Why do bearings rust? How to prevent bearings from rusting?

As we all know, bearings are precision mechanical parts that require high precision and high surface finish, and corrosion will make the bearing lose its original precision and finish, which will directly affect the performance of the bearing, reduce its service life, and even scrap it. In the process of bearing production and processing, if the rust prevention management measures are improper, it will cause a large amount of rust of semi-finished products and finished parts, which will seriously affect the balance connection and the completion of tasks on time. Therefore, bearing anti-rust management is very important. Today, the master will introduce the reasons for bearing rust and the measures to prevent bearing rust.
The main reason for bearing rust

1) In the grinding process, the instantaneous high temperature will make the surface of the workpiece reach a molten state, and the steel surface will chemically react with the oxygen in the air to form an extremely thin (20--30nm) iron oxide film. If it is not completely removed in subsequent processing, even if the bearing is coated with anti-rust oil, the internal corrosion will appear on the surface of the bearing after a period of time.

2) During the fine grinding or super grinding of the bearing, the specified accuracy is not achieved, and pits of a certain depth are formed on the surface. Once the corrosion particles or moisture in the air enter these pits, the corrosion will gradually appear.

3) After the bearing is acid-printed and engraved, if the cleaning is not clean or the neutralization is not thorough, it will cause corrosion.

4) The method of applying anti-rust oil is unreasonable. One is to use a rag soaked with anti-rust oil to roll the bearing on the rag. Sweat on the hands, corrosive substances on the rag and the bearing parts where the anti-rust oil has not been applied will cause corrosion; The second is to stack the bearings together, and then spray the anti-rust oil with a sprayer, and it is difficult for the anti-rust oil to be drenched between the superimposed surfaces of the bearing and the bearing, so that it will slowly corrode in contact with moisture and oxygen in the air for a long time. produced.

5) The influence of humidity. The critical humidity of steel is about 65%, but for many small-scale manufacturers, the production environment humidity is mostly more than 65%, and some even reach 80%, which can easily cause the bearing to rust.

6) When the bearing is washed with water, it will also cause serious corrosion of the bearing if it is not dehydrated or the dehydration is not clean, or it is dried by an air compressor without drying.

7) When the bearing is assembled and inspected, the operator directly touches the bearing parts with his hands, causing the sweat on the hands to stay on the bearing surface, which will cause the outer ring of the bearing to rust.

8) A lot of moisture in the air and corrosive substances with salt blow down on the bearing surface, and the temperature of the product drops due to ventilation to produce "condensation", which will also cause the bearing to rust.

9) The material of the bearing steel does not meet the requirements, such as the high content of non-metallic impurities in the steel (the increase of the sulfur content in the steel reduces the corrosion resistance of the material itself).

Measures to prevent bearing corrosion

1) Anti-rust management between processes

In the process of processing, metals often come into contact with atmospheric environments such as dust, moisture and acid mist, and rust will occur. After heat treatment, the residual salt is not cleaned, the acid cleaning and acid printing liquid cleaning are not completely neutralized, and the demagnetization is not clean. The end of the grinding wheel, iron Chips, sweat, etc. are very easy to cause bearing corrosion. Therefore, to ensure that the workpiece will not be lost during the processing, effective anti-rust measures must be taken for the bearing parts that stay between the processes.

a. Establish a rust-proof warehouse, adopt mechanical spraying method, spray 2-3 times per shift, 10-15 minutes each time, and concentrate rust-proof treatment on bearing parts.

b. Regularly clean all kinds of anti-rust equipment, prepare anti-rust liquid, cleaning liquid and cooling water in strict accordance with the process, regularly test, adjust, and replace on schedule.

c. Bearing parts that need to be inspected and ground must be demagnetized first, cleaned with cleaning fluid, and then put into storage to prevent rust.

d. After the bearing parts are pickled, they must be cleaned, neutralized completely, and then treated with anti-rust water.

e. It is forbidden to use cooling water, cleaning liquid to wash hands, wash cloths, etc., to ensure the cleanliness and performance of the liquid used, and to prolong the life of the liquid used.

f. Do a good job in civilized production, ensure environmental sanitation, and eliminate hidden dangers of rust.

2) Anti-rust management of finished bearings

The finished bearing is sealed and packaged after being coated with anti-rust oil, which can avoid being affected by the atmospheric environment during storage and transportation, resulting in rust and mildew, which will affect the performance.

a. The finished bearings are mechanically sprayed with kerosene twice, mechanically sprayed with rust-proof and lubricating dual-purpose oil, and packed with polyethylene seals.

b. Before kerosene spraying and anti-rust lubricating dual-purpose oil spraying, filter the filter element that meets the process requirements to ensure the cleanliness of the finished bearing. The oil tank and the machine tool are thoroughly cleaned once a month.

c. When inspectors and assemblers touch finished parts and bearings, they need to apply liquid gloves to avoid rust caused by hand sweat.

d. The finished bearing should be handled with care during transportation and storage to avoid damage to the package.

e. Assembly room and finished bearing storage room should be dry, clean and free of pollution sources.

3) Method of anti-rust oil

a. Immersion method. Some small items are soaked in anti-rust grease, so that a layer of anti-rust grease is adhered to the surface. Oil film thickness can be achieved by controlling the temperature or viscosity of the anti-rust grease.

b. Brushing method. It is used for outdoor construction equipment or special-shaped products that are not suitable for immersion or spraying. When brushing, pay attention not only to avoid accumulation, but also to prevent leakage.

c. Spray method. Some large rust preventives cannot be oiled by immersion method. Generally, the compressed air with a pressure of about 0.7Mpa is used for spraying in a clean air place. The spray method is suitable for solvent-diluted anti-rust oil or thin-layer anti-rust oil, but perfect fire protection and labor protection measures must be adopted.