Warp speed, Scotty

[ytuyuty]

I hesitate to ask this question because I have no idea what steel I am using, but maybe it will generate some interesting discussion anyway.

I made a knife and it warped and twisted very badly in multiple planes during the hardening quench.

Here's the story: I inherited a table saw and a few dozen circular saw blades that are all from the 1960s. So I decided to make a round knife for leather working, using a circular saw blade as the steel. All went well until the hardening quench. It ended up warped, twisted and disfigured.

I made a new knife, but went very slowly with the cutting and grinding to be sure that the steel never got hot, so I wouldn't have to harden/temper.

So... How do you prevent warping during the hardening quench when your blade is 0.07 inches thick?

 

[Buzzkill]

Depending on the starting material you may be able to quench between 2 plates of aluminum using some clamps.  As thin as the material is that method may harden some steels where you would normally need oil. If you happen to have a couple flat aluminum plates it would be pretty easy to give it a shot. 

[Frosty]

You don't say how large the blade is but just the geometry of a thin round blade is problematical. The center of the blade is going to quench slower than the edges it's surrounded by 360 * of steel while the edges are on the outside of the curve and less than 50% has extra steel to slow the quench.

As the outside edges cool they shrink while the center cools much more slowly. Much more in molecular change speed, not necessarily our perception of slow fast. I wouldn't be surprised if it looked like a tortilla made of bacon.

I don't know how I'd go about quenching a thin disk, I'd have to read and experiment. Off the top of my dented cabesa I'd think maybe a high quantity stream of water/oil directed against the center but that is simply reversing the stresses of chill shrinkage.

Frosty The Lucky.

[ThomasPowers]

What did you quench it in?  Did you run any normalizations before heating or the quench?  Have you tried an edge quench?

[ytuyuty]

Thanks, I just read about edge quenching and plates, never heard about those tricks before.

 

[Michael Cochran]

7 hours ago, ThomasPowers said:

What did you quench it in?  Did you run any normalizations before heating or the quench?  Have you tried an edge quench?

How would you edge quench a circular blade?

[ThomasPowers]

Quenching with air you make a curved piece of pipe with a slot in it that connects to your compressor and provides a curved jet of air.  Similar can be done with oil and water and if using quenching goop---semi solid mix of oil and greases you could just mold it in the container to match the blade

Now these are for quenching leatherworking round knives which are in reality semicircular at the edge.  For a knife that was truly round like a quoit I might try just heating the edge and then quenching the entire piece or using an air hardening steel like A2 or borrowing an old round lawn waterer or ...