How the hell do you heat treat 1095?!

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Now as for the lack of normalizing, I honestly don't know where knifemakers got the concept of normalizing right before the quench (perhaps from the abundance of lamellar annealing which could result in larger grain). The purpose of normalizing is to equalize and fix internal structures after very radical procedures like forging and other heavy deformation and temperatures. Industry often only does one at 1600F; this would be very unwise right before quenching. The proper thing to do for steel that has been heavily machined before hardening would be a good old stress relieve, not an all out normalization.

Bladesmiths are fascinated with normalizing because some folks have advanced the idea that there is some fantastic magic in ridiculously small grain size that will turn steel into unobtanium. There is a point of diminishing returns for everything and grains size can become too small to be useful for our purposes, don't get me wrong here I am not endorsing large grain which is universally bad for strength, I am just saying that there is a point where chasing that immeasurably small grain size is counterproductive.

I normalize after forging to fix all the problems that forging can inflict upon a bar of steel. Hand hammers simply cannot deform equally and evenly throughout, while forges and anvils are not the best for perfectly even heating and cooling. I normalize to equalize grain size, evenly distribute carbides and prepare the blade for the subsequent treatments. You can shrink the grain by doing a series of normalizing at the same temp but as the grain size decreases so will the coarsening temperature of those grains (isn’t interesting how nature builds these regulators into things, there is always give and take- e.g. the closer you get to the speed of light the more energy it takes to do so, until it becomes impossible to equal or exceed it) . Eventually you will get the grains fine enough that the coarsening temp will equal the normalizing temp, so you will need to keep ahead of it by lowering your heat.

If one is going to go lamellar in the wood ash, then really fine grain may be pointless since to make course pearlite you will have to go to a great enough temp to get total solution, which will reset the grain size according to that temp. This is not a concern for me since I do spheroidal anneals, the spheroidal anneal is subcritical and leaves the grain size alone while balling up the carbides within. This type of anneal can be greatly accelerated by being performed on martensite. My O1/L6 mixture will harden from normalizing heats so I am set, but one working with a forge and 1095 may want to heat the steel to critical and then quench before heating repeatedly to dull read to ball up the carbides.

After my anneal I have the grain size exactly where I want it, I have the carbides where they need to be and the steel is as stress/strain free as I would like for subsequent operations, so there is no need for a treatment before the quench, unless I get really stupid in the grinding (at least one good reason not to turn the steel blue while grinding, and to grind evenly).
 
billf said:
Kevin,

I have a couple questions:

1) after normalizing, can you spheroidize 1095 (or O1) by holding at 1200 for 2 hrs or so, or is that just a stress relief?

2) Any benefit for 1095 (or O1) to "snap temper" at , say, 300-325 after the quench, then soak in Liquid N2, then temper as usual? I would guess there is not too much retained austenite in 1095, but if there were it might help. O1 probably has a higher chance of retained austenite - again, is the "cryo" at all worth it or just excess?

Bill

Bill

1) Depends on the microstructure before the operation. If the steel was heated to dissolve all the available carbon and evenly distribute it and then treated to keep it there- as in martensite, then a soak at 1200F will spheroidize. But pearlite takes exponentially longer times to spheroidize so you would probably dull some drill bits on air cooled 1095 that has been soaked at 1200F-- believe me I know:( . I have even broke some threading dies on O1/L6 tangs that were done this way. But any steel that I have soaked at 1375F and then very slowly cooled has always been dead soft and well behaved.

2) If there is any chance at all that there is retained austenite then there will be a benefit from cryo. Cryo zaps reatained austenite there can be no argument there, and if you find a jump in HRC after cryo, it did its job.

To all of the long winded answers I have provided I need to add this qualifier- this is what works for me, in my shop, with my materials and my equipment. I stongly encourage folks to experiment and work up a system that meets your conditions and needs. The closer you get to the equipment that industry has, the closer you can adhere to their methods, if you have more "improvised" tools for the job you will need to be more creative in you methods.
 
Kevin

Thanks! I think I'll try a little experiment with the 1095 - 1 with 1200 degree stress relief, 1 with the "Cashen anneal", see if I can tell the difference.

Don't own a hardness tester, so I can't be real sure, but I did try the liquid N2 deal with O1 and it seems to be a little more wear resistant - could be the placebo effect, though!

I do use an interrupted quench for the O1 (Park AAA) and for the 1095 (Park 50) , so I'm trying to help optimize microstructure as best I can without salts.

Bill
 
Seeing how the question of heat treating 1095 was just being discussed, I'd thought I'd bring back this thread from some time ago.

Brian
 
For Son of Bluegrass: Do you use dry ice in the freezer?

My understanding is dry ice in alcohol will take a blade to -100F and that will take care of any retained austenite. I've got two ways of doing it.

1) A big plastic dubba with good sealing lid that I put the blade, dry ice and low-water-content alcohol in, then put dubba into the freezer for a while.

2) A smallish cooler that fits inside a box made of board insulation with blade, alcohol, dry ice in the cooler then in the insulation box for a while.

If I do understand correctly, the blade only needs to get down into the -100F range. It doesn't need to stay at that temperature for any extended time.

Mike
 
I love this thread... and the title.

I've compiled a bunch of relevant tips, tricks and tweaks gleaned from Kevin and mete regarding HT of 1095 and feel I've successfully come up with a clean and simple recipe for hardening this steel.

Here's what I did.

At the end of forging, use a couple of heats in the low end of the forging temps; 1600° - 1700°, use these heats to do final straightening and what-not. Take time, allow to cool in between so the blade can be closely examined for straightness etc.

Normalize, 3 cycles cool to room temp in between each cycle

First cycle: 1600°
Second cycle: 1550°
Third cycle:1500°

Austenitize: 1465° Bring to temp and equalize, THEN soak for 8 - 10 minutes

Quench in 130° Canola/Rapeseed oil. Use Parks #50 if you can get it.

I used my oven muffle to temper
at a true 400° for 2.5 hours and got chipping so I did another 2.5 hour temper at 425° tonight and will see how that does.

The 425° temper produces such a pretty blue oxide color, I wish I could finish my blades in that color.
 
I compiled the text into an Acrobat pdf file. If anyone is interested, I will send it by email to them.
 
I did the same testing that produced the chipping and now there is no discernable evidence that the blade was touched by anything, no rolling, no chipping; still performs exactly as before.

BTW, the test was stabbing it through the top of pop cans and cutting through the pull tab.
 
OK, disregard anything I said in teh previous two posts...:foot:

I finally got to really close inspection of those blades I quenched and while I did do a file test on the edge and spine (edge quenched) I got the expected results with the file test. I started noticing that I couldn't see any quench line so I looked a bit closer, using a file tip to scratch various areas of the blades. What I found was that only a minute portion of the edge was hardened :mad:

Back to the drawing board.

I managed to get a quote from heatbath for some Parks #50 through the company I work for but I would have to buy 55 gallons. Not really very cost effective unless I can sell at least 40 gallons of it.
 
I managed to get a quote from heatbath for some Parks #50 through the company I work for but I would have to buy 55 gallons. Not really very cost effective unless I can sell at least 40 gallons of it.

If the Park's doesn't work out, Houghton International will sell you 5gal of Houghto-quench "K" on a phone call (as fast or faster than Park 50). Also, I found out this weekend that John Perry has a 55 gallon drum of Chevron 70 (Chevron's fastest oil) and he would like to have less of it. He said he was surprized at how fast it is.

Mike
 
If the Park's doesn't work out, Houghton International will sell you 5gal of Houghto-quench "K" on a phone call (as fast or faster than Park 50). Also, I found out this weekend that John Perry has a 55 gallon drum of Chevron 70 (Chevron's fastest oil) and he would like to have less of it. He said he was surprized at how fast it is.

Mike

Thanks for that! Looks like there may be a Houghton distributor about 25 miles from my house.
 
Just for reference...

Along with Houghto-quench "K", there is Houghto-quench "G" (what Brownell's rebrands as "Tough Quench"). I talked with Don Fogg this past weekend and asked him what quench oil he used (when he isn't using water). Don has used Tough Quench/H-Q "G" for a long time. I asked him if his experience was that TQ/"G" would through harden 1/4" fast steels. He said it would. Scott McKenzie (Houghton's metallurgist who posts on BS and SFI) indicated H-Q "G" would through quench 1/4" fast steel, and with less distortion than "K". H-Q "G" is very slightly slower than Park AAA when new but "AAA" changes with time and then "G" is very slightly faster than "AAA".

Scott McKenzie has offered to yap with knife folks and help them find nearest distributors if they contact him through either BS or SFI. Scott is easier to find in an advanced search on SFI where he posts under his name (I never remember his BS post name).

For those interested, here's a link to a big quenchant thread on SFI and Scott McKenzie posted in this thread. http://forums.swordforum.com/showthread.php?t=53085

Mike
 
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