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New Way to Make Lighter, Stronger Steel -- In a Flash
ScienceDaily (June 9, 2011) � A Detroit entrepreneur surprised university engineers in Ohio recently, when he invented a heat-treatment that makes steel 7 percent stronger than any steel on record -- in less than 10 seconds.
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In fact, the steel, now trademarked as Flash Bainite, has tested stronger and more shock-absorbing than the most common titanium alloys used by industry.Now the entrepreneur is working with researchers at Ohio State University to better understand the science behind the new treatment, called flash processing.
What they've discovered may hold the key to making cars and military vehicles lighter, stronger, and more fuel-efficient.In the current issue of the journal Materials Science and Technology, the inventor and his Ohio State partners describe how rapidly heating and cooling steel sheets changes the microstructure inside the alloy to make it stronger and less brittle.The basic process of heat-treating steel has changed little in the modern age, and engineer Suresh Babu is one of few researchers worldwide who still study how to tune the properties of steel in detail. He's an associate professor of materials science and engineering at Ohio State, and Director of the National Science Foundation (NSF) Center for Integrative Materials Joining for Energy Applications, headquartered at the university.
"Steel is what we would call a 'mature technology.' We'd like to think we know most everything about it," he said. "If someone invented a way to strengthen the strongest steels even a few percent, that would be a big deal. But 7 percent? That's huge."Yet, when inventor Gary Cola initially approached him, Babu didn't know what to think."The process that Gary described -- it shouldn't have worked," he said. "I didn't believe him. So he took my students and me to Detroit."Cola showed them his proprietary lab setup at SFP Works, LLC., where rollers carried steel sheets through flames as hot as 1100 degrees Celsius and then into a cooling liquid bath.Though the typical temperature and length of time for hardening varies by industry, most steels are heat-treated at around 900 degrees Celsius for a few hours. Others are heated at similar temperatures for days.Cola's entire process took less than 10 seconds.
He claimed that the resulting steel was 7 percent stronger than martensitic advanced high-strength steel. [Martensitic steel is so named because the internal microstructure is entirely composed of a crystal form called martensite.] Cola further claimed that his steel could be drawn -- that is, thinned and lengthened -- 30 percent more than martensitic steels without losing its enhanced strength.
If that were true, then Cola's steel could enable carmakers to build frames that are up to 30 percent thinner and lighter without compromising safety. Or, it could reinforce an armored vehicle without weighing it down."We asked for a few samples to test, and it turned out that everything he said was true," said Ohio State graduate student Tapasvi Lolla. "Then it was up to us to understand what was happening."Cola is a self-taught metallurgist, and he wanted help from Babu and his team to reveal the physics behind the process -- to understand it in detail so that he could find ways to adapt it and even improve it.He partnered with Ohio State to provide research support for Brian Hanhold, who was an undergraduate student at the time, and Lolla, who subsequently earned his master's degree working out the answer.Using an electron microscope, they discovered that Cola's process did indeed form martensite microstructure inside the steel. But they also saw another form called bainite microstructure, scattered with carbon-rich compounds called carbides.
In traditional, slow heat treatments, steel's initial microstructure always dissolves into a homogeneous phase called austenite at peak temperature, Babu explained. But as the steel cools rapidly from this high temperature, all of the austenite normally transforms into martensite.
"We think that, because this new process is so fast with rapid heating and cooling, the carbides don't get a chance to dissolve completely within austenite at high temperature, so they remain in the steel and make this unique microstructure containing bainite, martensite and carbides," Babu said.
Lolla pointed out that this unique microstructure boosts ductility -- meaning that the steel can crumple a great deal before breaking -- making it a potential impact-absorber for automotive applications.
Babu, Lolla, Ohio State research scientist Boian Alexandrov, and Cola co-authored the paper with Badri Narayanan, a doctoral student in materials science and engineering.
Now Hanhold is working to carry over his lessons into welding engineering, where he hopes to solve the problem of heat-induced weakening during welding. High-strength steel often weakens just outside the weld joint, where the alloy has been heated and cooled. Hanhold suspects that bringing the speed of Cola's method to welding might minimize the damage to adjacent areas and reduce the weakening.
If he succeeds, his discovery will benefit industrial partners of the NSF Center for Integrative Materials Joining Science for Energy Applications, which formed earlier this year. Ohio State's academic partners on the center include Lehigh University, the University of Wisconsin-Madison, and the Colorado School of Mines.
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Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Ohio State University. The original article was written by Pam Frost Gorder.
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Journal Reference:
1. T. Lolla, G. Cola, B. Narayanan, B. Alexandrov, S. S. Babu. Development of rapid heating and cooling (flash processing) process to produce advanced high strength steel microstructures. Materials Science and Technology, 2011; 27 (5): 863-875(13) DOI: 10.1179/174328409X433813

Thanks for this very interesting article. See some possible applications for guns, but imagine will need to see whether gun barrel and action steels also benefit from this treatment...

Regards

Hey, look!

We rediscovered case hardening.

Neat! but barrels and actions are low strength steels in the scheme of steels. They are not hardened much and that's why they don't crack when someone engraves the breach with a sharp cornered tool or cuts a dovetail to splice chambers together like a M21. This article is talking about high alloy steels of extreme tensile strength, probably above 200,000 psi tensile strength. For perspective, our early 20th century gun frames are probably around 70,000 psi or so and the barrels might be near 100,000 psi on the really good stuff.

Vicker's had a multiple quenching technique in the say 1880s where they heated a piece of metal to say 950�F, cooled it, heated it again to say 750�F and cooled it. I can find the particulars if anyone is interested. They were addressing the tensile issue. Something similar for cogs where the end result was case colours of 1/32. Is that a typical case colour depth?

Kind Regards,

Raimey
rs

The process described here does not even remotely resemble case-hardening in my opinion. This process gives a through hardening, though it appears to be somewhat limited as to thickness of mat'l it can be applied to.

Worked on a lot of lathes over the years which were described as having "Flame Hardened" ways. This was of course done to cast iron & gave a surface hardness to the part. After the bed ways had been finish machined a very hot flame traveled down their length, followed immediately behind by a spray of cold water. The depth of hardness was dependant upon how deep the critical temp of the metal was reached. This was controlled by how closely the spray followed the flame & the speed of travel down the bed. One might quite easily refer to this as a "Flash Hardening" though.

Case Hardening is of course normally applied to a low carbon steel & requires a prolonged soak at high temp in a carbon rich mixture. This results in the steel absorbing the carbon gases released into its surface. Depth of case is dependant some on temp, but predominately upon time. It definitely is not a flash process.

By any chance were they Monarch lathes? The main lathe in my shop is a Monarch 12CK.

JRB;
Yes indeed some of them were Monarchs. I can't recall for sure now which all brands had the flame hardened ways, but am pretty sure there were others beside the Monarchs. Workwd on a large Sidney for a time which was herringbone geard & am thinking it had the flame hardened ways as well. It was about a 24" swing & with those herringbone gears you could hardly here it run. Except for one bad feature was probably the best engine lathe I ever worked on. That feature was that when you lifted the start lever there was virtually no clutch action, it just came on at set speed all at once.

I have a 50's vintage Monarch 10 EE variable drive toolroom lathe with a factory tracer and turret, burried in the back of a friend's shop. I used it for a good number of years. It needed the ways scraped and trued, maybe just reground the bed would have been in order.

Chuck that is one sweet lathe worth fixing up. If you want I can give you the current address of the Monarch company. Believe it or not they will completely overhaul that lathe although I think shipping from CA would choke a horse. My 12CK is a tool room lathe too. I like it so well that when I die they can bury the Monarch and a set of Starrett mikes with me.