Casting of Combustion Engine Pistons Before and Now on the Example of FM Gorzyce

From Manual Pouring to Robotic Precision: 50 Years of Piston Casting Technology Evolution

This technical summary is based on the academic paper "Casting of Combustion Engine Pistons Before and Now on the Example of FM Gorzyce" by M. Czerepak and J. Piątkowski, published in ARCHIVES of FOUNDRY ENGINEERING (2023).

Keywords

• Primary Keyword: Piston Casting Technology
• Secondary Keywords: Combustion Engine Pistons, Al-Si Alloy Casting, Permanent Mould Casting, Piston Surface Treatment, Federal-Mogul Gorzyce, Silumin Pistons

Executive Summary

• The Challenge: Modern combustion engines demand pistons that can withstand higher thermo-mechanical loads while reducing fuel consumption and emissions.
• The Method: The paper analyzes the 50-year evolution of permanent mould casting processes and piston construction at the FM Gorzyce plant.
• The Key Breakthrough: The transition from manual, single-mould machines to fully automated casting stations with robotic pouring and complex, multi-circuit cooling systems has dramatically improved consistency and efficiency.
• The Bottom Line: Advanced piston performance is achieved not just through superior casting processes but also through sophisticated design features like integrated cooling channels, reinforcing ring inserts, and specialized surface treatments.

The Challenge: Why This Research Matters for HPDC Professionals

For decades, the requirements for combustion engine pistons have relentlessly increased. The push for lighter vehicles, higher engine speeds, and lower emissions has led to a surge in working chamber pressures and temperatures. These extreme conditions place immense stress on the piston, the very heart of the engine.

This paper chronicles the journey of a single plant, Federal-Mogul Gorzyce, as it adapted its piston casting technology over 50 years to meet these escalating demands. Initially, pistons were produced via manual gravity casting into simple, single permanent moulds. This method, while functional for its time, faced limitations in consistency, cycle time, and the ability to produce the complex geometries required by modern, high-efficiency engines. The research provides a clear roadmap of the technological leaps required to move from basic castings to high-performance, multi-material components.

The Approach: Unpacking the Methodology

The study presents a historical comparison of piston manufacturing, contrasting the methods of the 1970s-1990s with today's state-of-the-art processes.

The "Before" Method:
- Machines: Simple, single-chamber permanent mould casting machines.
- Process: Manual pouring of liquid metal (mainly AlSi12 alloy) using casting ladles.
- Moulds: Consisted of a main core, pin cores, die cast blocks, and a top core, with simple cooling systems focused only on the main core. This led to non-uniform crystallization rates.
- Pistons: The resulting pistons were massive, with simple flat crowns and no additional integrated components or specialized surface coatings.

The "Now" Method:
- Machines: Fully automated, multi-station casting cells featuring double permanent moulds.
- Process: Casting robots perform precise dosing of the liquid alloy, placement of inserts (like salt cores and ring inserts), and unloading of finished casts.
- Moulds: Modern moulds are equipped with complex cooling systems, featuring up to 8 circuits with numerically controlled electrovalves. This ensures uniform, rapid crystallization and optimal process efficiency.
- Pistons: Today's pistons are lighter and feature complex designs, including shaped crowns for better combustion, internal cooling channels, and reinforcing ring inserts.

This evolution from a manual, single-piece flow to a fully automated, high-volume process highlights the critical role of process control and thermal management in modern casting.

The Breakthrough: Key Findings & Data

The paper highlights several critical advancements in piston casting technology that have enabled massive leaps in performance and production volume.

Finding 1: Automation and Advanced Cooling Revolutionized Production

The most significant process change was the move to fully automated casting stations. As shown in Figure 5, these stations use robots for pouring and handling, synchronized with power hydraulics that operate the moulds. This automation, coupled with the advanced cooling systems described in Figure 6, drastically improved the process. The alloy cooling time for a piston was reduced from approximately 60 seconds in the old process to about 13 seconds or less. This unification of the crystallization process not only improved casting quality but also massively increased production capacity, as illustrated by the production growth shown in Figure 13.

Finding 2: Piston Design Evolved from Simple Blocks to Complex Components

Modern pistons bear little resemblance to their predecessors. To handle higher thermal loads and improve engine efficiency, piston construction has become far more sophisticated.
- Cooling Channels: Salt cores are now placed in the mould (Figure 10) to create intricate internal cooling channels within the piston head. During engine operation, oil circulates through these channels, significantly lowering the temperature of the piston crown and top ring, thereby increasing durability.
- "Alfin" Ring Inserts: To combat wear in the top ring groove—the most thermally loaded area—austenitic cast iron ring inserts are now cast into the aluminum piston. These inserts undergo a process called "alfinating," where they are briefly submerged in an Al-Si alloy to create a diffusive layer, ensuring a strong metallurgical bond with the piston casting.

Finding 3: Surface Treatments are Crucial for Performance and Longevity

The final performance of a piston is heavily dependent on advanced surface treatments applied after machining. The paper details several key processes:
- Phosphatizing: An aluminum piston is treated to create a micro-porous conversion layer (Figure 11b), which improves corrosion resistance and prepares the surface for graphite coating.
- Graphite Coating: A special resin-based graphite paste is screen-printed onto the piston skirt (Figure 12). This layer, typically 5-15 µm thick, reduces friction, improves oil retention, and protects the piston from seizing during the critical engine break-in period.
- Anodizing & Plating: Other treatments like anodizing create a hard Al2O3 layer in the ring grooves for wear resistance, while chromium plating is used on ring surfaces to increase hardness and reduce friction.

Practical Implications for R&D and Operations

While this study focuses on permanent mould casting, its findings offer valuable insights for professionals across the entire die casting industry, including HPDC.

• For Process Engineers: This study underscores that precise, multi-zone thermal management is paramount for achieving consistent mechanical properties and short cycle times. The move from simple, single-point cooling to complex, numerically controlled circuits suggests that investing in advanced mould cooling technology yields significant returns in both quality and productivity.
• For Quality Control Teams: The data on various surface treatments (phosphatizing, graphite coating, anodizing) highlights that post-casting modifications are no longer an afterthought but an integral part of component performance. The effectiveness of these layers, as detailed in the paper, could inform new quality inspection criteria for mission-critical components.
• For Design Engineers: The findings on integrated components, such as the use of salt cores to create internal cooling passages and "alfin" inserts for localized wear resistance, demonstrate the immense potential of designing multi-material components. This approach allows for optimizing performance in specific areas without compromising the entire casting's properties, a valuable concept for complex HPDC parts.

Paper Details

Casting of Combustion Engine Pistons Before and Now on the Example of FM Gorzyce

1. Overview:

• Title: Casting of Combustion Engine Pistons Before and Now on the Example of FM Gorzyce
• Author: M. Czerepak, J. Piątkowski
• Year of publication: 2023
• Journal/academic society of publication: ARCHIVES of FOUNDRY ENGINEERING, Volume 2023, Issue 2/2023
• Keywords: Casting, Silumins, Pistons, Permanent moulding casting machines, Surface treatment

2. Abstract:

The article discusses the most important changes in the construction of permanent mould casting machines, as well as the method of casting engine pistons and their construction on the example of Federal-Mogul (FM) Gorzyce. The system of automatic cooling of the presently used permanent mould casting machines coupled with robots which pour the liquid alloy ensures uniform crystallization of the pistons and optimal efficiency of the casting process. As a result of the necessity to improve the engine efficiency and thus reduce the fuel consumption and harmful substance emission, the construction of the pistons has changed as well. The piston castings, which are produced by gravity casting for metal moulds, have undergone a diametric transformation. Typical piston designs for gasoline and Diesel engines are shown together with the most important parts of the piston, the crown (combustion chamber) and the guide part (skirt). Depending on the type of engine, the present pistons characterize in differently shaped crown, a slimmed internal construction as well as component participation (cooling channels and ring inserts), and the piston skirts undergo surface treatment procedures.

3. Introduction:

The requirements set for combustion engine pistons have been systematically rising in the recent years. This mainly refers to increased thermo-mechanical loads as well as low combustion gas emission and fuel consumption. The need for a reduced car mass and high rotational engine speed have caused an increase of the mean and maximal working chamber pressures and inertial forces. These expectations can be fulfilled through e.g. different solutions realized inside the engine. These include increasing values of temperature and pressure in the cylinders, which set the highest requirements for the heart of the combustion engine, i.e. the piston. The paper traces the history of piston production from WSK (Transport Equipment Production Plant) in the 1970s to its acquisition by Federal-Mogul Powertrain (now Tenneco) in 2001, detailing the evolution of the casting process.

4. Summary of the study:

Background of the research topic:

The study is set against the backdrop of rising demands on combustion engine pistons, driven by the need for greater engine efficiency, lower fuel consumption, and reduced emissions. This has necessitated significant advancements in both the materials and manufacturing processes for pistons.

Status of previous research:

The paper positions itself as a historical and comparative analysis of a specific industrial case (the FM Gorzyce plant). It builds upon the general knowledge of piston design, silumin alloys, and casting processes by documenting the practical evolution of these technologies over a 50-year period.

Purpose of the study:

The aim of the study was to detail the main changes in the construction of permanent mould casting machines, the cooling systems, and the construction of silumin pistons for Diesel and gasoline engines over five decades at the Gorzyce plant.

Core study:

The core of the study compares the "old" method of manual, gravity-fed casting in single moulds with simple cooling to the "new" method of fully automated casting cells with robots, double moulds, complex multi-circuit cooling, and the integration of components like salt cores and ring inserts. It also details the evolution of piston design and the various surface treatments applied to modern pistons to enhance their performance and durability.

5. Research Methodology

Research Design:

The research is a comparative case study, analyzing the technological evolution within a single production facility (Federal-Mogul Gorzyce). It contrasts the machinery, processes, and products from two distinct eras: the 1970s-1990s and the present day.

Data Collection and Analysis Methods:

The data is derived from company technical materials, including historical and current process documentation, photographs of machinery and products, and production data. The analysis involves describing and comparing the changes in casting machine construction, mould design, cooling systems, piston geometry, and post-casting treatments.

Research Topics and Scope:

The scope covers the permanent mould casting of silumin engine pistons. Key topics include:
- Changes in casting machine and permanent mould construction.
- Modernization of mould cooling systems.
- Evolution in piston construction for Diesel and gasoline engines, including the use of ring inserts and salt cores.
- Application of various surface treatments like phosphatizing, graphite coating, tinning, and anodizing.

6. Key Results:

Key Results:

• The evolution from manual, single-mould casting machines to fully automated casting stations with robots and double permanent moulds.
• Modernization of mould cooling from a single-core system to complex, 8-circuit systems with numerical control, ensuring uniform crystallization.
• A drastic reduction in piston crystallization time from ~60 seconds to ~13 seconds, leading to a significant increase in process efficiency and production volume.
• Significant changes in piston construction, including complex crown shapes, slimmed internal structures, and the integration of cooling channels (via salt cores) and wear-resistant ring inserts ("alfin" inserts).
• The widespread adoption of advanced surface treatments (graphite coating, phosphatizing, anodizing, etc.) to reduce friction, improve wear resistance, and enhance overall piston durability.

Figure Name List:

• Fig. 1. Old method of casting pistons: a) manual casting; b) single permanent mould casting machine [7]
• Fig. 2. Permanent mould casting machine for casting single pistons [8]
• Fig. 3. Casts of an previous gasoline engine piston with diameter Ø 90 mm; a) after lowering the permanent mould casting machine; b) simply flat piston crown [7]
• Fig. 4. Cast of an old Diesel engine piston with a) diameter Ø 110 mm; b) piston casting after cutting off ingate system and riser [7]
• Fig. 5. Automatized station for casting piston MFGD (Multi Functional Gasoline Diesel) [7]
• Fig. 6. Model of a modern double permanent mould for piston casting (Gasoline) [7]
• Fig. 7. Exemplary pistons for engines with direct ejection: a-c) side view; d-f) piston head surface [7]
• Fig. 8. Exemplary pistons for Light Vehicles engines: a-c) side view; d-f) piston crown surface [7]
• Fig. 9. Internal construction of the present pistons: a-c) pistons from Figure 7; d-f) pistons from Figure 8 [7]
• Fig. 10. Modern pistons with a ring insert and a salt core for: a) a Diesel engine, b) a gasoline engine [7]
• Fig. 11. Pistons for a Diesel engine: a) aluminium before phosphatizing; b) aluminium after phosphatizing; c) steel before manganese phosphatizing; d) steel after manganese phosphatizing [7]
• Fig. 12. Piston skirt after graphite covering: a) for a Diesel engine; b) for a gasoline engine [7]
• Fig. 13. Piston production at Federal-Mogul 2006 - 2021 [7]

7. Conclusion:

The current trends in combustion engine piston construction aim to increase cost-effectiveness and eco-friendliness by improving overall engine efficiency. The paper concludes that achieving this requires a multi-faceted approach. The evolution in casting technology—specifically automation and advanced thermal management—has enabled the production of more complex, lightweight, and durable pistons. Features like cooling channels and alfinated ring inserts are now critical for managing the high temperatures and pressures in modern engines. These advancements have lowered piston crown temperatures by 25-30°C compared to older designs, significantly prolonging durability. Furthermore, advanced production technologies, like local laser remelting of combustion chamber edges, are used to create fine-grained structures that resist cracking under extreme thermal loads.

8. References:

• [1] Pietrowski, S. (2001). Silumines. Łodź: Publishing University of Technology. (in Polish).
• [2] Ranjith Kumar, P., Chandrasekaaran, K. & Kannan, TTM. (2021). Investigation and Analysis of Engine Piston Rod Material. Automotive Material. London: LAP Lambert.
• [3] Rowe, J. (2021). Advanced Materials in Automotive Engineering. Woodhead Publishing.
• [4] Kammer, C. (2011). Aluminium Handbook. Vol. 1: Fundamentals and Materials. Beuth Verlag GmbH.
• [5] Manasijevic, S. (2012). Aluminum Piston Alloys. Radiša, R. (Ed.). Serbia: LOLA Institute Belgrade.
• [6] Oppenheim, A.K. (2004). Combustion in Piston Engines. Technology, Evolution and Control. Springer.
• [7] Federal-Mogul Gorzyce. Company own technical materials, Gorzyce 2022. Retrieved October 29, 2022 from https://www.fmgorzyce.pl/ (in Polish).
• [8] Pater, Z. (2014). Basics of metallurgy and foundry. Lublin.
• [9] Pietrowski, S. & Szymczak, T. (2006). The influence of selected factors on the cnstruction of the alfined layer on iron alloys. Archives of Foundry. 6(19), 251-266. (in Polish). ISSN 1642-5308.
• [10] Pietrowski, S. (2001). Structure of alifinishing layer on the gray cast iron. Archives of Foundry. 4(11), 95-104. (in Polish). ISSN 1642-5308.
• [11] Piątkowski, J. & Czerepak, M. (2020). The crystallization of the AlSi9 alloy designed for the alfin processing of ring supports in engine piston. Archives of Foundry Engineering. 20(2), 65-70. DOI: 10.24425/afe.2020.131304.
• [12] Crolla, D.A. (2009). Automotive engineering. powertrain, chassis system and vehicle body. United States of America: Butterworth-Heinemann.
• [13] Wróblewski, E. (2019). The influence of microgeometry of the piston lateral surface on the mechanical efficiency of a combustion engine. Unpublished doctoral dissertation, University of Technology, Poznań. (in Polish).
• [14] Zając, P., Kołodziejczyk, L.M. (2001). Internal combustion engines. Warszawa: WSP. (in Polish).
• [15] Iskra, A. & Kałużny, J. (2000). Effect of the actual shape of the piston side surface on oil film parameters. Journal of Kones. 7(1-2).
• [16] Piątkowski, J., Grabowski, A. & Czerepak, M. (2016). The influence of laser surface remelting on the microstructure of EN AC-48000 cast alloy. Archives of Foundry Engineering. 16(4), 217-221. DOI: 10.1515/afe-2016-0112.

Expert Q&A: Your Top Questions Answered

Q1: Why was the cooling system for the permanent moulds modernized so extensively?

A1: The paper explains that the old machines only cooled the main core, leading to inconsistent crystallization rates. The modern double permanent moulds use up to 8 cooling circuits with numerically controlled electrovalves. This ensures uniform cooling of the entire cast, unifies the crystallization time, and allows the casting cycle to be synchronized with robotic pouring, which is essential for achieving optimal process efficiency and consistent part quality.

Q2: What is the purpose of the "alfinating" process for the ring inserts?

A2: The "alfinating" process is critical for creating a durable bond between the austenitic cast iron ring insert and the aluminum piston body. The paper states that the process involves a short submersion of the insert in an Al-Si alloy. This creates a diffusive layer on the insert's surface, which significantly increases its adhesion to the piston casting when the molten aluminum is poured around it.

Q3: How do salt cores contribute to modern piston performance?

A3: Salt cores are used as sacrificial inserts during casting to create complex internal cooling channels inside the piston head, as seen in Figure 10. After casting, the salt core is simply washed out with water. During engine operation, oil circulates through these channels, actively cooling the piston crown and the first ring groove. This is crucial for managing the extreme heat in modern, high-output engines, thereby improving durability and preventing oil degradation.

Q4: Figure 13 shows a dramatic increase in piston production at Federal-Mogul after 2006. What were the key technological drivers for this?

A4: The paper attributes this growth to the introduction of modern, integrated casting lines after 2001. The key drivers were the full automation of casting tasks, the synchronization of permanent mould machines with casting robots, and the implementation of advanced water cooling systems. These changes shortened the alloy cooling time from around 60 seconds to 13 seconds or less, which directly increased the number of ready products and overall process efficiency.

Q5: What is the primary function of the graphite coating on the piston skirt?

A5: According to the paper, the graphite coating serves multiple functions. It is a thin layer (5 to 15 µm) that protects the guide section of the piston and reduces friction between the piston and the cylinder. Its surface also improves oil wettability and fills micro-irregularities, which enhances grinding conditions and protects the piston skirt from seizing, especially during the critical engine break-in period.

Conclusion: Paving the Way for Higher Quality and Productivity

The evolution of Piston Casting Technology over the last 50 years provides a powerful lesson in manufacturing innovation. The journey from simple, manual processes to highly automated, precisely controlled systems was driven by the relentless demand for higher engine performance and efficiency. The key breakthrough lies in the holistic integration of process technology—like robotic handling and advanced thermal management—with component design, including cast-in inserts and sophisticated surface coatings. This combination is what allows modern pistons to survive and thrive in extreme environments.

At CASTMAN, we are committed to applying the latest industry research to help our customers achieve higher productivity and quality. If the challenges discussed in this paper align with your operational goals, contact our engineering team to explore how these principles can be implemented in your components.

Copyright Information

• This content is a summary and analysis based on the paper "Casting of Combustion Engine Pistons Before and Now on the Example of FM Gorzyce" by "M. Czerepak and J. Piątkowski".
• Source: https://doi.org/10.24425/afe.2023.144296

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