Choosing the Right Casting Method for Automotive Parts: A Review of Green Sand, Die Casting, and More

This technical summary is based on the academic paper "Automobile Parts Casting-Methods and Materials Used: A Review" by Madhav Goenka, Chico Nihal, Rahul Ramanathan, Pratyaksh Gupta, Aman Parashar, and Joel Jb, published in Materials Today: Proceedings (2020). It has been analyzed and summarized for technical experts by CASTMAN with the assistance of AI.

Keywords

• Primary Keyword: Automobile Parts Casting
• Secondary Keywords: Die Casting, Green Sand Casting, Centrifugal Casting, Al-Si Alloys, Engine Block Casting, Squeeze Casting

Executive Summary

A 30-second overview for busy professionals.

• The Challenge: Automotive manufacturers face constant pressure to reduce vehicle weight using high strength-to-weight ratio materials while meeting stringent safety standards, necessitating innovative and efficient manufacturing methods.
• The Method: The paper provides a comprehensive review of five key casting processes used in the automotive industry: Green sand casting, Centrifugal casting, Lost-foam casting, Die casting, and Squeeze casting.
• The Key Breakthrough: Die casting is highlighted as a versatile, high-accuracy process for a wide range of parts, while specialized processes like green sand casting offer an inexpensive alternative for components with less demanding tolerances, and squeeze casting enables the use of advanced metal matrix composites.
• The Bottom Line: The optimal choice for Automobile Parts Casting depends entirely on the component's specific requirements, balancing factors like cost, dimensional accuracy, mechanical properties, and production volume.

The Challenge: Why This Research Matters for HPDC Professionals

In today's automotive industry, the drive for efficiency and safety is relentless. Manufacturers are tasked with reducing the kerb weight of vehicles to improve fuel economy and performance, while simultaneously making parts stronger to comply with high standards set by programs like NCAP. This dual challenge pushes engineers to explore innovative manufacturing methods and advanced materials. Casting, a cost-effective process for producing dimensionally accurate components, is central to this effort. However, with numerous casting techniques available—each with unique pros and cons—selecting the right process and material for a specific part like an engine block, piston, or transmission housing is a critical decision that impacts performance, cost, and quality. This paper addresses this challenge by reviewing the most prominent casting methods and materials used in modern automobile manufacturing.

The Approach: Unpacking the Methodology

This paper conducts a comprehensive review of the primary casting methods and materials relevant to the automotive industry. The authors analyze five distinct processes:

1. Green Sand Casting: A traditional method using a mold made of sand, clay, water, and other additives.
2. Centrifugal Casting: A technique where molten metal is poured into a rotating mold, using centrifugal force to distribute the metal.
3. Lost-Foam Casting: A process that uses a polystyrene foam pattern which vaporizes when molten metal is poured into the mold.
4. Die Casting: A method where molten metal is injected under high pressure into a permanent metal mold (die).
5. Squeeze Casting: A hybrid process combining casting and forging, where molten metal solidifies under high pressure.

The review examines the suitability of various materials for these processes, including grey cast iron, Compacted Graphite Iron (CGI), aluminum-silicon (Al-Si) alloys, and Metal Matrix Composites (MMCs). The paper evaluates each method based on its advantages, limitations, and specific applications in producing automotive components.

The Breakthrough: Key Findings & Data

[Based on the paper's Results section, present the 2-3 most significant findings with concrete data.]

Finding 1: Material Properties Dictate Process Selection for Engine Blocks

The choice of material for engine blocks is critical, and the paper highlights the shift from traditional Grey Cast Iron to more advanced materials like Compacted Graphite Iron (CGI) and aluminum alloys. When using green sand casting, CGI is preferred due to its superior mechanical properties. As shown in Table 1, CGI offers a significantly higher Modulus of Elasticity (170-190 GPa vs. 98-110 GPa for Grey Cast Iron) and Tensile Strength (300-600 Mpa vs. 160-320 Mpa), providing a much better strength-to-weight ratio. Aluminum alloy 319 (containing 5.5-6.5% silicon and 3-4% copper) is also used for its high strength-to-weight ratio.

Finding 2: Specialized Processes Yield Superior Component Performance

For specific components, specialized casting methods deliver significant performance gains over more traditional approaches. The paper compares pistons made via centrifugal casting versus those made by gravity permanent mould casting. The centrifugally cast piston demonstrated a 70.4% improvement in wear analysis and a hardness increase of 23.7HRB from the piston skirt to the head. Furthermore, squeeze casting proves highly effective for producing components from Metal Matrix Composites (MMCs). The paper notes that squeeze-cast components were found to have 20-30% better mechanical properties than parts made with die casting.

Practical Implications for R&D and Operations

• For Process Engineers: This study suggests that adjusting the cooling rate during sand casting is critical, as an accelerated rate promotes cementite formation while slow cooling forms a mixed microstructure of cementite and graphite. For high-quality, thin-walled components, low-pressure die casting is shown to be an effective method for reducing porosity compared to gravity die casting.
• For Quality Control Teams: The data in the paper comparing centrifugal casting to gravity permanent mould casting for pistons (a 70.4% wear improvement) illustrates how process selection directly impacts component durability. This could inform new quality inspection criteria focused on microstructure and wear resistance for critical moving parts.
• For Design Engineers: The findings indicate that die casting is highly suitable for thin-walled automotive components, capable of producing walls as thin as 0.75 mm with a smooth surface finish. This allows for lightweight and intricate designs. However, the paper also emphasizes that an appropriate draft angle is crucial in die design to ensure easy removal of the cast part.

Paper Details

Automobile Parts Casting-Methods and Materials Used: A Review

1. Overview:

• Title: Automobile Parts Casting-Methods and Materials Used: A Review
• Author: Madhav Goenka, Chico Nihal, Rahul Ramanathan, Pratyaksh Gupta, Aman Parashar, Joel Jb
• Year of publication: 2020
• Journal/academic society of publication: Materials Today: Proceedings 22 (2020) 2525-2531
• Keywords: Centrifugal Casting; Die Casting; Engine Block; Piston; Al-Si Alloys; CGI

2. Abstract:

Automobiles are becoming more and more sophisticated with every passing year. Manufacturers have been trying their best to bring down the kerb weight of their automobiles by using various materials with high strength to weight ratio. The different parts of the automobile are being made much stronger than before in order to comply with the high standards set by NCAP. Hence, this pushes automobile makers to come up with new and innovative methods to manufacture the parts of their automobiles. Our paper addresses the various casting processes used to make automobile parts and also touches on the various materials used to make the components. The casting methods discussed are- Green sand casting, Centrifugal casting, Lost- foam casting, Die casting and Squeeze casting. In the paper we discuss about the most suited materials used for each component and briefly discuss about the pros and cons of each process.

3. Introduction:

Casting is the process of pouring a liquid metal into a mold of specific dimensions in order to obtain a desired shape. Casting is preferred in industries as it is cost effective and produces dimensionally accurate components. Casting can be carried out using most metals, however the metals most predominantly used are iron, aluminum, steel and copper based alloys.

4. Summary of the study:

Background of the research topic:

The automotive industry is driven by the need to make vehicles lighter and stronger to meet performance goals and safety standards like those from NCAP. This has led to the use of advanced materials with high strength-to-weight ratios and the development of innovative manufacturing methods.

Status of previous research:

Casting has a long history, evolving from simple techniques to sophisticated modern processes like squeeze casting, centrifugal casting, and die casting. Materials have similarly evolved from basic metals to advanced Al-Si alloys, MMCs, and Zinc. Metal casting is a major market in the automotive industry, used for key components like pistons, engine blocks, and transmission housings.

Purpose of the study:

The paper aims to review the various casting processes (Green sand, Centrifugal, Lost-foam, Die, and Squeeze casting) and materials used to manufacture automobile parts. It seeks to discuss the most suitable materials for each component and evaluate the pros and cons of each process.

Core study:

The study provides a detailed analysis and comparison of five major casting methods. It discusses the process details, advantages, limitations, and material choices (e.g., Grey Cast Iron, CGI, Al-Si alloys) for each. Specific automotive applications such as engine blocks, pistons, cylinder heads, and wheels are used as examples to illustrate the practical application of each technique.

5. Research Methodology

Research Design:

The paper is a literature review. It synthesizes and analyzes existing research, technical papers, and industry knowledge on casting processes and materials used in the automotive sector.

Data Collection and Analysis Methods:

The authors collected information on five distinct casting processes. The analysis is comparative, discussing the benefits and drawbacks of each method and material in the context of manufacturing specific automotive components, supported by data from cited studies and tables comparing material properties.

Research Topics and Scope:

The research focuses on five casting processes: Green sand casting, Centrifugal casting, Lost-foam casting, Die casting, and Squeeze casting. The scope is limited to their application in the automobile industry for parts such as engine blocks, pistons, cylinder heads, and wheels.

6. Key Results:

Key Results:

• Green Sand Casting: A cost-effective process with design flexibility but suffers from low dimensional accuracy, poor surface finish, and defects like porosity. Compacted Graphite Iron (CGI) is a preferred material over Grey Cast Iron for its better mechanical properties.
• Centrifugal Casting: Ideal for cylindrical parts, it produces components with high metallurgical cleanliness and a homogenous microstructure, free from shrinkage and porosities. For pistons, it results in significantly better wear resistance compared to gravity permanent mould casting.
• Lost-Foam Casting: A reliable technique for complex, thin-walled parts like engine blocks. Magnesium alloys are preferred for their high strength-to-weight ratio and good workability.
• Die Casting: Widely used for its ability to mass-produce parts with high accuracy, uniformity, and excellent surface finish. It is ideal for lightweight zinc and aluminum parts. Low-pressure die casting (LPDC) is predominantly used for producing complex, lightweight aluminum wheels.
• Squeeze Casting: A process that combines casting with forging, ideal for creating metal matrix composite (MMC) parts. It produces components with enhanced mechanical properties (20-30% better than die casting) and reduced porosity.

Figure Name List:

• Fig. 1. Aluminium Die Cast Parts.
• Fig. 2. Flow chart of manufacturing of MMC pistons using squeeze casting.
• Fig. 3. The process of squeeze casting. (a) Initial poring of molten metal; (b) Plunger moving; (c) Plunger moving to reach the gate of molten metal; (d) Plunger moving to completely filling of die cavity.

7. Conclusion:

In this paper the casting processes which are most specifically used in the automobile industry have been discussed and attempts have been made to give a comprehensive evaluation of the processes which would be most suited for casting a particular part. During the course of this evaluation it was found that Die casting finds a ubiquitous application in casting most of the automobile parts, despite its high cost. Other processes like green sand casting can be used as an inexpensive alternative for casting parts which are less demanding on dimensional accuracy and surface finish. Based on the requirement of the part to be cast, specialised processes can be used the material and process parameters of which have been elucidated in this paper.

8. References:

• [1] H. Nguyen, "Manufacturing Processes and Engineering Materials Used in Automotive Engine Block," Mater. Sci. Eng. Sect. B, EGR250, pp. 11-23, 2005.
• [2] A. V. Adedayo, "Effects of addition of iron (Fe) filings to green moulding sand on the microstructure of grey cast iron," J. Brazilian Soc. Mech. Sci. Eng., vol. 32, no. 2, pp. 171-175, 2010.
• [3] D. Anantha Padmanaban and G. Kurien, "Silumins: The automotive alloys," Adv. Mater. Process., vol. 170, no. 3, pp. 28–30, 2012.
• [4] G. Chirita, D. Soares, and F. S. Silva, "Advantages of the centrifugal casting technique for the production of structural components with Al-Si alloys," Mater. Des., vol. 29, no. 1, pp. 20–27, 2008.
• [5] N. Periyasamy, "Thermal Analysys and Material Optimization of Piston in IC Engine," no. 3, pp. 1132-1144, 2018.
• [6] Q. Bakhsh, D. Ali, A. Ahmed, M. S. Wahab, K. Kamarudin, and A. A. Raus, "Mechanical Properties, Material and Design of the Automobile Piston: An Ample Review," Indian J. Sci. Technol., vol. 9, no. 36, pp. 5-11, 2016.
• [7] P. Scarber, H. Littleton, and A. Druschitz, "Preliminary Study of Compacted Graphite Iron Engine Blocks Produced by the Lost Foam Casting Process," AFS Trans, pp. 881-890, 2009.
• [8] R. Colás, J. Talamantes-Silva, S. Valtierra, F. Morales, and A. J. Pérez-Unzueta, "Cast-In Hypereutectic Aluminum Liners for Engine-Blocks," J. Manuf. Sci. Eng., vol. 131, no. 1, p. 014502, 2009.
• [9] M. Javidani and D. Larouche, "Application of cast Al-Si alloys in internal combustion engine components," Int. Mater. Rev., vol. 59, no. 3, pp. 132-158, 2014.
• [10] E. Aguirre-De La Torre, U. Afeltra, C. D. Gómez-Esparza, J. Camarillo-Cisneros, R. Pérez-Bustamante, and R. Martínez-Sánchez, "Grain refiner effect on the microstructure and mechanical properties of the A356 automotive wheels," J. Mater. Eng. Perform., vol. 23, no. 2, pp. 581-587, 2014.
• [11] B. Zhang, S. L. Cockcroft, D. M. Maijer, J. D. Zhu, and A. B. Phillion, "Casting defects in low-pressure die-cast aluminum alloy wheels," Jom, vol. 57, no. 11, pp. 36-43, 2005.
• [12] M. V. Kevorkijan, "MMCs for automotive applications," Am. Ceram. Soc. Bull., vol. 77, no. 12, pp. 53-59, 1998.
• [13] S. W. Youn, C. G. Kang, and P. K. Seo, "Thermal fluid/solidification analysis of automobile part by horizontal squeeze casting process and experimental evaluation," J. Mater. Process. Technol., vol. 146, no. 3, pp. 294-302, 2004.
• [15] Wu Shenqing and Li Jun, "Application of ceramic short fiber reinforced Al alloy matrix composites on piston for internal combustion engines."
• [16] Schrader, George F, Elshennawy, Ahmad K, Doyle, Lawrence E, "Manufacturing processes and materials", SME, p.186, ISBN 978-0-87263-517-3.

Expert Q&A: Your Top Questions Answered

Q1: Why is Compacted Graphite Iron (CGI) preferred over Grey Cast Iron for engine blocks made with green sand casting?

A1: According to the data in Table 1 of the paper, CGI provides significantly better mechanical properties. It has a higher Modulus of Elasticity (170-190 GPa for CGI vs. 98-110 GPa for Grey Cast Iron) and a much higher Tensile Strength (300-600 Mpa vs. 160-320 Mpa). This results in a superior strength-to-weight ratio, which is critical for modern engine design where reducing weight without sacrificing strength is a primary goal.

Q2: What specific advantage does centrifugal casting offer over gravity permanent mould casting for pistons?

A2: The paper cites a study that found a centrifugally cast piston had a 70.4% improvement in wear analysis compared to a piston made from gravity permanent mould casting. Additionally, the hardness from the piston skirt to the piston head increased by 23.7HRB. The centrifugally cast piston also had a coefficient of linear expansion that was about 23% lower, contributing to better dimensional stability under thermal stress.

Q3: The paper mentions Al-Si alloys may soften at high temperatures in die casting. What is a key challenge this presents for a part like a cylinder head?

A3: The paper notes that for a cylinder head, the maximum load it experiences is the thermal load caused by non-uniform thermal expansion and contraction. In a start-stop cycle, an engine can warm up from 243 K to 523 K. This thermal stress, combined with the material's tendency to soften at high temperatures, can hamper the surface characteristics and overall performance of the cylinder head.

Q4: What are the primary limitations of the green sand casting process mentioned in the paper?

A4: While green sand casting is cost-effective and offers good design flexibility, the paper identifies several key limitations. The process does not provide adequate strength due to high porosity. It also results in low dimensional accuracy and a very poor surface finish, often requiring secondary machining operations. Furthermore, defects such as shrinkage, porosity, and other surface defects are described as unavoidable.

Q5: How does squeeze casting improve the properties of aluminum alloys for parts like connecting rods?

A5: Squeeze casting allows for the fabrication of parts from Metal Matrix Composites (MMCs), where reinforcements like ceramic fibers are added to the aluminum alloy. As stated in the paper, this process results in components with 20-30% better mechanical properties than traditional die casting. For parts like connecting rods, this leads to a reduction in reciprocating weight, noise, and fuel consumption while increasing overall engine power.

Conclusion: Paving the Way for Higher Quality and Productivity

This review effectively outlines the complex trade-offs involved in Automobile Parts Casting. The core challenge remains balancing cost, weight, and strength. The paper concludes that while Die Casting is a versatile, high-accuracy solution for many components, its high cost makes it essential to consider alternatives. Processes like green sand casting offer a low-cost option for less critical parts, while advanced methods like centrifugal and squeeze casting provide superior mechanical properties for high-performance applications. The optimal path forward requires a deep understanding of how each process and material aligns with the specific functional requirements of the component.

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 "Automobile Parts Casting-Methods and Materials Used: A Review" by "Madhav Goenka, et al.".
• Source: Available online at www.sciencedirect.com, Materials Today: Proceedings 22 (2020) 2525-2531

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