VISTA Technology Knowledge: Brief View on Inter Factory Exchange of Four Row Cylindrical Roller Bearings for Rolling Mill

Hot tags: four row cylindrical roller bearing (1)

Basic status and existing problems and the conditions for rolling bearing in different factories

 图片1.png

Abstract: in view of the difference in the design and implementation methods of radial clearance of four row cylindrical roller bearings for rolling mills, which are widely used in the metallurgical industry at present, when different bearing manufacturers leave the factory, resulting in the non-interchangeability of users when using this type of bearings, the causes are analyzed and the solutions are put forward.

 

Key words: roller bearing; four row cylindrical roller bearing; interchangeability; analysis

 

1. Basic status and existing problems

Four row cylindrical roller bearing for rolling mill is a kind of bearing widely used in rolling mill roll system in metallurgical industry. The coding method and structural parameter design of this type of bearing are not unified in various countries. Since the 1970s, China began to use this type of bearing to replace bakelite tiles. 672000 is used to represent the four row cylindrical roller bearings for rolling mills in the method of compiling bearing codes. In the 1980s, FC00000000 / PXY or FCD000000000 / PXY began to be used to represent four row cylindrical roller bearings for rolling mills. The prefix FC was used for the type code to represent four row cylindrical roller bearings. The first and second digits behind FC represented the inner diameter of the bearing (nominal inner diameter mm / 5), the third, fourth and fifth digits represented the outer diameter of the bearing (nominal outer diameter mm / 5), and the sixth and seventh digits represented the width of the bearing, PX after the slash indicates the tolerance class of the bearing, and Y indicates the radial clearance group of the bearing. The code preparation method of four row cylindrical roller bearings of foreign manufacturers is different from that of China, and also different from country to country. See Table 1.

 

Table 1 code comparison of four row cylindrical roller bearings in different countries (companies)

 

National

bearing code

Bearing boundary dimension / mm

China

FCD88124450

 

440* 620* 450

Sweden SKF

314554B

 

Germany FAG

517454A

 

Japan NSK

440RV6213

 

Japan NTN

4R8801

 

 

For bearings with the same overall dimensions, there are differences in the design of structural parameters of bearings due to differences in the selection of bearing materials and processing technology in various countries, which is mainly reflected in the inner diameter of the roller group (i.e. internal rounding). The four row cylindrical roller bearings used in rolling mills as the main bearing unit of the radial load when the rolls of modern rolling mills work have many advantages over the original bakelite tile support. One of them is that the needs of rapid disassembly and assembly of rolls are considered in the design, and their inner rings are made interchangeable. Theoretically, the inner rings of four row cylindrical roller bearings with the same model, the same radial clearance group requirements, different manufacturers and different batches should be interchangeable, and the radial clearance group of the exchanged bearings should be the same. However, the actual situation in our country is not so. Incongruous phenomenon (large or small radial clearance) occurs when the bearings of the same model from different bearing manufacturers are exchanged at the same user's site, resulting in premature bearing failure.

 

2. Conditions for bearing inner ring exchange

(1) The inner diameter of roller set belongs to the structural design parameters of bearings. Designers from different countries and manufacturers have different ideas when designing the structural parameters of four row cylindrical roller bearings (involving raw materials, rated dynamic load, heat treatment process, operating conditions and lubrication conditions, etc.). Even for bearings of the same model, the value of the inner diameter of roller set may be different. For example, the inner diameter of FC4666206 / P64 roller set has two types: 257mm and 260mm. At present, the inner diameter of roller group cannot be reflected from the code of four row cylindrical roller bearings in China. When ordering, if the inner diameter of the roller set is not specified after the code of the four row cylindrical roller bearings, when several manufacturers provide the same type of bearing, if the user does not carry out technical coordination, there may be differences in the inner diameter of the roller set of the same type of bearing provided by various manufacturers, resulting in that the bearings cannot be interchanged.

 

(2) The radial clearance of four row cylindrical roller bearings is realized by the tolerance of the ring raceway. At present, there are two methods to design and realize the radial clearance of four row cylindrical roller bearings. One is the basic shaft system method, that is, the dimensional tolerance of the inner ring raceway is determined according to the bearing inner diameter dimension range, and the radial clearance of different groups of the bearing is realized by the dimensional tolerance change of the outer ring raceway (that is, the required radial clearance is obtained by grinding the outer ring raceway). This method is called the one-way tolerance method (or daily order subtraction). For example, the bearing of a certain dimension segment can be expressed as: the upper deviation of the inner race raceway dimension tolerance is zero, and the lower deviation is 0.04mm. This method is not scientific enough. For large clearance group bearings, it is easy to cause changes in the diameter of the center circle of the roller and interference between the roller and the outer side of the cage pocket. The other is the basic hole method, that is, the dimensional tolerance of the outer ring and roller assembly is determined according to the bearing inner diameter dimension range. The radial clearance of different groups of the bearing is realized by the dimensional tolerance change of the inner ring raceway, that is, the required radial clearance is obtained by grinding the inner ring raceway dimension based on the calculation data. This method is called the two-way tolerance method (or double subtraction). Taking FC3652168 / P64 as an example, the upper deviation of the inner race raceway dimension tolerance is 0.17il1ril, and the lower deviation is 0.205mm. This method is scientific and suitable for mass production. In the machinery industry standard JB / T5389.1-1995 (four row cylindrical roller bearings for rolling bearing mills), the base hole method is adopted, which is mostly adopted by foreign famous bearing manufacturers.

 

(3) In reality, there is another method to realize the radial clearance of different groups of bearings, that is, the mixed tolerance method. This method is caused by the designer's poor understanding of JB / T5389.1-1995 (four row cylindrical roller bearings for rolling bearing mills). In the "table A6" (inner race diameter deviation) given in JB / T5389.1-1995, the inner race diameter deviation was originally given according to the basic group clearance of the bearing. If the designed bearing clearance is not the basic group clearance, it should be corrected before reuse, otherwise, For bearings larger than the basic group clearance, in order to achieve the radial clearance required by the design of the finished bearing, the size of the outer ring raceway has to be grinded again, resulting in the realization of the radial clearance of the bearing to be realized by the grinding of the raceways of the inner and outer rings of the bearing.

 

Only when the inner diameter of the bearing roller group (inner circle size) is the same, and the design and implementation method of the radial clearance are the same, the exchange conditions of the bearing inner ring can be met.

 

3. Conclusion

In view of the confusion of the mill bearing manufacturers in the above problems, we propose that the competent technical department of the industry coordinate this problem or further explain the relevant standards. In addition, it is necessary to strengthen the explanation and publicity to users on this issue. The most important thing is that users should clarify the following points when ordering four row cylindrical roller bearings for rolling mills:

(1) Write down the bearing model: FC3652168P64.

(2) Write down the inner diameter of the roller set of the bearing.

(3) Write down the requirements for the radial clearance group of the bearing.

(4) The realization method of bearing radial clearance is clearly put forward, that is, whether the outer race of inner race is single or double reduction.

(5) Check the radial clearance and outer raceway dimension of inner ring of four row cylindrical roller bearings used for rolling mills of the same model from various manufacturers.

 

More about VISTA Four Row Cylindrical Roller Bearing :   

Vista four row cylindrical roller bearing High-quality brand have excellent reputation and popularity, good after-sales service system, fast, and guaranteed product quality!

 

 

As a leading global four row cylindrical roller bearing manufacturer and supplier in China, we're featured by perfect solution for many kinds of bearing supplying,competitive price and fast delivery for each customer. Please rest assured to buy four row cylindrical roller bearing at the best price from Vista. For any special requirement, contact us now.

 

With a cylindrical or tapered bore, and open or sealed design, these bearings can accommodate very heavy radial loads because of the high number of rollers and are well suited for rolling mill applications with high rolling speeds.

 

Four Row Cylindrical Roller Bearing  


2022-06-18

Vista Bearing

Shanghai, Kina,Victoria, Australien,Californien, USA
© 2020 VISTA Bearing All rights reserved. | Sitemap