Technical Papers by Chengdu Heavy-Duty Research Institute(Section)
Resource from: CBCC Likes:3020
Oct 20,2006
The Ways to Improve Bearing’s Life for Jobbing Sheet Rolling Mill
Chengdu Heavy-Duty Research Institute Author: Wen Jianhen 1. Introduction 1.1 Bearing’s Life Generally speaking, the rolling bearing’s limit service time under certain conditions is defined as its life, which can be divided into three types: fatigue life, precision & performance life and abnormally (or accidentally) damaged life. Precision & performance life refers to the bearing’s service time by which the bearing is scrapped because its precision or performance (e .g. noise, vibration, high& low temperature resistance, corrosion resistance and radiation hardening, etc) can’t satisfy the requirements of the machine; the abnormal damage refers to parts’ crushing, falling apart, burning, seizing, severe deformation and so on, caused by the bearing’s designing, manufacturing and improper use. When abnormal damage occurs, it is wise to find out the reasons and take proper measures to solve the problem to avoid decrease in service life and increase in consumption. For the rolling mills and most machines, the normal damage refers to the fatigue damage to the rolling surface of the bearing. It is showed in the tests and practice that the bearings’ fatigue lives vary under the same condition—their longest life/shortest life ratio varies several times, even tens of times. The mathematical statistics are introduced into the definition of fatigue life and its formula is as follows: L10=α１α２α３(C/P)ε(unit: 106 r) (1) Where, L10—basic rating life, that is bearing life when the failure probability is 10%(or non-failure probability is 90%).Unit: 106 r. α１—adjusted factor when the failure probability＜10% .From the experiment, when the failure probability is 50%, L50=4～5L10; α２—material quality factor, which is replaced by bm factor adjusted dynamic load rating; α３—lubrication factor, which is changed to be operating condition factor; C—basic dynamic load rating KN(or N) calculated from bearing designing; P—dynamic equivalent load KN(or N) ε—life exponent, for ball bearingε=3,for roller bearingε=10/3 1.2 Structure feature of rolling mill bearing In terms of width and thickness of the sheet material, the rolling mills’ rolling forces vary from hundreds of tons to 3000～7000 tons, and the speeds vary from a few meters per second to 30 meters per second. The radial designing space of the bearing and bearing housing is small due to the limitation of mill roll’s dimension. To satisfy the requirements of heavy duty, high speed and small radial space mentioned above, four-row tapered roller bearing and four-row cylindrical roller bearing are widely used for the support roll and the working roll of the jobbing sheet rolling mill. Meanwhile, given the working roll should be grinded frequently and mounted &dismounted easily, if proper clearance fit is adapted between the four-row tapered bearing’s ID and the working roll’s neck, then small clearance value(normally Ｃ２group) should be taken; if interference fit(or transition fit) between the inner ring(without flange)’s ID and the shaft neck is taken, then great clearance value(normallyＣ３ group) should be taken. ``` ===to read the full article, visit the following link=== http://www.khzz-bearing.com/english/seenews.asp?d_id=141
Chengdu Heavy-Duty Research Institute Author: Wen Jianhen 1. Introduction 1.1 Bearing’s Life Generally speaking, the rolling bearing’s limit service time under certain conditions is defined as its life, which can be divided into three types: fatigue life, precision & performance life and abnormally (or accidentally) damaged life. Precision & performance life refers to the bearing’s service time by which the bearing is scrapped because its precision or performance (e .g. noise, vibration, high& low temperature resistance, corrosion resistance and radiation hardening, etc) can’t satisfy the requirements of the machine; the abnormal damage refers to parts’ crushing, falling apart, burning, seizing, severe deformation and so on, caused by the bearing’s designing, manufacturing and improper use. When abnormal damage occurs, it is wise to find out the reasons and take proper measures to solve the problem to avoid decrease in service life and increase in consumption. For the rolling mills and most machines, the normal damage refers to the fatigue damage to the rolling surface of the bearing. It is showed in the tests and practice that the bearings’ fatigue lives vary under the same condition—their longest life/shortest life ratio varies several times, even tens of times. The mathematical statistics are introduced into the definition of fatigue life and its formula is as follows: L10=α１α２α３(C/P)ε(unit: 106 r) (1) Where, L10—basic rating life, that is bearing life when the failure probability is 10%(or non-failure probability is 90%).Unit: 106 r. α１—adjusted factor when the failure probability＜10% .From the experiment, when the failure probability is 50%, L50=4～5L10; α２—material quality factor, which is replaced by bm factor adjusted dynamic load rating; α３—lubrication factor, which is changed to be operating condition factor; C—basic dynamic load rating KN(or N) calculated from bearing designing; P—dynamic equivalent load KN(or N) ε—life exponent, for ball bearingε=3,for roller bearingε=10/3 1.2 Structure feature of rolling mill bearing In terms of width and thickness of the sheet material, the rolling mills’ rolling forces vary from hundreds of tons to 3000～7000 tons, and the speeds vary from a few meters per second to 30 meters per second. The radial designing space of the bearing and bearing housing is small due to the limitation of mill roll’s dimension. To satisfy the requirements of heavy duty, high speed and small radial space mentioned above, four-row tapered roller bearing and four-row cylindrical roller bearing are widely used for the support roll and the working roll of the jobbing sheet rolling mill. Meanwhile, given the working roll should be grinded frequently and mounted &dismounted easily, if proper clearance fit is adapted between the four-row tapered bearing’s ID and the working roll’s neck, then small clearance value(normally Ｃ２group) should be taken; if interference fit(or transition fit) between the inner ring(without flange)’s ID and the shaft neck is taken, then great clearance value(normallyＣ３ group) should be taken. ``` ===to read the full article, visit the following link=== http://www.khzz-bearing.com/english/seenews.asp?d_id=141
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1.The news above mentioned with detailed source are from internet.We are trying our best to assure they are accurate ,timely and safe so as to let bearing users and sellers read more related info.However, it doesn't mean we agree with any point of view referred in above contents and we are not responsible for the authenticity. If you want to publish the news,please note the source and you will be legally responsible for the news published.
2.All news edited and translated by us are specially noted the source"CBCC".
3.For investors,please be cautious for all news.We don't bear any damage brought by late and inaccurate news.
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