Four-row circular roller bearings

Main features: 

A. The bearing has the maximum radial load-bearing capacity within a limited installation space. 

B. Bearings can be used for high-speed rotation: 

C. The inner ring allows for interchangeability with the outer components (outer ring, complete set of rollers), facilitating quick wheel replacement.

Representation methods of structural forms and codes

The four-column cylindrical rollers in the bearing mainly include the FC type (two outer rings and one inner ring), the FCD type (two outer rings and two inner rings), and the FCDP type (two outer rings, two inner rings, and with retaining rings). 

FC - Type A: The outer ring has no oil groove or oil hole, while the end face of the outer ring has an oil groove. 

FC - Type B: The outer ring has oil grooves and oil holes, and the end face of the outer ring has oil grooves. 

FCD Type A: The outer ring has no oil groove or oil hole, while the end face of the outer ring has an oil groove. 

FCD - Type B: The outer ring has oil grooves and oil holes, and the end face of the outer ring has oil grooves. 

FCD - Y type: The outer ring has no oil groove or oil hole, the end face of the outer ring has an oil groove, and there is a gasket between the two outer rings. 

FCD - 2LS type: Outer ring has no oil groove or oil hole, sealed type 

FCDP - Type E: The outer ring has oil grooves and oil holes, the inner ring end face has oil grooves, and the retaining rings are of the column-pin type (hollow rollers) or solid window type.

Accuracy and clearance

This type of bearing is widely used in the roller system of metallurgical rolling mills. Its clearance and accuracy vary depending on the specific application, and generally follow the following rules: Generally, the clearance for hot-rolled products should be larger, typically P6 accuracy C4 group clearance. The clearance for cold-rolled products should be smaller, typically P5 accuracy C3 group clearance. For other special conditions, specific C0 or certain C9 clearance as well as P4 accuracy are also required. For example, in the roller system of hot-rolled long products (angles, channel steels, spherical flat steels, rods, etc.), P6 accuracy C4 group clearance is usually selected; while for cold-rolled sheet or plate products (copper strips, aluminum plates, tinplate, galvanized sheets, household appliance plates, etc.), P5 accuracy C3 group clearance is used; and in specific rolling machines and equipment such as battery skins, aluminum foils, copper foils, specific C9 clearance and P4 accuracy are required.

Selection of materials

High-carbon chromium bearing steel (such as GCr15, GCr15SiMn) 

Features: This is the most widely used type of bearing steel. After heat treatment, it possesses high hardness and excellent wear resistance as well as fatigue resistance. 

Application scenarios: Typically used in situations where there is a stable high load and relatively small impact. For example, the FC structure four-row cylindrical roller bearings mostly use this type of material. It is mainly applied in the size range of inner diameter ≤ 350mm, such as in the roller systems of long strip hot rolling mills, cold rolling working rolls and intermediate roll systems. 

Carburized bearing steel (such as G20Cr2Ni4A) 

Features: After being treated with carburizing and quenching, this type of steel will exhibit the characteristic of "hard exterior and flexible interior". Its surface has a very high hardness, ensuring good wear resistance; while the core has a lower hardness, still maintaining excellent toughness. 

Application scenarios: This excellent toughness enables it to withstand intense impact loads, with outstanding fatigue resistance and surface peeling prevention capabilities. Therefore, it is often used in harsh working conditions and high-impact situations, such as during the initial rolling of hot-rolled billets or in the roller system of cold rolling, mainly in the size range of inner diameter > 350mm.