The four-row cylindrical roller bearings, as the core supporting components of the rolling mill's roller system, mainly bear huge radial loads. Their performance directly determines the rolling accuracy, production efficiency and operational stability of the rolling mill. With the development of the rolling process towards ultra-thin specifications, high-strength materials and high-speed continuous production, the bearings are facing unprecedented challenges: 

Extreme load conditions: The rolling force keeps increasing, which requires the bearings to have higher rated dynamic and static load-bearing capabilities. 

Harsh operating environment: High temperatures during hot rolling, iron oxide scale, cooling water, as well as emulsions in cold rolling, pose severe challenges to the sealing, lubrication and material durability of bearings. 

Accuracy and lifespan requirements: High-end sheet materials have extremely high requirements for thickness and plate shape accuracy. Bearings need to have extremely high rotational accuracy and operational stability, and at the same time, a longer service life is pursued to reduce maintenance costs. 

Load imbalance and deformation effects: Under the action of rolling force and bending roll force, the rolls will undergo elastic bending, resulting in a severely non-uniform distribution of load within the bearings, which leads to local early fatigue failure. 

To address these challenges, the modern design and optimization direction should exhibit the following major trends: 

Structural performance optimization: Through topology optimization and extreme design, the bearing capacity of a single bearing is maximized. 

2. Force state optimization: Through geometric modification, active compensation of uneven load deformation is achieved to achieve uniform stress distribution. 

3. Integration of Materials and Sealing: Utilizing high-performance materials (such as rare earth steel, and applying surface treatment methods) in conjunction with lubrication and sealing technologies to jointly provide a reliable operating environment. 

4. Intelligence: Achieve real-time status monitoring and predictive maintenance. 

Load release aspect: 

Large rollers and high-density arrangement: By applying the extreme design method, the internal space layout of the bearing is optimized. While ensuring strength, larger-diameter and longer-length rollers are used, and the number of rollers is increased to directly enhance the basic load-bearing capacity. 

Structural aspect: 

Snap-fit welding cage: Suitable for extremely large-sized bearings (such as FCDP type), it has a sturdy structure and can withstand huge centrifugal force and impact loads. At the same time, oil guide grooves and oil storage pits are designed on the crossbars or pillars of the cage to improve the lubrication at the end of the rollers, reduce sliding friction and temperature rise. 

Optimization of outer ring lubrication holes: Adjust the number, angle and position of the lubrication holes to ensure that the lubricating oil can precisely and evenly reach each row of rollers. 

Employing a composite seal: Utilizing a combination of "three-piece frame seal + labyrinth seal + V-shaped fluid water seal + protective cover", multiple layers of protection are formed, effectively preventing water and debris from entering and preventing lubricating oil from leaking. 

Through the above comprehensive optimization, combined with on-site application, scientific management and regular maintenance, it achieves precise and effective reduction of overall losses, as well as improvement of bearing lifespan and stability.