Typical Surface Treatment Technology for Piston Ring

Hard Chromium Plating (Cr)

The hard Chromium plating layer has excellent characteristics which combine the original properties of Chromium metal with the advantages of electro-deposits. The main features of hard Chromium plating as follows:

• Extremely high hardness of HmV 800 to 1100.
• Highly melting point of approx. 1800°C
• Good thermal conductivity and corrosive resistance.
• Low friction factor and excellent wear resistance,Such features are very effective in preventing piston ring wear. With the development of this hard Chromium plating,engine performance has been greatly improved. It is applied to piston rings for medium sized engine as well as small sized engines, plus chromium plating which has oil retaining properties is used for high pressure compressors.

Wear resistance of Hard Chromium Plating

The following table shows the results of friction and wear tests on high grade cast iron and hard chromium plating. Gray cast iron was used for the mating material. As shown, it is evident that wear resistance of hard Chromium plating is about 7 to 8 times higher than cast iron.

Main Structual Materials for Piston Ring

Steel
R-SP is a steel selected and improved as material suitable for piston rings. It is used to produce compression rings. It is also used for high-performance oil ring [DIESELVENT-M] for diesel engines. R-SS is easy to form, excellent in spring characteristics and highly resistive to permanent set in thermal fatigue. It is widely used for combination oil ring [RVENT] spacer in various engine versions.

HI-R
HI-R is a high elastic material and it shows a modulus of elasticity of 147 to 167 GPa which is close to steel modulus of elasticity 196 GPa. The reason for this is that the configuration of graphite wear resistance which is top ranked among currently available cast iron types. HI-R is suitable for such applications as automobiles, vessels, construction equipments, aircraft which require high modulus of elasticity and break-resistance.

R-S
R-R is a tough cast iron provided with excellent physical and mechanical properties by a special refining process without addition of any alloying element. It offers adequate elastic modulus and hardness, is easy to break in and is relatively high in shock resistance.

Available Ring Sets

[X Series]
This piston ring features the use of the coil expander installed in the inner surface of the oil ring to enhance conformability to the wall surface of cylinder, ensuring high oil scraping capability. It is extensively used with piston in high performance diesel engines and gasoline engines of passenger cars, buses, trucks and construction vehicles. Another advantages is that it is highly effective in reducing oil loss due to a deformed cylinder.

[M Series]
The use of a steel oil ring makes this piston ring set capable of effectively ensuring optimum oil control over a long period with minimum oil consumption, This type is used with diesel engines in passenger cars, buses, trucks and construction vehicles.

[E Series]
In this piston ring set,the rear plate of the 2nd ring is combined with an expander to achieve a reduction in slap sound.This set is widely used for 2-strike gasoline engines.

[O Series]
This piston ring set is a combination of a top ring with a surface treated outer surface such as chromium plating, a second ring and a coil un-expandable ring. This is the most-common type widely used with 4-cycle gasoline engines and diesel engines in various vehicles ranging from motorcycles to buses and trucks.

[N Series]
This is a piston ring set without an oil ring for 2-strikeengines.Either the top ring only,or both rings have their surfaces treated to ensure long surface life.