The piston ring is one of the key parts in the piston system, and the selection of its material is crucial to the performance and service life of the engine. Piston rings need to have excellent wear resistance and elasticity in order to play a good sealing role in the up-and-down movement of the piston and ensure the normal operation of the engine. The main materials of common piston rings include steel, cast iron and ductile iron.
Steel is one of the most commonly used materials for piston rings because of its good moldability, ability to withstand large deformations, exceptional wear resistance, and low cost. Compared to cast iron, steel piston rings have higher tensile strength and wear resistance. These properties make them ideal for use in high-load, high-speed engine environments. The hardness and strength advantages of steel provide better resistance to deformation and breakage aat high temperatures and pressures. Wear resistance can be further enhanced by special treatments such as coating or heat treatment. Steel piston rings are also relatively economical to manufacture compared to ductile iron. Currently, C.T.I. uses 304H steel.
▲Microstructure of Steel
The material cost of cast iron is slightly higher than steel. It has good processability, but it is relatively less abrasion-resistant and requires a proper surface treatment. Although the performance of cast iron piston rings is not as good as that of ductile iron in a high temperature and high pressure environment, it can still meet the basic requirements for ordinary automobile engines. Currently, C.T.I. uses FC20 cast iron.
▲Microstructure of Cast Iron
Ductile iron is recognized as the best choice for piston ring material because of its excellent mechanical properties and wear resistance. Ductile iron has good self-lubrication and resistance to thermal cracking due to the large number of graphite particles. Also, the hardness and tensile strength of this material are much higher than those of ordinary cast iron, and it is more resistant to abrasion in high-temperature and high-pressure environments. However, the manufacturing cost of ductile iron piston rings is usually higher, and the production process is relatively complicated. Currently, C.T.I. uses FCD60 ductile iron. Ductile iron piston rings are widely used in all kinds of internal combustion engines, especially for high-power and high-speed gasoline and diesel engines. They not only provide exquisite sealing performance, but also have a much longer service life than other materials. Even under stringent automotive emission standards, ductile iron piston rings maintain excellent fuel consumption and emission targets. It can be said that this material is currently the best choice for piston rings.
▲Microstructure of Ductile Iron
Among the many choices of piston ring materials, ductile iron is undoubtedly one of the best materials, but the cost is higher. Next is steel, which performs better than cast iron and has a nice cost-effectiveness, but is more likely to be limited by size of raw material. Although the performance of cast iron piston rings is inferior to that of ductile iron and steel, they are still widely used in piston ring parts because there are no size restrictions on raw material and the cost is moderate.
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