Processing technology of super large split three-row cylindrical roller slewing bearing

Introduction The split three-row cylindrical roller slewing bearing has many segments, large size, high quality, low assembly precision during processing, large quenching deformation of the whole circle, large stress at the joint, and it is difficult to adjust the radial and circumferential gaps. There are many times of grinding the raceway, and the blade of traditional high-speed steel material is easy to wear. Improvement measures are proposed: adding special molds during processing and splicing; adopting segmented and faceted quenching, and adding a shaping process after quenching; designing a radial positioning fixture to adjust the radial clearance, and designing a tangential positioning fixture to adjust the circumferential direction clearance; The inner and outer ring axial raceway dimensions required to be machined are calculated by the clearance calculation; the coated carbide tool is used for soft turning, and the cubic boron nitride (CBN) tool is used for hard turning to complete grinding instead of turning. The finalized process route meets the technical requirements required for bearing machining. With the maturity of offshore equipment technology, large cranes in the offshore industry have developed to super large size and super tonnage. The slewing bearing structure of this diameter section is mostly split type, which has the advantages of being convenient for transportation, storage and disassembly, and the disadvantage is that it needs to be split and spliced ​​many times, the processing technology is complex, and the processing accuracy is difficult to guarantee, so it is necessary to determine the appropriate processing technology . 1. Super-large split three-row cylindrical roller slewing bearing structure The structure of a split three-row cylindrical roller slewing bearing structure is shown in Figure 1, which adopts the method of stepped lap joint and axially positioned connection with hinged bolts (Figure 2). Combined into a whole inner and outer ring, after assembly, the inner ring of the bearing expands along the inner diameter direction as shown in Figure 3. The maximum outer diameter of the split bearing is 12.3776 m. The height is 0.6 m, the maximum wall thickness is 489 mm, and the inner and outer rings are divided into 18 sections. Technical requirements: The assembly height is (600±2) mm, the axial clearance is 1.2 ~ 1.8 mm, the radial clearance is 0.5 ~ 1.2 mm, the axial runout is not more than 0.6 mm, and the radial runout is not more than 2 mm. 2. Processing difficulties 1) The bearing diameter exceeds the processing range of the machine tool table. 2) Splitting the notch on the thrust raceway will form a certain angle with the element line of the roller, so that the roller can pass through the notch. In order to ensure that the gear strength is less affected, the outer gear ring splitting cut is cut at the center of the tooth groove bottom, which increases the difficulty of milling the connecting surface and splicing a complete circle. 3) The diameter of the split bearing is large, the split section is inclined due to its own weight during the processing, the flatness and inclination of the two end faces and the axial raceway are large, the roundness and cylindricity of the radial raceway exceed the technological requirements, and the bearing rotates after assembly The accuracy cannot meet the requirements. 4) The total length of the quenching surface of the outer ring gear is 490 mm, which is a large-section raceway quenching. When the whole circle is quenched, irregular deformation will occur in the sections (Fig. 4). After deformation, it cannot be spliced ​​into a full circle, which affects the subsequent processing. After the whole circle is quenched, the stress at the seam is large, and the ferrule will be disengaged from the seam. The size of the whole circle is large, and the rotation of the quenching machine tool is difficult. 3. Plan formulation 3.1 The split bearing of the tooling fixture is processed on the tire tool. In order to facilitate lifting, the tire tool also adopts a split structure. The whole tire is divided into 4 sections, the connection method is upper and lower lap joints, the axial direction is positioned with tapered pins, and double rows of screws are added for fastening (Figure 5). The material of the tire tool is ZG380-510 cast steel with high yield strength and tensile strength, which ensures the rigidity of the tire tool. The tire tool provides a reliable rigid support for the processing of the split bearing, which can reduce the processing deformation of each process and ensure the processing accuracy. In order to expand the processing range of the machine tool, the special square box, support and supporting T-shaped block, screw rod, baffle plate, pressure plate, spacer block, etc. were remade, which solved the problem of over-range processing of large-diameter bearings. 3.2 Clamping method When processing, the clamping method of the tire and the split bearing should be considered. Take the processing of the main thrust raceway of the inner ring as an example. The inner ring clamping is shown in Figure 6. The bottom of the square box is designed with 2 rows of connecting holes, which are connected to the machine table through bolts. The claws clamp the tire and fix it with a pressure plate. The inner ring is placed on the tire, the long baffle is pressed against the outer diameter surface, and the pressure plate is pressed against the end face of the inner ring. The tire and inner ring are positioned axially and radially, and the number of fixed points is 3 times the number of bearing segments to prevent translation during parts processing. 3.3 The split surface of the splicing whole circle is in the shape of a step, and the axial clearance of the splicing is required to be no greater than 0.1 mm, and the radial clearance is no greater than 0.3 mm. Splicing will affect the machining accuracy of the bearing, so it is necessary to ensure that the splitting cut of the outer ring gear is at the center of the groove bottom. In terms of technology, the finished tooth shape and the subdivision line of the fine milling connection surface are first drawn (Figure 7), and the axial and circumferential fitting surfaces are processed on the CNC gantry milling machine. Through program setting and pre-simulation, the arc length of each segment and the angle and size of the two joint surfaces are adjusted, and the joint surfaces are developed several times to ensure the connection accuracy. The split bearing needs to be hoisted, spliced ​​and disassembled many times during processing. In order to ensure the connection accuracy of the finished product, a small-sized process taper hole is used in the previous process. Use taper pins to locate the connection points of each segment and then connect and process. In the final processing, the positioning taper pin holes are processed into reamed bolt holes to ensure reliable connection of parts. 3.4 The quenching scheme selects segmented and faceted quenching. For the convenience of hoisting, the hoisting holes are processed before quenching