Product Description
The turntable bearings are surface hardened by continuous medium frequency induction heating and water spray cooling along the circumferential direction of the tread. The depth of the effective hardened layer is generally 3 ~ 5 mm, and a longitudinal soft belt is left at the beginning and end of heating. With the rapid development of modern industry, higher requirements are put forward for the quality of turntable bearings and their materials. According to JB/T 4149-2010 Technical Conditions for Arm Bearings, the depth of hardened layer measured to 260HBW should reach 15mm. Such hardened layer depth can only be achieved by heating water (oil) at the same time with power frequency, and the surface hardened layer area and transition area have good stress distribution, which will help to improve the contact fatigue resistance and prolong the working life. Although the wheels of single-edged cranes with similar shapes can reach this hardened layer depth by means of sectional reciprocating heating with power frequency quenching machine, there are certain differences in process parameters due to the different shapes of the two bearings, and further process tests and research work are needed to realize the deep surface quenching of the bearings.
In this paper, the wheel of arm-type turntable bearing is studied, and the forging wheel with commonly used dimension φ 630mm (tread) and made of 35CrMnSi steel is selected, and the oil immersion quenching process is tested by three-stage reciprocating heating.
2.1 technical requirements.
The structure of the bearing is shown in Figure 2, which is made of 35CrMnSi steel. The quenching hardness of the tread and the inner surface of the rim is required to be 300 ~ 380 HBW, and the hardness from the end face of the bearing to the depth of the hardened layer 15mm is ≥260HBW.
Selection of rolling bodies.
Generally, the specifications of the selected rolling body are determined according to the clearance between the power frequency inductor and the parts, and the inner diameter of the coil is generally+40 ~ 100 mm of the workpiece diameter. According to the diameter of the bearing, the φ720mm special single-phase turntable bearing is selected, and the bearing accuracy is P5 level, as shown in Figure 3.
Operation control
Power frequency induction hardening of bearings is carried out on a special machine for power frequency induction hardening of bearings. During quenching, the loading cylinder drives the chuck to push the bearing into quenching for heating; the variable frequency motor drives the main shaft, tray and bearing to rotate around the longitudinal axis; during heating, the wheels are moved up and down according to the heating conditions, so that all parts of the bearing are heated more evenly; After heating, the workpiece is lifted by bridge crane and precooled in the air, and then the whole quenching operation is carried out. In the whole operation process, the time taken for lifting the bearing forging to oil cooling after heating to a warm temperature is important, because the bearing is in the air away from the heating environment, and the temperature drops very quickly. If the temperature of the workpiece drops too much and is lower than the quenching temperature, the quenching hardness of the wheel will be reduced. During cooling, the bearings should swing constantly to make the cooling more uniform. Operators should be familiar with equipment operation, and cooperate with bridge crane operators to prepare for bearing power frequency induction quenching.
Audited Supplier 
){kind=link}