machining titanium

[dpuch]

Please! read your material data sheets.

While fire may not be likely in most normal situations, it IS a possability. Be prepared.

III. FIRE & EXPLOSION HAZARD DATA FLASH POINT (F): N/A FLAMMABILITYLIMITS (%/VOL): LEL: N/A METHOD USED: N/A UEL: N/A AUTO-IGNITION TEMPERATURE (F): 2200F for metal in air, 480F for powder in air. EXTINGUISHING MEDIA: Dry table salt or Type D fire extinguisher. SPECIAL FIRE-FIGHTING INSTRUCTIONS: Remove uninvolved material; allow fire to burn out. Fire can be controlled by covering with dry salt or powder from Type D fire extinguisher. Carbon dioxide is not effective. UNUSUAL FIRE AND EXPLOSION HAZARDS: Dry titanium burns slowly while releasing much heat. Water applied to burning titanium may cause an explosion. Piled chips may burn vigorously.

Powder isn't that likely from milling, but that temp isn't that high either.


For milling, try some of these links with suggested speeds and feeds, as well as milling practices.

http://www.mmsonline.com/articles/010402.html
http://www.niagaracutter.com/solidca...speedfeed.html
http://findarticles.com/p/articles/m...6/ai_112862178
http://www.timet.com/fab-p17.htm

[davereagan]

I once ran my facemill inserts so dull on some Titanium 6-4 alloy that I shut the lights off and could see fire coming off the cutter. No flames. vYou guys have tihs confused with magnesium which can burn down a machine if it gets going.

Dave

[Pressfit]

Yes indeed Ti will also burn and cause a fire in and around a machine. I saw it personally happen with another Machinist over 25 years ago on a 50 inch King VTL. The part was a jet-engine exhaust duct about 4 feet in diameter which he was spinning around 20 or 30 rpm and cutting dry. WAY, WAY too much sfm and the chips came off red and fell down into the chip pan which probably had some residual oil or other matter in it.

Next thing you know there was smoke billowing around the machine and we had to evacuate the shop so the company fire department could put it out. After we were allowed to go back to work the machine was scorched with black soot and the entire wiring system was burnt out. The company had to send the machine out for a re-build.

Whenever we had to grind Ti, the grinder had to be completely cleaned of any dust and completely de-greased and wiped down. Then inspected and okayed by the fire department before starting.


Note the heading (Precautions) towards the bottom of the page....
http://en.wikipedia.org/wiki/Titanium

[davereagan]

Good info. I still think the above posters had it confused with magnesium. It sounds like the oil burned after the white hot titanium ignited it. Maybe they burned together.

[mxtras]

No - I am not confused. I have lit up a chip tray on a lathe. I was turning an ultrasonic grade of Titanium and that particular alloy will burn, I assure you. It will not actually flame - it burns the way steel wool burns except it is white hot and extremely bright. It's hot enough to catch adjacent combustibles on fire, and that is the hazard.

I was off on the type used to extinguish - it is type D, not K as I mentioned in post #7. Sorry. I guess I had fried chicken on my mind!

Scott

[davereagan]

OK, you win. Magnesium is still far more flammable, agreed? That's what they make fireworks from. I've seen carcass CNC machines for sale. Iron still there, wiring all burned out. Magnesium is always the culprit. Water seems to make it worse.

[Gumby]

The fire aboard the USS Enterprise in ’69 was compounded by the burning aircraft that was struck with a zuni rocket and eventually lead to the detonation of several large (500lb) ordnance on that aircraft after a failed attempt to extinguish the fire was made by a single Chief who was equipped with the wrong type of extinguisher. Those aircraft frames are made out of titanium and pose a significant fire fighting problem when you are not equipped with the proper tools.

Titanium can burn from normal machining operations if care is not taken to limit feed rates and cool the work piece.

This article outlines the difficulty in machining titanium alloys.

Just an FYI you can use graphite powder in place of a Type-D extinguisher if you can not afford the extinguisher. If you have to use water to combat a class D fire make sure you do not direct a solid beam of water at the fire as this will most likely result in a steam explosion. You can however use a mist spray to fight the fire with little risk of an explosion.

I hope this helps,
~Gumby