O1 – Furnace types and quenching ????help

[C_Claycomb]

I have started to file my first blades from O1 tool steel. I have been looking ahead to how I am going to get them heat treated.

The place I work has both an atmosphere furnace and a vacuum furnace, and the guys who run them don’t object to my running some blades through them. Question is, which to use, and how should I set things up.

The vacuum furnace gets heated up from cold, so that will provide a pre-heat, the atmosphere furnace though is on all the time at a minimum of about 1380degF (bit high??). On the other hand the atmosphere furnace uses a hot oil quench (about 175degF) whereas the vacuum unit uses gas (I’m not too clear on this, been told that it can achieve different quench rates).

In the case of oil quench I have read that the blades have to go into the oil vertically, point first, to prevent warping. How badly can a blade warp if quenched length-ways, edge first? The furnace runs with a conveyor belt, stuff goes in on a rack and gets heated and quenched in whatever orientation it gets put in with. Do I need to wrap the blades?

I can go and ask questions in the heat treat area, but I am so new to this that I still don’t know what the right questions are

)

I don’t live in the US, if I did I would be sending my first blades to someone who knows exactly what they are doing. Round here though, knife makers are even rarer than legal gun owners!

Hope that some of you guys can help me out.

Thanks

Chris



[This message has been edited by C_Claycomb (edited 01-12-2001).]

 

[AchimW]

I looked it up in my "Stahlschlüssel"-book.

Hardening temperature for O-1 is between 1460° and 1500° F. Quenching should be done in warm oil. Heat slowly to the hardening temperature and quench immediately, as any holding time at this temperature will produce grain growth. If the blade is quenched edgewise and this is done perfectly straight, there shouldn't be any warpage problems. The vacuum oven has the advantage that there will be no scale on the blade after the hardening, but air or gas cooling is not recommended for O-1 as you can't reach the necessary cooling rates to get it hard enough.

Tempering after hardening should be done for 2 hours in an oven (kitchen oven) and will produce the following hardness results if properly hardened:

Temperature: Hardness HRc:

as quenched 64
212° F 63
392° F 60
437° F 58
482° F 57
572° F 56

I would go for about 390° F with small knives and about 450° to 500° F for big knives like Bowies.

Achim