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Why use vermicular graphite alloy cast-iron to make piston rings?

At present, the big, medium and small rings are widely applied throughout the world. Including, flake graphite alloy cast-iron, vermicular graphite alloy cast-iron and spherical graphite alloy cast-iron.

Following are main performance indicators of such three materials.

No.

Performance Indicator

Flake Graphite Alloy Cast-iron

Vermicular Graphite Alloy Cast-iron

Spherical Graphite Alloy Cast-iron

1

Hardness

HRB95-108  HB200-300

HRB98-110  HB230-300

HRB100-110

2

Bending Strengthδw:N/mm2

400

600

1100

3

Modulus of elasticity: N/mm2

85000-110000

130000

150000

4

Thermal (tangential elasticity disappearance rate)

15%

8%

8%

5

Wear resistance and sorting by sizes

Second

First

Third

6

Thermal conductivity
λCaL/cm•s℃

First 
0.10-0.12

Second
0.09-0.10

Third
0.07-0.08

7

Linear expansion coefficient (within range of 20°~300℃ mm/mm℃

aP(11.0-12.0)×10-6

aR12×10-6

aQ12.3×10-6

8

Anti-fusion wear capacity(cylinder scoring) and sorting by sizes

First

Second

Third

9

Corrosion resistance and sorting by sizes

Third

Second

First

10

Fatigue strength δ-1 and sorting by sizes

Third

Second

First

11

Impact toughness and sorting by sizes ak:J/cm2 or kg-m/cm2

aP-K  Third

aR-K  Second

aQ-K  First


From the above 11 indicators, the eight performance indicators of vermicular graphite alloy cast-iron are all superior over the flake graphite alloy cast-iron, including:
•Hardness
•Bending Strength
•Modulus of elasticity
•Wear resistance
•Thermal (tangential elasticity disappearance rate)
•Corrosion resistance
•Fatigue strength δ-1 
•Impact toughness
 
And other six performance indicators are superior over the spherical graphite alloy cast-iron,including:
•Hardness
•Linear expansion coefficient
•Thermal (tangential elasticity disappearance rate)
•Wear resistance 
•Thermal conductivity
•Anti-fusion wear capacity
 
In addition,the vermicular cast-iron rings have been used for many years as the first gas rings in the high-speed or high horsepower diesel engines and proven that they are safe and reliable, the vermicular cast-iron rings have a good comprehensive application performance. 
So it is the best option to use vermicular graphite alloy cast-iron as the first gas ring material in the high-speed or high horsepower marine diesel engines.
 
The vermicular graphite alloy cast-iron is a sheet-like structure, similar to the tip of the bamboo leaf is round, the pieces are interlocked, the three-dimensional structure, the internal graphite forms a natural oil storage passage, so the product has very good flexibility, which is N times that of the gray cast iron.
The use of vermicular graphite alloy cast-iron in the first gas ring is a major feature of our company. We use single-piece casting process and barrel casting process; small batch and multi-batch production; complete model; fast delivery; coverable cylinder diameter is φ150~φ1000mm;  service life is up to 20,000 hours, about 2~3 years.

We use electroplating, composite plating and phosphating for heat treatment.

From the four aspects of hardness, elasticity, light transmission, and geometrical dimensions, all are tested.

We have the first CNC internal and external circular elliptical copying lathe, which can produce various types of piston rings according to user's actual sample or design drawings.
 
At present, we are the only company that uses vermicular graphite alloy cast-iron as the first gas ring material in the high-speed or high horsepower marine diesel engines in China. Our goal is to become an OE supplier for two-stroke low-speed marine piston ring.


Changsha HAOCHANG Machinery Equipment Co.,Ltd

www.hc-enginepart.com