Gear's 190x

[ratitude]

Just want to say thank you for sharing this great info guys. I read lots and post little, the only casting experience I have to date is for pistol. A few posts back Rick mentioned that the quench temperature will have an effect on bhn. From what I know about metallurgy, I agree with him. You should see a difference if the water you drop the boolits into is 33 deg or 200 deg. You should also see a difference quenching with oil vs water. Someday I look forward to trying some of these experiments myself, until then I will gleefully continue reading. Thanks again!

[geargnasher]

50/50 automotive antifreeze and distilled or rainwater makes a really good quench medium and keeps the bullets from tarnishing for a long time. Downside is it seems to never dry.

Rick, I've been thinking on this phenom that Brad and I seem to be experiencing and it may have to do with the low freeze point of the tin. It seems like I just can't get very low-tin, low antimony alloy to harden past 20 bhn, and any bullet temp above about 400 doesn't make it any harder. Yes I'm aware of the time and oven type affecting this, and that may be why Brad and I both are seeing the platau of hardness above a certain quenching temperature. I use a conventional oven. It's easy to quench 97/2/1 alloy from the mould and get them all the same hardness as long as I'm shucking them out at or above the maximum effective hardening temperature, but if I add more tin I can get them a bit harder by quenching at a higher temperature. Using 97/2/1 makes for consistent final hardness when quenching from the mould if they aren't all exactly the same temp leaving the mould, but are at or above the temperature that gets them as hard as they'll get. Thus, if I use more than 1% tin, I just air cool the bullets and then oven heat-treat at the temperature I want because it's too difficult to keep the alloy "just right" when casting. I know that antimony is the principle hardener, but tin percentage seems to affect the temperature at which the heat treat hardness peaks out. Make sense? I'm not saying this is fact because I'm not 100% sure what my alloys contain and it's more of a casual observation at this point. I do suspect that there is probably not much arsenic in my wheel weight metal and I think I'm pretty close on the tin/antimony percentages, to half a percent or so based on specific gravity, slush point/liquidus point, and hardness achieved through various cooling rates.

Gear

[cbrick]

Back when I was doing all the testing I never heat treated an alloy with only 0.5% Sn so I can't answer your question from my own experience. I have, possibly had several papers written by the metals industry that discuss this very thing. I just now looked through the only one I've found so far and it only discussed Pb/Sb/As alloys and it didn't include Sn at all. This was the paper discussing 2% Sb as being too slow to age for industry purposes but with no Sn and 6%+ Sb the strengthening time curve was satisfactory. Logic tells me that in view of that that 0.5% Sn would have little to no effect. My own WW alloy XrF tested at 2% Sb & 2% Sn (I added 2% Sn prior to the testing) and I can and have many times readily reached 30 BHN with this alloy. If a 2% Sn alloy will do this and industry is doing it with no Sn what would be the effect of 0.5% Sn? Back to that logic thing I can't see it but . . . One of the papers discussed Sn at 5% and up as limiting the amount of strengthening that can be achieved and increasing age softening. Like 0.5% Sn I've never heat treated a 5% Sn alloy either. My own experience testing age softening was with 2% Sn and it took 10 years to go from 30 BHN to 26 BHN.

As a side note none of the WW XrF testing done through the site listed As at all, just didn't show up. My own suspicion is that at 0.25% it was too little for these tests and the machine discounted it.

I'll try and find some of the other papers tomorrow (I also have some notebooks that may contain some of this stuff) and see if any of them discuss the specific effect of Sn and Sn percentages on strengthening and aging. It's possible I don't have a bunch of it, much didn't make it to this computer when the laptop it was on started to act up, I lost over half of my photos & other things.

Rick

[35 shooter]

Yes, a low % tin gives a harder boolit when heat treated. My alloy has no tin, 6/2 ISO should be same Sb with tin added + Cu.

A member here tested the bhn on some straight ww boolits i heat treated @ 465* for one hour water dropped in cool tap water. Don't remember if it was lee or saeco tester he used but the boolits were no more than 2 weeks old and bhn was 27.
No tin was added so probably had low tin content. I always thought that was a little high no. for the bhn on straight ww ht, but after seeing poppers post about low tin content more heat treat effect on bhn it makes more sense now.

[btroj]

As a side note none of the WW XrF testing done through the site listed As at all, just didn't show up. My own suspicion is that at 0.25% it was too little for these tests and the machine discounted it


Rick, that is my biggest issue with XRF testing. I just don't think they are precise enough for some things. The guy at the scrap yard only needs to know a pretty rough estimate to decide what he is gonna pay you. Now if you had one specifically set up for a WW type alloy it might be better? If it wasn't so dang expensive I would consider having a wet lab analysis done but I'm not will to pay the hundreds it would cost.

Gear is exactly on point with what I am seeing. The really low tin seems to make the HT temp less critical.

I took a batch of 4 month old air cooled range scrap bullets out last night. Split them into 3 groups of about 50 each. One batch was heated for a full hour, in a preheated oven, to 340. One batch was heated for a full how to 420. One batch was left as is. The as is batch has reached 14 BHn after 4 months of aging. Right after the quench the others measured 9 and 9.5. Will be testing daily for a week or more to see what happens with time.

[cbrick]

A member here tested the bhn on some straight ww boolits i heat treated @ 465* for one hour water dropped in cool tap water. Don't remember if it was lee or saeco tester he used but the boolits were no more than 2 weeks old and bhn was 27.
No tin was added so probably had low tin content. I always thought that was a little high no. for the bhn on straight ww ht, but after seeing poppers post about low tin content more heat treat effect on bhn it makes more sense now.

35 shooter offered a good clue, he heat treated straight WW and in 2 weeks they tested 27 BHN. He added no tin so should have been close to 0.5% Sn.

Rick

[geargnasher]

Gear is exactly on point with what I am seeing. The really low tin seems to make the HT temp less critical.

I took a batch of 4 month old air cooled range scrap bullets out last night. Split them into 3 groups of about 50 each. One batch was heated for a full hour, in a preheated oven, to 340. One batch was heated for a full how to 420. One batch was left as is. The as is batch has reached 14 BHn after 4 months of aging. Right after the quench the others measured 9 and 9.5. Will be testing daily for a week or more to see what happens with time.

Excellent, I await the reports. My optimum mould temperature for aluminum when water-quenching from the mould is somewhere around 400-420. No telling what the bullet temperature is.

Gear

[popper]

Interesting reslts today with the 30/30. I usually PC then size. Tried the same boolit (150 PB), same load, 17 gr 2400 + dacron. These were sized then PC HTd ~ a week ago. A few wouldn't chamber - resized the case! Boolits were 0.312-313. Nothing spectacular for groups - but better - several had the funky lumpy PC on the base (DT). Target holes were smaller than the same alloy in the BO (145 PB) @ ~ same fps. I recommend H.T. after sizing! Assuming the Isocore is 96/3/1/? I get 97/2/0.5/0.2. It is harder than my 96/3/0/1 alloy I use in the 308, full case of 335. Both are quenched from 400F to ~ 50F H2O, one hr cooking, cold oven to 400F. Not much but alloy & air to heat in the oven, IIRC ~ 10 min to get probe to 400F empty.

[btroj]

I measured this morning and just now when I got home from work. I realize it is WAY too early to draw conclusions but right now it seems the 420 group is much harder than the 340 group.

Dammit I hate to say this but- Rick may well be right.

Gear, could your results from the mould be due to the fact heat treat I allows the metal crystals to change in size while yours are a mass of whatever fresh from the mould? I am not a metallurgist by any stretch, just a supposition.

[cbrick]

I measured this morning and just now when I got home from work. I realize it is WAY too early to draw conclusions but right now it seems the 420 group is much harder than the 340 group.

Dammit I hate to say this but- Rick may well be right.

I'm crushed, just devastated, I shall never be the same again. You doubted me?

Not that I've never done this before but for several years half my electric bill was from the lead pot and convection oven. When I wasn't doing that I was studying what the metals industry had to say about it, I didn't make this stuff up, I didn't invent it. I studied how & why and did it for myself. Hundreds of times with very repeatable results.

Saturday evening will tell the story. Here's another test I did you may find interesting. I depleted (reduced, not eliminated) antimony in a pot of WW alloy. I did my normal HT on the bullets from that pot and the bullets turned out near the same BHN as those from the normal alloy with but one difference. The normal alloy would be near peak hardness in three days, the depleted alloy reached almost the same BHN, finally, it took three weeks.

The BHN of your bullets should reach near peak hardness in 3 days assuming 2%+ Sb after that time they may continue to harden slightly for a little while. Less than 2% Sb and your looking at more time to harden.

Rick

[cbrick]

Gear, could your results from the mould be due to the fact heat treat I allows the metal crystals to change in size while yours are a mass of whatever fresh from the mould? I am not a metallurgist by any stretch, just a supposition.

Time my pill counting friend, time!

Quenching from the mold most certainly does harden the bullets but when you ask yourself why the best you can get is 18-20 BHN just think time. When quenching from the mold how long are the bullets at that temp before hitting the water? Think of your half hour heat treating results and your current one hour results.

Rick

[popper]

Cbrick - JOURNAL OF THE ELECTROCHEMICAL SOCIETY January 1953

"The results obtained appear to lead to the conclusion
that a homogeneous alloy of uniform solid solution cannot
be produced by any present casting process unless further
heat treatment is employed. Slow cooling would appear to
hinder rather than help the attainment of homogeneity in the solid solution."

The secret to a good cast boolit. Maybe better testing equip. but no change to metallurgy.

If you consider the lattice of materials to be a crystal, then you are correct and the term is often used that way.
Considering a 1000 # chunk of Pb as a crystal is kind of out of my realm of understanding.
A 'good' boolit alloy will have many small 'crystals' of SbSn or whatever with many small dendrite structures.
Large 'crystals' will cause the alloy to be brittle and/or weak
I think Badgeredd's approach to a 'balance' alloy Sb=Sn is to tie up all into SbSn molecule so no individual is present. Normal 'freezing' of alloy bounces back and forth between liquid & solid, causing layers of different alloy composition to form. Felix stated that alloy @ 200F then AC is soft. Validated!
Yes, the closer you get to 'slump' temp & then rapidly cool, higher BHN - more homogeneous alloy.
Now to go study the softening when the base is hit with a hammer (high pressure).
More fun.

[btroj]

I was going to do more casting tomorrow but OT came and cut that out. I can use the money but prefer the time off.

Rick, I didn't doubt you per se but rather wondered of alloy content made a difference in end result. This is less tin than many of your tests so it needed doing?

[cbrick]

Rick, I didn't doubt you per se but rather wondered of alloy content made a difference in end result. This is less tin than many of your tests so it needed doing?

I've tried to explain to you that with what your doing with the heat treat Sn isn't an issue. I tried telling you that because at your percentage of Sn it simply isn't particularly significant. Increase your Sn significantly and it will be.

Rick

[btroj]

That is the next test, to see how Sn content makes a difference. I will increase the Sn in a batch to around 1% while keeping Sb the same and repeat the test.
I expect to see the top end hardness decrease with increased Sn.

[cbrick]

Considering a 1000 # chunk of Pb as a crystal is kind of out of my realm of understanding.

Yeah, me too.

I think Badgeredd's approach to a 'balance' alloy Sb=Sn

Yep, I've been telling people that use Sn that very thing for longer than there has been a CastBoolits.

is to tie up all into SbSn molecule so no individual is present.

A Sb/Sn molecule? Uh, no!

Normal 'freezing' of alloy bounces back and forth between liquid & solid, causing layers of different alloy composition to form.

Uh, ok, if you say so.

Rick

[cbrick]

That is the next test, to see how Sn content makes a difference. I will increase the Sn in a batch to around 1% while keeping Sb the same and repeat the test.
I expect to see the top end hardness decrease with increased Sn.

Ok, I give up.

Rick

[btroj]

Ok, I give up.

Rick

No, don't give up.


You said Sn isn't an issue at real low levels. If I raise it to 1% it would become an issue, would it not? Does it not affect both final hardness and probably the time to final peak hardness?

I may be dense with this but I do eventually get it. This is why I do my own testing and see what happens over time. I'm kind of a visual learner I suppose.

NO giving up.

[cbrick]

No, don't give up.

You said Sn isn't an issue at real low levels. If I raise it to 1% it would become an issue, would it not? Does it not affect both final hardness and probably the time to final peak hardness?

Brad, in how many posts in this thread alone have I said that at these percentages Sn will not do what your saying. How many times have I said 5% and up? How many times have I already posted my results using 2%?

Go ahead and play with your 1% and see what happens.

Rick

[btroj]

Ok, so I don't have enough tin to matter. I sure won't be using 5 % Sn with 2 % Sb.

I will say I didn't ever think of soak time as being beneficial as it pertains to time for dpcrystal growth/change. I was thinking only in terms of getting the bullets to temp. That little tidbit alone was educational, very educational.