Keeping O1 flat after quench and before tempering

[Deering Knives]

How do you keep your blades flat after the quench? I use to flat pieces of steel.

 

[samuraistuart]

Here is what jumps out at me. I don't know the Mf of O1, but I think it is around a hundred degrees or so. It may be 0F or it may be 200F, maybe someone who does know can chime in. The point being, the blades need to cool all the way to the Mf temperature in order for full martensite conversion. If the Mf of O1 is closer to 100 degrees F, or worse even 0F, you're not getting full martensite by keeping the blades "warm" before tempering.

There is absolutely no need to worry about stress cracks as long as you aren't waiting until the next day to start tempering (or you quenched in water!). Then I might be concerned with stress cracks. Go to tempering once the blade has cooled down to room temp. As far as keeping things straight, for me it is SUPER easy to put on thick gloves and do any straightening right after the quench, before the steel has fallen below 400F or whatever it is. It is very easy to correct bends and bows with gloved hands during that minute or so. If I can't catch the bend during cooling, the three point clamping system during tempering works very well too.

Bottom line...I wouldn't "keep the blades warm". Let them cool down to room temp.

 

[Fiddleback]

I've never heard of this. After quench we cool to room temp between plates of aluminum. That prevents warp. I would never sit a warm blade on any surface. I had warping troubles due to this when I was starting out. Temper twice at 425.

01 is one of the most forgiving steels. I have never had a stress crack in 01 and don't expect to see one. You might be spinning your wheels with the keeping it warm deal.

 

[Deering Knives]

geez, I am getting mixed information. I used to do kinda what you are talking about fiddleback... sounds like I'm switching back..

 

[Stacy E. Apelt - Bladesmith]

I will tell you what you should do, metallurgically. What others do or you read/saw on the internet I don't know about:

ALL steels need to reach Mf before temper. On most simple carbon steels ( 1084, 1095) that is somewhere between 130F and 200F. On steels with alloying (52100, 5160, O-1, A-2, etc.) it can be between 0F and 70F. On high alloy steels and stainless steel, it needs to be at or below -100F. After cooling to room temperature, all non- stainless/high alloy steels should be cooled in cold tap water at a minimum.

Stress cracks form in steels that had high stress quenches and have sat for many hours or longer at room temp. If tempering within 3-4 hours, it isn't an issue. Cooling the steel to room temp will not cause cracks.

Tempering while still warm on a steel like O-1 will lead to retained austenite. Some of that will be reversed in the tempers, but there will likely be some that gets stabilized and will never go away. The final hardness will be lower than if properly done.