quenching: softest alloy and still effective

[Guesser]

I've quenched WW from the mold and heat treated and quenched. With WW material becoming harder to find and/or more expensive I'm starting to alloy 50/50 with PB, as this works for most of my shooting. What I'm curious about is what percentage if PB does quenching or heat treating stop the increase in BHN factor.

[357maximum]

I have personally taken it all the way down to 15% ww....It still gets you somewhere(not very far), but there is some weird JUMP between 20 and 25% when waterdropping...So I suggest not going below 25% ww to the pure. I have seen very little (inconsequential) change in accuracy between the 25% and 50% ww mixes...so I use the softest mix I can accurately get away with, because most of my boolits are destined for a deerlike critter. These mixes allow you to use them without any fancy HPing, or complicated 2part casting tequniques...if you want a softer nose you still have the option of annealing the noses in a shallow pan of water also.

[243winxb]

My guess it never stops because of Hall-Petch strengthening . http://en.wikipedia.org/wiki/Grain_boundary_strengtheningJust less BHN. Up to 900fps just 2% antimony works fine, this is 50/50 WW & pure. Higher velocity requires 2% tin with more antimony. IMO. Look at example at bottom of page. http://www.freepatentsonline.com/5464487.html

[imashooter2]

I've found significant improvement water dropping range scrap which is very soft air cooled...

[stubshaft]

I water drop boolits that are 25 - 1 and have a BHN of 9.5 (when air cooled). They measure 21 BHN after water dropping.

[Guesser]

Good information and thanks to all.
Next question: when we water drop or heat treat, is this a thorough condition or is it only a "hard surfacing" damaged or removed during sizing/lubing?

[BABore]

It depends on boolit diameter. Water dropping can lead to the skin hardening affect due to the mold temp being just above the critical hardening temp of around 400-425 F. Because the boolit is just barely hot enough, the core can drop below the critical point before the rapid quench reaches it. With OHTing, you can run the boolits up a bit hotter and get progressively deeper hardening. I would'nt worry on boolits 30 cal or smaller. In fact, I don't worry at all on bigger boolits. A softer core and hard skin make for a perfect hunting boolit. 458 Caliber boolits, cast from 50/50 WW-Pb and WD'd, make the perfect hunting boolit. Hard enough on the outside to survive full velocity, yet they expand and retain their mushroom. IMO, there are many benefits to have this situation for HV cast. The boolit cross-section is tougher, gives a little, and has better springback than a rock hard boolit. I've found that I can get another 200-400 fps out of 22 bhn 50/50 over 28 bhn straight WW's. Also less antimony to leave a wash in the bbl.

[243winxb]

From my link above, patent >
After 8 days, 1 1/2 months and 2 months, hardness tests were again performed on these samples and these tests revealed that the hardness was essentially unchanged.

At least 25 of the samples which were heated for 5 and/or 10 minutes and then quenched as described above also were sectioned, ground, polished and hardness tested both at the surface and the core. These tests revealed that the hardness was essentially uniform throughout. The outer surface becomes softer if run thru a sizing die, inside the bullets is still hard. On Lymans website FAQ.

[runfiverun]

even if you do damage the sides of the w-dropped boolit some in sizing you still have the benefit of a nose strong enough to resist slumping in h/v applications.
thats why it is recommended to size the same day as casting w-dropped boolits so if you do mash them some they will still harden over the cure time.
plus they are sooo much easier to size before they harden up.

[snaggdit]

I didn't follow the link when you first posted it, but went and read it now. Interesting that the hardening is uniform throughout on oven heat treating. I wonder if water dropping does as well? Another thing I found interesting is that in the reading they talk about pure lead or lead with antimony a lot but in the metallurgical analysis they list the following:

metal wt. %
______________________________________

Copper 0.038
Arsenic 0.16
Antimony 3.0
Tin 0.25
Zinc 0.0001
Cadmium 0.0001
Nickel <.0001
Bismuth 0.018
Silver 0.0038
Tellurium 0.0015
Sulfur 0.0005
Iron <.0001
Lead Balance

It's those traces of copper and arsenic that actually affect the grain boundries allowing for heat treating.

[243winxb]

It's those traces of copper and arsenic that actually affect the grain boundries allowing for heat treating. http://www.keytometals.com/Article88.htm
Solution Treating and Aging
The alloy containing 2% Sb clearly does not respond sufficiently to be considered as a possible alternative.The 4% Sb alloy, however, attains a hardness of 18 HV after 30 min, and the alloys that contain 6, 8, and 10% Sb could be handled almost immediately

Adding sufficient quantities of antimony to produce hypoeutectic lead-antimony alloys can attain useful strengthening of lead. Small amounts of arsenic have particularly strong effects on the age-hardening response of such alloys, and solution treating and rapid quenching prior to aging enhance these effects.

Hardness Stability. For most of the two-year period, the solution-treated specimens were harder than the quench-east specimens. Other investigations have also shown that alloys cooled slowly after casting are always softer than quenched alloys. The alloys with 2 and 4% Sb harden comparatively slowly, and the alloy containing 6% Sb appears to undergo optimum hardening.

Application. Because of the detrimental effect of antimony on charge retention, the effort to reduce antimony contents of the positive plates in lead-acid storage batteries has led to the trend of replacing eutectic alloys with a Pb-6Sb-0.15As alloy. Battery grids made of this arsenical alloy will age harden slowly after casting and air-cooling. However, storing grids for several days constitutes unproductive use of floor space and results in undesirable interruptions in manufacturing sequences.

Although large-scale solution treatment of battery grids might be difficult to justify economically or to achieve without some distortion, quenching of grids cast from arsenical lead-antimony alloys offers an attractive alternative method of effecting improvements in strength. The suitability of quenched grids can be assessed by comparing with the hardness level that battery grids require in order to withstand industrial handling (about 18 HV, the hardness of the eutectic alloy). The alloy containing 2% Sb clearly does not respond sufficiently to be considered as a possible alternative.The 4% Sb alloy, however, attains a hardness of 18 HV after 30 min, and the alloys that contain 6, 8, and 10% Sb could be handled almost immediately.

[snaggdit]

Well, I had always been lead to believe that heat treating (or quenching) lead and alloys such as Lino without arsenic would not harden over air cooling. It seems that there can be some hardening even without the presence of an elemet such as thallium, bismuth, tin, cadmium, antimony, lithium, arsenic, calcium, zinc, copper and barium but that increasing amounts of tin/antimony lend hardness mainly based on composition not so much additional gain by heat treating (albiet a small amount). Also, this article seems to hold up the tendency of heat treating to slowly relax over time as has been mentioned before. I think (and it is only my humble opinion) that for our limited facilities, hardening pure by including at least 25% WW (with the included arsenic) offers the easiest way to effectively get increased hardness due to heat treating/quenching. I am enjoying the discoveries, though!

[Guesser]

This is all pleasantly overwhelming. I've been around bullet casting for more than 50 years but I just cast them and water dropped or OHT later and went on shooting and casting, mostly just air cooled for lower pressure rounds. I'm going to start paying more attention, should be fun!!!!
Thanks to all for all the recited experience and leadership!!!