How many do you know about the essential nine almighties in the bearing industry

How many do you know about the essential nine almighties in the bearing industry

1. Installation of bearing

　　 Whether the bearing is installed correctly or not affects the accuracy, life and performance. Therefore, the design and assembly department must fully study the bearing installation. Hope to install in accordance with operating standards. The work standard items are usually as follows:

　　 (1) Cleaning the bearing and its related parts

　　 (2) Check the size and finishing of related parts

　　 (3) Installation

　　 (4) Inspection after bearing installation

　　（5）Supply lubricant

　　 I hope to open the bearing package just before the installation. General grease lubrication, do not clean, directly filled with grease. Lubricating oil does not need to be cleaned in general. However, the bearings for instruments or high-speed use should be cleaned with clean oil to remove the anti-rust agent coated on the bearings. Bearings with anti-rust agent removed are easy to rust, so they cannot be left alone.

　　Furthermore, bearings that have been sealed with grease can be used directly without cleaning. The installation method of the bearing varies with the bearing structure, fit and conditions. Generally, since most of the shaft rotates, the inner ring needs an interference fit. Cylindrical bore bearings are usually pressed in with a press or hot-fitting method. In the case of a tapered hole, install it directly on the tapered shaft or use a sleeve.

　　When installed on the shell, there is generally a large amount of clearance fit and interference in the outer ring. It is usually pressed in with a press, or there is a shrink fit method for installation after cooling. When dry ice is used as the coolant, the moisture in the air will condense on the surface of the bearing when the shrink fit is installed. Therefore, appropriate anti-rust measures are required.

　　2, bearing material

　　The rings and rolling elements of rolling bearings are subjected to high contact pressure repeatedly while making rolling contact with sliding. The cage is in sliding contact with the two sides of the ring and the rolling element or one side, and bears the tensile and compressive forces on the other. Therefore, the main requirements for the materials and performance of bearing rings, rolling elements and cages are as follows:

　　(1) The required properties of ferrule and rolling element materials: high rolling fatigue strength, high hardness, and high wear resistance;

　　 (2) The required performance of the cage material: good dimensional stability and high mechanical strength.

　　 (3) Good workability is required. Depending on the application, it is also required to have good impact resistance, heat resistance, and corrosion resistance.

　　 Material of ferrule and rolling element

　　 Rings and rolling elements usually use high carbon chromium bearing steel. Most of the bearings use SUJ2 in JIS steel grade. SUJ3 is used for large bearings. The chemical composition of SUJ2 has been standardized as a bearing material in countries around the world. For example: AISL52100 (USA), DIN100Cr6 (West Germany), BS535A99 (UK), etc. are all of the same kind of steel.

　　 When further impact resistance is required, chromium steel, chromium-molybdenum steel, nickel-chromium-molybdenum steel are used as bearing materials, and carburizing and quenching are used to make the steel have a hardened layer from the surface to an appropriate depth. Carburized bearings with proper hardening depth, fine structure, proper hardness of surface and core hardness have better impact resistance than bearings using bearing steel, and the chemical composition of general carburized bearing steel. NSK and DKF have implemented vacuum degassing treatment, so the materials used have high purity, low oxygen content, and good quality.

　　 In turn, proper heat treatment is adopted to significantly increase the rolling fatigue life of the bearing. In addition to the above-mentioned steel grades, high-speed steel with excellent heat resistance and stainless steel with good corrosion resistance are also used for special purposes.

　　 cage material

　　The material of the stamping cage is low carbon steel. Depending on the application, brass plates and stainless steel plates are also used. The material for cutting the cage is made of high-strength brass, carbon steel, and synthetic resin.

　　3. Storage of bearings

　　 The storage of bearings must first fully consider the size and weight of the stored bearings, and secondly, consider the necessary handling space and equipment to ensure that the bearings will not collide during storage and retrieval. Do not place the bearing directly on the ground.

　　 Therefore, it is necessary to configure a proper shelf, and the bottom of the shelf should be 30cm above the ground. In the general packaging state, the rust prevention effect is 13 years depending on the storage environment. In special circumstances that require storage for nearly 10 years, the storage method can be immersed in oil such as turbine oil (as bearing lubricant).

　　 (1) Work to install bearings

　　 There are many ways to install the bearing, and the same work will be done after installation. After the bearing is installed, the outer ring must be obliquely coated with bearing lubricant.

　　A. Application of lubricant

　　 1. For grease lubrication, apply lubrication to cover all the roller surfaces, and restore the position of the outer ring after finishing.

　　2. For oil lubrication, coat all roller surfaces with oil, and restore the position of the outer ring after coating.

　　 B. After coating, cover with plastic film to prevent dust.

　　 (2) Precautions for disassembling the bearing

　　The disassembly of the bearing is carried out when the bearing needs to be replaced due to regular maintenance or abnormal operation. When the bearings need to be replaced frequently during regular maintenance, the reason for the abnormality should be understood when the bearing is disassembled to prevent the abnormality from recurring. At least the following items should be retained.

　　 1. Collect and keep the used lubricant.

　　 2. Keep damaged bearings.

　　 3. Keep records of abnormal events during operation.

　　4. Keep a record of the bearing condition during abnormal operation.

　　4. Maintenance of bearings

　　 In order to make the bearing fully play and maintain its due performance for a long time, it is necessary to do regular maintenance. Through appropriate regular inspections, it is very important to improve productivity and economy to detect faults early and prevent accidents before they occur.

　　 (1) cleaning

　　 When removing the bearing for inspection, first make a record of the appearance with photography or other methods. In addition, confirm the amount of remaining lubricant and sample the lubricant before cleaning the bearing.

　　The cleaning of the bearing is divided into rough washing and fine washing, and a metal grid can be placed at the bottom of the container in use. For rough washing, use a brush to remove grease or adhesions in oil. If you rotate the bearing in oil at this time, be careful that the rolling surface may be damaged by foreign matter. Slowly rotate the bearing in oil during fine washing and proceed carefully. Commonly used cleaning agents are neutral non-water-containing diesel or kerosene, and mild alkaline liquids are sometimes used as needed. But no matter what kind of cleaning agent is used, it must be filtered frequently to keep it clean. After cleaning, immediately apply anti-rust oil or anti-rust grease on the bearing.

　　 (2) Inspection and judgment

　　In order to judge whether the removed bearing can be reused, it is necessary to check its dimensional accuracy, rotation accuracy, internal clearance, mating surface, raceway surface, cage and seal ring. Regarding the inspection results, it can be judged by those who use inertial bearings or are proficient in bearings. Judgment criteria vary according to mechanical performance and importance, inspection cycle, etc. If the following damage occurs, the bearing must not be reused and must be replaced.

　　 5. Adjustment of bearing axial clearance

　　 The axial clearance inside the bearing can be achieved by moving the axial position of the outer ring.

　　1 Adjusting shim method

Fill a set of soft material (soft steel or elastic paper) gaskets between the bearing end cover and the end surface of the bearing seat; when adjusting, first install the bearing end cover without placing the gasket, and tighten the bearing end cover evenly on the same side. Screw, while turning the shaft by hand, until the bearing rolling element is in contact with the outer ring and there is no gap inside the shaft; at this time, measure the gap between the bearing end cover and the end surface of the bearing seat, plus the shaft required by the bearing in normal operation Toward the gap; this is the total thickness of the gasket to be filled, and then fill the prepared gasket between the bearing end cover and the end face of the bearing seat, and tighten the screws after z*.

　　2 Adjusting bolt method

Press the pressure ring on the outer ring of the bearing and pressurize with the adjusting bolt; before the pressure adjustment, first measure the pitch of the adjusting bolt, and then slowly tighten the adjusting bolt until there is no gap in the bearing, and then calculate the adjustment The corresponding rotation angle of the bolt. For example, if the pitch is 1.5mm, the clearance required for the normal operation of the bearing, then the required rotation angle of the adjusting bolt is 3600×0.1535=360; at this time, if the adjusting bolt is reversed 360, the bearing will obtain an axial clearance of 0.5mm , And then fix it with a stop washer.

　　 6. Bearing damage and countermeasures

　　Bearing damage

　　 Generally, if the bearing is used correctly, it can be used until the fatigue life is reached. However, there may be accidents that are prematurely damaged and cannot withstand use. This kind of early damage, as opposed to fatigue life, is the quality limit called failure or accident. It is mostly caused by careless installation, use, and lubrication, foreign matter invaded from the outside, and insufficient research on the thermal effect of the shaft and housing.

　　About the damage state of the bearing

The jamming of the ring and rib of the roller bearing can be considered as the cause. There may be insufficient lubricant, unsuitability, defects in the oil supply and drainage structure, foreign matter intrusion, bearing installation errors, and excessive shaft deflection. These reasons coincide. Therefore, it is difficult to know the real cause of the damage only by investigating bearing damage. However, if you know the bearing's operating machinery, operating conditions, the structure around the bearing, understand the situation before and after the accident, combined with the damage state of the bearing and several reasons, you can prevent similar accidents from happening again.

　　7, bearing form

　　Inch single row deep groove ball bearing: R

　　Inch single row deep groove ball bearing with flange: FR

　　 Metric single row deep groove ball bearing: The symbol is omitted

　　 metric single row deep groove ball bearing with flange: F

　　 Metric single row deep groove ball bearings of specific size: MR

　　Specific size metric single row deep groove ball bearing with flange: MF

　　 Thrust bearing with groove: FM

　　 Trackless thrust bearing: F

　　 Sealing ring. Dust cover

　　 Contact type Teflon seal with retaining ring on both sides: TT

　　 Steel plate dust cover on both sides: ZZ

　　 Contact rubber seals on both sides: 2RS

　　 8. Selection of rolling bearing oil

　　 Spindle bearing lubricants that use rolling bearings are generally considered based on the product of the bearing inner diameter d and the spindle speed n, that is, the speed factor dn, the bearing operating temperature T, and the load P borne by the bearing. The variety of lubricating oil can be selected from Japan Central Oil Chemical (COC) high temperature grease bearing oil, which can be determined according to product variety, working conditions and viscosity grade.

Bearing working temperature -30-0℃, normal load (3MPa) suitable oil viscosity (40℃) 18-32mm2/s, viscosity grade 22, 32; heavy load or shock load (3MPa-20MPa) suitable oil viscosity (40℃) ) 18-50mm2/s, viscosity grade 32, 46.

Bearing operating temperature 0-60℃, speed factor (dn value) below 15000mm.r/min, normal load suitable oil viscosity (40℃) 32-70mm2/s, viscosity grade 32, 46, 68, heavy load or impact load (3MPa-20MPa) Applicable oil viscosity (40℃) 70-192mm2/s, viscosity grade 68, 100, 150;

Speed ​​factor (dn value) 15000-75000mm.r/min, normal load suitable oil viscosity (40℃) 32-50mm2/s, viscosity grade 32, 46, heavy load or impact load (3MPa-20MPa) suitable oil viscosity ( 40℃) 42-90mm2/s, viscosity grade 46, 68, 100;

Speed ​​factor (dn value) 75000-150000mm.r/min, normal load suitable oil viscosity (40℃) 15-32mm2/s, viscosity grade 15, 32, heavy load or impact load (3MPa-20MPa) suitable oil viscosity ( 40℃)32-42mm2/s, viscosity grade 32; speed factor (dn value) 150000-300000mm.r/min, normal load suitable oil viscosity (40℃) 9-12mm2/s, viscosity grade 5, 7, 10, Heavy load or shock load (3MPa-20MPa) is suitable for oil viscosity (40℃) 18-32mm2/s, viscosity grade 15.

Bearing operating temperature 60-100℃, speed factor (dn value) below 15000mm.r/min, normal load suitable oil viscosity 40℃110-192mm2/s (100℃9.3-12.5mm2/s), viscosity grade 150, heavy load Or impact load (3MPa-20MPa), suitable for oil viscosity (40°C) 195-240mm2/s (100°C 15-24mm2/s), viscosity grade 150;

Speed ​​factor (dn value) 15000-75000mm.r/min, normal load suitable for oil viscosity 40℃70-120mm2/s (100℃5.6-9.3mm2/s), viscosity grade 68, 100, heavy load or impact load ( 3MPa-20MPa) suitable oil viscosity (40℃) 110-192mm2/s, viscosity grade 150; speed factor (dn value) 75000-150000mm.r/min, normal load suitable oil viscosity 40℃50-90mm2/s(100℃ 5.6-9.3mm2/s), viscosity grade 46, 68, 100, heavy load or shock load (3MPa-20MPa) suitable for oil viscosity (40℃) 70-120mm2/s, viscosity grade 100.

　　 9. Matters needing attention in measuring bearing radial clearance

　　 (1) As far as possible, use special instrument measurement methods.

　　 (2) The use of hand-pushing measurement requires the measurer to have high measurement skills. The measurement error of this method is relatively large, especially when the clearance is in the edge state, it is easy to cause errors. At this time, the instrument measurement shall prevail.

　　 (3) When measuring with a feeler gauge, the operation should be carried out according to the provisions of the standard, and the method of rolling over the feeler gauge with a roller is not allowed to measure.

　　 (4) During the measurement process, the ball should be ensured to fall into the bottom of the groove, and the closed bearing should be measured before closing. When a loaded instrument is used, the measured value should also deduct the increase in clearance caused by the load.

　　 (5) For multi-row bearings, the clearance of each row is required to be qualified, and the arithmetic average of the clearances of each row is taken as the radial clearance of the bearing.