Heat treating 17-4

[mr fixit]

What is the atmospheric requirements for heat treating 17-4? What condition does it need to be for a blast baffle for 5.56?
H900? H1100? which is better/best?

[Rich V]

Heat treatment is done in air. It's a low temp (900 - 1150 F) so no scale is formed.

I use H900 as it is the hardest grade. Heat for 1 hour at 900F then air cool and you're done.

[mr fixit]

Does it have to be in air?

May sound crazy......

I don't have a kiln, or access to one. I do have a way to melt aluminum (roughly 1000-1100*F). I was wondering about melting the Al, and dropping a blast baffle in for an hour, then taking it out to air cool. I have found 17-4 annealed is why I ask.

[Rich V]

The temperature needs to be controlled tightly if you want the H900 temper. I don't think you can get anywhere near the control needed by using a molten metal bath.

I use a small pottery kiln that has digital temp control. Look around to see if you can get access to a small kiln locally. The other alternative is buy some 17-4 in the H900 temper and machine your baffle from it directly. It will be a bit tougher to machine but it will cut just fine with carbide tooling.

[ChimeraPrecision]

Keep in mind 17-4 shrinks (at a very predictable rate) when heat treated. Compensate by cutting your parts oversive by the calculated amount.

I heat treated some 17-4 the other day and got 43Rc in the H900 condition. Which is rather hard.

I absolutely love 17-4, plus it's magnetic so you can grind it with a mag chuck easily.

[0101silent]

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[delta9mda]

Ask samson104. He just finished a 556 can from all 17-4 the heat treated when completed.

[Dlob]

You have to start with solution treated metal too (condition A). Taking any old 17-4 and then heating it for an hour at 900 doesn't get you there.

Also (trying to dig up memories from a job 4 years ago) - you can heat treat at 900, or about 1025 and above (higher = softer), but from 950-1000 bad things happen...can't recall what though. Something corrosion related if I recall.

You'd likely want the hardest condition for this use, shoot for 900.

[T-Rex]

If you turn/cut it in the hardened condition, does it need to be treated, again, afterwards?

[Rich V]

If you turn/cut it in the hardened condition, does it need to be treated, again, afterwards?

No need to heat treat after machining.

[T-Rex]

No need to heat treat after machining.

So, since it is easier to machine, in hardened state, there should be no reason to go through the hassle of heat treating, at all. Provided you're able to obtain it in that condition.

I used it as the blast baffle, on my 22 build. It is much nicer to turn than 316. I was able to use HSS inserts on the 17-4.

[Rich V]

No need to heat treat after machining.

So, since it is easier to machine, in hardened state, there should be no reason to go through the hassle of heat treating, at all. Provided you're able to obtain it in that condition.

I used it as the blast baffle, on my 22 build. It is much nicer to turn than 316. I was able to use HSS inserts on the 17-4.

Assuming you have a decent lathe it should machine fine.

I sent you a PM

[Pdave]

Anybody have a source for small quantities of H900? Speedy metals and online metals sell it in the (A) state.

[Dlob]

McMaster has it in the H1150-M (Rockwell C 33) and what appears to be H1000 (C40) on their precision ground round rod material.

Other places to try - Grainger, or any local supplier?

[T-Rex]

McMaster is a bit pricey.
Plenty of eBay sellers have small quantities.

Local sellers was a good tip. Machine shops, too.

[Samson104]

I have made a couple cans with it both in annealed and hardened.
while in the H900 state it is its hardest I honesty don't think its cost and hassle is worth it over 316 or even 304 SS , maybe if you are trying to make as light a can as possible not using titanium or plan on abusing the s--t out it with magdumps from full auto.
I won't bother with it any more except for a blast baffle or a brake.

BUT a small pottery kiln is the ticket fo heat treating.
Put the metal in , bring temp to 900 start timer , at an hr and a half turn it off and leave it till tomorrow.

[mr fixit]

I have made a couple cans with it both in annealed and hardened.
while in the H900 state it is its hardest I honesty don't think its cost and hassle is worth it over 316 or even 304 SS , maybe if you are trying to make as light a can as possible not using titanium or plan on abusing the s--t out it with magdumps from full auto.
I won't bother with it any more except for a blast baffle or a brake.

BUT a small pottery kiln is the ticket fo heat treating.
Put the metal in , bring temp to 900 start timer , at an hr and a half turn it off and leave it till tomorrow.

So having a SS muzzle brake as a sacrificial baffle should negate the need for it in front of cones?

[Samson104]

So having a SS muzzle brake as a sacrificial baffle should negate the need for it in front of cones?

The brake will take the brunt of the abuse off the first baffle but if you intenbd of realy getting the can of or on a real short barrel then have a hard first baffle wouldn't hurt

[Samson104]

I'm planning my next 308 can to be 100% titanium but will have an internal brake made from17-4.
Basically like a brake mount can but the brake will be permanent inside the can so it'll work on an 5/8x24 threaded barrel

[pyrofx]

Delta and I are in the plan stage of the ultimate blackout can now. All Ti, except maybe 17-4 expansion/blast baf/end cap. .
Bet our design comes out close .