Heat Treat questions... (specific to 5160)

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krept

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Jan 14, 2002
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The purpose of the 5160 blade I'm using here is just to familiarize myself with the HT process. I've read before that after doing an edge quench and the blade cools down enough, one is supposed to wait 12-24 hours before performing the next quench.

1) Does anyone know the purpose of this?

I know in annealing you want to cool down the blade as slowly as possible... and in other steels like the 10xx series you want to temper right after the quench.

I tried a second quench today and left the blade in the oil for about an hour. Went out and checked on the blade, the oil felt a little warm. Checked an hour later and it didn't really change much. The oil is in a steel pan outdoors in AZ, so it probably wouldn't have cooled down much more because of the ambient temp. So I basically did a couple more cycles just to see what happens... edge quench for 10 seconds or so, then let the blade rest in oil for 1 hr. So far, I'm on #4. Again, the purpose of doing this is to test my ability to hold the blade well with tongs, check for nonmagnetic, etc.

2) I'm using ambient temp oil, probably 80-90 degrees is my guess. Is the purpose behind warming up the oil to not shock the steel as much, like with water... possibly causing it to fracture?

3) I read that the most critical time for the quench is the first second or so, when it's going from 1550/nonmagnetic to sub 900 or so estimated. Has anyone tried a really quick swipe in water for say 1 sec and then gone over to the oil so it's not as abrupt a total change as with only water? (i.e. a two quench tank setup)

4) Finally, regarding the original question... would there be any benefit to say, letting the freshly quenched blade sit in the oil for a couple minutes, then transferring over to water (warm or cool) to hasten the cooling process? Or is the slooow cooling what is important? if that's the case, why not use vermiculite instead of oil?

Thanks in advance folks... any insight is helpful!

cheers,
erik
 
Helolo Eric:
Several important factors, oil - what oil? When you heat oil, it cools faster than when cool thanks to viscosity stuff.

The reason you let them cool slow is to allow the transformation to complete as far as it wants to. Blades are always changing, multiple quench encourages completion of transformation without soaking and encouraging grain growth. The benefits are all dependent upon the steel you are using and the degree of reduction by forging. Not all 5160 is the same.

Catch my next article in Blade and you will have some ideas as to why as we know it today. BAsic information is also in my books, knife talk I and II.
 
Ed, thanks for the reply. I'm truly in awe of your experience and would like to ask many questions but I'll keep it short.

Would it be correct to conclude that after the steel reaches the same temperature of the oil, the steel still continues to change? If that is the case, it can't be fate/convenience that the optimal temperature to hold the steel at is what the oil settles to in ambient conditions... i.e. if one were to hold the oil to the initial quench temp (e.g. 130F) for 24 hours might there be a discernable difference in performance?

cheers,
Erik
 
After this I'll step aside. 5160 is rather forgiving. It makes for a very good blade steel, especially where toughness is greatly required. Properly quenched and then properly tempered for blade usage you should expect a high of about 58 HRc. It is always good practice to not allow the steel to fall below hand warm before tempering, approximately 125 degrees F but no lower before placing in preheated temper (5160 may be a unique exclusion to this). In cases that a preheated temper is not readily availble in time the steel can be held in boiling water or in an oven preheated to approximately 220 F. Regardless of the steel, leaving the steel rest in quench for hours makes no good sence to me - even if it is in the Arizona sun. There is nothing mystical about heat treating steel. Just following very basic but rigid requirements will provide success.

RL
 
Once the steel reaches the temp of the quench oil no further change occurs.Tempering should always be done immediately.Doing a second hardening after a 24 hour wait does nothing at all, you can do it right away.... I have done the water then oil quench but not on blades .We were trying to save a customers parts since he had picked the wrong alloy.It took a bit of experimentation and cracked parts to get it right.....You need to do a lot of reading about heat treating !!!
 
Thanks again.
:D
Mete, trust me, I've read a lot of stuff you have written both here, TFL, THR, etc. Good info. I couldn't find anything specific to 5160, however.

In researching the heat treatment process specifically to 5160 I thought I read that the added chromium allows for a more complete transformation (hence it's response to multiple quenches) than 1060 and this also makes the difference in allowing the 5160 to cool.

What happened in my searches over the past couple of days that I saw multiple references to "quench, then temper to 375 (or so) for at least 2 hours). One thing that was confusing me is WHEN to temper, so I continued to dig. (thanks for the info RL)

I searched and found at least a couple references to letting the steel cool down in the quench overnight. One of them is Ed Caffrey... here is what he said in a post related to 5160:

do not know the EXACT time required between quenches, but have narrowed it down to letting the blade cool down in the oil, AT LEAST until the oil is at room temp. (I usually schedule my quenching for the last thing in the evening so the blades remain in the oil at least over night) Through the testing, it was determined that each slow cool down in the oil acts similar to an annealling cycle as far as grain size reduction is concerned.......without any softening taking place.
Click to expand...

Interestingly, I also saw a reference to not letting the oil reach past 190F or otherwise it would cool the steel down too much, didn't think of the viscosity thing, so I'm guessing there is also a sweet spot temp to get the oil at as well.

I'm really starting to love this stuff, thanks again.
 
More info I used:

Most of the blades we make are differentially hardened by edge quenching (see Quenching Methods and Steels) three times in heated oil, with the blade being allowed to cool in the oil overnight each time. The interval between quenches is no less than 24 hours.
Click to expand...
from http://www.tellercanyon.com/process.html (looks like they make nice blades)

from http://www.knivesby.com/Ed-Fowlers-heat-treat.html
Quench the blade in the oil to the depth you wish to harden. When it quits fuming, fully submerge the blade in the oil and allow the oil and blade to come to room temp. Blades then go back to the home freezer overnight. I try to keep 24 hour cycles. repeat the quench cycle for a total of three quenches.
Click to expand...
(it looks like the blades are REALLY brought to low temp before temper)

http://www.caffreyknives.net/journeymanarticle.html had the original info I saw:
Once the entire edge is an even heat, quench by placing the tip into the oil first, for a slow count of 7, and then rock the rest of edge into the oil for another slow count of 7. Continue rocking the blade back and forth in this manner until all the “fumes” have ceased. At this point slide the blade off the limiter plate, and allow it to cool COMPLETELY in the oil. Repeat the process twice more for a triple quench
Click to expand...

cheers
 
" slow cool down in the oil acts like annealing as far as grain size" -absolutely not - they are not related. ....The 24 hours may be there for convenience but does nothing for the steel....It is doubtfull that the freezer will do anything for 5160.
 
RL,

No mystery here. Just good sound heat treat. Tell it like it is. Over what ancient fire was the technolgy discovered for heat treating our blades?

Hope they were lucky enough to have had hot dogs!

Fred :D :D :D
 
I have noticed no benefit from deep cryogenically treating 5160.
-------------------
Here's one that worked well for a fairly large blade of 5160:

Preheat: 1150 F / 7 minutes
Austenitize: 1525 / 7 min
Oil Edge Quench
Temper: 400 / 1 hour
Temper: 375 / 1 hour

This blade took second place in a cutting contest of about 10 blades of different steels.

RL
 
Hello Eric:
Now you have to decide, are you going to follow theory or search for turth?
The only way you can find truth is by testing your baldes for what you want them to do.
By testing blades 5160 blades, I have determined the following:quench-
Heat the cutting part blade (lower third or even to half) to critical, hold for a very few minutes to even up the heat, then quench in Texaco type A oil pre heated to 160 degrees (for my steel worked my way), this slightly increases cooling rate. Once the blade has quit fuming, fully submerge the blade in the oil and let it cool to room temp. If you want to try for a few more cuts in testing, put the blade in the home freezer over night then quench again. Three quenches gives the biggest bang for your buck. For some reason four is worse, 5 just a little better, sometimes.
This applys to one inch John Deer load coltrol shafts that have been forged to shape very carefully, keeping the temp below 1700 degrees f. Over heat and you will have trouble with blades cracking if you do not temper immediately. I try to keep my forging temp around 1625 (slag comming off the blade like fine snow flakes), this gives me a 75 degree margin of safety, and forge from quality round (larger) stock and you will have no trouble with blades cracking. If they do it is probably due to the quality (nature) of the steel you are using, or forging too hot. Work the steel as much as possible, move the edge in and out - more than necessary, this is to develop the maximium benefit of forging. Don't forge too hot or too cool, when it stops moving quit forging, you can softly straighten a blade at cooler temps, but don't try to move the steel.

Forge evenly from side to side, as observed by relative displacement of the steel. This is a combination of keeping the temp the same for the first blows of the hammer and working one side then the other. Don't be afraid of heating too often, the more thermal cycles coupled with forging, the better - as long as you don't overheat.

Rex shot a chemistry on 52100 5 1/2 inch round stock, then on a finished blade, there was no measurable corbon loss and as close to full conversion as they could measure.

When I temper my 5160 blades they will do the 90 degree flex and more with a three 350 degree two hour draws when allowed to come up to temp slow and cool slowly. Just for the fun of it we once flexed one to 90 without benefit of tempering after three quenches in three days. I would not recomend this for a using knife.

My strongest recomendation is to thoroughly test your blades yourself and come up with your own results. Let theory explan what happened, but testing guide your efforts.
Good Luck and please keep us informed as to your results.
 
awesome info, I really appreciate it.

this is literally my first ever try at a heat treat. Heck, I haven't even finished a knife yet. I'm trying to get as much info as I can... i.e. "standing on the shoulders of giants" so I can cut as much out of the learning curve as I can and hopefully contribute meaningfully to discussions years from now.

thanks again for sharing

cheers,
Erik
 
Good idea Krept... I might suggest it is beneficial to carefully choose the shoulders of those you stand upon :D

Nick
 
Krept, I really don't want you to screw up your first blade heat treat. It will be the difference between a knife and something that only looks like a knife. As Mete says study all you can about it, and as Ed says test. The testing will come as a matter of course. It will be automatic to you , especially in the long beginning. I have this to say and hope you will remember: get it in quench very quickly and get it in PREHEATED temper before falling below hand warm (150 F absolute high - 125 absolute minimum). Do not allow it to fall below about 125 F before placing in preheated temper. Preheated temper means the tempering oven is already at 400 F before the steel is ready to be placed into it.

RL
 
Roger ,least anyone have a misunderstanding -while I hope that Krept will study extensively I hope that he also TEST ! He could follow your lead because you did study and test. You separated out the myths and also found what worked for you with your equipment and methods .
 
Hey, There's something here I don't understand.

Why would you preheat your "temper" (I'm guessing that means oven?BIt it could mean some other process like salt.) to 400F.

I find that 400F is a bit high for tempering 5160. Generally 350F does a good job. It could be I'm just not getting the refference or your process Roger.

I have heard of folks putting steel in the tempering oven right away. But I have never done so. At the blade school somebody mentioned that there were a whole bunch of stresses after Hardening and that blades will crack if you don't temper immediately.
I tried to make that happen with a piece of 52100. I ran it through 7 hardening cycles. I waited 24 hours between each cycle. I couldnt get it to crack. Did you have a different experience?


Eric,
I noticed you are doing your homework. Good for you! I look forward to seeing you progress and succeed!

A couple of thoughts...

Some of the sites you referenced...about Ed's methods are just flat out wrong. If you want to know about Ed Fowler, then ask him. He laid out his basic formula right here. The reason I say this is that a lot of folks read about it on the Internet, and try it, and struggle. They used the wrong oil, forge too hot or cold, start with poor steel, and then get pissed cause they can't make it work. Ed's recipe is specific to a lot of variables.

The next thing you can do to make your life easier, is to keep meticulous notes. Slap a number on your blades and follow their path all the way to the finished knife. Record everything that you did at each step, and then take time with the finished knife reveiwing your process.

Test your knife before you have polished it to the final sheen. This will help you change geometry or decide the blade is not up to standard before you finsih it.

Be consistant in your tests. Use the same media. That way you have a good comparison, historically, of your progress.

IN any field in the world where passion is the key factor in success, there are a lot of opinions flying around, tempers flare, names get called, personal attacks are made, in generaL IT'S A HELL OF A GOOD TIME!

Every comment, every bit of knowledge from the old master to the shiny new rookie, is valuable, and worth listening to.

The great thing is, after you have done all the homework you get to go in the shop and play. When you do, lock the door behind you. Leave all of the personalities and the controversy outside. Forget the books, forget the knowldge. Let the steel guide you. Listen,watch, pay attention and learn.

No good teacher wants you to fall into step and follow mindlessly. Find your own way. All of the information here and elswhere is just a beginnning.
Experience will shape your knives more than talk.

Welcome! Good luck! Now go make some knives!

You are welcome to call the house if you get stuck.

Shane
 
Due to my job, I put in too many hours to make knives in the summer, so I am just working on ideas for knives to make this winter.

I plan to do a few knives with two different types of steel forged into a single blade. My hope is to learn a bit about how Japanese blades were made like this.

I like to use John Deere Load shafts, so thats clearly going to be one of the steels I use to make my next blades, But Im not sure what other steel would go with the 5160 Load shaft?

I hope to forge one steel that is able to get very hard around a softer steel that is known for being very strong and bendable...

I believe that 5160 steel would do well as the inner steel that is kept soft,,,But what steel shall I forge over the top of the 5160 that is known for getting very hard?

Also, I plan to copy the Jananese way of useing a clay-covered blade in a water quench...Now I know that all the experts say that 5160 is best quenched in warm oil,,,But the way I want to get around this is by keeping the inner core of 5160 from getting near the water , and haveing the outer skin steel being a water-quenched type steel.

So what do you think of this idea?

Would 5160 forge weld to a (water-quenched) harder steel?
and
What steel would you suggest I use to wrap around the softer 5160?
 
Are you talking about damascus or folded steel? Or laminated ? Laminated usually has a hard center covered on each side with softer steel.I wonder if anyone has done a 5160/52100 laminate.
 
September 24 Bill Burke and I will host our first symposium about the high performance blade at my shop. Three men who have voiced a high level of interest in the high performace knife will be attending. This is the first such hands on debate to occur with more than one on one. It will be interesting,

Rex and I wrote letters and spent many hours on the phone discussing method and the High Performace blade. We did not communicate nearly as completely as we thought we had. Rex came to my shop twice and each time we both learned a lot. I have learned from all who have forged with me.

The route to the high performace blade is not easily charted. There are many events that we do not think to mention, simple stuff that when repeated many times is not readilly brought to a cognitive level, at least when writing about it. We will all keep notes and dsicuss what we saw regularly.

Should be interesting and will pave the way for many more hands on experiences. Bill Moran taught in such manner that when I left his tutorial I had more questions than answers, that mental environment has not changed.
Thus is the goal of our endeavors.
 
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