What Difference Does The Quench Water Temperature Make?

[Rick]

I wasn't referencing the graph because it only represents the binary Pb/Sn, which doesn't quench-harden anyway.

That's quite true, try to quench harden a Pb/Sn alloy and you'll die a very old white haired bent over bullet caster and still not harden them. It's the Sb that enables the strengthening of the alloy if rapidly frozen in place while cooling. Other parts of the alloy such as As or Sulphur and others are grain refiners that significantly enhance the effect.
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[pokute]

I wasn't referencing the graph because it only represents the binary Pb/Sn, which doesn't quench-harden anyway.

The context of heat treated bullets is ternary alloy containing Sb and possibly As/Cu/S, which has very complex properties of precipitation-hardening due to the interaction of the various trace grain refiners often present in alloy such as WW. For a purely theoretical discussion, ternary Pb/Sb/Sn alloy has a simple phase diagram where the precipitation temperature is still below the liquidus line. The whole mess of the alloy doesn't have to be bumped above the net liquidus temperature to achieve the PH effect, it just has to be warm enough for the molecules to loosen up a bit and re-situate themselves as they cool and age.

I agree completely. I was, I thought, dealing with a discussion about the effects of quenching, and so I picked on a nice, simple binary phase diagram that could be used to discuss quenching effects.

Solid solution precipitation hardening is a whole other topic. I happen to know a little about a small number of steel and Al alloys that precipitation harden, but the physics are specific to each system. My bullet hardness needs thankfully don't require me to go beyond the Pb/Sn graph, plus a little hand-wavy stuff about Antimony and Arsenic, which I run into as contaminants.

 

[Rick]

I don't use tin (it doesn't add much hardness)

Several reasons for using Sn other than hardness though it does add a little. Sn adds right 2 BHN to my SWW & brings it up to 8 BHN.
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[pokute]

I mostly want soft, tough bullets that can deliver all their energy onto steel plates. Commercial hardcast bullets atomize on contact with the plates. Lead with just enough Tin flattens out nicely on the plates and gives them a big kick in the pants. If I want harder, I add a chunk of Linotype or a handful of hardcast bullets left over from my pre-casting days. To me, BHN12 is hard.

 

[KeithB]

Phase diagrams show the microstructure of an alloy system under equilibrium conditions. The two axes represent composition and temperature. What we need to see is an Isothermal Transformation diagram, which plots time versus temperature for materials of a specific composition. Then we could see the microstructure changes based on specific cooling rates.

 

[Ian]

Solid solution precipitation hardening is a whole other topic.

Actually....The precipitation hardening of solid alloy subsequent to heat treatment is the crux of the subject. The specific temperatures needed for different levels of final hardness vary by alloy, and final hardness is affected somewhat by coolant type/temperature. Rate of cooling from treatment temperature to room temperature also has an effect, but this all only sets the stage for the PH to take place.

 

[pokute]

Actually....The precipitation hardening of solid alloy subsequent to heat treatment is the crux of the subject. The specific temperatures needed for different levels of final hardness vary by alloy, and final hardness is affected somewhat by coolant type/temperature. Rate of cooling from treatment temperature to room temperature also has an effect, but this all only sets the stage for the PH to take place.

And with that many variables, how much progress do you think you can make sitting in the backyard with a lead pot, some wheelweights, and a bucket of water? I've got the ASTM handbooks, right here, holding up my cup of coffee, and they don't provide anything beyond general descriptive guidance. The whole topic resolves to kitchen sink experimentation, and minimal reproducibility.

The isotherms that KeithB wants require vast amounts of data. Fine if what I am after doing is manufacturing a gun frame out of 17-4PH, but way beyond what I am going to put in to cast a few hundred bullets.

 

[pokute]

I guess what I'm trying to say at this point is that starting from the Pb/Sn phase diagram, and having a pastry cooks feel for what a dash of Sb or As will do as far as providing quench hardening and/or age hardening, is about all that one can bring to the table. Effort spent learning to swage jacketed bullets would be a better investment than trying to go any further outside the laboratory.

 

[Rick]

I guess what I'm trying to say at this point is that starting from the Pb/Sn phase diagram, and having a pastry cooks feel for what a dash of Sb or As will do as far as providing quench hardening and/or age hardening, is about all that one can bring to the table. Effort spent learning to swage jacketed bullets would be a better investment than trying to go any further outside the laboratory.

yeah but some of us just gotta know, curiousity is a powerful master. It is reproducible if ya work with consistent alloys and consistent technique.
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[Ian]

It is reproducible if ya work with consistent alloys and consistent technique.

Yes. As was written earlier, it ain't rocket surgery.

Most alloy in the "clip-on wheelweight" category can be toughened to near 30 BHN maximum, heat treat to just below the slump point in a convection oven for one full hour (find the slump point the "hard" way), go straight into a bucket of cold antifreeze without passing go. In a few days it will be close to as hard as it will ever be, though it takes another week or two to settle down fully.

Water-quench from a hot mould, cutting the sprues at the instant they are solid enough to not smear but will leave a goat-arse pucker on the base, you can expect 24 bhn in a few days. Cut that alloy in half with near pure lead and you still get 18-20 bhn, but it takes about three weeks to get there. Add a bunch of tin to either and the PH process slows down while also changing the fundamental shooting characteristics of the alloy for better or worse, depending on what you intend to do with it.

If you use "pure" alloy from a foundry, you'll likely have lower numbers because of lack of trace grain refiners, principally As, but the reward is consistency from batch to batch, year to year, if repeatable exactness is of particular importance to what you're doing.

I've cast literally tons of WW alloy, from various sources through the years, often alloyed with soft-ish scrap sourced from roofers and plumbers, and found a great deal of consistency in my bullets when using any given hardening technique. I can usually count on exactly 19 BHN from .30-caliber bullets cast of 50/50 WW/soft Pb, water-quenched from a hot mould into lukewarm water, after the bullets age three weeks. Air-cooled, the same alloy ends up about 10 bhn after a month, regardless of caliber. If I add 1% tin to the air-cooled, it ends up about 11 bhn.

Part of the thrill of all this (for me, anyway) is scrounging scrap alloy and tinkering around until I can get what I want out of it. There is a little bit of pastry chef involved, but the pie recipe will turn out plenty good if it's close, and if it isn't, it usually doesn't take much head scratching to get it right.

 

[pokute]

Well, lucky or not, I have mostly Reactor Bricks of nearly pure lead, and a lot of pure Tin that a neighbor gave me(!). That, and about 400lbs of ancient ingots cast from wheelweights(?) that are a blackish color and act like they have a lot of Arsenic or Antimony in them - Whenever I use them I have to add tin until the bullets fill out again. And all I want is soft stuff for pistols.

 

[fiver]

that's where we run into trouble.
think about what most of us are working with and what the conclusions most of us have come to, on our own volition.
we may have got there different way's but it seems anyone with any time under belt and a little curiosity have come to nearly the same point.
some will just buy their alloy and run with what it gives them, but most of us are working with street lead.
which is okay if you put some care and effort into making it homogenous and repeatable.

my big batch of alloy under the bench is one mixmaster batched pile of alloy the same from the front to back and top to bottom.
it's a big pile of lead lino-type and ww's, pretty easily repeated, maybe not exactly but close enough I couldn't tell on target or with a BHN tester.

am I exactly the same as most others alloy's here...no way. [many of the ww's I use are truck weights and car weights from the 80's]
am I close enough we could swap alloy straight across and be able to make quality bullets within 30 minutes of opening the package,,,,,, for sure.



here is the bad thing.
I could see the chart there perfectly, I couldn't understand it in any way, shape, or form.

 

[Brad]

I followed some advice from Rick and learned to use heat treat temp to control BHn. I rarely use max temp for what treat, I tend to go lower so I get around 18 BHn.

I use mostly range scrap and heated to 425° F for a full hour then quenched I can reliably get 18 BHn after a few weeks.

I used to water drop out of habit but have since decided it is far easier to air cool and heat treat for consistency. I also shoot lots of stuff air cooled.

When I want a specific alloy for something different I mix up maybe 150 pounds and use it exclusively for that application. I make 50 pound lots of ingots then remelt using a set number of ingots from each of the original melts. This gives me a large amount of uniform alloy.

 

[Bill]

I was already casting when I first read this, so I plugged the pot back in and ran a little test, I dropped ten into room temp water, ten into 100 degree water, and ten into ice water, then tested the next day. The ice water 22 bhn, room temp 18 bhn, 100 degree water also 18 bhn, air cooled 11 bhn.

Bill

 

[Rick]

Re-test them in a week and again in a couple of weeks. My best guess on this is that the water dropped bullets will all reach pretty close to the same BHN but the ice water ones will get there quicker.

 

[Brad]

I would be interested to know what they test after a month.

 

[Rick]

I would be interested to know what they test after a month.

And what the alloy is??
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[waco]

I tried heat treating in my convection toaster oven for the first time a few weeks ago. My bullets were cast and air cooled a few months ago. They were right at 11-12 bhn
I put them in the oven and did my best to maintain a constant temp. I had to chase it a bit but kept it between 400-450 for one hour.

Right out of the oven and into cold water(it was 35 degrees out in my shop) I waited a week to test them. 18bhn is what I got. My small wire basket fits perfectly into a five gallon bucket.
I figure from oven to bucket was less than 2 seconds.

 

[Brad]

If water temp does make a large difference then water dropping may be the worst thing you can do. With larger handgun bullets it isn't hard to get the water too hot to touch while casting a pot of alloy. With a potential of 75-100° water temp change the hardness would change too as the session goes on.

 

[Rick]

Plus consistency from the pour to the drop into the water is difficult at best, just have one bullet hang up a bit and that drop is different than previous drops.