HT questions - equalize?

[HSC ///]

what does it mean to "equalize" in a HT process?
ex - "Preheat: Heat to 1400°F (760°C) Equalize."
This is for SS

also when the quench is a plate quench and the required min clamp pressure is 4 bar, isn't this alot of pressure applied to the plates? 4 bar = 58 PSI

lastly I see some makers use double SS foil...why do you need to double the foil?


thx

 

[samuraistuart]

What I take that to mean is that some parts (not necessarily a knife blade) have complex cross sections, mass larger in some areas vs others, and that the piece needs to be held at that specified temp in order to ensure that the entire piece has reached the desired temp. How long that takes I suppose is dependent upon the piece in question.

I'll defer the 2nd and 3rd questions to more experienced. I always thought that "4 bar" referred to pressurized air being sprayed between the plates to help the piece quench faster, but I admit that I am totally just guessing, and could be totally wrong. I have heard of people saying you need to use C clamps and all sorts of other methods to clamp down on quench plates. I never understood the physics as to why putting a lot of pressure on the plates is going to offer a better quench (or a straighter blade), than simply good contact being made on both sides with decent pressure (like hold your hand down on the top plate is all that's needed).

 

[Stacy E. Apelt - Bladesmith]

1) Stuart has that covered - heated evenly through the piece.

2) You may be reading a HT chart wrong. In industry, steel is often quenched in moving air, which is usually specified as 4 Bar pressure or such. The wording may read,"quench in plates or 4 Bar air ."
50PSI clamp pressure isn't that much pressure. Once the clamp pressure is dispersed over the whole plate, it is only a few PSI. Think about it. People stand on things to clamp them while doing things like plate quenches or gluing. That is about 150-200 pound clamping pressure. A strong person can squeeze 100PSI with his hand. An old guy like me can squeeze 5-7- pPSI.

3) Most folks don't usually double the foil, but they almost always double the fold. Fold a 1" wide border, use a rubber hammer to pound it flat and tight, then folf=d agai at 1/2" and repeat the pounding tight. Don't pound anything but the folds.

 

[HSC ///]

1

2) You may be reading a HT chart wrong. In industry, steel is often quenched in moving air, which is usually specified as 4 Bar pressure or such. The wording may read,"quench in plates or 4 Bar air ."
.

thank you
the wording form the Crucible CPM 154 sheet read -
"Quench: Oil or positive pressure (4 bar minimum) to below 125°F (50°C"

 

[Stacy E. Apelt - Bladesmith]

That is what I thought you might have read. If using contact plates, just have some way to clamp them down snug on the blade. It doesn't take a lot of pressure.