Any advice on backyard heat treating 5160?

V

Vaunripped

Joined
Nov 20, 2010
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I know that 5160 is not the best choice for backyard heat treating, but when the price tag is free you cant argue to much.

I'm going to be using a brake drum forge, canola oil, and a magnet on a stick for the hardening. Not being able to keep the perfect temp for the prescribed 10 min, I don't think I'll get everything out of the steel that It has to offer, and that's ok. Its 1/4" thick spring steel... if I manage to break it I will prolly try and keep it to myself because imo I was doing something WAY wrong.

I have been searching for a few days now and have found little more that "heat it till its none magnetic and quench" or all the temps and soak times to the degree and second that is needed.

Any tips or tricks on getting as much out of the 5160 as I can with the tools I have?

Thanks for any advice.

Dusty
 
Tim Lively has a great video (Knifemaking Unplugged) that includes very low tech heat treating for 5160. I have also done some simple HT with 5160 and had pretty good results without any soaking and quenching in automatic transmission fluid (I think canola is too quick for 5160). As with most simple steels, you can get by with heating a little past non-magnetic and quenching in warm oil. You probably won't be getting the most out of the steel, but you'll still make some great knives.

- Chris
 
I don't know that I agree about it not being good for backyard heat treating. It's the steel I use all the time, heat treating with a propane forge and quenching in canola oil, and it does quite well. Just had a blade I posted in the Custom and Handmade subforum go through a month of SERE training with an airman that cut down a bunch of branches, batonned firewood, etc. for most of a month and the airman said it was still as sharp as it was when he got it. That's the hardest use one of my small (7") blades has seen and it stood up just fine.

See it here: http://www.bladeforums.com/forums/showthread.php/913040-Primal-Tactical-SERE-knife

As for the heat treatment, finish up your forging and then triple normalize. In other words, heat above nonmagnetic and let it air cool until no more heat color shows up in a low light environment. Each time you do that it shrinks the grain size and makes the steel tougher. I was thoroughly convinced when I saw this: http://paleoplanet69529.yuku.com/to...n-Grain-Size-Control-Experiment-----normalize

After that do all of your stock removal and get ready to heat treat. If you are using a solid fuel forge, it's a good idea to use a muffle furnace. This is an idea I learned from Tai Goo, though my dad said he saw blacksmiths using it when he was a kid. You take a piece of UNGALVANIZED pipe large enough to fit the blade inside with a bit more room and heat it up in the forge. Once it's good and hot on all sides (you may need to rotate it to get it to heat all over), stick the blade in and heat in there. The pipe evens out the heat along the length of the blade and keeps from getting too hot. You can also cap one end and put wood shavings or other organic material inside the pipe as you heat the blade. As it burns, it consumes the oxygen inside and you can get very little scale.

Bring the blade above non-magnetic and quench in canola oil. Check for warps, then heat and quench again. Do it a third time, then wipe off the excessive oil and draw temper at 400 degrees for an hour. Let it air cool, then do it again and then a third time.

Doing the triple quench helps approximate the effects of soaking the blade at temperature, as I understand it.

So, triple normalize, triple harden, triple temper. Then see if you're unhappy with the results or not. One of the appealling aspects of 5160 is that it gives great performance with a simple heat treatment.
 
Oh, just saw Hesparus's comment about canola oil. Every blade I make is quenched in it, with no problems whatsoever from the quench. Plus it's non-toxic, which is a big plus!

And I second the motion to get Tim's video, and follow it up with the suggestion of buying anything that has Tim and/or Tai in it. My number one recommended resource for my students in my simple knifemaking class is Woodsmaster Volume 9 from Hood's Woods because it has both of them in it, closely followed by their individual videos. High-quality blades with very minimal equipment is pretty inspirational!
 
Also keep in mind if you tripple quench the blade, it will warp towards the edge a bit, so start out with slightly more belly in the blade than you hope to have in the finished blade. You can make a trailing point into a drop point just by multiple quenching.
I use canola for 5160 as well.......works great, heated to about 125*F
Darcy:)
 
Thanks a ton, this is just what I was looking for, so far I'm only doing stock removal. The forge just recently got built for hardening, but if that's all it takes to make a better knife I suppose that's what I'll do.

I didn't mean to say that 5160 isn't a good steel, I don't have enough experience under my belt to say any steel is better than another. It was more a statement taking into consideration my lack of experience, were from everything I have read 1084 would be better for my skill level.

Now that I have more information to work off, or at least differently phrased, I'm confident that my work will improve.

Thanks again for the advice.
 
Nah, didn't take it to mean that you thought it wasn't a good steel. I was just a bit perplexed by thinking it wasn't something that could do well with a "backyard heat treatment" as it does well with such if you do it right. It's actually a fairly easy steel to heat treat, and the resulting performance is quite good.

Darcy - True that, though I don't see it in most of my blades. It seems like mostly thin, narrow cross sections tend to curve downwards in the oil quench. A thicker spine and/or a broader blade doesn't seem to be much affected.

My quasi-Japanese-style blades seem most prone to this. :) I heat treated one last week at the same time I did another blade that, while not significantly thicker, was wider. I curved the Japanese-style more than I wanted it to be prior to the quench, while the other blade I quenched in the final shape I wanted. The Japanese-style curved toward the edge and ended up with dead-on the amount of curve I wanted. The other stayed right like it was. Both blades were 5160, both were about the same length, both got the same heat treatment at the same time. Weird, huh?
 
Good stuff Stormy... though, I question the effectiveness of the triple quench. You can either thermal cycle after forging with normalizing or before the final HT with multiple quenches.... the steel doesn't really care. It is the cycling that is important and you don't gain much past 3 cycles.

Nice to see you more active here! See you at Blade?

Rick
 
Yep, don't have a table number yet. Luke says you're buying me a chocolate milk. :) I'll take you up on that.
 
From the sounds of it I shouldn't need to worry about the warp as much with the thickness of the steel I'm using, .204 and full 1/4" all 1"+ from edge to spine.

Dose normalizing it for the smaller grain affect how it files? As in dose it make it harder to work by hand compared none normalized 5160? I'm only concerned because my access to power tools is rather limited so I do a lot of the work with files.

So I only need to do either the triple normalizing or the triple quench not necessarily both?

Would a gas forge make this any easier? After seeing the two brick forge WIP thread I have been toying with the idea of making one.

Thanks again for all the help.
 
A gas or coal forge would make a huge difference.

I am asserting(based on what I've learned up to this point) that generally, grain refinement plateaus after 3-4 decent thermal cycles. Whether you do it after forging(normalizing) or during the multiple quench makes little difference. I will add that more can go wrong with multiple quenching because it places more stress on the steel and there are more variables at play.... so normalizing cycles would be more forgiving. My personal recommendation is to normalize 3 or four times after forging, with a quench thrown inbetween one of the cycles.

Fine grain is good all around... for machining, filing, sanding, drilling.
 
Also a good idea to make your last normalizing heat a bit lower temp...... just below non magnetic as 5160 will air harden a bit and it'll be easier to file if you keep it softer.
Storm Crow, I have had pretty wide thick bowies that warped downwards on me a fair bit........only was a problem with multiple quenches though. For the record I no longer do that with 5160.....I do a single quench after an 8 min soak. I played around with an interupted water quench years ago just for fun and it warps the other direction in water.
The only other tip I can think of is to do your heat cycling in a low light environment.....if you are outside just wait until dark as you can see the color in the blade better. That's why blacksmiths shops were usually kinda dark. I screwed up a sword one time by overheating it in a charcoal fire outside in the winter during daylight hours...........too bright to see the color well and overheated the blade. Result was huge grain that I discovered while trying to straighten the blade and it snapped. Live and learn:rolleyes:
Darcy:)
 
Have you tried quenching spine down to control "tip-dip". The fraction of a fraction of a second that the spine hardens before the edge really helps stabilize the process.
 
Rick Marchand said:
Have you tried quenching spine down to control "tip-dip". The fraction of a fraction of a second that the spine hardens before the edge really helps stabilize the process.
Click to expand...
Never tried that........I always wanted to get the edge in there first just to give it the best chance of fully hardening.....probably not required.......I`ll give it a try. Thanks,
Darcy:)
 
DEllis said:
I do a single quench after an 8 min soak.
Click to expand...

Ah, see here is the part I'm looking to get around, I'm real sure I cant hold that temp for that long with out over heating just going "by eye", I just don't have the tools yet.
 
Rick - As I understand it (and I claim expertise in no area), the triple quench allows the carbon to get into solution better, approximating the effect of a soak time in a controlled furnace for those of us who harden using a forge and "backyard" methods. So, in my mind at least, the triple normalizing is to refine the grain and relieve stress, while the triple quench helps the crystal changes be more complete. Am I off on that? Luke did some testing with O1 and it seemed to play out, from which I theorize that the chromium in the mix is at least part of the reason why it's effective if it is.

Darcy - Hmm, that is odd. Never been a problem with me unless it was a thin, narrow blade. I can anticipate when a blade shape is likely to do that (usually the quasi-Japanese, though I haven't done too many of those) and compensate with extra curve to let it straighten up where I want it to be. It straightens most dramatically the first quench, then a bit more on the other two.

Vaunripped - I haven't noticed a difference in how the steel files (and I tend to file my bevels and leave the file marks as I like the looks of them in conjunction with the forge finish), but Darcy is right about 5160 having a tendency to air quench itself in thin sections. You may be filing just fine at the base of the blade and find that the last inch or two up at the tip will barely cut. Heat it enough to watch the temepr colors run if that happens, and let it cycle all the way through to gray and you'll have it soft again. Don't let the steel get red or it'll air quench itself again.

Rick - Just re-read your spine-down quench comment. The blades that do curve edgeward in the quench have been all quenched point-down in a vertical quench tank.
 
What was Luke's testing, Stormy?

From another thread, here is a response by Kevin Cashen about the differences...

Triple normalizing- this can have an effect on the steel in a couple of different ways the two most prominent would be grain size and carbide condition. If you have heavy banding or other segregation in a high carbon steel, heating it above Accm (the upper critical temp for a steel, which is much hotter than hardening temperatures) will dissolve the current carbides and put everything into solution. Quickly cooling it in air from this condition will keep it all evenly distributed and fine, but it will not help with grain size, in fact it will increase the grain size a bit, if this treatment is then followed by a couple of cooler heats the grains can then be recrystalized into a finer condition. This is the big selling point of the triple quenching crowd, but normalizing will do it with much less stress on the steel and without buggering up your finished blade in the final sequence. Also bear in mind that there is a reasonable size for grains in most steel applications and taking it farther just to boast about the finest grain around is merely overkill and can even have some negative side effects. So refine the grain to a good working size and move on. The real challenge in proper normalizing is in the carbides, grain refinement is rather elementary since it happens every time you heat and cool the steel at a reasonable temperature.

Triple quenching- more of a marketing buzzword than anything else, in my humble opinion. It is basically doing much of what should have been done with good normalizing, but can push grain size down much faster due to increased stress on, and strain within, the steel but all of us know what this also leads to when it gets out of hand. Many of the wild claims attached to it that are not error in testing can easily be attributed to the elimination of other problems that were not taken care of in earlier heating operations. Guys who are working with carbon rich steels that require accurate and extended soaks may find that repeating the austenitizing and quenching procedure will allow them to put much more carbon into play without a proper soak than if they only did it once. It is in this part that the sayings about “doing it right the first time” apply the most.
Click to expand...
 
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It's been a while since Luke told me about it, but he took two pieces of O1 (I don't recall if he had made them into blades or not) and did one with his normal soak time and quench with his HT oven, then did the other one with a triple quench. Said that when he checked them they were pretty much the same. I don't have any more details in memory than that, though I could ask him if anyone's curious.

Re-reading our PM discussion, I have to ask, so what you're saying is that if it's a hypereutectoid steel (carbon above what? .90% approximately?) that's being heat treated in the forge, a multi-quench helps to get the alloying elements and carbon into solution, but that with eutectoid steels, you can quench around 1500 degrees Fahrenheit and get the carbon into solution before the grain has time to grow, meaning you only need a single quench. Am I following you?
 
I guess what I'm trying to say (poorly, it appears:o) is multiple quenching would probably help if someone can't (or doesn't want to) achieve a consistant controlled soak.

If you HT using a torch, it may be something to look at.

I don't want to start into a bunch of different steel types. From my own experience, what I understand about 5160 is that soaking is the best option but if you can't, using a higher austenizing temperature like 1525F-1550F with an immediate quench would ensure full solution. 5160 is hypoeutectoid so you won't get any excess carbon like you would with 1095 or any of the hypereutectiod steels. Check out a steel carbon equilibrium diagram to see the relationship between heat, carbon content and where the Acm line corresponds. It gives a great visual to explain why 1084 is the simple HT'er's friend and why anything above or below eutectoid would benefit from a soak.

That's all I care to get into... HT is one of those touchy subjects, unfortunately. Folks tend to feel they are under attack if someone doesn't agree with their process. I don't want to be misconstrued anymore than I already am.;)

Ricky out.:p
 
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Ok, so lets see if I have this at least mostly correct.

Try triple quenching and normalizing together and separate, either one is better than just hardening once with out a soak. Use a muffle furnace, it will help with scale and evening out the heat. A propane forge will make start up time a lot shorter and will lessen the odds of over heating.

I only have to ask about differential hardening, and I think it goes with the original heat treat question. I understand the basics of what needs to happen, the question is for edge quenching. When edge quenching do I only quench the edge and let the spine air cool or do I edge quench and then quench the rest of the blade? and How much of the blade width is quenched when edge quenching, 1/4, 1/2, 3/4? Is tempering done the same when edge quenching as when full hardening, as in 350-450 (the range I have seen quoted for tempering heat) for an hour or two for two or three cycles?

Thanks again for all the great advice, I'm sorry for getting into such a touchy subject. I do understand that it will take testing to find "what works for me", but the road there will be a lot shorter now.

Dusty
 
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