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Heat treat O1 problems


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Hey all! Having troubling hardening O1.

I have a 6mm thick bushcraft blade that’s normalised and annealed… soaked it at 815 Celsius for 15 mins (in a pipe in the forge) and quenched in canola oil at 40 Celsius. But no luck! File cuts fine… I tried with a smaller piece of steel that  hardened fine. Maybe 6mm is too thick? And is not quenching/cooling fast enough? 
Thanks for your help!

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Why do I keep seeing the same post over and over?---This is not a chat room.  Folks will answer as it suits them.

Are you heating the steel to non-magnetic before quenching?

Are you getting it in the quench FAST---a second or two.

Are you sure it's O1, have you successfully hardened it before?

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I only see two posts in his history Thomas and only one visible. Perhaps he had to change his login and rejoin?

I recognize the question and writing style. Almost a verbatim repeat IIRC.

Joshknife: Asking the same question repeatedly won't get an answer it will get you ignored. 

 

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I saw both threads, but now one has been removed, because posting the same thing in more than one section is frowned upon. I thought 01 was air hardening but after looking up the properties and came up with this from Hudson tool steel. It is oil hardening.

Quote

 

Preheating: Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1200-1300°F (649-704°C) and equalize.

Austenitizing (High Heat): Heat slowly from the preheat to 1475-1500°F (802-816C)

Soak for 30 minutes for the first inch (25.4 mm) of thickness, plus 15 minutes for each additional inch (25.4 mm).

Quenching: Oil quench to a temperature no lower than 150-125°F (66-51°C).

Note: O1 is somewhat prone to quench cracking, especially if there are significant changes in section thickness and sharp internal corners. The oil quenching should be performed so that the heat removal is as uniform as possible in all areas of the part being quenched. Be sure to remove the part from the oil before the temperature drops to ambient temperature. Hot oil at a temperature of 300 to 400°F (149-204°C) is recommended.

Tempering: Temper immediately after quenching. Do not allow the part to cool below 125°F (51°C). The typical tempering range is 350 - 400°F (177 -204°C). Hold at temperature for 1 hour per inch (25.4 mm) of thickness, 2 hours minimum, then air cool to ambient temperature. To minimize internal stresses in cross sections greater than 3 inches (76.2 mm) and to improve stability in parts that will be EDM’d after heat treatment, a soaking time of 4 to 6 hours at the tempering temperature is strongly recommended.

Cryogenic Treatment: Refrigeration treatments should typically be performed after the temper, and must be followed by a second temper.

Annealing

Annealing must be performed after hot working and before re-hardening.

Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1425 -1450°F (802-816°C), and hold at temperature for 1 hour per inch (25.4mm) of maximum thickness; 2 hours minimum. Then cool slowly with the furnace at a rate not exceeding 50°F per hour (28°C per hour) to 1000°F (538°C). Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be a maximum of 212 HBW.

 

 

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5 hours ago, ThomasPowers said:

Why do I keep seeing the same post over and over?---This is not a chat room.  Folks will answer as it suits them.

Are you heating the steel to non-magnetic before quenching?

Are you getting it in the quench FAST---a second or two.

Are you sure it's O1, have you successfully hardened it before?

Apologies! Thanks for your replies. not trying to spam people. New to the forum. Realised the post was in the wrong sub-forum…

Successfully hardened a smaller off cut from the billet. Getting it in the oil within a second or so… (non magnetic) I’m pretty stuck!

Maybe O1 is still softer than a chainsaw file after quench? 

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Unless this knife was stock removal it's possible you have a layer of decarburized steel that's softer with harder steel underneath.

You're giving rather specific numbers. How do you know you're at 815C? If you're using a magnet, just bear in mind that nonmagnetic is the lower critical temperature and (in general) the quenching temperature is 90-150C hotter than that. Those sorts of differences can be hard to tell by eye, but just keep that in mind.

Personally, I would skip the soak. IMHO with thin cross sections like a knife it's more likely to cause problems than provide a significant benefit, even with a muffle.

As quenched O1 should skate a chainsaw file.

4 hours ago, Irondragon ForgeClay Works said:

I thought 01 was air hardening

O series tool steels are oil quenching

W series are water

A series are air

I believe for large cross sections and/or simple geometries there are multiple quenchant options.. I would have to check my book for examples. 

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Thanks for the help everybody!

Success! The blade was stock removal. I have a thermocouple that I run alongside the blade when heat treating… skipped the soak time and got it a little hotter… seemed to do the trick. Thermocouple might not be that accurate after all…

Could be worth snapping to check the grain structure and trying again? Hopefully wasn’t too hot! 

Thanks for your help!

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1 hour ago, BIGGUNDOCTOR said:

O1 will air harden in thinner sections.

This characteristic would cause me to heat treat it before grinding the blade. 

Bear in mind I'm not a bladesmith guy but I have heat treated a thing or two.

Frosty The Lucky.

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