oven heat treat!!!!!!!!

[indymadcaster]

well i did a big batch today of clip on WW put the gas checks on and convectioned oven baked my 762 44 45 boolits for an hour @ 460degrees and then quenched in 45 degree water i wonder how hard they are?

[madsenshooter]

Not as hard as they're going to get. Give em a little time before testing, in 4 days they should be up around 25.

[outdoorfan]

If the antimony content was close to 4%, then I would guess pretty close to 30 bhn. And it should pretty much be there in 24-48 hours.

[Shiloh]

Don't know what the Brinell hardness is, but it harder than I need. From what I read about it, 25-30 or more is possible. What are you using them for? Long distance so you can run at higher velocities??

Shiloh

[indymadcaster]

yes it is for sks and my 308 handi its a lee C312-155-2R OMG they are TOUGH
i can barely make marks in them with pliers in 762x39 i am thinking h335 or lil gun maybe bench mark in 308 i am thinking of 34 grains of surplus 4895
:castmine:

[Blammer]

better size then NOW. :)

[sqlbullet]

Last winter my son, then 10, did a science fair project on this very subject. I handled all the lead for him, and helped him design the experiment. He kept the logs, did the research, made the conclusions, and created the display.

We cast 18 series of 30 bullets, using a Lee six cavity 175 gr .401 TL mold. The lead alloy was 96% lead, 3% antimony, 1% tin. 6 series each cast to a hot mold from a lead pot at 650°, 700° and 750°.

Half of the series at each casting temp were water quenched. Certain series received subsequent oven treatments at 350° and 450°.

This gave us the following variations at each casting temperature:

air-cooled
air-cooled, oven treat (350°)
air-cooled, oven treat (450°)
quenched
quenched, oven treat (350°)
quenched, oven treat (450°)

10 samples were analyzed from each series for weight and hardness. The weight was on a cheap frankford arsenel digital scale, and the hardness was using a Lee hardness tester. The indent size was estimated by three parties, and all estimates were included in the subsequent averages. Hardness was measured 48 hours after treatments.

The highest average BHN came from the bullets quenched with no subsequent heat treatment in an oven. I know this flies in the face of the prevailing wisdom I have read hear, but I feel the data sample is large enough that I am satisfied. The samples cast at 750° and quenched averaged a BHN of 32.41, while the oven treated (450°) bullets from the same casting temp averaged 25.33. Quenched bullets that were subsequently heat treated averaged 1 bhn harder than air-cooled bullets that subsequently received the same heat treatment.

There are two big advantages to oven treating. First, it can be applied after sizing, reducing stress on equipment. Second, the standard deviation in the hardness of the oven treated bullets was much lower. While they don't get quite as hard on average, they are more uniform in their peak hardness.

The chart of the results can be viewed here (http://www.fellingfamily.net/isolead/).

[outdoorfan]

Had you HT'ed those boolits at around 480 degrees, my guess is they would've been harder. The other thing is the amount of time elapsed between the oven and the quench can effect final hardness. From the time I open the oven to the boolits being under water is not much over one second.

[Doc Highwall]

I took a look at the chart and found that you heat treated the boolits for one hour at these temperatures. I would have tried the 450deg again for 2 hours and tested again. Looking at the chart again I did not see antimony mentioned, you need it to harden the lead at least 4%.

[outdoorfan]

I took a look at the chart and found that you heat treated the boolits for one hour at these temperatures. I would have tried the 450deg again for 2 hours and tested again. Looking at the chart again I did not see antimony mentioned, you need it to harden the lead at least 4%.


If he got 30+ bhn with 3% antimony, then he doesn't "need" more antimony. I don't think there's a difference between 1 & 2 hours in the oven. Have you seen a difference?

[Doc Highwall]

outdoorfan, when I look at his chart his heat treated boolits are softer then his water quench boolits. I also went back to his post and saw that he had 3% antimony content that I did not see when I read the attachment, my fault. I believe that one hour is the minimum time with over two hours not adding anything and his high temperature of 450 deg as slightly low preferring closer to 475 to 485. Some times with a lot of heavy boolits in the oven it takes a little longer to stabilize the temperature and you also need room around the boolits for the water to cool them evenly. It has been a long time since I have done any heat treating but I will be doing it again some this summer.

[mroliver77]

To get the most out of oven heat treating the lead must be brought as close to slump temperature as possible. The last few degrees make a big difference. Preheat your oven having first made some sort of baffle to keep direct heat from the elements from the lead. I use a heat sink too in the form of a ceramic pizza tray.Then load a couple scrap boolits from the same batch into oven. After giving time for boolit to saok up heat, gradually increase temp a few degrees at a time until you get a boolit to slump. Back off 10 degrees and try again. If this does not destroy boolit you are ready to do a batch. Remember that different alloys melt art diferent temps and you can ruin a batch by disregarding . Now you can use 450 deg. but will not get the max effect. You can sneak up on the temp and get more hardening but remember that oven dials are crude and do not reflect true oven temp. Best to get a good thermometer or take the time and do the slump test. I have satisfactory results with 2% antimony but get 20ish brinnel. According to articles on subject you get the most hardening effect with 4%. YMMV
Jay