Schaeffler Doubles Service Life With New Rolling Bearing Material

Mixed friction or contamination with foreign particles are conditions as they occur in the steel industry, mining or also in railway technology. Heavily reduced service lives of the bearings or early failures can cause very high follow-up costs. The conflict of objectives to be resolved: On the one hand, the careers have to be hard, wear-resistant and stable. On the other hand, they should be able to tolerate the introduced deformations due to hard foreign particles when rolling over and, if necessary, even out. Schaeffler has solved this conflict of goals between great hardness and sufficient ductility with the Mancrodur bearing steel in conjunction with the carbonitriding heat treatment.

Mancrodur carbonitrided has an extraordinary combination of properties that make this rolling bearing material ideal for particularly difficult environmental conditions:

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• Due to the heat treatment - a combination of carburizing and nitriding - the surfaces of the Mancrodur bearings are hard and wear-resistant.
• On the other hand, Mancrodur produces carbonitrided fine and spherical carbides that are evenly distributed in the material and are little concentrated on the grain boundaries. The risk of local vulnerabilities is reduced. The raceway surface is not only harder and more wear-resistant, but also more ductile.

In spite of its high surface hardness, Mancrodur is able to level the surface of the track with foreign particles. Material fatigue is significantly delayed, cracking is prevented and the service life is significantly extended.

With insufficient lubrication, the temperature of the material increases locally due to the higher friction. Compared to other steels, the temperature-related drop in strength at Mancrodur is smaller, so that the risk of local overload due to insufficient lubrication is significantly reduced.

Under normal lubrication conditions (full lubrication), the carbonitrided Mancrodur offers an increase in the basic load rating of 30% compared to the standard material, which is equivalent to an increase in the nominal service life of 240%. In test series with full lubrication, a life span up to six times longer with Mancrodur was proven carbonitrided.

Double service life in operation

In difficult environments, such as those found primarily in railway technology, mining or the steel industry, tests under adverse real conditions are crucial. In a hot strip mill of a steel producer, the first test bearings of the four-row FAG tapered roller bearings made of Mancrodur are used in the work rolls. The test bearings achieve a double service life in this application.

Mancrodur is particularly suitable when higher machine availability is to be achieved despite rough operating conditions. In addition to already proven applications in steel mills, heavily loaded axlebox bearings in freight wagons, planetary bearings in wind power transmissions and bearings in pumps and compressors are further preferred fields of application for the new high-performance steel. The trend towards downsizing in many machines means that the bearing capacity is limited. With the significantly higher load capacity, the insensitivity to insufficient lubrication and contamination, Mancrodur can also be used especially for bearings in gearboxes of agricultural machines, construction machinery, cars and trucks as well as in ship drives. (ud)

Hannover Messe 2017: Hall 22, Stand A12