Continuous Cast vs Centrifugal Cast Bronze: What's the Difference?

If you're buying bronze bar stock, you'll encounter two main casting methods: continuous casting and centrifugal casting. Both produce quality material, but the process differences affect grain structure, tolerances, cost, and suitability for your application. Here's what you need to know.

How Continuous Casting Works

In continuous casting, molten bronze is poured into a water-cooled graphite die and solidified in a controlled, uninterrupted process. The result is a long, uniform bar with consistent grain structure throughout its length. This process is ideal for producing standard round bar, hollow bar (tube), and flat bar shapes in high volume. Most bronze bar stock on the market today is continuously cast.

How Centrifugal Casting Works

In centrifugal casting, molten bronze is poured into a spinning mold. The centrifugal force pushes the dense metal outward while impurities and gas porosity migrate toward the center bore, which is later machined away. This produces a very dense, clean outer structure. Centrifugal casting is typically used for large-diameter hollow shapes — tubes and rings that would be impractical to produce by continuous casting.

Grain Structure and Density

Continuous cast bronze has a fine, uniform grain structure with consistent properties from OD to ID and along the entire length. Centrifugal cast bronze has a directionally solidified structure with the densest, cleanest material at the OD — exactly where bearing surfaces are typically located. For critical bearing applications in large diameters, centrifugal casting can offer superior performance.

Dimensional Tolerances

Continuous cast bronze is produced to tighter as-cast tolerances per ASTM B505 — typically a few thousandths of machining stock on the OD and ID. This means less material waste and less machining time. Centrifugal castings have wider as-cast tolerances and require more finish machining, adding to the total cost. For standard sizes, continuous cast is almost always the better value.

Size Range and Availability

Continuous cast bronze covers the widest range of standard sizes: solid bar from under 1" to over 12" diameter, and hollow bar in hundreds of ID/OD combinations. It's the most readily available form from any bronze supplier. Centrifugal castings fill the gap for large diameters — typically 6" and above for tubes — and for custom OD/ID combinations not available as standard continuous cast sizes.

Cost Comparison

Continuous cast bronze is more economical for standard sizes. The high-volume, automated process keeps material costs low, and tighter tolerances reduce machining cost. Centrifugal castings carry a premium due to individual mold setup and lower production rates, but they can be more economical for large, non-standard sizes where a continuous cast equivalent would require excessive machining from oversized stock.

When to Specify Continuous Cast

Use continuous cast bronze for standard bushings, bearings, valve components, pump parts, and any application where the required size is available as a standard continuous cast shape. This covers the vast majority of bronze bar stock orders. Common alloys like C93200 (SAE 660), C93700, C95400, and C86300 are all available as continuous cast bar, cut to length from US mills.

When to Specify Centrifugal Cast

Specify centrifugal casting for large-diameter tubes and rings (typically 6"+ OD), custom ID/OD combinations, and applications where maximum density at the bearing surface is critical. Centrifugal castings are common in steel mill bearings, large pump wear rings, marine stern tubes, and heavy industrial equipment.

Bottom Line

For most applications, continuous cast bronze is the right choice — it's more available, more affordable, and produced to tighter tolerances. Reserve centrifugal casting for large or custom sizes where it provides a clear advantage. Both casting methods are available through Triton Bronze & Metals, with material sourced from US mills and mill test reports available on request.