The raceway of the slewing ring (turntable bearing) needs to be quenched. After quenching, the hardness of the raceway of the turntable bearing is increased and the wear resistance of the raceway is increased. However, improper quenching is prone to quenching cracks. Once cracks occur, they will be caused in most cases. The scrapping of slewing bearings has important meanings due to the prevention of quenching cracks. Prevention of quenching cracks can be grasped from the following aspects.
1. Choose a reasonable quenching method. According to the structure and characteristics of the slewing bearing, technical requirements, structural design, worker quality, etc., the correct and reasonable selection of the quenching method can greatly reduce or avoid quenching cracks.
2. Reasonably arrange the process line. Once the material, structure and technical conditions of the slewing ring are recognized, the process personnel shall conduct process analysis and recognize the reasonable process line. Correctly arrange the sequence of preparatory processing, heat treatment and thermal processing. This is the main effective way to prevent the cracking tendency of the slewing bearing track after heat treatment.
3. Appropriate recognition of the heating parameters. In the heat treatment of the slewing bearing track, improper heating is the main factor that causes the cracking of the quenched slewing bearing raceway. Therefore, the heating parameters such as heating medium, heating speed, heating temperature and heat preservation time should be correctly selected and designed.
4. Other methods to prevent quenching cracks Tempering in time after quenching (low temperature tempering is generally used), and the thin-wall treatment of parts with complex shapes can also effectively prevent cracks from occurring.
5. Selection of quenching medium The selection of quenching medium should be summarized and considered the following elements:
(1) Slewing bearing characteristics: the chemical composition of the steel (phase change characteristics), the cross-sectional dimensions, geometry, surface roughness and surface condition of the workpiece, the placement and density of the raceway during quenching, etc.
(2) Quenching method: including quenching bath liquid, stirring speed, flow direction, and solution concentration.
6. Proper product design should be based on the working conditions and use requirements of the slewing bearing, the cross-sectional dimension of the slewing bearing should be reasonably designed, the correct material should be selected, and the structural design should try to meet the heat treatment process for the structure of the slewing bearing.
