5160 quench and tempering

gga357

gga357

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I have been trying to get all my ducks in a row. I decided to use 5160 to make my first knives. Throwers/general purpose utility knives. So I have been reading everything I can on 5160 HT. The question I have is the difference between edge quench and spine tempering or drawing. (Forgive my lack of knowledge with respect to terminology)

So my understanding is if you edge quench then you get a layer of martensite followed by pearlite. I imagine there is a mix of different structures in the transition.

If you do a normal quench then "draw" (I think that is right) the spine you have martensite through out the blade but are tempering the spine more than the edge.

Also if someday I build a HT oven, what is practical number of blades that can be HTed at once? Assuming the oven is large enough. is it practical to quench 2? 4? 6? blades in quick succession?
 
There are folks who will expand (or correct me) on this but...

gga357 said:
I have been trying to get all my ducks in a row. I decided to use 5160 to make my first knives. Throwers/general purpose utility knives. So I have been reading everything I can on 5160 HT. The question I have is the difference between edge quench and spine tempering or drawing. (Forgive my lack of knowledge with respect to terminology)
Click to expand...

5160 might not be the best steel to start out with. It is not the easiest to heat treat with a simple forge. With its low carbon content and alloying (chromium) it needs more attention than lets say 1070/80/84.

gga357 said:
So my understanding is if you edge quench then you get a layer of martensite followed by pearlite. I imagine there is a mix of different structures in the transition.
Click to expand...

Yes there is...... oh boy..... this could be interesting. selective hardening is the term used, I believe.

gga357 said:
If you do a normal quench then "draw" (I think that is right) the spine you have martensite through out the blade but are tempering the spine more than the edge.
Click to expand...

That is correct, too.... a homogenous blade with a select temper.

gga357 said:
Also if someday I build a HT oven, what is practical number of blades that can be HTed at once? Assuming the oven is large enough. is it practical to quench 2? 4? 6? blades in quick succession?
Click to expand...

That has more to do with your quench tank set up than the HT oven. Everytime you quench a blade, you raise the temperature of the oil and change the characteristics of the quench.


Rick
 
Thanks for replying.

Rick Marchand said:
5160 might not be the best steel to start out with. It is not the easiest to heat treat with a simple forge. With its low carbon content and alloying (chromium) it needs more attention than lets say 1070/80/84.
Click to expand...

Well the suggestion of 5160 came from my idea of making throwers rather than buying them. Plus a thrower as first knife theoretically means simple profile and simple bevels.

Rick Marchand said:
That has more to do with your quench tank set up than the HT oven. Every time you quench a blade, you raise the temperature of the oil and change the characteristics of the quench.
Click to expand...

Got ya. Make sense. What about time between knives and from first to last? Heat loss of the blade was a concern.
 
Yes, that's certainly something to think about, too. The easy answer is treat one blade at a time... but I'm sure there will be some alternatives (especially if you make one with a PID controller) presented once some other's start chiming in.

Rick
 
gga357 said:
Also if someday I build a HT oven, what is practical number of blades that can be HTed at once? Assuming the oven is large enough. is it practical to quench 2? 4? 6? blades in quick succession?
Click to expand...

The most that I've done at one time was 5 or 6 and I didn't run into any problems. The volume of quenching oil you have on hand is probably the biggest factor.
 
I've been using a small 110V jeweler's burnout oven for heat treating blades. It takes a fair amount of time to come back up to temp, after removing a blade, before quenching the next one. Presumably a bigger, more robust oven/kiln/furnace would lose less temp and recover faster.
 
Mitchell Knives said:
The most that I've done at one time was 5 or 6 and I didn't run into any problems. The volume of quenching oil you have on hand is probably the biggest factor.
Click to expand...

Keep a Plastic coke bottle of water frozen. if your oil gets too hot dip the whole bottle in to cool it quickly, but not too long lol. Remember to clean it really good before you put it back in the wifes freezer. I put mine in a gallon ziploc bag. then into the freezer.
 
Rusty McDonald said:
Keep a Plastic coke bottle of water frozen. if your oil gets too hot dip the whole bottle in to cool it quickly, but not too long lol. Remember to clean it really good before you put it back in the wifes freezer. I put mine in a gallon ziploc bag. then into the freezer.
Click to expand...

Thanks! That's a really good idea; I'll have to try that.
 
I have a 4400 watt 220v oven. and 5 gallons of oil. I have done 5 blades at a time. I open the oven grab a blade and as I move it to the oil the door closes on a weak spring. After that blade is quenched, the oven is back up to heat. I give it a couple minutes and then do another. The steel and refactory in the oven will not cool as fast as what the thermocouple reads. The thermocouple is a small piece compared to a blade and is affected more by the cool air that enters than the blade. Plus, I believe once the carbon is in solution its not going to do anything bad if the temp drops 30 decrees for a short period. Like 1095, yes it has a very short window, but nothing needs to happen real fast from 1475 to say 1350. I used to make getting the blade from the oven to the oil a mad dash, thinking I only had .8 seconds. Not true, its point .8 from under 1200 to about 900. Before and after the time lines are greater. I don't waste anytime, but, I don't go nuts.
 
Rusty McDonald said:
Keep a Plastic coke bottle of water frozen. if your oil gets too hot dip the whole bottle in to cool it quickly, but not too long lol. Remember to clean it really good before you put it back in the wifes freezer. I put mine in a gallon ziploc bag. then into the freezer.
Click to expand...


That sounds like a great idea.
 
ib2v4u said:
I have a 4400 watt 220v oven. and 5 gallons of oil. I have done 5 blades at a time. I open the oven grab a blade and as I move it to the oil the door closes on a weak spring. After that blade is quenched, the oven is back up to heat. I give it a couple minutes and then do another. The steel and refactory in the oven will not cool as fast as what the thermocouple reads. The thermocouple is a small piece compared to a blade and is affected more by the cool air that enters than the blade. Plus, I believe once the carbon is in solution its not going to do anything bad if the temp drops 30 decrees for a short period. Like 1095, yes it has a very short window, but nothing needs to happen real fast from 1475 to say 1350. I used to make getting the blade from the oven to the oil a mad dash, thinking I only had .8 seconds. Not true, its point .8 from under 1200 to about 900. Before and after the time lines are greater. I don't waste anytime, but, I don't go nuts.
Click to expand...

Thanks for sharing your methods. Sounds reasonable to me.
 
Also if tempering say with edge in water. Or drawing the spine how do you how long to hold the torch. Seems like most tempering cycles are somewhat long. How do you create a repeatable procedure for this methods?
 
You can't.... it is a give and take. Some of the experienced guys can get a pretty good temper with a torch... but it takes time and patience. If you go too fast, you only get a surface temper. You need to bring it up SLOOOOOOOOOOOOWLY to achieve a deep temper. Even then, it will never be better than a proper soak... but different situations call for different approaches.... you can't selectively spring temper the spine of a knife in a toaster oven. The torch should be a compliment to the tempering oven, not a replacement, IMO.


Rick
 
Just thinking here. If I had a block that heated to about 800 F or capable of sustaining heat via coils or someother method, then I could set it on top of the spine while the edge is in water. Wonder if something like that would work.
 
I've seen some use heat tongs. These are tongs with larger pieces welded/fastened to the ends. These larger pieces are heated in the forge, the placed on either side of the spine. I've not tried it, but the heat is said to be more controlable this way.
 
I've used both methods and did the cut and bend on both. The problem I had with the fully quenched blade and drawing the spine was getting it to hot while drawing the spine and having it reharden on me, I think this is from the chromium in the 5160. My best results came from an edge quench. My suggestion is try a couple blades using both methods and see what works best for you. Good luck and have fun.
 
Thanks Me2 & Mike Q. Does anyone know, what is the structure of a spring? Is it Martensite through out and temperted to a lower RC.
 
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Just to clarify, when I drew the spine I used a torch. Me2's suggestion of using tongs with blocks would be the way to go and prevent rehardening.
 
I'm planning on making a set of basic throwing knives for a friend of mine out of 5160. These will be profiled, rough ground, given a proper soak at temp in my Evenheat oven(forget what temp, exactly, for 5160, though), full quench into Park's AAA, and then get 2 tempers of 2 hours each. I anticipate no problems, and if my friend is able to break these suckers, I wanna hear the story. ;) :)
 
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