Bronze is Back – SF&E Dusts off 75 Years of Knowledge to Meet Growing Demand

When Stainless Foundry & Engineering opened its doors 75 years ago, bronze was one of our core competencies. SF&E worked with multiple military and commercial customers to pour non-ferrous propellers, various pump components, and split case pumps, among other parts.

For the past 20 years, we have primarily served as a high alloy and steel foundry. Due to a growing market need for quality bronze castings, SF&E is back into non-ferrous materials including brasses, bronzes, and other copper-based alloys. Our engineers are merging the foundry’s past knowledge, with today’s best practices, to work toward solving some of the industry’s biggest challenges.

Stainless Foundry & Engineering founder John McBroom (L) and colleagues with brass propellers. Photo circa 1956.

Issues Manufacturers Face

The high strength and corrosion-resistance of brasses, bronzes, and copper-nickel makes them important alloys for parts that will be used in seawater. These alloys also have large grains that cause porosity so they can be problematic. Specifically for high specification jobs, including pressure-retaining parts and Naval Sea Systems Command (NAVSEA) defense parts, it is difficult to conduct nondestructive testing, such as radiographic (X-RAY) and liquid dye penetrant testing (LPI/LP).

Another issue is that many bronze foundries only pour one or two non-ferrous alloys, and can struggle with soundness and casting quality. Manufacturers are looking for bronze foundry partners who can guarantee consistency and deliver within lead times, which, unfortunately, isn’t always the case.

Ramping Up Procedures

At our peak bronze era, SF&E poured 15 different brass & bronze alloys. In the past year, we have reintroduced and poured six different alloys for commercial and NAVSEA customers: C87500 Silicon Brass, C90300 Tin Bronze, C90500 High Tin Bronze, C90700 High Tin Bronze, C95400 Nickel Aluminum Bronze, and C95800 Nickel Aluminum Bronze. We have plans in 2021 to add five to seven more to our repertoire.

Here’s an inside look into the considerations that go into launching SF&E’s second generation bronze offering.

• Melt Practices – The SF&E metallurgy team continues to develop specific work instructions, including melt practices for each grade within each alloy family.

• Processing Procedures – The SF&E foundry engineering team is setting up routings to accommodate the unique requirements of bronze at the molding, cutoff, and grinding stages of production. Partnering with our quality engineers, we are setting up heat treat practices, and non-destructive testing. One of the recently mastered inspection processes we’ve inserted is casting impregnation. This is the process of introducing resin into the part to prevent negative part performance.

• Welding Procedures – SF&E engineers developed specific welding procedures for all appropriate grades and alloys that follow commercial, ASME, and NAVSEA qualifications.

• Testing – We use tools including MAGMASOFT, which runs detailed profiles on sand and investment molds, that can predict feeding and porosity while assessing the thermal balance in tooling and providing autonomous optimization of casting quality, yield, and much more. Our metallurgy team uses two spectrometers, set up specifically for non-ferrous alloys, to test and verify material quality.

• Contamination Prevention – SF&E pours over 250 different ferrous and non-ferrous alloys. We carefully control the sequencing of the alloys and keep them physically separated to prevent contamination. As our volume increases, we will dedicate some parts of the foundry exclusively to brass, bronze, and other non-ferrous material production.

• Trusted Partners – We know we can’t be experts at everything, so we are actively qualifying vendors and partners who can make us more efficient at services including heat treat, machining, and non-destructive testing.

Same Dedication to Service

Non- ferrous customers benefit from the optimization created by SF&E’s multi-year Throughput Improvement Project, which currently achieves average commercial lead times of 5 to 7 weeks. Non-ferrous customers range from existing ferrous customers, expanding their work with us to include non-ferrous, and new customers looking for a stronger bronze foundry. SF&E knows that the best way to serve our customers is to continuously develop and improve ourselves. For more information on our bronze capabilities, please contact sales@stainlessfoundry.com.