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Carbon Steel
Thursday | 08 September, 2016 | 12:53 pm

Pure power

By Corinna Petry

Above: TimkenSteel’s qualified gear quality bar products begin to take shape at the jumbo bloom vertical caster in Canton, Ohio.

TimkenSteel air melts steel so clean it resists fatigue and failure in extremely tough conditions

September 2016 - Products made from forged steel bar are put to the test through critical applications that are airborne, such as fighter jets, and deep in the ground, such as mining and petroleum extraction. Used in these circumstances, the material must not fail: You don’t want planes grounded and oil rigs halting production.  

TimkenSteel has stayed relevant for a century. Yes, it still makes special-bar quality billets and bars for use in bearings and gears, but the requirements and demands that have been imposed on the material over that time have increased exponentially.

Gear life depends on many factors and steel cleanness is a critical one. TimkenSteel has 100 years’ experience producing clean steel for gearmakers. 

When one customer needed to supply power transmission systems that has to fit within a space no larger than a fist, TimkenSteel assessed all of its processing steps—from melting steel and casting billets, rolling bar and forging, heat treating and finish machining. 

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Finished gears are examined through quality verification protocols at TimkenSteel’s technology center.

Tough testing

After undergoing a thorough engineering analysis, TimkenSteel proposed that inclusions greater than 10 micrometers (about one-fifth the diameter of a human hair) would represent a significant fatigue risk and reduce gear performance. The company used its proprietary engineering tool TimkenSteel Virtual Component Fatigue Model (VCFM) to illustrate the impact of steel cleanness on the performance of the gears. Model runs were fed actual inclusion data from TimkenSteel material and two competitors. Each producer was evaluated with 32 samples.

Of all those samples, only two—produced by TimkenSteel—exhibited any inclusions greater than 10 micrometers, while virtually all of the 32 samples from its peers exhibited many inclusions greater than that 10-micrometer size.

Based on the modeling analysis, TimkenSteel produced Ultrapremium material for the customer’s gears, which tested 10 gear sets to 100 hours under accelerated harsh conditions, with intermittent disassembly and inspection. Based on historical test results from the peer competitors, the customer anticipated multiple failures under these harsh conditions. All 10 gear sets made from TimkenSteel material passed with no failures or signs of fatigue.

As a result, the customer is specifying Ultrapremium for these high-power dense applications.

Carry that load

Ultrapremium presents TimkenSteel with “an opportunity to engage more closely with customers at the design level for highly loaded components,” says Ray Fryan, vice president-technology and quality at the Canton, Ohio-based producer. 

The technology TimkenSteel has developed isn’t so much about the grade chemistry, because it can apply to virtually any chemistry. Rather, “it’s a tight set of controls in manufacturing and around the quality verification. Those two things together put steel at a purity comparable to remelted steel, vacuum arc remelting and vacuum induction melting,” he says.

The remelt processes are typically performed by small niche players that can demand a premium for the product. But TimkenSteel can produce 2 million tons of steel annually and make an air melted product at much lower cost.

Being integrated, TimkenSteel has control from the initial melt to ladle refining, from reheating to bloom production, from strand casting to the rolling mill.

“We can make a heat from a caster in a little over an hour. The value proposition is there are certain control points in air melting of steel that makes or breaks purity level. We studied this for a long time,” Fryan says. “The most recent development is an intended marrying of what we learned from our process and the ability to measure and characterize it. We put it together and called it Ultrapremium.”

More power

The upshot is a highly pure steel “that transmits more power in a smaller space. We had a [American] customer that had a 400 hp right-angle gear drive system, transmitted through [a piece of equipment] as big as your fist.

“They are good gear designers that understand all the manufacturing and design levers to make their gears tolerate as much power as possible,” Fryan says. “But the missing link was material. They were buying standard gear-quality steel that had been used for decades but was inadequate to deliver what they needed. They were experiencing failures in accelerated lifecycle tests with supplied steel.”

The customer consulted TimkenSteel. “We told them about our remelt equivalent and told them it could help,” says Fryan. “We gave them material, they manufactured 10 gear sets. All 10 passed. They showed no wear at the end of the accelerated tests.”

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Hot bars solidify on a cooling bed at TimkenSteel. They are later tested for how “clean” they are for gear manufacturing.

Seeing potential

Fryan says TimkenSteel is promoting Ultrapremium to upwards of two dozen customers. “We are following leads. We have a European customer with American operations—they are intrigued. They want to put more power through existing transmission designs but are limited by material. Our material could be a solution.”

By using Ultrapremium in existing designs, Fryan suggests “an automotive customer could avoid hundreds of millions of dollars worth of retooling and plant redesign costs.” The European customer plans to benchmark Ultrapremium in its product, he says.

If TimkenSteel does get buy-in from a major customer seeking sufficient volume of Ultrapremium, Fryan is certain there is nothing to get in the way. “We have the manufacturing capacity. If there was a testing capacity consideration, we would add lab assets to do that,” he adds. “It’s a very scalable model.”

Steel versus 3-D printing

TimkenSteel is very aware of the developments in the field of additive manufacturing and advanced materials and process technologies, and sees them both “as complements to our processes, or they could be very competitive threats.”

To date, the volume that’s able to be produced “is amenable to small-volume application and to things with complex and sophisticated part features. People that do prototyping will adopt it. It’s a strong strategic fit,” Fryan says. 

However, “high-volume part production may not be amenable. Steel is still very versatile; it’s the most important engineering material on the planet, and the most economical.”

He suggests additive manufacturing may eventually become a technology disruption “but replacement of high volume steel-based products are not likely to occur in my lifetime. A lot of factors are working against it. The powder material necessary to feed the 3-D printing; the cost is much higher than rolled and forged steel; the printing process is very slow—the highest number I heard is about 1 kg per hour.” 

Bulk rolled steel bar and powder metallurgy have competed for applications for decades, Fryan says, and numerous structural components have long been produced  from powdered metal. But there is a “boundary management driven by performance and economics. Additive will have this same boundary competition with bulk steel but it is a niche play today.”

Weight versus power

The tension between the need to lightweight parts for fuel efficiency and the need for power-dense material to provide power is a big part of that ongoing discussion.

National laboratories are conducting research on highly un-densified additive manufacturing techniques for aerospace applications, trying to get very lightweight, like sponge structures or micro-trusses that get printed and joined together. “So for airframe structures, there is absolutely a place for additive there,” Fryan says. “But for high volume power transmission and power transfer, additive becomes less competitive.”

Just the same, competition is fierce in materials. “Think about what happened with the aluminum and steel competition in automotive body applications. The F-150 was the shot heard ’round the world,’” he comments. 

People are also working on downsizing the rest of the car. “The engine, the crank, transmission, driveline—all those things have design limits, and are driven by engineering of steel from which they are made.

“To move system design and mass, it’s complicated. It’s a nonlinear design process that requires deep collaboration between steel producers and design engineers,” Fryan says. “Then you think about the next 15 parts touched by that process.”

Meanwhile, TimkenSteel will talk to customers about running Ultrapremium in their next design cycle, and Fryan is fairly optimistic customers will want to test it out. “We see the value of talking broadly our about capability and we are prepared to solve complex problems.”

Quoting the wildly successful hockey player Wayne Gretzky, Fryan says, “That’s where the puck is going to be and we are ready.” MM

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