Firstly, understand the material of the blank and the conditions after forging before processing. Secondly, check whether the blank has defects such as lamination and cracks. Measure the outline size of the blank shape, including the inner and outer diameters of the blank, the height dimension, and the calculation of the machining allowance. It can accurately estimate the number of cutting tools for turning. The blank of the slewing bearing can be classified into two sorts: normalizing treatment and quenching and tempering treatment. The cost of normalizing treatment is relatively low, for the hardness is low, and the torque carried by the gear is relatively small.
1. Turning processing
(1) Rough turning
Rough turning is carried out according to the turning process drawings. The cutting speed and cutting amount are strictly implemented in accordance with the process regulations.
(2) Rough turning aging
After the rough turning of the bearing parts is completed, use three-point support and lay flat (stacking is not allowed, and the aging time is not less than 48 hours before finishing processing.)
(3) Fine turning
When finishing turning bearing parts, the cutting speed is 6 to 8 revolutions per minute, and the cutting amount is 0.3 to 0.5 mm.
(4) Forming finishing turning
When the bearing parts are finally formed into finishing turning, in order to prevent the parts from deforming, the fixed clamping device of the parts must be loosened to make the parts in a state of no force. The turning speed is 8 revolutions per minute and the cutting amount is 0.2 mm.
(5) Special process for the inner ring of crossed and three-row roller slewing bearings which can prevent the inner ring of crossed and three-row roller slewing bearings from deforming after heat treatment. Turning must be processed in pairs, that is, raceway back-to-back processing, without cutting before heat treatment, and cutting after heat treatment.
(6) Finish turning after heat
After the heat treatment of the inner and outer rings of the bearing, perform the finishing process.
2. Heat treatment
(1) Raceway surface quenching: the surface of the bearing raceway is quenched by medium frequency, to make sure that the hardness is not less than 55HRC, the depth of the hardened layer is not less than 4 mm, the width of the soft belt is less than 50 mm, and the corresponding place is marked with "S".
(2) After heat tempering treatment: the bearing inner and outer rings need to be quenched at 200 degrees for 48 hours before being out of the furnace. In order to ensure the disappearance of internal stress and prevent subsequent cracks from occurring. After each batch of slewing bearing is heat treated and tempered by slewing bearings manufacturers, magnetic particle inspection is required to prevent cracks from occurring.
3. Gear making
(1) Some slewing bearings used in severe working conditions require surface quenching treatment, such as excavators, pile drivers, wood grapples, graders and other working conditions, which have relatively large impact loads and need to be quenched on the tooth surface, according to the modulus size. The hardness after quenching is between 45-60HRC. For common working conditions such as cranes and tower cranes, the tooth surface does not need to be heat treated.
(2) With the rapid development of Industry 4.0, slewing bearings are more and more widely used in the automation industry. In this application field, the precision requirements for the teeth are relatively high, and the minimum requirement is also 8-level accuracy. In response to the rapid changes in the market, during the construction of the new plant, higher precision requirements are required for the equipment to meet market demand.
4. After the gear-making process is completed, there are follow-up processes such as fine turning, plane, drilling, track grinding, and assembly, and the slewing bearing can be delivered.