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Warner Smith

Heat treating O1 steel. Can I?

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I have a blade made from O1 steel (stock removal) that is ready for heat treating.  As a newbie,  I'm scared to death to get treat it myself.  My biggest concern is not knowing the actual temperature of my forge/the blade.  A friend on here told me that I need to put the blade inside of a pipe in the forge,  and get a thermistor and digital thermometer so I can KNOW what's going on in the forge.   So I need some assistance sourcing those  (which ones on Amazon?).  I've been planning on sending this out for heat treatment, and still may (with a bowie that I'm planning to make), but wanted some opinions from the community here.

     Thanks in advance, 

           Warner 

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What you are looking for is pyrometer, which is the tool that displays temperature, and a K type thermocouple, which is the tool that senses temperature for the pyrometer to read and display.  You want one that will read up to 1300 C/2372 F, though if you can get one that will read up to 1372 C/ 2301 F, even better.  The hand held laser types don't read high enough to be useful :(,

 

Geoff

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That looks just about like what I have and should do the job for you.  One problem with using a forge for heat treating a blade with is that the pyrometer only shows you how hot it is where the end of the thermocouple is, not how hot the steel is.  With O1 you need to be able to hold the blade at just about 1475° for about ten minutes, if I remember the formula right, to get good carbon solution without getting over saturation resulting in retained austenite.  That's not to say that you can't use a muffle tube in your forge to bring the steel up to temperature and then quench it and get a good knife.  You just might not be getting the most out of the steel.  Trying to perform a soak for 10 minutes in a muffle tube takes close monitoring and is an easy way to cause grain growth.  O1 is one of those high carbon steels that is heat treated better in a regulated high temperature oven or a molten salt tank.  Steels like, 1080, 1084, or 5160 are more forgiving in the heat treat and are better for heat treating with a gas or solid fuel forge.

Doug

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1 hour ago, Doug Lester said:

That looks just about like what I have and should do the job for you.  One problem with using a forge for heat treating a blade with is that the pyrometer only shows you how hot it is where the end of the thermocouple is, not how hot the steel is.  With O1 you need to be able to hold the blade at just about 1475° for about ten minutes, if I remember the formula right, to get good carbon solution without getting over saturation resulting in retained austenite.  That's not to say that you can't use a muffle tube in your forge to bring the steel up to temperature and then quench it and get a good knife.  You just might not be getting the most out of the steel.  Trying to perform a soak for 10 minutes in a muffle tube takes close monitoring and is an easy way to cause grain growth.  O1 is one of those high carbon steels that is heat treated better in a regulated high temperature oven or a molten salt tank.  Steels like, 1080, 1084, or 5160 are more forgiving in the heat treat and are better for heat treating with a gas or solid fuel forge.

Doug

You just made up my mind.  I'm going to send them out, even though it may just be 2 knives in O1.  I'll have a bunch in A2.  I have 24 small pieces of A2 that I plan on making Puukko knives from.  Progress on the first one so far....I'm pretty pleased with how the bevels turned out.  

Warner 

20171125_152210.jpg

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1 hour ago, Doug Lester said:

That looks just about like what I have and should do the job for you.  One problem with using a forge for heat treating a blade with is that the pyrometer only shows you how hot it is where the end of the thermocouple is, not how hot the steel is.  With O1 you need to be able to hold the blade at just about 1475° for about ten minutes, if I remember the formula right, to get good carbon solution without getting over saturation resulting in retained austenite.  That's not to say that you can't use a muffle tube in your forge to bring the steel up to temperature and then quench it and get a good knife.  You just might not be getting the most out of the steel.  Trying to perform a soak for 10 minutes in a muffle tube takes close monitoring and is an easy way to cause grain growth.  O1 is one of those high carbon steels that is heat treated better in a regulated high temperature oven or a molten salt tank.  Steels like, 1080, 1084, or 5160 are more forgiving in the heat treat and are better for heat treating with a gas or solid fuel forge.

Doug

I did buy 10 feet of 1075 (1/4" x 1 1/2").  All this O1, A2, and D2 I got for free...

Warner 

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I have not done 10 minutes soaks so far with the baffle pipe but I have done 5mins for 80CrV2 and it's definitely doable. I had the blade spine down with a bevel actually resting on the thermocouple. I can safely assume my temp reading was accurate. You will have to fart with the gas and air to maintain a stable temp though. For each normalizing cycles, I waited to I had the given temp stable enough before putting the knife in. I managed to let the temp vary by only about 5°f. 

I know it scares you but you could train your hand with chunks of waste first to see if you can nail it.

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On the bright side, O1 has a very wide hardening window. Your canola oil is plenty fast for O1. So there's no doubt your steel will harden but the quality of the grain and carbides will depend on your soaks.

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56 minutes ago, Joël Mercier said:

On the bright side, O1 has a very wide hardening window. Your canola oil is plenty fast for O1. So there's no doubt your steel will harden but the quality of the grain and carbides will depend on your soaks.

Always the encouraged, Joel.   Haha.  I think I'll send these out though...I will have too much time into them to risk messing them up.  I'll start messing with the 1075 that I bought,  and actually FORGE something eventually.  Haha.  You're a good guy though...your advice is appreciated.

Warner 

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Warner, don't be afraid of doing your own HT on O-1 in the forge with a baffle tube. I did this for a couple of years and got great  results from my O-1 blades. Did I get the optimal HT? Probably not, but there is very little chance of "messing them up" so to speak. Watch for the decalescence in the tube and quench. It will teach you a lot more about the stele than sending them out will. Take a few scrap pieces of the O-1 and practice. Break them when you at done with the tempering cycles. You will learn how to do it by eye and get a very good HT. O-1 is not a terribly difficult steel to HT by shop methods.

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