That will give the max time to keep from hurting the rest of the brass. I’m figuring the neck is 1000F in 5 seconds and still will be a 1000F when done longer. I guess the question is....if brass is annealed to 1000F, is it overdone? In my opinion using a touch on the brass OD and watching for 750F at the neck ID, the torch method is bring brass at the ID to temperatures much more than 750F.
Proper temperature for salt water annealing....
- Thread starter done111
- Start date
That will give the max time to keep from hurting the rest of the brass. I’m figuring the neck is 1000F in 5 seconds and still will be a 1000F when done longer. I guess the question is....if brass is annealed to 1000F, is it overdone? In my opinion using a touch on the brass OD and watching for 750F at the neck ID, the torch method is bring brass at the ID to temperatures much more than 750F.
Yep, kinda hard to overheat the brass if your heat source is a known quantity. I left a piece of 308 brass in the salt bath for over 3 minutes at 1000 F to see what it would take to soften the case down to the head. Wasn't able to soften it more than half way down, by my crude (squeeze with pliers) way of measuring.
Do you think the neck portion was over-annealed at 3 minutes? I can see parts of the casing being ruined, I'm just talking about the necks.
For the same reasons you can last longer standing in 40°F air than submerged in 40°F water, or hold your hand in 200°F air, vs dipping your hand in 200°F water..
conduction/ heat transfer.
As hot as it is, a flame is merely gaseous, whereas the salt bath is liquid. Liquids, at least water, transfer heat approx 25x faster than air.
Here's something I've read about but never bothered trying:
Try this(AT YOUR RISK): Blow up a balloon and hold a match to it. It will explode instantly because the air inside the balloon can't move the heat away from the surface of the balloon very quickly.
Now take another balloon and fill it with water. Hold a flame to it. The balloon won't explode because the water is very good at carrying the heat away from the surface of the balloon.
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Plugging in a melting pot & dipping any cases as deep as you like, and at any duration -for perfect process anneal, is too complicated?
This is about the 5th time I am putting this graph on the website. I cut the necks off of once fired Lapua 6BR cases. The necks were attached to a fine Nichrome wire and lowered into a small accurate laboratory furnace thru a small hole in the top of the furnace. Temperature control was +/- 2 degress F. Lowering the samples thru the hole allowed putting them in the furnace without opening the door which would cause a large temp drop. I chose 15 seconds for the shortest time since I didn't know how long it took to reach temp. It shows the trend. 5 seconds would obviously show less hardness drop. The annealed brass was cross sectioned put in epoxy and polished. Microhardness was done on each piece. The results were converted from vickers hardness to Rockwell B scale using an ASTM conversion table. The most obvious thing is 15 seconds at 900F there is very little drop in hardness.
No dumb comments that it isn't the entire case. Put your thinking cap on.
Just looking at the blue line which represents a cartridge neck of brass at 10 different temperatures each held for 15 seconds. Each data point on the graph plot represents the results of one sample in the furnace. Temperature on the bottom axis, hardness on the left axis.
No annealing = a hardness of 81 HRB units
900F for 15 seconds = 80 HRB
1000F for 15 seconds = 79 HRB
For all practical purposes no change in hardness. Must have good stress relief which I don't think can be measured by hardness? Most metallurgical labs don't get involved with stress. People may dispute these numbers but that's what I got doing everything as accurate as possible.
Micro hardness is done with a small diamond indenter, a weight is applied to the indenter, the softer the brass the bigger the indent. The indent is then measured using a microscope > the length measurements are converted to hardness scales using ASTM tables. It's required to make at least three indents and average them.
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Webster, very interesting chart/experiment. Great food for thought. Did you measure the hardness of virgin brass at the neck for comparison (is that what we are trying to get to without going lower?)? Also I'm wondering what were the conditions of your furnace heating besides the temperature? I'm curious of how well it "soaked" the brass. Was there some sort of circulating air in there? I imagine the brass will soak the heat faster in a salt bath than with still hot air around it. Your 5 minute plot would definitely be heat soaked and appears to be dropping fast starting at around 750F.
Do you think the work hardening from one firing as compared to virgin brass is a large difference? Could it be possible that if the brass saw multiple firings (more severe work hardening) that the plot would have started higher and sloped faster and arrived to a similar location around 1000F on the 15 second curve?
Don
Do you think the work hardening from one firing as compared to virgin brass is a large difference? Could it be possible that if the brass saw multiple firings (more severe work hardening) that the plot would have started higher and sloped faster and arrived to a similar location around 1000F on the 15 second curve?
Don
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That seems like good info but I too must question the applicability in our practices as that seems like very mild temps and long dwell times comparatively.
A torch will be way hotter than those temps in the flame. Conduction from contact in the bath will be way faster than convection from relatively cool air. Induction would be a more direct application still.
15 seconds in an oven at 900 may only get the case up to 500 degrees.Turn the furnace up to 2500 degrees and see the results.
A torch will be way hotter than those temps in the flame. Conduction from contact in the bath will be way faster than convection from relatively cool air. Induction would be a more direct application still.
15 seconds in an oven at 900 may only get the case up to 500 degrees.Turn the furnace up to 2500 degrees and see the results.
Not sure what you mean by mild temps.
Don’t have a good answer to your question and done111. I have put thermocouples on small samples and put them in small furnaces many times at work. The small samples get to temp in a few seconds especially copper. Keep in mind that the cartridge factories also anneal with a flame for a few seconds. Not sure if they still use a flame. Frankfort Arsenal used a flame 20 years ago. My furnaces did not have a fan. They were considered accurate enough to determine when incipient melting started in aluminum castings for the aerospace industry and they were certified by an inspector from the aircraft industry. I anneal for 5 sec with a torch and just accept whatever is happening.
In 5 sec it is still possible to get the very tip of the neck red, depends on how you apply the flame. I assume that’s because the flame touches the end of the neck and there is less copper to spread the heat. I noticed that sometimes the first 10-15 thou of the neck end is red and the rest of the neck is cooler. It’s impossible for enough heat to travel down the body to cause any damage in 5 sec. 750F is the very bottom of the annealing temp range and if you heat with a torch for 5 sec the neck is only in the annealing temp range for 1 or 2 tenth of a second. You have to be careful what part of the flame touches the case. There is a huge difference in temp though out the flame. The blue pencil point tip is the hottest. You need to verify you are not overheating in a dark room.
Again I think you just have to get a method that doesn’t overheat and just accept the results.
dcali
Bullet Maker
You're just factually incorrect here. That's not how alloy melting points work.
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dcali
Bullet Maker
I think it's reasonable to think that the time to temp may be delayed in an oven when discussing such short annealing times. You basically have a ramped temperature, which is going to draw out the time a little. So Webster's chart probably overstates the actual required temperatures/times relative to faster heating sources. By how much, I can't say. I've looked (a lot) for data on small sections of brass for annealing data and it's really hard to find. Almost all the engineering literature out there is on larger sections and 1 hour+ heat times. What little I have found was not precise enough (or short enough) for our needs. This is understandable given the difficulty in performing experiments like that.
The best way seems to be to do before and after hardness testing using the method in question. That way, it doesn't really matter what the brass temperatures are as long as you do it the same way every time and are happy with the resulting hardness. Unfortunately, not many have access to the required equipment.
The best way seems to be to do before and after hardness testing using the method in question. That way, it doesn't really matter what the brass temperatures are as long as you do it the same way every time and are happy with the resulting hardness. Unfortunately, not many have access to the required equipment.
1000s of people are probably annealing. None of them can determine the hardness. How would you determine a proper hardness anyhow. Several creditable people couldn't find a difference in accuracy annealed and no anneal. Quit making it complicated. Just anneal for a few seconds and you have stress relieved and probably had a tiny drop in hardness. Just do it the same way each time and don't get red in a dark room. How many years are people going to discuss this before they settle on a method? Hall of fame short range BR shooters don't anneal.
I mean a 1000 degree furnace is only 40% of a butane flame which is ~2500 degrees. Sure 15 seconds at 1300 degrees the brass hardness starts dropping appreciably but how much faster will the hardness start to drop at 2500 degrees? I would venture a guess that its going to be the 5-6 seconds that most flame annealers seem to use. In 3 seconds my annie will have a 3006 neck glowing(!) red. I used your 15 second benchmark with induction the neck would have melted off the case instead of finally just becoming soft.
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dcali
Bullet Maker
Your "tiny drop in hardness", which I presume is based on that chart, is incorrect because your chart is overstating the time required to get a drop because of the way the brass was heated (convection). An AMP doesn't anneal for anywhere near the time that you say is required, and they have measured the resulting hardness. It's a big drop, and it happens in a couple seconds of heating.
And yes, people have been doing it without knowing what they're getting for ages. I don't bother at all. But if I'm going to do something, I'd prefer to understand it and do it right if at all possible. Saves a lot of wasted time and effort.
Do any of you use the salt bath method and have 450* tempilaq . I'd love to know if the bath is at 750* how long it takes for the case to reach 450* half way between the head and shoulder ? or half way between head and the spot the salt bath no longer makes contact with the case ?
The reason that I want to know this is . If the salt bath method really does heat firearm brass very fast . Why is the salt bath recommended to have a temperature of almost 1000* . My theory here is if the heat does not transfer quickly towards the case head . Why not have the bath set to the actual temperature you want , resulting in every case being heated to the exact same temperature . Rather then at a 1000* and 3sec you get 650* , 4sec you get 750* , 6sec you get 900* . If the case does not transfer to heat to the head fast . Why not have the bath at 750* and at 4sec you get 750* , 5sec you get 750* etc leaving you with consistently annealed brass with a much larger window to work with ????
The reason that I want to know this is . If the salt bath method really does heat firearm brass very fast . Why is the salt bath recommended to have a temperature of almost 1000* . My theory here is if the heat does not transfer quickly towards the case head . Why not have the bath set to the actual temperature you want , resulting in every case being heated to the exact same temperature . Rather then at a 1000* and 3sec you get 650* , 4sec you get 750* , 6sec you get 900* . If the case does not transfer to heat to the head fast . Why not have the bath at 750* and at 4sec you get 750* , 5sec you get 750* etc leaving you with consistently annealed brass with a much larger window to work with ????
That tempilaq test would be an interesting test for nothing other than to calm fears about heat migration. I thought I read somewhere that it had been done but it could just be that the gentlemen on the 6.5 forum could still handle them barehanded so the heat wasnt migrating that far up the case body.
Why anyone would want to make the process slower though I dont understand. We are wanting to limit the time spent doing chores and heat flow in the the case body. Lowering the temp of the brass only drags those things out longer and aggravates the issues.
Why anyone would want to make the process slower though I dont understand. We are wanting to limit the time spent doing chores and heat flow in the the case body. Lowering the temp of the brass only drags those things out longer and aggravates the issues.
Your making a lot of assumptions. I have had enough of this babble.
Well since we're getting testy...None of the assumptions are as large as the one you are making in that assuming 15 seconds is a proper annealing time and 1300 degrees is a proper annealing temperature. Neither of those things are applicable to what we reloaders practice.
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