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1 Introduction Some large-scale electric fan motor manufacturers in Guangdong Province have such a situation; a batch of motor assemblies have not had abnormal appearances during the test operation before leaving the factory; they have passed the factory inspection and passed the qualified specifications; the packaging is shipped. The products are shipped to the province. Outside; some even exported to the Middle East; but when the merchants received the goods inspection; found that the motor transformation noise increased abnormally; after the motor was dismantled, the motor bearing was found to be severely corroded; except for the inner diameter and the end surface, there was corrosion; the primary corrosion position was in the steel ball and The touch of the raceway; although the rusting procedures are different; but it affects the normal operation of the motor; the merchant returns it. This kind of incident not only affects the reputation of the motor factory; it also hinders the normal operation of the motor factory. /*250*250 was created on 2017/12/25*/ var cpro_id = 'u3171089';
The motor manufacturer believes that there are problems in bearing quality and anti-rust disposal produced by the bearing factory; they find our bearing product quality inspection station; need to check the quality of the bearing; and help them deal with the problem of motor bearing rust.
2 Motor bearing sample corrosion characteristics through the production process of several motor manufacturers, the production environment, the selected insulation paint composition, smooth grease composition, installation process, packaging materials, warehouse storage and related motor parts and bearing production plant production And the knowledge of the sale and the on-site inquiry; found that the rust event has the following characteristics:
(1) The primary attack is on household appliances and office machinery such as power-on fans and cold-fan motors; the power of the motors used in these machines is mostly several watts to hundreds of watts; and it is basically a fully enclosed small-sized motor.
(2) The abnormal single motor installation package was not found during the trial operation of the product; after the storage for several months, the noise increased appearance. After the motor was disassembled, the noise was found to be caused by the internal corrosion of the bearing.
(3) The rust of the motor bearing is in the production process or in the warehouse storage time; it is just the high temperature and humidity in the annual March and April.
(4) The bearings required by the motor factory are usually purchased directly from the bearing factory; the motor factory buys back the bearing that has been rust-proofed by the bearing factory; writes the smooth grease by itself; and then installs it on the rotor of the motor. Most of the smooth grease used for the bearing is Adding additives to lithium-based oils; using solvent-based paints is prone to paint rust.
(5) The inside of the bearing is sometimes more severe than the external corrosion; this rust is related to the smooth grease type and relative humidity; the ester oil is smooth grease in the medium humidity (70% RH); the smooth grease is easy to rust, if it is Corrosion caused by moisture; the surface is simply rusted outside the bearing without smooth grease.
(6) Smooth grease with a special paint odor; due to the smooth fat attack.
(7) The corrosion of the bearing has significant directionality; that is, the side of the bearing facing the rotor side of the motor is more rusted; inside the bearing; the raceway on the side of the rotor and the retainer are more rusted.
3 Analysis of motor bearing corrosion
3.1 Corrosion principle The cause of the rust of the motor bearing is very messy; it can be the bearing anti-rust treatment is not good; it can also be the corrosion caused by moisture; and the corrosion caused by the paint mist. It and the variety of insulating paint, bearing pre Filling the smooth grease, the treatment method of the motor paint and the storage environment of the motor have close contact. Through the inspection and analysis of the samples of the rusted motor bearings, it is determined that the corrosion of the motor bearing is announced by the stator wire package insulation paint inside the motor. The corrosive acid component is absorbed by the smooth grease together with the moisture; it is formed by the failure of the smooth grease enthalpy; especially in the steel ball and raceway touch orientation; the rust is more severe.
There are four main types of acid components announced by most motor manufacturers:
1 low-molecular lacquer acid component (anhydrous o- and terephthalic acid; anhydrous maleic acid; trans-butenedioic acid) without repercussions.
2 The acid component formed when the paint is cured (when changing the phenolic lacquer; changing from formaldehyde to formic acid).
3 primary fatty acids (formic acid, acetic acid) produced by heat or oxidative differentiation.
4 The acid component formed after the lacquer cured material is hydrolyzed. The primary acid component of the varnish is the formic acid; the amount of formic acid is closely related to the degree of rust attack. The smooth fat adsorbs the acidic component announced by the lacquer; Inducing smooth grease enthalpy; and this acidic component promotes the hydrolysis of oil; the result is an increase in the concentration of acidic components; causing bearing corrosion.
Smooth grease operation principle; the use of grease layer to separate the steel ball from the surface raceway; the viscosity characteristics of the grease; the steel ball and the raceway appearance; the metal interface separating the steel ball and the surface raceway; Wear and protect the metal from air and moisture; reduce oscillation and noise; make the bearing change smoothly. But after the smooth grease is changed, the viscosity will change; the oil film will break through; the separation function and adhesion characteristics of the smooth grease will be The result of such an attack; the first is to make the acidic component of the insulating varnish directly oxidize the metal appearance; cause the bearing to rust. The second is to form a steel ball and the surface raceway straight touch; when the rotation occurs, the wear occurs; then the noise is increased .
3.2 Operating elements of corrosion (1) The insulating paint used by the motor factory is 1032 melamine acid impregnated insulating varnish; this type of lacquer is made of oil modified alkyd resin and butanol modified melamine resin and organic solvent. Cheng. Because it is rich in organic solvent; in the case of improper use; the bearing is simple and rusty.
(2) After the coil is immersed in paint, it is not dry and boring; the oxidizing gas rich in acid component in the paint gradually releases into the bearing; especially when the relative humidity is 70% to 90%; it will cause smooth grease enthalpy; bearing rust .
(3) The rule of the coil dipping process has a boring temperature of 120-130 ° C; the working time is 180 min; in actual operation; if the drying temperature is lower than 130 ° C; the working time is less than 180 min; the oxidizing gas containing the acid component is not Will be fully announced.
4 Disposal measures should prevent paint rust; it is necessary to improve the bearing's own rust resistance. The bearing information is usually bearing steel; the anti-rust treatment method usually uses anti-rust oil inside the bearing; the bearing after anti-rust treatment The motor factory participates in the smooth grease by itself. However, if the anti-rust oil is applied too thickly, it will reduce the smoothing function. Although it pays attention to improving the anti-rust function of the smooth grease; it has a certain effect; but the most useful method is still to change the paint. ingredient.
Because the paint will attack harmful acid gases; of course, it will cause bearing rust; the detailed disposal method is:
(1) Try to use solvent-free paint.
(2) If available; use an impregnating lacquer that does not contain oxidizing components; such as Epoxy-urethane-based or Epoxy-based impregnating varnish.
(3) When using melamine acid impregnating varnish; the curing temperature and curing time should be adjusted; the curing temperature is slightly higher than 130 ° C (such as 135 ° C) and the curing time is greater than 180 min; and it is necessary to strictly implement the process; In the high temperature and wet period; due to the concept of rust prevention; the paint of the paint factory in the sample of the boring (curing) moment; not necessarily sufficient; the motor has a detailed connotation shape.
(4) Select a paint that does not contain evaporating acid.
(5) Select a paint with good hydrolysis resistance.
(6) Try to use mineral oil bearing smooth grease.
(7) When the motor factory writes the smooth grease by itself; in order to prevent the water vapor and dust in the air from entering the bearing, the noise and other rusting elements can be formed; the smooth grease container should be sealed; even in the case of grease injection. And the amount of grease should be determined according to the specifications; if the 6202 bearing is used; the reference value is in the range of 0. 60 ~ 0. 80g; the grease filling process should be kept clean; boring.
(8) Use plastic film packaging with micro-holes; make the motor must be ventilated before it is used. When it is sealed with plastic film, the paint gas will remain in the bearing; the water will dew; it should be prevented.
(9) Smooth grease can be transformed under the influence of high temperature when the motor cover is sprayed or painted.
(10) Negotiate with the bearing manufacturer; use the more useful rust inhibitor when the bearing is produced.
(11) In order to completely dispose of the paint rust; it can be considered by the motor production plant, the bearing production plant and the paint production unit to participate in the discussion; to summarize the talents of all aspects; to deal with the corrosion of the bearing.
5 Conclusion We have now provided these profiling conclusions to the motor manufacturers; they have confirmed their analysis; they have improved in production and technology; they have achieved good results.
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Motor bearing corrosion analysis and disposal methods
Source: China Bearing Network Time: 2013-07-14