Heat Treatment of D-7

[joe sangster]

I have a customer who has a knive blank of D-7 & wants it handled ,ground & heat treated. Can anyone tell me how to heat treat D-7 ? I have only heat treated ATS-34 & 440C. Your help would be greatly appreciated !

Joe

[AcridSaint]

Taken from Engnath.com:

D-2, D-7 steel Preheat at 1500 F. Harden from 1850 to 1875 F. Draw immediately.

[joe sangster]

Thanks, AcridSaint ! What Rc should that give me ?

Joe

[Don Robinson]

Joe, what Cap says sounds about right to me, but why don't you google Crucible metals and you might find a data sheet?

[AcridSaint]

I'm not sure about the RC, but as Don says, you should be able to get a datasheet from Crucible's website. Bob's site is just the first place I go when I want to get a HT method that's easy to understand. It's a little dated, but most of the popular steels and a few obscure ones are listed.

[joe sangster]

I could not find a data sheet for D7 but did find Crucible's sheet for D2. It states "preheat to 1100 -1200 . equalize, then to 1400-1450 , equalize , then austinitize at 1825-1875 X 30-45min " I don't understand what they mean by "equalize". How do I do that ? Joe

[Don Robinson]

Originally Posted by joe sangster

I could not find a data sheet for D7 but did find Crucible's sheet for D2. It states "preheat to 1100 -1200 . equalize, then to 1400-1450 , equalize , then austinitize at 1825-1875 X 30-45min " I don't understand what they mean by "equalize". How do I do that ? Joe

To equalize the heated metal, it's held at the same temp. until the metal is heated all the way thru to the same temp. as the chamber.

Some of the methodology in heat treating information goes back to the days when we didn't have accurate digital controllers. The furnace door had a glass window in it so you could see the interior of the chamber. You'd raise the temperature, then watch thru the window until the steel reached the same color as the chamber itself. Equalized.

Using a modern electric furnace I equalize 5 to 10 minutes at the temperature, then progress to the austenitizing temp.

An old myth about heat treating steel says that the interior of a piece of steel in a furnace is cooler than the exterior. That's not true. Steel heats up at the same rate inside and outside. At least the knives we're talking about.

Joe, I haven't heard of D7 steel. Are you sure it's not "S7"? S7 is a shock resistant steel people used to use before the powdered metals came along. Good for shock in a sword maybe, but not much edge holding ability.

[shgeo]

If D2 and D7 heat treat similarly, you should soak for al least 30 minutes at 1875?F and longer for lower temperatures. Not giving the full soak time will result in incomplete carbide solution and give you an inferior blade.

[joe sangster]

I have never heard of D7 either but the man says it is D7. He says it is very similar to D2 but with a higher vanadium content. He is an old machinist & seems to know what he is talking about but what do I know ! I certainly have no expertice along these lines & have advised him of this . He says he has a sample piece that i can work with so I may try heat treating as D2 & see what I get, Joe

[AcridSaint]

I've heard of D7 before, although I've never actually seen it. I know I sound like a broken record here, but I'll post another tidbit from Engnath:

"D-4 and D-7 are also good cutlery alloys, but darn hard to find in the right sizes. Air hardening steels can work harden while you're grinding them if you get the stock too hot. This doesn't mean much on the grinder, but when you try to file a guard notch, the file will just slide."

That came out of his steels section on D2.

[joe sangster]

Thanks , Cap!

[Carcar?_BR]

Hello People. When I read Joe?s topic I remembered something about and tryed to find in Wayne Goddard book, something about D7.
I made a mistake about the steels with D6, but the contents of D7 is this :
C: 2,35 Cr: 12,00 Mo:1,0 V:4,00