Basic knowledge and application of slewing bearing

    Slewing bearing，be also known as slewing ring bearing or  turntable bearing。It is a kind of large bearing that can bear comprehensive load, and can bear large axial load, radial load and overturning torque at the same time.The slewing support bearing generally has the installment hole, the inner gear or the outer gear, the lubricating oil hole and the seal device, thus can make the host machine design structure compact, the guidance is simple, the maintenance is easy。Slewing bearing，be also known as slewing ring bearing or  turntable bearing。It is a kind of large bearing that can bear comprehensive load, and can bear large axial load, radial load and overturning torque at the same time.The slewing support bearing generally has the installment hole, the inner gear or the outer gear, the lubricating oil hole and the seal device, thus can make the host machine design structure compact, the guidance is simple, the maintenance is easy。

一、Structural classification and characteristics

There are four main structures of slewing bearing: single row four-point contact ball slewing bearing, double row angular contact ball slewing  bearing, single row cross roller slewing  bearing, three row combined roller slewing bearing, which are respectively divided into three types of toothless type, external type and internal type.The characteristics of each structure are as follows:.

1、single row four-point contact ball slewing bearing：

It consists of two seat rings.Compact structure, light weight, four point contact between steel ball and arc raceway, can bear axial force, radial force and tipping moment at the same time.Rotary conveyors, welding operators, small and medium-sized cranes and excavators and other construction machinery can be selected；

2、double row angular contact ball slewing  bearing

It has three seat rings, steel ball and isolation block can be directly into the upper and lower raceway, according to the state of the force, the arrangement of the upper and lower two rows of steel balls with different diameters.This kind of open assembly is very convenient, and can withstand a lot of axial force and tipping torque.Due to its large axial and radial dimensions and strong structure, it is especially suitable for tower cranes and truck cranes with medium or above diameters.

3、single row cross roller slewing  bearing,

It has compact structure, light weight, high manufacturing accuracy, small assembly clearance, high requirements for installation accuracy, roller 1:1 cross arrangement, can withstand the axial force, large radial force and tipping torque.Widely used in lifting and transportation, construction machinery and military products.

4、three row combined roller slewing bearing

It has three seat rings up and down and radial raceway separate, so that each row of roller load can be accurately determined, can bear all kinds of load at the same time, is the largest bearing capacity of all products of rotary bearing.The shaft and radial dimensions are larger and the structure is firm, especially suitable for heavy machinery requiring larger diameter, such as bucket wheel excavator, wheel crane, Marine crane, ladle slewing and large tonnage truck crane, etc.

二、 Bearing materials

   Ring and rollers: generally, the rotary bearing rollers is made of carbon chromium bearing steel hardened as a whole.GCr15 or GCr15SiMn;Rotary support ring is surface hardened steel, when the user has no special requirements, generally choose 50Mn steel manufacturing, but sometimes in order to meet the needs of some special applications of the host, but also according to the specific conditions of use provided by the user to choose other brands of surface hardened steel, such as 42CrMo (42CrMo4V), 5CrMnMo.

Cage materials: the cage used for slewing support has integral type, sectional type, isolation block type and other structural forms.The integral and sectional cage is made of 20 # steel or ZL102 cast aluminum alloy.Isolation     block type is made of polyamide 1010 resin, ZL102 casting aluminum alloy, etc.In recent years, nylon 1010 has also begun to be used in sectional retainers

   Sealing ring material: rotary bearing sealing ring material with oil resistant butadiene eye rubber manufacturing.

三、Application:

   slewing bearings are widely used in large slewing devices of hoisting machinery, mining machinery, construction machinery, port machinery, ship machinery and other equipment, and some are also used in radar antenna pedestal, robot, tunnel boring machine of excavator and other aspects.Especially in the mechanical aspect, the most widely used, including: truck crane, railway crane, port crane, Marine crane (including:  floating crane, Marine crane, Marine deck crane, Marine electric slewing crane）metallurgical cranes, container cranes, etc.