Heat treating a large 5160 bowie questions

flatgrinder

flatgrinder

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Dec 20, 2005
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I'm about to heat treat a large bowie, ground from 5/16" stock. It has a 10" blade and is about 2" wide. edge thickness is approx. the thickness of a nickel.

I plan on using my forge. It's an old propane NC venturi burner forge. Should I keep the blade facing down while it heats up and when it turns cherry red, test it with a magnet and flip it so it's edge up and put it back in the forge for a couple more seconds?

Is 5160 deep hardening? Should I soak the blade like O1? How long should I soak the blade for? 10 minutes? Or should I just dunk it when it's non-magnetic? Also, would transmission fluid be a suitable quenchant?

Is edge quenching worth it? Or should I just fully harden the whole thing?

Sorry for all the questions, I haven't made a bowie before and I don't want to screw it up.

Any tips or recommendations would be really appreciated! :thumbup:
 
Is this one for your own use and just for fun? Or will you be selling it and then making others for sale? I ask because I have two sets of advice I can give depending on the answer.
 
This one is for my own use. I plan on making more for sale later on. Does the answer depend on whether or not I have an Evenheat kiln? ie. Use the forge for my own, and an Evenheat for the ones I sell? :confused:

(I hope it doesn't as I can't afford an Evenheat at this time).
 
The answer depends upon whether the exact temps and other numbers would matter if it is just by eyeball anyhow:) . Also we seem to have two camps visiting the forums these days, one that insists on total control with equipment that will maintain tight tolerances and steel with a known chemistry, the other enjoying traditional methods that rely upon intuition and getting things just in the ballpark and the satisfaction that comes with doing by eye alone. One side embraces equipment and materials that accommodate the professional offering a product to the public at top dollar. The other tends to resent this position as forcing expenses on them they the don’t need in their approach, and I must admit I can see how gadgets with digital controllers can take away from the old world crafty atmosphere that one associates with smithing.

But I am growing tired of giving the wrong advice to the wrong group and sparking a tinkling contest so I think it is just easier to ask whether they are doing it for fun or are aiming for a professional type of operation before I recommend exact temperatures, extended soak times, quench oils designed for the task etc… Besides it could also save a lot of typing;).

Your idea of heating the edge last is a good one; also keep the tip cooler until the very end. 5160 is not really deep hardening but it is an oil hardening steel. It may need a good soak for the opposite reason that O1 would, O1 is a hypereutectoid with lots of carbide formers so you need extra time to get the carbon into solution. 5160 is a hypoeutectoid with extra ferrite (iron) and some mild carbide forming, but you will need extra time to get that ferrite in the mix. A soak sufficient enough to do it entirely will be quite a task in a forge, so if you can do some pre-heat treatments it may work better. If you have annealed the steel do one or two normalizing heats right before heating to quench in order to mix up the stuff separated in the anneal and it will help with not being able to soak things. If it is any help quenching temperature should be around 100F higher than when the magnet stops sticking.

Even the “just for fun” guys would have more fun with a good quench oil, but I will just let it rest and say that your transmission fluid should work if it is clean and you move the blade to keep things in motion.

Edge quenching is worth it if you plan on intentionally bending the blade, if you want it to resist unintentional bending then a full quench would be the strongest while just tempering the spine back later would give a tougher blade that will also resist bending. In other words, if you ask me, the best route to go with at the time of quench is to put the whole thing under the oil.
 
I am new to the forum but not to knife making. Been making knives for about 9 years.
Kevin - I hope you see this and can continue. I had exactly the same question and found this post with a search. However, I'd like the end of the story. After the blade has been hardened and is touchable ( about 150 degrees ) it, I would think, need to be put into the tempering oven. What temperatures and tempering timeframes will provide what different rockwall hardnesses?? I would think that for a knife like a skinner or a hunter, one would want an RC of around 60-62 for edge holding. But, for a bowie, I would think one would want something softer and more flexable, maybe an RC between 53 to 57. Like the thread originator, I, too, am making my first bowie for my own use.
If Kevin doesn't see this, I would welcome the continuation from anyone.
Thanks,
Jacque
 
Look for some steel maker's instructions for 5160. I know they've been posted here from
time to time and Google is your friend. The relationship between tempering temperature,
hardness and toughness is not simple and linear. It varies with steel type. With the A2
I'm currently using they both seem to peak at 500 degrees. This is almost certainly not
right for 5160.
 
Edge holding ability is not from hardness alone. Much depends on the carbon content and the alloys it may be mixed in, and the heat treat itself. I don't believe you will get 5160 as hard as you mentioned, especially after temper. Study up on the different steels available, and their properties. Some steels are better for impact resistance, 5160, and others are better for holding an edge in use, 01, W2, 52100, and others. Some steels may be at their best at 62 RC, while others may be too brittle at that hardness. If you are HTing in your forge, you may want to look into 1084, or W2. While 5160 can be HTed in a forge, it is at it's best when soaked in a temp controlled appliance, before quench.
 
jacqueeagonsr said:
.................... After the blade has been hardened and is touchable ( about 150 degrees ) it, I would think, need to be put into the tempering oven. What temperatures and tempering timeframes will provide what different rockwall hardnesses??
Thanks,
Jacque
Click to expand...

What condition that steel will be in after "hardening", while using a gas forge for heat, and non-standard medium for quenching is anybody's guess!
Predictable hardnesses can only be predetermined by using known forging, post-forging, controlled hardening and controlled tempering processes.

With the methods "flatgrinder" is using, a LOT of testing will be needed when all is said and done, to determine how successful the day's efforts really were!
 
dlpierson said:
Look for some steel maker's instructions for 5160. I know they've been posted here from
time to time and Google is your friend.
Click to expand...

I appreciate that response. I have already searched the internet with google and have found instructions for tempering 5160 to RC of 48 for springs. Not hard enough for a knife. I appreciate and totally agree with the theory presented in the other responses. I was hoping someone could step up to the plate and give a real specific answer. Something like "I temper my 5160 at 300 degrees for two hours and get an RC around 57 most of the time. Try that for a starting point.". I have the Heat Treatment --- of TOOL STEELS book by Bill Bryson, which has great recipies for a lot of tool steels. I will be glad to share his recipies with anyone (A2, A6, S7, D2, O1, W1, etc). He just doesn't cover 5160. Please keep the responses coming - all are appreciated.
J.
 
jacqueeagonsr said:
I appreciate that response. I have already searched the internet with google and have found instructions for tempering 5160 to RC of 48 for springs. Not hard enough for a knife. I appreciate and totally agree with the theory presented in the other responses. I was hoping someone could step up to the plate and give a real specific answer. Something like "I temper my 5160 at 300 degrees for two hours and get an RC around 57 most of the time. Try that for a starting point.". I have the Heat Treatment --- of TOOL STEELS book by Bill Bryson, which has great recipies for a lot of tool steels. I will be glad to share his recipies with anyone (A2, A6, S7, D2, O1, W1, etc). He just doesn't cover 5160. Please keep the responses coming - all are appreciated.
J.
Click to expand...

I think most people temper at 350, but I've heard of some going over 400. Myself, I don't use 5160 for knives I'll sell, so I don't have a lot of experience with it, but I'm using it for my JS test blade, and I tempered at 350, and it's working fine.

BTW, welcome to Bladeforums!
 
jacqueeagonsr said:
I appreciate that response. I have already searched the internet with google and have found instructions for tempering 5160 to RC of 48 for springs. Not hard enough for a knife. I appreciate and totally agree with the theory presented in the other responses. I was hoping someone could step up to the plate and give a real specific answer. Something like "I temper my 5160 at 300 degrees for two hours and get an RC around 57 most of the time. Try that for a starting point.". I have the Heat Treatment --- of TOOL STEELS book by Bill Bryson, which has great recipies for a lot of tool steels. I will be glad to share his recipies with anyone (A2, A6, S7, D2, O1, W1, etc). He just doesn't cover 5160. Please keep the responses coming - all are appreciated.
J.
Click to expand...
J., not to sound redundant here, but tempering at "X" degrees to get "X" RC is TOTALLY dependant upon the degree and uniformity of hardness you achieve in the FIRST place. And, that degree and uniformity of hardness depends upon the forging, post-forging and hardening processes and control thereof.
First, let's get that little puppy hard, and then we'll deal with tempering and testing.
 
The fact is, you're not going to get 100% performance out of any steel you heat treat in a forge, unless you can hold a very precise and constant temperature for 10 to 15 minutes. Probably 1084 would be the best, since it doesn't have any alloying elements that would require a longer soak time.
 
Thats because the speed at which 5160 needs to quench is rather slow when compared to stuff like 1095 and W2.

anyway

5160

Anneal at 1525°F then cool rapidly to 1300°F and cool to 1200°F at no more than 20°F/h for 5 hours.

To harden heat to 1525°F and quench in oil. (Most want you to hold the 1525 for 15 or more minutes)Temper as needed (minimum of 350°F).

According to the Bethlehem book "Modern Steels - Handbook 3310" the following are APPROXIMATE Rockwell C hardnesses of oil quenched 5160 for various tempering temperatures:

SAE 5160
Temperature Hardness Temperature Hardness
400°F 59 Rc 900°F 42 Rc
500°F 57 Rc 1000°F 37 Rc
600°F 54 Rc 1100°F 32 Rc
700°F 52 Rc 1200°F 28 Rc
800°F 49 Rc 1300°F 20 Rc
 
Many thanks to all for your advice and special thanks to Phillip for the specifc answer - soak at 1525 for 10-15 minutes and temper at 350 degrees (for how long?? 1 hour??). I think I'll use the electric furnace instead of the propane forge - better control. I will be back and will post the results - maybe even a picture, if I don't destroy the blade.
 
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