Application technology development history of oil film bearing in rolling mill industry

Jul 20, 2023

With the development of steel rolling technology, rolling mill bearings are also improving. On the basis of independence, independent research and development, and self-reliance, the technology of oil film bearings for rolling mills in China has also developed rapidly. The development of oil film bearings requires a comprehensive review and study of China's oil film bearing technology, as well as foreign advanced technology, which is beneficial to the understanding, promotion and development of China's rolling mill oil film bearing technology. Rolling mill oil film bearing technology is a system engineering technology, and at the same time, it is also a comprehensive engineering technology in a multidisciplinary field. It requires manufacturers to have corresponding supporting capabilities, which reflects the development speed and level of China's industry from the side.

The operation technology of oil film bearings includes a complete set of knowledge and skills such as storage, cleaning, installation, commissioning, operation, maintenance, diagnosis and management of oil film bearing parts in rolling mills. The technology of correct operation of rolling mill oil film bearings is a reliable guarantee for the safe operation of bearings. In the early 1950s, only the reversible rolling mill of Anshan Iron and Steel Cold Rolling Plant was equipped with oil film bearings in my country. Its operation and management are carried out in full accordance with the relevant regulations of the Soviet Union. The traditional process is adopted, the rolling pressure is not large, the rolling speed is low, the lubrication system is also very simple, and the operating technology level is relatively low. In actual operation, relevant management, technical personnel and operators in our country are very serious about their work, strictly follow the regulations, and have accumulated some experience in use and maintenance. However, due to the lack of in-depth understanding of the working principle of bearings, we are still relatively backward in many aspects, and this backwardness has continued for some years. For example, after the bearing components are installed, a pressure test of 35N/cm2 should be done. If there is oil leakage, the rotary seal should be tightened until there is no leakage. However, after such a pressure test adjustment, the effect of use is not good, and the life of the seal is also short. This kind of seal is a "J" type seal with a skeleton, which is sealed by the lip. After the pressure test is tightened, it is no longer a lip seal, but a band seal that clings to the rotating surface. Although the technology is backward, China's oil film bearings have started and accumulated experience.

From the 1960s to the early 1970s, my country's self-equipped rolling mill oil film bearings were put into operation. The φ1300mm roll oil film bearings and φ300mm rack roll oil film bearings of Wuyang Iron and Steel Company's 4200mm extra-thick plate rolling mill and the φ1700mm hot rolling mill back-up roll φ1100mm oil film bearings of Benxi Iron and Steel Company A batch of new bearings represented by the company are put into operation, the former is a single-stand rolling mill, and the latter is a multi-stand continuous rolling mill. These multi-stand rolling mill oil film bearings have been put into operation, which has popularized and improved the operation technology of rolling mill oil film bearings in my country. In terms of management, we have a professional technical team formed by professional technicians. And a dedicated workplace, the oil film bearing workshop implements closed management, the oil film bearing maintenance personnel and lubrication personnel have clear job responsibilities and operating procedures, the division of labor is becoming more and more refined, and the management is becoming more scientific and standardized.

Due to the improvement of the bearing structure and the renewal of the lubrication system, great progress has been made in the installation and commissioning of the bearing and the maintenance operation of the lubrication system compared with the beginning. In addition, the successful use of oil film bearings in continuous rolling mills has brought the operating technology to the modern level. One step closer. Subsequently, my country successively introduced complete sets of 1700mm hot and cold plate continuous rolling mills from Wuhan Iron and Steel Company and 2050mm and 2030mm hot and cold plate continuous rolling mills from Shanghai Baoshan Iron and Steel General Works, and also introduced MORGOIL bearings and MESTA bearings in sets. Personnel, including technicians and skilled workers, have undergone on-the-job training, and after the equipment is put into production, the continuous and safe operation of the bearings has been ensured. This indicates that the operation technology of oil film bearings in rolling mills in my country is close to the world level at that time.

Since the 1990s, rolling mills and rolling mill oil film bearings have been introduced in sets—mainly MORGOIL bearings, and more oil film bearings have been brought in when buying second-hand rolling equipment. The main type is also MORGOIL bearings. In this way, some major types of rolling mills, such as wire rod mills, single-stand reversing mills, semi-continuous rolling mills, continuous rolling mills, and profile rolling mills, are equipped with oil film bearings; in terms of bearing types, there are Soviet-type liquid friction bearings, Chinese TZ Brand oil film bearings, American MESTA oil film bearings and MORGOIL oil film bearings can be regarded as the country with the most complete varieties of rolling mill oil film bearings (including lubrication systems) in the world today. According to incomplete statistics, there are currently more than 20 iron and steel factories in my country, and nearly 200 rolling mills are equipped with oil film bearings, the number is quite huge. This is enough to show that the rolling mill oil film bearing operation technology has been widely popularized in China and has reached a new level in the world today.

The manufacturing technology of oil film bearings. The development of oil film bearings for rolling mills in my country began in the late 1950s. At the beginning, there were no drawings, no technical information, and no equipment. Under such circumstances, it is not easy to develop oil film bearings for rolling mills. There is a complete set of work procedures from material selection, process route, processing methods to special tooling design and manufacture. In terms of material selection, it is necessary to consider the pairing of the taper sleeve and the anti-friction material, the forging process performance of the sleeve, the combination of the bushing steel sleeve and the anti-friction material, and the process of the steel sleeve; from the process route, it is necessary to meet the requirements of the taper sleeve. , the technical requirements of the bushing, and at the same time use the existing processing equipment, which itself requires a good combination of theory and practice, for example, how to carry out physical and chemical treatment on the inner surface of the steel bushing to increase the bonding force; In general, we know that the taper bushing and bushing have the highest machining precision, the surface roughness of the taper bushing is Ra0.05μm (the bushing is Ra0.2μm), the geometric precision is high, the deformation is difficult to control, the surface roughness is low, and ultra-thin machining must be carried out. For finishing machining, polygonal columns, spirals, vibration lines, etc. are not allowed on the surface; the design and manufacture of special tooling is also very important, which is the key to realizing the processing method and ensuring the processing accuracy. In the early 1960s, the manufacture of the main parts of oil film bearings developed on ordinary machine tools was completed. At the end of the 1960s, a new period of manufacturing oil film bearings for rolling mills in my country began.

The test technology of oil film bearing includes two parts: one is the measurement technology of parts processing, and the other is the measurement technology in experimental research. Due to the high machining accuracy of the main parts of the oil film bearing, accurate and fast measurement is required. In order to meet this requirement, first of all, there must be high-precision measuring instruments and supporting auxiliary instruments. At the same time, for the measurement during processing and the quality inspection after processing, scientific measurement methods and skilled technology must be implemented. For this reason, in addition to purchasing and customizing high-precision measuring instruments, we also design and manufacture special instruments and accessories to implement a set of scientific measuring methods and procedures. This ensures good measurement repeatability and high precision.

After the successful development of the main parts of oil film bearings in rolling mills, the theoretical research on oil film bearings in rolling mills was driven by the continuous improvement of the installation level of rolling mills. The theoretical research work started in 1974. The main work at that time was to explore the working mechanism, establish mathematical models from the classical lubrication theory, numerical calculation methods, quasi-analytic methods, etc., and take the theoretical research one step further. In view of the classical theory of oil film peak pressure of more than 100MPa, and then carried out the application of elastohydrodynamic theory, at that time, some scholars who studied elastohydrodynamics only focused on the research of high secondary elastohydrodynamics of anti-shaped contact, while for sliding bearings, It is considered an atypical elastohydrodynamic problem, and some people even think that heavy-duty oil film bearings do not belong to the elastohydrodynamic category. After in-depth research, it is found that the circumferential distribution of the film thickness has obvious "necking", which is a unique phenomenon in the elastohydrodynamic theory, and the axial distribution behind the film is also different from the classical theory. The peak position of the oil film pressure moves backward, and , the eccentricity can be calculated to ε>1, which proves that the oil film bearing lubrication theory of rolling mill belongs to the elastohydrodynamic problem. With the development of modern tandem rolling mill towards high speed and heavy load, the thermal-elastic-hydrodynamic theory has been studied. At the same time, the research work on static-dynamic pressure lubrication theory has also been carried out in depth, and the first set of static-dynamic pressure oil film bearings in my country has been designed and developed.

For the product development of oil film bearings, our country designs and develops oil film bearings for rolling mills, which is based on the bearing products manufactured by the former Soviet Union in the early 1950s and a little factory information. The oil film bearings of rolling mills at that time were only suitable for low-speed rolling in terms of performance; in terms of structure, they were relatively old and inconvenient for assembly, disassembly and maintenance. Since the mid-1960s, my country has designed and manufactured thick plate and extra thick plate rolling mills and 1700mm hot and cold continuous rolling mills. Under the circumstances at that time, rolling mill bearings could only be developed by themselves. Due to the difficulty in manufacturing extra-large rolling bearings, oil film was used. bearings. The first generation of domestic rolling mill oil film bearings, represented by φ1300mm oil film bearings of 4200mm extra-thick plate rolling mills, belongs to low-speed and heavy-duty bearings, but has a greater improvement in structure than Soviet-style oil film bearings. The second generation of domestic rolling mill oil film bearings, with 1700mm thermal , The φ1100mm oil film bearing of the tandem cold rolling mill is represented, the rolling mill speed is increased, the structural design is improved, and the quickness of assembly and disassembly is improved; the third generation of domestic rolling mill oil film bearing is represented by the φ500mm static-dynamic pressure oil film bearing of the 650mm plate rolling mill , The bearing performance has been significantly improved, the carrying capacity has been doubled, and the structural design has also become more perfect, close to Morgan bearings. It is the third country in the world that independently designs and manufactures static-dynamic pressure oil film bearings after the United States and the former Soviet Union. The independent development capability of my country's oil film bearings for rolling mills is second only to the United States and the former Soviet Union, but we are superior to them in terms of in-depth research and form selection of static-dynamic oil film bearings. For example, regarding the design of the oil chamber, the United States adopts one oil chamber in the center, the former Soviet Union adopts four oil chambers, and my country adopts the axially symmetrical double oil chamber type. The cavity is improved to a double oil cavity type. The oil film bearing of the rolling mill is the contemporary level mark of the φ1350mmTZ brand oil film bearing developed for Jiuquan Iron and Steel Company in the early 1990s, which adopts symmetrical double oil chamber static-dynamic pressure oil film bearing hydraulic locking, new rotary seal, two-way thrust and quick assembly and disassembly and other advanced technologies.

In terms of complete set capacity, three types of oil film bearings for Chinese rolling mills have been used: pure static pressure, pure dynamic pressure, and static-dynamic pressure. Pure static pressure oil film bearings have not been promoted in the rolling mill industry. Pure dynamic pressure oil film bearings are widely used in various reversible rolling mills and hot tandem rolling mills. Static-dynamic pressure oil film bearings are mainly used in cold tandem rolling mills. Rolled on a reversing mill. Evaluate the complete set capabilities of these three types of oil film bearings, represented by static-dynamic oil film bearings: 

(1) Design and manufacture of the bearing body. In terms of design, the shape, size, quantity and position of the oil chamber are determined, and the main parameters of the bearing Selection, determination of static pressure system pressure, flow rate, viscosity, numerical calculation, selection, and manufacturing to ensure high load capacity, high operating accuracy, etc., can be completed by ourselves, and provide the user with the oil film thickness change required by the AGC system. 

(2) Ultra-high pressure oil supply system, in terms of system design, a safe and reliable ultra-high pressure oil supply system that meets the requirements can be designed according to the different rolling systems of the rolling mill, and an economical and reasonable pressure can be determined together with the bearing design —Flow parameters, the system is also equipped with a set of special devices to ensure the pressure balance of each oil chamber in the four bearings. In terms of ultra-high pressure components, in the early 1980s, my country has successfully developed a pump with a working pressure of 100MPa and a flow rate of 10L/min, a collector-splitter, a relief valve, a pressure gauge, a hose, a quick connector, etc., to realize Completed domestically and put into production. 

(3) Hydraulic locking and fast assembly and disassembly, quick assembly and disassembly, began to be used in products in the late 1970s, meeting the requirements of modern rolling mills, especially continuous rolling mills. In order to better control the axial pressing force of the taper sleeve and fast and safe assembly and disassembly, in the early 1980s, the hydraulic locking device was developed and has been successfully applied to the product. 

(4) Rotary seals. Modern rolling mills, especially continuous rolling mills, have continuously increased rolling speeds, and the requirements for bearing rotary seals have become more and more stringent. On the basis of absorbing the advantages of various contemporary rotary seals, the form of rotary seals in my country has been gradually improved and formed, and the mold design, rubber formula, vulcanization process, physical and chemical inspection and finished product testing are all mature and complete. 

From the six aspects listed above, it is not difficult to see that my country can design and manufacture dynamic pressure, static-dynamic pressure rolling mill oil film bearings and dynamic pressure, static pressure oil supply system in a complete set to meet the requirements of various modern rolling mills. It can be said that China's rolling mill oil film bearing technology has become a complete system engineering technology. With foreign advanced manufacturing technology, it is moving towards a higher level.