What Is Centrifugal Casting?

Centrifugal casting or rotocasting is a casting technique commonly used to cast thin-walled cylindrical parts. It is commonly used to cast metals such as aluminum and iron to provide standard-sized blanks for custom parts with complex shapes.

For companies seeking economic benefits and low processing requirements, but requiring high precision and low tolerances, most will choose centrifugal casting over forging and other processing processes.

Molten metal is poured into a preheated rotating mold that is placed horizontally or vertically (depending on the specific part). Under the action of centrifugal pressure, the molten metal is evenly dispersed in the outer area of ​​the circular mold cavity, and it is cooled to produce high-quality parts.

 

Differences from Other Casting Methods

Centrifugal casting stands apart from other common casting techniques due to its reliance on rotational force:

• Vs. Sand Casting: Sand casting uses disposable sand molds and relies on gravity to fill the mold. This can lead to issues like porosity and inclusions. Centrifugal casting, in contrast, uses permanent or semi-permanent molds and leverages centrifugal force, which significantly reduces porosity, improves density, and pushes impurities towards the inner surface where they can be machined away.

• Vs. Investment Casting: Investment casting (lost wax casting) is known for producing intricate, high-precision parts with excellent surface finish. While it offers superior detail, it is often a more labor-intensive and costly process, especially for larger or simpler geometries. Centrifugal casting, particularly centrifuging, can offer similar precision for certain small parts but generally excels in producing robust, hollow, or symmetrical components more efficiently.

• Vs. Die Casting: Die casting uses high pressure to force molten metal into reusable metal dies. It’s ideal for high-volume production of parts with thin walls and good surface finish. However, die casting is typically limited to lower melting point alloys and can be expensive for tooling. Centrifugal casting is more versatile in terms of material selection (including high-temperature alloys) and is better suited for producing parts with rotational symmetry, where the centrifugal force can be optimally utilized for metallurgical advantages.

Centrifugal Casting Process: A Step-by-Step Explanation

Regardless of its specific type, the centrifugal casting process typically follows these fundamental steps:

Mold Preparation

Centrifugal casting molds, which are smooth and cylindrical internally, possess semi-permanent and permanent characteristics. These are usually made from steel, graphite, or cast iron. Before manufacturing officially begins, the molds must be thoroughly cleaned by workers, and a refractory coating or insulating layer is patiently applied. This process, while protecting the mold, facilitates subsequent part removal and enhances cooling speed.

Mold Heating

The mold is preheated to a specific temperature, which varies depending on the metal being used. For example, when iron is being centrifugally cast, it can be preheated to 2500 degrees Fahrenheit. Heating to the appropriate temperature is beneficial for protecting the mold, aiding the metal in cooling and hardening at a suitable rate, and thereby enabling the batch production of high-quality parts.

Mold Rotation

Controlling the mold’s rotation speed is crucial. If the speed is too fast, the casting can easily crack. If it’s too slow, impurities in the molten metal cannot be effectively expelled, and irregularities may appear on the casting’s surface and interior. Therefore, the casting material, its size and shape, the mold structure, and the pouring temperature must be comprehensively considered.

Molten Metal Pouring

Before pouring, the molten metal has already been refined to remove impurities. The position where the metal is poured varies with different centrifugal casting methods. In true centrifugal casting, the metal is directly poured into the rotating mold. In semi-centrifugal casting, the metal is poured into a central sprue; in centrifuging, it is poured into a central mold trough.

Solidification

Under the continuous action of centrifugal force, denser, heavier metals are pushed towards the mold walls, while lighter impurities and oxides accumulate and remain on the internal surface or at the center. Subsequently, the metal begins to cool and harden from the outside in.

Removing the Solidified Casting from the Mold

Once the mold’s rotation stops, the casting is confirmed to be solid. After the desired hardness and quality have been achieved, the mold can be removed, and the final solidified casting can be extracted.

Post-Casting Operations

Depending on the casting’s characteristics and application, it may undergo the following subsequent treatment steps: cooling, cleaning, machining (especially to remove the internal impurity layer in true centrifugal castings), heat treatment, and inspection.

Vertical vs Horizontal Centrifugal Casting

The orientation of the mold’s rotational axis defines two main configurations:

• Horizontal Centrifugal Casting: In this setup, the mold rotates horizontally. It is predominantly used for producing long, thin-walled cylindrical parts such as pipes, tubes, and liners, where maintaining uniform wall thickness along the length is crucial. The length-to-diameter ratio can be quite high.

• Vertical Centrifugal Casting: Here, the mold rotates vertically. This method is generally preferred for producing shorter, larger-diameter rings, bushings, and other disc-shaped parts. Gravity plays a more significant role in the vertical orientation, influencing the distribution of metal and allowing for the production of parts with varying wall thicknesses along their height if designed accordingly.

Main Types of Centrifugal Casting

True Centrifugal Casting

True centrifugal casting is the quintessential form of the process, specifically designed for creating hollow, rotationally symmetrical components.

• For tubes, pipes, sleeves: This method is the go-to for manufacturing products like seamless pipes, cylinder liners, bearing races, and various types of sleeves. The absence of a core simplifies the process and eliminates potential core-related defects. The natural segregation of impurities to the inner diameter means that a final machining step can easily remove these defects, leaving a high-quality, dense outer wall.

• Mould types, speeds: Molds for true centrifugal casting are typically made from steel, cast iron, or graphite, chosen for their durability and thermal properties. They can be either permanent or semi-permanent. The rotational speed is a critical parameter, precisely calculated based on the desired part dimensions, material properties, and the need to generate sufficient centrifugal force (G-force, typically 60-100 Gs) to ensure proper metal distribution and prevent “raining” of the molten metal.

Semi-Centrifugal Casting

Semi-centrifugal casting addresses the need for dense, solid, or partially hollow, rotationally symmetrical parts where a central core is required.

• For solid parts like gear blanks, pulleys: This method is widely used to produce components such as gear blanks, flywheels, railway wheels, and pulleys. The centrifugal force aids in feeding the molten metal from the central sprue to the extremities of the mold cavity, reducing porosity and ensuring a high-density structure in the critical outer sections of the part.

• Process and typical materials: The process involves pouring molten metal into a rotating mold with a central core. The rotational speed is lower than in true centrifugal casting, as the primary goal is not to form a free inner surface but to enhance feeding and density. Common materials include cast iron, steel, and non-ferrous alloys.

Centrifuging

Centrifuging, also known as pressure casting or centrifugal investment casting, is a specialized application of centrifugal force for precision casting.

• Suitable for small precision parts like bushings, jewelry, nozzles: This method is particularly effective for producing multiple small, intricate components with excellent detail and surface finish. It is widely employed in industries like aerospace (for small turbine blades), medical (implants), and even the production of jewelry and dental prosthetics, where high precision and consistent quality are paramount.

• Differences from above: The key distinction from true and semi-centrifugal casting is the use of multiple individual mold cavities arranged around a central sprue on a spinning table. The centrifugal force acts to rapidly fill these cavities, ensuring complete filling of even the most complex geometries and promoting directional solidification, leading to fine grain structures and minimal defects. Unlike the other two methods, the primary benefit here is not the creation of a hollow part or enhancing density in a large solid part, but rather the efficient and precise filling of numerous small, often intricate, mold cavities.

Common Materials for Centrifugal Casting

Centrifugal casting is compatible with a variety of metals, allowing manufacturers to choose materials based on performance requirements such as strength, corrosion resistance, and thermal stability. Below are the most commonly used materials in centrifugal casting operations.

Aluminum Alloys

Aluminum centrifugal casting is widely used for components that require lightweight and excellent corrosion resistance. Typical alloys include A356, 319, and 6061. These are often used for automotive housings, aerospace parts, and heat exchanger sleeves.

Molten aluminum is very fluid and solidifies quickly on the mold walls. This makes it ideal for producing large aluminum parts through centrifugal casting, with fine grains and little porosity.

Stainless Steel

Stainless steel is very suitable for centrifugal casting due to its excellent corrosion resistance, high strength and high temperature resistance. This casting process can produce high-density, uniform round or tubular parts, which are widely used in pump bodies, valves, pipelines and special annular parts in the aerospace and chemical industries. Centrifugal casting of stainless steel parts requires high technology and equipment, so it is more suitable for professional casting companies with advanced engineering capabilities and quality control systems.

Nickel Alloys

Nickel-based alloys, including Inconel and Hastelloy, are used when thermal resistance and chemical durability are essential. These materials are common in aerospace, marine, and power generation industries. Although more difficult to cast due to high melting points and oxidation tendencies, large centrifugal nickel castings are possible using vacuum-assisted or inert gas-controlled environments, which are standard in advanced centrifugal foundries in China.

Cast Iron

Cast iron has excellent fluidity and solidification characteristics. This material is particularly suitable for manufacturing complex parts in tubular or annular shapes. Including gray cast iron and ductile iron, with high density and excellent strength, it is ideal for heavy-duty applications.

This technology is widely used in industries such as oil and gas, chemicals, and ships to produce key components such as pipes, cylinder liners, and annular parts.

Given the high requirements of centrifugal casting for process control and equipment precision, only medium and large enterprises with advanced equipment and mature technical strength can achieve the expected quality.

Copper

Centrifugal casting copper parts take advantage of the excellent electrical conductivity, thermal conductivity and corrosion resistance of copper alloys, and are particularly suitable for producing high-precision, high-density tubular or annular parts. This technology is versatile and frequently employed in manufacturing bearing bushings, valves, flanges, gear rings, and various parts that require excellent mechanical properties and thermal conductivity.

Due to the strict requirements on material formulation and casting process, the providers of centrifugal casting copper parts are usually large-scale enterprises with professional technology and advanced equipment.

Applications of Centrifugal Casting Products

Centrifugal casting’s unique advantages make its products indispensable across a diverse range of heavy industries, where durability, high performance, and structural integrity are paramount.

• Industries:
  • Automotive: Centrifugal casting is crucial for producing high-strength components such as cylinder liners, brake drums, and gear blanks, which require exceptional wear resistance and uniform density to withstand demanding operational conditions.
  • Aerospace: In aerospace, precision and reliability are critical. Centrifugal casting delivers high-quality rings, bushings, and specialized components for jet engines and structural parts, often utilizing superalloys for extreme temperature and stress environments.
  • Petrochemical: The petrochemical industry relies on robust components that can withstand corrosive substances and high pressures. Centrifugally cast pipes, tubes, and pump casings made from corrosion-resistant alloys are vital for safe and efficient operations in refineries and chemical plants.
  • Marine: For marine applications, components must endure harsh saltwater environments and heavy loads. Centrifugally cast propeller shafts, stern tube liners, and various bushings offer superior corrosion resistance and mechanical strength, ensuring longevity and reliability at sea.
  • Municipal: Infrastructure projects, particularly water and wastewater systems, extensively use centrifugally cast ductile iron pipes and fittings due to their strength, leak-proof nature, and long service life, contributing to efficient urban utilities.
• Typical Parts:
  • Bushings: Often made from bronze or specialized alloys, centrifugally cast bushings provide excellent wear resistance and are used in heavy machinery, automotive suspensions, and industrial pumps.
  • Pipes and Liners: Seamless pipes and cylinder liners, particularly for engines and hydraulic systems, benefit from the process’s ability to create a dense, uniform wall thickness and a clean outer surface.
  • Pump Components: Impellers, casings, and wear rings for various types of pumps are frequently centrifugally cast, ensuring high efficiency and resistance to abrasion and corrosion.
  • Shaft Sleeves: These protective components for shafts are ideal for centrifugal casting, offering a precise fit and superior material properties to extend the lifespan of rotating equipment.

Benefits of Centrifugal Casting

The distinct methodology of centrifugal casting confers several significant advantages over other casting processes, making it a preferred choice for critical applications.

• High Density and Mechanical Strength: The primary benefit stems from the centrifugal force itself. As the molten metal is spun, denser metal is forced to the mold wall, while lighter impurities and gases are pushed towards the inner diameter. This results in a casting with exceptionally high density, minimal porosity, and a fine, uniform grain structure, leading to superior mechanical properties such as tensile strength, yield strength, and fatigue resistance. The directional solidification from the outside in further enhances these characteristics.
• Minimal Waste and Excellent Surface Finish: Because the process inherently pushes impurities to the inner surface, this contaminated layer can be easily machined away, leaving a clean, sound casting. This reduces overall material waste compared to methods where defects might be distributed throughout the part. While the inner surface requires machining, the outer surface, formed against the mold, typically exhibits a good as-cast finish, minimizing post-processing requirements for external dimensions.
• Ideal for Hollow Cylindrical Parts: Centrifugal casting is uniquely suited for producing hollow, axis-symmetrical components without the need for cores. This eliminates core-related defects and simplifies manufacturing, making it highly efficient for items like pipes, tubes, and rings. The process ensures concentricity and uniform wall thickness, which are difficult to achieve with other casting methods for such geometries.
• Considerations: While highly advantageous, it’s worth noting that centrifugal casting is primarily suited for parts with rotational symmetry. Initial tooling costs can be higher than some simpler casting methods, but this is often offset by the superior quality and reduced post-processing for high-volume or critical components.

Choosing the Right Centrifugal Casting Manufacturer

Selecting a reliable centrifugal casting manufacturer is crucial for ensuring the quality and performance of your components.

• In-house vs. Outsourced:
  • In-house: Offers maximum control over the entire production process, potentially faster turnaround for urgent needs, and closer integration with your design team. However, it requires significant capital investment in equipment, skilled labor, and ongoing maintenance.
  • Outsourced: Provides access to specialized expertise, advanced equipment, and economies of scale without the capital outlay. It allows you to focus on your core competencies. The challenge lies in selecting a trustworthy partner who can consistently meet your quality and delivery requirements.
• China vs. Local Suppliers:
  • China Suppliers: Often offer competitive pricing due to lower labor and operational costs, along with vast production capacities. Many Chinese manufacturers have state-of-the-art facilities and extensive experience. Considerations include longer lead times, potential communication differences, and the need for thorough due diligence on quality control.
  • Local Suppliers: May offer faster delivery, easier communication, and closer oversight. They can be beneficial for smaller runs or highly specialized needs where proximity is an advantage. However, costs might be higher compared to overseas options.
• How to Evaluate a Centrifugal Casting Supplier:
  • Certifications: Look for internationally recognized certifications such as ISO 9001 (quality management), ISO 14001 (environmental management), and material-specific certifications like ASTM or ASME compliance, which demonstrate adherence to rigorous standards.
  • Experience: Assess their years in the industry, their track record, and specific experience with your required materials, part geometries, and industry applications. A manufacturer with a proven history of success in similar projects is a strong indicator of reliability.
  • Equipment and Technology: Inquire about their centrifugal casting machines (horizontal and vertical), melting furnaces, machining capabilities, and any advanced inspection equipment (e.g., NDT, spectral analysis). Modern, well-maintained equipment is essential for precision and consistency.
  • Capacity: Understand their production capacity to ensure they can meet your volume requirements and deliver within your desired lead times, whether for high-volume production or prototype runs.
  • Quality Control Standards: A reputable supplier will have a robust quality control system, including in-process checks, final inspection, and material testing, to guarantee that products meet specifications.

Why Choose CSMFG for Your Centrifugal Casting Needs?

As a leading China-based manufacturer, CSMFG is dedicated to providing superior centrifugal casting services that meet the most stringent industry demands.

• Overview of CSMFG’s Capabilities: CSMFG boasts state-of-the-art centrifugal casting facilities, equipped with both horizontal and vertical casting machines capable of handling a wide range of sizes and materials, including stainless steel, aluminum, nickel alloys, and various copper alloys. CSMFG’s team of experienced engineers and metallurgists possesses deep expertise in optimizing casting parameters for diverse applications.
• Customization Options: CSMFG understands that every project is unique. CSMFG’s services are highly customizable, from material selection and mold design to precise dimensional tolerances and post-casting treatments. CSMFG works closely with clients from concept to completion, ensuring that the final product perfectly aligns with their specifications and performance requirements.
• Quality Control Standards: Quality is at the core of everything CSMFG does. CSMFG’s comprehensive quality management system adheres to international standards, including ISO 9001. CSMFG implements rigorous testing and inspection protocols at every stage of the process, from raw material verification and molten metal analysis to dimensional checks, non-destructive testing (NDT), and mechanical property testing of the finished product.
• Industries Served: CSMFG’s proven track record extends across numerous sectors, including automotive, aerospace, petrochemical, marine, municipal infrastructure, and general industrial machinery. CSMFG is proud to be a trusted partner for companies seeking high-performance, defect-free cast components.

Get a Free Quote Today. Contact CSMFG now to discuss your project requirements and receive a detailed, no-obligation quote for CSMFG’s expert centrifugal casting services.

FAQ about Centrifugal Casting

What is the difference between sand casting and centrifugal casting?

Sand casting allows for complex shapes using temporary molds but often results in rough finishes and internal defects. In contrast, centrifugal casting uses spinning permanent molds to produce dense, high-quality cylindrical parts with better material integrity and symmetry.

What are the main types of centrifugal casting?

True centrifugal casting (for hollow parts), semi-centrifugal casting (for solid parts with cores), and centrifuging (for small, intricate precision parts).

What are the key benefits of this process?

High density, superior mechanical strength, minimal material waste, excellent surface finish, and ideal for hollow cylindrical components.

How do I evaluate a centrifugal casting manufacturer?

Look for certifications (e.g., ISO 9001), experience, modern equipment, sufficient capacity, and robust quality control standards.

What materials can CSMFG centrifugally cast?

CSMFG handles a wide range, including stainless steel, aluminum, nickel alloys, and various copper alloys.

Does CSMFG offer post-casting services?

Yes, CSMFG provides comprehensive post-processing, including machining, heat treatment, surface finishing, and quality inspection.