces of raceways and rollers, from which surface-initiated aking may occur. In order to improve both problems, JTEKT has developed a new long-life, high corrosion-resistant steel with optimized content of chromium and molybdenum. Additionally, original carbonitriding heat treatment has improved corrosion-resistance...

Replacing oil film bearing with rolling bearing In 1972, JTEKT adopted four-row cylindrical roller bearings for new cold tandem mill tandem back-up rolls (BUR) at rst in Japan. Since then, JTEKT has supplied bearings for BUR to many steel manufacturers all over the world. Since JTEKT carried out the modication design and delivered rolling bearings for the modication of the plate mill by replacing the oil lm bearing of the back-up roll with the rolling bearing in 1984, JTEKT has completed about twentyve projects (maximum record in Japan) until 2007 and has contributed to offer highly-precise products...

Bearing failures, causes and countermeasures Characteristics Flaking caused by excessive axial load Flaking Causes (Inner ring of four-row tapered roller bearing) (Outer ring raceway of four-row tapered roller bearing) Flaking caused by improper mounting Loading position (1) Flaking on bearing raceway surface generated on only rows receiving axial load 1) Crossed work rolls causing excessive axial load · Roll neck diameter is smaller than the standard one. · Chock side liner is worn. · Inaccuracy of mill stand. · Rigidity of the chock is poor. · Corrosion on liner or clearance generated between...

Bearing failures, causes and countermeasures Characteristics Flaking at corroded start point Flaking on raceway surface started from corroded (rusted) portion Flaking Causes (Outer ring raceway of four-row tapered roller bearing) Flaking on nicks (scratch) start point Countermeasures (Rolling contact surface of four-row cylindrical roller bearing) (Inner ring raceway of double-row cylindrical roller bearing) Cracking Chipping (Inner ring side face of four-row tapered roller bearing) 1) After the bearing was used, it has been left for a long period with moisture mixed in grease. 2) Improper rust...

Cracking Chipping (Rolling contact surface of four-row cylindrical roller bearing) Causes (Inner ring raceway of four-row cylindrical roller bearing) Cracking on rolling elements 1) Application of load greater than bearing load rating (Load resistance of roller by use of pin type cage) 2) Secondary factor in case of damaged pin of cage (For a reversible mill, pins are broken due to fatigue caused by rapid acceleration and deceleration) 3) Other factors · Ingress of water due to faulty sealing. · Increase of axial clearance of bearing, causing application of partial and excessive load. 1) Optimal...