Trouble annealing 02

G

GoldSkula

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Jun 14, 2018
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So I forged a bowie knife to rough shape from 02 some time back. I normalized it 3-4 times but when I tried filing it it felt like it was almost hardened. It didn't feel quite as hard as quenched 80 CrV2 but close. The annealing temperature is 680-720°C(http://www.astmsteel.com/product/aisi-o2-steel-tool/). I have tried this many times but it is still hard. I tried it several times with lower and higher temperatures for 15-30 minutes but with no luck. Should I anneal it longer ? If so how long ?

Thanks in advance!
 
This is the Annealing process for O1 but it should be similar for O2. Alot of steels you have to cool slowly from the anneal temp or it will harden up agian. O1 says it needs to cool at a rate not exceeding 50° per HR.

“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.”
 
The heat treaters guide says 1370-1425 for O2. The higher Mn lowers the annealing temperature relative to O1.
 
“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.”
Click to expand...
1450 / 400 = 3.6 hours +2 hours minium = 5.6 hours ???
450 / 50 = 9 hours ??
9 + 5.6 = 14.6 hour total time ?
What kind of decrab. whill have that piece of steel ?
 
I just place the steel into my forge and turn the blower off. I'm not sure how long does the forge stay hot(over 600°C) but when I pick the blade from there the next morning it's soft. I haven't noticed more than usual decarb on any of my several blades that I have done this with.
 
I use my kiln with alloy steels and stuff like L6 for a fine spheroid anneal but to be honest with most carbon steels I just bring it up to roughly 1500° and bury it in wood ashes. Comes out very soft , easy to grind and drill..
I know my hillbilly anneal method sounds unrefined but it works
 
L6 is notorious of "air hardening" and I found out that was the case even with the non-moly version. What I needed up doing was heating to 1500, quenching and "tempering" at 1200. Seemed to work okay.
 
If your in a rush you can do a sub critical anneal. This will get you soft enough to drill and work.
 
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