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Chef knives and temp control


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Hey gents! Been a while since I've posted over here.  Had an injury and couldn't forge for a  while but I'm back. Got a  couple of oddball questions for yall. 

1. Chef knives. Could use some help. Just tried forging one with 1in wide x 1/4 thick cru forge v and it was pretty rough. What is everyone's preferred steel for chef knives and what size stock do you prefer? 

Here's my first chef forged 

 

2. Temp reading and heat treating 

What does everyone use for reading temps and controlling heat during HT? 

I just built a blown burner and I'm waiting on kaowool to finish a real forge. (I've been using a 2 brick forge) I was thinking of doing a PID controller but kind of thinking it may be overkill. Now I'm thinking a good thermocouple (omega) and a good pyrometer should do the trick. I wanna use w2 and 1095. What's everyone's thoughts? 

Thank you!

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Here's what I use. A 10$ thermocouple and 10$ reader. I used the decalescence to confirm its accuracy, it is spot on. Though I must confess it isn't ideal for blades longer than 5" in my case. I have to swipe the blade in the tube in order to heat the whole blade evenly, but that's already the case when you heat it directly in the forge anyways.. 

 

Edited by Joël Mercier
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That's pretty much how i planned on setting mine up. Except have the TC come In from the side . 

How do you test your hardness? I've had a difficult time selling forge HT blades cause a lot of people dont seem to trust it. So I'd like to have numbers to back it up. 

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The only chef's knife I have made was from 3/4" round W-1.  A power hammer is really helpful for taking that down to 1/8" x 2". :lol:  My HT setup is much like Joel's, except the pipe is in a coal forge and there is no thermocouple.  I go by decalescence alone, because it's really all you need.  

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Did you watch YouTube vids about it? If not, you should. It's fairly simple but you have to do it in the darkness or you will not see it. 

Edit: a 5/8" rod will be tricky to forge into a 2" wide blade. Try 3/4" instead.

Edited by Joël Mercier
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1 hour ago, Justinschmidt said:

Haha yeah I actually thought about getting some 5/8 o1 round but was talked out of it by a buddy. I understand what decalescence is but how do you use it to HT? 

Just to put the answer on record.

The dealesence point is what you want to see both for thermal cycling to refine grain and as an indicator that the steel has reached quenching temperature.  After the quench and the blade has cooled down below the end of the martensite phase and has reached hardness it is then immediately put in the tempering oven at the temperature that matches the desired final hardness.

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Yeah I use the decalescence when I 3x normalize before getting to aus temp to quench. But I never knew about using it to quench.  It makes sense but at the same time seems like you would be to late by the time it converted then there would be pearlite in there. 

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36 minutes ago, Justinschmidt said:

Yeah I use the decalescence when I 3x normalize before getting to aus temp to quench. But I never knew about using it to quench.  It makes sense but at the same time seems like you would be to late by the time it converted then there would be pearlite in there. 

Pearlite is a result the speed of cooling hence the need to "jump the pearlite nose" . Different steels have different needs for optimization during that process hence different quenching oils. An example is 1095. For quite a long time this factor was "underrepresented" in the Thinking about hardening and 1095 was thought to be a great beginners steel because it had the highest carbon content of the 10xx series. Higher carbon =better edge was the thinking. Nesides having more carbon yhan will easily go into solution, .95 % as opposed tothe .84% that readily goes in to solution, 1095 is finicky about quenching speed. It wants to get over the pearlite nose in a bit less than 1 second for optimal . From about 1500 to under 800 in less than a second but the rub is that too sudden, like a water quench, and it is prone to cracking in blade dimensions. It I a finer balancing act than I like given other steels optimize as well, and have the useful carbon needed, with more forgiving quench requirements.

I just use that as an example of the variations and importance of knowing what an individual steel wants in order to avoid pearlite in the quench.

It is a matter of understanding the phases steels go through in response to temperature and the use or controlled interruptions in the phases for our purposes.

Not a metalurgist but I did stay in a Holiday Inn several times.

Edited by Vern Wimmer
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Decalescence is the phase change on the way up, when the shadows in the steel disappear indicating full transformation of the crystal lattice to FCC, or austenite.  This is time to quench, thus converting the austenite to martensite.  Depending on your alloy, you have anywhere from under a second with 1095 to over a minute with air hardening alloys to miss the nose of the curve.  Cru-Forge V allows you to have around 30 seconds to drop the temp from 1550 F to under 800 F.  

Recalescense is what you see on the way back down as the crystal matrix shifts back to BCC, or perlite/ferrite. 

I'm not a metallurgist either, but I study it as much as I can.  Once even at a Holiday Inn! :lol:

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I love when I see people say "I'm not a metallurgist...".  Especially when I get to follow up with this:

I am a metallurgist, and they covered it pretty well.  B)

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Yeah that's what I was worried about things like 1095. I REALLY want to use w2 not just for hamon purposes but I've heard excellent things about it. 

So decalescence heat treating. Get steel above critical,  wait for shadows to disappear, quench. I like it. 

But what do you say to customers who dont trust this sort of HT because I'm a newbie maker? 

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3 minutes ago, Jerrod Miller said:

I love when I see people say "I'm not a metallurgist...".  Especially when I get to follow up with this:

I am a metallurgist, and they covered it pretty well.  B)

Haha that's awesome! So you dont really need a pid controller to get optimized heat treat. Good to know

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You can get hardness check files, or send a blade out for testing and keep the report to prove your process works.  You can also do the brass rod and other cut tests with the blade in front of them.  But some people just won't be convinced, and won't buy.  Other will.  

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2 minutes ago, Justinschmidt said:

Yeah that's what I was worried about things like 1095. I REALLY want to use w2 not just for hamon purposes but I've heard excellent things about it. 

So decalescence heat treating. Get steel above critical,  wait for shadows to disappear, quench. I like it. 

But what do you say to customers who dont trust this sort of HT because I'm a newbie maker? 

You can always make a video about it after some practice when you get confident enough in your experience. 

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Also keep in mind that some alloys like a soak at temperature to dissolve carbides and get more carbon into solution.  A temperature readout is generally good enough for this, as you should be able to regulate the blade temp reasonably well.  You just don't want to over shoot too hot due to grain growth.  

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Great points gentlemen.  And with kitchen knives I dont have to worry about Yahoo's trying to chop through metal I beams and trying to cut down a tree with an edc lol 

Jerrod also good point. I'm just gonna get a hand held pyrometer just to make sure something like that doesn't happen.  

I really appreciate the input and help gentlemen.  Calmed my nerves a bit 

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6 minutes ago, Justinschmidt said:

Calmed my nerves a bit 

Relax.  Don't worry.  Have a home brew.  Wait, wrong hobby.  

But yeah, don't worry too much.  Back when people had to trust their lives to a blade (more than they do today), thermocouples and PID controllers didn't exist (but then again, they're all dead ;)).  And often the difference between what one can do with minimal control and perfection is pretty slim, especially when compared to a blade from a big box store.  

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2 hours ago, Justinschmidt said:

Yeah that's what I was worried about things like 1095. I REALLY want to use w2 not just for hamon purposes but I've heard excellent things about it. 

So decalescence heat treating. Get steel above critical,  wait for shadows to disappear, quench. I like it. 

But what do you say to customers who dont trust this sort of HT because I'm a newbie maker? 

Oh I am going to get in a pot of trouble with the knifemaking world here but I have faced that question and pretty much come to a speech (I just saw Jerrod's excellent answer btw) I point out that IMO while factories require certain uniformity in process that does not always equal the highest possible performance in a steel, just the easiest manufacturing process. The 1095 I mentioned is a prime example. Used for years by many  factories the need for uniformity in production leads to compromises. A certain well known knife has always been, and I have 4 examples, too soft for my purposes and I suspect, to avoid manufacturing loss, they let it linger in the nose too long. Other things done that customers may hear about are pure sales hype. I have seen no evidence put forth by real metalurgists I trust that so called "cryo treating" has any great affect on most basic carbon steels. It is IMO a "must" to optimize some stainless steels, but that is apples and oranges since forging stainless is problematic. Yet we see several factories advertising "cryo treated 10xx". 

The carbon steels are heat treated and hardened in response to physical changes in their structure and those changes has very observable effects on the steel without recourse to numbers those changes existed before thermocouples were invented. I actually prefer to say " I saw decalescence occur with my own eyes" than to say "I put it in an oven, closed the door and set it for the right temperature". Not meaning to be dispariging about the high temp ovens at all. I am heating the steel to get an effect and it is one I can see. Of course if I was paying a crew of employees to do it I might find it a lot more cost effective to use an oven and thermocouple.

1 hour ago, Vern Wimmer said:

Bad craziness man.

 

Edited by Vern Wimmer
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It makes a lot of sense to me.  I think people think too much about numbers and perfection and things. In reality the difference between steels is pretty minimal.  But we all want to do the absolute best job we can.  I'll get a pyrometer just to verify everything when heat treating 

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13 minutes ago, Justinschmidt said:

It makes a lot of sense to me.  I think people think too much about numbers and perfection and things. In reality the difference between steels is pretty minimal.  But we all want to do the absolute best job we can.  I'll get a pyrometer just to verify everything when heat treating 

I have read a few times a hand held pyrometer isnt gonna help much in blade making. I think it has something to do with the scale screwing with the readings.

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Hand held isn't quite descriptive enough.  You can get a hand held IR thermometer or a hand held reader for a thermocouple wire.  I would always suggest avoiding IR for high temp applications (>1000 *F).  

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