Ball Milling Titanium

[edwardw]

I made a trip to my local machine shop and they had some titanium turnings there. I bought 8 lbs for $1 / lb. I went back today and was asking for some more and they gave me about 45 lbs of their turnings because they didn't want it and just needed to get rid of it (I was the only person who had bought any in the past 6 months). Now I've got over 50 lbs of titanium and want to make some sparky motors out of it. Just to give you an idea I have 10 30 gallon trash bags full of titanium turnings. The pieces are about 1/4" wide by I don't know how long since they curl and curl and curl. Some of the stuff you can tell was finish work and more like steel wool, but the majority is thick curls.

I have a friend and he suggested I ball mill it to the sizes I want. I'm not looking at making talc but probably taking it down to the size of frosted flakes to grains of rice. He has a ball mill that has chrome and stainless steel balls that he uses.

I've looked on the internet and asked around about ball milling metal and haven't gotten too many answers. I know it's done, but can it be done with Titanium. If so are there dangers of it igniting when air hits the metal (I think it's termed 'pyrophoric') Also, can Titanium be milled to the sizes I want?

Any other methods for turning all this metal into useable additives?


Edward

 

[jwagner61]

Hi,

I think powdered titanium metal is made through reduction of the oxide in flowing hydrogen at high temperature. The oxide is a ceramic and can be easily ball milled, but malable metals cannot.

That being said, it might be possible to break the titanium turnings into small pieces by first cooling them in liquid nitrogen followed by smashing them with a hammer on an anvil. Anyone who saw the movie Terminator has an idea how this might work.

It's free advice because thats all it worth,

John

 

[edwardw]

I saw some information on the internet about ball milling aluminum and they were getting powders out. I cut a sample of turnings (20 g) up with scissors and then I put them in the good old coffee grinder. What I got out after about 2 minutes was rice sized pieces. Though the polycarbonate top was much worse for wear and I doubt it would last through 5 lbs of turnings.

Edward

 

[BlueNinja]

Maybe if you decide to use the coffee grinder route you could machine your own steel lid? I would be worried about the blades of the grinder wearing down.

 

[edwardw]

The grinder is just a temporary fix. It's not rated for continuous use. The steel lid would probably not be the best since high speed titanium pieces would spark a lot. There are already a few (once every 10 seconds or so) sparks now. And not to mention the time it would take to machine the piece and get it to fit exactly.

Edward

 

[bobkrech]

Edward

Be careful when milling the titanium in a high speed coffee mill. Although I think it's unlikely, it might be possible to lite off the titanium with a spark in the milling process, and once it starts burning, you can't put it out. It's the only metal that burns with nitrogen as well as oxygen. (The gold coating on high grade cutting tools is titanium nitride.)

A ball mill looks like the way to go if you want to try reducing it yourself. You should try it out in your friends mill, but if you're not successful with his chrome/stainless balls, you might want to try ceramic.

Titanium has a pretty good scrap value. You might just want to see what it's worth. Skyliters prices range from $15 to $20 per pound for Ti flake, and for what I can find for scrap prices, Ti scrap sells for $1.50 a pound. If you have 50 pounds and a local scrap dealer that acdepts it, you might be able to get enough for it to buy a few pound of the new stuff.

Bob Krech

 

[aksarben10]

Lloyd Sponenburgh wrote the manual on these things. Search on his name and you will find many references from people who have followed his book and made mills. They can be made in just about any size and he covers the safety issues as well. Anytime you get small partical sizes of any material they can get explosive, static is a concern.

For milling metals you need heavy media, heavier the better ceramic balls are too light for a tough metal. Even with softer products lighter media will take more time.

To keep the product from reacting to new air, some people stop the mill from time to time and open them to recycle the air, it allows the product to oxidize over time instead of all at once.




Skylighter carries the book.


Ball Milling Theory and Practice for the Amateur Pyrotechnician

By Lloyd Sponenburgh

If you want to learn how to grind your own materials faster and efficiently, or to simply make better black powder, this book’s for you. This 66 page manual contains plans, bills of materials, tool lists, and clear, step-by-step instructions for building a durable and high quality ball mill. Also included are sections on grinding media and casting your own lead media. 7 illustrations, 6 photographs.


Scott

 

[bjmcder]

Titanium has a tendancy to spark when struck, and you risk a metal fire with all the esposed surface area present with turnings or powders. You may need to purge your mill with argon or a similar inert gas (but not nitrogen!) to prevent this.

Whe using titanium, it should be like medium-coarse sand in consistancy (20-60 mesh). Too fine and the spark effect is lost, too coarse and you will get severe nozzle erosion, or even a CATO.

 

[r1dermon]

i like the liquid nitrogen idea. most compressed gas companies have liquid nitrogen, and its not that expensive, as long as you have a dewar flask to carry it in. use it in a well ventalated area to decrease the risk of asphyxiation, but, i've seen rubber smash into pieces after it spent 1 minute in a liquid nitrogen bath...so if you could get a bunch of shavings into the liquid nitrogen, and THEN transfer them to the ball mill and turn it on, you should get some decent flakes out of that. how thick are the shavings?

 

[edwardw]

Bob, I've been aware of the sparking and the fire hazard. The coffee grinder will only handle about 10 grams at a time. I took about 10 grams and started it burning on a piece of concrete in the backyard and I thought the sun was rising right there. My wife was in the house and saw the brilliant light on the wall and thought I was burning the house down. Her quote was "It was brighter than daylight." I found it very interesting that it's the only element that will burn in nitrogen, kind of like magnesium will burn in carbon dioxide. I appreciate the advice.

I think I'm going to try and ball mill some of the pieces with the stainless steel balls. If it doesn't work then I'll find something else.

Here is a picture of the 4 type of turnings that I have.

Right to Left: Looks like a parting operation then a turning operation. The fishy shaped one I'm pretty sure is a drilling operation followed by some finishing swarf.

Edward

 

[edwardw]

Here is what some of it looks like after it's gone through the coffee grinder. Imagine grinding aluminum foil. It will break down, but it dents and dings and tears first.


Edward

 

[r1dermon]

ever seen magnesium ribbon burning? quite bright.

 

[edwardw]

Actually I have a big piece of magnesium. It is 1" thick, 6" wide and 5 feet long. Scrap from a metal dealer when I asked if they had any. I got it for $10. I then was very careful and cut about a 1/2 strip off of it. Took the torch and heated the end until it caught fire. Very very bright and burned for a long long time. Still amazes me that metals can burn.

Edward

 

[r1dermon]

OMG, you're so lucky....magnesium is a great igniter. but, the ribbon is a little pricey. also, if its thin enough it will shoot around. light it on the ground and it will take off, as long as its light enough. i havent had any for a while. but i never knew scrap yards had that stuff. man. looks like i've got tomorrow planned. lol.

 

[Ray Dunakin]

Originally posted by r1dermon
i like the liquid nitrogen idea. most compressed gas companies have liquid nitrogen, and its not that expensive, as long as you have a dewar flask to carry it in. use it in a well ventalated area to decrease the risk of asphyxiation, but, i've seen rubber smash into pieces after it spent 1 minute in a liquid nitrogen bath...so if you could get a bunch of shavings into the liquid nitrogen, and THEN transfer them to the ball mill and turn it on, you should get some decent flakes out of that. how thick are the shavings?

Liquid nitrogen would probably be a bad idea, since titanium burns in nitrogen.

 

[r1dermon]

qute an interesting point....scrap that liquid nitrogen idea...lol

 

[BlueNinja]

What about, if you could obtain it, liquid CO2? It isn't all that cold, and I'm not sure if titanium will burn in it? A bath of CO2 for 5 minutes or so would chill it nicely.

Also, I don't see how liquid nitrogen would be a problem if you use it. It supports Ti burning, but I don't think it would be any more of a fire hazard than ball milling it in plain air.

 

[r1dermon]

im not sure liquid CO2 is cryogenic like LOX or liquid nitrogen...you could probably dunk it in LOx, however, i wouldnt mess with liquid oxygen in ANY quantity.

 

[daveyfire]

Originally posted by Blue_Ninja_150
What about, if you could obtain it, liquid CO2? It isn't all that cold, and I'm not sure if titanium will burn in it? A bath of CO2 for 5 minutes or so would chill it nicely.

Unfortunately, Liquid CO₂ is only available at higher pressures. That's why "Dry Ice" is dry -- the solid CO₂ sublimates into the gaseous phase at atmospheric pressure.

https://www.chem.uncc.edu/faculty/murphy/1252/Chapter11B/img004.JPG is a phase diagram showing the phases of CO₂ and the points at which they can occur. Anywhere in the blue zone (past the triple point) will give you liquid CO₂... 5.11 to 73 atmospheres and above -56.4 degrees C. Too much work for me

Good luck Edward, looking forward to seeing some sparky sugar motors!

 

[BlueNinja]

Yes, Davey is right. I had a brain fart. For some reason I thought liquid CO2 was obtained by temperature.

 

[bobkrech]

We have a cryogenic mill for powdering and alloying metals that are not stable at room temperature. Unfortunately they are not cheap, but they esist.

Liquid nitrogen or liquid argon are available at local welding gas supply houses. The cost is relatively cheap. We buy a lot of gas and have scheduled deliveries twice a week. I believe we pay about $55 for a 240 liter dewar of liquid nitrogen with a $30 per month rental charge. That about 3 liters for a $1. A small time user would pay about twice this price, however I think by the time you add up the costs to actually reduce the titanium turnings into the proper size, you have spent more money than it's worth if you go this route.

Bob Krech

 

[edwardw]

Also - any idea of cooling the metal down probably won't work. The metal is thin -thin enough to be cut with regular scissors- so it will cool down, then heat up relatively fast. As Bob said it's going to be far more expensive trying to cool it down. I'm going to just mill them and see what happens. So far - about 24 hours worth of milling and I'm getting good results.

Edward

 

[r1dermon]

nice....you have any way to screen it and accurately record mesh size?

 

[Tools R Us]

TI turnings work OK in sugar motors, in AP motors they are mostly burned in the motor with very little sparky effect. The chunks need to be good sized for good effect, at 10-15% the mix very thick. We had good luck putting them in a kitchen blender mixed with water to chop them.

The coolant used in the machine shop makes a great nonstick surface, they don't stick to the propellant making it hard to mix them in. To remove the coolant wash with Acetone or the easy way is to spread it about a 1/4" deep in an electric frying pan and burn it off outside at about 400F for 30 min.

 

[Tools R Us]

A 75mm 5 grain L sparky sugar motor;

https://www.trailertrashaerospace.com/images/2-29-2004_chubsy_sparks.jpg

 

[edwardw]

I'll have to try that kitchen blender idea. I will go to ARC and get one, the wife wouldn't be so happy if I messed her's up. The turnins I have don't have any cutting fluid on them or have been washed because they are very clean. I'll let you know the results. Right now the sugar sparky is on the back burner and a hybrid is on the front.


Edward

 

[sean79]

FWIW, the Ti I used to use for sparkies was from Skylighter. I used a 50/50 mix of the 10-20 mesh and 18-36 mesh sponge. Sponge really isn't that hard on nozzles. Add 10% or so of your total Ti mix of lathe turnings such as what you have and it will really crack and pop. I did a 2000 N/sec K motor that set off a car alarm once.

I also managed to jam up a K motor nozzle with 5% lathe turnings. I've gone as high as 15% sponge and it comes out fine.