Do you know the control points of FAG bearing heat treatment process?
Bearing incoming material requirements and pre-cleaning
The machined parts should firstly ensure that no iron filings remain on the surface of the ferrule, and secondly, the cleanliness of the surface of the ferrule should be ensured, and there should be no attachments such as oil and dirt.
In actual production, the cleanliness of the surface of machined parts cannot fully meet the requirements of heat treatment, so it is necessary to clean before heat treatment. Before cleaning, you should wash off the oil stains on the surface of the ferrule, and regularly check the concentration and temperature of the cleaning fluid. The appropriate temperature and concentration are helpful to cleaning the stains such as anti-rust oil.
The purity of the atmosphere in the bearing furnace
Atmosphere into the furnace
The atmosphere introduced into the furnace is liquid, so the water content of the liquid gas should be checked regularly; the water vapor in the propane cylinder should be drained regularly; the water content in the protective gas and enriched gas should be checked regularly.
Oil fume from bearing oil groove
Most mesh belt oil bath furnaces will be equipped with oil curtains and other similar functional devices at the blanking port, mainly to reduce the oil fume entering the furnace, so the adjustment of the oil curtain is very important, and the appropriate adjustment position can block 70 At the same time, there should be a burning port of furnace atmosphere at the junction of the quenching heating furnace and the oil tank, so that the combustible gas in the furnace can be burned and discharged.
Regular cleaning of the methanol drip port is beneficial to balance the atmosphere in the furnace. At the same time, three factors should be paid attention to: 1) The water content of methanol, according to the regulations of GB 338-2011 "Industrial Methanol", the water content of methanol is not more than 0.2%; 2 ) Regularly clean the carbon black of the methanol drip port to prevent clogging; 3) The methanol cracking must be sufficient.
Selection of quenching oil
Quenching oil consists of two parts: base oil and additives. At present, bright quenching oil is mostly used in ferrules. Additives have been added to the oil to increase the smoothness of the product. Without affecting the cooling rate, the flash point temperature of the quenching oil should be increased as much as possible when the quenching oil is proportioned, so as to prevent the generated fumes from entering the furnace and affecting the finish of the ferrule.
Maintenance of quenching oil
As the quenching oil is used, more carbon black and impurities are produced. These impurities will adhere to the surface of the ferrule and make the surface black. Therefore, the oil must be monitored regularly. The increase in viscosity in the monitoring indicators is generally not more than 20% of the new oil; the increase in acid value is generally not more than 50% of the new oil; with the use of quenching oil, its flash point will gradually decrease, and the use temperature should be lower than the flash point At least 70 ℃.
In the process of using quenching oil, its corresponding viscosity, acid value, and flash point will change. It is best to establish a trend table of these characteristic values and confirm whether the quenching oil meets the requirements of use through continuous tracking. In addition, avoid stirring on the surface where the quenching oil is in contact with air to reduce oil oxidation.
Cleaning after bearing quenching
The post-cleaning is mainly to clean the quenching oil and reduce the retained austenite. The temperature of the hot cleaning has a significant impact on the cleaning effect. The purpose of the cold cleaning fan and the spray nozzle adjustment is to ensure that the water on the surface of the ferrule can be blown off and reduce Water vapor entering the tempering furnace.
In order to prevent rust, an anti-rust agent is generally added to the cold cleaning solution, and the mass fraction of the anti-rust agent is generally 5% to 8% (the range of different anti-rust agents is different). Too high mass fraction will produce mottling on the surface of the ferrule; too low mass fraction can not achieve the purpose of rust prevention.
Burning oil in the tempering furnace
The purpose of oil burning is to reduce the oil and water vapor in the furnace and on the furnace wall through high temperature, and to reduce the probability of blue appearance of the workpiece during tempering. The oil burning temperature of the tempering furnace is set at 300 ℃, and the time is usually about 4 hours.