There is no way to clean the cleaning method, mainly for the cooling oil residual oil attached to the surface of the fastener during cold heading or cutting, and the cleaning of the residual oil on the surface of the fastener after quenching in the heat treatment oil. 1 alkaline water cleaning method The simplest alkaline water cleaning is a direct heating or indirect heating cleaning tank, which is 3% to 10% N2CO3 or NaOH aqueous solution. For self-tapping screws for carburizing or carbonitriding, the intermediate cleaning before tempering is usually carried out with a sodium carbonate solution heated to 50-70 ° C 5% to 10%. Connected mesh belt furnaces fall into this category. Fastener cleaning generally uses a dual method of spraying and immersing. If the effect is better with hot water, the high-pressure airflow is used for drying. The main disadvantage of the alkaline water cleaning method is that the cleaning effect is not very good, especially the blind holes and the groove portion of the fastener are prone to stains and residues. The wastewater generated by the alkaline water cleaning must be neutralized and the waste oil recovered to meet the relevant environmental requirements before being discharged. 2 metal cleaning agent cleaning method In order to overcome the shortcomings of the alkaline water cleaning method and improve the cleaning effect, a special metal cleaning agent can be used at present, the cleaning agent is diluted into a 1% to 3% solution in 40-70 ° C water, and the fastener is soaked in the solution 15 ~ 20 min, then rinsed with hot water, and finally dehydrated with a dehydrator. Can be used in the washing machine. The disadvantage of the metal cleaning agent cleaning method is that it is expensive and has an unpleasant odor. It has a certain corrosive effect on the fastener, and the wastewater pollutes the environment. Therefore, the wastewater must be treated and the waste oil recovered. 3 organic solvent cleaning method It is cleaned with an organic solvent such as trichloroethane or trichloroethylene, and the cleaning effect is good. When the quenched fastener is cleaned by immersion or spraying under normal pressure, the volatilization and splashing of the organic solvent pollute the environment. To this end, a complete set of closed vacuum decompression solvent vacuum cleaning method is used, the vacuum pump is used to discharge the air, and the fastener is contacted with high-density solvent vapor in the absence of air to further improve the cleaning effect, and the solvent and oil are recovered by vacuum distillation. . The solvent content of the recovered oil is reduced from 20% to less than 4%, which is lower than 50 ppm of the environmental sanitation regulations of trichloroethylene. 4 combustion degreasing method Cold-pressed or machined fasteners need to be cleaned of the surface oil before entering the heat treatment process. To this end, the fastener can be heated in a degreasing furnace to 350-400 ° C to vaporize or burn the oil to achieve the purpose of de-oiling the fastener or the effect of surface phosphorus removal. The combustion degreasing method is only suitable for cleaning before heat treatment, and can also clean light, low viscosity and low boiling oil such as cooling oil and anti-rust liquid. After the high-viscosity, high-boiling heavy quenching oil is burned, a large amount of residue and carbon black adhere to the surface of the fastener, failing to clean the object. For fasteners requiring high surface cleaning, such as aviation bolts, automobile engine connecting rod bolts, etc., advanced cleaning techniques such as vacuum or ultrasonic are currently used to replace the commonly used chlorinated hydrocarbons that have a destructive effect on the atmospheric ozone layer. The method can achieve efficient and environmentally friendly cleaning. Editor in charge: Hu Na
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