A journey weighing several tons: From the blank to the large-diameter slewing bearing
It's a long way from a solid piece of steel to a fully functional slewing bearing. Because the production journey begins with a cylindrical steel strand and finally ends at thyssenkrupp rothe erde as a ready-to-use centerpiece of various applications.
1. The first steps: from the warehouse to the saw
The journey of the gigantic steel rings begins in the ring rolling mills of thyssenkrupp rothe erde. But at the beginning, nothing can be seen of their later diameter. At this stage the cylindrical steel strands have diameters of only 180 mm to 1500 mm and weigh on average around 21 tons. Transport to the sawing equipment is therefore carried out with the aid of a high-voltage magnet.
2. From the cylinder to the "glowing donut".
In the cutting shop, a high-performance saw cuts through the steel strand. The size of the cut steel cylinder depends on the geometry that the slewing bearing is to have at the end and can therefore vary, depending on the order. In order for the steel cylinder to be modeled into a ring after sawing, it must first be heated. In special furnaces, the steel cylinder is heated up to 1,200 degrees.
To turn the red-hot steel cylinder first into a disk and then into a ring, it is upset with a powerful press. 6,000 tons of press force deform the steel into a disk. A punch is then used to produce a ring from the disk - a steel donut. To prevent the tool from sticking to the steel, a graphite layer is applied. The temperature next to the equipment is around 70 degrees Celsius.
3. Rolling and heat treatment
The completion of the initially rather donut-shaped steel ring takes place in a CNC-controlled and -monitored rolling process. This is followed by a defined heat treatment in which the ring is given its mechanical technological properties. These are checked in various destructive and non-destructive testing procedures.
4. The ring is machined and the slewing bearing is mounted
At thyssenkrupp rothe erde, the rings are given their contours, such as raceway, bores and, if necessary, splines, by various machining production steps. These contours are required for the functions, such as the rotary motion and the connection to the adjacent construction. To increase the service life and wear resistance of the bearings, the raceways and wear surfaces are hardened. This is done by our inductive hardening process.
Depending on the design and required tolerances, the subsequent finishing of the slewing bearing is either by hard turning or grinding. A combination of the two processes is also possible. After finishing, the rings are mounted.
5. The big moment: everything must fit
Nothing works anymore: Now the moment of decision has come. Whether all production steps mesh well with each other is determined when the outer ring and inner ring, or upper and lower ring, are brought together and function together as a large-diameter antifriction bearing, handling the rotary motion without any problems. In the final inspection, both internal and external specialists check the manufacture of the rothe erde® large-diameter antifriction bearing: final dimensional checks are carried out and the forces required for the rotary motion of the bearing are calibrated.
Construction projects of large plants depend on the success of slewing bearing manufacturing. Faulty production would not only mean a loss of time, but also high costs - not least due to the standstill of plant construction if, for example, a wind turbine cannot be built further because the delivery of a large-diameter antifriction bearing is delayed. That's why our experts at thyssenkrupp rothe erde focus on quality and precision work based on over a century of experience as well as the latest technological know-how.