Required Mechanical Properties of Common Rail for Diesel Direct Injection


In the new sophisticated diesel direct injection, the common rail plays an essential role. Exposed continuously to increased pressure and heat, its performance is crucial for the whole system. Selecting materials with the right mechanical properties enables the manufacture of a common rail with high quality and guarantees perfection and reliable performance of the entire diesel engine.

The diesel common rail is hot forged and supports pressure up to 2200 bars. The fuel pressure in the next-generation diesel engines can reach up to 2700 – 2800 bars. Therefore Setforge is about to develop in close collaboration with experienced steel producers new steels for diesel common rails that correspond to modern engine standards.

The required qualities of the steels suitable for the manufacturing of diesel common rail can be categorized in 3 main groups:

1. Excellent Internal Pressure Fatigue Resisting Property

2. Vibration Fatigue Resisting Property

3. Cavitation Resisting Property

Excellent Internal Pressure Fatigue Resisting Property
Internal pressure fatigue is a form of material fatigue (crack initiation, growth, and eventual fracture). It is caused by internal pressure within the common rail. It is important that the material resists internal fatigue excellently since the component endures cyclical rapid loading and unloading of highly pressurized fuel on starts and stops and constant pressurized fuel flow while operating.

Vibration Fatigue Resisting Property
Vibration fatigue is a kind of material fatigue that has been caused by vibrations from various random forces. To consider resistance to vibration fatigue is essential while selecting the right material, since the common rail  as a part of the diesel direct injection is a subject to vibrations.
Cavitation Resisting Property
Cavitation is bubble forming and implosion in a liquid. Bubbles form on low-pressure areas and implode on high-pressure areas upon rapid pressure changes. Repeated implosions on metal surface cause cyclic stress that leads to surface fatigue. The diesel direct injection has both low- and high-pressure fuel flows (low-pressure flow from tank to pressure valve is where bubbles form and high-pressure flow from pressure valve to common rail is where bubbles implode); therefore the cavitation resisting property of the material is very important.

Setforge possesses an excellent expertise in selecting and participating in the development of modern materials with best mechanical properties. Based on the design of the diesel common rail our team provides high-quality manufacturing process combining different forging techniques and tools. Setforge raw material selection guarantees a perfect diesel direct injection performance and endures all possible problems caused by vibrations, cavitation or internal pressure.


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