Thread: O1 heat treating problem

Hi Gents!

I'm in big trouble.



I made the following process:

normalizing: none.
soaking: ~805C/1480F, 15 min.
quenching oil: 50C, 30-40 sec.
tempering: after cool enough to touch, 205C/400F, 2x1h (between cooling to room temperature)

It seemed all right but I can't sharpen the blade. The edge is very sensitive (see the pic). What did I do wrong?

More picture from the heat treatment process (on the first pic: the first few minutes on 1480F):



Thank you in advance for your help!

If Bruno doesn't see this maybe you should PM him

Mike Blue should be able to help too. Between the two of them, I'm sure they'll get it figured out.

Unfortunately I'm much more of a practitioner of the eyeball and magnets approach to hardening, so I won't be much use at all to you. However, what you describe does seem to me to be pretty much by the book.

It all sounds right to me, the only thing that comes to my mind, is how thick was the edge prior to heat treat.

I started off having trouble/inconsistent edges with heat treating O1. I was not leaving a thick enough edge for the long soak of an O1 heat treat. After I started leaving more meat/steel on my O1 blades my troubles went away.

Charlie

Thank you guys for the very quick answers!

Charlie,

I forgot to describe this: the edge thick was 0.03145 in (0.8mm). One more thing, I may have been overheated during polishing but I cooled down all the time?

It may not be heat-treated again, just a few tenths removed from the bottom?

.8 is about the limit of what I would do in your setup. There are 2 main issues: your blade is exposed in the fire, so the surface will be affected and may end up with less carbon. Secondly and more importantly: the edge behaves like a cooling fin. The time you need to take it out and get to the quench tank may air cool it below critical temperature. Leave a bit more thickness to the edge to overcome this problem. Another thing: after HT, you need to remove just a little bit of material from the edge itself because the surface area of the edge itself will have lost carbon.

If you have overheated > 200 C after HT, then your blade is done for. Nothing will recover from that except doing HT all over. Did the blade discolor during polishing? If you saw colors on the steel, you did. If not, then you didn't.

Now in terms of recovering: take 1 mm from the edge and see if the resulting edge passes the spark test. If it does, re-grind your razor and hone again. If it doesn't, then do the heat treatment again.

Also a soak of 15 minutes might be a bit long for something so thin. I usually do just 5 minutes or so (counting from the time the edge section gets the correct temperature)

Bruno, thank you for your quick help!

Originally Posted by Bruno

...
If you have overheated > 200 C after HT, then your blade is done for. Nothing will recover from that except doing HT all over. Did the blade discolor during polishing? If you saw colors on the steel, you did. If not, then you didn't.
...

Then it should be no problem fortunately.

What do you mean the spark test exactly? What I should see?

So many possible variables! Geometry, HT, steel, honing technique, decarb.....

Is there anything different about this blade to previous ones?

Is the edge chipping during honing or are you testing the edge in some way after honing?

Bruno hit what I was thinking as everything sounded like it was right...the time between the fire and the quench is very critical. To add to what Bruno mentioned about blade thickness, I always try to leave at least a penny width of thickness at the edge. I found out another hard way about not leavintg enough meat at the edge and have had multiple "potato chip" blades.