Cutting nickel steel

First, this post is going to be somewhat vague as I'm under an NDA and can't give much detail.
That said, I have a need to cut 1/16" to 1/4" thick slices off of
irregularly shaped objects composed of 5-10 percent nickel, 1-2 percent carbon, a few trace elements, and the rest iron. Annealing is not an option--they have to be cut as is. The objects may be somehwere in the range of 1 to 5 inches in diameter. The kerf has to be as narrow as possible.
So far I've been using a diamond lapidary blade and oil coolant but it's really slow going and judging from the noises it makes the saw is not happy. It'll cut through a lump of slag in a minute or so, but one of these puppies takes a half an hour with the same setup.
I was wondering if anybody had any ideas on a better way to go.
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Iron actually chemically eats away the edge of diamond, so you really should not use it on iron.
What they use for iron meteorites (which are very similar to what you describe) is a cubic boron nitride blade: http://www.gravescompany.com/CBN_Blade.htm
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snipped-for-privacy@removethis.ix.netcom.com says...

I was thinking about trying a boron nitride blade, but reports I'm seeing say that they don't seem to work any better than diamond on the meteorites. On the other hand, the same people reporting that also reported that the POS blade that I started out with was decent and the one I replaced it with, that is working much much better, is crap, so . . .
I guess I should try one (the boron nitride that is) and see how it goes.
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On Fri, 15 Jul 2011 01:51:40 -0400, J. Clarke wrote:

Wire EDM? It'll still take time, but the kerf will be narrow!
--
Tim Wescott
Control system and signal processing consulting
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Wire EDM can slab it off at around 25 in.^2/hr., with a kerf on the order of 0.020 in. At those speeds, you'll have a heat-affected zone a couple of thousanths deep, so that may be a consideration.
--
Ed Huntress

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says...

Interesting thought, but sounds expensive. I don't think we've got the budget for it.
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I don't know what shop time is on a wire EDM these days. It was $45/hour last time I looked, but that was quite a while ago.
--
Ed Huntress



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Perhaps it could be sliced with an abrasive water jet. That might cost less than EDM.
Best Regards Tom.
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says...

Hmm, something to look into. Might be cheaper than me standing in front of a saw. Thanks.
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My guess is that it's the best deal. I don't know what they charge for waterjet these days. As for laser, expect a very rough cut on the downside of the workpiece, and a much thicker heat-affected zone (HAZ).
Wire EDM can really rip when you're just cutting straight lines are you aren't looking for blanking-die accuracies. It will easily hold a couple of thousandths, and it can do better than a tenth, although that really slows you down.
--
Ed Huntress




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The use of diamond for cutting ferrous materials is NOT acceptable. Diamond is dissolved by iron when it is subjected to heat, such as in grinding.
Harold
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I've used a Leco water-cooled abrasive cut-off saw for metal sample preparation. I thought that lapidary saws were used mostly for stone and ceramics.
After cutting off sample pieces we would mount them in a thermoplastic compound and polish them on a Buehler machine. The final step used diamond paste. Samples were etched (if necessary) and the samples went on for further analysis (grain structure, etc).
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And stubborn old gold alloy dental crowns. After the slide hammer failed she went in with a chop saw. Two hours I'll never forget. She gave me the remains which otherwise would have gone out with the used sharps. It had been center drilled for a root canal and might make a grotesque Goth/vampire necklace were I so inclined.
In June I made -one- appointment for the whole month of July. Guess when the dentist has to install the new crown.
jsw
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Cringe... It sounds like an Edgar Allan Poe story, but maybe you're though the worst of it.
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Thanks to the root canal the tooth had no feeling. The worst pain was in my butt, specifically the wallet area.
The old crown might make a good lid for a poison ring. I could mold the roots to grow around my finger.
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The ring sounds a bit gruesome, but maybe you'll start a new trend in body art. <g>
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I only thought up that stuff to one-up the goth daughters of lady friends.
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snipped-for-privacy@cox.net says...

Just a little more information--the saw wasn't happy because the blade was decentered. Crappy blade--lasted two cuts. The replacment was a different brand and it's cutting much much better. Not great but better.
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J. Clarke wrote:

I have done some diamond grinding of steels. I agree that high-speed grinding of steel damages the diamond by getting it hot enough to alloy. WET grinding at lower speeds, however, works because the diamond is kept cool by the fluid, so the alloying is at least slowed to a minute fraction. You lose speed of progress on the cut by slowing down, but diamond can still remove steel at a steady pace. It just about has to still be faster than wire EDM and both can accommodate thin kerfs. Abrasive waterjet can't do really thin kerfs, and will not produce flat faces of the cut. Not much can beat the cutting rate of waterjet, however. You can probably do your cuts in 2-5 minutes each, depending on part size!
Jon
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