Abstract: Rolling mill bearing plays an important role in rolling mill in our country, rolling mill bearing often occurs mechanical burning loss in daily production, how to reduce the number of burning loss of rolling mill bearing, improve the level of rolling mill equipment, improve the operation rate of rolling mill, this paper analyzes the cause of rolling mill bearing burning loss.
Preface
In the process of rolling mill production, rolling mill bearings will be burned or bearing frame will smoke, which will affect the production and bring some economic and cost losses to enterprises. Therefore, to improve the stability of rolling mill, improve the quality of rolling mill products and ensure the smooth production of rolling mill assemblers put forward a key task.
1. The reasons for rolling mill bearing failure can be roughly divided into two aspects:
1) Internal reasons, such as bearing quality.
2) External reasons, such as installation, maintenance, maintenance, etc. In order to find out the reasons and take better targeted measures, it is very important to analyze the cause of burning loss.
2. Analysis of causes of burning loss
1) Assembly problems
A. Because the manufacturing accuracy of the rolling mill is not very high, when the service life is long, various parts of the rolling mill will be deformed to different degrees, and the bearing seat will have a large coaxiality difference, which makes the bearing at both ends of the rolling mill bear uneven force. When the lubrication is not enough, it is easy to produce high friction heat, resulting in local pitting corrosion or locking of the bearing. According to the actual situation of the rolling mill, use cleaning agent before installation, clean the bearing, blow dry with compressed air, then check the roller, cage and raceway, rotate the cylindrical roller bearing with a tool, the bearing can be smooth and linear rotation can continue to use. Roller, raceway dents, pitting and other phenomena, to replace.
B. Labyrinth labyrinth, dynamic and static precision of size, geometry, also affect the mill bearing damage, the lack of for moving maze is following the roll rotation, such as the labyrinth of dynamic and static deformation after coordination, waterproof circle may because some one local discontinuity in the process of rotating friction, on the local stress concentration, when the friction frequent will generate a lot of heat, And transferred to the rolling mill bearing, when the heat is too high, grease will be thin to the outside of the seal ring loss, resulting in bearing burning or friction smoke. Before assembly, check the integrity of the static and static maze, remove the foreign matter and impurities attached, and compare the good performance of the match, avoid wear caused by processing error, and replace the ones that can't be repaired in time.
2) Insufficient lubrication
Friction is inevitable as long as there is movement, and the most effective measure to reduce friction is to add lubricating materials. Rolling bearing in the movement of both flow friction, and sliding friction, cylindrical roller is a very hard rotating body, working in the bearing inner ring and outer ring to do rotation and sliding movement, so the friction coefficient is very small, as long as ensure a good layer of lubrication film can ensure good lubrication.
But in the work often occurs because of lubrication problems caused by burning bearings, mainly the amount of oil and fuel problems. At present, the mill grease we use is complex calcium sulfonate base 3# grease with strong adsorption capacity and can form high strength oil film. Requirements on oil when the assembly must at the same time, all the bearing inner ring coated with grease, to ensure that the bearing has sufficient lubrication conditions, for long time use of rolling mill, lubrication performance in the process of using gradually reduce, wear also gradually increased, to adopt lubricated periodically, using pressure oil pump obsessive refueling refueling gun, to ensure normal lubrication conditions.
3) Foreign body influence
A foreign body is what is called a foreign impurity and it has several main aspects:
A. Other impurities in the grease;
B. Foreign matter enters into the bearing during disassembly and assembly;
C. Local damage caused by the impact of parts in the assembly process;
D. Water and dust at work. The most common is grease and foreign matter in the process of disassembly and assembly.
When the diameter of the foreign body is less than the working clearance of the bearing, it can be stirred by grease to cause friction and strain on the ball working face, and make the bearing wear and failure in advance; When the foreign body is greater than the working gap, the foreign body is rolled and crushed, and part of the foreign body is embedded in the working surface, resulting in stuck. The debris not embedded in the working surface will be involved in the oil, which aggravates the bearing wear surface, causes the temperature of the working surface to rise sharply, and quickly wears out the oil film, causing the bearing to burn under dry grinding state. Therefore, it is a key aspect of our work to strictly control foreign matter entering into the bearing.
Bearing seal and prevent water and foreign matter into the important device, but also bear the function of preventing leakage of lubricating oil, due to the vertical mill roll in spinning on its architecture, water and impurity easily through the clearance between the suite, along with the roll rotation into the bearing internal, thus erosion lubricating grease, reduce the lubrication effect, significantly, this is also our in the work place, The seal of roll head cannot be removed easily.
4) Overload damage
Rolling bearings under the condition of overload, tend to produce abnormal wear and fatigue damage, combined with the practical production, cycle load overload causes of bearing failure is more, take the production channel, for example, when rolling channel steel mill rolling force of a lot larger than round steel, have a greater chance of burning bearing, due to the requirement of rolling technology, with part of the frame is very big, When the bearing is impacted, it works under a large load, resulting in the initiation of fatigue cracks in the part of the rolling body, thus causing fatigue wear and burning of the bearing.
5) Influence of external temperature
Rolling mill bearings are sensitive to external factors in long-term high temperature, high speed and frequent impact. Compound calcium sulfonate base 3# grease is suitable for the lubrication of mechanical bearings with high load, drop point is greater than 300℃, oil content is about 2%, high temperature reversibility does not work 1/4 cone insertion difference is small. When the roller is working, due to various reasons, the cooling water can not play a good cooling role, so that the temperature of the roller itself is too high, and will be transferred to the bearing interior, once the temperature ≥300 degrees, grease will slowly become liquid. A large number of lubricating oil will leak to the outside of the bearing, and the lubrication condition drops sharply, leading to a step by step rise in bearing temperature, and eventually lead to bearing burning loss. Therefore, in the work, the management of rolling mill cooling water is also an indispensable link to reduce the burning loss of bearings.
3. Endnotes
1) The causes of rolling mill bearing burning loss are analyzed. 50%~60% of rolling mills are caused by improper installation, adjustment, use and maintenance.
2) Proper installation, inspection and maintenance of bearings and the formulation of corresponding management and maintenance ledger, so as to reduce the accident rate of rolling mill burning bearings.
3) There are many factors that affect the service life of bearings. Therefore, a comprehensive management system and process procedures should be developed in order to extend the service life of bearings and ensure smooth production.
4) In the next step, we will continue to find and analyze the use and maintenance of thrust (positioning) bearings and transverse adjustment devices, and continue to tackle and improve, to prevent the rolling roll from axial shifting, improve the rolling mill stability, and ensure product quality.
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