High Quality Slewing Bearings

1.Advantages of four-point contact ball slewing bearings

Advantages and applicable working conditions of four-point contact ball slewing bearing The four-point contact ball bearing is a single-row angular contact ball bearing, and its raceway is designed to withstand bidirectional axial loads. The contact angle can be 30 degrees, 35 degrees, and 45 degrees.

The inner ring can be divided into two pieces, which can hold a large number of balls, so it has a large bearing capacity. The bearing is separable, that is, the two pieces of the inner ring and the outer ring with the ball and cage assembly can be installed separately.

Four-point contact ball slew bearing has a compact structure and light weight. The steel ball contacts the arc raceway at four points, which can bear axial force, radial force and overturning moment at the same time, and has strong dynamic load capacity.
Applicable working conditions: The load is generally below 100T, and you can choose single-row four-point contact ball bearings, double-row ball contact ball bearings, and ball-ball combination bearings.

The overall cage and segmented cage can be used to improve stability and service life, and the rotation speed can be appropriately increased to 30rpm-120rpm. The accuracy level is best controlled.

At present, the common four-point contact balls include excavator bearings, truck crane bearings, crane bearings, crawler crane bearings, turret bearings, CT machine bearings, bottle blowing machine bearings, filling machine bearings, turntable bearings, and crane bearings. etc.

2.Advantages and features of four-point ball crossed roller three-row roller bearings

The internal structure of the slew ring is basically a four-point ball crossed roller three-row roller bearing. The advantages and characteristics are summarized as follows:

1. Four-point contact ball bearing, flexible, anti-permanent fatigue, highest speed, selection design below 50T

2. Cross roller structure, resistant to permanent deformation, good rigidity. 1797/3230, 1797/2500, and 1797/2635 are typical rough-skinned designs, bulky designs, and high reliability. Among them, cross-tapered roller bearings are the first choice for high-precision bearings for measurement, control, and positioning.

3. Double-row ball bearings, flexible to take into account the load below 100T, such as crane bearings, car crane bearings.

Double row crossed roller bearings, in the same way, taking into account rigidity and load-bearing

3. Three-row roller bearings, a typical example of low-speed, heavy-load, high-precision bearings, are always unfavorable. Mature design and highest reliability. The field of low-speed heavy-duty bearings almost occupies the top edge. Preferred structure above 200 tons.

3.Material selection of slewing bearing

The material of the slewing ring bearing, 45# was selected in the early stage, and it was gradually eliminated due to the poor quenching and tempering performance.

This article focuses on the influence of the materials 42CrMo, 40Cr, 50Mn and GCr15 on the process and quality of the slewing bearing.
As a high carbon steel, 42CrMo has excellent quenching and tempering properties and quenching properties, and is the first choice for slewing bearings.
50Mn has good hardenability and is also a good choice for slewing bearings.
40Cr is also good in terms of mechanical properties, and it is still in the stage of exploration and practice.

GCr15 small slewing bearing can be selected, but milling and drilling in the process are troublesome due to full quenching, so it is generally not recommended.

4.Slewing bearing application

The slewing bearing and the slewing bearing are similar in form, but there are qualitative differences. In short, the slewing bearing is just a mechanism that can rotate in a purely mechanical way.

The slewing bearing needs to realize various loads, precision and measurement and control, as well as realize the driving rotation of various actions.
Features in the field of use of slewing bearings:
◎Port cranes usually use three-row roller slewing bearings with internal teeth or external teeth with a diameter of 4 meters to withstand high overturning moments.
◎Stacker and reclaimer: The turntable bearings used in the stacker and reclaimer are usually ball-column combination type, three-row roller type and cross-roller type, and most of them have a diameter of over 3 meters.

Due to the harsh working environment and large dust, this type of bearing has the characteristics of high bearing capacity, long life and good sealing performance.
◎Ferris wheel: used for the four-point contact ball turntable bearing on the Ferris wheel, the outer diameter is 5000mm larger, and the thickness is 200mm
◎Ship unloader: The slewing bearing for ship unloader usually adopts the structure of three rows of rollers with external teeth, with a diameter of about 4 meters.
◎Tower crane: The slewing bearing for tower crane usually adopts small-sized four-point contact ball slewing bearing or double-row ball slewing, and the diameter does not exceed 2 meters.
◎Radar antenna: The short-wave antenna generally uses a three-row roller structure slewing bearing, and the rotation speed is slow.
◎Shield machine: The diameter of the slewing bearing for shield machine ranges from 2.5 meters to 6 meters, and some have larger diameters. These bearings work under very harsh conditions, with large bearing load, strong corrosion resistance and short life. .
◎Ladle turntable: The slewing bearing for the ladle turntable usually adopts a three-row roller structure. Due to the harsh conditions with dust and high temperature, it has high requirements on the retainer, grease and sealing strip.