Case History: AGI engine base
Engine base made of Austempered Gray Iron (AGI)
Project Context and Objectives
The case describes the technological upgrade project for an automotive engine block made of GJL 250 gray cast iron using austempering heat treatment. Austempering treatment applied to gray cast iron produces Austempered Gray Iron (AGI).
The GJL 250 cast iron component is assembled in the highest series and standard performance models, while the AGI austempered gray cast iron version is used in very high performance car niches.
Indicative image, not related to the actual component due to confidentiality.
Sectors of reference
The AGI engine block guarantees reliability, thermal efficiency, and resistance to mechanical stress, even under harsh operating conditions, in applications in the following sectors:
- Automotive
- Agricultural and off-road
- Nautical
- Industrial
Specifically, the engine block in question is an automotive component designed for four-cylinder internal combustion engines in high-performance cars, with outputs of up to 400 horsepower
Problems solved and benefits
Upgrade without
redesign
Improvement of mechanical performance without the need to redesign or modify the geometry of the component, foundry equipment, or casting process.
Optimized Production Process
The castability of GJL gray cast iron is maintained and the existing dry processing line can continue to be used; CGI, on the other hand, cannot be dry processed.
Superior thermal efficiency
High thermal conductivity and vibration damping capacity, thanks to the ausferritic microstructure with lamellar graphite.
Increase in performance
Significant increase in hardness (+40 HB), tensile strength (+100 MPa), yield strength (+85 MPa), and fatigue strength (+40 MPa)
Cost-effective
Austempering can be easily integrated into existing production lines, with minimal impact on overall costs.
Issues resolved – Requirement
The addition of the heat treatment phase is an effective, low-investment alternative to the use of compacted graphite iron (CGI), also known as vermicular iron. Although CGI offers superior mechanical strength compared to conventional gray iron (GJL), its production process is unstable (castability, complex feeding and attachment techniques) and its machinability is more critical.
For applications intended for large or high-load engines, the paradigm shift towards AGI, also supported by field tests, was driven by the desire to improve mechanical performance without the need for redesign.
The addition of the treatment phase has no implications for geometries, equipment, or production processes: it is therefore a cost-effective strategy that has a minimal impact on total costs.
In addition to being an interesting application aimed at improving the mechanical strength of the base material, the use of austempering treatment also guarantees good workability.
In other words, the aim of the technological upgrade project is to improve performance without having to redesign the engine or change its manufacturing process.
Acquired benefits
The benefits achieved, which concern the optimization of the production process and mechanical characteristics, can be summarized as follows:
- The excellent castability of GJL gray cast iron is maintained.
- Use of the existing dry machining line for GJL, by adapting the tools (CGI, on the other hand, cannot be dry machined)
- Greater hardness, mechanical strength, and wear resistance compared to GJL
- Thermal-physical and acoustic properties comparable to those of GJL
- No changes necessary to the component geometry
- Flexibility of the production process: hardness can be defined by the specific austempering process.
Case History
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