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Research on the Influence of Rolling Mill Speed Increase on Four-row Cylindrical Roller Bearings and Optimization Measures

wallpapers News 2020-11-20
The speed of the rolling mill in the steel mill was increased, which caused an excessive temperature rise of the four-row cylindrical roller bearings on the backup rolls. In view of this problem, the friction torque and calorific value of the bearing before and after the speed increase are calculated and compared, and it is shown that the influence of speed on the friction torque is not obvious, and the calorific value is approximately proportional. The bearing has been optimized to reduce temperature rise. The main measures taken are to reduce the contact area of the sliding parts, add a heat dissipation oil circuit; reduce the roughness of the contact surface; optimize the bearing oil hole to improve the heat dissipation effect. A simplified calculation method for the point contact between the roller end face and the rib is proposed. After the optimized bearing is applied, the temperature rise is obviously slowed down and the service life is improved.
 
With the continuous advancement of supply-side structural reforms and unprecedented pressure on environmental protection, a large number of steel mills have been included in the ranks of reducing production capacity, and domestic large steel mills have temporarily exceeded supply, so they have adopted an increase in rolling speed to achieve The purpose of efficiency enhancement. The four-row cylindrical roller bearings for the support rolls of a cold-rolled 1250 line in a steel mill increased the speed from 197r/min to 257r/min under the condition of the same rolling force and lubrication method. After the speed is increased, the bearing temperature rises too high many times and alarms and stops. According to incomplete statistics, this model is used in about 200 lines of nearly 20 domestic steel mills, and the market utilization rate is very high, which has a certain value for its optimized design. The structure of the four-row cylindrical roller bearing is shown in Figure 1. The external dimensions are Φ690×Φ980×750, the material is G20Cr2Ni4A, the cage is welded by pillars, the accuracy grade is P5, and the load capacity Cr is 20700kN and Cor is 56500kN. The relevant requirements of the bearing comply with the standard JB/T5389.1.
 
Through the above optimization measures, the optimized bearing was installed and tested in the steel plant, and the bearing usage was tracked and recorded. Under the working condition of the maximum speed of 250r/min and the maximum rolling force of about 1000t, the bearing has not been used until now (5 months in use). The temperature is too high. The optimized bearing meets the operating conditions after speed increase.
 
Increasing speed and efficiency has become the future development trend of the steel industry, and the design of four-row cylindrical roller bearings should also be developed in the direction of reducing temperature rise. The measures taken are on the one hand to reduce the rolling-sliding friction of the contact surface, and on the other hand to study effective measures for bearing heat dissipation. At present, the heat and heat dissipation theory of bearings still needs to be studied more deeply and systematically. In engineering applications, relevant theories should also be actively converted into practice, especially in the bearing development and design stage.

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