O-1 and 1095 heat treat temp/grain question (newbie)

D

DarrenW

Joined
Dec 8, 2013
Messages
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Hi Gang,

Brand new to this forum and just getting into knife making and trying to do it all with my limited resources and knowledge - great fun! :-)

I have read numerous threads on various sites about heat treating these two steels and how "tricky" they can be to do (properly) but would also like to try (and learn). I have read some of Mr Cashen's comments and many others so I do understand about using the proper equipment to get the best out of a steel, BUT, I would like to maybe play a little with this. What I would like to understand is just how negative an effect to changes in structure are caused by variation in temperature during the heat treat process.

So here's the scenario. Gas forge that can only be controled to a low temp of ~1680F with any consistency; not able to get a carburizing atmosphere but seems to be neutral. Using the above mentioned steels (O-1 and 1095 1/8" stock) and trying to get the best possible result with said limitations here's what I was thinking.

Option 1: Double/Triple quention method. Negatives - possibly too stressful on blade causing warping/cracking. Seems pretty straight forward trying to get more carbon into the edge to harden (terminology?).

Option 2: Setting forge to lowest consistent temp and manually controlling blade temp by heating and pulling blade in and out of forge. Negatives - temp variation causing ????? grain growth? What else? If I can judge temp (by guess and by golly) to around +/-200F or so (or worse based on my very limited skill/knowledge), what will I be doing to the steel? Will the steel have huge grain growth or is a temp swing of that causing something else?

Any thoughts or input would be wonderful if you have a moment or two to spare for stupid questions.

Thanks!
Darren
 
The best answer to your question is to not use either of those steels before getting some experience with simpler steels, such as 1084, and go back and read more in the stickies. 200° + or - is a wide range of variation. You can get very close to the quench temp by bringing the steel to non-magnetic, noting the color, then increasing the heat to one, or two shades of red hotter. However, if you forged the blade, you have steps to in heat cycling before reaching that point. Neither of the two steels you have chosen should be heated over 1475°, except when you are normalizing.
 
Plus, if you are going to be working with the O1 have your tempering oven up to temp when you do your quench. As soon as the blade is quenched and cooled sufficiently get it right into the first tempering cycle. If you wait too long there is a good chance you will hear an unpleasant *ping*.
 
Not true in my experience. Very slim chance of problems. I've never had 01 crack for any reason. You may be thinking 1095, which often can. He should not be working with 01 anyway without a HT oven so it can be soaked. 01 doesn't even harden fully until stabilized at ambient temp.
 
Do you have a muffler in your forge? If not get one, I use a section of 2" square pipe (fits the blades I make usually). This will help you steady out the temps some where the knife is concerned. When I am using my thermocouple I run it thru the back of my forge into the muffle. I combine that with watching the colors of the steel hence why I have adopted the historical tradition of heat treating at night if you wanna call it that. Dark room or night time help judge the color and what not.

1095 is gonna be a tad tricky. I varying success with it in my forge. I do better with 52100/w1 and w2/ and 1075 which I use most often. 1084 would be a good starting point to get some experience judging color and what not. Plus its alot less stressful if all your doing is going a couple shades above non mag and quenching vise trying to hold a temp for 5 or 10 minutes when your first starting out.
 
LRB,

I hope I wasn't offering erroneous information about the O1. I was just passing along the advice I got from my steel supplier and an ABS master smith.
 
Thanks for all the input Gang, much appreciated.
I hear what you are saying with working with a more appropriate steel to start with - actually I am using some 1084 for a new chef knife for myself right now but do have a bunch of 1095 and O-1. I have played with these steels a bit and came away with servicable blades, so I know I can get something to "work" but what I am trying to accomplish (or not) is to make a better blade if I can. There is so much information here and reading the various dialogs many others here have started I am trying to get a handle on what is actaully happening to the steel. I've watched YouTube demos of guys using much less sophisticated heating methods to make what appears to be a very passable blade with little trouble so it is a bit of a case of trying to make the best possible product within the limitations of one's equipment and supplies. It is also, for me, as much a learning experiment as it is a quality (relative) tool. I do mostly grinding to get to blade shape and use the forge as a heat source as I do not have power available to me to setup a proper electric heat treat oven; and truely at this point don't need to at the moment as this is a hobby level endevour and not paying the bills (yet), in the future who knows.
I'll let you know if I end up with something that works.
Darren
 
Why don't you start with a beginers steel as you are a beginer ?? 1084 is one but it really makes a very fine blade. Start with one steel and experiment with that a lot before you try a second one. Above the normal HT temp you will get grain growth. This is more a function of temp than time.Instead of testing blades go to a smaller piece and do tests on toughness [break the blade] and other destructive tests.
 
Thanks again everyone. I think I am going to do as quint suggested and see if I can stabilize and reduce my forge temp to do this properly otherwise will succumb to the greater wisdom and stick with other steels.
To answer my original question, if I get the gist of what everyone is saying, without precise temp control grain growth is too large and will produce a weak/poor blade and essentially a waste of effort.
Darren
 
Not a waste in effort. A learning experience leading to more knowledge and eventually a great blade. Start with simpler steel to HT and gain success then move on to more complicated steel. 1095 is not easy to HT with simple methods. It can be done but is more difficult.
 
Just remember a well heat treated 1084 blade will usually perform better than a steel that doesn't have a proper heat treat. It's fine to experiment, but you will be giving up performance.
 
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Wanted to add since I was thinking about this. So 1095 can be done and can be done well, its just harder to do. I dont want it to sound like you cant HT 1095 in a gas forge with minimal equipment. For instance I have two kitchen knives I made in 1095 about 8months or so ago. One I have been using every night I cook and it has worked great. I took both of these blades and performed a hardness test and got 62hrc on both in various spots. These were tempered at about 410F so everything seems to have worked out well.

Ofcourse there are other attributes then HRC, that is only one scale to measure the performance possibility in a blade.
 
When I first started I was doing 1095 in a forge I had very inconsistent results. Mostly due to overheating. If you insist on using 1095 because you have a bunch of it this is a humbling test. Put your blade in a vice with the tip about a inch through the bottom and see if it is flexible . Do this after you have tempered. A lot of my blades would just snap and reveal a overheated mess of grain so poor it looked like table salt. I wasn't trying to bend them just a little force is all I needed to see.

I now have a oven so I rarely use the forge for heat treating. As noted in above posts save the 1095 for later on and track down some 1084 or some 5160 and you will get a usable blade.
 
The above advice is all good. The reasoning is this:
Your forge is running at around 1680°F ( BTW, how was that determined?). That is the parameter you can't change.
You put a piece of O-1 or 1095 in and want to hold it at 1475°F for ten minutes - How will that happen? - It won't.
You can move the blade in and out ( called "pumping" the blade) to get an even heating from tip to tang, but if the forge is 200° too hot, the blade will quickly become too hot if it stays in there too long. This will cause severe grain growth and other problems with the blade upon quench.
What most people with only a forge do is run it at as low as temperature as it will stay stable, and pump the blade slowly from back to front of the forge, getting an even color on the blade. As it gets to a bright red, pull it out and check with a magnet placed on the side of the forge to see when it gets non-magnetic. For practical terms, call this 1400°F ( it is a few degrees higher than that actually). You want to heat it about two shares of red brighter to around 1475-1500°F. Once it gets there, keeping it in the roughly 1700° chamber will be counterproductive. Pull it out and quench it. The steel would do better with a longer soak ate 1475°F, but since that can't happen in your scenario, you just quit when you have to. The damage by a 10 minute soak at higher temperature will be far more than the slight loss in hardness and toughness by a too short soak time.

Building a blown burner will allow lower hold temps. Building a PID controlled blown burner will allow holding at 1475F nicely.

Caution, staring into a forge to do HT can seriously damage your retinas. You must wear forge glasses. The welders shops usually can get them, and many get them from Auralens.
 
Hi bladsmth,
Thanks for that info, that is kinda what I was wondering - what happens and to what extent it happens when the heat control is out (10%) or so and it is significant. I like what you are saying about taking the steel to the correct temp and then quenching rather than over heating the steel; better to get something usable, though not perfect, than to finish with junk. I read an article by Newt Livesay commenting on something Bob Dozier said about knives and it struck a cord with me and now understand a little better the others here who told me to not use 1095 etc. Bob said, “They have never really owned a good knife,” and although I am trying to make a good knife I have no real reference point to compare to as many of you doing proper heat treat and getting spectacular results (compared to the average junk sold in stores) and when I read somewhere else about someone using 1095 and HT in there forge and selling their wares I wonder who is correct. It's all relative to the expertise and knowledge of the maker. One man's treasure is anothers junk(?).

Anyway, I had some time yesteday to play in the shop and here is what has transpired since last week. I took quint's advice and made a little muffle (if I am using that term correctly) out of a scrap piece of angle iron and rested it on top of some smaller pieces of firebrick. This in effect made a chamber outside of the direct flame front and it looks like I am now able to get this area into the 1480-1520F range consistently - I am using a thermocouple probe to measure the temp in there, and supposedly it should be accurate to +/- 1F. I am still trying to figure out a choke for the forge (it a Majestic 2 burner deluxe knifemaker model) but I may have to come up with my own burner to get more control. I would really like to control the mixture to richen it up and allow me to have a carburizing atmosphere (correct terminology?) if I can. No matter, if this works I am happy and more temp is no problem which means I should be able to HT some of the air hardening stainless steels (looking for some quenching plates now).

So what I am planning is to do a HT test run on some 1095 (to see for myself and try to understand it better). I am going to heat treat some scrap pieces of 1095 one inside the muffle and one outside with temps measured in both areas, quench and then break them in two to see if I can see the difference in the grain. If all goes as planned I will take some pics of the steel after HT as well as my setup and post them.

I just want to say that this forum has been so helpful and I very much appreciate everyones input as this is not something seemingly many people understand and there are few bladesmiths where I live that I can talk to, so again this is great help and if this learning experience on my part becomes useful for someone else all the better.

Take care
Darren
 
Stacy,

What is your opinion on whether or not O1 should be tempered soon after quenching?
 
All steels should be tempered immediately after quench. The hyper-eutectoid carbon steels can crack if left too long, and the higher alloy steels can stabilize the retained austenite if left too long. O-1 falls into the carbon steel group, and is one that should get tempered with little delay.

Now, when we say immediately, some people translate that into, "Run from the forge to the kitchen with the still smoking blade and stick it into a pre-heated 400°F oven." It isn't that imperative, but it should be done within the hour. The best scenario is to do the HT on as many blades as you have in the batch, let the blades cool undisturbed to room temp, check the edge with a file to make sure they hardened, wipe/wash off the blades gently, and put them in the pre-heated kitchen oven. All this can easily be done in less than 30 minutes.

Bending, grinding, dropping on the floor, and anything that will shock or stress the blade should be avoided until after the first temper. ( You can straighten the blade while still hot right out of the quench oil, but after the blade cools to 400°F, don't try any more straightening until the first temper is done. Straighten any further bends and warps at 400° while still hot at the end of the first temper, and repeat as many times as needed. Just keep the blade between 300° and 400°F while straightening and you should have no problems.)
 
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