What Is Centrifugal Casting?

1. Introduction

Centrifugal casting stands out as a specialized metal-casting process in which molten metal solidifies under intense centrifugal force.

Enabling manufacturers to produce high‑integrity, axisymmetric components with superior mechanical properties.

First patented by A.G. Eckhardt in Germany in 1809 and later refined in the 19th century for industrial pipe production, the process now accounts for an estimated 15 % of global pipe and tube output.

Its ability to minimize impurities and directional solidification makes centrifugal casting indispensable in sectors ranging from oil & gas to aerospace.

2. Definition and Principles of Centrifugal Casting

What Is Centrifugal Casting?

In centrifugal casting, molten metal enters a rapidly rotating mold, where centrifugal force (Fc = m·ω²·r) drives the liquid outward, producing a dense, defect‑free solid.

By controlling rotational speeds—typically 100–500 RPM—foundries generate forces of 20 g to over 200 g, dramatically outpacing gravity.

The Role of Centrifugal Force

Centrifugal force concentrates heavier metallic elements at the mold’s outer radius, while lighter oxides and inclusions remain near the bore.

Consequently, operators machine away the inner diameter “center‑line” drop, yielding sound metal with up to 30 % higher tensile strength than gravity‑cast counterparts.

Horizontal vs. Vertical Casting

• Horizontal Centrifugal Casting: Ideal for pipes and long tubes, this orientation maintains consistent wall thickness over lengths exceeding 10 m, with wall variations under ± 1 %.
• Vertical Centrifugal Casting: Suited to shorter, rigid parts—like bushings and bearing races—vertical setups require less floor space and achieve similar density improvements.

Mold Rotation, Force Dynamics, and Cooling

Foundries preheat molds to 300–600 °C, then pour metal at its liquidus temperature (e.g., cast iron at 1 420 °C).

As the mold spins, a water‑jacketed cooling system extracts heat at 5–10 °C/min, promoting outside‑in solidification and preventing center‑line porosity.

3. Types of Centrifugal Casting

Centrifugal casting comes in several distinct variants, each tailored to specific geometries, materials and performance requirements.

True (Conventional) Centrifugal Casting

• Process: Molten metal pours into a smooth, rotating cylindrical mold; gravity plays only a minor role.
• Features:

• • Produces seamless tubes, pipes and hollow cylinders with wall thicknesses from 3 mm to 200 mm.
  • Delivers radial grain flow and densification at the outer diameter, boosting tensile strength by up to 30 % over gravity‑cast equivalents.

• Applications: Pressure pipes (API 5CT), engine cylinder liners and pump casings.

Semi‑Centrifugal Casting

• Process: Combines centrifugal force with controlled gating; a central core forms internal cavities (e.g., spokes).
• Features:

• • Suits parts that require a solid central web, such as gear blanks and flywheels.
  • Balances metal distribution: heavier sections form toward the mold wall, while fins and spokes receive directed feed metal.

• Applications: Automotive flywheels, locomotive driving wheels, large bronze impellers.

Centrifuged (Multi‑Mold) Casting

• Process: Multiple molds attach radially around a central spindle; one pour yields dozens of identical castings.
• Features:

• • Ideal for small, repetitive components (e.g., bearings, bushings).
  • Achieves high throughput: a single 10‑m spindle can support 20–30 molds, producing hundreds of parts per hour.

• Applications: Bushing rings, valve seats, small impellers.

Vertical Centrifugal Casting

• Process: The mold spins on a vertical axis; molten metal enters from the top and fills downward.

• Features:

• • Offers compact footprint—equipment heights typically under 3 m.
  • Provides excellent control over inner diameter quality and eliminates centerline porosity in shorter parts.

• Applications: Bearing sleeves, bushings, bearing races, and short pipe sections.

Horizontal Centrifugal Casting

• Process: The mold rotates about a horizontal axis; metal pours at one end and travels axially before solidification.

• Features:

• • Extends to very long castings—commonly over 10 m—with uniform wall thickness variation under ± 1 %.
  • Simplifies removal of slag and dross, as impurities concentrate at the bore.

• Applications: Long pressure pipes, large‑diameter tubes and railcar wheels.

Vacuum Centrifugal Casting

• Process: Operators evacuate the mold chamber to < 10⁻² Pa prior to pouring, then spin and solidify under vacuum.
• Features:

• • Reduces dissolved gases and porosity by up to 80 %, essential for superalloys and aerospace components.
  • Maintains chemical purity, enabling sound casting of reactive alloys (e.g., titanium).

• Applications: Turbine blades, aerospace couplings, high‑performance bearing races.

4. Materials Used in Centrifugal Casting

Centrifugal casting accommodates a remarkably broad spectrum of materials, from traditional cast irons to advanced superalloys, and even non‑metallic melts.

Manufacturers select the alloy that best balances mechanical strength, corrosion resistance, thermal performance, and production cost.

Cast Iron

• Gray Iron (ASTM A395/A536) dominates approximately 60 % of centrifugal castings, notably in cylinder liners and pump casings.
• Ductile Iron (Grade 60–40–18)—with tensile strengths of 415 MPa and elongations over 10 %—adds impact resistance for applications like roller shells.

Carbon & Alloy Steels

• Carbon Steels (e.g., A216 WCB) provide tensile strengths up to 485 MPa and weldability for pressure vessels and valve bodies.
• Low‑Alloy Steels (e.g., 4140, 4340), when heat‑treated, reach 1 000+ MPa, suiting gears, shafts, and high‑stress bushings.

Stainless Steels & Nickel Alloys

• Austenitic Grades (AISI 304, 316L, CF8M) resist corrosion in chemical and food‑processing equipment; they cost 20–30 % more but eliminate post‑cast plating.
• Heat‑Resistant Alloys (310, 330) maintain strength at 1 000 °C, ideal for furnace rolls and flue pipes.
• Nickel‑Base Superalloys (Alloy 718, Waspaloy), though premium in price, deliver creep rupture strengths above 600 MPa at 650 °C, critical for aerospace bearings.

Bronze & Copper Alloys

• Aluminum Bronzes (C95400, C95500) exhibit tensile strengths of 450–550 MPa and superior marine corrosion resistance—used in impellers and propeller hubs.
• Copper‑Nickel (90–10, 70–30) alloys combine 200–300 MPa strength with excellent biofouling and chloride resistance for seawater piping.

Aluminum & Magnesium Alloys

• Aluminum (A356) rotates at 300–400 RPM to produce lightweight, non‑magnetic parts like pump housings; thermal conductivities reach 180 W/m·K.
• Magnesium Alloys (AZ91), though less common (< 5 % of volume), offer the lowest density (1.8 g/cm³) for specialized automotive and electronics housings.

Non‑Metals

• Glass: Centrifugal casting creates seamless glass tubes for optical and laboratory applications, with wall tolerances down to ± 0.2 mm.
• Thermoplastics: Emerging processes spin molten polymers (e.g., PEEK) into high‑performance composite liners for corrosive‑service vessels.

5. Equipment and Process Steps

Centrifugal casting relies on specialized equipment and a tightly controlled sequence of operations.

In this section, we outline the key machinery, mold systems, and procedural steps—enhanced with typical data points—to ensure repeatable quality and throughput.

Molding Machines

• Horizontal Spindle Units

• • Power: 75–300 kW electric motors drive molds up to 2 m in diameter and 10 m in length.
  • Speed Range: 100–400 RPM, generating 20–150 g of centrifugal force at the mold OD.
  • Application: Long tube and pipe production, where axial uniformity matters most.

• Vertical Spindle Units

• • Footprint: Compact designs under 3 m height fit shop floors with limited headroom.
  • Speed Range: 150–500 RPM, ideal for shorter castings with wall thicknesses from 3–50 mm.
  • Application: Bearing sleeves, bushings, and small‑diameter cylinders.

Mold Types

• Permanent Metal Molds

• • Fabrication: Precision‑machined steel or cast iron, often heat‑resistant to 700 °C.
  • Reusability: Up to 500 cycles before resurfacing; maintenance intervals every 200 spins.
  • Surface Finish: Achieves as‑cast Ra 1.6–3.2 µm without post‑machining.

• Expendable Sand/Ceramic Molds

• • Composition: Resin‑bonded silica sand or alumina‑based ceramics.
  • Advantage: Low tooling cost for short runs; accommodates exotic alloys.
  • Limitation: Single‑use only, with typical cycle times of 5–10 minutes per mold.

Pouring Techniques and Temperature Control

1. Mold Preheating

• • Temperature: 300–600 °C to prevent thermal shock and ensure uniform solidification.
  • Method: Electric induction heaters or gas‑fired burners integrated into the mold enclosure.

2. Metal Pouring

• • Temperatures:

• • • Gray Iron: 1 400–1 450 °C
    • Carbon Steel: 1 480–1 520 °C
    • Stainless Steel: 1 550–1 600 °C

• • Technique: Gravity pour into a stationary ladle or controlled “spin‑pour” directly into the rotating mold.
  • Rate: 50–200 kg/s, adjusted to minimize turbulence and gas entrapment.

3. Real‑Time Monitoring

• • Sensors: Infrared pyrometers track mold and melt temperatures with ± 5 °C accuracy.
  • Feedback Loops: Automated controls adjust pour speed and cooling flow to maintain target solidification profiles.

Cooling, Solidification, and Part Extraction

• Cooling Systems

• • Water/Oil Jackets: Circulate media at 10–20 L/min, extracting heat at 5–15 kW per m² of mold surface.
  • Air Quench: In smaller vertical units, high‑velocity air jets achieve cooling rates of 10 °C/s.

• Directional Solidification

• • Strategy: The outer‑to‑inner cooling front promotes a dense OD skin while channeling shrinkage toward the bore.
  • Outcome: Eliminates centerline porosity; yields tensile strength improvements of 20–30 %.

• Spin‑Down and Extraction

• • Spin‑Down Time: 1–3 minutes after pour completion, ensuring full solidification of the outer shell.
  • Molding Cycle: Total cycle times—preheat, pour, cool, extract—range 5–30 minutes depending on part size.
  • Part Removal: Hydraulic or mechanical split‑mold systems open under 50 bar pressure, then eject castings via integrated knock‑out pins.

6. Key Advantages of Centrifugal Casting

Exceptional Metallurgical Quality

One of the most compelling benefits of centrifugal casting is its ability to produce components with dense, defect-free structures.

Due to the centrifugal force exerted during solidification (often ranging from 60 to over 100 Gs), impurities and inclusions are forced toward the inner surface of the mold.

These low-density inclusions can be easily removed during machining, leaving a high-purity outer structure.

• Directional solidification results in fine, uniform grain structures radiating outward.
• Porosity is virtually eliminated, which is critical for pressure-containing components like pipes and liners.

Superior Mechanical Properties

Centrifugal casting delivers parts with outstanding tensile strength, yield strength, ductility, and fatigue resistance.

These enhanced mechanical properties are the result of the homogeneous microstructure and refined grains developed through rapid and uniform cooling.

• Tensile strength can be improved by up to 30% compared to static castings of the same alloy.
• BHN (Brinell Hardness Number) is typically higher and more consistent across cross-sections.

Dimensional Stability and Near-Net Shape

The process enables the casting of parts close to final dimensions, minimizing the amount of post-processing required. This reduces material waste and machining time.

• Wall thickness can be precisely controlled within ±0.5 mm, even on large-diameter parts.
• Excellent concentricity and straightness—especially in horizontal centrifugal castings.

Cost Efficiency for Large Volume Production

Although the initial setup costs (e.g., mold fabrication, machine investment) are relatively high,
centrifugal casting becomes extremely economical over large production runs or in the manufacturing of high-value, long-life parts.

• Reduced rejection rates and less scrap.
• Lower tooling maintenance compared to sand or die casting.
• Fewer weld repairs or heat treatment cycles are necessary.

High Production Speed

Because molds are typically metallic and reused repeatedly, they allow for rapid heat extraction and cooling.

This not only shortens solidification times but also enables faster cycle times per part.

• For example, a typical stainless steel centrifugal pipe (DN200, L=1 m) can be cast and cooled in less than 30 minutes.

Flexible Sizing and Customization

Centrifugal casting can accommodate a wide range of part sizes:

• From small bushings (50 mm dia) to large tubes (>2 meters in length)
• Wall thickness ranging from 5 mm to over 150 mm
• Materials from carbon steels, stainless steels, nickel alloys, to bronzes

Designers can adjust mold speed, temperature, and alloy composition to meet custom application needs.

7. Limitations and Challenges

• High Capital Investment: A turnkey centrifugal cell costs USD 1–2 million.
• Geometry Constraints: Process suits axisymmetric shapes only; complex non‑cylindrical parts require other methods.
• Size & Wall Variation: Mold diameter influences maximum feasible RPM; thin‑walled sections (< 3 mm) risk collapse, while thick walls (> 200 mm) cool unevenly.
• Mold Erosion: High‑speed rotation wears metallic molds, necessitating maintenance every 200–300 cycles.

8. Applications of Centrifugal Casting

Centrifugal casting has become a cornerstone manufacturing process for producing high-integrity, cylindrical, and rotationally symmetrical components across a broad spectrum of industries.

Its ability to deliver dense, defect-free parts with superior mechanical and metallurgical properties makes it especially well-suited for demanding applications.

Industry	Component Examples	Typical Materials
Industrial	Pipes, impellers, pump housings	Steel, ductile iron, bronze
Automotive	Brake drums, flywheels, clutch rings	Cast iron, alloy steels
Aerospace	Jet engine rings, turbine seals	Nickel-based superalloys
Power Generation	Boiler tubes, turbine rings, sleeves	Stainless steel, Inconel, alloy steels
Oil & Gas	High-pressure connectors, couplings	Duplex, super duplex, nickel alloys
Marine	Shaft sleeves, pump parts, water-lubricated bushings	Cu-Ni, bronze, stainless steel
Architecture	Bronze columns, decorative castings	Brass, bronze

9. Comparison with Other Casting Methods

Centrifugal casting stands out among various metal casting techniques for its ability to produce high-integrity, near-net shape components with superior mechanical properties.

However, the ideal casting method depends on multiple factors—geometry, volume, cost, material, and performance requirements.

This section compares centrifugal casting with other common casting methods from multiple perspectives.

Overview Table: Casting Methods at a Glance

When to Choose Centrifugal Casting

Centrifugal casting is the optimal choice when:

• The part is symmetrical and cylindrical (e.g., sleeves, tubes, rings).
• High mechanical integrity and defect-free structure are mandatory.
• Medium to large production volumes justify the equipment investment.
• The part will operate under corrosive, high-pressure, or high-wear conditions.

10. Centrifugal Casting Glossary

Given the highly specialized nature of centrifugal casting, engineers and operators rely on a precise vocabulary to communicate requirements, control processes, and ensure quality.

Below is a curated glossary of common terms and acronyms you’ll encounter in centrifugal‑casting specifications, shop orders, and inspection reports.

Term / Acronym	Definition
I.A.W. (In Accordance With)	Indicates that a part or process must comply with a referenced standard or specification—e.g., “I.A.W. Gould’s 1213 spec.”
FM / FM (Finished Machined)	Denotes that the casting receives a final machining pass to achieve its specified dimensions and surface finish.
RM / RM (Rough Machined)	Signifies a preliminary machining operation, leaving extra stock for subsequent finish machining.
RMS (Root Mean Squared)	A statistical measure of surface roughness; lower RMS values (e.g., 1.6 µm) correlate with smoother finishes.
AC / A/C (As Cast)	Describes a casting left in the condition fetched from the mold, without any post‐casting machining or grinding.
TFA / TFT (To Finish At / To Finish To)	Specifies target dimensions or tolerances to be achieved after all machining and finishing operations.
RFQ (Request For Quote)	A customer’s formal inquiry seeking pricing, lead times, and capabilities for producing specified castings.
UOM (Unit of Measure)	Standard unit in which quantities or dimensions are expressed (e.g., inches, millimeters, kilograms).
LN (Length)	Abbreviation for the length dimension of a part or feature, typically in UOM specified.
QTY (Quantity)	Number of individual pieces or castings requested or ordered.
REF (Reference)	Used to point to another drawing, document, or standard for further details (e.g., “REF DWG 1234”).
PC / PCS (Piece / Pieces)	Denotes discrete countable items—often used interchangeably with QTY in purchase orders or pack lists.
PO (Purchase Order)	Formal document from a buyer authorizing a supplier to provide specified parts or services at agreed terms.
TOLR (Tolerance)	Permissible variation in a dimension, surface finish, or property (e.g., ± 0.25 mm).
BHN (Brinell Hardness Number)	Hardness scale derived by measuring the diameter of an indentation made by a hardened ball under specified load—commonly used for cast iron grades.
UNS (Unified Numbering System)	Alphanumeric code that uniquely identifies the chemical composition of wrought and cast alloys (e.g., G10500 for gray iron, C92200 for phosphor bronze).
AISI (American Iron and Steel Institute)	Organization that publishes steel and cast‑iron designations and standards.
ASTM (American Society for Testing and Materials)	International body that develops and publishes voluntary consensus standards for materials, including centrifugal‑casting alloys and test methods.
SFSA (Steel Founders’ Society of America)	Trade association that establishes best practices, furnace guidelines, and metallurgical standards for steel casting processes.
FOB (Free On Board)	Shipping term indicating that the seller delivers goods aboard a carrier at the origin port; buyer assumes risk and freight costs from that point.
SS (Stainless Steel)	Corrosion‐resistant iron‑based alloy containing ≥ 10.5 % chromium; often used in centrifugal casting for chemical, food, and medical equipment.

LangHe Industry® is committed to delivering both high‑quality castings and clear, actionable information.

Should you need deeper explanations or have process‑specific questions, our technical team stands ready to assist.

11. Conclusion

Centrifugal casting delivers unparalleled performance for cylindrical components, combining mechanical excellence, cost‑efficiency, and production speed.

By leveraging centrifugal force—up to 200 g—manufacturers densify metal, expel impurities, and reduce machining.

As materials science and automation converge, centrifugal casting will continue to evolve, meeting tomorrow’s demands in energy, transportation, and advanced manufacturing.

At LangHe Industry, we stand ready to partner with you in leveraging these advanced techniques to optimize your component designs, material selections, and production workflows.

ensuring that your next project exceeds every performance and sustainability benchmark.

Contact us today!

 

FAQs

Are there size limitations in centrifugal casting?

Yes. While the process accommodates a broad range of diameters (from a few centimeters to over 3 meters), the part must be axisymmetric.

Very small or extremely large parts may require alternate methods due to mold limitations or cost considerations.

What tolerances can be achieved with centrifugal casting?

Typical tolerances:

• Outer diameter: ±1.5 mm to ±3.0 mm (as-cast)
• Wall thickness: ±2.0 mm
• Roundness: <0.5% of diameter
  Final tolerances can be refined via machining, depending on the application.

How are impurities and porosity controlled in this process?

The centrifugal force forces impurities, slag, and gas bubbles toward the bore or inner diameter, which can then be machined away.

This process greatly reduces internal porosity and enhances structural integrity.

Can centrifugal casting be used for custom or low-volume production?

Yes, particularly for components where high strength and metallurgical soundness are critical.

Although tooling and setup can be more complex than sand casting, for critical parts—even in low volumes—the benefits often outweigh the cost.