Four-row Short Cylindrical Roller Bearings Of The Rolling Mill

The four-row short cylindrical roller bearings of the rolling mill are the core components of the working rolls and supporting rolls of the rolling mill (covering both hot rolling and cold rolling), belonging to the category of roller bearings. They are specially designed to withstand high radial rolling forces and can directly ensure the stable operation of the rolling mill and the accuracy of the strip rolling. Their structure adopts a four-row short cylindrical roller layout, with the rolling elements being short and thick (having a small length-to-diameter ratio), and the inner ring mostly being detachable. The outer ring is thickened and reserved for grinding, and some models have guard edges that can withstand a small axial force. Depending on the application scenario, the design can be without cage or with a brass cage. In terms of performance, this bearing has extremely strong radial bearing capacity. For example, for the model FC5688240, its basic rated dynamic load can reach 6800kN. At the same time, it has excellent impact resistance; the friction coefficient is low, which can meet the requirements of high-speed rolling of the rolling mill (line speed can reach 30m/s), and the precision grade is mostly P5 or P4, ensuring the smooth operation of the roll system. The application scenarios mainly include the rough and finishing rolling units of hot-rolled strip rolling mills, the supporting rolls and working rolls of cold-rolled sheet and strip rolling mills, as well as medium-thick plate rolling mills, etc., and can be adapted to the rolling processing of steel, non-ferrous metals, etc. In terms of installation and maintenance, the inner ring of the bearing needs to have a tight fit with the shaft, the outer ring needs to have a clearance fit with the bearing housing, and during installation, it is necessary to align according to the marks to avoid uneven loading; lubrication requires the use of circulating lubricating oil with a cleanliness level below NAS 7, and daily maintenance requires regular checks of the wear of the rollers and the clearance, and after the outer ring is worn, it can be reused through regrinding.

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Product Introduction

The four-row short cylindrical roller bearings, as an important sub-type of cylindrical roller bearings within the family of roller bearings, are the core transmission and load-bearing components of steel rolling equipment. They play a crucial role in hot rolling and cold rolling rolling machine units, directly influencing the stability of the rolling machine operation and the accuracy and quality of the rolled strip materials.
From the perspective of structural design, this bearing adopts a four-row short cylindrical roller layout, with the rolling elements in a short and thick shape, and the length-to-diameter ratio usually ranging from 1.2 to 2.0. This design significantly increases the contact area between the rolling elements and the cage, enhancing the radial load-bearing capacity. The inner ring is mostly of a separable structure, divided into double inner rings or integral inner rings with spacer rings in two forms. The double inner ring design is convenient for individual installation and replacement, meeting the requirements of the disassembly and maintenance of the rolling machine's roller system; the outer ring adopts a thickened design, with a wall thickness typically 15%-25% higher than that of ordinary cylindrical roller bearings, and a 3-5mm grinding allowance is reserved. When the outer ring raceway is worn, it can be restored to accuracy through professional grinding, extending the bearing's service life. Some models of bearings have single-sided or double-sided guard edges, capable of bearing a small axial force (generally 5%-10% of the basic rated radial load), which can cope with the slight axial movement generated during the operation of the rolling machine, while the models without guard edges need to be paired with thrust bearings to withstand the axial force. Regarding the cage, according to the working conditions, it is divided into brass solid cages and stamped steel cages. The brass cage has higher strength and wear resistance, suitable for high-speed and heavy-load conditions, such as cold rolling units with a rolling speed exceeding 15m/s. The stamped steel cage is widely used in medium and low-speed, general load scenarios, reducing production costs.
In terms of performance, the core advantage of this bearing lies in its extremely strong radial load-bearing capacity. Taking the common model FC4872200 as an example, with a bore diameter of 400mm, an outer diameter of 540mm, and a width of 200mm, the basic rated dynamic load can reach up to 5800kN, and the basic rated static load can reach 9200kN. It can withstand thousands of kilonewtons of radial force generated during the rolling process of the rolling machine, meeting the usage requirements of heavy-load equipment such as medium-thick plate rolling machines and hot continuous rolling machines. At the same time, the bearing adopts high-precision manufacturing processes, with precision grades mostly at P4 or P5 levels. The radial runout error of P4-grade bearings is controlled within 0.005mm, and the radial clearance can be precisely adjusted according to the working conditions, typically ranging from 0.015 to 0.035mm, effectively ensuring the smooth operation of the rolling machine's roller system and reducing the thickness deviation of the rolled strip materials. Moreover, the bearing has a low friction coefficient, generally ranging from 0.001 to 0.002. In high-speed rolling scenarios (such as a cold rolled strip rolling speed of up to 30m/s), it can reduce energy loss and heat generation, and with a reasonable lubrication system, it can achieve long-term continuous and stable operation.
In terms of application scenarios, this bearing is widely applicable to various rolling machine equipment. In the hot rolling field, it is mainly used in the supporting rollers of the roughing and finishing sections of hot continuous rolling machines, as well as the working rollers and supporting rollers of medium-thick plate rolling machines, such as in a hot continuous rolling production line with an annual output of 30 million tons, the finishing section supporting rollers often use this type of bearing, capable of withstanding high temperatures, heavy loads, and impact loads; in the cold rolling field, it is commonly used in the supporting rollers of cold rolling strip rolling machines, especially in cold rolling units for high-precision strip materials such as stainless steel and silicon steel, such as the supporting rollers of a 20-roll cold rolling machine, leveraging its high-precision characteristics to ensure the surface quality and thickness tolerance of the strip materials; in addition, it is also applied in the finished machine frames of profile rolling machines and bar rolling machines, suitable for the rolling processing of different specifications of metal materials.

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