Just like there’s no one medical measurement that can reflect
a person’s overall health, there’s no single steel cleanness metric that
completely defines the inclusion population in your steel, i.e., how clean your
That’s why TimkenSteel materials scientists developed a set
of cleanness measurements – and the data analysis software to gather them – to
provide the full picture of the oxide inclusion population in steel that
contribute to early failure in engineered components like gears and bearings.
“It’s always been TimkenSteel’s focus to manufacture and
supply steels for the most demanding, highly loaded critical applications,”
said Peter Glaws, senior materials scientist at TimkenSteel. “We want to do it
in the most cost effective manner. That’s why we developed the cleanest
air-melt steel possible and tied it to steel cleanness measurements that are
useful for our customers’ design engineers. It’s what defines Ultrapremium
TimkenSteel’s Ultrapremium process measures oxide inclusions
using automated scanning electron microscopy (SEM) with energy-dispersive x-ray
spectroscopy (EDS) capability. This allows rapid inspection of a larger area,
providing improved understanding of the overall inclusion population. And that
means more meaningful cleanness metrics relevant to component design, allowing
customers to better determine the probability of critically sized inclusions
being located in the high stress regions of the component.
The origin of the analytical tools that resulted in the
development of Ultrapremium technology goes back nearly a decade.
“We developed cleanness analysis methods employing the most
advanced measurement equipment available,” said Glaws. “Traditional measurement
methods are generally incapable of differentiating at higher levels of steel cleanness.
You can’t rely on
standard non-met or mag particle methods to provide sufficient
information. They are just not sensitive enough. Our advanced measurement techniques
provide the means to differentiate steels certified to high quality standards. Our
analytical systems generate data in a useful form so that gear designers or
bearing designers can answer the question: ‘What’s the likelihood of an
inclusion related failure in our component?’”
About three years ago, TimkenSteel started working with a company
that was having problems with the performance of highly stressed gears.
They were using steel that met standard bearing quality specifications, but were
still getting early failures.
“We talked to the customer about Ultrapremium technology and
their metallurgist was intrigued and excited,” said Glaws. “They gave us three
bars to examine.”
Tests showed oxide inclusions were the likely culprit.
Later, the customer used Ultrapremium steel in a test simulating
exposure to the harshest service environment conditions for a set number of hours.
Historically, these tests resulted in premature failures with competitor
materials. With Ultrapremium steel, all the gear sets passed with no failures
or signs of fatigue.
It was an easy call for the customer to switch to
Ultrapremium steel. Not only was fatigue life longer, but Ultrapremium
technology utilizes air-melted steel, which approaches the cleanness levels of remelt or
VAR steels at three to five times less cost.
“People are recognizing that in certain circumstances there’s
opportunity to replace remelt with premium air-melt steel,” said Glaws.
Within the last year, TimkenSteel has talked with 20 to 30
more customers about Ultrapremium technology. More samples are on the way to
TimkenSteel’s technology center.
“Many of our more discerning customers recognize that as
time goes on and they are driven to lightweight or increase power capacity at
current size, they need higher quality steels with better steel cleanness,”