Case Study: Hydraulic Valves in GJS
High performance, complex geometries, and metallurgical reliability for hydraulic valves made of spheroidal graphite cast iron (GJS)
Hydraulic valves are essential components in high-pressure systems. They regulate oil flow, operate in continuous cycles, and are constantly exposed to dynamic stresses and harsh operating conditions. For this very reason, they must ensure durability, reliability, and long-term stability.
In this context, ductile iron (GJS) proves to be a particularly suitable material, especially when compared to traditional gray iron (GJL), which is typically used to manufacture valves that do not operate under severe conditions. Its combination of strength, toughness, and metallurgical quality makes it ideal for critical components such as hydraulic valves.
The application context
The distributors manufactured by Zanardi Fonderie are used in off-highway machinery, such as agricultural, earthmoving, and forestry equipment, where operating conditions are quite demanding. Their primary function is to manage, direct, and regulate the flow of pressurized oil from the hydraulic pump to the actuators (hydraulic cylinders and motors), according to the machine’s required functions.
In this context, distributors must bear:
- high and fluctuating oil pressures
- shocks and cyclic loads
- temperature fluctuations and constant vibrations
- the need for operational continuity even after prolonged use.
The choice of material is a key factor in the system’s durability, safety, and overall performance.
Why Choose Ductile Iron (GJS)
When mechanical performance exceeding that of the GJL is required
Compared to GJL lamellar cast iron, GJS—typically in pearlitic grades—offers a significantly superior set of properties. It is better able to withstand pressure, absorb shocks, endure repeated cyclic loads, and maintain a more ductile and controlled behavior. All of this helps reduce the risk of failure, even under very severe operating conditions.
Results Achieved
The upgrade delivered a tangible improvement in performance, with specific advantages in mechanical, functional, production, and economic terms.
Resilience under demanding operating conditions
Ductile iron (GJS) in the pearlitic grades absorbs impacts and repeated cyclic loads. It withstands constant temperature fluctuations and maintains its ductile properties, significantly reducing the risk of failure compared to lamellar cast iron.
Design freedom and castability
The material’s castability enables the creation of complex shapes and intricate internal passages for hydraulic distributors. It allows for the integration of geometries that optimize the flow of pressurized oil and reduce the amount of final machining required on the part.
Mechanical resistance to pressure
The component withstands the high and fluctuating pressures typical of off-highway hydraulic systems. It ensures high resistance to mechanical fatigue during continuous operating cycles.
Structural weight optimization
The dimensional stability of the spheroidal microstructure ensures reliable castings even with complex geometries. It optimizes the overall weight of the casting while maintaining its strength.
Lower Total Cost
The longer service life of the valve and the optimization of production processes reduce industrial costs. This component enhances the value and reliability of the entire hydraulic system.
Excellent design flexibility
Another strength of GJS is its ability to produce complex shapes and intricate internal channels, which are typical features of hydraulic distributors. The material’s excellent castability makes it possible to:
- create internal passages optimized for oil flow
- incorporate designs that reduce the need for final finishing
- Ensure clean and uniform oil lines
- optimize weight without compromising on durability
The spheroidal microstructure provides dimensional stability and results in reliable components, even when the geometries are particularly complex.
Example of hydraulic valves made of ductile iron
Zanardi Fonderie’s metallurgical expertise
Zanardi Fonderie’s extensive experience in the production of complex spheroidal graphite castings is a key factor in the success of high-performance applications. Metallurgical testing is, in fact, a central element of the entire production process and involves a thorough assessment of the spheroidisation and uniformity of the material, which are essential for ensuring reliability and long-term durability.
A thorough analysis of casting simulations during the design phase and process control make it possible to minimize potentially critical defects, such as porosity and inclusions.
In addition, targeted surface inspections are conducted, particularly in the interior sections of the ducts, where the quality of the concrete pour is critical to proper operation.
This approach is complemented by direct and ongoing collaboration with the customer, which enables us to translate functional requirements into reliable, industrially viable production solutions. The integration of these capabilities allows us to combine metallurgical quality, high performance, and operational reliability in the component.
The result
Thanks to the use of GJS spheroidal graphite cast iron and the rigorous metallurgical testing developed by Zanardi, the final distributor offers high resistance to pressure and fatigue. The component thus ensures high reliability even under extreme operating conditions. These advantages are complemented by optimized total cost, achieved not only through the component’s longer service life but also through the optimization of production processes.
Conclusions
These application examples demonstrate that ductile iron is an ideal solution for hydraulic valves. The combination of superior mechanical performance, advanced design capabilities, and consistent, controlled metallurgical quality enhances the reliability, functionality, and overall value of the component, thereby contributing to the improvement of the hydraulic system as a whole.
Applications of GJS hydraulic valves
Agriculture and forestry sector
Off-highway machinery
Industrial hydraulics
Case History
Real cases explaining the development of client projects
