The technological process of the automobile hub bearing unit and the selection of processing tools

The automobile industry is a pillar industry in our country and occupies a pivotal position in the national economy. Especially with the breakthrough of new energy vehicles and unmanned driving technology, the automobile industry will be one of the focuses of technological competition between countries in the future. Therefore, with the strong support of the country, my country's automobile industry has made great progress and development, and front-wheel drive vehicles have been widely popularized. As an important part of the automobile industry - hub bearing unit, it has also made remarkable achievements with the development of the automobile industry.

As a very important part of the car, wheel bearings play a vital role in the safety of the car. How to improve the service life of wheel bearings is a difficult problem for every car person, and it is also the goal and motivation that every car person strives for. However, the service life of the hub bearing is a comprehensive evaluation index for evaluating the hub bearing. Bearing design and processing technology, material, sealing device, use method, and service conditions all have varying degrees of influence on bearing life and performance. Among them, the choice of processing technology is the one that has a greater impact on the life of hub bearings. To improve the processing technology of bearings, we can start from the following aspects:

First, improve the hub bearing forging technology. The outer ring of the ring blank of the wheel hub bearing has the characteristics of thin wall thickness, large width, and large difference in the size of the inner ring. The structure is complex and asymmetric, and the shapes are diverse. Therefore, it is more difficult to forge the ferrule blank. Therefore, a new forging process is required, and the advanced forging process of developed countries in Europe and the United States can also be used for reference, that is, the hot forging production of the bearing ring blank is carried out by using a multi-station high-speed upsetting press, and the medium-frequency induction furnace heating and tower forging process are used.

Second, wheel bearing cryogenic treatment technology. The use of new types of bearing steel with better performance will greatly improve the life and performance of hub bearings, but the improvement of steel quality requires long-term research and a large amount of investment, which is a long-term and slow development process.

Third, the machining technology of hub bearings. The hub bearing unit of the automobile has developed into a special hub bearing, which consists of an outer ring with double grooves, two inner rings with single grooves, two rows of steel balls, a pair of glass fiber nylon cages, and two sealing rings. constitute. Bearing hub processing has relatively high requirements in two aspects, one is the center distance of the second groove of the outer ring, and the other is the axial oil clearance of the bearing of the axial unit. This makes processing and assembly extremely difficult. Therefore, in the finishing stage of the outer ring, the corresponding round forming turning tool should be used to finish the machining surface. Since the machining surface is turned at the same time under one installation, the accuracy of the groove distance depends entirely on the accuracy of the forming turning tool. up. Therefore, in the processing of large-scale and high-precision bearings, it is the processing trend of the bearing industry to adopt hard turning (replacing grinding with turning) technology, and this process has high processing efficiency and low cost, and traditional processes cannot compete with it.

In the actual production and processing process, hardened steel is generally used for hub bearing units, because hardened steel has the characteristics of high hardness, high strength, and almost no plasticity. Therefore, it is often used to make bearings, gears, and high-hardness parts. On the contrary, it is precisely because of these characteristics of hardened steel for processing hub bearings that the difficulty factor of processing is higher than that of ordinary steel. This puts forward more stringent requirements on the cutting tools for processing such materials. As the leader of professional hard material processing tools, Valin Superhard can provide customers with professional and efficient cutting solutions for automotive hub bearing units and precision cutting tools. This series of tools adopts hard turning technology to turn hub bearings, not only realizing A more stable cutting process ensures a higher finish and helps the bearing industry reduce the total production cost. Therefore, for the processing of automobile wheel bearings, we generally recommend PCBN cutting tools. This is because PCBN cutting tools not only have high hardness, but also have high chemical stability and good thermal conductivity. The heat is quickly transferred from the cutting point, which reduces the thermal deformation of the workpiece, improves the machining accuracy and cutting efficiency and the service life of the tool, and is an indispensable tool in machining.

However, since there are many kinds of PCBN product series on the market, which PCBN tool to choose is the most optimal processing solution?

In this regard, we recommend using PCBN inserts of Hualing BN-H10C25 grade to process wheel bearings. Moreover, according to the characteristics of the processed material, we apply a special coating treatment to the CBN polycrystalline composite blade, which can reduce the friction force during the contact process with the workpiece, thereby reducing the cutting force, reducing the frictional heat generation during cutting, and reducing the friction of the workpiece. Thermal stress deformation, compared with the uncoated CBN insert, the smooth coating of the coated CBN insert is perfectly combined with the CBN base material, which can obtain better cutting performance, reduce the wear of the meniscus, improve the machining accuracy and use life.

The specific tool solution is as follows: During the process of heating and then hard turning, the cutting parameters of the processing equipment should be adjusted during the process of turning the Valin BN-H10 C25 layer composite CBN blade to remove the workpiece allowance. The experiments show that during the processing, the processing parameters play a vital role in the processing quality, product surface finish and service life. The following are the processing parameters summarized by our company's scientific research personnel in the actual production process for reference.

That is, during the cutting process, the cutting speed is adjusted to 180m/min, the feed rate is 0.1mm/r, and the cutting depth is 0.15mm. This enables the hub bearing to achieve a surface finish of less than 0.6µ. Compared with traditional carbide tools, the production efficiency is doubled and a higher surface finish is obtained.

A lot of practice shows that our company's CBN inserts have greatly improved the production speed and tool life compared with traditional carbide tools, and are very effective processing tools in the processing of wheel hub bearings.

At present, my country is building the future industry 4.0 with high-end manufacturing represented by high-speed rail, manned spaceflight, new energy vehicles, and artificial intelligence, seizing the commanding heights of future industries, completing the overall surpassing of developed countries, and realizing the great rejuvenation of the Chinese nation. But these goals and plans are inseparable from the diligent pursuit of every participant, as well as the excellence of every component and every process. Only by striving for development and technological innovation can we truly achieve cornering overtaking and become a real manufacturing powerhouse. Although it is difficult to achieve such a goal, there is a long way to go, and we are willing to explore together.