Oven Heat treating - 1st attempt...IT WORKED!

[BigDaddie]

Hi All,

I gave oven heat treating a crack yesterday. The 5 30cal rifle boolits started off at BHN of 14 as cast. I then put them in the oven on a tray at 460degF for 1 hour and quenched them in chilled H20. I had already filled a flat on them before the heat treat. The alloy is antimonied lead close to Lyman #2. I threw in some shot as I read that the arsenic helps with heat treating.

I tested them tonight on my Lee hardness tester (24hrs later) and they came in at 27BHN. They were all the same measurement.

I was quite surprised that they were that hard!

The question is: How does one control the amount of hardening from the base alloy? Is it just a matter of heat treating for 30mins instead of an hour? Also, if the boolits are gas checked, does that pose any issue?

[blaser.306]

I had a post similar to this about a month ago , I also added a small amount of shot to the melt to increase "hardness" whitch it did . However it would appear that you only need antimony to increase the hardening effect and the arsenic only causes your boolits to become so hard that they are brittle . That is my experience anyway !

[Matt_G]

The question is: How does one control the amount of hardening from the base alloy? Is it just a matter of heat treating for 30mins instead of an hour? Also, if the boolits are gas checked, does that pose any issue?

To answer the last question first, I personally have never had any issue heat treating gas checked boolits.

Re controlling the amount of heat treat:
Time and temp are the two variables you can control.
Shorter time, less hardening. Same thing with lower temp.
There is a great article on heat treating lead alloys in the NRA publication "Cast Bullets". I believe it is out of print, but if you keep your eyes open you may be able to find a copy.

A low temp like 425 F for only a half an hour will yield a boolit less hard than one heat treated at 460 F for an hour.

BTW, he states there is no advantage to using ice water over room temp water.
Never tested that myself...

[badgeredd]

To answer the last question first, I personally have never had any issue heat treating gas checked boolits.

Re controlling the amount of heat treat:
Time and temp are the two variables you can control.
Shorter time, less hardening. Same thing with lower temp.
There is a great article on heat treating lead alloys in the NRA publication "Cast Bullets". I believe it is out of print, but if you keep your eyes open you may be able to find a copy.

A low temp like 425 F for only a half an hour will yield a boolit less hard than one heat treated at 460 F for an hour.

BTW, he states there is no advantage to using ice water over room temp water.
Never tested that myself...

OK...I have to ask. Has anyone compared the consistency and degree of hardness between water quenched from the mold to oven treating? Is it more consistent oven heat treating? Just curious if it is worth the added effort. Curious minds have to know

Edd

[Matt_G]

Dennis talks about this is that article I mentioned.
Water quenching from a "cool" mould made no difference in hardness. They were the same hardness as air cooled. By cool he meant 300 F mould temp or less.
(He rigged a thermocouple to measure the temp of the mould.)

However, once the mould started dropping frosted boolits (mould temp of 430 F) the hardness attained by water quenching was on par with oven heat treating.

So as long as you keep the mould hot, water quenching from the mould will yield close to the same results as heat treating in the oven.

The only advantage I see to oven heat treating is that you can harden the boolit after sizing and gas checking if applicable.
Lead work softens so if the water dropped boolit has to be sized, there will some softening of the boolit.
In that article, Dennis suggested that if the boolit doesn't need to be sized, water drop.
If it does need sizing, heat treat in the oven. (After sizing of course)

HTH

[badgeredd]

Matt G,

Thanks for the answer. I had wondered if there was a particular advantage to oven treating over just water dropping. You've answered that question completely.

Edd

[waksupi]

I did test various temperatures in an oven for hardness variations. I found I could get most any hardness I wanted, by varying the temperature by 20 or so degrees up or down. I'll see if I can find the chart I did on it, seems like I heated from around 350, up to 460.

[AJ Peacock]

Here is a great article that should shed some light on the subject.

http://www.lasc.us/HeatTreat.htm


AJ

[BrianB]

I think you'll find that the temperature of the water will have some effect on the hardness. Colder water will more than likely yield harder bullets. I don't have the equipment to test this, but it would be great to hear from someone who does.

[felix]

Brian, for really large boolits, the cold water temp will help get the center harder, but most folks do not want the center harder on larger boolits for better mushrooming. Best to use room temp water for all applications. Little boolits cool too fast from the mold before they hit the water, and they won't get as hard no matter the water temp. ... felix

[Pat I.]

OK...I have to ask. Has anyone compared the consistency and degree of hardness between water quenched from the mold to oven treating? Is it more consistent oven heat treating? Just curious if it is worth the added effort. Curious minds have to know

Edd

My experience has shown that oven treated bullets will be a lot harder and more consistant than bullets quenched from the mould.

[Gohon]

The chart that AJ posted is the guide I use for oven heat treating. Straight wheel weights heated at 420 degrees for one hour then quenched gives me a consistent 18-19 BHN which is what I use. I've never been a fan of really hard casts and always try to stay in the 16-19 BHN range for all my casts.

[BrianB]

Brian, for really large boolits, the cold water temp will help get the center harder, but most folks do not want the center harder on larger boolits for better mushrooming. Best to use room temp water for all applications. Little boolits cool too fast from the mold before they hit the water, and they won't get as hard no matter the water temp. ... felix

I figured it would. I remember my first attempt in heat treating steel many years ago. I dropped near-red hot steel in a bucket of water in January (The water was ice cold). I could clearly see the stress fractures when I pulled it out so I dropped it on my anvil to see what would happen...snapped like a piece of glass.

[BigDaddie]

Thanks fellas!

I'd like to shoot these boolits in the 308 at around 2000fps using Varget. Hence why I wanted them harder than 14BHN.

That article answers all my questions

[badgeredd]

My experience has shown that oven treated bullets will be a lot harder and more consistent than bullets quenched from the mould.

Thanks Pat. I've read several articles on heat treating, but have never seen anyone say whether oven treating was more consistent. It would seem logical that if the oven treated boolits were brought up together at the same temp and quenched from that temperature, they'd be more consistent in hardness or toughness. But what is logical in my mind may not be correct or logical in fact.

Edd

[Marlin Hunter]

Lead work softens so if the water dropped boolit has to be sized, there will some softening of the boolit.
In that article, Dennis suggested that if the boolit doesn't need to be sized, water drop.
If it does need sizing, heat treat in the oven. (After sizing of course)

HTH

Does it work harden completely through the bullet or only on the surface?

[felix]

Dependent on the diameter size of the boolit, like was stated above. Sizing will affect surface only, unless movement goes throughout. ... felix

[mrbill2]

Lyman 311284 bullet cast from 100% wheelweights air cooled sized to .309 with lube and sized. How deep below the surface does this bullet soften after being sized and how does one determine the depth and bhn.? Does it matter?
Mr. Bill2

[Matt_G]

Does it work harden completely through the bullet or only on the surface?

Dependent on the diameter size of the boolit, like was stated above. Sizing will affect surface only, unless movement goes throughout. ... felix

The way I understand what Mr. Marshall was saying in that article is that it depends on the amount of sizing required.

If you're only sizing a thou or 2 it will mostly just work soften the surface. That softened layer is only a few thou thick.

However, if for some reason you were sizing down a lot, that lead has to go somewhere. It will elongate the boolit; therefore, it could potentially soften the entire boolit.

He had a special Lee mould that cast 30 cal boolits several sizes oversize that he used to test this.
For instance he sized a boolit which dropped at .315 in a .310 die. After springback the boolit measure .311. But that sizing of .004 elongated the boolit .006 inches.
When testing the hardness with a small Knoop hardness tester it was shown that the elongation caused hard grains to slide by one another. The metal that deformed due to this sliding action work softened, and rendered the boolit no better than an air cooled boolit, in fact it may have been even softer.
That is why he suggests oven heat treating for any boolit that can't be used as dropped and must be sized.