Views: 27 Author: guangm Publish Time: 2020-06-16 Origin: https://kns.cnki.net/KCMS/detail/detail.aspx?dbcode=CJFQ&dbname=CJFD2006&filename=DDTL200608008&v=MjI3ODhZZWRwRnk3blZMcklJU25mWXJHNEh0Zk1wNDlGYklSOGVYMUx1eFlTN0RoMVQzcVRyV00xRnJDVVI3cWY=&uid=WEEvREcwS
What's purpose of screen printing the graphite coating on the piston and plunger?
Generally, the anti-friction coating treatment on the piston surface is needed to improve the reliability and life of the engine, it reduces the friction between the piston and the cylinder liner or cylinder block, by tin plating ,coating graphite or molybdenum disulfide, etc.
The function of tin plating is getting smaller and smaller in the pistons of modern high-speed engines and high-power engines, it's basically no longer used while anti-wear coatings mainly use graphite coatings. There are generally two methods forcoating: spraying and screen printing
Spraying graphite is a traditional process method, relatively simple and easy to master. But the pre- and post-process is complicated which leads a poor uniformity of the appearance and thickness of the coating. Also there always a serious coating loss during spraying, 80% according to relevant information). The price of paint is more expensive, it's not conducive to environmental protection and personal safety of operators.
Application of screen printing technology in coating of piston surface
Screen printing graphite coating on piston usually the process: ultrasonic degreasing-cleaning-hot water cleaning-drying-screen printing-curing.
1. Ultrasonic degreasing completely remove the oil pollution on the surface of the piston, makes the surface of the piston clean. Using a special cleaning agent suitable for aluminum alloys or a degreasing solution containing sodium carbonate are both avaiable.
2. Cleaning is mainly to remove the cleaning agent on the surface of the piston.
3. Hot water cleaning, furtherly remove the residual cleaning agent on the surface of the piston, then it is beneficial to the rapid drying
4.Drying, quickly evaporate the water on the surface of the piston to obtain a clean surface, while preventing the cast iron insert ring from rusting.
Ultrasonic degreasing, cleaning, hot water cleaning, drying and other processes are all pre-treatments, which have a great influence on the bonding strength of the graphite coating, and also affect the appearance quality of the coating.
It's the best to use deionized water for cleaning, so after piston dried, there won't be solid impurities and no watermark on the surface. Curing is to dry and solidify the coating, it has a very important influence on the bonding strength and also affects the appearance quality of the coating.
