world of industries 3/2017 (EN)

MACHINE ELEMENTS
ence from pilot projects that really count. The field experience so
far with carbonitrided Mancrodur is very promising.
Higher operating life in steel industry
One of the largest hot strip mills of Thyssenkrupp Steel Europe
(TKSE) is located at its Bochum site. The hot strip mill is specially
designed for milling high-tensile quality steels. The rolling bearings
need to be able to withstand 45 million Newtons at high temperatures
and with a large amount of contamination. After downtimes
occurred because of the premature failure of conventional bearings,
TKSE installed four-row FAG tapered roller bearings made of carbonitrided
Mancrodur. The international steel producer has confirmed
that these bearings have a significantly longer operating life.
01 Grinding patterns from case-hardened steels
(left) and carbonitrided Mancrodur (right)
Higher load-carrying capacity in wind turbine
gearboxes
This is how Bernhard Köhler, Business Development Manager in
the Regional Wind Business Unit at Schaeffler, describes the current
situation in the development of wind turbine gearboxes: “Since
design lifetimes of at least 20 years apply in the wind energy industry
– corresponding to 175,000 hours – and the bearing positions
more and more frequently max out the planetary bearings’ load
ratings, the industry is in desperate need of bearing solutions
that will provide longer bearing life even under extreme lubrication
conditions.” With a load-carrying capacity that is 30% greater
and an operating life that has now been all but proven on the test
stand to be at least twice as long, the wind energy industry can once
again tap into margins of higher power density and longer runtimes
by using carbonitrided Mancrodur. “For instance, downsizing
planetary wheel bearings makes it possible to increase the wall
thickness of the planetary wheels or the ring gear within the same
installation space, which is precisely where the limits of feasibility
are often reached. Besides the lower mechanical load of the gear
rings, the greater wall thickness also reduces their elastic deformation,
improving meshing considerably,” explains the specialist.
02 Comparison of the effect of mixed friction on the operating life
of bearings made of standard bearing material with that of bearings
made of carbonitrided Mancrodur
Handling overloading in freight transport
“Occasionally, operators will look for various non-standard ways to increase
the productivity of their machines and facilities. In rail freight
transport, for example, this might be done by regularly overloading the
freight cars with over 10% more payload than specified by the design,”
stresses Schaeffler Senior Manager Matthias Kilian. He goes on to say,
“The overloaded bearings, such as inch-based AAR class K bearings
(AAR = Association of American Railroads) with about a 157 mm bore
therefore need to be replaced early and often unexpectedly. The premature
material fatigue is usually the result of the mechanical overload
combined with mixed friction and excessively long maintenance intervals
for these load conditions.”
By exchanging the axlebox bearings with structurally identical bearings
made of carbonitrided Mancrodur, the operator can still have
the increased payloads while returning to reasonable maintenance
intervals, and it will no longer be necessary to purchase new bearings
as frequently. However, the greatest economic benefit for the operator
comes from the fact that the cars’ existing bogies can still be used.
“Otherwise, the operator would have to resort to the next larger bearing
series, such as AAR class G bearings with a bore that is around 20 mm
larger, which would naturally make larger wheelsets, wheelset shafts,
and other bogie components necessary,” Matthias Kilian explains.
Photographs: Schaeffler
www.schaeffler.com
03 Benefits of Mancrodur depending on application area
About Schaeffler AG
Schaeffler Group is a leading integrated auto motive
and industrial supplier. The company based in Herzogenaurach,
Germany, generated revenues of approximately
13.3 billion Euros in 2016. With around 86,600
employees, Schaeffler is one of the world’s largest
family owned companies. The group has approximately
170 operating locations in more than 50 countries
with a worldwide network of manufacturing plants,
research and development centers, and sales subsidiaries.
Schaeffler makes key contributions towards
‘mobility for tomorrow’ with precision components
and systems in engines, transmission and chassis
applications as well as rolling and plain bearing solutions
for industrial applications.
WORLD OF INDUSTRIES 21