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09-19-2011, 02:57 AM #1
Steel for hot working press dies (800 deg C)
I am in need of some type of steel (metal) that I can use on my hydraulic press at a temperature of approximately 800 deg C (clamshell heater). Pressures around 3000 PSI compression, no parts under external tension.
For a production ready fixture, plans call for Nimonic 80, which is pretty dang pricey....like nuclear engineering pricey (and I'm just judging from my gut here, I haven't even called to get a real quote) I only need two pieces that are 2" diameter x 2-3" long, and one piece with an ID of 2" and a length of 2" or so to use as a bushing (wall thickness of 1/4, no precision fits) Not something I can really call Special metals up and order...or at least for a reasonable price (to me at least, as I'm on a bologna sandwich budget).
I think a lot inconel grades of steel should work for these pressures and temperatures, but would prefer to defer to suggestions.
This is not a production process, but yet something I would be doing as a hobby...I don't need certs, all I need is something that is not going to mushroom at my temp/pressure! All parts are physically contained, so it's not like something is going to bend and blow out.
Any suggestions on a suitable material? Or even better...anybody got any drops of Nimonic!!!
09-19-2011, 09:12 AM #2
You can probably get away just fine with 4140 or 4340.
Blacksmiths use these alloys for hammer tooling, which has to hit 2300 F steel a couple of hundred times a minute, and it holds up for years.
No, its probably not as good as Nimonic 80, but its a lot cheaper and more available.
If you are expecting hundreds of thousands or even millions of uses from this tooling, then, sure, buy the real stuff. But for developing tooling for small runs, 4340 is more than adequate.
Frankly, I have made a fair amount of short run tooling for my hydraulic press, which, being an enerpac, goes above 3000 psi without blinking, from plain old mild steel, and used them on stainless steel parts that were probably 2200-2400 degrees F for runs of hundreds of pieces. Sure you will get some degradation of the tooling over time, but if you are not building parts for the space shuttle, its adequate.
09-19-2011, 09:58 AM #3
09-19-2011, 01:55 PM #4
Since you would fully understand, I'm considering building a mokume gane press for precious/base metals. The parts in question would actually be functioning AT the high temperature, not just contact temperature.
The whole apparatus would be heated to the bonding temperature (mokume gane billet as well as the two pieces of high temp steel and a bushing to contain the billet). The one advantage is that all of the items would either be in a reduction or neutral environment, no oxidation allowed, but my feelings were similar, that I should be able to get away with a quality steel, or even stainless...but was hoping to hear from experienced people.
I know that the forging temperature for 4140 ranges from 1700 up, but wasn't sure how much strength it retains at temperatures below 1700.
I think I'll probably give it a try with 4140 as I've got a bunch of 2" drops. If I find it's deforming too much, then I can try upgrading to a better steel, even if it's still not a superalloy!
09-19-2011, 08:58 PM #5
Just found a little more information...
304 SS yeild strength at 800 deg C is around 18000 PSI
4140 at approx same temp is around 12000 PSI
either way, for a few uses, 4140 should work fine at my pressures
09-20-2011, 08:46 AM #6
Well, from a standpoint of experience, I can tell you that when I use 4140 tooling to beat on stainless, the stainless moves and the 4140 doesnt...
Even when both are pretty hot.
Stainless is funny stuff, not as "hard" as you would think, especially when you get it warm.
I wouldnt use it for tooling, unless you are working with chemical environments that require it.
As for making mokeme gane with heated dies- never heard of doing it that way- is this something you are inventing, or is it proven tech?
I know two of the top mokeme guys in the world, and neither of em does that.
One uses very high tech inert atmosphere ceramic furnaces, the other uses propane forges that are carefully built to create neutral atmospheres- but, as far as I know, both do all their press work out in the ordinary atmosphere. They seem to put a lot more emphasis on very large tonnages then they do on heated dies- as in 200 tons and up.
09-20-2011, 09:54 AM #7
It's proven design, mostly for repeatability. It's basically doing it in an inert atmosphere, without taking it out of the furnace to press it together and laminate the sheet.
It was published in a book, but I guess the guy who built it had a $250,000 grant from a supplier or something.
I sold my anvil because it was in the way, now I'm sad because I want it again.
09-20-2011, 07:49 PM #8
I have that book. That method looks alot harder than it needs to be. I have done mokume under my press and under the power hammer. The press was easy. I made the flat dies out of s7. I have used lots of mokume but have been buying it or at least I used to buy it. With gold at 1800 bucks demand for stuff like this is pretty small..
09-20-2011, 09:46 PM #9
With silver at $40, demand is small :-) I'm still thankful that I have a few pounds from back in the day when it was $6/oz
Jewelry is nothing more than a hobby. If I someday break even, I'll be overjoyed.
09-24-2011, 01:53 PM #10
I've seen a couple of different folks start their mokume billets in a small clamp that goes in the furnace. The clamp was just two pieces of mild steel plate with holes in the corners and some bolts through them. Pulled it out of the furnace, tightened the bolts until they started twisting, then start hitting it with a big sledge. Throw out the steel plates when they get beat up.
I think it was more of a fixture to hold the stack together until they got it stuck than a pressure device. If I were going to put it under a press I'd probably dispense with the bolt tightening and stick it right in the press.
09-24-2011, 06:12 PM #11