Deep fry a knife? A Knife making question

[Chef Niloc]

I was just thinking why not temper a knife in oil, like a frialator? A frier would hold a even temp much better then a oven, would it not work better?

 

[Lefty]

I'm sure it would even taste that much better!

 

[StephanFowler]

I was just thinking why not temper a knife in oil, like a frialator? A frier would hold a even temp much better then a oven, would it not work better?

yep, works great.

in fact, if you use an appropriate oil and quench directly in to the oil from your HT oven you can get a marquench. which if done right creates Bainite instead of Martensite. (Howard Clark was a pioneer in this concept for swords) most all of Busse's knives are bainite. standard industry practice is to use metallurgical salts for that purpose vs oil because most oil gets unstable at the temperatures we want to use.

bainite is a VERY tough phase of steel, but loses a couple points of hardness.


a good friend of mine Walter Sorrells (sword smith, lives about 15 minutes away from me) quenches for 5 seconds into water and then jumps directly into a heated oil bath to finish his quench

 

[Eamon Burke]

What temp would be ideal for this Bainite formation?

 

[Larrin]

What temp would be ideal for this Bainite formation?

The temPerature varies with the steel, austenitizing temperature, and desired hardness. It's typically 400-600F for lower bainite. However, it can't be done by the end user. Once you have martensite you can't just temper some more and get bainite.

 

[Jim]

Can someone explain why the medium used for the tempering matters? could you use an inert gas or ??

 

[l r harner]

the thing with most oils is the fact that the flash point of the oil is really close to the temps most would need for tempering (i have thought aobut the frier thing but for safty in ll jsut let the kiln come down to temp and then temper

 

[Delbert Ealy]

If you really want to know more about banite then click here: http://www.msm.cam.ac.uk/phase-trans/2004/Australia.lectures.html
and download the lecture on banite. The lecture is very good.
I will tell you right now that I wish knifemakers would leave the banite alone, for knives the best microstructure you can get is martensite, no ifs ands or buts.

Back to the topic and Colins original question; fryer oil would work great, however most of us knifemakers don't have commercial fryers available. I work in an enviroment with open flame and sparks all the time and I really wouldn't want one more thing that could suddenly burst into flames in my shop. I worked with commercial fryers alot in the past too, and if I never see another one it will be too soon.

 

[Delbert Ealy]

Can someone explain why the medium used for the tempering matters? could you use an inert gas or ??

Honestly Jim, it really doesn't matter that much, its just that most knifemakers use open air (inside a kiln or oven) because it is easy, and then there are some that want to tinker with the process.

 

[Bill Burke]

I see no reason for it not to work. time at temp is wht's important not what is used to get to the temp. If I am off base here correct me Larrin.

 

[Larrin]

Bill: The heat transfer is much higher with liquid like oil than air in an oven, but that's not really important in tempering. You're just sticking it in an oven for 1-3 hours. The rate at which it first reached temperature isn't that important.

Delbert: You've been listening to Kevin Cashen too much, bainite is fun stuff, if a bit over-hyped. Certainly in kitchen knives where hardness is king there isn't much reason to heat treat for bainite. However, as you say, martensite is great.

 

[StephanFowler]

I will tell you right now that I wish knifemakers would leave the banite alone, for knives the best microstructure you can get is martensite, no ifs ands or buts.

I would agree

 

[Delbert Ealy]

Bill: The heat transfer is much higher with liquid like oil than air in an oven, but that's not really important in tempering. You're just sticking it in an oven for 1-3 hours. The rate at which it first reached temperature isn't that important.

Delbert: You've been listening to Kevin Cashen too much, bainite is fun stuff, if a bit over-hyped. Certainly in kitchen knives where hardness is king there isn't much reason to heat treat for bainite. However, as you say, martensite is great.

Larrin,
Naw I made up my own mind about this, I'm not one to buy into the idea of carrying around a sharpened crowbar.
I do agree that banite is cool stuff, especially where toughness is the primary concern.

 

[Chef Niloc]

Bill: The heat transfer is much higher with liquid like oil than air in an oven, but that's not really important in tempering. You're just sticking it in an oven for 1-3 hours. The rate at which it first reached temperature isn't that .

Let me start by saying I am not a knife maker and only know what I have read on line and seen on video.
My question was not based on how quick the blade reaches tempering temp but rather the fact that a fryer would hold a more stable temp. A commercial fryer will stay with in 5* of it's calibrated temp for hours on end a oven can fluctuate 25* or more over the corse of a few hours. I'll bet a good kiln would hold a very stable temp but I think a kiln with a good electronic thermostat would cost more then a fryer, But a kiln would be safer. I have herd that pre heating quench oil to around 200* then quench, and then temper is the way to go? So I thought a fryer might kill to birds with one stone. Just turn the fryer to 200* and then turn it up to temper. On the note of flammability I did not think it would be a issue as you already quench in oil. so the danger of a oil fire would be just as likely as in a quench? I also think that most knives are tempered between 300-400? a fryer is pretty i have never had a fryer go up in flames at those temps, only when old oil gets above 500 do to a broken thermostat or a dumb cook. I have come to know fryers as just "there" since I have seen one 5-7 days a week for 20+ years.
So how important is the the consistency of tempering temp?
And I guess if I decide to make a knife at work I could use the fryer?
I think I could also use the coal burning bread oven for forging?
Also would a blast freezer work for a sub zero treatment? -100 in 10 sec. If not the liquid nitrogen ice cream maker might work well to? The sub zero anti grill might be of use too? I have a mareana too so the 1200 ton pile driver or the press that liftes the boats into and out of the water would put a little gient to shame I'm thinking there a lot of useful things in my kitchen that would make for a good knife?

 

[Chef Niloc]

Larrin,
Naw I made up my own mind about this, I'm not one to buy into the idea of carrying around a sharpened crowbar.
I do agree that banite is cool stuff, especially where toughness is the primary concern.

Sounds like a good oyster knife!! above I sad I heve never made a knife. That not interlay true I have made oyster knives out of railroad spikes, but a oyster knife does not need to be heat treated. Soft steel and iron work great.

 

[Chef Niloc]

Ps I love the fact that a topic of heat treating brings all the knife makers out of the woodwork. I'd love to sit around and drink a few beers with you guys, bet the conversations would be very interesting.

 

[l r harner]

i guess if you think abut it we just cook steel and liek you would have ot work sugar its all the times and temps have to be met to get the steel or sugar the way you want the end product.

quenching 1500f steel in 130f oil is not much a hazard so long as you get the whole blade into the oil and dont pull it back out till its under the fash point. the oil only gains a little heat and will not boil. if you pull the blade out before it has got under the flash point you will be holding on to a flamming sword

as far as the ecoal fires oven goes if ou can controle it at temps in the 1400-1600 range then you could HT a blade of simple steel
the blast cooler would not be a help on the simple stuff but on high alloy it might help
the frier if you felt safe runnnning at temps between 350 and 450 then you might get away with it


almost makes me want to see a chef "cook " up a blade (but its not nearly in mysafe zone as i have a kiln (with added mass inside to help with heat spikes and keeps things even )

 

[WildBoar]

Ps I love the fact that a topic of heat treating brings all the knife makers out of the woodwork. I'd love to sit around and drink a few beers with you guys, bet the conversations would be very interesting.

Sounds a lot like the upcoming ECG :thumbsup2: