Types of bearings used in cold rolling production lines

Sep 10, 2024

In cold rolling production lines, roll neck bearings are key components, and their selection and application are crucial to ensure the stable rotation of the production line, improve product quality and extend equipment life. The characteristics of cold rolling production lines include large loads, large differences in working speeds, harsh working environments and frequent roll changes. These characteristics determine that the required bearings must have high load capacity, high precision, high limit speeds, and good sealing and lubrication properties.

1. Characteristics of cold rolling production lines and their requirements for bearings

High load: Bearings on cold rolling production lines need to withstand loads 2-5 times higher than ordinary bearings, which places extremely high demands on the bearing capacity and material strength of bearings.

Large differences in working speeds: Different equipment on the production line has different working speeds, and bearings need to adapt to this speed change and maintain a stable operating state.

Harsh working environment: A large amount of dust, particulate matter, lubricating fluid, iron filings and other debris will be generated during the cold rolling process. This debris can easily enter the bearing and affect its normal operation. Therefore, the bearing needs to have good sealing performance.

Frequent roll changes: The cold rolling production line needs to replace the rolls regularly, and the ease of disassembly and assembly of the bearing is also an important consideration when selecting.

High rigidity and high precision: Cold-rolled products have strict requirements on dimensional accuracy and surface quality, so the bearings need to have high rigidity and high precision to ensure the processing quality of the products.

2. Common bearing types and characteristics on cold rolling production lines

Spherical roller bearings

Spherical roller bearings have the characteristics of self-aligning, which can automatically adapt to the angular error caused by shaft deflection or box deformation, thereby ensuring the normal operation of the bearing. This type of bearing is usually used on the support rollers of small strip mills. It has a simple structure, is easy to install, and can withstand a certain axial load. However, due to its limited self-aligning ability, it is not suitable for occasions with excessive load or high speed.

Four-row tapered roller bearings

Four-row tapered roller bearings can withstand large radial and axial forces and are ideal for large rolling mill support rollers. The bearings must be assembled strictly according to the serial number to ensure that the rollers in each row are evenly stressed. The four-row tapered roller bearing has a strong load-bearing capacity, but the structure is relatively complex, and special attention should be paid during disassembly and assembly. In addition, since it can bear radial and axial loads at the same time, four-row tapered roller bearings can simplify the design of the bearing seat and reduce production costs.

Multi-row cylindrical roller bearings

Multi-row cylindrical roller bearings have the advantages of low friction coefficient, small radial size, and high manufacturing precision. Its inner ring is detachable, easy to disassemble and assemble, and is widely used in the working rolls and support rolls of high-speed four-roll mills. The use of such bearings can increase the roll neck size, improve the load capacity and limit speed. However, multi-row cylindrical roller bearings do not bear axial force, and thrust bearings need to be added to bear axial loads. In addition, its manufacturing cost is relatively high, but it has a significant effect on improving production efficiency and product quality.

Needle roller bearings

Needle roller bearings are popularly used in the work roll transmission system of cold rolling production lines due to their large load capacity and ability to increase the work roll neck size. This bearing is suitable for rolling mills that transmit large torques and can effectively improve the transmission efficiency and stability of rolling mills. However, needle roller bearings have high requirements for installation accuracy and need to maintain good lubrication during use to avoid wear and failure caused by poor lubrication.

3. Selection and treatment of bearing materials

The bearings on the cold rolling production line need to withstand high temperature, high pressure and corrosive media, so it is very important to choose the right bearing material. Common bearing materials include steel, ceramics and plastics. Among them, steel bearings are widely used because of their good load-bearing capacity and wear resistance. However, the traditional GCr15 bearing steel has a high impurity content and poor fatigue strength and impact resistance. In order to improve the load-bearing capacity and service life of the bearing, carburized steel that has been vacuum melted or electro-slag remelted can be used instead of GCr15 bearing steel. In addition, the lower bainite isothermal quenching technology has also been well applied in rolling mill bearings, which can effectively improve the impact toughness, fracture toughness, and wear resistance of the bearing.

4. Sealing and lubrication of bearings

The bearings on the cold rolling production line need to have good sealing performance to prevent dust, water and other debris from entering the bearing. To this end, improvement measures such as adding end face sealing rings can be used to improve the sealing effect of the bearing seat. In terms of lubrication, grease is mostly used for the lubrication of roller bearings, and oil lubrication is used at high speeds. The selection of grease needs to be comprehensively considered based on factors such as speed, ambient temperature and load conditions. Reasonable selection of lubricants and ensuring that they are sufficiently clean are essential to extend the service life of bearings.

5. Maintenance and care of bearings.

In order to ensure the normal operation of bearings on cold rolling production lines and extend their service life, they need to be cleaned, inspected and replaced regularly. The inspection content includes the wear and clearance of the inner and outer raceway working surfaces and rolling element surfaces. Bearings that exceed the standard or are damaged should be replaced in time. In addition, a bearing use file should be established to record the disassembly, replacement and lubrication of bearings in detail for subsequent management.

In summary, the types of bearings used in cold rolling production lines are diverse, and each has its characteristics. When selecting and applying bearings, it is necessary to comprehensively consider factors such as the working conditions, load requirements, precision requirements and convenience of maintenance of the production line. By reasonably selecting bearing types, materials, sealing structures and lubrication methods, the stable operation of the cold rolling production line can be ensured, and product quality can be improved.