Building on Brass and Bronze
The US Navy and industries including oil and gas, mining, construction, and food and beverage rely on brass and bronze castings to withstand the harsh environments vehicles and equipment endure day-to-day. Brass and bronze are non-ferrous metals that have highly-corrosion-resistant properties, making them ideal for parts submerged in seawater and pumps that move abrasive slurries. C95800 nickel-aluminum bronze, for example, is more corrosion-resistant than stainless steel.
Between the expansion of industries in need of brass and bronze castings, and the declining supplier base of foundries able to serve them, Stainless Foundry & Engineering has relaunched its brass and bronze production offering. In late 2020, we dusted off 75 years of knowledge working with brass and bronze as a core competency. Over the past 18 months, SF&E has honed our production process, developed enhanced processes through project data charters and refined our quality controls.
The highly knowledgeable in-house foundry and process engineers and metallurgists at SF&E have successfully produced parts ranging from C95400 aluminum bronze investment castings under 5 pounds to C95800 sand castings weighing 1,500 pounds. We are happy to report that we are able to take on any brass or bronze order to support the needs of some of the country’s most critical industries.
Prepping for the Pour
Brass and bronze alloys have challenges, particularly with large grains that cause problematic porosity in the castings. At the inspection end, conducting nondestructive testing such as radiographic (X-Ray) and liquid dye penetrant testing can be difficult. For these reasons, the front-end preparation before the pour is crucial for a successful casting.
“When a customer requests a new alloy or one that we haven’t poured in a long time, we take a scientific approach to fit our existing processes and capabilities,” says Mike Porfilio, Director of Quality for SF&E.
Things change over time based on what the team has learned, and we work our large body of knowledge into the technical sheets and the existing project charters for brass and bronze. We consider our process for pouring and provisions for weld upgrade, as well as our final inspection.
Porfilio and the quality assurance team also huddles with the heat treater partners outside the foundry, as this process is different for brass and bronze.
“We want to be sure that the heat treaters understand what we are trying to do and the properties we are trying to make,” Porfilio said.
The Process of Improvement
Pouring a new alloy – or in this case, reintroducing alloys – presents a foundry with challenges.
“The gating and the rigging system are very important, especially when designing the sprue for aluminum bronze,” says Javed Khokhar, Engineering Manager for SF&E. “In the case of investment casting, with every alloy you need to have a separate sprue.”
SF&E relies on 3D software MAGMASOFT® to simulate the casting process so they can test the rigging system design, identify areas where shrinkage, porosity, or inclusions may occur, and adjust all aspects accordingly.
Other considerations set brass and bronze apart. These alloys melt and solidify at different frequencies, leading to turbulence during the melt and pour. When working with nickel aluminum bronzes, this can result in the formation of aluminum oxide gas, which causes slag. The melt for brass and bronze alloys require different techniques and furnace settings.
Multiple trial heats are performed to analyze the microstructure for the initial pour of a production order.
“Over the last 18 months, our brass and bronze project charter has provided key results in order for SF&E to feel comfortable getting back into processing these materials in production volume levels, both commercial and high specification,” said Mitch McCaffery, Vice President for SF&E. “Given the large need in the marketplace, we are happy with the output data the team has achieved to get us ready.”
Inspection Verifies the Process
Quality inspection builds the customer’s trust in the foundry’s ability to cast these alloys. Typically, SF&E probes the customers interested in the new alloy and keeps them informed throughout the casting process.
“While developing the business case for the project charter, one of the items the inspection department was tasked to ensure was to that the non-destructive testing lab had the right tools to complete an inspection,” says Porfilio. “With radiography, for example, you have to use different image quality indicators than with stainless steel, so we bought a new set of ASME E272 non-ferrous reference radiographs.”
Schutte & Koerting, a manufacturer of steam jet vacuum systems, is a longstanding customer of SF&E, mainly with pressure containing castings in stainless steel and various alloyed valve parts. In 2021, they decided to transition a pattern traditionally poured in CA-15 martensitic steel and M30C nickel-based steel to C90500 tin bronze. S&K received the parts, machined them easily, and added them to the end application without issue.
“A lot of other foundries have problems with porosity and consistency from piece to piece, which is most likely caused by the way the patterns are gated and the process by which the casting is poured,” Ruth Pizzino, Production Manager for Schutte & Koerting said in a case study previously published by SF&E. “We have not run into these quality issues with SF&E. I am thinking SF&E is doing something right in the engineering department to have this success.”
Growing Demand
With this handle on brass and bronze production, SF&E is taking orders of all sizes and complexities. When needed, SF&E can convert practically any alloy to brass or bronze to meet the high standards for commercial or high specification structural and sub-assembly parts like those of the Naval Sea Systems Command (NAVSEA).
SF&E has achieved the level of quality for brass and bronze they have been known for in casting stainless steel. If you need expertly cast brass and bronze parts for your project, contact us at sales@stainlessfoundry.com.