PDA

View Full Version : First attempt at heat treat



DropPoint
08-21-2010, 05:38 PM
I have a 3/32 1095 knife I've been working on that I heat treated today and I think I did things right.

I'm using a charcoal grill and a hair dryer as my forge. I put my steel into the coals after I had heated it up a bit with the hair dryer. Then I heated to non-magnetic and put the lid on the grill and let it sit for about two minutes.

I took it out and immediately put it in a canola oil quench and I didn't even get a sizzle let alone any flame. So I put the knife back into the fire and this time kept the hair dryer going on the blade until I had a nice cherry red(?) and non-magnetic once again.

I quenched again in the canola oil and got some flame this time which quickly went out on its own. I left it in the quench for about 1-2 minutes then pulled it out and put it in my little oven at 450 degrees for an hour and half.

Sound good? It's cooling now so I'll inspect for cracks later tonight. I had a very slight warp when I took it out of the oven which I've bent out (I think)

I hope I did this right. Put a lot of effort into my first knife from scratch. :)

silver_pilate
08-21-2010, 06:53 PM
It's hard to say if you nailed it or not. When I was using canola, I never really had any flare-ups. It sure smells nice though :D. Anyhow, you may be in the ball park. It's just impossible to know with what you did. A couple of common problems that you have to watch out for when you're not sure of your temperature are not heating enough to get to critical and overheating and blowing up the grain size. It takes some testing and careful observation of steel color in consistent low lighting to heat treat something like 1095 consistently without knowing the temp. The canola quench will likely be fast enough for the thin cross section of a knife, you just have to make sure you had it at critical temperature.

Something else I'd recommend for next time is to let the blade cool all the way to room temperature before tempering. Also make sure you heat up the oil a little bit to decrease the viscosity so it is able to cool faster. 125-130F would be good.

--Nathan

DropPoint
08-21-2010, 08:27 PM
Thanks for the tips silver. I guess I won't really know until I'm finished cleaning up the blade and test it. I've cleaned it up a bit and no cracks. So that's good.

BossDog
08-21-2010, 09:38 PM
Nathan seems like he gave you a really good answer. Let's hope it turns out for you...

Jerry Bond
08-21-2010, 09:55 PM
Nathan, it seems to me like your getting to be more and more like Ed---Always giving the right answers. I know that I will ALWAYS listen to either of ya'll.
Jerry

silver_pilate
08-21-2010, 10:13 PM
Thanks, Jerry. But I'll be the first to tell you that there are a ton of guys on here that know way more than I do. I just try not to answer unless I've got a pretty solid handle on the answer. It's thanks to guys like Ed and Kevin and Tracy (and many others) that I know anything at all, and I just try to pass that along.

--Nathan

DropPoint
08-21-2010, 10:59 PM
Nathan - very helpful indeed
I really like this forum because everyone has been so helpful. I feel like I should give back more than I have some times but don't know what.

So in the interim I'll just post a not so good photo of my knife after the heat-treat and a little bit of cleanup. Thanks again for the help

http://i133.photobucket.com/albums/q66/calistoga54/PatternNo2.jpg

Kevin R. Cashen
08-22-2010, 09:20 AM
1095 is not necessarily the steel I would choose to start out with using the tools you have available, but that being said it is also quite possible to make a very nice knife with it if you develop the skills to compensate for it. What sticks out in my mind is the closing the grill and waiting. While soak times are the ideal, when using a forge or other simple heating method they are not a luxury that we have, we need to get things to temp and quench before something can go wrong. Some say the magnet is "foolproof"; I say only fools would put all of their faith into one test or indicator without a verifying cross reference. Thus the magnet is most powerful as a heat treating tool when used in conjunction with knowledge of the phase changes we are aiming for. Wait for evening and practice this-

Heat just a bar of your chosen steel from one end and test it with the magnet by sliding along the side from your cool end to the hottest extremity. Take time to careful note that color of the steel at different positions. One thing you will notice is that the bar will go from dull red to "cherry red" to bright reddish orange, but then there will be a dark shadowy band that is followed by a bright orange red again. That shadowy area is very, very important to us as heat treaters.

In order to harden our blade we need to put more carbon into solution within the steel than is possible at room temp and then trap it there in the quench. The crystalline makeup of the steel is a different configuration at the elevated temperature which will allow it to hold the extra carbon, but it requires large amounts of energy to reorganize the iron atoms into the new configuration. So what causes that shadow is the internal transformation hogging up heat and light energy. It is in the beginning of this range that the magnet will stop sticking as the electron spin is affected by the on coming changes. For lower carbon steels you may want to wait for the bright glow on the hotter side of the transformation, but for 1095 you want to memorize the look of the spot just above nonmagnetic but before shadow goes really bright again.

The magnet is only fool proof for determining the Currie point of iron, which is around 1414F regardless of the steel type, despite that fact that every alloy will have a different temperature that is best to quench from. However that shadow, called "decalescence" is determined by the chemistry of that particular bar of steel making the necessary transformation. The human eye trained to recognize decalescence can be more accurate than the magnet, but the two together, verifying each other, is a very formidable tool.

Learn that temperature and just try to get the entire blade evenly to it and you should have it to where you want to be for quenching. Leave the spot on accurate extended soak to neurotics like me who freak out over 2% less austenite, and just enjoy a really nice knife that you managed to make with simple tools.

A properly heated blade entirely below the surface should not result in flaming of the quenchant. People who flash or flame their quenchant did something wrong and are endangering themselves, their shop and ruining their quenchant. You should get a short hissing-sizzle quench sound and then gentle cooling to ambient.

DropPoint
08-22-2010, 10:45 AM
Kevin,

Thanks for the reply. I have a short piece of 1095 left over from the knife. I'll try your suggestion and watch closely for what you are talking about. I don't know if my camera's colors would be accurate enough but I'll try getting a good shot of what you describe as well.

RodneyJ
08-22-2010, 08:20 PM
Kevin
you stated that 1095 is not what you would suggest starting with using the tools that he has. I am trying to start using a one brick forge heated with a propane torch. what steel type and quench oil would you suggest for some one just starting out. I am making hunting knives and just looking for something that has better edege holding ability than the factory knives I own. I also am working with D2 and 440C these I will send out for heat treat. but I'm looking for something I can play around with and do some learning

silver_pilate
08-22-2010, 09:58 PM
Rodney, I'm sure Kevin will chime in as well, but I'd recommend 1080 or 1084 for heat treating at home with those tools available. They are as close to being eutectic as any knife steel out there, and as such, the heat treat is much simpler than other steels. For all intents and purposes, you can use a magnet more accurately with this steel than any other as austenizing temperature is just a bit about curie point (non-magnetic). So basically, take the entire blade up to non-magnetic, watching for the decalescense Kevin described earlier. Once your colors are nice and even at non magnetic, you quench in a fast medium. I think you'll find a water quench to be severe for those steels with a higher failure rate if stresses introduced into the steel during forming aren't dealt with. Some people use brine, but for something with a thin cross section like a knife, you can get by with quenching in canola oil (though Parks#50 forumlated oil is my first choice).

Kevin has an excellent run down of heat treating 1084 somewhere on his site.

--nathan

RodneyJ
08-22-2010, 11:04 PM
Nathan
I have seen alot of people recomend the Park # 50 I will have to try and find some. I have tried to heat treat 2 different knives the first was a file knife. that was ok but not great the secound I have not put an edge on yet to test I hope I got it right because I really like this little knife. Can you tell by looking at the blade if you have grain growth. if so what does it look like. I have been doing alot of reading and getting confused.
Thanks
Rodney

silver_pilate
08-23-2010, 07:47 AM
Rodney, the only way you can determine if grain growth is a problem is by performance and destruction testing.

As for performance, you want to put an edge on the knife and test by cutting rope, cardboard, hacking 2x4's, etc. If you're seeing edge chipping during hacking 2x4's or similar, it could be that you have grain growth that is causing your knife to be brittle, or it could be that you didn't temper at high enough heat, or.....etc etc etc. If you see your edge rolling over rather than chipping, it could be that you didn't fully harden the steel or that you tempered at too high of a temperature.

The only way to really know about the grain size is to break the knife and look at the grain structure under a microscope. With the naked eye, you can tell to some extent, especially if there is significant grain growth. When you look at the break, if you see a grainy appearance like compressed sand, you probably got it too hot for too long.

Now, since this is one of your first blades, you may just want to keep it around, carry it, use it, and see how it does. In the future, you can test your heat treat on something that you put less work into (i.e. thinned pieces of your steel that you run through various heat treating protocols using the tools you have and then break or test to destruction).

--nathan

silver_pilate
08-23-2010, 07:50 AM
Oh, and Park's#50 is a great fast oil for steels like 1095, 1084, W2, etc. For medium speed steels like O1 or CruforgeV, something like AAA is a great oil. They can usually be had in 5 gallon buckets if you can find a distributer. They're not cheap, but they last a good while, and you only need a couple of gallons to quench most average size knives.

--nathan

RodneyJ
08-23-2010, 08:23 AM
Nathan
Thanks for the info, I do want to keep this one around. I found an article by Kevin were he recommends 1070,1075,1080,and 1084 as good steel for a beginner to start heat treating I will have to go back and read it several more times as I practice. also I was able to find a local maker that offers heat treating services I am going to check with him and see if he will let me watch the process so I can know for sure what the decalescense looks like.
Rodney

Kevin R. Cashen
08-23-2010, 09:45 AM
Kevin,

Thanks for the reply. I have a short piece of 1095 left over from the knife. I'll try your suggestion and watch closely for what you are talking about. I don't know if my camera's colors would be accurate enough but I'll try getting a good shot of what you describe as well.

Rodney, as Nathan mentioned in his excellent post 1084 is the best steel for most any forger and particularly for beginners. One excellent rule to remember to keep your life easy is - simple steels for simple tools. Two things make steels simple, low alloying and trouble free carbon levels. The more alloying you have that can interact with the carbon the tougher your job gets, and the more carbon you have above .8% the same complications arise. However, when you dip below .8% you get in to a situation of having to fill large amounts of iron with limited carbon.

Alloying that does not interact with carbon is not so much an issue and can be an asset. I add this caveat to acknowledge manganese, which is present at some level in most modern steels but can be a help in getting over the hardening hurdle.

1095 not only has extra carbon that you have to do something with in order to keep it out of mischief in your blade, but it also has much less manganese which makes the job of full hardening a bit trickier. It is for this reason that so many recommend a very fast oil like Parks #50 for 1095. However I would not expend too much energy on obtaining a product that the producer does not want to sell to you, or is expensive enough to sorely challenge cost vs. benefits factor.

1084 has both the manganese level for better hardening as well as carbon content right at the eutectoid sweet spot to make it very trouble free and most efficient in getting full results. 1080 is also a good choice, and either should harden pretty well in Toughquench, McMaster Carr or any number of good oils on the market (most traceable back to Houghton international, a very good quenchant maker).

Kevin R. Cashen
08-23-2010, 10:00 AM
On grain growth- if you have quality old files, score one and break it. Now use the fractured end as your reference and practice nailing the right temp and then break a piece off your practice pieces to compare to the file example. If it is a quality file it will have the fine velvety grain look you want. Actual grains should not be resolvable by the naked eye, if they are they are too big, the accumulation of their microscopic surfaces will give you that velvety look. Do not buy any of the hocus pocus about being able to see grain size on the outside of a prepared blade or getting actual grain size numbers off from a fractured end. Actually attempting to measure grain size to a number designation requires tools most bladesmiths do not have, I know because I have those tools and it still isn't a cake walk. To really measure austenite grains you need to use special water cooled saws to cross section the steel and then mount it for metallographic examination so that you can properly polish it to levels exceeding 50,000 grit before etching in rather hard to get reagents to make the grain boundaries recognizable. Then under 100X magnification you need to apply one of a few formula methods to determine the ASTM grain size based on the number in given area. Believe me it is much easier just to break a file and stay finer than what you see there.:3:

Oh, I also wanted to add that another great exercises is to score or forge notches in your test bar used for seeing decalescence, about every 1" or so. Heat to see where the shadow is by counting in on the notches, but also pay attention to the area beyond decalescence. When still at temp quench in water and then start breaking off 1" sections and examining the grain. You will find it getting finer as you approach the shadow area and then it will become very hard to break without bending. This way you can have a visual reference with direct correlation between temperature and grain size. Another trick is to overheat the steel in the first two inches to produce very large and weak grains in the 1" you break off. Then reheat to a normal heat and quench the same large grained section. The next fracture will reveal a fine grain again, from just one corrective heat. This is important to get smiths over the grain growth hysteria our field unnecessarily suffers from. Once you learn these temps grain size is yours to control at will, and you don't need any magic forging techniques, all you need is a heat source and the knowledge of proper temperature cycles.

RodneyJ
08-23-2010, 12:16 PM
Thanks for the information and tips the reason I ask about being able to see grain growth is that after heat treating some 1095 the other day I noticed small raised spots on the blade that were round or oval in shape and approxamitly 1/16 to1/8 in size. These spots seemed to be pretty evenly distributed through out the blade and took a good bit of sanding to remove them. The only other steel I have tryed to heat treat was a file knife and do not remember seeing these spots on it.
Rodney

DropPoint
08-23-2010, 08:49 PM
A lot of good information here, I appreciate it. I'm really going to have to study this whole process. I just tested my knife with a file and I definitely didn't get it the same hardness throughout. The handle portion is easily scored with a file yet the blade itself is not, which is sort of good I suppose. I need a more uniform heat source...time to build a small gas forge

Doug Lester
08-25-2010, 03:12 PM
I would not expect through hardening with any of the 10XX series of steel as they are shallow hardening. They will only through harden to a thickness equal to twice the depth of hardening for a particular steel in this class. Pearlite will be formed in the sections of the blade thicker than that. One thing that influences depth of hardening is grain size with larger grain promoting greating depth of hardening. So yes, one could get through hardening at all thicknesses of the blade if the grain is large enough. However, large grain is to be avoided because it also promotes brittleness in the steel. On the other hand, over refinement of the grain is to be avoided too because it could make the blade unhardenable or the hardened edge so thin that you will grind it away during the finishing grind or sharpening.

Another thing about the 10XX series of steels is that you only have about 9/10 of a second to get the temperature of it to fall from around 1400 degrees to 1300 degrees. That means that it must be above 1400 degrees when the blade is plunged into the quenchant. That means that you must move the steel from the forge to the quench tank just as fast as you can safely move. Your quench tank should also be close enough to your forge that you can reach it in one step or by turning your body.

Doug Lester