Annealing in molten lead

[Webster]

Not to be argumentative here since I do agree we happen to have an alignment between heat treating of alpha phase brass necks and what is called The Draper Point Temperature (the point where a human eye can see a visible dull glow).

However, that temperature is much lower than 1300 degrees F. Depending on which human technician we test, that temperature is roughly 980 F and can vary a little with different humans. If I were to blind test you in the lab, you would call the temp under 1000 F, or we wouldn't qualify you for heat treating.

What usually happens in practice, is that the heat rate of the process will overshoot that Draper Point Temp and that allows for what we would call flash heat treating in the necks for a shorter time.

One of the only reasons the type of immersion heating being discussed with molten lead or salts still exist, is for settings where the temperature over-shoot cannot be allowed. But here we are talking about hobby reloading, not industrial settings where we have to protect from over-shoot.

Now for the OP's question... I don't recommend using molten lead or salt for heat treating necks when other methods are less total fuss. Both molten lead and motel salts can heat treat brass necks to varying amounts, but it wouldn't be the method of choice when all things are considered.

There are always safety issues with an open flame and beginners should proceed with extreme caution of they don't have an experienced mentor or extensive shop/lab experience with safety. However, there are also safety issues with molten lead and salt so there are trade-offs between the issues and benefits.

If you ever put a case in a lead or salt bath that had some moisture in it there would be a large explosion with hot stuff flying everywhere. I feel very safe with my hand-held torch. You keep mentioning the Draper Point no metallurgist uses the Draper Point. All furnaces are monitored with a thermal couple to obtain real numbers and control. In some instances optical pyrometers are used.

 

[Webster]

Annealing brass is done at a faint red color or about 1300 degrees F. Molten lead at a good pouring temperature is about 850 degrees F, not near hot enough to anneal brass.

Faint red is about 1050F. Don't know how accurate but it comes from a PHD scientist I used to work with. He was a consultant to the copper industry. He reloaded 9MM. Some people think it's a little higher. Might depend on your interpretation of how bright the red is.

 

[RegionRat]

If you ever put a case in a lead or salt bath that had some moisture in it there would be a large explosion with hot stuff flying everywhere. I feel very safe with my hand-held torch. You keep mentioning the Draper Point no metallurgist uses the Draper Point. All furnaces are monitored with a thermal couple to obtain real numbers and control. In some instances optical pyrometers are used.

Places like foundries and steel mills still kill or seriously injure folks every day. I believe commercial logging and fishing is still worse, but working with molten metals and salts demands respect or it doesn't end well. I have lost many friends in those places, and nearly lost my brother and father more than once.

"You keep mentioning the Draper Point no metallurgist uses the Draper Point. All furnaces are monitored with a thermal couple to obtain real numbers and control. In some instances optical pyrometers are used."

We don't know each other, but I will give you a clue that I know hundreds of metallurgists and know a thing or two about radiometry and calibration. You can find me if you want to know why.... LOL

 

[Webster]

Places like foundries and steel mills still kill or seriously injure folks every day. I believe commercial logging and fishing is still worse, but working with molten metals and salts demands respect or it doesn't end well. I have lost many friends in those places, and nearly lost my brother and father more than once.

"You keep mentioning the Draper Point no metallurgist uses the Draper Point. All furnaces are monitored with a thermal couple to obtain real numbers and control. In some instances optical pyrometers are used."

We don't know each other, but I will give you a clue that I know hundreds of metallurgists and know a thing or two about radiometry and calibration. You can find me if you want to know why.... LOL

I guess we have different work experiences. I do enjoy reading your post and replies. Good hunting. Enjoy the summer.

 

[cavedweller60]

Annealing brass is done at a faint red color or about 1300 degrees F. Molten lead at a good pouring temperature is about 850 degrees F, not near hot enough to anneal brass.

I have to respectfully disagree. I'm certainly no expert at annealing but, I do have a decent amount of metal working experience including hardening and tempering steel...I also know how to use google. If you do a search on the annealing temp of brass, it is around 800 degrees, assuming you want it to anneal in a few seconds. You can do it at 700 but it will take a long time. The source I looked at said the actually annealing temp is 670 degrees but, as said a minute ago, it will take awhile. At 1300 degrees, you are approaching the forging temps of some steels.

 

[Straightshooter1]

I have to respectfully disagree. I'm certainly no expert at annealing but, I do have a decent amount of metal working experience including hardening and tempering steel...I also know how to use google. If you do a search on the annealing temp of brass, it is around 800 degrees, assuming you want it to anneal in a few seconds. You can do it at 700 but it will take a long time. The source I looked at said the actually annealing temp is 670 degrees but, as said a minute ago, it will take awhile. At 1300 degrees, you are approaching the forging temps of some steels.

Yes, 670°C will work just fine.

BTW: you didn't address the other important factor . . . "time" at that temperature.

 

[cavedweller60]

Yes, 670°C will work just fine.

BTW: you didn't address the other important factor . . . "time" at that temperature.

I did mention that...."You can do it at 700 but it will take a long time". I didn't state the specific time needed because I would be guessing. The other problem with using low temps and extended periods of time is heat soak. The entire case will reach the annealing temp, or close to it, if it is kept at that temp for enough time.

 

[dellet]

Pros
If you already cast, you have everything you need.

Cons
It’s complicated to do
it’s extremely inaccurate
not very repeatable results

If you already have your pot going, it’s not to bad to start. There is some brass prep that will help keep from sticking solder to case. Really the only good thing about immersion annealing is that you can pick your temperature. After that things get sketchy.

With a flame you can hold the case upright and direct the flame up and have the base in something that will act as a heat transfer, even in a socket in a drill, helping to cool the case head. Heat naturally travels up, away from the body and base. With immersion, the case is upside down with heat being dissipated out the case head.

Being able to pick a safe temperature has its problems. You really don’t want your lead over 900f so even a candle flame will produce about twice that temp cutting time in heat considerably. Add the case being upside down in even 750f lead and you will anneal at least 1/2” farther down the case than is immersed. Something keep in mind if it’s a 22 Hornet case.

To keep from sticking lead to the case, a couple things work. Outside of the case, coating it with bees wax works great. Inside the case is tougher. If you leave in the spent primer the heating air inside will push the lead out. Yes, you do need to be aware it bubbling lead and use gloves and eye protection as any time casting. Without the primer hole plugged, the escaping air will actually pull lead up into the case higher than the level of the neck inserted into the length as. Driving heat even closer to the case head. Of course the hot air trapped in the case with a primer does the same thing.

Keeping the case in the lead for the same amount of time can be done watching the second hand of a clock, holding the case the same depth is a challenge. Again a consistency problem.

Since you can be assured that you will have more case annealed than you planned, high pressure loads probably should be off the table. Case stretch/brass flow will be more than what you’re used to.

With all that said, it has its place. Bertram brass is a good example. They make a lot of oddball and obsolete brass. A lot of it sold as “basic” which more or less means unfinished. Most likely trim lengths will be off and more critically it’s not annealed properly. It sucks to pay $5+ per case and have a 30% failure due to cracks in the case body on the first or second firing. Annealing just the neck won’t help. Here’s what I do.

New brass is fitted with shot primers, sides are coated with bee’s wax, lead at 775f. Case head to 200 line painted with 350 tempilac. Very low pressure fire forming load. Haven’t lost a case to sidewall cracking since and neck only anneal after the one trip to the lead pot.

It’s not the first tool I reach for, just another onto have for the right job.