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07-31-2006, 08:21 PM #1
I have a few dies that are made of 4130 that will need hardened soon. I think we're finally done changing the design, and now it's time for the long haul. They measure approx. 30 X 25 X 3 and are fairly accurate at the moment. Is there any precautions I should take to ensure that they don't warp or distort during the hardening process? Is it pretty stable, or does it run all over the place when put to the heat?
07-31-2006, 09:26 PM #2
It isn't non deforming tool steel in any case. That big and that thin means it will likely move around more than you hoped. It will almost cetainly need to be quenched while being held very close to vertical. Can your heat treater do that? You probably aready know it won't get very hard - due to low carbon content. Might think about inserting where it needs to be hard with A2 or the like. Depends on what you expect it to do.
07-31-2006, 09:46 PM #3
Just a far-out thought.. But have you considered nitriding them ? Only bad part is, that nitriding is almost impossible to do any more machining to...
07-31-2006, 10:02 PM #4
That's a job for a heat treater with a BIG salt bath quench. You simply can't do it with an oil quench or a mist. You have to keep the slope of the quench sufficient for the metallurgical changes to occur without excessively chilling the surface.
You will still get some distortion and maybe a soft core but the distortion results with a salt bath quench will be far superior to any other.
I think your choice of material kinda painted you in a corner. I'm sure there are low cost dies steels that distort less than 4130 while providing acceptable hardness. Cost of material, cost of heat treating, distortion control, and hardness toughness are an endless juggle for the metallurgist with all his training and experience.
A shop dweeb or even an experienced tool designer works at a big disadvantage in these situations.
08-01-2006, 07:33 PM #5
Thanks for the advise. I'll pass it along to my boss and see what he thinks we should do from here. I've thought about getting a 2" subplate and bolting it to the bottom to help keep it flat.
08-01-2006, 08:20 PM #6
My Atlas book specifically says this material is suited to "small and medium sections", so I guess you fall outside that one for a start.
You won't be getting this material very hard either, it looks like 54 RC max.
It just seems like an odd choice of material, more suited for say forging chain links, logging tongs or making a gear, bolt or pin.
I can't guess what you mean by "die" - injection moulding?
If nitriding is possible, it would be my guess as the best, but not sure of the application - injection moulding, forming work, (but not if say blanking aluminium...)
08-01-2006, 08:53 PM #7
We're cold forming thin gauage CP3 titanium. Almost like a stamping process I guess, but not at high speeds. Without hardening we've made about 250 parts on it so far and it's holding up well. My boss picked the material, and I'm supposed to make it work.
The depth of form is about .75 so most of the original block is still intact. His first choice was 4340 but the lead-time was too far out. Would that be a better material to work with?
08-01-2006, 09:24 PM #8
If you get more "not tool steel" you should do all heat treating first, followed by initial and in process stress relief at less than tempering temps. By in process, I mean in between rough, semi-finish and finish machining. Easy to get a slab of 4140 or 4340 up near 40 Rc and still be able to machine it with out a lot of heart burn. If you want full "near 40 Rc" at near net form, heat treat after initial rough machining - but still in process stess relieve.
Then there is P20 mold steel, which won't be as hard, but you won't have to screw around with heat treat. Probably more expensive.
If you want to proceed along with the least fuss, run parts in the 4130 until they are not so good and remachine die. Continue doing this until you "use up" the thickness. Heat treating something this size is not a thing to be taken lightly - either by you the end user or any HT vendor you use.
08-01-2006, 09:35 PM #9
What's the machining like on actual tool steel like A2? Is it possible with inserted carbide cutters, or would it require the use of ceramics? I'm delving into a specialty that I don't specialize in, and I don't want to waste company money floundering around.
The VP has been noted in saying, "When have we ever been disappointed that we did the right thing?"
For this job he wants us to do the right thing, and I'm placed in the precarious spot of providing just that. If a different grade of material will hold up better after 10,000+ parts I need to look into what will be involved with making it happen.
Thanks for all the great advice so far. If done right this job will be a big hitter that keeps people employed for years to come.
08-01-2006, 09:42 PM #10
Annealed tool steels machine more or less like "soft" steel. It is after heat treat that something like A2 is harder than you can imagine. Then there is D2 - which is so "slippery" hard after heat treat that it dosent even grind very good.
If you can make 250 good parts in "soft" 4130, why bother with tool steel, heat treating and the BS and costs involved?.
See my last paragraph above.
08-01-2006, 11:34 PM #11
The only reason I'm considering it is the quantity of parts possibly involved. In the next 2-3 years of production requirements it could increase to upwards of 150 per day. With that volume of parts to be made I'd like to know I went the extra step to ensure a repeatable process.
When it's all said and done I'm going to make a duplicate die set for the Oops factor. It WILL happen, and if we're not prepaired, we'll never meet min/max. It will get bad really quick. Without a spare set and about 1 week of downtime we're over 1,000 parts behind...
30 a month for me is steady work for any part number.
08-02-2006, 01:55 AM #12
IMO, your boss didn't do a great job of steel pickin'. One problem with 41xx steels for this part is that they lack nickel, which promotes deep hardenability. The severity of the quench necessary to avoid the pearlite nose on the TT plot is much higher than with a Cr-Ni-Mo steel like 4340, and that's not meant to imply that 4340 is a good die steel. All it means is that the likelihood of warpage is directly related to the severity of the quench.
Obviously you've got quite a chunk of money tied up in this part already, so saving it would be a good thing [img]smile.gif[/img] For what you're doing, it sounds like you need hardness mainly for wear resistance and not necessarily for ultimate strength. I'd investigate the suitability of salt bath nitrocarburizing if it was my part. Its a form of surface hardening, but the temperatures are in line with those used for nitriding (around 1000*F or a bit less) and there is no severe quench. You end up with a surface that's in the low to mid 60's, and that surface has good lube retention properties which can be desirable in a process like you describe. If you do a search for Kolene, it should bring up some good info on the SBN process. Kolene is one of the owners of a proprietary SBN process, and they license it to heat treaters around the country. I've had it done to some parts in the past, and found it will do everything they say it will do.
I dont think you can get the 4130 hard enough to have any appreciable wear resistance without some type of surface hardness treatment. I've made a lot of cold flanging dies in the past from similarly heavy sections of 4140, and after a minimal temper they were seldom above Rc50-51. My guess is that your part will likely be under Rc50 after tempering. That's probably not nearly hard enough for resisting the wear that wants to happen when your Ti slides under high pressure during forming. SBN will give you a surface hardness and friction coefficient close to that of hard chrome, so it should do well for resisting wear. A treater who does the process should be able to look at your part and tell you whether there are certain features that would make the process unsuitable, such as thin highly loaded sections, etc. If it'll work, it should be about the safest process out there for getting the hardness with minimal danger of distortion.
08-02-2006, 06:50 AM #13
I agree A2 cuts like butter for the most part, Even M42 and H13 do not present any real problems to machine in the annealed state, the only thing I did on H13 was cheat on the tap drill size a touch and run it one letter size bigger...H13 will make you think a sharp new tap is a dull old one
08-02-2006, 08:40 AM #14
As John and others have said, anything that big and thin is going to move around. For most of our applications like that, we use a Crucible product call Maxel 3 1/2: http://www.crucibleservice.com/esele.../max3half.html
This is also known as "brake die". We buy the heat treated and drawn material. It's usually a little less than 35Rc which makes is tough, but not impossible to machine. It can be drilled and tapped with HSS. If we have wear spots, those usually get inserted with A-2 or D-2. If the inserts are kept small, say the size of your fist or less, we just make them to size and don't bother to grind. We heat treat in a vacuum furnace and have very little (less than 0.001") distortion.
08-02-2006, 09:15 AM #15
Bright heat treat and annealing is sure nice JR isnt it ??
08-02-2006, 10:29 AM #16
Ron..If accurate dimensioned parts are what your after, I would stay away from 4100 series steel and use a good air hardening series, like A5 or A7 properly hardened and tempered to desired hardness. Always discuss a project with a heat treater before selecting a material. It makes life way easier. Best regards, Mark in Buffalo