Specialty alloys go mass market in wrapped bearings

Features - Materials

Technology developed for smartphones allows Materion to roll out a high-strength, niche alloy to a much wider industrial marketplace.

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Snicker all you want the next time you see someone holding his smartphone at arm’s length to take a self-portrait. Selfies on Flickr, Facebook, and Twitter are shrinking load-bearing systems in commercial and consumer vehicles while increasing capability, slashing weight, and cutting fuel use. Well, not the photos themselves, but the technology that goes into them.

Plant investments, equipment upgrades, and processes that specialty alloys company Materion developed for springs in smartphone cameras turned out to be ideal for converting a tough bronze alloy into thin sheets. ToughMet, a copper-nickel-tin alloy that had only been available to those willing to mill thick-walled tubes or rods, is now available in wrapped bearings, thanks to smartphone-inspired rolling processes.

“If we didn’t have a world-class strip mill for beryllium copper, we wouldn’t have known how to do this,” says Dave Krus, product marketing director for Materion’s Engineered Products Group. He adds that the company upgraded its Elmore, Ohio, rolling facility to make thin ToughMet alloys for electronic gadgets, but that the processes came from beryllium copper expertise.

“The same engineers who figured this out for beryllium copper were the ones who figured it out for ToughMet. We’ve got a whole lot of brain power and engineering experience here. Without it, we wouldn’t have a flat ToughMet product,” Krus explains.
 

Origins of BowMet bearings

About a year ago, Materion officials met with the owners of British bearings specialist Bowman International Ltd. Krus says he had been considering ways to expand ToughMet’s market now that it had a thin product, and Bowman was looking for new materials for high-performance wrapped bearings – round, hollow cylinders that support rotating parts in equipment such as boring-shaft supports in mining equipment or driveshafts in cars.

“We met by chance, but we were both looking to do the same basic thing at the same time,” Krus says. As a materials company, Materion wasn’t familiar with all of the end markets that could benefit from stronger bearings. Typically, the company produces parts to order and wasn’t set up to support a wide range of standard sizes and shapes. “When people did order from us, we’d have to get exact specs from them. We couldn’t produce to a standard size or part number.”

Bowmet Bearings

  • Static load: 120,000psi (820N/mm2)
  • Dynamic load: 50,000psi (340N/mm2)
  • Coefficient of friction: 0.24 dry, 0.04 oiled
  • Max sliding speed: 10fps dry (3m/s), 33fps oiled (10m/s)
  • Operating temperature: -450°F to 570°F (-250°C to 300°C)
  • Hardness: HRC30

Early this year, the companies signed a distribution agreement for Materion to supply ToughMet metal to Bowman and for Bowman to create and support a catalog of wrapped bearings under the BowMet brand name; a deal Bowman calls the biggest development in wrapped bearings in more than 70 years.

The new mass-market applications for ToughMet come after nearly two decades of development and sales of the metal.

Materion, formerly Brush Wellman, has been selling ToughMet since 1997, when it built a casting plant in Lorain, Ohio, for the material. Krus says within a few years of its release, a few customers began asking for thin sheets of ToughMet for some electronic devices, so Materion began experimenting with ways of rolling the material in Elmore. After several years of engineering trials, the company figured out heat-treatment and cold-treatment steps to get the metal to roll into sheets, leaning heavily on its expertise in rolling beryllium copper.
 

High strength, lubricity

Because basic bronze formulas are non-corrosive, require little lubrication, and tend to be easy to form, designers often choose them for lighter, load-bearing applications. However, standard bronze isn’t strong enough to handle the strain of heavy loads, so vehicle and equipment producers generally turn to steel. Krus says steel is an imperfect substitute because it requires more lubrication. Designers had imperfect choices: create oversized bronze bearings, adding weight and taking up more space to get the needed weight and lubricity levels or switch to steel and add a lubrication system. Either way, system sizes and weights go up and fuel economy goes down.

BowMet bearings can handle 50,000psi dynamic loads in wrapped bearings (120,000psi static loads). Equivalent stainless steel wrapped bearings tend to max out at about 20,000psi dynamic loads, 37,000psi static. In addition, the BowMet sliding speeds, dry or lubricated, are much higher than the equivalent steel bearings. Higher weight and lubricity ratings allow manufacturers to design smaller load-bearing systems with higher load ratings, saving space and weight.
 

From niche to mainstream

As a milled material, Materion’s ToughMet has been popular only in very demanding conditions where price is secondary to performance. Many aircraft manufacturers spec ToughMet for landing gear on planes. The Mars Rover features ToughMet in its wheel bearings. Equipment makers for the mining and oil and gas industries also have used the metal extensively in drilling equipment.

A spinodal-hardened bronze, ToughMet’s atoms line up in a complex crystalline structure that gives the metal its high strength and high lubricity. But getting that internal alignment isn’t easy, since it requires a proprietary vertical casting process and exacting cooling and mixing steps. The copper, nickel, and tin in the alloy solidify at different temperatures, so creating a homogenous material requires a lot of metallurgical know-how, Krus says.

Finished metal comes out of the casting process in billets or bars. So customers had to mill cylindrical bearings from larger heavy tubes, wasting as much as 75% of the material they purchased.

“At one point, we approached off-highway agricultural equipment producers. They tested ToughMet, and it worked great. But then they found out how expensive it was,” Krus says. “We could get into mining equipment, where a bearing failure could take a multi-million-dollar piece of equipment out of service for days. But with anything lighter, it was really hard to justify that cost difference.”

The customers that were able to justify the extra expense generally looked at the long-term costs of operating equipment. While costlier to purchase than steel and other alternatives, ToughMet lasts three to five times longer in the field. Between maintenance costs, replacement parts, lost man hours, and extra lubrication, estimates are that some heavy duty equipment operators could save about $2,600 for every 8,100 hours of machine use. Those savings could go up dramatically with the BowMet bearings.
 


 
 

Thinner metal sheets

Creating a wrapped bearing out of ToughMet costs one-third the price of milling the equivalent part from a rod of the material, Krus explains. He still expects most of the demand to be on the heavier, commercial side of market where companies can justify the extra cost if it means higher tow ratings, vehicle weight savings, or improved reliability.

Lowering those initial costs makes the material available to a much wider base of users, he adds. In some cases, he expects BowMet bearings will cost only a few cents more than equivalent steel ones. Early BowMet orders have gone to race car producers, aerospace companies, and agricultural equipment makers.

Typically, Materion doesn’t have its products widely available in mainstream parts catalogs. Its customers come to the specialty materials company when all off-the-shelf options fail.

Krus says that’s a big part of what makes this project special for the company. “We’re excited to see who’s going to be interested in using this.”

 

Materion
www.materion.com

Bowman Intl. Ltd.
www.bowman.co.uk

 

About the author: Robert Schoenberger is the editor of TMV and can be reached at 330.523.5381 or rschoenberger@gie.net.