reduce warping in machined o1 parts before heat treat, normalize or anneal prior?

I milled some round 01 into rectangular parts 3/8 by 1/4 by 1" long. They have some grooves and half rounds cut out the sides. They look as if they could warp a little during hardening. Would a normalize or anneal process help before hardening? I understand normalize as heating about 100F above critical. Is that correct? These are my parts so I have no heat treat guy to rely on.

Thanks.

lowCountryCamo said:

I milled some round 01 into rectangular parts 3/8 by 1/4 by 1" long. They have some grooves and half rounds cut out the sides. They look as if they could warp a little during hardening. Would a normalize or anneal process help before hardening? I understand normalize as heating about 100F above critical. Is that correct? These are my parts so I have no heat treat guy to rely on.

Thanks.

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some people use A1 or A2 air hardening steel instead. the theory being it is less likely to warp. it requires a furnace with a automatic temperature controller which most newer furnaces can be programmed for heat treat cycles. maybe talk to heat treat guy and ask what metals warps less ??

oil and water hardening steels will have more stress and distortion than air harden as a rule.

The advice to use A2 to reduce warping is a good recommendation. I have used it a moderate amount and found it tends to warp very little.

I also use O-1 often and occasionally W-1 and have read a modest amount about its use. I have not come across the idea of annealing after machining and prior to hardening to reduce warpage. But, I can tell you that the technique you use to quench will definitely make a big difference in the distortion you experience. Recently, I was making some long skinny parts out of 0-1 for watch-repair screw drivers---the replaceable blades. As a demo to the customer, I heated up a blade after machining to cherry red and just dropped it into the oil bath. It took on a very visible warp. Then with another blank, heated it to the same temp and held it in tongs and plunged it rapidly lengthwise and thrust it back and forth rapidly as it cooled. (He thought the smoke was cool BTW) The second blade was nice and straight. After temper to a light/med yellow it were much tougher and better proportioned than his expensive Bergeon blades. Untempered, the blade snapped easily with just holding it in my fingers---used the warped blade for that demo. He ahd me make quite a few blades once he could see the difference between what Bergeon is selling now (I'll be they were better 30 yrs ago) and custom blades made using very basic "blacksmithing" techniques. The factory ones came in a prettier package though.... ;-)

Sorry for the rambling reply. But the demo is typical of results I have observed many times.

Denis

DG is right on target. Dropping the part in sideways so one side cools a few milliseconds sooner can really make it curl up.

I'm still using the Bergeon screwdrivers I bought around 1967. They are excellent. Of course, they are probably made in China now.
Bill

9100 said:

DG is right on target. Dropping the part in sideways so one side cools a few milliseconds sooner can really make it curl up.

I'm still using the Bergeon screwdrivers I bought around 1967. They are excellent. Of course, they are probably made in China now.
Bill

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His were made of some sort of SS cheese. They very easily bent like a boat propeller (well not quite that badly but it was the best written visual image I could come up with) when used on some screws that were fairly, but not unreasonably, tight. The ones we made could take all he could apply and were unscathed. They did not look too bad either as I find the oxidation colors attractive. And a few strokes on a fine diamond stone had the facets gleaming. I am not surprised that the ones you have from the 60's are excellent.

Denis

The only way that normalizing is going to help you is if you rough machine, normalize, then (semi) finish machine before heat treat.. Lets most of the warpage that would have occured in hardening, happen between the 2 machining operations..

I met a guy who took the time to walk me through his shop once...Very smart man... He would process his parts, gaging and anticipating the stress he would induce into the part etc, by making cuts in specific regions of the material to get the part to curl up but leaving enough stock on the piece so that after it was done warping he could machine the rest of the part complete without annealing or normalizing. The parts he was showing me were very small tight tolerance polymer parts for the optics industry. He isn't that much older than I am, but far more intelligent as far as machining goes.

allloutmx said:

but far more intelligent as far as machining goes.

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It's just too easy sometimes. Takes the fun out of it.

O-1 grinds nice, gets fairly hard, and is cheap. Other than those, I can think of no other redeeming qualities. If you got a part that you want minimal warpage on, use A-6. That is the least warping, heat treatabel material.
JR

JRIowa said:

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O-1 grinds nice, gets fairly hard, and is cheap. Other than those, I can think of no other redeeming qualities. <>
JR

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I can think of one more: Convenience. It is so quick and esay to harden and temper with a simple torch and oil quench. No fussing with a heat treat oven, SS bags or inert gas environment. From the time you are finished machining til the part is hardened and tempered might be 1-2 minutes or so. Not saying, by any means, that it is a substitute for the many specialized alloys available. It is just a go-to alloy for making simple things like punches, pins, screw drivers, gravers not to mention -
- Blanking dies
- Drawing dies
- Machine ways
- Cams
- Forming dies
- Plastic mold dies
- Coining dies
- Gages
- Shear Blades
- Trim dies

The larger pieces listed above would not be easily torch hardened it is true. But it is a widely used and versatile alloy.

Denis

I make dozens of small artists' tools out of O1 each year--stock is 1/8" X 1/2" and is Starrett--the "no-name" stuff on sale at Enco was brittle. The tools have two 90-degree bends in them, sort of like those little zed-shaped screwdrivers.

Dennis is right about the quench technique--keep it moving rapidly in the oil until cooled, although I usually hold the pieces vertically in the tongs. Having the oil bath at around 100 degrees F helps too.

Annealing O1 requires a digitally-controlled HT oven, as it must cool down at rate much slower than ordinary "turn it off and leave door shut." The recommended rate varies between 27-50 degrees F PER HOUR from annealing temp (around 1550 IIRC) to 1000-1200 degrees F. My oven cools more rapidly than that, and when I tried to anneal it simply didn't work. Burying the pieces in sand didn't work either.

I did try various normalizing processes (each O1 manufacturer has a slightly different recommendation) but the results were inconsistent--in some instances the pieces became brittle and snapped, and grain growth was visible along the breaks.

There's a stress-relieving technique for O1 some processors advise--heat slowly to 1200 F, then cool in still air. I have tried this, after cold-bending the pieces and before hardening, and it doesn't hurt but I can't tell if it helped.

Here's some links to O1 heat treating. The last one, buffalo precision, has a suggestion for a double temper that they call a "stress relief temper" that really worked for me. After doing the second temper I was able to toss the tools up in the air, and watch them come down on the floor and bounce back up like springs without breaking.

Hudson Tool Steel Corporation

http://www.alro.com/datacatalog/014-toolsteel.pdf

http://www.bucorp.com/files/aisi_o1.pdf

http://buffaloprecision.com/data_sheets/DSO1TSbpp.pdf