Abstract The paper introduces several key processes of large-scale pivoting support and measures taken for the production with the result that the products can meet the requirements marked in the drawings.
Descriptors super huge bearing, processing , quench-hardening, deformation.
Large slewing bearing, also known as slewing bearing or extra large bearing, is a large bearing capable of withstanding comprehensive loads. It can withstand large radial loads, axial loads and tipping moments. Slewing bearings are widely used in hoisting and transporting machinery. , port machinery, ship machinery and other large-scale rotary devices.
Due to the large volume of the large slewing bearing, the small cross-sectional area of the part, the high machining precision, the long process, and the easy deformation, the difficulty of machining increases. We have adopted corresponding technical measures for the support rings and outer rings of the slewing bearings, and according to the design. It is required to be processed, assembled by commissioning and more than one year of use inspection, which fully meets the original design requirements, and some aspects are even higher than the original design requirements.
1. Selection of rough forging
The large-sized workpiece of the slewing bearing has a support ring, an outer ring and a fixing ring. Since the support ring and the fixed ring are thin-walled annular parts, if the blank of one piece needs to be large when forging, and the heat treatment is prevented, the amount of quenching and tempering needs to be increased. Since the dimensions of the inner and outer rings of the retaining ring and the supporting ring are relatively similar, after repeated analysis, it is relatively easy to forge a large forging, and the fixing ring and the supporting ring are forged into one body, so that one set of slewing bearings has two blank forgings, one for outer The ring, the other is a forging of the retaining ring and the support ring.
2. Rough machining
The key to roughing is whether to separate the retaining ring from the support ring. The roughing process is a process before quenching and tempering. If the retaining ring is separated from the support ring, the amount of the retaining ring should be increased, and the deformation during the heat treatment is easy to increase; if it is not separated, during the semi-finishing process, due to the high hardness of the quenching and tempering, the machining and the large ring cut open. It is more difficult. From the perspective of the overall manufacturing process, it is not separated, and then separated after being tempered.
First, the amount of deformation during the quenching and tempering process is reduced.
Second, it is beneficial to better heat treatment, thus ensuring the quality of the heat treatment process. Through this analysis, we decided not to separate the retaining ring from the support ring before heat treatment, thus making the overall The roughing allowance is correspondingly reduced.
3. Since the fixing ring and the supporting ring require the hardened layer to be 3 to 5 mm, the hardness after surface quenching reaches HRC 55 to 60. The diameter of the part is large, but the cross-sectional area is small. After the car is finished, the surface is quenched. If the deformation is too poor, it can only be scrapped and the loss is too great. If quenching first, the thickness of the hardened layer should be 3~5 mm. If the amount of space is smaller than the shape variable, it will cause waste.
If the amount is larger than the shape variable, it is difficult to process. The amount of deformation is 1. 5 mm, such a 2 mm retention, the amount of the hardened layer is 2 mm, and the thickness of the hardened layer is 5 to 7 mm. Sufficient, after the quenching and tempering process, after the hardness test is passed, we test the support ring and the fixed ring and the outer ring, and find that the deformation amount is up to 1 mm, the minimum is 0.70 mm, and the amount is not exceeded. If it is reworked, it can also be supported by multiple points. The quenching surface can be 1.5 mm. If there are more support points, the retention can be reduced to 1 mm.
In the turning process, since the hardness is basically HRC 59-60, we use the special alloy tool we developed and use the low-speed small feed for turning. When the amount is 0. 02 mm, it is ground with a bowl-shaped grinding wheel. When required for size, it is ground with a polishing belt to achieve the dimensional and roughness requirements of the drawings, laying the foundation for the manufacture of high quality slewing bearings.